ENERGY NETWORK

RESEAU D'ENERGIE

English Abstract

An energy network is provided. An embodiment includes a network having a
plurality of power stations and a plurality of loads interconnected by an
electricity grid. The loads include electrolysers. The network also includes a
controller that is connected to both the stations and the loads. The
controller is operable to vary the available power from the power stations
and/or adjust the demand from the electrolysers to provide a desired match of
availability with demand and produce hydrogen as a transportation fuel with
specific verifiable emission characteristics.

French Abstract

L'invention concerne un réseau d'énergie. L'un des modes de réalisation comprend un réseau possédant plusieurs centrales énergétiques et plusieurs charges reliées entre elles par un réseau d'interconnexion. Les charges comprennent des électrolyseurs. Le réseau comprend également un dispositif de commande qui est connecté à la fois aux centrales et aux charges. Le dispositif de commande peut être actionné de manière à faire varier la puissance disponible des centrales énergétiques et/ou de manière à régler la demande des électrolyseurs afin de fournir une disponibilité correspondante souhaitée avec la demande et de produire de l'hydrogène en tant que carburant de transport présentant des caractéristiques d'émission spécifiques vérifiables.

Claims

Claims:
1. An energy network comprising:
a plurality of electricity generating stations;
a plurality of variable power loads connected to said generating
stations by a grid; ,
a controller for receiving and processing data concerning availability of
electricity from said plurality of electricity generating stations and
concerning demand for electricity from said plurality of variable power
loads;
said controller being operable to send instructions to one or more of
said plurality of variable power loads to adjust demand from said
variable power loads to approach a match of said demand with an
availability of power from said generating stations; and
transmission means for transmitting information including data and
instructions between said controller and said plurality of electricity
generating stations and said plurality of variable power loads.
2. The network of claim 1 further comprising at least one generating
station having a variable availability such that said controller is operable
to
send instructions to said at least one generating station having variable
power
to adjust availability from said generating station to match said demand.
3. The network of claim 2 further comprising a data network connected to
said controller, said network providing additional information about said
demand and said availability to said controller and which is used by said
controller to determine whether to adjust at least one of said demand and said
availability to approach a match there between.
4. The network of claim 3 wherein said match is based at least in part on
determining which of a plurality of adjustments produces a reduced amount of
harmful emissions in comparison to another adjustment.
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5. The network of claim 3 wherein said match is based at least in part on
determining which of a plurality of adjustments has a least amount of
financial
cost in the marginal cost required to produce electricity.
6. The network of claim 3 wherein said variable power loads include at
least one water electrolyser for converting electricity into hydrogen.
7. The network of claim 6 wherein said electrolyser has a known schedule
of production.
8. A controller for an energy network having a plurality of electrical
generating stations and a plurality of power loads connected to said
generating stations by a grid, said controller having a plurality of
programming
instructions operable to (i) receive and process data concerning availability
of
electricity from the plurality of electrical generating stations, (ii) receive
and
process data concerning demand for electricity from the plurality of power
loads, and (iii) adjust demand from said power loads to match said demand
with an availability of power from said generating stations.
9. The controller of claim 8 wherein said network further includes at least
one generating station having a variable availability such that said
controller is
operable to adjust availability from said generating station to match said
demand.
10. The controller of claim 9 wherein said network further includes a data
network connected to said controller, said network providing additional
information about said demand and said availability to said controller and
which is used by said controller to determine whether to adjust at least one
of
said demand and said availability to approach a match there between.
11. The controller of claim 9 wherein said match is based at least in part on
determining which of a plurality of adjustments produces a reduced amount of
harmful emissions in comparison to another adjustment.
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12. The controller of claim 9 wherein said match is based at least in part on
determining which of a plurality of adjustments has a least amount of
financial
cost in the marginal cost required to produce electricity.
13. The controller of claim 9 wherein said variable power loads include at
least one electrolyser for converting electricity into hydrogen.
14. The controller of claim 13 wherein said electrolyser has a known
schedule of production.
15. A method of controlling an energy network comprising the steps of:
receiving demand information representing an amount of electricity in
demand by at least one electrical load, said at least one electrical load
including an electrolyser for converting electricity into hydrogen;
receiving availability information representing an amount of electricity
available from at least one electrical generating station; and,
adjusting operation of said at least one electrical load and said at least
one electrical generating station such that said demand information
and said availability information approach a match there between.
16. The method of claim 15 wherein said adjusting step comprises the
steps of:
determining if said demand exceeds said availability, in which case
performing the steps of:
(i) increasing availability if additional availability is available;
(ii) decreasing said demand if said additional availability is not
available;
determining if said availability exceeds said demand, in which case
performing the steps of:
(i) increasing demand if additional demand is available;
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(ii) decreasing availability if additional demand is not available.
17. The method of claim 15 wherein said availability information includes a
cost associated with producing electricity and said adjusting step includes a
determination of a desired cost optimization based on said cost and a
decision whether to adjust availability or demand based on said cost
optimization.
18. The method of claim 17 wherein said cost is determined based on a
marginal cost of electricity to produce hydrogen.
19. The method of claim 17 wherein said cost is determined based on an
emission cost associated with producing electricity.
20. The method of claim 17 wherein said cost is determined based on an
emission cost associated with the application using hydrogen produced by
said electrolyser.
21. The method of claim 20 wherein said application is a hydrogen
powered vehicle and said emission cost is determined based on at least one
of a) associating an emission cost associated with a non-hydrogen vehicle
with an emission profile generated by a power station producing electricity
for
said electrolyser and b) comparing said emission cost with forms of hydrogen
generation other than said electrolyser.
22. The method of claim 15 wherein said at least one electrical load
additionally includes a set of conventional loads.
23. The method of claim 15 wherein said at least one generating station
includes a first power station having an availability profile that is
substantially
fixed and a second power station having an availability profile that is
substantially random.
24. The method of claim 23 wherein when electricity from said second
power station is available and if said availability exceeds said demand then
at
said adjusting operation step said demand from said electrolyser is increased.
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25. The method of claim 23 wherein when electricity from said second
power station is unavailable and if said demand exceeds said availability then
at said adjusting operation step said demand from said electrolyser is
decreased.
26. The method of claim 23 wherein said first power station is a nuclear
power station and said second power station is a wind farm.
27. The method of claim 15 wherein said electrical load includes a plurality
("K") of electrolysers and said demand is based at least in part on the
following:
TotalElectricPowerDemandOfElectrolysers(t) =
<IMG> (RateOfFuelProductionk (t) x
SpecificEnergyConsumptionForHydrogenProductionAtStationk (t))
wherein
<IMG> RateOfFuelProductionk (t) = TotalRateOfHydrogenProduction(t)
where K = number of electrolysers; and
t = time.
which is in balance with electricity supplied by captive electrical generating
stations, J in number, and available electricity from a grid:
TotalElectricPowerDemandOfElectrolysers(t)=
<IMG> PowerForElectrolysisFromCaptivePowerSource, (t) +
PowerForElectrolysisFromGrid(t)
where J = number of captive generators; and
t = time.
such that over a predefined period the following requirements are met, acting
as constraints to RateOfFuelProduction and the optimization process:
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FuelAvailablelnStation k (t+ .ANG.t) = Fuellnventory k (t) +
(RateOfFuelProduction k (t) -
RateOfFuelConsumption k (t)) x .ANG.t
.gtoreq. CustomerDemandForFuelAtStation k (t + .ANG.t,
FuelSellingPrice)
.ltoreq. MaximumStorageCapacityOfStation k
where t = time.
28. The method of claim 15 wherein said demand information is based at
least in part on a measured amount of stored hydrogen fuel available at said
electrolyser.
29. The method of claim 28 wherein said measured amount is based on at
least one of: a) pressure, temperature, volume in compressed storage tanks
and b) pressure, temperature, volume, mass of metal hydride in metal hydride
hydrogen gas storage.
30. The method of claim 15 wherein said availability information includes
information concerning at least one of: a type of emission created by each
electrical generating station, a type of fuel used by each electrical
generating
station, an efficiency rating for each electrical generating station, and a
response time for deactivating or activating each electrical generating
station.
31. The method of claim 15 wherein said availability information includes
one or more types and quantities of emission produced per unit of electricity
produced for each electrical generating station.
32. The method of claim 31 wherein said electrical generating station burns
hydrocarbons and said types and quantities of emissions includes a
measurement in mass of emitted CO2, NO, CO per kWh of electricity
produced by said electrical generating station.
33. The method of claim 32 wherein said demand information includes an
emission penalty associated with that load and said adjusting step is made at
least in part by adjusting availability at one of said electrical generating
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stations having a reduced amount of pollutants produced per kWh in relation
to another one of said electrical generating stations.
34. The method of claim 15 wherein said demand information includes at
least one of a type for each load, and whether an emission penalty is
associated with that type of said load.
35. The method of claim 15 wherein said demand information for an
electrolyser includes an amount of hydrogen currently being stored at said
electrolyser and a consumption forecast for said stored hydrogen.
36. An energy network comprising:
a plurality of generating stations;
a plurality of power loads connected to said generating stations by a
grid, said power loads including at least one electrolyser;
a fuel cell connected to at least one of said electrolysers for converting
hydrogen into electricity for introduction to said grid; and,
a controller connected to said grid and operable to adjust demand from
said power loads to approach a match of said demand with an
availability of power from said generating stations, wherein said
adjustment of availability includes activating said fuel cell for delivery of
electricity to said grid.
37. The network of claim 36 further comprising at least one generating
station having a variable availability such that said controller is operable
to
adjust availability from said generating station to match said demand.
38. The network of claim 37 further comprising a data network connected
to said controller, said network providing additional information about said
demand and said availability to said controller and which is used by said
controller to determine whether to adjust at least one of said demand and said
availability to approach a match there between.
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39. The network of claim 38 wherein said match is based at least in part on
determining which of a plurality of adjustments produces a reduced amount of
harmful emissions in comparison to another adjustment.
40. The network of claim 38 wherein said match is based at least in part on
determining which of a plurality of adjustments has a least amount of
financial
cost in the marginal cost required to produce electricity.
