Note: Descriptions are shown in the official language in which they were submitted.
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PCT/EP2009/001023
Dynatronic GmbH
Heating System Producing Electricity
The present invention relates to a heating system for a property, including a
thermal interconnection between a thermal heat generator, in particular a
conventional heating system, and a plurality of heat consumers for
simultaneous
production of heat and electricity, the thermal interconnection being
controlled by
a control unit, one of the heat consumers including a conversion system based
on a thermodynamic cycle, in particular a water vapor or an ORC or Kalina
process, and provided for the conversion of thermodynamic energy into
electrical
energy, and the condensation heat occurring in the thermodynamic cycle being
transferred to further heat consumers.
As regards the following description, reference is made to the attached "List
of
terms used and their meanings" and the "List of abbreviations".
The brochure "Kurzinfo: Lion"Powerblock" (as at October 2007) of OTAG
Vertriebs GmbH & Co. KG, Olsberg, Germany (http://www.otag.de/download/
071007_Lion_Kurzinfo_2007_D.pdf) presents a heating system for residential
properties according to the prior art. Essential components of this system are
a
gas burner, a steam-based thermodynamic circuit consisting of a tube
evaporator
and a heat exchanger for condensation of the water vapor and for transferring
the
condensation heat to the heating circuit. The steam pressure energy generated
is
first converted into linear kinetic energy by means of a double free-piston
uniflow
steam engine and then into electric power with the aid of a linear generator
coupled thereto. The supply of steam into the working chamber of the free
piston
is controlled mechanically by way of slide valves which are firmly connected
with
the piston rod and, depending on the piston position and piston velocity, open
and close the inlet for a specific time that can not be controlled further. As
a
result of this, the piston path in which the inlet is open is always fixed and
is
therefore optimally designed for one working pressure only. The lower working
pressures occurring, e.g., during start-up or switch-off can therefore not be
optimally exploited since this requires a relatively longer opening of the
inlet to
ensure a full utilization of the expansion chamber.
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After the piston has performed its expansion work, it travels over an opening
in the cylinder wall which serves as an outlet for the expanded water vapor
until
such time as the piston closes the opening again in its return movement,
which,
for one thing, results in that compression work is to be performed on the
steam
remaining in the cylinder in order to push the piston to its initial position
again.
This compression work is carried out by the contradirectional working cycle of
the
double free piston, accompanied by the losses in the energy conversion which
inevitably appear in the process. For another thing, the piston is unable to
perform the maximum possible expansion work since at the moment when the
piston travels over the outlet opening, an overpressure must still be present
in the
working chamber for the remaining water vapor to flow into the condensation
chamber at all, something which leads to further conversion losses.
A further drawback of this known mini CHP (combined heat and power) unit
results from the use of water as the medium for the thermodynamic cycle since
water will only condense at 100 C at normal pressure. But since the domestic
heat consumers often require only distinctly lower temperature levels, such
as,
e.g., in the operation of a floor heating system with a flow temperature of 50
C
max., the maximum possible efficiency of electric power generation, which is
based on the spread between vaporization temperature and condensation
temperature, is not exhausted thereby. While a cycle using water vapor as the
medium and involving condensation temperatures of below 100 C is also
conceivable, the negative pressure resulting therefrom is difficult to
maintain in
the long run due to leakages that can be hardly avoided for technical reasons.
For a more economic way to generate electricity by means of a mini CHP unit,
the following characteristics would additionally be worthwhile:
- An efficient generation of electricity should be possible also at times when
there is no heating demand, in order to ensure a higher utilization of the
unit;
- the heating system should be able to effectively utilize the thermal energy
from thermal solar collectors, which is excessively available in summer, for
generating electricity;
- the heating system should be able to automatically adjust the condensation
temperature of the thermodynamic cycle to the variable low temperature level
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provided, such as, e.g., heating return temperatures, in order to achieve a
maximum temperature spread; and
- the electricity generation unit should not be bound to a particular type of
combustion plant (gas, oil, pellets, etc.).
The current state of the art relating to heating systems with a simultaneous
thermal heat production and an electricity production based on a thermodynamic
process is characterized by the following features:
(a) only one single heat generator: a conventional heating system which is
configured as a gas heating in order to reach the high temperatures
required in the thermodynamic process;
(b) the heating system is combined with a thermally coupled heat
accumulator in which the thermal heat produced by the heating system
can be temporarily accumulated and be passed on to a heat consumer
offset in time. The equilibrium between the thermal energy generation
and the thermal energy demand results according to the following
formula:
EHeiz(t) + ESP OUT(t) = E,NVd (t) + EHW (t) + ETHDY(t) + Esp IN(t)
where: Esp ouT(t) = EWW (t) + EHW (t)
and thus the following applies: EHe;z(t) = ETHDY(t) + Esp IN(t),
(c) the system has only one mode of operation, in which, by means of a
system of converting thermodynamic to electrical energy, electricity is
produced and the condensation heat arising in the thermodynamic
process fills the heat accumulator at the same time;
(d) there exists no thermal interconnection to a thermal heat sink provided
at the property and which is exploited in an efficiency-increasing manner
in the production of electricity;
(e) there exists no thermal interconnection to thermal solar collectors
provided at the property and which are exploited for solar electricity
production;
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(f) there exists no thermal interconnection to a waste gas heat recovery
system provided at the property and which is exploited in an efficiency-
increasing manner in the production of electricity;
(g) the thermodynamic cycle is based on a single-stage water-steam circuit;
(h) the conversion of thermodynamic to electrical energy is effected either
by means of a combination of a uniflow steam engine with a linear
generator of a type having two contradirectional pressure cylinders as
are used in conventional free piston systems, with one working chamber
always remaining unutilized and only one pressure cylinder carrying out
the working cycle at a time alternately. In principle, the capacity (power)
of the conversion system is adjustable through the repetition frequency
of the working cycles, with the conversion system being however
realizable only based on a constant ratio of inlet pressure to outlet
pressure due to an absence of a possibility of a closed-loop control of
the inlet volume per working cycle, which in turn leads to the fact that the
condensation temperature, which is dependent on the outlet pressure, of
the thermodynamic cycle is not adjustable;
(i) an equalization of the inconstant consumption of energy of the heat
consumers is effected by means of the heat accumulator filling level.
The operating mode is active until the heat accumulator filling level has
exceeded an upper limit, and becomes active again as soon as the filling
level has fallen below a lower limit. The following applies here:
PHeiz(t) = PTHDY(t) + Ps IN(t)
where: PTHDY(t) = f (input temperature TTHDY-In)
Generally, the following boundary conditions and requirements are to be
taken into account for an economic electricity generation by a thermodynamic
process by means of a mini CHP unit:
- A high efficiency in electricity generation is achievable only when great
temperature differences are involved, i.e. an output temperature of the
heating
system that is as high as possible (> 300 C) is required and, in particular in
the
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generation of electricity when there is no heating demand, a condensation
temperature that is as low as possible (< 20 C) is required;
- at present, no working medium is known which can be used for technically
implementing a thermodynamic process in this temperature range demanded and
which has thermodynamic properties which, in addition, allow a high efficiency
in
the generation of electricity. In addition to the high boiling point, which is
a
disadvantage, water further has the characteristic that a high superheating of
the
steam is required to allow an expansion with dry steam, which has a negative
effect on the thermodynamic efficiency;
- in a mode of operation "generation of electricity when there is no heating
demand", a very high cooling capacity at as low a temperature level as
possible
(< 20 C) is required for the condensation heat arising, but such cooling
capacity
is realizable from the environment only with high prime costs involved (e.g.,
water
cooling circuit with geothermal probe) or by a high expenditure of energy
(e.g., by
a heat exchanger having ventilators); and
- for residential properties, only a low noise emission caused by the
conversion system is acceptable.
Furthermore, the problem has to be solved of how the various heat
generators, heat accumulators and heat consumers can be thermally coupled to
each other in the most favorable way.
According to the invention, provision is made in a heating system of the type
initially mentioned that the heating system is operable in at least one of two
modes of operation, wherein in the first mode of operation the heat generated
is
supplied to the thermodynamic cycle for producing electricity and the residual
heat resulting from the thermodynamic cycle is used for heating, and in the
second mode of operation electricity is produced independently of the heating
demand in that a heat sink absorbs the condensation heat of the thermodynamic
process. Advantageous and expedient configurations of the heating system
according to the invention will be apparent from the dependent claims.
The invention is primarily geared to a heating system for residential
properties, which is used to heat the rooms of a property and/or the domestic
service water of the property (heat consumers). For the first time, a system
is
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proposed in which a conventional heating system is combined with a
thermodynamic circuit, for instance with an ORC circuit (Organic Rankine
Cycle)
"on a small scale" (i.e. not in industrial plant engineering or power plant
construction) to provide in this way an efficient option for generating
electrical
power. Until now, ORC installations have been rarely made use of in the low
load
range since the efficiency of conventional ORC installations in this range is
generally considered to be too low.
The invention provides a heating system which avoids the above-mentioned
disadvantages of the prior art by one or more preferred measures and meets the
additional requirements. These preferred measures relate both to improvements
in the basic system structure and improvements in respect of a demand-oriented
efficiency- and cost-optimized design of each individual component, and also
to
an optimized overall system structure resulting from the additional
requirements.
