Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02542376 2004-02-27
ENERGY MANAGEMENT SYSTEM, METHOD, AND APPARATUS
Field of the Invention
This invention relates to the field of energy management systems, methods, and
apparatus, such as may, for example, include the field of ice making systems
for
recreational facilities such as arenas.
Background of the Invention
Recreational facilities in mid-latitude climates may include an ice rink for
winter
sports such as hockey or curling, and may also include other facilities such
as a
swimming pool, concert hall or classrooms, dressing rooms, heated stands,
showers, and
so on. Up to now, ice making equipment has tended to be used to make ice, and
the heat
rejected in the ice making process may not necessarily have been used as
advantageously
as might otherwise have been possible or desirable. Arena ice making equipment
has
tended to be operated separately from building mechanical systems, rather than
being
fully integrated with them as proposed herein in a combined heating, air
conditioning and
refrigeration system. That being the case, in the view of the present
inventors it may be
advantageous to employ the rejected heat more effectively than previously. In
that
regard, the present inventors are of the view that it may be advantageous to
employ the
ice making apparatus as a heat pump to provide a source of heat for rejection,
with an ice
by-product that can be melted at a subsequent opportunity. That is, heating
and cooling
loads may not occur during the same time period, or may be unequally matched.
Given
that both heating and cooling loads may vary during the day, it may be
advantageous to
provide a large amount of rejected heat at one time of day, and a large amount
of
refrigeration at another. To that end the present inventors propose, as
described herein, to
provide an apparatus, and a method of using a thermal capacitance to address,
in some
measure, the timing mis-match that may occur between the heating and cooling
loads.
Summary of the Invention
In an aspect of the invention there is an energy management system. The energy
management system includes a refrigeration apparatus. The refrigeration
apparatus is
operable to reject heat. A refrigeration load ice sheet apparatus is connected
to the
refrigeration apparatus for cooling to make an ice sheet. A thermal storage
cold sink
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apparatus is connect to the refrigeration apparatus for cooling. A heating
load apparatus
is connected to be heated by the heat rejected from the refrigeration
apparatus. A load
management control system is operable at a first time to cause ice to be made
at the
refrigeration load ice sheet apparatus and to cause heat to be directed from
the
refrigeration apparatus to the heating load apparatus. The load management
control
system is operable at a second time to cause the thermal storage apparatus to
be charge as
a cold sink and to cause heat to be directed from the refrigeration apparatus
to the heating
load apparatus.
In another aspect of the invention there is a recreational facility. The
recreational
facility includes a refrigeration plant. An ice sheet pad is connected to be
cooled by the
refrigeration plant. A thermal energy storage cold sink reservoir is connected
to be
charged by the refrigeration plant. At least one building heating load element
is
connected to receive heat rejected from the refrigeration plant. The
refrigeration plant is
operable to draw heat from either the ice sheet pad or the thermal energy cold
sink
reservoir as a source of heat for rejection to the building heating load
element.
In another aspect of the invention there is a recreational facility. The
recreational
facility includes a vapour cycle refrigeration plant that uses a working fluid
and includes
a compressor, a condenser, an expansion device and an evaporator are all
operatively
connected together. There is an ice rink pad, a thermal energy cold sink
storage reservoir
and at least one building heating load element. There is a first heat transfer
transport
medium conduit assembly connected to carry a first heat transfer transport
medium
between the evaporator and the ice rink pad and between the evaporator and the
thermal
energy cold sink storage reservoir. There is a second heat transfer transport
conduit
assembly connected to carry a second heat transfer transport medium between
the
condenser and the building heating load element. The refrigeration plant is
operable to
draw heat selectively from either the ice rink pad or the thermal energy cold
sink storage
reservoir and to reject heat to the building heating load element. The working
fluid is
segregated from the first and second heat transfer transport media. The first
and second
heat transfer transport media is different from the working fluid.
In an additional feature of that aspect of he invention, the working fluid is
ammonia. In another additional feature of that aspect of the invention, the
first and
second heat transfer transport media are at least partially glycol. In a
further feature, the
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first and second heat transfer transport media are the same. In another
feature, the first
and second heat transfer transport media conduit assemblies are connected for
fluid
communication therebetween.
In another feature of that aspect of the invention, one of (a) the first heat
transfer
medium conduit assembly, (b) the second heat transfer transport medium conduit
assembly and (c) the first and second heat transfer transport medium conduit
assemblies
are connected together, includes a flow element operable to direct flow of at
least on of
the heat transfer transport media between the condenser and thermal energy
cold sink
storage reservoir.
In another feature, the recreational facility includes fluid flow elements
connected
to carry heat transfer transport medium flow between the condenser and the
thermal
energy cold sink storage reservoir. In yet another feature, the thermal-energy
cold sink
reservoir includes at least one container holding a thermal storage phase
change material
and the first heat transfer transport medium conduit assembly is connected to
permit the
first heat transfer transport medium to traverse the container. In still
another feature, the
recreational facility includes an array of containers holding a thermal
storage phase
change material.
In another feature, the heat transfer transport media from either of the first
conduit
assembly or the second conduit assembly can be directed selectively to engage
in heat
transfer with the storage reservoir. In still another feature, the
recreational facility
includes an air conditioning element in the nature of a fan coil unit
connected to the cold
sink storage reservoir by piping for carrying a heat transfer transport fluid,
that fluid
being at least partially anti-freeze.
In still another feature of that aspect of the invention, the recreational
facility
includes a thermal stratification reservoir for containing a portion of the
second heat
transfer transport medium. The thermal stratification reservoir has a low
outflow port
connected to an inlet of the condenser. The condenser has a high return line
emptying
into the thermal stratification reservoir and a plurality of building heating
loads connected
to draw a hot portion of the second heat transfer transport medium from the
reservoir and
to return the portion to the reservoir in a cooler condition. In another
feature, there is a
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hot off take manifold connected to an upper region of the thermal
stratification reservoir
the feeds a plurality of building heating load elements.