41. The network of claim 38 wherein said variable power loads include at
least one water electrolyser for converting electricity into hydrogen.
42. The network of claim 41 wherein said electrolyser has a known
schedule of production.
43. An energy network comprising:
a plurality of generating stations;
a plurality of power loads connected to said generating stations by a
grid, said power loads including at least one electrolyser; and,
a controller connected to said grid and operable to adjust demand from
said power loads to approach a match of said demand with an
availability of power from said generating stations, wherein said
adjustment of demand includes activating one or more of said
electrolysers to absorb excess availability of power from said
generating stations.
44. The network of claim 43 further comprising at least one generating
station having a variable availability such that said controller is operable
to
adjust availability from said generating station to match said demand.
45. The network of claim 44 further comprising a data network connected
to said controller, said network providing additional information about said
demand and said availability to said controller and which is used by said
controller to determine whether to adjust at least one of said demand and said
availability to approach a match there between.
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46. The network of claim 45 wherein said match is based at least in part on
determining which of a plurality of adjustments produces a reduced amount of
harmful emissions in comparison to another adjustment.
47. The network of claim 45 wherein said match is based at least in part on
determining which of a plurality of adjustments has a least amount of
financial
cost in the marginal cost required to produce electricity.
48. The network of claim 43 wherein said electrolyser has a known
schedule of production.
49. An energy network comprising:
a plurality of electricity generating systems;
a plurality of power loads;
means for transmitting electricity from said plurality of electricity
generating systems to said plurality of power loads;
a controller for receiving and processing data concerning one or more
of said plurality of electricity generating stations and one or more of
said plurality of power loads and for issuing instructions to one or more
of said plurality of electricity generating stations and to one or more of
said plurality of power loads;
means for transmitting data from said plurality of electricity generating
stations and said plurality of power loads to said controller; and
means for transmitting instructions from said controller to one or more
of said plurality of electricity generating stations and to one or more of
said plurality of power loads.
50. An energy network as claimed in claim 51 wherein said data
transmitted by said data transmitting means includes data concerning
availability of electricity from said plurality of electricity generating
stations and
data concerning demand for electricity from said plurality of power loads.
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51. An energy network as claimed in claim 52 wherein said instructions
transmitted from said controller by said instruction transmitting means
include
instructions to one or more of said plurality of power loads to adjust the
demand for electricity.
52. An energy network as claimed in claim 52 wherein said instructions
from said controller transmitted by said instruction transmitting means
include
instructions to one or more of said plurality of electricity generating
stations to
adjust availability of electricity.
53. An energy network as claimed in claim 52 wherein said controller
receives and processes said data and issues said instructions to approach a
match of demand from said plurality of power loads and of availability from
said plurality of electricity generating stations.
54. The network of claim 52 further comprising a data network connected
to said controller, said network providing additional information about said
demand and said availability to said controller.
55. The network of claim 55 wherein said match is based at least in part on
determining which of a plurality of adjustments produces a reduced amount of
harmful emissions in comparison to another adjustment.
56. The network of claim 55 wherein said match is based at least in part on
determining which of a plurality of adjustments has a least amount of
financial
cost in the marginal cost required to produce electricity.
57. The network of claim 51 wherein said power loads include at least one
water electrolyser for converting electricity into hydrogen.
58. The network of claim 57 wherein said electrolyser has a known
schedule of production.
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Description

CA 02511632 2008-02-08
Energy Network
PRIORITY CLAIM
[0001] The present application claims priority from Canadian Patent
Application Number 2,455,689 filed on January 23, 2004 and published on
July 23, 2005 and US Non-Provisional Patent Application Number US-2005-
0165511-A1 filed on July 14, 2004 and published on July 28, 2005.
FIELD OF THE INVENTION
[0002] The present invention is directed to the generation and
distribution of energy and more particularly to energy networks.
BACKGROUND OF THE INVENTION
[0003] Hydrogen can be used as a chemical feed-stock and processing
gas, or as an energy carrier for fueling vehicles or other energy
applications.
Hydrogen is most commonly produced from conversion of natural gas by
steam methane reforming or by electrolysis of water. Comparing hydrogen as
an energy carrier with hydrocarbon fuels, hydrogen is unique in dealing with
emissions and most notably greenhouse gas emissions because hydrogen
energy conversion has potentially no emissions other than water vapour.
[0004] However emissions that have global impact, such as CO2, need
to be measured over the entire energy cycle, which must include not only the
hydrogen energy conversion process but also the process that produces the
hydrogen. Looking at the main hydrogen production means, steam methane
reforming generates significant quantities of CO2 and, unless the emissions
are captured and sequestered which is only practical in systems that are very
large and where facilities to capture and sequester the gas are available,
these gases are released to the environment. In the case of electrolysis,
since
the electrolysis process produces no environmental emissions per se and
transmission of electricity results in little or no emissions, if the
electricity is
sourced from clean forms of power generation such as nuclear, wind or hydro,
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hydrogen production by electrolysis generates hydrogen with near zero
emissions over the full energy cycle.
[0005] One of the most frequently cited impediments to the
development of gaseous hydrogen vehicles is the lack of a fuel supply
infrastructure. Because of the relatively low volume density of gaseous
hydrogen it is not cost effective to handle gaseous hydrogen in the same way
as liquid fuels using central production at a refinery and transporting fuel
in
fuel tankers. Also unlike natural gas which is delivered to the customer
through a pipeline, there is no large-scale pipeline delivery infrastructure
for
hydrogen. Analysis of the problem has shown that in the near term, because
of the relatively low number of vehicles and hence low market demand in any
specific location, the initial infrastructure could build on the existing
energy
distribution systems, which deliver natural gas and electricity, using on-site
hydrogen production processes to convert these energy streams to hydrogen.
Using on-site production systems, a widely distributed network of fuel supply
outlets, which are sized to meet relatively small demand on a geographical
density basis, can be created. The proposed solution of using distributed on-
site fuel production systems addresses the needs of a nascent hydrogen fuel
market where it may take decades for the fleet of vehicles to be fully
converted to hydrogen.
[0006] A hydrogen distribution system having a multiple number of
fueling stations connected to one or more energy source(s) in a hydrogen
network is disclosed in US Patent 6,745,105 (Fairlie et al). The fuel stations
on the network act independently to supply local needs of hydrogen users but
are controlled as a network to achieve collective objectives with respect to
their operation, production schedule and interface to primary energy sources.
A hydrogen network as a collective can be optimized to meet a variety of
environmental and economic objectives.
[0007] Because the electrolysis process can be operated intermittently
and can be modulated over a wide range of outputs, an electrolyser fuel
station can be operated as a "responsive load" on the grid. It is also
recognized that for hydrogen networks based on electrolysis, because
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recognized that for hydrogen networks based on electrolysis, because
hydrogen can be stored, for example as a compressed gas in a tank, a
hydrogen network can become a secondary market for electricity providing
"virtual electricity storage" or demand shifting, by decoupling the electrical
energy demand for hydrogen production from when the hydrogen is used.
The fueling stations in the hydrogen network can also incorporate hydrogen
powered electricity generators such as fuel cells or hydrogen combustion
systems which can use hydrogen made by the hydrogen network to re-
generate electricity and/or thermal energy thereby acting as emergency power
generating systems or as peak shaving electricity generators to reduce costs
or emissions during peak demand periods.
[0008] Because the environmental benefits of hydrogen should be
evaluated over the full fuel cycle, it is important to the value proposition
of
hydrogen fuels to be able to measure and control accurately the emissions
created in the hydrogen production process. In most electricity market designs
electricity is a commodity and it is often difficult to differentiate and
assign
particular sources of electricity generation to a particular electricity
demand.
Hence it is difficult to precisely define the emission characteristics of
power
used in a particular application. For electrolysers connected to the grid in a
hydrogen network, the emissions created by hydrogen production are thus
often taken to be the average or pool value of the generation mix on line or
the marginal rate of emission from increasing power demand when hydrogen
is produced.
[0009] At the same time there is recognition that, in the near term,
reducing carbon dioxide and other green house gas emissions is the primary
objective of hydrogen energy and so the electrolysis solution which offers
nearly zero emission production of hydrogen is of particular interest. If the
emissions from hydrogen production could be verified, a clean "emission-free"
hydrogen could be designated by an "environmental label" and receive
emission credits such as fuel tax rebates for avoiding the CO2 emissions that
would otherwise be generated by using other fuels.
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[0010] Hydrogen energy systems have been demonstrated such as
photo-voltaic (PV) hydrogen vehicle fueling stations (Xerox/Clean Air Now),
which operate "off-grid", solely powered by renewable emission-free
electricity
generation, and hence demonstrate in conjunction with hydrogen fuel cell
vehicles a virtually emission free or "zero emission" energy system. However
PV power systems are expensive and occupy a lot of space and so other
types of clean energy systems need to be considered including wind, hydro-
electric, "clean coal" (scrubbed and CO2 captured and sequestered) and
nuclear. These power generation systems are only cost effective on a large
scale when operated like a commercial power plant and cannot be scaled
down to the size determined to be appropriate for on-site hydrogen production
in a hydrogen network (which constitutes a load of typically less than 20 MW
per fuel outlet).
[0011] Optimization of energy systems is addressed in the following
patents: US Patent 5432710 issued on July, 1995 (Ishimaru), US Patent
6512966 issued on January 28, 2003 (Lof), International Patent Application
WO 01/28017 published on April 19, 2001 (Routtenberg), US Patent 6673479
issued on January 6, 2004 (McArthur), US Patent Application 2003/0009265
published on January 9, 2003 (Edwin), US Patent 6021402 issued on
February 1, 2000 (Takriti).
[0012] None of these patents adequately address the need for a
system controlling the delivery of energy to a geographically distributed
network of hydrogen production units in an optimized way and in a way such
that environmental attributes of the hydrogen production process can be
audited.
SUMMARY OF THE INVENTION
[0013] An aspect of the invention provides an energy network
comprising a plurality of electric power generating stations and a plurality
of
variable power loads connected to the generating stations by a grid. The
network also includes a controller connected to the grid and operable to
adjust
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network also includes a controller connected to the grid and operable to
adjust
demand from the power loads to match the demand with an availability of
power from the generating stations.