A special overall system consisting of a combination of the advantageous
measures listed below leads to a preferred technical realization of the
heating
system which, based on the thermodynamic system design, results in a
maximum energy efficiency in the conversion of thermodynamic to electrical
energy:
(a) a thermal interconnection to a thermal heat sink provided at the property
for increasing the efficiency in the production of electricity and for
realizing a further mode of operation, "Production of electricity only";
(b) a thermal interconnection to thermal solar collectors for generating solar
electricity by means of a thermodynamic process in the low temperature
range and for realizing a further mode of operation, "Production of solar
electricity", in which electricity is produced with the aid of the thermal
solar collectors;
(c) a thermal interconnection to a waste gas heat recovery system which is
provided at the property and is exploited by means of a thermodynamic
process in the low temperature range for increasing the efficiency in the
production of electricity;
(d) a technical realization of a combined heat and power generation having
a very wide temperature spread beneficial to the Carnot efficiency, of
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from approx. 20 to 300 C using a medium which is suitable for the
extended temperature range for a single-stage thermodynamic cycle, in
particular thermal oils or silicates, having a critical temperature above
the exit temperature of approx. 300 C and which ideally does not create
a negative pressure relative to the ambient pressure, also in the low
condensation temperature range at the level of the heat sink;
(e) the use of a very efficient multistage thermodynamic cycle having a high
temperature circuit and a low temperature circuit, preferably both being
ORC circuits, electricity being generated from both circuits;
(f) the use of a valve-controlled, possibly double-acting pressure cylinder/
linear generator system which is optimally suited for this application and
is adjustable in respect of both the transfer capacity and the inlet
pressure/outlet pressure ratio by the closed-loop control of the inlet
volume or of the expansion path per working cycle;
(g) or, as an alternative to (f), the use of a suitable a rotational
conversion
system for converting thermodynamic energy into mechanical rotational
energy, in particular using a DiPietro engine;
(h) as a further improvement regarding (g): the rotational system includes a
rotational generator, in particular an RMT generator;
(i) the control unit controls a capacity (power) adaptation required owing to
the additional heat generators in the different modes of operation, it
being prevented that the heating system needs an adjustable capacity,
and the thermal equilibrium in the different modes of operation being
balanced either by a power regulation in the conversion system for
converting thermodynamic into electrical energy or by means of closed-
loop control of an accumulator inflow PSP IN(t) and thus by way of the
accumulator filling level of the heat accumulator;
(j) the use of a high temperature heating system, in particular a high
temperature biomass combustion plant, as the heat generator.
Generally, the thermal coupling according to the invention, of a heat sink
provided at the property, configured as, e.g., an air moisture heat exchanger,
a
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geothermal collector, a geothermal probe, a body of water, an air cooling
system
or a cold reservoir, allows an additional mode of operation in which
electricity can
also be produced at a time when there is no heating demand, by the heat sink
absorbing the condensation heat of the thermodynamic cycle. By the thermal
coupling of a heat sink provided at the property to the thermodynamic cycle, a
maximum temperature spread is reached between the temperature level of the
medium prior to expansion (TTHDY-In) and the temperature level of a heat sink
(TWa) provided at the property.
The theoretically possible Carnot efficiency in the conversion of the thermal
energy thus results from the formula:
I1CARNOT = 1 - TWs / TTHDY-In
Especially advantageous with respect to the maximum possible Carnot
efficiency is the use of a special high temperature heating system, in
particular a
biomass combustion plant configured in this way, such as, e.g., a wooden
pellets
heating system allowing medium outlet temperatures TH Out of above the boiling
point of water, in particular with outlet temperatures of greater than 300 C.
In order to be able to exploit the high outlet temperatures of the high
temperature heating system, a thermodynamic circuit medium (e.g., thermal
oils)
suitable for this temperature range and having a critical temperature above
the
outlet temperature of the high temperature heating system is required.
The generation of electricity with the aid of the thermodynamic cycle is
effected in that the working medium, preferably a cooling agent having a low
boiling point, is vaporized, a high pressure being produced by the
vaporization.
This pressure can be extracted as mechanical kinetic energy in the form of
volume change work during the expansion of the gas and be converted into
electrical energy in the process.
Preferred is a medium which is suitable for the thermodynamic cycle, e.g.
thermal oils, or an ORC medium which is specially developed for this
application
and which, in addition to the good heat transfer characteristics required,
also
distinguishes itself in that no negative pressure relative to the ambient
pressure
arises in the medium in the required low condensation temperature range since
the efficiency of the thermodynamic cycle is reduced by an ingress of air
during
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negative pressure conditions, which is difficult to avoid in the long term for
technical reasons. Furthermore, the superheating of the vaporized gas required
prior to expansion should be as small as possible since the energy added
during
superheating does not increase the energy yield of the thermodynamic cycle.
The control unit manages the energy distribution and, based on periodically
determined measured data, adjusts an equilibrium between thermal energy
generation and thermal energy demand according to the formula
EHeiz(t) = EU4w (t) + EHW (t) + ETHDY(t) + ERest(t).
According to a special embodiment of the invention, a valve-controlled piston
engine is provided which can be used for separately and variable setting the
inlet
and outlets periods of each working cycle. For one thing, this results in that
under the given conditions, each expansion proceeds under optimum pressure
conditions. For another thing, based on the inlet period the inlet volume is
controlled and thus the outlet pressure of the medium after expansion has been
effected, which in turn allows the temperature of the medium after the
expansion
of the thermodynamic cycle to be able to be variably adjusted to maximum
temperature required at the moment of conversion, of one of the heat
consumers.
Ideally, the condensation of the medium then also takes place at this
temperature
level. Therefore the maximum possible portion -- under the given circumstances
-- out of the thermal energy available is used for electricity generation. The
equilibrium between the thermal energy generation and thermal energy demand
is periodically determined and adjusted by the control unit here preferably
according to following formula:
EHe z.(t) = Eww (t) + EHw (t) + ETHDY(t)
A further improvement in the energy utilization is achieved by a thermally
coupled heat accumulator in which the thermal heat produced by the heating
system can be temporarily accumulated and be passed on to at least one heat
consumer offset in time. Owing to this thermal interconnection, the heating
system always only needs to be put into operation for a short time for heating
purposes. Furthermore, as will be described below, the heat accumulator also
allows the solar energy to be utilized both for heating purposes and for solar
electricity generation. The heat accumulator preferably is a heat accumulator
of
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an additive configuration having different temperature levels (stratified
storage
tank), in which a heat exchange takes place both in the flow line and in the
return
flow in each case at a selectable, best possible temperature level available
in the
heat accumulator. In addition to the extensively used buffer vessels, other
types
of accumulator are also conceivable, such as, e.g., space-saving latent heat
accumulators with an accumulator medium which performs a phase change,
preferably from solid to liquid, in the required accumulator temperature
range, or
a thermochemical heat accumulator. The equilibrium between thermal energy
generation and thermal energy demand is periodically determined and adjusted
here by the control unit preferably according to the following formula:
EHea(t) + Esp ouT(t) = Eww (t) + EHW (t) + ETHDY(t) + Esp IN(t)
Based on data from sensors for detecting process-influencing parameters, the
control unit automatically adjusts the most favorable operation at and for
each
particular point in time by changes in the process control variables (such as,
e.g.,
flow velocity of the circuits, etc.). On the basis of sensor data, each heat
exchange between individual components of the heating system is adjusted by a
closed-loop control of the heat flows occurring, such that the transfer of the
thermal energy of the respectively warmer medium to the respectively colder
medium is as effective and complete as possible. The control unit can also
include information from an electricity supplier of the property into the
process of
controlling the heating system to allow a production of electricity in
particularly
profitable periods of time.
The equilibrium between thermal energy generation and thermal energy
demand is periodically determined and adjusted by the control unit preferably
according to the following formula:
EHeiz(t) + Esp ouT(t) = Eww (t) + EHw (t) + ETHDY(t) + Esp IN(t) + ERest(t)
By means of sensors for detecting process-influencing parameters, the
control unit independently sets one or more of the modes of operation
characterized below:
(a) Mode of operation "Heating, WW and production of electricity"
Function Energy transmission Temperature levels and
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preferred temperature ranges
Heating, WW heating, EHeiz+ Esp OUT = TH Out = TTHDY-In > 300 C
and THDY production of
ETHDY+ EI1W+ Esp IN +Eww THK VL =TSp In = TTHDY-Out = TWW =
electricity
TKond = TH In= 45..85 C
Fig. 5
THK RL = TSp out = 20..70 C
(b) Mode of operation "Exclusive production of electricity from thermal heat"
Function Energy transmission Temperature levels and
preferred temperature ranges
THDY production of EHeiz = ETHDY+ ERest TH Out = TTHDY-In > 300 C
electricity from thermal
ERest = Ews TTHDY-out = TKond = Tws in = 15..25 C
heat
Tws Out = < 20 C
Fig. 6
(c) Mode of operation "Standstill".
In connection with the temperatures indicated above, an ideal situation
without losses in the thermal transmission is assumed in which the control
unit
adjusts the operation at the respectively most favorable temperature spreads.