In yet still another feature of that aspect of the invention, there is a heat
rejection
from the refrigeration plant that is used to meet at least 50% of all the
building heating
requirements. In another feature, there is a heat rejection from the
refrigeration plant that
is used to meet at least 80% of all the building heating requirements. In
still another
feature, there is a method of operation of the recreational facility that
includes the step of
operating the refrigeration plant to produce heat for rejection to be directed
to the
building heating load and thereby charging the cold sink reservoir as a by-
product of
producing heat for rejection. In another feature, there is a method of
operation that
includes the step of cooling the ice rink pad at one time of the day while
rejecting heat to
the building heating load and charging the cold sink at another time of day.
In ayet
further feature, there is a method of operation that includes the step of
discharging the
cold sink at another time of day to reduce work input to the compressor.
In another aspect of the invention there is an ice forming apparatus. The ice
forming apparatus includes a compression apparatus, an expansion apparatus, a
first heat
exchange apparatus connectable to convey a working fluid from the compression
apparatus to the expansion apparatus, and a second heat exchange apparatus
connectable
to convey the working fluid from the expansion apparatus to the compression
apparatus.
The compression apparatus is operable to receive a gas phase of the working
fluid, and to
compress the gas phase. The first heat exchange apparatus is operable to
reject heat from
the compressed working fluid to a thermal sink. The expansion apparatus is
operable to
permit working fluid received from the first heat exchange apparatus to
undergo a
pressure drop to a temperature lower than the freezing point of water. The
second heat
exchange apparatus is operable to transfer heat from a thermal source to
working fluid
received from the expansion apparatus. There is a controller. The controller
is operable
to govern operation of the compression apparatus. The controller is operable
to cause the
compression apparatus to compress the working fluid to a first pressure to
yield a first
temperature in the compressed gas for a first rate of heat rejection to the
thermal sink.
The controller is operable to cause the compression apparatus to compress the
working
fluid to a second pressure to yield a second temperature in the compressed gas
for a
second rate of heat rejection to the thermal sink. The second pressure is
higher than the
first pressure.
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In another aspect of the invention there is a method of operating a
refrigeration
apparatus, the method including the step of providing a thermal storage
apparatus for
storing a cooled medium, thereby to provide a cold sink. The method includes
the step of
operating the refrigeration apparatus to produce a greater amount of rejected
heat than
required to obtain cooling for a cooling load, and the step of using the
thermal storage
apparatus as a reservoir for excess cooling potential developed while
generating that
greater amount of rejected heat.
Brief Description of the Drawings
These aspects and other features of the invention can be understood with the
aid
of the following illustrations of a number of exemplary, and non-limiting,
embodiments
of the principles of the invention in which:
Figure la shows a schematic representation of an example of a recreational
facility
embodying principles of the present invention;
Figure lb is a second schematic representation of the recreational facility of
Figure 1 a showing the relationship of heating load, cooling load, and heat
transfer apparatus for addressing the heating and cooling loads;
Figure 2 shows a Pressure v. Enthalpy chart for a refrigerating apparatus for
the
recreational facility of Figure 1 a;
Figure 3a shows a heating load v. time chart for the recreational facility of
Figure
1 a in January;
Figure 3b shows a thermal storage cold sink charge and discharge chart for the
recreational facility of Figure 1 a in January.
DETAILED DESCRIPTION OF THE INVENTION
The description that follows, and the embodiments described therein, are
provided
by way of illustration of an example, or examples, of particular embodiments
of the
principles of the present invention. These examples are provided for the
purposes of
explanation, and not of limitation, of those principles and of the invention.
In the
description, like parts are marked throughout the specification and the
drawings with the
same respective reference numerals. The drawings are not necessarily to scale
and in
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some instances proportions may have been exaggerated in order more clearly to
depict
certain features of the invention.
Description of a Recreational Facility
A description of the present invention may commence with the supposition of
the
existence of a building, such as a recreational center, indicated generally,
and
schematically in Figure 1 as 20. The recreational center may be a school or a
college, or
part of a school or a college, a community center or other building.
Recreational center
20 may include an arena, or ice rink 22, a swimming pool 24, conference rooms,
or class
rooms 26, dressing rooms 28, showering facilities 30, stands for spectators
32, a
gymnasium 34, and an auditorium 36 , an indoor soccer pitch 38, or some
combination
thereof. The ice rink may be a curling rink, which may have multiple sheets,
or may be a
pleasure skating or hockey rink with one or more ice pads. Such a building may
have
cooling loads (that is, a need for cooling or refrigeration) and heating loads
(that is, a
need for heating) that may vary with the time of day, the season of the year,
the activities
occurring in the building, and the amount of sunshine per day. There may be
simultaneous heating and cooling loads, as when there is a cooling load to
make ice in the
ice rink, and a heating load to keep the gymnasium or auditorium warm. A space
that
requires heating at one time of day may require cooling at another time of
day. For
example, when the auditorium is used as a fractionally filled lecture hall it
may require
heating, but, later, when it is used as an entertainment hall for a sold out
public
perfonnance, it may require cooling.
In general, there will be time varying-cooling and heating load profiles for
recreational center 20. The cooling load may tend to be lowest at night, and
higher
during the day, particularly when the Sun is shining on the building. During
the night the
rink may be on "night set-back", since the rink is not in use, and needs only
to be
maintained in its condition, rather than being capable of making new ice. The
heat loads
in the arena may be less at night as well, given the generally cooler external
ambient at
night, the absence of a light load (assuming the lights are turned off at
night), and the lack
of a human load when the building may tend to be unoccupied. Figure 3a shows
the
heating load in a colder period of the year, such as January in the Northern
hemisphere.
It is assumed that ice rink 22 may be maintained in operation year round.
This, of course,
is not necessarily true at all ice rink locations. Some locations operate as
ice rinks in the
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Winter months (typically from September 1 to April 30 in southern Canada, for
example), and as rinks for roller skating or in-line roller blading in the
Summer months.