[0015] The network can further comprise at least one generating station
having a variable availability such that the controller is operable to adjust
availability from the generating station to match the demand.
[0016] The network can further comprise a data network connected to
the controller, the network providing additional information about the demand
and the availability to the controller and which is used by the controller to
determine whether to adjust at least one of the demand and the availability to
achieve a match there between. The match can be based at least in part on
determining which of a plurality of adjustments produces a reduced amount of
harmful emissions in comparison to another adjustment. The match can also
be based at least in part on determining which of a plurality of adjustments
has a least amount of financial cost in the marginal cost required to produce
electricity.
[0017] The variable power loads can include at least one electrolyser
for converting electricity into hydrogen.
[0018] In another aspect of the invention, an energy network is
provided that produces hydrogen that has a specific emission profile, so that
the hydrogen produced by electrolysis has a measurable emission
characteristic that can be compared with emissions from other hydrogen
production processes such as hydrogen produced by steam methane
reforming (SMR). This is achieved by assigning specific energy flows to the
hydrogen production systems and auditing the energy flows to ensure that
they are used to produce fuel having the desired environmental values.
[0019] By assigning specific generation systems, which may be
referred to herein as "captive power producers", to produce electricity for
the
hydrogen network there is an opportunity to optimize the operation of these
systems on a large scale, where energy flows for instance exceed one
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Megawatt, in the context of the public electricity grid and electricity market
where energy can be bought and sold into a general electricity market taking
advantage that hydrogen can be stored and electricity cannot.
[0020] An aspect of the invention provides a complete energy network
encompassing electricity and hydrogen fuel production, that can serve a two-
tier market: a) a prime market where electricity demands are served and b) a
secondary market where hydrogen fuel is produced.
[0021] An aspect of the invention provides a distributed network of
electrolysis systems as a means of providing hydrogen production, providing
a method of hydrogen delivery that is cleaner than at least some other
systems. Since the electrolysis process produces little or no harmful
emissions, (i.e. the by-products are oxygen and water vapour), and since the
transmission of electricity to the electrolyser produces no emissions such as
produced by trucking tankers of fuel (either directly or indirectly through
increased traffic congestion), the harmful emissions generated by the
electrolysis process are entirely dependant on the form of primary electricity
generation.
[0022] However in many electricity markets clean forms of power
generation are not differentiated from other forms of power generation and so
clean hydrogen production cannot be demonstrated as the emission rate is
taken to be either the average emission rate of all electricity generators
producing power on the grid or the marginal emission rate of the generating
system operating when electrolysers are connected.
[0023] An aspect of the invention provides a single point hydrogen
network controller to schedule and control operation of the different
resources
connected to the network. The operation of the energy network created by the
hydrogen supply systems and captive electrical generators can be optimized
(and/or adjusted as desired) by controlling electricity flows either to the
electrolysers or to the general electricity market connected to the grid such
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that the contributions from minimizing the aggregated hydrogen production
costs and maximizing the aggregated value of power supplied from captive
power producers are maximized, subject to the production constraints of
ensuring adequate hydrogen supply at each fuel location and achieving a pre-
defined level of environmental emissions for the hydrogen produced. The
optimization produces a schedule based on optimizing the following Objective
Function by maximizing the value of the function over the time horizon control
actions can be taken:
V(t) = ~k , (RateOfFuelProductionk (t) x FuelValuek (t)) +
~~_I (AvailablePowerFromCaptiveSources, (t) x GridElectricityValue/ (t))
where K = number of electrolysers;
J = number of captive power generators; and
t =time.
Eq.1
[0024] When defining the functions in the Objective Function, the
RateOfFuelProduction function is determined by the available energy, from
"captive" and grid sources; and the fuel demand at each location on the
network (Note that the function "RateOfFuelProduction" is expressed as four
words, without spaces in between each word. This notation is followed for
other functions expressed herein.). The fuel demand depends on the
customer demand forecast over the schedule period and the amount of fuel
inventory available in storage at the start of the schedule period. The fuel
demand forecast could be determined by modeling customer demand or
through a direct measurement of hydrogen in customer storage systems.
[0025] Knowledge of the specific emission profile from electricity
generation is desirable so that the fuel production can be labeled according
to
an environmental impact specification and so if power is purchased from the
grid to supplement power from captive sources, data is needed from
measurement of the average emission rate, the marginal emission rate or a
rate which is measurable and reasonably assigns emissions given the
electricity market design or customer choices on the grid.
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[0026] The single point hydrogen network controller schedules the
operation of the electrolysers on a "day forward" basis or in a schedule
period
co-incident to the scheduling of the general power grid so that power
transactions with the grid can be scheduled. During the operating period of
the schedule, the controller would monitor operation of the different sites
and
power availability to make supply corrections to balance energy flows as
needed.
[0027] Not only can electricity demand for the network collective be
tailored to supply but so can the production rate of individual electrolysers
and
so the Hydrogen Network controller can set a production rate and hence
schedule the power consumption of each unit.
[0028] And so the controller would determine an optimal (or otherwise
desirable) hydrogen production schedule based on an electric power demand
of the electrolysers, K in number, on the Hydrogen Network:
TotalElectricPowerDemandOfElectrolysers(t) =
Ik (RateOfFuelProductionk () x
SpecificEnergyConsumptionForHydrogenProductionAtStationk (t))
Eq.2
where in the Objective Function (Eq.1):
Ek Rate OfFuelProductionk (t) = TotalRateOfHydrogenProduction(t)
Eq.3
where K = number of electrolysers; and
t = time.
which is in balance with power supplied by captive power sources, J in
number, and available power from the grid:
TotalElectricPowerDemandOfElectrolysers(t) _
,~_1 PowerForElectrolysisFromCaptivePowerSource/ (t) +
PowerForElectrolysisFromGrid (t)
where J = number of captive generators; and
t = time.
Eq.4
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such that over the schedule period the following requirements are met, acting
as constraints to RateOfFuelProduction and the optimization process:
FuelAvailablelnStationk (t + dt) = Fuellnventoryk (t) + (RateOfFuelProductionk
(t) -
RateOfFuelConsumptionk (t)) X 8t
Eq.5(a)
CustomerDemandForFuelAtStationk (t +,8t,
FuelSellingPrice)
Eq.5(b)
MaximumStorageCapacityOfStationk
Eq.5(c)
where t = time.
Eq.5
and the emissions specification as proscribed by the environmental label are
met.
[0029] Where in Eq.5(a) Fuellnventoryk is the measured amount of fuel
"on-hand" such as measured by pressure, temperature, volume in
compressed storage tanks or such as measured by pressure, temperature,
volume, mass of metal hydride in metal hydride hydrogen gas storage, where
in Eq.5(b) CustomerDemandForFuelAtStationk, being a probabilistic function,
is set to a defined confidence level of meeting the supply constraint.
RateOfFuel Consumptionk is determined by the
CustomerDemandForFuelAtStationk forecast and RateOfFuel Prod uctionk in
Eq 5(a) would be adjusted to satisfy demand constraint at all times over
schedule period. The full hydrogen storage condition, Eq.5(c), is a hard limit
constraint, however the station would be designed such that at most times it
has sufficient storage to meet demand and provide a margin for storage
capacity for making real time adjustments to energy flows when the Network
has an over supply of power.
[0030] The emission specification could define limits for a number of
different emissions including so called criteria pollutants which affect local
air
quality at the location of the power plant such as nitrous oxides, carbon
monoxide, sulphur compounds and hydrocarbon emissions as well as
emissions affecting the global environment such as carbon dioxide and other
green house gases. The environmental specification may work on an
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instantaneous value, such as in the case of criteria pollutants where air
quality
emergency procedures are triggered by achieving certain levels, or emission
standards could be proscribed by time average values measured over a
specified period of time, such, as required for green house gas reporting in
some jurisdictions. A key characteristic of the energy network is that
emissions for the whole fuel cycle including the end use applications such as
hydrogen fuel cell vehicles, can be measured and controlled very precisely
since they occur only at the power station. Because power plants already
have to comply with certain reporting requirements the emission monitoring is
often in place.
[0031] Based on specific emission profiles, hydrogen production at
each location on the network can be scheduled to take advantage of the
lowest cost combination of captive power and grid power, which meets
hydrogen production and emission requirements. The emission profile is
dependant on the emissions of specific generating processes, which also
complies with local emission standards. In the case of captive power
generation the emission profile is well defined, reporting directly to the
controller, and can be monitored. In the case of power purchased from the
grid, and depending on the market design under which the grid operates,
either an average emission value calculated for all power generators on-line
or the marginal emission rate for increase in power demand can be used.
[0032] The emission constraints on the optimization of hydrogen
production in the network can be written as:
For an emission that is not to exceed defined levels,
t,-1 (PowerForElectrolysisFromCaptiveSource, (t)
xEmissionRateForEmission,ForSource, )
+(PowerForElectrolysisFromGrid(t)xEmissionRateForEmission,ForGrid)) /
(TotalHydrogenProductionRateOfNetwork(t))
<_ ProscribedEmissionLevelForEmission,PerUnitOfHydrogen(t, LocationOfEmission)
where J = number of captive power generators; and
t = time.
Eq.6
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where the Emission, specification may depend on time and geographical
location, and for Emissionm that must not exceed a pre-defined time average:
[(lIT) ~_J (PowerForElectrolysisFromCaptiveSource, (t) x
EmissionRateForEmissionmForSource/) + (PowerForElectrolysisFromGrid(t) x
EmissionRateForEmissionmForGrid))dt] /
[(lIT) fTotalHydrogenProductionRateOfNetwork(t) dtl
<_ ProscribedTimeAvgEmissionLevelForEmissionmPerJUnitOfHydrogenProduced
where J = number of captive power generators; and
T = time interval over which the time average is to be taken.
Eq.7
[0033] In markets where emission credits are transferable from power
production to fuel production, the emission reductions from captive power
sources providing power to grid for which the Hydrogen Network owns
environmental attributes can be applied to hydrogen fuel production. In this
case Eq.6-7 would be modified to include emission credits from power
generation that could be applied against emissions generated when fuel is
produced.