One difficulty in the technical realization of the thermal equilibrium between
thermal energy generation and thermal energy demand in a plurality of modes of
operation is constituted by the required load distribution between the
individual
components, which need to have a power throughput dependent on the mode of
operation and on the condensation temperature. The following must always
apply:
PHeiz(t) + Psp oU1(t) = PWW (t) + PHW (t) + PTHDY(t) + PSp IN(t) + PWs(t)
The generator side of the equation can always be equalized for all modes of
operation by the use of a heating system which is controllable in terms of the
power PHei7(t) and which generates a constantly high output temperature TH out
at
a constant thermal transfer efficiency, independently of the power required.
The
consumer side of the equation can always be equalized by a variable power
throughput of the thermodynamic conversion system PTHDY(t), which, however,
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additionally requires a closed-loop control for the condensation temperature.
An
additional option resides in regulating the heat accumulator input power PSP
IN(t)-
The technical realization of a heating system having a controllable heating
power PHeiz(t) at the required high output temperatures TH Out > 300 C is
difficult.
It is therefore of advantage if the heating system can be operated at a
constant
heating power PHei,, irrespectively of the mode of operation, by the required
load
distribution being effected either by means of the variable accumulator inflow
PSp IN(t) or by means of an adjustable power throughput PTHDY(t) of the
thermodynamic conversion system.
The dynamic load distribution required has the following effect on the
relevant
modes of operation:
(a) Mode of operation "Heating, WW and production of electricity"
The thermal equilibrium of this mode of operation reads as follows:
EHeiz(t) + Esp OUT(t) = ETHDY(t) + EHW(t)+ Esp IN(t) +Eww(t)
The heat accumulator absorbs the condensation heat of the thermodynamic
process and, at the same time, the heat consumers are supplied from the heat
accumulator. Thus the following applies:
ESp OUT(t) = EWW (t) + EHW (t)
EHeiz(t) = ETHDY(t) + ESP IN(t)
ESp IN(t) = EHeiz(t) - ETHDY(t)
On the power level this means:
PSP IN(t) = PHeiz(t) - PTHDY(t)
At a constant heating power:
PHeiz(t) = PHeiz = constant
While this mode of operation is active, the power throughput PTHDY(t) of the
thermodynamic conversion system is constant:
PTHDY-Heizk at TKond = THeizk RL
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This results in a constant accumulator inflow:
PSp IN = PHeiz - PTHDY-Heizk
An equalization of the inconstant energy consumption of the heat consumers
is effected by means of the heat accumulator filling level. The operating mode
is
active until the heat accumulator filling level has exceeded an upper limit,
and
becomes active again as soon as the filling level has fallen below a lower
limit.
(b) Mode of operation "Exclusive production of electricity from thermal heat"
No regulation by means of the accumulator inflow takes place here. The
thermal equilibrium of this mode of operation reads as follows:
EHeiz(t) = ETHDY(t) + ERest(t)
and, hence:
PTHDY(t) = PHeiz - Pws(t)
When the temperature level Tws is sufficiently low, a constant cooling
capacity
Pw5 can be taken from the heat sink. Thus, the following applies:
PTHDY(t) = PTHDY = constant at TKond = TWs
While this mode of operation is active, the power throughput PTHDY(t) of the
thermodynamic conversion system is constant:
PTHDY-Strome = PHeiz -- Pws
When it is intended to operate the heating system at an equally high heating
power PHeiz irrespectively of the mode of operation, this means:
PHeiz-Stromp = PHeiz- Heizk = PHeiz- Heiz Solar = PHeiz- Solar
This results in a separate power level for PTHDY for each mode of operation:
Mode of operation (a) PTHDY-Heizk = PHeiz - PSp IN
Mode of operation (b) PTHDY-Stromp PHeiz- PW.
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Due to the lower temperature of the heat sink, PTHDY-Strome is higher than
PTHDY-
Heizk. When the temperature levels of TWS and THeizk RL are unequal, the
following
applies:
PTHDY-Strome # PTHDY-Heizk
One option to realize a heating system with only two modes of operation, (a)
and (b), and a constant conversion power PTHDY and a constant heating power
PHeiz is obtained when the temperature level of the heat sink equals the
return
temperature of the radiators THeizk RL.
When TKond = THeizk RL = TWs
then PHeiz = PTHDY-Stromp = PTHDY-Heizk applies.
The maximum Carnot efficiency reduced thereby for this system thus results
from:
I1CARNOT = 1 - THeizk RL. / THeiz
A further option to realize a heating system having a constant heating power
PHeiz is obtained when the outlet pressure constantly corresponds to the
temperature level of the heat sink TWS. The mode of operation (a), which, as a
result, is no longer applicable, must therefore be replaced by a mode of
operation
in which the heating system 2 produces thermal energy exclusively for use as
thermal heat and for WW heating, with the appropriate heat circuits needing to
be
integrated for this purpose, of course. While this requires a conversion
system
having a variable conversion power PTHDY(t), an advantage of this application
resides in that the conversion system only needs to implement a constant ratio
of
the inlet pressure to the outlet pressure and the power can be controlled by
means of the repetition frequency fyc. Realization is possible using a turbine
or a
uniflow steam engine, for example.
Here the following applies: PTHDY(t) = f(ff,,c)
The maximum Carnot efficiency of this application results from the following
formula:
fCARNOT = 1 - THeizk RL / THeiz
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A preferred option for producing electricity is a linear conversion system for
converting thermodynamic energy into electrical energy, which is coupled to
the
thermodynamic cycle and includes one or more pressure cylinders, a linear
generator, and a filter and rectifier unit. The linear conversion system
provides
for a piston/cylinder unit which is coupled to the thermodynamic cycle and
specifically matched therewith, for initially converting the thermodynamic
energy
into kinetic energy from which electrical energy is then produced by means of
a
linear generator that is likewise specifically matched with this application,
and the
electrical energy is converted by means of a grid-based frequency converter
into
an AC voltage suitable for being fed to the grid. A suitable pressure
cylinder/
linear generator arrangement distinguishes itself by a high overall conversion
efficiency, low prime costs, quiet operation as well as by a long service life
as
there are no transverse or rotational forces.
A special aspect of the conversion system consists in that by means of a
valve-controlled piston engine, the inlet and outlet times of each working
cycle
can be adjusted separately and variably. This results, for one thing, in that
under
the given conditions, each expansion proceeds under optimum pressure
conditions. For another thing, based on the inlet time the inlet volume is
controlled and, hence, the outlet pressure of the medium after the expansion
is
completed, which in turn allows the temperature of the medium after the
expansion of the thermodynamic cycle to be variably adapted to the temperature
required at a maximum at the moment of conversion, of one of the heat
consumers. Ideally, the condensation of the medium likewise takes place at
this
temperature level. As a result, the highest possible amount - under the given
circumstances - of the thermal energy available is used for generating
electricity.
To prevent the piston from striking against the cylinder head or cover, it is
possible, in principle; to limit the piston stroke in that the piston rod is
coupled to
an idling crankshaft, for example.
A further possibility of avoiding a hard strike consists in that the expansion
stroke available is not completely utilized for decompression and the
remaining
piston travel is realized by way of a magnet snapping. Here, the induction
force
that guides the piston up to the stop is adjusted such that only small forces
act
upon impact, thus allowing long-lasting operation.
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In a thermodynamic pressure cylinder conversion system having a variable
conversion power PTHDY(t), the conversion power is obtained from the product
of
the number of working cycles (strokel and stroke2) and the work performed by
one piston stroke WTHDY and the cycle frequency fcyc:
PTHDY(t) = 2* WTHDY * fCyc(t)
The work WTHDY performed is a function of the constant cylinder dimensions
and the variable parameters:
WTHDY _ f (TVaporiz VEini, TKond)
= Tvaporiz: temperature of medium - inlet pressure of medium
= VEinl: inlet volume per stroke
= TKond: condensation temperature - outlet pressure of medium
At constant, high Tvaporiz and in conversion systems having a constant inlet
volume per stroke VE;n,, the outlet pressure of the medium can not be closed-
loop
controlled. This means that in these systems only one condensation temperature
level is possible for all modes of operation:
WTHDY = constant
The conversion power PTHDY(t) in this thermodynamic pressure cylinder
conversion system can be varied by changes in the cycle frequency:
PTHDY(t) = 2* WTHDY * fCyc(t)
One possibility of making the cycle frequency fcyc to be variable consists in
varying the expansion velocity and, hence, the expansion duration tExp of a
piston
stroke by making the induction force Find to be variable through electrically
variable parameters of the linear generator.
The cycle frequency f,,c is dependent on the expansion duration tEp. When a
working cycle is immediately (without dead time) followed by the
contradirectional
working cycle, then the following applies:
fcyo = 1/(2* tExp)
CA 02714644 2010-08-10
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The expansion duration tEP is dependent on the stroke length, which however
is constant, and on the expansion velocity of the piston, which, in turn, is
the
result of the equilibrium of forces between the mechanical thrust Fstroke of
the
pressure cylinder during expansion and the opposed induction force Find of the
linear generator.
tE,p = f (Find)
and, hence: fcyc(t) = f (Find)
An electrically adjustable parameter of the linear generator is the coil
inductance, which can be varied, for example, through an electrically
selectable
wiring of coil pairs.