The building, namely recreational center 20, may be equipped with an energy
management system, indicated generally as 40, for responding to these
environmental
loading conditions. Energy management system 40 may include a refrigeration
plant or
apparatus, such as may be in the nature of an ice making apparatus 42
connected to cold
floor piping 44 embedded in a concrete pad defining a floor of ice rink 22; a
cold sink
thermal storage member, or apparatus, indicated as an "ice reservoir" 46; a
first
underfloor radiant heating system 50 for use in the arena stands, a second
underfloor
radiant heating system 52 for use in the gymnasium, a hot water supply 54,
such as may
be used to provide domestic hot water or Zamboni (t.m.) water; a snow pit
heater 56; a
building fan coil heating or air conditioning system 58, a building radiant
heat zone
apparatus 60, a building heat pump 62, and a supplemental heating device 64,
such as
may be an oil or gas fired boiler 66. A"Zamboni" is a brand of ice refinishing
truck that
is used to renew the ice surface every hour or two during normal hours of
operation (e.g.,
roughly 6 a.m. to midnight).
Refrigeration Apparatus
Refrigeration apparatus 42 may be a vapour cycle system in which a working
fluid is passed, in succession, through a pressurizing stage 68, as when run
through a
pump, or compressor 70; a cooling stage 72, as when passed through a first
heat
exchange device 74, such as condenser 76; an expansion stage 78, such as when
passed
through an expansioii apparatus 80, such as may be a valve, or nozzle, 82; and
a heating
stage 84, such as when passed through a second heat exchange device 86, such
as may be
identified as a chiller, or evaporator 88.
The Compressor
Compressor 70 may be a reciprocating compressor, may be a rotating vane
compressor, or a screw compressor. The compressor may be a gas compressor that
may
be used to compress a working fluid in a gaseous state to a higher temperature
and
pressure. Compressor 70 may symbolise not merely a single compressor, but an
array of
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two or more compressor units, such as units, 90, 92, arranged in parallel to
permit partial
operation at times of reduced demand.
The Condensor
Working fluid may be carried from the outlet of compressor 70 to the inlet of
the
condensor in a fluid conducting element 94, such as a piping for carrying high
pressure
gas. Condensor 76 may typically be a heat exchanger of either the tube and
shell type or
the multiple alternating plate type with either a dual or multiple plate
arrangement, and
may be either a cross flow heat exchanger, or a counter flow heat exchanger.
It may be
advantageous to employ a counter-flow multiple plate capillary tube heat
exchanger to
obtain relatively high performance. Heat exchanger 74 has a first fluid path
for the
refrigerant working fluid, that path having an inlet 96, and an outlet 98,
inlet 96 being
connected to receive hot, high pressure working fluid from compressor 70, and
outlet 98
being connected to permit cooled,. high pressure working fluid to be conducted
to
expansion apparatus 80. Heat exchanger 74 also has a second fluid flow path,
the second
fluid flow path being segregated from the first fluid flow path. The nature of
the heat
exchange in condensor 76 is such that the first fluid flow path is the hot
side. of the
condensor from which heat is being extracted, and the second fluid flow path
is the cold
side of the condensor through which coolant flows, thereby carrying heat away.
A
coolant for the cold side of condensor 76 may be chosen from any of a number
of cooling
media, of which, in one embodiment, the coolant may be glycol (t.m.). In a
vapour cycle
system, such as may be employed, the state of the working fluid may tend to be
transformed in condensor 76 from a superheated gas to a liquid, or to a mixed
phase fluid
of partial gas, partial liquid quality.
The Expansion Device
Cooled, relatively high pressure working fluid may be conducted in a fluid
flow
conduit 100, such as may be a high pressure seamless steel pipe, to expansion
apparatus
80. Expansion apparatus 80 may tend to be a substantially adiabatic device in
which the
pressure of the fluid is reduced, with a corresponding drop in temperature,
and enthalpy.
Expansion apparatus 80 may, in some instances, be a work extraction device, in
the
nat~lre of a turbcmachine,-or may be a nozzle, orifice, or valve, of suitable
geometry, such
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as nozzle 82. In a typical vapour cycle device, the working fluid enters the
expansion
device as a liquid, or largely liquid flow.
The Evaporator
Evaporator 88 may include second heat exchange device 86, connected to
expansion apparatus 80 by a low side pressure fluid conduit, or pipe 102.
Fluid carried
by pipe 102 enters evaporator 88 at inlet 104, and follows a first flow path
through the
evaporator to an outlet 106. Evaporator 88 also has a second flow path,
segregated from
the first flow path. The first and second flow paths of evaporator 88 are
segregated from
each other and may be in a cross-flow, or counter flow arrangement. As above,
evaporator 88 may have the physical form of a.tube-and-shell heat exchanger,
or may
have the form of a heat exchanger having multiple, substantially parallel
plates or layers.
These layers may be tightly packed to give a low temperature difference across
the heat
exchange interface between the coolant and the working fluid. By the nature of
the
device, the hot side of the heat exchanger is the second flow path, which may
contain a
relatively inert and relatively benign heat exchange fluid that may tend to be
in the liquid
phase, and that has a freezing point below the range of operation of the
machine. This
coolant medium may be a fluid such as glycol (t.m.). This heat exchange fluid
may flow
in a circuit of piping connected with one or more of the cooling load devices
noted
below. The cold side of this heat exchanger (i.e., evaporator 88) carries the
working
fluid. Most typically, working fluid entering evaporator 88 may be of
intermediate
quality in a mixed liquid and vapour state under the pressure done as
indicated in the
Pressure v Enthalpy chart of Figure 2. Heat added in evaporator 88 converts
the working
fluid to gas. It is often desirable for the working fluid leaving evaporator
88 to be
somewhat superheated beyond the saturated gas line, thereby tending to avoid
ingestion
of liquid working fluid into compressor 70. For the purposes of analysis, a
designer may
wish to consider four thermodynamic state points for the working fluid, those
points
being (1) at the inlet to compressor 70;(2) at the outlet of the compressor
70; (3) at the
outlet of the condensor76; and (4) at the inlet to evaporator 88. Also for the
purposes of
simple or approximate analysis, although there is fluid flow resistance in
both heat
exchange elements, they are idealised as being constant pressure devices.
Working Fluid
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In this example, in the event that a vapour cycle system is used, as opposed
to a
gas cycle or other system, the vapour cycle system may employ a working fluid,
as noted
above. That working fluid may be any of a number of possible working fluids,
be it an
HCFC working fluid or some other. In one embodiment the working fluid may be
refrigerant R-404A. In another embodiment the working fluid may be ammonia,
also
designated as refrigerant R - 717.