[0034] The FuelValue function in the Objective Function is the selling
price of hydrogen fuel per unit of fuel produced and charged to customers,
less the cost of hydrogen production per unit of fuel produced which depends
on cost of available power to the Hydrogen Network and the other variable
process costs in operating the particular electrolysis fueling system k (ie.
cost
of water, operating maintenance etc.):
FuelValuek (t) = FuelSellingPrice(t) - FuelCost(CostOfPower(t),
FuelStation VariableProcessCostsk (t))
= GrossMarginForHydrogenProductionAtStationk (t)
where t = time.
Eq.8
The CostOfPower function is the cost of power produced by captive sources,
which depends on variable costs such as the fuel cost of the generator and
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charges for grid transmission, plus the cost of power that is purchased from
the grid:
CostOfCaptivePowerSource/ (t,VarableGeneratingCosts,
CostOfPower(t) _ 11j=1
Transmission Charges) + PurchaseCostOfGridPower(t)] /
[TotalCaptivePower(t) +AmountOfGridPowerPurchased(t)]
where
TotalCaptivePower(t) = Z~_1 PowerFromCaptivePowerSource/ (t) ;
J = number of captive power generators; and
t = time.
Eq.9
Because hydrogen can be stored at the sites, where it is being produced and
dispensed to customers, the hydrogen production cost can be minimized by
scheduling hydrogen production at times, such as low electricity demand
periods on the grid, when grid power costs and grid power generation
emissions are lowest.
Within some jurisdictions, the selling price of hydrogen from the Hydrogen
Network is another variable, which could be changed to encourage fuel
purchases to balance energy supply and demand.
FuelSe11ingPrice(t) = Price(CustomerDemand(t),SupplyCapabilityAtTimeOfWeek,
CompetitionPricing)
where t = time.
Eq.11
For example the period of lowest electricity demand and as a consequence
lowest cost and lowest stress on supply system is typically on weekends and
holidays. As a consequence because this a favoured time to produce
hydrogen, the price of hydrogen could be lowered to promote consumption
during these periods. In this way through the FuelValue function and meeting
constraint Eq. 5, fuel price can enter into the system optimization to balance
energy flows in the Network, and would be part of the schedule information
sent to the fuel station network.
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The AvailablePowerFromCaptiveSources function in the Objective Function is
the total power available from captive sources less the captive power that is
committed to the electrolysers for hydrogen production and is the power that
could be sold by the Hydrogen Network to the Public Electricity
Grid:
AvailablePowerFromCaptiveSources(t) = TotalCaptivePower(t) -
YJ PowerForElectrolysisFromCaptivePowerSource1.(t)
j=1
Eq.12
where
TotalCaptivePower(t) _ J PowerFromCaptivePowerSourceJ . M;
j-1
Eq.13
J = number of captive power generators; and
t = time.
The GridElectricityValue function in the Objective Function depends on the
selling price for captive power in the electricity market of the electrical
grid,
which can also include environmental credits from supply of captive power.
GridElectricityValue(t) = CaptivePowerSellingPrice(t,GreenAttributes(t)) -
CostOfCa p tivePo wer(t)
= GrossMarginForCaptivePowerSaleToGrid(t)
Eq.14
where
CostOfCaptivePower(t) _ j 1 CostOfCaptivePowerSourcej (t) /
TotalCaptivePower(t)
Eq.15
J = number of captive power generators; and
t = time.
In some energy markets these credits, called "green tags", may be
transferable between the stationary power market and the transportation
(hydrogen fueling) market, and hence could be transferred to hydrogen
production and used to meet emission constraints in Eq.6-7. In some power
markets the emission credit is dependent on the power it is displacing, or the
marginal emission rate. Depending on the electricity market design, the
ability
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to sell power into peak demand electricity markets can contribute
significantly
to the energy network, since it is competing with peak power generators which
are more expensive, because of poor utilization, and which often have higher
specific emission rates.
The optimization can be performed over a specific time interval so as to
determine an operating schedule and fuel pricing and so as to optimize
operating cost subject to constraints of maintaining fuel supply reliability,
insuring sufficient fuel is available at each station to meet customer demand
and meeting the emission objective that the hydrogen produced has specific
and verifiable emission characteristic over the whole production cycle on an
instantaneous or time average basis as proscribed by the emission standard.
The same scheduling algorithms can be used in longer running hypothetical
demand scenarios to determine the mathematically optimized number, size
and location of fueling outlets needed to satisfy demand in a region and the
necessary commitment to invest in captive electricity generation as well as
the
type of generation as it relates to the specific emission profile required to
insure specifications of the environmental label are met.
The fueling of hydrogen vehicles presents a potentially large load on the
grid.
Projections for North American markets have shown that electrical power
required to fuel a fleet of fuel cell vehicles equivalent to the gasoline
powered
vehicles on the road today would double the amount of energy handled by the
grid, and so the power transfers of the Hydrogen Network could have a huge
impact on the grid. Because the electrolysers can act as "responsive loads"
reacting very quickly and their production rate, and hence power range, can
be varied over a wide range, an energy network under control of a network
controller as taught herein can provide ancillary services to the electricity
grid
such as providing operating reserves and even generator control services to
insure electricity network stability. These ancillary services if contracted
and
paid for by the grid operator would be provided at the request of the Public
Grid Operator and would act as conditional constraints on the system.
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Typically the request for Grid Power Supply Change would be in the form of a
directive to increase or lower fuel production at specific hydrogen generators
or groups of generators over time t to t +At depending on geographical
location hence through:
_
GridPowerSupplyChangeAtStationk (t + At)
(RateOfFuelProductionk (t + Lit) - RateOfFuelProductionk (t)) x
SpecificPowerConsumptionForHydrogenProductionAtStationk (t + Lit)
where t = time.
Eq.16
where the new RateOfFuelProduction at time t+dt is now fixed for the period
the request is in effect. Applying this constraint may require other resources
on the network to adjust schedule to meet production constraints.
[0035] For example during the daily ramp up and ramp down in
electricity demand, the Hydrogen Network can disengage and engage
electrolysers either making power available to the grid from captive
generation
or reducing the electricity supply by absorbing power from the grid. Because
of the responsiveness of these systems the Hydrogen Network can earn
additional revenue in these periods from the Public Electricity Grid operator,
and because of the distributed nature of hydrogen production units in the
Hydrogen Network, they can provide ancillary services to individual
generators as well as transmission lines addressing transmission capacity
constraints. The services provided by the electrolysers as "responsive loads"
in the Hydrogen Network can be supplemented by hydrogen powered
electricity re-generation, which could be available at the hydrogen fueling
stations and which also could be under the control of the Hydrogen Network
Controller.
[0036] In some cases the request may not be load specific. In this case
the provision of these services would be guided by the same optimization in
Eq.1-15 in terms of calculating value for captive energy flows however in this
case if contracted to provide services in terms of shedding load or increasing
loads the Network must react to the grid operator request to meet these
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requirement thus becoming an instantaneous operating constraint on the
system; modifying Eq.4.
_
GridPowerSupplyChangeAtStation,, (t +,8t)
{ ~J (PowerForElectrlysisFromCaptivePowerSource1 . (t + at)) +
1-~
PowerForElectrolysisFromGrid(t + dt)}-
l jJ_ (PowerForElectolysisFromCaptivePowerSourceJ. (t)) +
1-1
PowerForElectrolysisFromGrid(t)}
where J = number of captive power generators; and
t = time.
Eq. 17
[0037] For example if the Hydrogen Network is contracted to provide
operating reserves and the grid operator requests a Grid Power Supply
Change but not from specific loads then the Hydrogen Network Controller
would increase CaptivePowerSellingPrice in Eq. 14 reducing fuel production
in Eq. 1 until sufficient power is made available to make up the power which
the Network has been contracted to supply. If on the other hand the Grid
operator requests that the Hydrogen Network absorb a power supply surge,
the Hydrogen Network Controller responds by reducing the value of
CostOfGridPower in Eq. 9 increasing fuel production in Eq. 1.
[0038] In the case of the hydrogen network providing ancillary services,
the operating schedule would be conditional on demands from the grid
operator and so contingencies in terms of storage capacity and the amount of
fuel stored to meet customer demand in Eq. 5 and emissions in Eq. 6-7 would
be needed to ensure the Network operates within these constraints.
[0039] Under highly constrained market conditions, hydrogen fuelled
power regeneration or back up power units could play the role of captive
power sources, in cases such as providing back up power locally to grid under
emergency conditions or if there is a demand spike in the electricity market.
In
this case the regenerative systems act as captive power sources, which are
run when the CaptivePowerSellingPrice exceeds the variable cost of
regenerating power (Eq.9), based on, fuel cost = selling price of hydrogen,
(Eq.11) and hence, under these conditions, when operating the unit is
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profitable. This may occur even while hydrogen is being produced on the
Network. For example, when power demand on the grid exceeds available
supply but one or more fueling stations on the Network have insufficient
inventory to meet demand (Eq.5), and so must produce fuel. In this case a
virtual transfer of hydrogen fuel from one station to another can be
transacted
through the electrical grid.
[0040] An energy network in accordance with the invention could be a
wholesale buyer and seller of electricity and would operate as a hydrogen-
electricity utility having captive sources of energy with defined emission
characteristics which it controls either through bi-lateral contracts with the
electricity generators or which it owns out-right. In this way the energy
network owns the environmental attributes of specific power sources
generating electricity in a specified period. Because the network-wide
hydrogen production requirements are significant, and given that hydrogen is
being used to fuel a large fleet of hydrogen vehicles, the energy transfers
into
and out of the general electricity grid will have a significant impact on
energy
balances in the public electricity supply.
[0041] The optimization of the resources in the energy network
according to methods proscribed can also impact the design and layout of the
physical resources particularly through a desire to minimize and/or reduce
transmission charges and maximize and/or increase effectiveness of power
regeneration systems. Generally speaking the fueling stations constitute a
distributed load which will be located in the same locations as general
electrical demand and so, as it is unlikely that the power demand of fuel
stations will exceed transmission capacity at a given location if the fuel
stations operate in periods of low electricity demand, no special transmission
allowances or arrangements with the grid will be needed beyond those
already in place. Also in designing the network there is an inherent trade-off
between production capability and storage.