Another way of configuring the induction force Find of the linear generator to
be variable consists in a closed-loop control of the load current of the
inverter by
the input resistance of the inverter, for example. The special advantage of
this
configuration resides in that this interface, for example in the form of a
semiconductor junction, allows a very rapid and precise closed-loop control of
the
induction force Find also during the expansion phase. This, in turn, results
in that
the combination of pressure cylinder and linear generator can be optimized in
the
design of the dimensions since this allows an optimum operation to be realized
under the limiting factors of maximum acceleration and maximum piston
velocity.
The highest power throughput is produced when the piston is initially
constantly
accelerated at maximum acceleration during expansion. Once the maximum
permissible velocity of the piston is reached, the piston is moved at this
maximum
velocity until it is necessary to decelerate the piston again at a negative
and
constant maximum acceleration.
In this way, it is possible to provide a heating system having a variable
conversion power PTHDY(t) for all modes of operation; however, since it is not
possible to adjust the outlet pressure, the following applies here, too:
TKond= THeizk RL= TWs
11CARNOT - 1 - THeizk RL / THeiz
The technical implementation of such a conversion system, such as, for
example, a pressure cylinder, a uniflow steam engine, or a Corliss engine, is
CA 02714644 2010-08-10
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effected by means of a periodic valve timing. Each individual inlet valve and
outlet valve is opened and closed periodically at the cycle frequency fcy, for
a
time period as determined by the valve timing settings, as illustrated in
Figure 10,
the cycle duration tcyc corresponding to the sum of the duration of one
working
cycle tAus,l and one contradirectional working cycle tAus12:
tEinll = tEin12 = constant
tCyc = tAusll + tAusl2
fcyc = 1 / tcyc
tExp = 1l(2*fc c)
All of the valves are synchronized in time in that in its expansion phase, the
pressure cylinder periodically changes the valve position by the mechanical
motion of the pressure cylinder or a synchronized motion derived therefrom,
such
as a rotary motion, and in this way directly mechanically controls the closed
periods of each individual valve. The open periods for each valve are defined
by
the dimensions of a piston valve, for example, which opens and closes a valve
by
a linear motion. One example of a linear design of a periodically operating
conversion system having a double-acting pressure cylinder is the known steam
engine by James Watt.
A rotary type of this periodic pressure cylinder conversion system includes
separate rotary valves which are opened and closed synchronously with the
cycle
frequency fcy, for defined periods of time as illustrated in Figure 10. The
open
periods tEinl of the separate valves result from the angular dimensions of the
rotating valve segment in which a flow through the valve is possible. In
purely
mechanical systems, the cycle frequency fcyc is derived from the mechanical
motion of the pressure cylinder, which is converted to a rotary motion, such
as,
e.g., in the known Corliss engine. Another way of implementation is produced
by
obtaining the cycle frequency by means of an external control, e.g. using an
electric motor which rotates synchronously with the piston position. The
rotary
valves are synchronized in time in that, for example, all valves are connected
with
each other by a rotary spindle which rotates at the cycle frequency fcyc.
CA 02714644 2010-08-10
In order to realize a dynamic closed-loop control of the outlet pressure of
the
medium and, thus, of the condensation temperature TKond, the inlet volume per
stroke VE;n, needs to be adjustable, which is possible by way of a variable
open
period of the inlet valves tE;n,. Ideally, the inlet valves are externally
controlled, i.e.
a control unit sets the inlet volume VE;n,(t) by means of the inlet period
tEinl such
that the desired pressure of the medium is reached over the full piston stroke
upon completion of the expansion. The condensation temperature of the medium
is thereby set such that it corresponds to the maximum required temperature of
the heat consumers coupled.
Preferably, inlet valves that can be electrically driven are employed for this
purpose. In principle, the valve can also be driven pneumatically or
hydraulically.
Further conceivable is a solution in which the inlet valves are realized with
a
piston valve which opens and closes the inlet valves by its linear motion, the
linear motion of the piston valve being externally controlled, i.e. not being
derived
from the motion of the pressure cylinder. A controlled linear motion of the
piston
valve can be realized using a linear motor, for example.
One way of implementation is constituted by the valve-controlled double-
acting pressure cylinder illustrated in Figure 11, in which the piston of the
piston/
cylinder unit is moved by the working medium flowing into a working chamber of
the pressure cylinder. Following an evaluation of sensor data, the control
unit
automatically determines the inflow duration. The inlet volume to be
controlled is
therefore a function of the medium pressure available on the input side,
which,
however, can be considered to be constant, and the temperature desired on the
output side during condensation.
Since it is always the full piston stroke that is used for expansion, a direct
interrelation exists between the inlet period tE;n, and the desired
condensation
temperature TKond, i.e. for each adjustable condensation temperature TKond
there
exists a corresponding inlet period tE;n, and thus a constant value for the
work
performed by a piston stroke WTHDY. As a result, the following applies:
WTHDY = f (TKond)
This means that the inlet period tE;n, can not be made use of for controlling
work performed by a piston stroke WTHDY. The inlet period tE;n, can be
exclusively
CA 02714644 2010-08-10
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used for adjusting the outlet pressure of the medium after the expansion. The
conversion power PTHDY(t) in a thermodynamic pressure cylinder conversion
system can therefore be exclusively varied by varying the cycle frequency. The
conversion power PTHDY results from the product of the number of working
cycles
(stroke 1 and stroke 2) and the work performed by one piston stroke WTHDY and
the cycle frequency fcy,.:
F THDY(t) = 2* WTHDY(TKond) * fCyc(t)
This principle is, of course, also applicable when using two contradirectional
pressure cylinders, as are made use of in conventional free piston systems,
with
one working chamber always remaining unutilized and only one pressure cylinder
carrying out the working cycle at a time alternately, while the other one is
currently in the outlet phase.
Based on a conversion system implemented in this way, the cycle frequency
fcy, thus controls the conversion power PTHDY, while the condensation
temperature TKond is adjusted on the basis of the inlet period tEini.
The following results from this for the different modes of operation:
Mode of operation (a) PTHDY-Heizk = 2* WTHDY-Heizk * fCyc-Heizk = PHeiz - PSp
IN
when TKond _ THeizk RL
Mode of operation (b) PTHDY-Stromp = 2* WTHDY- Stromp * fcyc-Stromp = PHeiz -
Pws
when TKond = Tws
It is, however, technically complicated to configure the induction force of a
linear generator to be adjustable in order to use it for regulating the
conversion
power. A further advantage of the valve-controlled double-acting pressure
cylinder consists in that it is not necessary to immediately start with the
execution
of the next working cycle once a working cycle has been executed. By a
variable
dead time trot inserted between execution of the working cycles, the
repetition
frequency and thus the conversion power PTHDY can be controlled. The cycle
frequency fcy, is dependent on the expansion duration tExp and the dead time
trot:
f c y c = 1 /(2* (tExp +ttot))
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For the required capacity (power) adaptation, the control unit determines the
appropriate cycle frequency fcy, in the different modes of operation:
fCyc - PTHDY / 2* WTHDY
Here, the control unit waits between execution of one working cycle and
execution of the contradirectional working cycle until half the period
duration Tcyc
has elapsed. A power-modulated valve control takes place here, as illustrated
in
Figure 12. The dead times are compensated by the filter and rectifier unit
almost
without loss.
In the process, the outlet valves are alternately opened and closed after half
the period duration Tcy, that is, synchronously with the cycle frequency fcyc.
It is
therefore feasible to design the outlet valves to be externally controlled,
such as,
e.g., by electrically drivable valves, and also by a control derived from the
linear
motion of the pressure cylinder, such as, e.g., by means of a rotary valve
control
that is synchronous with the piston position.
Basically, however, a generation of electricity is also possible using a valve-
controlled rotational conversion system coupled to the thermodynamic cycle,
such as a compressed air motor specially matched therewith, in which the
linear
piston movement is first converted to rotational energy by means of a
crankshaft,
the rotational energy then being converted to electrical energy by means of a
generator likewise specially adapted to this application.
A further preferred option is offered by the use of a rotary piston machine,
in
particular a DiPietro engine as such, in which the inlet volume per working
cycle
can be likewise controlled. An RMT generator, primarily designed for wind
power
plants, presents itself for use as a rotational generator. Both components
distinguish themselves by a high efficiency in conversion as well as by very
low
start-up and switch-off losses in the required capacity range, even at low
rotational speeds.
The electrical voltage produced in the generator in all of the systems
described may, of course, also be used for other purposes. Instead of
generating
a line voltage, it is possible to generate battery charging voltages using a
suitable
converter, e.g. for lithium ion batteries for electric vehicles, or voltages
suitable to
be used for obtaining hydrogen through electrolysis. The kinetic energy
produced
CA 02714644 2010-08-10
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by the conversion system may also be used for other purposes, e.g. for cooling
indoor air by means of a refrigerating machine.
In a combustion plant involving output temperatures of TH out> 300 C, it is
technically difficult to reach the low waste gas temperatures required for an
efficient operation. A marked improvement according to the invention in the
efficiency of the combustion system is achieved by the thermal interconnection
of
a waste gas heat recovery system in a function as a separate heat generator
for
the thermal heat energy ERuck(t) recovered having the temperature level TRack.