Ammonia may be chosen as a working fluid for a number of reasons. It is
readily
available; it is relatively inexpensive; it dissipates relatively quickly and
easily in air, it
does not tend to cause lasting environmental damage in terms of either ozone
depletion or
green house gas omissions if it leaks, and does not tend to present a long
lasting toxicity
problem when disposal is desired; and, in ice making technology, there is a
well
established level of knowledge and expertise in the industry in using ammonia.
Further,
the working range of pressures and temperatures for ammonia may tend to be
suitable for
the present purposes. Ammonia may tend to permit the use of relatively common
mineral oil lubricants, as opposed to highly specialized (and expensive)
hygroscopic oils.
Ammonia may tend to permit smaller pipe sizes, better heat transfer and
smaller heat
exchangers. Leaks may tend to be relatively easy to detect. Ammonia tends to
be
relatively tolerant of moisture in the system.
Heat Transfer Transport Medium
Refrigerating apparatus 42 may be contained in a separate building, or
segregated
structure 110, as, symbolised by the dashed line rectangle in Figure lb. This
construction
permits all devices through which the working fluid passes (which may be
referred to as
the refrigeration plant) to be segregated from, and to be separately
ventilated from, the
enclosed building structure of facility 20 in which persons may be engaged in
recreational activities. In this way, a leak of the working fluid may tend not
to migrate
into occupied areas of recreational facility 20, and may tend to be vented to
external
ambient. In keeping with this, heat transfer transport medium conduit
assemblies,
namely the heating and cooling circuits emanating from segregated structure
110, such as
low pressure coolant circuit 112 that carries coolant to and from the cold
side of
condensor 76, and low pressure coolant circuit 114 that carries coolant to and
from the
hot side of the chiller, i.e., evaporator 88, may tend to be relatively low
pressure, liquid
conduits operating at modest positive pressure over ambient, carrying a more-
or-less non-
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corrosive liquid heat transfer medium in the nature of a liquid coolant of
relatively low
toxicity, and low volatility, and such as may tend not to pose an undue
environmental
hazard if a leak should occur, such an antifreeze or antifreeze mixture of
which one type
may be glycol. A fluid of this nature may tend to be significantly less
corrosive than
Ammonia or a brine solution. Further, when used in the context of this
application the
term "glycol" may refer to a mixture of glycol and water such as may be
suitable for the
operating range of the equipment, be it -30 C to + 60 C, -40 C to + 70 C or
some other
range.
Coolinp, or Refrigeration Load and Storage Elements
Cold Floor Piping
Whether for heating or cooling loads, the piping, or assembly of conduits for
carrying the heat transfer fluid transport medium, may tend to be laid out in
a manner
defining a circuit, or a plurality of circuits, through which coolant may be
pumped to and
from the refrigeration plant and the various Heating and cooling load
elements.
Referring to the schematic of Figures la and lb, the primary cooling load for
an
ice making apparatus in an area is, generally speaking, the refrigeration load
of the ice
rink pad or pads. To that end, ice rink 22 has underfloor cold ice piping 42,
as noted. In
the embodiment of Figure la, coolant circuit 114 is connected to the hot side
outlet 122
of the chiller (i.e., evaporator 88) by a first fluid conduit portion in the
nature of a pipe
section 124 leading to a cooling loop pump 126 that may be used to urge
coolant through
a tee 128, and through a first valve 130 and into cold floor piping 44. Cold
floor piping
44 may include a header identified as rink inlet manifold 132. An array of
underfloor
loops 134 are fed from the common pressure source of rink inlet manifold 132,
loops 134
returning to, terminated at, and discharging into, a second header, identified
as rink return
manifold 136. Return line 138 carries the coolant back through a tee 140 to
the inlet 142
of the hot side of the chiller. It is understood that in passing through loops
134, the
coolant will tend to draw heat from the ice rink pad, or pads, as the case may
be, and, to
the extent that the pad is maintained at a temperature below the freezing
point of water,
and to the extent that sufficient water is maintained above the pad, a sheet
of ice will be
maintained in a frozen state, or new ice may be made as a surface accretion of
water is
frozen. Thus heat may flow from the arena surrounding into the pad of ice,
from the pad
of ice into the coolant loops, and from the coolant into the evaporator.
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Although only one array of loops is indicated in the schematic, this may be
representative of two or more pads, each having an array of cooling loops, and
which
may be fed sequentially between inlet and outlet manifolds such as may be
controlled by
selectively operating a number of valves according to a refrigerating duty
cycle, or
simultaneously, as may be desired.
Cold Sink Thermal Storage Reservoir
As noted above, the coolant circuit may include a first tee 128 upstream of
the ice
pad, and a second tee 140 downstream of the ice pad. First tee 128 may be used
to feed
coolant fluid through an alternate fluid communication path, namely ice
reservoir feeder
pipe 144, to a second valve, identified as ice reservoir inlet valve 146.
While valve 146
may have two inlets, 148 and 150, as indicated, it has but a single outlet 152
leading to
ice reservoir 46. Valve 146 may have three positions - namely, inlet 148 open,
and inlet
150 closed; or inlet 148 closed and inlet 150 open, or both inlet 148 and
inlet 150 closed.
Similarly, the outlet of ice reservoir 46 feeds a third valve, identified as
ice reservoir
outlet valve 154. Outlet valve 154 has an inlet 156, and a pair of alternately
selectable
outlets, 158, 160. This valve may have three positions as well, namely outlet
158 open
and outlet 160 closed; outlet 158 closed and outlet 160 open; or both outlet
158 and outlet
160 closed. Outlet 158 is connected to a cooling side return line 162 which,
in tum,
meets coolant return line 138 at tee 140. Differential operation of valves
130, 146 and
154 may then permit the coolant medium on the hot side of the chiller to be
directed to
the floor loops 134 of the ice pad, or pads (as when valve 130 is open, and
valve inlet 148
is closed), or to ice reservoir 46 (as when valve 130 is closed and valve
inlet 148 and
valve outlet 158 are open, and inlet 150 and outlet 160 are closed).