[0042] Based on the system characteristics however, the energy
network designer can further optimize the design of the network based on
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following factors, which are a consequence of the energy network and
optimization:
[0043] Locating the hydrogen generation at points on the electricity grid
or network to relieve periods of excess supply over demand, or instability
where a renewable energy source is connected and making available a
hydrogen application that can absorb the hydrogen such as injection of
hydrogen in a natural gas pipeline;
[0044] Locating hydrogen generation and/or hydrogen storage and
regeneration at points on the grid or network to relieve periods of excess
demand for fuel, power and/or heat;
[0045] Locating hydrogen generation and/or hydrogen storage at points
on the grid where the capacity of the grid itself is constrained relative to
the
available supply or demand for power;
[0046] Locating hydrogen power regeneration at locations to distribute
operating reserves and improve system reliability to avoid need for committing
larger units of generation;
[0047] Providing hydrogen fuel from the distributed network of
hydrogen energy storage devices as stores become depleted or additional
demand is expected; and
[0048] Providing a supplemental load to permit base load plants to
operate at their optimum efficiency and lowest emissions during periods of low
demand.
[0049] The network operator could also work closely with the other
power generators on the public grid to make power purchases bilaterally to
reduce emissions through demand management of specific generators such
as natural gas fired generation where a significant drop in efficiency occurs
when power levels are reduced and hence a significant increase occurs in
specific emissions (emission gm per kWh). By increasing loads through
hydrogen production the generator can be more efficient and hence produces
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lower specific emissions. In this way the network can also act to improve the
efficiency of the public grid.
[0050] These actions could be formally contracted by selling ancillary
services to the grid. Because the network can adjust energy flows between
captive power plants and hydrogen production in a very precise fashion and
on a "real-time" basis the system can provide short-term operating reserves to
the grid and even "spinning reserves" by making a certain proportion of the
demand for fuel production a "responsive" load. In this way, in the event of
outage of a generator or transmission line and the network is contracted to
provide operating reserves, the network controller would be notified and would
turn down the rate of hydrogen production to make power available as
required. Similarly in dynamic control, when load is picking up at the
beginning of high demand periods or during periods when load is dropping off,
the network can operate as a variable power generator to facilitate the ramp
up of power plants. For some forms of generation that are currently used,
such as coal powered generators, this will reduce start up times and increase
the efficiency of operation, resulting in lower specific emissions. Where the
electrical load is large enough, the network could be used to dynamically
adjust load in the electrical network to improve efficiency and reduce cost
through potentially maintaining a higher level of control than otherwise
available by adjusting output of conventional power generators. The tighter
control of the grid will result in efficiency improvement benefits which will
accrue to the network and which also lower specific emission rates for the
grid. These actions could be enhanced by regenerative systems that can be
part of the network through "hydrogen energy stations" which incorporate
power regeneration from hydrogen fuel with hydrogen production.
[0051] The list of ancillary services provided by the Hydrogen Network
could include: "spinning" type reserves (<1 minute dispatch time), operating
reserves, emission reductions (i.e. air quality emergency) and to some degree
generator control as well as relieving local grid congestion.
[0052] The provision of ancillary services could contribute significantly
to the value of the Hydrogen Network. The ancillary services themselves
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would be service requests from the grid operator which having been
previously contracted to the grid would act as constraints in the optimization
in
Eq.1
[0053] An ancillary service request would act like a higher level or
"overriding" constraint on the Network optimization constraint either through
Eq.16 specifying a certain load be increased or shed in the Hydrogen
Network or in the case of a non-specific change in power level through
optimization of the resources subject to changing power available to grid.
[0054] The impact on design of the network so that the network can
provide ancillary services, would be an increase in storage capability in the
system and a general increase in inventory to account for conditional
constraints and insure fuel supply reliability.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will now be explained, by way of
example only, with reference to the attached figures in which:
Figure 1 is a schematic representation of an energy network in
accordance with an embodiment of the present invention;
Figure 2 is a graph of electricity demand from conventional loads in the
network;
Figure 3 is a graph of output power available from certain power
stations in the network;
Figure 4 is a flowchart showing a method of operating an energy
network in accordance with another embodiment of the invention;
Figure 5 is a flowchart showing a set of sub-steps that can be used to
perform one of the steps in the method of Figure 4;
Figure 6 is an energy network in accordance with another embodiment
of the invention; and,
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Figure 7 is an energy network in accordance with another embodiment
of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0055] Referring now to Figure 1, an energy network is indicated
generally at 50. Network 50 includes a plurality of electrical power
generating
stations 54 (also referred to herein as electrical generating stations or
electricity generating stations). In a present embodiment, electrical
generating stations include a coal power plant 58, a nuclear power plant 62, a
natural gas power plant 66, and a wind-farm 70. As will be discussed in
greater detail below, each electrical generating station 54 has a profile
relating
to the amount of energy it can generate, and another profile relating to the
environmental pollutants associated with that energy generation.
[0056] Network 50 also includes a power grid 74, which is substantially
the same as any conventional electrical power distribution grid, including
transmission lines, power stations, transformers, etc. as is currently known
or
may become known.
[0057] Network 50 also includes a plurality of electrolysers 78, that are
connected to grid 74, and which are operable to convert electricity from grid
74 into hydrogen, and store that hydrogen locally. The configuration and type
of electrolyser is not particularly limited, and can be any type of
electrolyser
that are currently known or may become known. Electrolysers 78 thus appear
as an electrical demand to grid 74 when they are activated to convert
electricity from grid 74 into hydrogen.
[0058] (As used herein the term, electrolyser means any system that
includes an electrolytic hydrogen generator and/or other means to generate
hydrogen from electricity and/or other equipment and/or associated
equipment to render such a system operable to convert electricity into
hydrogen and/or store hydrogen. Thus, such a system can also comprise
gauges, storage tanks, water sources, pumps, dispensing equipment, etc. as
the context of the particular embodiment being described may require to
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CA 02511632 2007-04-24
provide the function described in association with that electrolyser, as will
be
appreciated by those of skill in the art who are implementing such
embodiments or other features of the invention.)
[0059] In a present embodiment, three electrolysers 78 are included in
system 50. A first electrolyser 781 supplies a fuel cell 82, which is operable
to
convert hydrogen received from first electrolyser 781 into electricity for use
by
a plurality of consumers 86.
[0060] A second and third electrolyser, indicated at 782 and 783
respectively, are also included in network 50. Electrolyser 782 and 783 are
essentially hydrogen filling stations operable to a) generate hydrogen from
electricity b) store that hydrogen and c) supply hydrogen to hydrogen-
powered vehicles ("HPV") 90 that periodically stop at electrolysers 782 and
783 in order to obtain hydrogen fuel. While not included in the present
embodiment, it is to be understood that other hydrogen applications are within
the scope of the invention, in addition to the supply of HPVs, for example,
industrial hydrogen.
[0061] Network 50 also includes a plurality of conventional consumer
loads 92 as are currently found on prior art electricity grids, such as
residences, factories, office towers, etc.
[0062] Of particular note, network 50 includes a first set of transmission
lines 94 that connect stations 54 to grid 74, that include physical cabling to
allow power to be delivered from stations 54 to grid 74. By the same token,
transmission lines 94 also include additional data cabling to allow feedback
from grid 74 to those stations 54 about demand in network 50, and also to
include specific instructions from grid 74 to increase or decrease output, as
appropriate or possible depending on the type of station 54.
[0063] Thus, network 50 also includes a second set of transmission
lines 98 that connect grid 74 to electrolysers 78, that include physical
cabling
to allow power to be delivered from grid 74 to electrolysers 78. By the same
token, transmission lines 98 also include additional data cabling to allow
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feedback from electrolysers 78 to grid 75 about demand and overall levels of
reserve hydrogen stored at those electrolysers 78.
[0064] Network 102 also includes a controller 102 that is connected to
grid 74, via data cabling 106. Through data cabling 106, controller 102 is
operable to receive data from the data cabling associated with transmission
lines 94 and 98 and thereby maintain awareness of outputs being generated
by stations 54, as well as demands experienced by electrolysers 78. By the
same token, controller 102 is operable to issue instructions to stations 54
and
electrolysers 78 to vary supply and/or demand, respectively, as appropriate
and/or within the inherent limitations of stations 54 and electrolysers 78.
Further details about controller 102 will be provided below.
[0065] Network 50 also includes a data network 110, such as the
Internet, that is connected to controller 102, through which various energy
market information is available, and through which controller 102 can update
the energy market information posted on data network 110 and thereby notify
other entities connected to network 110 about the status of energy network
50. The details of data network 110 and such energy market information will
be discussed in greater detail below. Controller 102 connects to data network
110 via any suitable backhaul 114, such as a T1, T3, or the like.
[0066] As will be understood by those of skill in the art, network 50 has
an energy demand profile that can be compiled from historic data of demand
activity on network 50 and which can be used to provide a fairly accurate
prediction of future demand activity. Table I shows an energy demand profile
caused conventional consumer loads 92. Figure 2 shows a graphical
representation of the energy demand profile listed in Table I, indicated at
118.
Table I
Exemplary Demand Profile of Loads 92
Time Demand
(GW
12:00:00 AM 10
1:00:00 AM 10
2:00:00 AM 10
3:00:00 AM 16-
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Time Demand
(GW)
4:00:00 AM 10
5:00:00 AM 10
6:00:00 AM 10.5
7:00:00 AM 11
8:00:00 AM 12
9:00:00 AM 13
10:00:00 AM 14
11:00:00 AM 15
12:00:00 PM 16
1:00:00 PM 16
2:00:00 PM 16.5
3:00:00 PM 17
4:00:00 PM 16
5:00:00 PM 15
6:00:00 PM 14
7:00:00 PM 13
8:00:00 PM 12
9:00:00 PM 11
10:00:00 PM 10.5
11:00:00 PM 10
12:00:00 AM 10
[0067] It can thus be seen that loads 92 have a substantially fixed (i.e.
predictable) energy demand profile. In contrast to loads 92, however, the
demand profile caused by electrolysers 78 can be characterized as being "on-
demand", in that their energy demand profile can be dynamically matched to
the availability of energy in network 50. Put in other words, since
electrolysers 78 can be used to create and store hydrogen at any time,
regardless of when that hydrogen is to be consumed by fuel cell 82 and/or
HPVs 90, it is possible to choose at which times that electrolysers 78 will be
activated to store hydrogen for later use by fuel cell 82 and/or HPVs 90.