The equilibrium between thermal energy generation and thermal energy
demand is periodically determined and adjusted here by the control unit
preferably according to the following formula:
EHeiz(t) + ESp OUT(t) + ERuck(t) = EWW (t) + EHw (t) + ETHDY(t) + ESp IN(t) +
EResf(t)
For one thing, the waste gas residual heat can be made use of for meeting
the heating and VVW demand, the following applying:
ERUck(t) = Eww (t) + EHW (t)
Figure 8 illustrates one possible technical realization of this thermal
interconnection by means of the heat accumulator. The disadvantage of this
arrangement resides in that Evwv (t) + EHW (t) are variable, whereas the
quantity of
heat recovered is always obtained constantly as soon as the heating system is
in
operation. The thermal equalization can only be effected when there is a
heating
demand.
Therefore, a further improvement in accordance with the invention is the use
of the waste gas residual heat for producing electricity in the thermodynamic
cycle, that is, in the modes of operation (a) and (b), the following applying:
ETHDY(t) = ERUck(t) + EHeiz(t)
By a thermal coupling of thermal solar collectors either directly to a heat
consumer or preferably to the heat accumulator, the annual heating costs may
be
reduced. The equilibrium between thermal energy generation and thermal energy
demand is periodically determined and adjusted here by the control unit
preferably according to the following formula:
CA 02714644 2010-08-10
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EHeiz(t) + Es01(t) + EsP OUT(t) + ERuck(t) = EWW (t) + EHW (t) + ETHDY(t) +
EsP IN(t) +
ERest(t)
An optimum energy utilization is obtained by a thermal interconnection,
according to the invention, of the individual components of the heating
system,
which ensures that each heat generator is in a heat exchanging relationship
with
each heat consumer, the heat accumulator, or with any other heat generator,
with
provision being preferably made for a contradirectional heat transfer when
different heat transfer media are involved, and preferably for an exchange of
medium when identical heat transfer media are involved.
Furthermore, the heating system according to the invention may be
selectively operated in a plurality of modes of operation. In a first mode of
operation, the heat generated or accumulated by one or more heat generators is
used for heating or for filling the heat accumulators. In a second mode of
operation, the heat generated is supplied to the thermodynamic cycle for the
production of electricity, the residual heat arising from the thermodynamic
cycle
being transferred to the heat sink. In a third mode of operation, the heat
generated is supplied to the thermodynamic cycle for the production of
electricity,
the residual heat arising from the thermodynamic cycle being used for heating
or
for filling the heat accumulators. On the basis of predefined criteria, the
control
unit automatically determines in which one of the modes of operation the
heating
system is operated and, to this end, can optionally obtain information from an
electricity supplier of the property to allow a production of electricity in
especially
profitable periods of time.
This heating system is able to effectively exploit solar energy, both for the
production of electricity and for obtaining thermal heat, by further raising
the low
temperature level prevailing in the heat accumulator or in the solar
collector,
which must only be higher than the temperature of the heat sink (Tws), by the
remaining temperature range up to a consumption-dependent target temperature.
Further advantages arise in that, in one mode of operation of the heating
system, in particular during the night or in winter, the solar collectors are
made
use of as a heat sink which absorbs the residual heat of the thermodynamic
cycle. A multistage solar collector structure is of advantage here, which
includes
a series connection of different types of collectors consisting, on the one
hand, of
CA 02714644 2010-08-10
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cost-effective collectors having a lower thermal insulation and, on the other
hand,
of higher-quality collectors having a high thermal insulation. For the purpose
of
energy optimization, it is further of advantage in some modes of operation
that
the individual collector types can also be bypassed, i.e. the solar medium
does
not flow through them. Based on predefined criteria, such as, e.g., the
outside
temperature, the control unit here determines whether the solar medium flows
through only one of the collector types or through both in series.
In addition, radiators or a floor heating system provided in the property may
be utilized as a permanent heat sink for the thermodynamic cycle, even when
there is no heating demand. A special radiator in the laundry room, which is
heated with residual heat whenever the latter develops during the exclusive
production of electricity, could at the same time be utilized for laundry
drying, for
example.
As a rule, a solar-assisted heating system shows an inverse ratio between the
availability of solar primary energy and the heating demand, i.e. while a
large
amount of primary energy is available in summer, there is hardly any or only
little
heating demand, whereas the opposite applies in winter. The invention makes
use of exactly this inverse ratio, to the effect that the surplus of primary
energy is
converted into electrical energy. Due to a multiple dual use of the resources
of
the components which are already present in the solar-assisted heating system,
of the solar collectors, heat accumulators, heating system and radiators, only
the
prime costs of the conversion system plus worthwhile add-ons such as
additional
collector surfaces and additional accumulator volume have to be incurred for
solar electricity production. A high overall system utilization of the cost-
intensive
collector surface is advantageously achieved as there is no excess supply of
solar heat energy in summer any more and in winter the solar supply is
utilized
via the heating system.
Due to the weak points as initially described of the circuit media currently
available, the system presented so far, which is based on a thermodynamic
process for electricity generation, is however not able to cover the desirable
high
temperature range which is given, on the one hand, by the high flash point of
a
heating system (> 1000 C) and, on the other hand, by the ambient temperature
(< 0 C) of theoretically available temperature potentials.
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A marked improvement according to the invention is therefore constituted by
the combination of two thermodynamic cycles (partial processes) for successive
temperature ranges, each partial process being a separate independent
thermodynamic process and each partial process having a conversion system of
its own for the conversion of pressure to electrical energy, and the
condensation
heat of the partial process for the higher temperature range being used as
vaporization heat for the partial process of the lower temperature range by
means
of an interconnection via a heat exchanger. For example, a steam, butyl
benzene, propyl benzene, ethyl benzene, toluene or OMTS cycle may be used
for the temperature range of from 300 to 150 C and an ORC cycle using the
R245fa medium may be used for the low temperature range of from 150 to 15 C.
The resultant addition of the temperature ranges results in a theoretical
Carnot
efficiency of 50 % in this example.
The equilibrium between thermal energy generation and thermal energy
demand is periodically determined and adjusted here by the control unit
preferably according to the following formula:
EHefz(t) + Es0 (t) + Esp OUT(t) _
Eww (t) + EHw (t) + ETHDY1(t) + ETHDY2(t) + Esp IN(t) + ERest(t)
A further improvement according to the invention appears if the necessary
capacity compensation between the partial processes occurs in that the control
unit controls the transition temperature between the condensation of the
medium
of the first partial process and the vaporization of the medium of the second
partial process and the capacity ratio of the two partial processes and
adjusts it in
accordance with the requirements.
A further aspect according to the invention is a cost-effective coupling of
individual components of the two conversion systems for the conversion of
pressure into electrical energy, so that it is not required to provide all
individual
components twice, by means of a mechanical coupling of the conversion systems
which is configured such that the mechanical forces add, so that only one
generator and one grid-based frequency converter are required, each of which
transfers the sum of the energy of the partial processes.
CA 02714644 2010-08-10
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A further possible cost-effective coupling of individual components of the two
conversion systems for the conversion of pressure into electrical energy, so
that it
is not necessary to provide all individual components twice, can be
implemented
by means of an electrical coupling of the generator outputs; as a result, only
one
grid-based frequency converter is required, which transfers the sum of the
energy
of the partial processes.
In principle, it is also possible to couple the pressure cylinders of the two
conversion systems for the partial processes by means of a crankshaft, the
generation of electricity being effected by way of a rotational generator.
Of particular advantage here is the coupling of a waste gas heat recovery
system and a thermal solar plant to the low temperature circuit of the two-
stage
thermodynamic process. The energy supply ETHDY is effected here in two stages
at different temperature levels. In the low temperature stage (stage 2), the
thermal energy ERuck recovered is made use of for heating or partial
vaporization
of the thermodynamic medium up to the temperature level TRUck, the following
applying:
ETHDY2(t) ' Eso1(t) + ERuck(t) + ERestl(t)
This means that owing to the different temperature levels, the amount of
energy for conversion into electrical energy ETHDY_Sta9e2 and thus ETHDY
additively
increases by the value of the waste gas heat ERUck(t) recovered and the solar
energy Esol(t).