Given the operation described, the positions of valves 130, 146 and 154 may be
interlinked mechanically or electronically. In particular, the positions of
valves 146 and
154 may be governed such that both are open at the same time to flow of
coolant in the
cooling circuit and closed to coolant flow from the heating circuit; or,
conversely, both
are open to the heating load side of the system, but closed to the cooling
circuit. The
positions may also be governed in such a manner that when inlet 148 and outlet
158 are
open, inlet 150 and 160 are prevented from opening, and vice versa. It may
also be noted
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that coolant pump 126 may have a pressure relief bypass in the event that both
valve 130
and valve 146 are closed simultaneously, as they may be during a change of
duty cycle.
The cold sink thermal storage member, or thermal capacitance member may, for
brevity and simplicity be referred to as an "ice reservoir", 46. It may be
that ice reservoir
46 is an accumulation of ice, typically enclosed in an insulated wall
structure, identified
as 164. It may also be that ice reservoir 46 is not "ice" at all, but rather a
brine, or an
eutectic fluid, or some other medium such as may tend to have a significant
thermal
mass, such that ice reservoir 46 may tend to work as a thermal capacitance
that can be
"charged up" by being cooled over a period of time, so that it may then have a
large
capacity to cool other objects at a later time. This is illustrated in Figure
3b. It may be
that ice reservoir 46 employs a phase change material, such as a eutectic
fluid as noted
above, where there is a significant enthalpy drop between the warm state,
possibly a
liquid or quasi-liquid state, and the cool, or cold state, possibly a solid or
quasi-solid
state. A liquid freezing point would, for example, tend to be just such a
large enthalpy,
narrow temperature range phenomenon. Where an eutectic material is used, it
may be an
eutectic having a phase change temperature lying in the range of - 40 to + 20
F, or
possibly in the narrower range of -20 F to + 0 F. The phase change medium may
be
water, or an aqueous solution.
The arrangement described thus far may tend to permit coolant to flow
selectively
to either ice reservoir 46 or cold floor piping 44, or to both in parallel if
valve 130 is
maintained in an intermediate or partially open condition. However, as
described to this
point the two loads have not been placed in series with each other. In an
alternate
embodiment, a further valve 170 may be located in line 162 between valve 154
and tee
140, this valve 170 having an inlet 172 fed by line 162 from valve 158. Valve
170 may
also have a first alternately selectable outlet 174 by which to direct flow
through to tee
140, and hence to the return, and a second, alternately selectable outlet 176
by which to
direct flow of coolant from ice reservoir 46 through alternate feedline 178 to
a tee 180
connected between valve 130 and inlet manifold 132 to permit feed inlet
manifold 132 of
the underfloor cooling loops 134 of the ice pad. In operation, if valve 130 is
closed, inlet
148 of valve 146 is open, outlet 158 of valve 154 is open, outlet 174 is
closed, and outlet
1.76 is open, coolant driven by pump 126 will be forced through ice reservoir
46, and then
in series into cold floor piping 44.
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In yet a further alternative, a valve 190 may be teed into the coolant return
line
138 outlet line running from outlet manifold 136 of the array of underfloor
cooling loops
toward the chiller. Valve 190 may have an inlet 192 oriented toward the ice
pad outlet
manifold 136, a first outlet 194 oriented toward the chiller, and a second
outlet 196
oriented toward a shunt line 198 that meets the inlet line of ice reservoir
46. By closing
inlet 148 of valve 146 (inlet 150 also being assumed closed), opening valve
130, opening
outlet 158 of valve 154 (and closing outlet 160), and opening outlet 196 while
closing
outlet 194, coolant driven by pump 126 can be directed through the cold floor
piping 44
of the ice pad in series with ice reservoir 46, but with the coolant being
directed to ice
reservoir 46 after leaving the ice pad cooling array, rather than before.
Ice reservoir 46 may be a large insulated enclosure 164, or box or fluid tight
chamber through which liquid coolant, such as glycol, can be pumped. The
enclosure
may contain a large number of hollow balls 166 such as may be made of a
plastic
material. Balls 166 may contain a phase change thermal storage medium, which
may be
distilled water, or some mixture or other substance such as may have, for
example, a
large enthalpy change at a state change plateau temperature, or relatively
small range of
temperature, in the desired operating temperature range as noted above. Balls
166 may
be stacked to permit interstitial flow of the liquid coolant. Balls 166
segregate the heat
transfer storage medium phase change material from the heat transfer transport
medium.
Ice reservoir 46 has an inlet 182, and an outlet 184, such that coolant fed in
at inlet 182
may tend to work its way through any of a large number of possible flow paths
by
wending about the collection, or stacked array, of balls 166 to outlet 184,
this process
being accompanied by heat transfer between the diffusely moving liquid and the
thermal
storage medium containing balls 166. Where the liquid heat transfer medium is
warmer
than the material in the balls, the liquid may tend to be cooled, and where
the liquid is
cooler than the material in the balls, the liquid may tend to be warmed.
Hot Side Elements
Thermal Ecqualizer
Thermal equalizer 204 is a large heat exchange fluid heat transfer medium
stratification reservoir, or tank. The cold side loop 112 drawing hot coolant
from outlet
200 of condensor 76 is carried to hot side inlet 208 near the top of thermal
equalizer 204,
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and may be drawn out at the relatively lower temperature outlet 210 located
near the
bottom of thermal equalizer 204, through pump 212, and back to inlet 102 of
evaporator
88. Cold side loop 112 carries relatively benign coolant, such as glycol (or,
as noted, a
glycol-water mixture), out of segregated structure 110 that contains
refrigeration
apparatus 42.
Thermal equalizer 204 may be served by a multi-path conduit assembly
identified
as coolant circuit 214, having a hot, or upper outlet manifold 216 whence to
draw off
warmed coolant, and a return, or cooled, lower inlet manifold 218 at which to
introduce
returning coolant. Thermal equalizer 204 includes a third path, through which
coolant
may be passed on a closed circuit cooler loop 220, driven by coolant pump 222.