[0068] Network 50 also has an energy availability profile that reflects
the output of energy from stations 54. However, such an energy availability
profile is not as predictable as the energy demand profile 118. This is due to
the unique nature of the power generation equipment, and as such the
availability profile of each type of station 54 will vary. For example, output
from nuclear power plant 62 will be fairly constant, due to the fact that
startups
and shutdowns of nuclear power plants are difficult. This means that any
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excess power from nuclear power plants in a network such as network 50
needs to be shunted to a non-consumer load, thereby wasting the power. By
the same token, output from wind farm 70 is extremely random, subject to
fluctuations in weather and wind conditions. The random nature of the output
from wind farm 70 makes it difficult to match the output of wind farm 70 with
the demand shown in demand profile 118. Table II shows an exemplary
energy availability profile from nuclear power plan 62 and wind farm 70.
Figure 3 shows a graphical representation of the combined nuclear and wind
energy availability profile listed in Table II and is indicated generally at
122.
Table II
Exemplary Availability Profile of Nuclear Power Plan 62 and Wind-Farm
Time Nuclear Wind
(GW) (GW)
12:00:00 AM 8 2
1:00:00 AM 8 3
2:00:00 AM 8 0
3:00:00 AM 8 2
4:00:00 AM 8 1
5:00:00 AM 8 2
6:00:00 AM 8 0
7:00:00 AM 8 1
8:00:00 AM 8 1
9:00:00 AM 8 3
10:00:00 AM 8 0
11:00:00 AM 8 2
12:00:00 PM 8 2
1:00:00 PM 8 0
2:00:00 PM 8 0
3:00:00 PM 8 1
4:00:00 PM 8 0
5:00:00 PM 8 0
6:00:00 PM 8 1
7:00:00 PM 8 0
8:00:00 PM 8 0
9:00:00 PM 8 2
10:00:00 PM 8 2
11:00:00 PM 8 3
12:00:00 AM 8 0
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[0069] It can thus be seen that the energy availability profile of a station
54 such as nuclear power plant 62 is substantially fixed, whereas the energy
availability profile of a station 54 such as wind farm 70 is substantially
random.
[0070] In contrast to nuclear power plant 62 and wind farm 70, other
stations 54 can be characterized as being "on-demand", in that their energy
availability profile can be dynamically matched to the demand being
experienced by network 50. Thus, coal power plant 58 and natural gas power
plant 66 can be considered "on-demand" power stations 54, that are operable
to generate power on an as-needed basis according to the overall energy
demand profile of network 50.
[0071] As is understood by those of skill in the art, the on-demand
aspect of plants 58 and 66 make them suitable for helping to dynamically vary
the amount of power being generated by stations 54 to match the needs of
the energy demand profile 118 of conventional loads 92. As is also
understood by those of skill in the art, a skillful combination of
substantially
fixed power stations (i.e. nuclear) with "on-demand" power stations can be
used to match the energy demand profile 118 of conventional loads 92.
However, such combination is more difficult when random power stations
(such as wind farm 70) are introduced. Also, a period of overproduction can
lead to at least a temporary need for shunting power output from nuclear
power plant 62.
[0072] (While not included in network 50, it will now be understood by
those of skill in the art that in other embodiments, network 50 can include
other types of stations 54, that can also be classified as fixed, random, "on-
demand", and/or combinations thereof. One example of another type of
station 54, with its own availability profile is a plurality of solar panels,
which
can be less random than wind farm 70, but still more random than nuclear
power plant 62. A still further example of an "on-demand" station is a hydro-
electric generating dam: because of hydraulic storage in the reservoir, the
output can be throttled to meet load. For example hydro-electric generators
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can be used to control grid frequency - so called automatic generation control
(AGC)).
[0073] Referring to Figure 4, a method for controlling an energy
network is indicated generally at 400. In order to assist in the explanation
of
the method, it will be assumed that method 400 is operated using controller
102 to control network 50. Furthermore, the following discussion of method
400 will lead to further understanding of network 50. (However, it is to be
understood that network 50 and/or method 400 can be varied, and need not
work exactly as discussed herein in conjunction with each other, and that
such variations are within the scope of the present invention.)
[0074] Beginning first at step 410, demand information is received.
Such information is received at controller 102, from electrolysers 78 and
conventional loads 92, along the data cabling associated with transmission
lines 98 and via grid 74. Such demand information can take the form of
information regarding each electrolyser 78, plus a demand profile of
conventional loads 92 such as demand profile 118. The information
associated with each electrolyser 78 would include the amount of hydrogen
currently being stored in each hydrogen tank associated with its respective
electrolyser 78, as well as forecasts of expected hydrogen demand at each
respective electrolyser 78, to provide an estimate of how long the remaining
amounts of hydrogen stored at that electrolyser 78 will last, and/or to
estimate
how long the electrolyser 78 will need to be run in order to keep up with
future
demands.
[0075] Next, at step 420, availability information is received. Such
availability information can take the form of availability profile 122, and
can
also include the on-demand capacity that is available from coal power plant
58 and natural gas power plant 66.
[0076] Next, at step 430, it is determined whether the demand
information received at step 410 matches availability information received at
420. If there is a match, then method 400 returns to step 410 and method 400
begins anew. If however, there is a mismatch, then method 400 advances to
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step 440. What constitutes a match, will of course typically include a
provision for a certain amount of excess availability to match any spikes in
demand. The amount of excess availability to be provided can be determined
using known techniques.
[0077] Next, at step 440, demand is adjusted, or availability is adjusted,
as appropriate, in order to bring the availability and demand closer towards a
match. For example, where only nuclear power plant 62 and wind farm 70 are
operational, and where the combined availability from nuclear power plant 62
and wind farm 70 exceed the current demand from conventional loads 92,
then controller 102 can instruct one or more of electrolysers 78 to commence
hydrogen production, and thereby consume that excess demand. The criteria
for picking which ones of electrolysers 78 should commence production of
hydrogen is not particularly limited, and can include a determination of the
amount of hydrogen currently being stored at that electrolyser 78 and/or the
forecast for hydrogen consumption at that electrolyser 78. Wherever need is
greatest, then that electrolyser 78 can be activated, subject to constraints
in
the capacity of transmitting over grid 74.
[0078] As another example of how step 440 can be performed, where
only nuclear power plant 62 and wind farm 70 are operational, and where the
combined availability from nuclear power plant 62 and wind farm 70 is below
the current demand from the combination of conventional loads 92 and
electrolysers 78, but still exceeds the amount of demand from conventional
loads 92, then one or more electrolysers 78 can be instructed to cease
hydrogen production to bring the demand down to a level that matches with
the availability from nuclear power plant 62 and wind farm 70.
[0079] The frequency with which method 400 cycles is based, at least
in part, on the ability of various elements in network 50 to react to
instructions
issued at step 440 from controller 102. Accordingly, it is to be understood
that
the demand information received at step 410 also includes a certain degree of
forecasting that takes into account the amount of time needed to activate or
deactivate an electrolyser 78 and/or a power plant such as power plant 58
and 66. Thus controller 102 may schedule the operation of the electrolysers
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78 on a "day forward" basis or in a schedule period co-incident to the
scheduling of the general power grid so that power transactions with grid can
be scheduled. During the operating period of the schedule controller 102
monitors operation of the different electrolysers 78 and power availability to
make supply corrections to balance energy flows as needed, and ensure that
various contract obligations between different entities that operate different
portions of network 50 are being complied with. Also, since the operator of
electrolysers 78 is typically different than the operator of grid 74, it is
contemplated that the operator of electrolysers 78 can schedule power sales
and purchases with the operator of grid 74 to optimize their value and the
second level of dynamic control where electrolysers are used to manage
demand, either managing random resources or providing ancillary service
type functions. Thus, the particular frequency and way in which method 400
cycles will be affected by this type of scheduling, and such variations should
now be apparent to those of skill in the art.
[0080] Referring to Figure 5, an exemplary set of sub-steps for
performing step 440 of method 400 is indicated generally at 440a. Beginning
at step 500, a determination is made as to whether demand is greater than
the availability. This can be performed by controller 102 simply monitoring
the
level of demand experienced by electrolysers 78 and conventional loads in
relation to the availability from generating stations 54. If demand exceeds
availability, then the method advances to step 510 at which point a
determination is made if there is any additional availability. This is also
performed by controller 102, which examines the output from generating
stations 54 to see if there is any additional capacity for generation from any
one or more of those stations 54. If there is additional availability (i.e.
not all
stations 54 are operating at peak capacity), then the method advances to step
520 where controller 102 can instruct an appropriate one of stations 54 to
produce additional power to meet the demand.
[0081] If, however, at step 510 it is determined that there is no
additional availability, then the method advances to step 530 at which point a
determination is made as to whether there is excess demand. Put in other
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words, a determination is made as to whether any of the electrolysers 78 that
are currently `on' can be turned `off' (or at least scaled back in power
consumption) in order to ease the overall demand on grid 74.
[0082] If it is determined at step 530 that there is excess demand, then
the method advances to step 540 and at this point demand is decreased to
match the availability, by turning `off' (or scaling back power consumption)
of
an appropriate one of electrolysers 78. Typically, an electrolyser 78 that had
a sufficient amount of hydrogen in its holding tanks to meet short term
hydrogen demand would be the candidate chosen for scaling back power
consumption from grid 74.