In the first stage of the thermodynamic process, the thermal energy EHelz
recovered is made use of only for residual vaporization of the thermodynamic
medium from the temperature level TRuck up to the temperature level THeiz, the
following applying:
ETHDYI(t) = EHeiz(t) - ERestl(t)
By means of sensors for detecting process-influencing parameters, the
control unit independently sets one or more of the modes of operation
characterized below:
(a) Mode of operation "Heating, WW and production of electricity"
CA 02714644 2010-08-10
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Function Energy transmission Temperature levels and
preferred temperature ranges
Heating, WW heating, EHeiz = ETHDY1 + EResti TBren = TTHDY1-In = 300 C
and THDY production of
ETHDY2 = ERuck + EResti TTHDYI-out= TTHDY2-In = 150 C
electricity
Fig. 19 Esp IN = ERest2 THK VL =Tsp in = TTHDY2-out = Tww =
TKond = TH In= 45..85 C
Esp OUT = EHW + Eww
THK RL = Tsp out = THeiz Ab = 20..60 C
THeiz Ruck = THeiz Mit = 100..140 C
(b) Mode of operation "Exclusive production of electricity from thermal heat"
Function Energy transmission Temperature levels and
preferred temperature ranges
THDY production of EHeiz = ETHDY1 + EResti Teren = TTHDYI-In = 300 C
electricity from thermal
ETHDY2 = ERuck + EResti TTHDYI-Out= TTHDY2-In = 150 C
heat
ERest2 = Ew5 TTHDY2-out= Tws = THeiz Ab = 15..25 C
Fig. 20
Heiz Ruck = THeiz Mit = 100.. 140 C
(c) Mode of operation "Exclusive production of electricity from thermal heat
and accumulated or direct solar energy"
Function Energy transmission Temperature levels and
preferred temperature ranges
THDY production of EHeiz = ETHDY1 + EResti Tsp out = TH In = 20..60 C
electricity from thermal
ETHDY2 = Teren = TTHDYI-In = 300 C
heat and heat
accumulator and solar Esp out + ERuck + EResti TTHDYI-out= TTHDY2-In = 150 C
energy ERest2 = EM TTHDY2-out= Tw5 = Tsp in =
Fig. 21
15..25 C
THeiz Ab = Tsp Out = TKoI out = 20..60 C
THeiz Rock = THeiz Mit = 100..140 C
CA 02714644 2010-08-10
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(d) Mode of operation "Filling solar energy reservoir"
Function Energy transmission Temperature levels and
preferred temperature ranges
Filling solar energy EsP in = Esoi TsP in = TKOs out = 40..90 C
reservoir
TsP out = TKol in = 20..40 C
Fig. 22
(e) Mode of operation "Solar heating and WW'
Function Energy transmission Temperature levels and
preferred temperature ranges
Solar heating and WW Esa OUT = EHW + Eww THK VL = TsP in = TKoI out= Tww
by means of heat
EsP In = Eso, = 45..90 C
accumulator
Fig. 23 THK RL = TSP out = TKoI In = 20..50 C
In connection with the temperatures indicated above, an ideal situation
without losses in the thermal transmission is assumed in which the control
unit
adjusts the operation at the respectively most favorable temperature spreads.
It is possible, of course, to establish further modes of operation from the
above tables by combining several modes of operation or by omitting a
generating unit, accumulator or consumer in some modes of operation; these
further modes of operation, however, shall not be discussed in further detail
here.
How the heating system is operated depends on the current situation. As a
rule, the production of heat energy is more efficient than the production of
electricity. But when selecting the operating mode, the control unit also
takes into
account, inter alia, the supply of primary energy, the (predicted) demand for
heat
energy, the time-dependent degree of utilization of the heat accumulator, and
the
ratio between the income for electrical power fed and the effective heating
costs.
The control unit provides for an energy management for a situation-based
distribution of energy in consideration of determined and predicted process-
influencing parameters.
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According to one aspect of the invention, provision is also made for a
sequence of different modes of operation which, owing to the resultant high
and
constant utilization of the heating system accompanied by a simultaneous
effective production of electricity, is advantageous whenever the heating and
WW
energy demand is lower than the maximum heating capacity of the heating
system installed. In accordance with such a sequence of modes of operation,
alternately the first the mode of operation (a), "Heating, WW and production
of
electricity", is active until such time as the heat accumulator is filled
sufficiently,
and then, after this condition is met, parallelly the modes of operation (b),
"Exclusive production of electricity from thermal heat", and (e), "Solar
heating and
WW by means of heat accumulator", until such time as the amount of heat
accumulated in the heat accumulator falls below a lower threshold.
To be able to operate the system in all modes of operation, the power
throughput PTHDYI(t) and PTHDY2(t) of the conversion systems 116 and 118 must
be adjustable for each mode of operation, the following applying to each
relevant
mode of operation:
(a) Mode of operation "Heating, WW and production of electricity" at TKond2
_ THeizk RL
PHeiz = PTHDYI
PTHDY2 = PRiick + PRest1
(b) Mode of operation "Exclusive production of electricity from thermal heat"
at TKond2- TWs
PHeiz = PTHDYI
PTHDY2 - PRuck + PResti
(c) "Exclusive production of electricity from thermal heat and accumulated
or direct solar energy"
PHeiz - PTHDY1
PTHDY2 = PSP Out + PRuck + PRest1
CA 02714644 2010-08-10
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Since the condensation temperature of the second stage TKdnd2 is different in
the various operating modes, it is advantageous to provide the second stage
with
a conversion system which has an outlet pressure that can be regulated, such
as,
for example, the valve-controlled linear generator described above or a
DiPietro
engine.
Since the condensation temperature of the first stage TKdnd2 is constant in
the
various operating modes, it is advantageous to provide the first stage with a
conversion system without an outlet pressure that can be regulated, such as,
for
example, a uniflow steam engine or a turbine.
Based on a modified configuration (see Figure 24), a technical
implementation of all modes of operation is possible in which the second stage
includes a conversion system without an outlet pressure that can be regulated,
such as, for example, a uniflow steam engine or a turbine. This is made
possible
in that the heating system is realized to have a mode of operation (a) in
which
only the first stage produces electricity. In the second stage, only thermal
heat is
produced in this mode of operation in that the thermodynamic low temperature
circuit medium does not flow through the conversion system of the second stage
in this mode of operation.
The mode of operation (a) modified thereby is characterized by the following
features:
(a) Mode of operation "Heating, WW and production of electricity"
Function Energy transmission Temperature levels and
preferred temperature ranges
Heating, WW heating, EHeiz = ETHDY1 TBren = TTHDYI-In = 300 C
nd THDY production of
electricity ETHDY2 = TTHDY1-Out= TTHDY2-In =T5p In = 1 50 C
ERUck + ERest1
Fig. 19 THK VL = TWw = TKond = TH In=
E5p IN = ETHDY2 45..85 C
E5p OUT = EH'w + EWw THK RL = Tsp Out = THeiz Ab = TTHDY2-Out
= 20..60 C
THeiz Rick = THeiz Mit = 100..140 C
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Further general increases in efficiency for all system structures presented
are
obtained, for one thing, based on the fact that internal heat exchangers
(regenerators) are provided for the thermodynamic cycle.
For another thing, it is often difficult in hot summer nights to reach cooling
temperatures below the desirable 15 C. One cost-effective solution is
constituted
here by a sprinkler system which cools down solar collectors additionally,
inter
alia by the evaporative heat loss produced in the process. This sprinkler
system
should, of course, be activated by the control unit only when, all in all,
cost
benefits are expected to result thereby.
It is furthermore conceivable that the conversion system for the high
temperature circuit 402 is realized by means of a Stirling engine since
Stirling
engines are designed for higher temperatures. It would be theoretically
possible
in this way to produce electrical energy at a high overall efficiency with
burner
circuit temperatures of > 500 C.
Further details of the invention will be apparent from the following
description
with reference to the accompanying drawings, in which:
- Figure 1 shows a schematic illustration of the thermal interconnections of
all components involved and the associated functions of the intelligent energy
distribution management of the heating system according to the invention;
- Figure 2 shows a technical realization of the heating system according to
the invention:
- Figure 3 shows a schematic illustration of a combined condenser;
- Figure 4 shows a cost-effective realization of the heating system according
to the invention;
- Figure 5 shows the mode of operation "Heating, WW and production of
Electricity";
- Figure 6 shows the mode of operation "Exclusive production of electricity
from thermal heat";
- Figure 7 shows a technical realization of the heating system according to
the invention using waste gas heat recirculation coupled to the heat
accumulator;
CA 02714644 2010-08-10
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- Figure 8 shows a technical realization of the heating system according to
the invention using waste gas heat recirculation coupled to the thermodynamic
process;
- Figure 9 shows a schematic illustration of a possible linear conversion
system for the conversion of thermodynamic into electrical energy;
- Figure 10 shows a schematic illustration of a periodic valve timing;
- Figure 11 shows a schematic illustration of a valve-controlled double-acting
pressure cylinder;
- Figure 12 shows a schematic illustration of a power-modulated valve timing;
- Figure 13 shows a schematic illustration of a possible rotational conversion
system for the conversion of thermodynamic energy into electrical energy;
- Figure 14 shows a schematic illustration of a double-stage thermodynamic
cycle;
- Figure 15 shows a schematic illustration of a mechanical coupling of the
conversion systems for converting pressure energy into kinetic energy;
- Figure 16 shows a schematic illustration of an electrical coupling of the
generator outputs;
- Figure 17 shows a technical realization of a solar collector circuit;
- Figure 18 shows a technical realization of a double-stage design using solar
collectors and waste gas heat recirculation in the THDY circuit;
- Figure 19 shows the mode of operation "Heating, WW and production of
electricity";
- Figure 20 shows the mode of operation "Exclusive production of electricity
from thermal heat";
- Figure 21 shows the mode of operation "Exclusive production of electricity
from thermal heat and accumulated or direct solar energy";
- Figure 22 shows the mode of operation "Filling solar energy reservoir";
- Figure 23 shows the mode of operation "Solar heating and WW';
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- Figure 24 shows a modified technical realization of a double-stage design
using solar collectors and waste gas heat recirculation of a condensation
temperature in the THDY circuit;
- Figure 25 shows the modified mode of operation "Exclusive production of
electricity from thermal heat".
Figure 1 generally indicates the individual components of a heating system
according to the invention and their thermal interconnection 5 according to
the
invention: the heat generators 1, comprising a conventional heating system 2
and
optional solar collectors 3, an optional heat accumulator and/or cold
reservoir 4, a
heat sink 6, heat consumers 7, comprising an apparatus for providing hot water
8, a thermal heat circuit 9 and a thermodynamic cycle 10 which, by means of a
conversion system 11. is used for converting thermodynamic energy to
electrical
energy for the production of electricity. A central control unit 12 controls
the
operation of this heating system and of its individual components. The control
unit incorporates process-influencing control parameters which are
continuously
detected by suitable sensors 13 and are supplied to the control unit 12. On
the
basis of the parameters detected and/or specific assumptions, the control unit
12
is also able to estimate or predict (other) parameters which are relevant for
the
control process of the heating system.