At times
when there is no thermal load, or insufficient thermal loading, to accept all
of the heat
rejected from refrigeration apparatus 42, the excess heat rejected from
condensor 76 may
be dumped into coolant carried in coolant circuit 214, whence it is rejected
into water
such as may be sprayed over cooling pipes in closed circuit cooler 224. The
water thus
warmed may drain into a water sump 226, from which it is drawn by pump 228 and
conducted again back into closed circuit cooler 224.
Thermal equalizer 204 is a reservoir in which the coolant medium may settle
and
stratify according to temperature. Thus hot return flow from condenser 76 is
added to the
top of thermal equalizer 204, and cooled coolant directed to the inlet of
condenser 76 is
drawn from the bottom of thermal equalizer 204. Similarly, hot fluid for
direction to the
various heating loads is drawn from the upper region of equalizer 204, and
returned to the
bottom.
Supplemental Heat
On occasions where there may not be sufficient rejected heat available from
condensor 76 to meet all of the heating loads of recreational facility 20, or
where the
temperature of the heat rejected is not fully sufficient to meet the
temperature
requirements of, for example, a radiant or fan coil heater or a hot water
heater, that unmet
demand may be met by the employment of a supplemental heating device, such as
oil or
gas fired boiler 66. Further, a supplemental heating device may be employed in
the event
that refrigeration apparatus 42 is not in service, and an alternate heat
source is required.
To that end, pump 230 may urge coolant from thermal equalizer outlet manifold
216
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along line 232 to boiler 66. In the event that extra heating is not required,
the coolant
may pass through the supplemental heating device, or through a bypass, without
the
heating element being in operation. After leaving the supplemental heating
device, the
coolant, having had a temperature boost (or not, as may be appropriate in the
circumstances), may be directed to pump 234. Pump. 234 may be used to urge the
warmed coolant through the building fan coil forced air heating system, such
as may be
used in the classrooms, the auditorium, the dressings rooms, and so on. At
some times of
year this system may be used to provide heating, and at other times of year to
provide
cooling (e.g. to act as an air conditioner), such as when coolant from ice
reservoir A6 is
directed through cooling circuit 238 and building fan coil 58 and returned via
the shunt
valve between return line 236 and line 282. When used for heating, coolant
exiting the
fan coil heating system is carried along return line.236 to inlet manifold
218.
Alternatively, or additionally, warm coolant leaving the supplemental heating
device may be directed to pump 240. Pump 240 is operable to urge coolant
through
building radiant zone heating apparatus 242. Apparatus 242 may, again, be
installed in
classrooms, in dressing rooms, in hallways, in the auditorium, and so on.
Coolant exiting
this system returns through line 236 to inlet manifold 218.
In a further alternative,, warm coolant leaving the supplemental heating
device
may be directed to pump 244. Pump 244 is operable to urge coolant through heat
pump
246, such as may be operable to provide local heating or cooling within
recreational
center 22. As before, return coolant is directed into return line 236 and
carried to inlet
manifold 218.
In another heating load circuit, pump 250 draws warmed coolant from outlet
manifold 216 and urges it along fluid conduit 252 to provide heating to the
multi-loop
heating element 254 to melt snow in the snow pit 56 in the Zamboni room. The
return
line 256 from snow pit 56 carries coolant back to inlet manifold 216. In yet
another heat
load circuit, pump 260 may draw warmed coolant from outlet manifold 216 and
urges it
along fluid conduit 262 to underfloor heating array 264, which may include an
inlet
manifold, or header, 266, an outlet manifold, or header 268, and several
underfloor
heating loops 270 such as may be used to provide radiant floor heating in a
gymnasium,
on a pool deck, under a walkway, or in one of the other rooms or enclosed
spaced of
recreational facility 20. Coolant then flows from outlet manifold 268 through
return line
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272 to inlet manifold 218. In still another heating load circuit, hot coolant
from thermal
equalizer 204 is driven by pump 280 from outlet manifold 216, through fluid
conduit 282
to the hot side of valve 146, through which it may be directed through ice
reservoir 46,
valve 154, and return line 284 back to inlet manifold 218. This may occur when
valves
146 and 154 are "open" to the heating load fluid, and closed to the cooling
load fluid. In
this instance, the cold storage capacity of ice reservoir 46 is employed as a
heat rejection
sink for heat extracted from condensor 76. This, in turn, may tend to reduce
the inlet
temperature on the cold side of the condensor, and allow the system to operate
at a lower
heat rejection temperature. To the extent that the charging cycle of the ice
reservoir is
premised on the existence of time periods in which the heat load exceeds that
amount of
rejected that that would otherwise normally be available from the
refrigeration plant
maintaining the ice sheets, the portion of the cycle in which the ice (or
solid phase of the
storage medium) in ice reservoir 46 may melt may tend to be coincident with
(a) a
reduced heating load or (b) a differential shift to a greater ice pad cooling
load.
Alternatively, the ice (or solid phase) may be melted by operating the system
to provide,
for example, air conditioning through circuit 238 as noted above.
In the foregoing example, the heat transfer transport medium, namely the
liquid
coolant, from the hot side of the system (i.e., the side with the heating
loads) may be
directed through ice reservoir 46 to draw out the stored cooling, in the same
manner as
the heat transfer medium on the cold side of the system (i.e. the side with
the refrigeration
loads) had previously been directed through ice reservoir 46 to charge up the
thermal
storage medium by freezing (i.e., changing the phase from liquid to solid) the
thermal
storage medium inside balls 166. This may be facilitated by using the same
heat transfer
transport medium in both the hot and cold sides of the system, and may permit
fluid from
the hot side and from the cold side of the system to be passed alternately
across the
thermal storage medium array. Further, the use of a relatively non-corrosive
liquid, such
as glycol or a glycol mixture, may tend to permit the same fluid to be used in
conventional building heat exchangers of either the forced air or radiant
types, thus
tending to facilitate the integration of the ice making refrigeration source
as a heat pump
for satisfying other building loads, as formerly addressed by conventional
building
mechanical systems for heating and air conditioning.