[0083] However, if, in the unlikely event that it is determined at step 530
that there is no excess in demand (for example, all electrolysers 78 are
turned
"off" and the excess demand is being created by conventional loads 92), then
the method will advance to step 550 for exception handling. A situation as
this can result in brown outs or rolling blackouts throughout conventional
loads 92, or, more likely, the operator of grid 74 would pull on any available
reserves in the network, and/or make use of any other network to which grid
74 is attached to obtain reserves, given the requirement for operators of
grids
to have such reserves available to avoid brown outs and blackouts.
[0084] Returning to step 500, if it is determined that availability is
greater than demand at step 500, then the method will advance to step 550 at
which point a determination will be made as to whether there is any additional
demand that can be added to grid 74 to make up for the excess availability.
For example, where controller 102 determines that one or more electrolysers
78 are not "on" or otherwise at full capacity to produce hydrogen, then it
will
be determined at step 550 that there is additional demand that can be added
to grid 74, and so the method will advance to step 560 and demand will be
increased on grid 74 to match that availability. Thus, typically at step 560
controller 102 will instruct an appropriate one or more of electrolysers 78 to
begin hydrogen production and thereby absorb the excess availability from
power station 54. This situation could arise where wind farm 70 is
experiencing a high level of wind which is providing additional availability
to
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grid 74, such that the overall availability from power stations 54 exceeds the
demand from conventional loads 92, then controller 102 can determine which
electrolysers 78 are in need of hydrogen production, and accordingly, instruct
an appropriate one of those electrolysers 78 to begin hydrogen production
and thereby absorb the excess availability from power station 54.
[0085] However, if at step 550 it is determined that there is additional
demand that can be added to grid 74, (i.e. all electrolysers 78 are "on" and
operating at full capacity) then the method will advance to step 570 at which
point a determination will be made as to whether there is any excess
availability. Put in other words, a determination is made as to whether any
power stations 54 can be turned "off', or have their production scaled back,
in
order to reduce the availability to match the demand on grid 74. For
example, if natural gas power plant 66 is operational, then production of
power therefrom can be scaled back to reduce the overall availability from
stations 54 and the overall availability towards a match with the demand.
[0086] However, if at step 570 it is determined that there is no excess
availability then the method will advance to step 550 for exception handling.
For example, where all stations 54 are "off" except nuclear power plant 62
then power from nuclear power station 62 can be shunted into a power sink,
or, in very rare circumstances, nuclear power station 62 will be shut down.
Typically nuclear power stations will simply continue to operate and dump
load by shunting excess power to the generation of steam. (Alternatively, in
some cases excess hydrogen production could be dumped into natural gas
pipelines.)
[0087] It should now be apparent that method 400 can be modified to
provide a high level of sophistication to match availability with demand. For
example, each power station 54 can be identified by a number of different
criteria that can be used in the process of determining which power stations
54 should be turned "off" or turned "on" in order to match current demand.
Table III shows an exemplary set of criteria that can be associated with each
power station 54.
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Table III
Power Station Criteria
Station Station Emission Fuel Type Efficiency Availability
Owner Type Rating Response
Coal A Corp Dirty CO2 Coal A High
power
plant 58
Nuclear B Corp Nuclear Uranium B Fixed
power Waste
plant 62
Natural C Corp Clean CO2 Natural B High
gas Gas
power
plant 66
Wind- B Corp None Renewable A Random
farm 70
[0088] For greater detail, Table III shows five columns of criteria
associated with each power station 54. Column 1 is the Station Owner, which
indicates the private or public entity that actually owns and operates the
power station 54. Column 2 is the Emission Type, which indicates the type of
effluent or emissions or other harmful substances generated by that station.
Thus, note that coal power plant 58 is considered "Dirty C02", while natural
gas power plant 66 is considered "Clean CO2", meaning that while both plant
58 and 66 produce carbon dioxide ("CO2"), the overall emissions from plant 66
are considered cleaner (i.e. less criteria pollutants and lower CO2 emissions
per kWh generated) and less harmful to the environment. By the same token,
note that nuclear power plant 62 is classified as producing nuclear waste,
which is not an emission but still harmful to the environment and/or awkward
to store in a safe manner. Finally, note that wind farm 70 is considered to
have no emission type, since it does not generate emission.
[0089] Column 3 of Table III indicates the type of fuel that is used by
each power station 54. Column 4 of Table III indicates an efficiency rating
associated with each power station 54. An "A" rating according to the present
example is considered to be of higher efficiency than a "B" rating. (However,
note that such efficiency ratings relate to the efficiency of a particular
power
station 54 in relation to other power stations 54 that are based on the same
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fuel type. Different stations 54 of the same fuel type can then be compared
based on their efficiency in relation to each other. However, in the present
example all stations are of different types, so the efficiency rating
described
below is simply a contributing factor in determining the cost of operating a
particular station 54.) Finally, Column 5 of Table III refers to the
availability
response of each power station 54. Thus, coal power plant 58 and natural gas
power plant 66 are considered to have high availability and therefore to be
easily added or removed from operation and overall availability to grid 74.
(Other factors can affect the availability even of high availability stations -
- for
example, the availability of coal as a fuel is relevant since it takes time to
fire-
up a coal boiler.) Nuclear power plant 62 is considered to have a fixed
availability and therefore not easily added or removed from operation and
overall availability to grid 74. Wind farm 70 is considered to be random, and
therefore also not easily added or removed from operation and overall
availability to grid 74.
[0090] By the same token, each electrolyser 78 and conventional loads
92 can be identified by a number of different criteria that can be used in the
process of determining which demands placed on grid 74 can or should be
turned "off" or turned "on" in order to match availability. Table IV shows an
exemplary set of criteria that can be associated with electrolyser 78 and
conventional loads 92.
Table IV
Demand Criteria
Load Owner Load Type Emission Hydrogen Demand
Penalty? Storage Response
Capacity
Electrolyser D Corp Electrical No High High
781
Electrolyser E Corp HPV Filling Yes Medium High
782 Station
Electrolyser F Corp HPV Filling Yes Low High
783 Station
Conventional Local Electrical No None Fixed
Load 92 utility
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[0091] For greater detail, Table IV shows six columns of criteria
associated with the loads on grid 4. Column 1 identifies the load, as
previously described. Column 2 is the Owner of the load, which indicates the
private or public entity that actually owns and operates the load. Column 3
indicates the load type, also as previously described. Column 4 indicates
whether there is an emission penalty associated with the means by which the
power was generated. In other words, where the Emission Penalty indicates
"No", it means that there is no additional cost (such as taxation) levied
against
the owner of the load, regardless of whether the power station 54 that
generated the power actually used by the load actually generates emission or
not. However, where the Emission Penalty indicates "Yes", it means that an
additional cost (such as taxation) will levied against the owner of the load,
if
the power station 54 that generated the power actually used by the load
generates emission. Thus, in the example given in Table IV, where the load
is used to fill HPVs with hydrogen, then an emission penalty will be levied,
but
if the load is simply delivering electricity to consumers, then no emission
penalty is levied. (Alternatively, or additionally, such an emission penalty
may
be calculated according to the end use application. In a market like
transportation fuel, penalties typically apply, depending on amount and type
of
emission, such penalty being comparable to the fuel equivalent suppliers such
as gasoline, or other types of hydrogen suppliers such as Steam Methane
Reformers ("SMR")).
[0092] Column 5 of Table IV identifies the hydrogen storage capacity,
and thus electrolyser 78, is indicated as having a "high" level of storage
capacity; electrolyser 782 is indicated as having a "medium" level of storage
capacity; and electrolyser 783 is indicated as having a "low" level of storage
capacity; and conventional loads 92 have no storage capacity. Finally,
Column 6, Demand Response, identifies that electrolysers 78 have a "high"
level of demand response in that they can be quickly turned "off" or "on" (or
set to some level in between based on hydrogen demand constraints) by
controller 102, while conventional loads 92 cannot turned "off" or "on" by
controller 102, and are a fixed demand on grid 74.
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[0093] It should now be apparent that the various types of criteria are
merely exemplary and that other criteria can be provided as desired. It should
also now be apparent that method 400 can be operated in a more
sophisticated manner than earlier described by having the information in
Table IV be received at step 410 as part of the demand information, and the
information Table III be received at step 420 as part of the availability
information. The determination as to whether there is a "match" at step 430,
and the adjustments performed at step 440 can thus be very sophisticated by
utilizing various weights of criteria provided in Table III, Table IV and in
conjunction with the current operating realities of system 50.
[0094] Many examples of how such adjustments are made at step 440
will now occur to those of skill in the art. As one very simple example, such
adjustments can be based simply on a pure match between the owner of the
load with the owner of the power station. In other words, if D Corp (owner of
electrolyser 781) has agreed to buy power from C Corp (owner of natural gas
plant 66), then controller 102 can be configured to ensure that electrolyser
78,
is activated at times that natural gas plant 66 is active so that the amount
power delivered to electrolyser 78, matches a certain level of output from
natural gas plant 66.
[0095] More sophisticated matching is typically contemplated however,
as various weights are applied to each of the criteria in Table III and Table
IV
as a way of arriving at which electrolysers 78 are activated or deactivated to
increase or decrease demand, and/or which power stations 54 are activated
or deactivated to increase or decrease availability to achieve a desired match
there between.
[0096] Still further sophisticated matching is contemplated as controller
102 is provided with information data network 110 that can be related to the
other information in Tables III and IV to achieve a desired match in demand
and availability, and thereby provide additional demand information at step
410 and availability information at step 420. Table V shows an exemplary set
of criteria that can be provided over data network 110.