Figure 2 illustrates the schematic structure of a mini CHP unit according to
the
invention, having a burner circuit 70 which flows through the heating boiler
of a
combustion system 71, a thermodynamic circuit 74 that is used for generating
electricity, a heating circuit 79 which flows through the radiators 80, and a
cooling
circuit 77 which transports waste heat to a heat sink, the burner circuit 70
flowing
through the vaporizer 73 of the thermodynamic circuit 74 and, depending on the
mode of operation, either the heating circuit 79 or the cooling circuit 77
flowing
through two separate condensers 75 and 76 on the output side. A heat
accumulator 81 is thermally coupled to the heating circuit 79 by means of a
heat
exchanger.
According to Figure 3, the separate condensers 210 and 211 are combined in
a cost-effective manner in a combined heat exchanger, each having separate
inputs and outputs for the thermodynamic circuit 200, the collector circuit
201,
and the heating circuit 202.
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Figure 4 illustrates the schematic structure of a further mini CHP unit
according to the invention, which is more cost-effective to produce owing to a
dual function of some components. For instance, the boiler of the combustion
system 331, through which the medium of the thermodynamic cycle 330 flows, is
at the same time the vaporizer of the thermodynamic cycle 330. The heat
accumulator 332 can be selectively used as a thermal heat sink of the
thermodynamic cycle by the condenser 333 being integrated in a cost-effective
manner in the heat accumulator 332. In the same way, the heating circuit may
be
made indirect use of in a cost-effective manner as a thermal heat sink of the
thermodynamic cycle in that it receives the required thermal heat by means of
a
heat exchanger 334 integrated in the heat accumulator 332.
Figure 5 describes the components and temperature levels included in the
overall structure according to Figure 4, which are required for the mode of
operation "Heating, VWV and production of electricity".
Figure 6 describes the components and temperature levels included in the
overall structure according to Figure 4, which are required for the mode of
operation "Exclusive production of electricity from thermal heat".
Figure 7 illustrates the schematic structure of a further possible mini CHP
unit,
including a waste gas heat recirculation 338 which is coupled to a heat
accumulator 340 by means of a heat exchanger 339.
Figure 8 illustrates the schematic structure of a further possible mini CHP
unit,
including a waste gas heat recirculation 350 which is coupled to the
thermodynamic circuit medium 352 by means of a heat exchanger 351.
The system illustrated in Figure 9 comprises a thermodynamic part 501
having a working medium, one or more pressure cylinders 502, a linear
generator
503 including a magnet and a coil, a control unit 506 which acts on both parts
and is part of the central control unit 12, a rectifier and filter unit 504
converting
the voltage pulses generated by the movement of the magnet to a DC voltage,
and an inverter 505 inverting the DC voltage to an AC voltage suitable for
feeding
into the grid. The condensation heat of the thermodynamic process is supplied
to
the heat consumers.
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Figure 10 shows a schematic illustration of a periodic valve timing in which
each individual inlet valve and outlet valve is opened and closed periodically
at
the cycle frequency fcy, for a time period as defined by the valve timing
settings,
the cycle duration tcyc corresponding to the sum of the duration of one
working
cycle tAusll and one contradirectional working cycle tAus12=
Figure 11 illustrates a valve-controlled pressure cylinder in which the two
working cycles are completely independent of each other (in particular in
terms of
time); this means that no predefined periodic sequence of cycles is provided
as
is the case in known multiple stroke engines. Rather, an individual working
cycle
is initiated depending on the situation, i.e. the control unit 609 provides
for the
performance of a working cycle by opening and, respectively, closing the ports
605; 606, 607, 608 only if specific criteria are fulfilled (in particular a
sufficient
pressure of the working medium). The four ports 605, 606, 607, 608 coupling
the
lines 601, 602 to the working chambers 603, 604 can be selectively opened or
closed by the control unit 609.
The expanding working medium flows through the first line 601 into the first
working chamber 603 of the pressure cylinder 600. To this end, the control
unit
609 opens the port 605 and closes the port 606. At the same time, the control
unit 609 closes the port 608 of the second line and opens the port 607. This
results in a force Fstroke being exerted on the piston 608, causing the piston
608 to
move to the right (according to the illustration in the Figure), accompanied
by a
performance of work. This process, which terminates after one stroke of the
piston 608, constitutes a "normal" working cycle of the pressure cylinder.
In the contradirectional working cycle, the control unit 609 closes the open
ports 606, 607 and opens the closed ports 605, 608, so that an oppositely
directed piston force - Fstroke and a movement of the piston 608 to the left
are
produced. It depends on the current position of the piston 26 which one of the
two working cycles (normal or contradirectional) is carried out.
The volume (inlet volume) flowing into the working chambers 603 and 604,
respectively, is controlled by means of the control unit 609. Upon an
evaluation
of sensor data 610, the start and duration of the inflow process are
determined
automatically, and the pressure and, hence, the temperature of the medium
after
the expansion are adjusted thereby such that this temperature corresponds to
the
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maximum required temperature of the heat consumers coupled. That is, the inlet
volume is a function of the medium pressure available on the input side and
the
pressure desired on the output side during condensation, which allows a very
efficient energy conversion.
As already mentioned, the control/closed-loop control of the individual
circuit
processes and of the linear generator is performed taking process-influencing
parameters into consideration (thermal energy supply, thermal heating demand,
pressure and temperature of the working medium, the heat accumulators, and
the surroundings, etc.), which are provided by a large number of suitable
sensors
610 (pressure, temperature sensors, etc.)
This principle is, of course, also applicable when using two contradirectional
pressure cylinders, as are made use of in conventional free piston systems; in
this case, the working chamber 304 remains unutilized and only one pressure
cylinder carries out the working cycle at a time alternately while the other
one is
in the outlet phase.
Figure 12 illustrates a schematic view of a power-modulated valve timing, in
which, after one working cycle is completed, execution of the next working
cycle
is not started immediately. By means of insertion of a variable dead time trot
between execution of the working cycles, the repetition frequency and thus the
conversion power PTHDY can be controlled. The cycle frequency fcy, is
dependent
on the expansion duration tExp and the dead time trot: Here, the control unit
waits
from execution of one working cycle till execution of the contradirectional
working
cycle until half the period duration Tcyc has elapsed. Hence, a power
modulation
on the output voltage generated takes place, the dead times being compensated
by the filter and rectifier unit almost without loss. In the process, the
outlet valves
are alternately opened and closed after half the period duration Tcyc, that
is,
synchronously with the cycle frequency fcy,.
Figure 13 illustrates an alternative rotational conversion system which may be
employed in place of the linear conversion system described above. The
rotational conversion system is coupled to the thermodynamic cycle 701 in
which
the available thermal energy (heat energy) is first converted into
thermodynamic
energy (steam pressure). The steam pressure is then converted into rotational
energy by means of a valve-controlled expansion engine 702, such as, e.g., a
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rotary piston engine (in particular a DiPietro engine), the control unit 705
here
likewise adjusting the inlet volume of each individual working cycle by means
of
the inlet and outlet valves such that the pressure and, hence, the temperature
of
the medium after the expansion corresponds to the maximum required
temperature of the heat consumers coupled. The rotational energy is converted
into electrical energy by means of the generator 703, the electrical energy
being
finally converted to AC current by a grid-based frequency converter 704 for
feeding into the grid. The control unit 705 incorporates process-influencing
control parameters which are continuously detected by suitable sensors 706 and
supplied to the control unit 705 (part of the central control unit 12).
Figure 14 describes a double-stage thermodynamic process which consists of
two partial processes 400 and 401 for successive temperature ranges. Each
partial process is a separate independent thermodynamic process with a medium
suitable for the allocated temperature range. Each partial process includes a
separate conversion system for converting pressure to electrical energy 402
and
403. The condensation heat of the partial process for the higher temperature
range 400 is used as vaporization heat for the partial process of the lower
temperature range 401 by means of an interconnection via a heat exchanger
404.
Figure 15 describes possible cost-effective solutions - one for a linear
system
(Figure 15a) and one for a rotational system (Figure 15b) - of how to avoid
having
to provide a double configuration of all individual components of the two
conversion systems for the conversion of pressure into electrical energy that
are
required in double-stage thermodynamic processes. This is implemented by the
mechanical couplings as illustrated of the conversion systems for the
conversion
of pressure energy into kinetic energy 451 and 452, which are realized such
that
the mechanical forces appearing in the conversion of the pressure energy into
kinetic energy add up vectorially by acting into the same direction
isochronously
as closed-loop controlled by the control unit. As a result, only one generator
453
and one grid-based frequency converter 454 are required, which each transfer
the sum of the energies of the partial processes.