Electronic Control
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Operation of energy management system 20 is governed by an electronic control
system, 300, that includes a controller 302, and an array of sensors 304 such
as may
include (a) temperature sensors; (b) pressure sensors; (c) humidity sensors;
(d) volumetric
flow rate sensors; (e) thermostat settings; (f) external ambient condition
sensors (g) solar
sensors; and (h) a clock, or clocks. The use of temperature and pressure
sensors in
refrigeration apparatus 42 permits the operating statepoints to be known, and
adjusted,
according to existing heating and cooling demands, and according to
anticipated demand
such as may be determined from historic demand parameters stored in memory,
and on
the basis of external weather conditions.
Electronic control system 300 may include a memory 320 having climatic data
for
the site of installation, including sun rise and sunset times for the
location, and it may
have stored ambient temperature and pressure information from recent days for
use in
extrapolating thermal load management estimates. It may include setting
temperatures
for the various heat sinks and heat sources. The memory data may include data
for
working fluid pressure, temperature, enthalpy, entropy, and density, from
which other,
intermediate statepoint conditions may be interpolated. Electronic control
system 300
may also include programmed steps for calculating the statepoints at which
refrigeration
apparatus 42 might best operate for given loading conditions, or expected
loading
conditions based on time of day, weather, and historic demand.
Examples
In one embodiment, a vapour cycle system such as may be employed in
refrigeration apparatus 42 may use Ammonia as a working fluid. The low side of
the
vapour system may operate at a low pressure, PLOW of between 30 and 40 psia,
and may,
in one example, operate at about 38 psia, with a temperature under the vapour
dome of
between 0 F and 20 F, and possibly about 10 F when PLOW is 38 psia at the
first
statepoint at the exit from evaporator 88. There may be a few degrees of
superheat at
evaporator 88 to discourage the ingestion of liquid working fluid in
compressor 76, or
compressors 76, as may be. Referring to Figure 2, compression may occur along
a
roughly isentropic path from the first statepoint at the inlet to compressor
70 to the
second statepoint at the inlet to condensor 88 (the increase in entropy being
relatively
small), and may be roughly adiabatic, with relatively little opportunity for
either heat loss
or heat gain in the compressor itself. The high side of the system, at the
second state
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psia, during
daytime operation (that is, between about 8 a.m. and 8 p.m.). The temperature
at the
second statepoint may be in the range of 200 - 260 F, depending on the
pressures. The
hot side condensing temperature at the third statepoint (at the outlet of
condensor 88) may
be in the range of about 80 F to 120 F, and may, when Phigh is about 181 psia
be about 95
F. The outlet of the condenser may operate at a statepoint lying at or very
near to the
saturated liquid line of the vapour dome. Expansion through the expansion
device, which
may be a valve, from the third statepoint to the fourth statepoint at the
inlet to the
evaporator 76 may be considered to be adiabatic. The co-efficient of
perfonnance of this
system operating between these pressures, and with an expansion device inlet
condition
at Phigh and saturated liquid, may be about 4.2 to 4.3
During night-time operation this system may operate at about the same
conditions
on the low side, but at a reduced temperature and pressure on the high side.
That is,
during the night, the cooling load on the ice pad may be much lower, so the
system may
run at a reduced output. During this time there may be excess refrigeration
capacity, well
in excess of the cooling required to maintain the sheet, or sheets, of ice in
the arena. In
some instances, the environmental control system for recreational facility 20
may operate
very well under these conditions.
In that light, the system may operate with a reduced pressure differential
during
night time operation, such that the statepoints may be approximately as
follows: The first
statepoint, at the inlet to the compressor, may be at a pressure of between 30
and 40 psia,
and may, specifically, operate at about 38 psia. The outlet temperature may be
about 10
F, and the condition of the working fluid may be at the saturated gas line, or
may be
warmer by a few degrees of superheat to discourage ingestion of liquid working
fluid in
the compressor.
The working fluid is compressed from the first state point to the second
statepoint
in a nearly isentropic, substantially adiabatic compression. The second
statepoint, at the
iiilet of the condensor may be at a pressure of between 120 and 140 psia, with
a
temperature of between about 65 and 80 F, and may be at about 126 psia at
about 70 F.
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The third statepoint, at the outlet of the compressor or inlet of the
expansion
device, may be at the saturated liquid line, at the high pressure, which, as
noted, may be
in the range of 120 to 140 psia, and may be about 126 psia.
The fourth statepoint is reached by adiabatic expansion through the expansion
device, such as may be a valve, from the third statepoint to the low side
pressure of the
first statepoint.
For this example, the co-efficient of performance may be between 7.0 and 8.0
and
may be about 7.26.
During night time operation the cooling capacity of refrigeration apparatus 42
may be used alternately to maintain the ice surfaces and to charge ice
reservoir 46 by
adjusting the positions of the various valves in the coolant load circuits.
During daytime operation, heat rejected from the condensor, and carried
through
thermal equalizer 204, may be used to heat ice reservoir 46, with the effect
that the heat
rejection temperature seen at the condensor may be somewhat reduced. This may
permit
the system to be operated at a somewhat more efficient operating point than
might
otherwise be the case during the time it may take to "discharge" ice reservoir
46. At
another time, such as at night, the process may again be altered to re-charge
ice reservoir
46, and so on.
However, it may be that the heat rejected by refrigeration system 42 while
this
substantially reduced night time load is being addressed may not be fully
sufficient to
address other heating loads in recreational facility 20. That is, it may be
desired to have
greater heat rejection, at higher temperatures. In that instance,
refrigeration system 42
may be operated at a greater percentage of its overall capacity to provide a
greater
amount of rejected heat, at a higher heat rejection temperature. In so doing
refrigeration
apparatus 42 may provide cooling to charge up ice reservoir 46 (that is, to
extract heat
from ice reservoir 46, thereby tending to cause a significant enthalpy
reduction in the
thermal storage medium such as may tend to cause a phase change, such as
freezing, of
the thermal storage medium). It is assumed that, in general, in a mid-latitude
location,
during much of the hockey season that for much or all of the day the external
environmental conditions may include an ambient temperature greater than the
freezing
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point of water, namely 32 F, (or, really, greater than about 20 - 25 F, since
it may be
better to have a sheet of ice for hockey, skating, or curling, whose
temperature is
modestly, yet clearly, below the freezing temperature) such that refrigeration
is required
to maintain the ice rink surface, or surfaces, at an appropriate temperature
for hockey,
pleasure skating or curling. It need not necessarily be so, since
refrigeration apparatus 42
may be used as a heat pump to reject heat into recreational facility 20 even
when the
external ambient temperature is significantly lower than 20 F.