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Table V
Demand Criteria
Power Efficiency Marginal Emission
Station Fuel Rating Cost Cost
Type
Coal A $0.08/kWh $0.04/kWh
Coal B $0.10/kWh $0.05/kWh
Natural Gas A $0.09/kWh $0.02/kWh
Natural Gas B $0.11/kWh $0.03/kWh
Uranium A $0.07/kWh $0.01/kWh
(Nuclear)
Uranium B $0.09/kWh $0.02/kWh
(Nuclear)
Wind A $0.10/kWh $0.00/kWh
Wind B $0.11/kWh $0.00/kWh
[0097] Thus, the information Table V can be used by controller 102 in
conjunction with the information in Tables III and IV to arrive at a cost
determination associated with using a particular power station 54 to provide
power to a particular electrolyser 78 and/or conventional loads. Thus, note
that when supplying electrolyser 782 and electrolyser 783 the emission cost in
Table V will need to be added in to arrive at a total cost for producing power
to
meet the demand of that load, however, such emission cost would not be
needed when determining costs for supplying electrolyser 78, and
conventional loads 92. It should now be apparent that Table V can reflect
market data that is updated on a continuous basis using data from an energy
exchange or other market for trading energy. It should also now be apparent
that the concept of "emission cost" can be based on many different forms --
such as tonnage of emitted C02, NO, CO etc., nuclear fuel waste and/or other
hazardous material that is emitted by a particular power station 54. Such
emission cost can be based on government emission credits or taxes, and/or
actual hazardous material disposal costs, and/or emission levels related to
these costs which are less than pre-defined limits for purpose of labeling
fuel
in certain markets, and/or the like. It should also be understood that the
concept of marginal cost in Table V is merely for demonstration purposes and
that other concepts of marginal cost can apply. For example, a marginal cost
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(cost of next kWh) can be the marginal cost of electricity required to produce
hydrogen, which would relate to marginal electricity price from electricity
producers. In a competitive electricity market the marginal cost of the grid-
connected resources can be determined by the market spot price, whereas for
captive power generators it can be the fuel price determining whether they
supply. In electricity spot market nuclear or wind are "price takers", because
if
on they are committed. This detail in design of an energy network can vary
according to where the network is deployed.
[0098] Other costs that could be included into Table V include marginal
and/or emission costs that are reduced for off-peak usage and/or transmission
costs.
[0099] In general, it should now be understood that the availability
information can include one or more types and quantities of emission
produced per unit of electricity produced for each power station. Examples of
types and quantities of emission include a measurement of the mass (e.g.
kilograms or tons) of emitted C02, NO, CO, etc. per kWh of electricity
produced by a given generating station. Similarly, the demand information
can include an emission penalty associated with that load, and the adjusting
of demand and availability can be made at least in part by adjusting
availability at one of the power stations having a reduced amount of
pollutants
produced per kWh in relation to another one of the generating stations. It
should now be apparent that this can provide a means of attributing the
amount of emissions produced by a given HPV or fleet of HPVs using a
particular electrolyser, by tracing back the electricity used by that
electrolyser
to generate the hydrogen for that HPV to a particular generating station. As
part of its function, controller 102 can track this information and keep
records
thereof to provide a method of also verifying the amount of emissions
attributable to a particular electrolyser and/or HPVs that fuel up at a
particular
electrolyser. Such verification can be later used for a variety of purposes,
such as an audit trail proving that a particular set of laws or regulations or
treaties are being complied with.
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[00100] In another embodiment of the invention, HPVs 90 are equipped
with wireless transmitters that communicate with via data network 110 to
controller 102. The transponders identify the location of each HPV 90 in
relation to electrolyser 782 and electrolyser 783, and identify the amount of
hydrogen fuel that is stored in the HPV 90. Controller 102 is then operable to
estimate whether a particular HPV 90 is more likely to refuel at electrolyser
782 or electrolyser 783, and thereby assess the hydrogen demand needs of
electrolyser 782 or electrolyser 783 and to schedule production of hydrogen
for
those electrolysers 78 accordingly.
[00101] Referring now to Figure 6, an energy network in accordance
with another embodiment of the invention is indicated generally at 50a.
Network 50a includes the same elements as network 50, and like elements in
network 50a bear the same reference as their counterparts in network 50,
except followed with the suffix "a". In contrast to network 50, however,
network 50a also includes an additional set of transmission lines 118a that
connect fuel cell 82a to grid 74a. In this configuration, fuel cell 82a can be
a
load in relation to grid 74a that supplies power to consumers 86a, or, fuel
cell
82a can be an additional power station that can provide additional power to
grid 74a, (and thereby provide power to 92a) to add to the power already
being provided by power stations 54a. Controller 102a can thus be used to
issue instructions to fuel cell 82a to behave as a power station and supply
power to grid 74a, or controller 102a can leave fuel cell 82a to simply supply
power to consumers 86a attached thereto. Network 50a also allows for a
means to, in effect, ship or transport hydrogen from electrolyser 78ai to
electrolyser 78a2 and/or electrolyser 78a3 without the need to physically
transport the hydrogen between those destinations. In this way the operator
of grid 74a has additional control over flows and also can collect fees for
hydrogen transmission service. Also note that the cost of transporting
hydrogen by truck or train can then be compared with the cost of transporting
hydrogen by converting it to electricity and carrying through the grid. Such
cost comparisons can also include relative efficiencies between transportation
methods. (i.e. the amount of fuel burned, and emissions generated by the
truck that would be used to physically carry the hydrogen from the source
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electrolyser to the destination electrolyser, vs. the amount of hydrogen
produced at the destination electrolyser in relation to the amount of hydrogen
required to generate the electricity used to power the destination
electrolyser
during generation of hydrogen at the destination electrolyser.)
[00102] Also, as the operator of grid 74a is typically required to abide by
reliability regulations that require back up power generators be available on
various levels of response (i.e. "spinning" to provide a fifteen minute
response
time) such back up power can be made available by having the operator of
grid 74a contract for such backup power with the operator of electrolyser 78a1
with the view that hydrogen reserves at electrolyser 78a, can be converted
back into electricity that is returned to grid 74a for general consumption
(e.g.,
at 92a).
[00103] Referring now to Figure 7, an energy network in accordance
with another embodiment of the invention is indicated generally at 50b.
Network 50b includes the same elements as network 50, and like elements in
network 50b bear the same reference as their counterparts in network 50,
except followed with the suffix "b". In contrast to network 50, however,
network 50b includes a hybrid hydrogen/natural gas power plant 122b that
can receive hydrogen from electrolyser 78b1. Hybrid hydrogen/natural gas
power plant 122b primarily utilizes natural gas to generate electricity or
heat
for consumers 86b, but in a present embodiment, hybrid hydrogen/natural gas
power plant 122b is also operable to utilize hydrogen available from
electrolyser 78b1 in the event that natural gas is unavailable or it is
otherwise
desirable to burn hydrogen rather than natural gas. The foregoing
embodiment is illustrated herein for demonstration purposes, and is presently
less preferred as it can be inefficient to use electricity to generate
hydrogen
and to then generate electricity because round trip efficiency is presently no
better than about 30%. However, this embodiment can be applied when
storage capability and transmission capability of a pipeline can be used as
way of storing electricity -- for example the natural gas power plant could be
a
peaking plant. (i.e. a plant that that provides power at peak demand (and
typically peak market) times. Typically fast responding gas turbines are used
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as "peaking generators"). Also, where the energy conversion involves heat as
well as electricity there is an improvement in efficiency as heat energy that
is
otherwise waste is also captured for some use. Also, such reconversion may
be useful where emission concerns are being addressed - for example
reducing NOx emissions in power turbine through hydrogen injection.
[00104] While only specific combinations of the various features and
components of the present invention have been discussed herein, it will be
apparent to those of skill in the art that desired subsets of the disclosed
features and components and/or alternative combinations of these features
and components can be utilized, as desired. For example, while electrolysers
are discussed as a type of load whose demand can be varied dynamically in
other embodiments such variable loads can be batteries, fly-wheels and/or
other energy storage devices as desired. Other storage systems include
pumped hydraulic and compressed air, and applications such as hot water
heaters could operate the same way, except that they do not offer the
opportunity to provide fuel to vehicles in the way hydrogen provides power to
HPVs. Other types of electrolysers can be included such as electrolysers
used for industrial applications. The industrial electrolyser example is
particularly desirable where grid 74 is engaged in interuptability contracts
with
the industrial electroylsers. As will be appreciated by those of skill in the
art,
so called "Interruptibility Contracts", can be used for large electrolysers
producing hydrogen for industrial applications, where such electrolysers can
be turned off for certain periods on signals from the grid operator. The grid
operator would pay a monthly rate of, e.g., $10-$20/kW of interruptible power
for the right to effect such interruptions. During the interruption periods,
the
industrial application would take hydrogen from storage. Such discounts for
interruptions, combined with emission credits, can provide desirable value, in
for example, reducing the amount of time needed to pay back the capital cost
for installing the industrial electrolyser plant. Such interuptibility
contracts can
be administered by controller 102, as controller 102 instructs various
electrolysers to cease production according to contracts between grid 74 and
those electrolysers, based on instructions fro grid 94.
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[00105] While the embodiments herein generally contemplate that
portions of network 50 are owned and/or operated by a single entity, it is to
be
understood that, in practice, different entities will typically operate
different
portions of network 50. For example, the operator of grid 74 can be different
than the operator of electrolysers 78 and/or stations 54 and/or loads 92
and/or
controller 102. Where grid 74 is independently owned and operated, it is
typical that all power transfers on grid 74 are cleared by the grid operator.
As
another example, where controller 102 is owned and operated by the same
party that owns and operates electrolysers 78, then controller 102 can act as
a broker between electrolysers 78 and the various ones of stations 54 to
arrange for an optimum or otherwise desired match (i.e. based on cost,
emission, etc.) between the demands of electrolysers 78 and availability from
stations 54.
[00106] In general, it should now be apparent that the embodiments
herein can be useful for improving overall stability of an electricity grid.
In
particular, electrolysers can be responsive loads, dynamically being added or
removed from the overall demand on the grid, which can ease instability as
the grid experiences ramping up and ramping down of demand during a given
twenty four period. This improvement in stability can in and of itself be a
service delivered by the operator of the electrolysers and the network
controller to the operator of the grid, charging a fee to the operator of the
grid
for providing such stability. By the same token, the ability to offer
operating
reserves to the operator of grid (as shown in network 50a) can also be a
service for which the operator of the electrolysers can charge a fee to the
operator of the grid.
[00107] The above-described embodiments of the invention are intended
to be examples of the present invention and alterations and modifications may
be effected thereto, by those of skill in the art, without departing from the
scope of the invention which is defined solely by the claims appended hereto.
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Representative Drawing