Figure 16 describes a further cost-effective solution how it can be avoided
having to provide a double configuration of all individual components of the
two
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conversion systems for the conversion of pressure into electrical energy that
are
required in a double-stage thermodynamic process. By means of a suitable
electrical coupling 462 of the generator outputs 460 and 461, which is
realized
such that the different voltage potentials generated by the two generators are
supplied to the input of the grid-based frequency converter 463 without short
circuits occurring between the generators, it is achieved that both voltage
potentials serve as an energy reservoir for the grid-based frequency converter
463, for the conversion to a grid-compatible AC voltage. The result of this is
that
only one grid-based frequency converter 463 is required, which transfers the
sum
of the energy of the partial processes.
Figure 17 is a schematic illustration of a multistage solar collector
structure
which includes a series connection of collectors of lower thermal insulation
50
and higher thermal insulation 51. In addition, each of the types of collectors
can
also be bypassed, i.e. the solar medium does not flow through it. Based on
sensor data, such as, e.g., the ambient or collector temperature, and on the
currently intended purpose of use of the collectors as heat generators or as a
heat sink, the control unit 12 determines whether the solar medium flows
through
only one of the collector types or through both in series.
Figure 18 shows a schematic illustration of a double-stage configuration
including solar collectors and a waste gas heat recirculation in the THDY
circuit,
essentially comprised of a burner circuit 100, a thermodynamic high
temperature
circuit 101, a thermodynamic low temperature circuit 102, a heating circuit
117, a
solar circuit 103, a WW circuit 104, and a cooling circuit 105. The burner
circuit
100 flows through the heating boiler of a combustion system 106 and is coupled
to a thermodynamic high temperature circuit 101 by means of a heat exchanger
107. The solar energy Eso,(t) accumulated in the heat accumulator 115 is used
for heating the thermodynamic medium up to the temperature level Tsp out by
the
low temperature circuit 102 being thermally interconnected to the heat
accumulator 115 by means of a heat exchanger 112, the heat exchanger 112
having a dual function: in one mode of operation it serves for heating the
thermodynamic medium up to the temperature level T5 out, and in another mode
of operation it serves as a condenser for transferring the condensation heat
of the
low temperature circuit 102 to the accumulator medium. The heat energy ERuCk
recovered is used for heating or partial vaporization of the thermodynamic
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medium from the temperature level Tsp out up to the temperature level TROck in
that
the low temperature circuit is thermally interconnected to the waste gas heat
recovery 110 by means of a heat exchanger 111. In one mode of operation, the
residual heat of the low temperature circuit ERest-stufe2(t) is transferred to
the
cooling circuit 105 by means of a condenser 109. The thermal coupling of a
solar
collector circuit 103 to the heat accumulator 115 is performed by means of a
heat
exchanger 113. The thermal coupling of a heat accumulator 115 to the WW
circuit 104 is performed by means of a heat exchanger 114.
Figure 19 describes the components and temperature levels involved in the
overall structure according to Figure 18 which are required for the mode of
operation "Heating, WW and production of electricity".
Figure 20 describes the components and temperature levels involved in the
overall structure according to Figure 18 which are required for the mode of
operation "Exclusive production of electricity from thermal heat".
Figure 21 describes the components and temperature levels involved in the
overall structure according to Figure 18 which are required for the mode of
operation "Exclusive production of electricity from thermal heat and
accumulated
or direct solar energy". Rather than the solar collectors, other thermal
energy
sources may, in principle, also be made use of, e.g., district heating may be
utilized. This does not affect the basic functional principle of the heating
system
according to the invention.
Figure 22 describes the components and temperature levels involved in the
overall structure according to Figure 18 which are required for the mode of
operation "Filling solar energy reservoir".
Figure 23 describes the components and temperature levels involved in the
overall structure according to Figure 18 which are required for the mode of
operation "Solar heating and WW'.
Figure 24 is a schematic illustration of a modified realization according to
Figure 18, in which the second stage includes a conversion system without an
outlet pressure that can be regulated, such as, for example, a uniflow steam
engine or a turbine. This is allowed in that the heating system is implemented
to
have a mode of operation (a) in which only the first stage produces
electricity and
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the second stage in this mode of operation is only used for producing thermal
heat in that the thermodynamic low temperature circuit medium does not flow
through the conversion system of the second stage in this mode of operation.
Figure 25 describes the components and temperature levels involved in the
overall structure according to Figure 24 which are required for the modified
mode
of operation "Heating, WW and production of electricity".
The invention has been described with reference to several exemplary
embodiments. It is, of course, apparent to a person skilled in the art that
modifications may be made without leaving the idea of the invention. In
addition,
the exemplary embodiments illustrated are of a sketch-like nature. Any missing
details are not relevant to the essence of the invention, but may be added by
a
person skilled in the art.
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List of terms used and their meanings
Conventional heating Heating installation on the basis of fuel oil, gas,
system coal, electrical energy, wood logs or wooden
pellets, wood gasification plant, biomass
combustion plant, ...
Heat generator Thermal heat source, e.g. conventional heating
system, solar thermal process, process waste heat
(such as the residual heat in biogas production), ...
Heat consumer Radiator, WW consumer, and thermodynamic
process
Heat accumulator or cold Buffer vessel, latent heat accumulator,
reservoir thermochemical accumulator, ...
Heat sink Deep-water geothermal probe, geothermal
collector, body of water (pond, pool, rain water or
domestic service water, river, ... ), air-cooled heat
exchangers with or without ventilators, air-cooled
solar collectors, accumulated environmental cold
energy, heating system return flow installations or
in-floor heating system return flow installations,
evaporative heat loss, ...
Thermodynamic process ORC process with one cooling agent or a mixture
of several cooling agents, thermal oils, hydraulic
oils, gases; Kalina process; water vapor process; ...
Generator Asynchronous generator, synchronous generator,
RMT generator, ...
Grid-based frequency Rectifiers or AC converters, frequency changers, ...
converters
Sensors For the purpose of measuring pressure,
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temperature, flow rates, solar radiation, filling level,
piston position or rotational frequency, ...
Expansion engine Pressure motor, turbine, DiPietro engine, steam-
powered screw-type engine, ...
Radiator Radiator for a residential property, in-floor heating
system, wall heating system, ...
WW consumer WW-domestic service water, dishwasher, washing
machine, ...
Solar collector Flat plate collector, tube collector, parabolic trough
collector, parabolic mirror collector, ...
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List of abbreviations
BHKW Combined heat and power unit (CHP unit)
EHeiz Thermal energy generated by the conventional heating system
Et.1 Energy demand for thermal heat
EKM-Ab Waste heat arising in a refrigerating machine
EKUhI Energy required for indoor cooling
ERest Condensation heat energy (process anergy)
ERest1 Condensation heat energy of the first stage of the thermodynamic
process
ERest2 Condensation heat energy of the second stage of the
thermodynamic process
ERUCk Waste gas heat recovered
Eso, Thermal solar energy
ESpIN Thermal energy to be accumulated
Esp OUT Thermal energy to be taken from the heat accumulator
ETHDY Energy of the thermodynamic process for the conversion into
electrical energy (process exergy)
ETHDY1 Energy of the first stage (high temperature stage) of the
thermodynamic process for the conversion into electrical energy
(process exergy)
ETHDY2 Energy of the second stage (high temperature stage) of the
thermodynamic process for the conversion into electrical energy
(process exergy)
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Ewq Thermal energy supply of the heat source
Eww Energy demand for domestic service water
fly. Cycle frequency
Find Induction force of the generator
KW Cold water
PHeiz Thermal heating power of the conventional heating system (heat
flow)
PHeiz- Heiz Solar Thermal heating power of the conventional heating system in
the
mode of operation (c), "Exclusive production of electricity from
thermal heat and accumulated or direct solar energy"
PHeiz- Heizk Thermal heating power of the conventional heating system in the
mode of operation (a), "Heating, WW and production of electricity"
PHeiz- Solar Thermal heating power of the conventional heating system in the
mode of operation (d), "Filling solar energy reservoir"
PHeiz-Stromp Thermal heating power of the conventional heating system in the
mode of operation (b), "Exclusive production of electricity from
thermal heat"
PHW Heat capacity demand for thermal heat (heat flow)
PRest Condensation waste heat capacity of the thermodynamic process
(heat flow)
PRuck Heat capacity of waste gas heat recovered (heat flow)
PSp IN Heat accumulator input power (heat flow)
PSp OUT Heat accumulator output power (heat flow)
PTHDY Power throughput of the conversion system of the thermodynamic
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process for the conversion into electrical energy
PTHDY1 Power throughput of the conversion system of the first stage (high
temperature stage) of the thermodynamic process for the conversion
into electrical energy
PTHDY2 Power throughput of the conversion system of the second stage (low
temperature stage) of the thermodynamic process for the conversion
into electrical energy
PM"V Heat capacity demand for thermal heat for domestic service water
(heat flow)
RL Return flow
SP Accumulator
t Time
tAusõ Open period of the outlet valve in the working cycle
tAusi2 Open period of the outlet valve in the contradirectional working cycle
tcyc Cycle duration of an overall cycle
tEinõ Open period of the inlet valve in the working cycle
tEinl2 Open period of the inlet valve in the contradirectional working cycle
tE, Expansion duration of a piston stroke
THDY Thermodynamic cycle
TKond Condensation temperature of the thermodynamic process
tto, Standstill period of the piston (dead time)
VEinl Inlet volume per stroke
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VL Flow line
WT Heat exchanger
WTHDY Work performed by a piston stroke WTHDY during the expansion in a
working cycle
WW Warm water