In those circumstances, rather than being operated at a full set back
condition,
refrigeration apparatus may be operated to reject a greater amount of heat,
and thereby to
produce a greater amount of cooling than might otherwise be required merely to
maintain
the ice sheets in their desired frozen condition.. That being the case,
operation may
include the step of re-directing coolant flow leaving the chiller (i.e.
evaporator 88) hot
side through ice reservoir 46, rather than (or in addition to, or in
alternating duty cycle
with) cold floor piping 44, thereby "charging" ice reservoir 46. Operation may
then
include operating at a floating head pressure (i.e., the pressure at the
compressor outlet)
to yield a desired outlet temperature at outlet 200 of circuit 112 (or at
inlet 208 of thennal
equalizer 204) thereby yielding heat to be directed to any of the heating load
elements
described above as may be appropriate in the circumstances. Thus, for example,
rather
than having a compressor outlet temperature of 70 F, the outlet pressure may
be about
130 - 150 F t yield useful heat for zone heating or water heating. The
corresponding high
side pressure might be in the range of approximately 80 - 120 psia, or, less
modestly, it
might be run at 160 - 200 psia, as may occur during customary daytime
operation, e.g.
181 psia @ about 220 F. A "floating" head pressure may be obtained by
providing a
compressor that is variably operable to yield varying output pressures. It may
be noted
that electricity may be less expensive at night than during daytime hours such
that the
cost of extra operation of the compressors at night may not be unduly high.
In a first example of an alternate embodiment, the low side of the vapour
cycle
system may operate at a colder temperature, being in the range of - 5 to - 30
F, and
perhaps about - 15 to - 25 F. In such an embodiment, ice reservoir 46 may
contain a
eutectic material having a melting point in the range of - 20 to 15 F, that
is, the phase
change from solid to liquid of the "ice reservoir" thermal storage medium may
take place
under the vapour dome at a temperature level, on the phase change plateau,
that is less
than the freezing point temperature of the fluid, namely water, from which the
hockey ice
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is to be made, and, indeed, at a temperature that is less than the desired use
temperature
for the ice surface. To the extent that the desired ice surface temperature
for skating may
be in the range of 20 - 25 F, the thermal storage medium may have a eutectic
phase
change temperature may be in the range of- 25 to about 10 to 15 F.
In the event that ice reservoir 46 is connected in series with the cooling
loops 134
of the ice pad array, the enthalpy of the phase change in ice reservoir 46 may
be used to
provide a measure of extra cooling of the coolant fluid being admitted to the
underfloor
coolant loops (which may, in turn affect, in some measure, statepoint 4), as
when ice
reservoir 46 is upstream of the underfloor cooling loops of the ice pad, and
valve 170 is
employed. Alternatively, the change in enthalpy of the phase change of the
thermal
storage medium in ice reservoir 46 may be used to suppress the enthalpy of the
coolant
that is returned to the chiller at statepoint 1, as when ice reservoir 46 is
connected in
series downstream of the underfloor cooling loops, as when valve 190 is
employed.
Where this series operation is employed, whether upstream or downstream, it
may be that
inlet 154 of valve 150, and outlet 164 of valve 158, may be substantially
permanently
closed, or, alternatively, valves 150 and 158 may not then require inlet 154
and outlet 164
respectively, and the attaching piping to the "hot" side of the system may be
omitted.
In the operation described above, the system may employ a "floating" high
pressure on the condensor side, such that the system may adjust the heat
rejection
temperature at the condensor according to the need for rejected heat to
address heating
loads in recreational facility 20.
Operation of this apparatus may involve a number of logically related steps.
That
is, operation may commence at a given time of day. For that time of day the
microprocessor in the controller may seek historic data for expected demand in
the
upcoming time period. It may also determine the state of the "ice reservoir"
by polling
the temperature sensor in the ice reservoir to determine if the ice reservoir
is below, at, or
above its phase change plateau., It may poll temperature sensors in the ice
pad floor to
obtain an indication of ice temperature, and the various temperatures of
coolant loops at
inlets and outlets from their loads. It may also determine which pumps are
"on" and
which are "off'. Where there is a cooling load, the controller may cause
refrigeration
apparatus 42 to operate for a period of time until the cooling load reaches a
low set point
temperature, as may be determined either from values established in memory or
that may
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be keyed in digitally at an input device, or set in an analogue manner using
an analogue
thermostat. At that time refrigeration apparatus 42 may return to a dormant
state, and
may remain in a dormant state until the load reaches a higher temperature, at
which the
refrigeration apparatus may again be activated. This is a simple "On-Off'
control
mechanism between a pair of high and low set point temperatures, with the
output
temperature being cycled in a band between the high and low set point
temperatures. In a
further alternative, a more sophisticated "trend monitoring" system may be
used, in
which the temperature of the cooling load loop may be sensed over time and
compared
with the desired set point temperature. The refrigeration systems may then be
run faster
(or for a longer duty cycle) or slower (or for a shorter duty cycle) depending
on the rate
of change of the desired output parameter. In either case, the refrigeration
apparatus may
be used to attend to one load or another load,. according to load sharing
logic. For
example, it may spend 15 minutes per hour cooling one ice pad, another 15
minutes
cooling another ice pad, and 30 minutes in a non-operating condition. At other
times,
under other demand conditions, it may spend 25 minutes on each pad, with a ten
minute
dwell per hour.
Electronic controller 300 may then assess heating and cooling loads throughout
recreational facility 20. Having done so, it may determine the output heat
rejection
temperature at the thermal equalizer, and may signal the various heat load
pumps to
operate as may be required. Where there is surplus heat rejection, the
controller may
cause the closed circuit cooler to operate to soak up the extra rejected heat.
Where there
is insufficient rejected heat to meet the heating load demand, the controller
may cause the
supplemental heating element to operate to boost the temperatures in the
heating system
or systems. Where a larger amount of rejected heat is desired, and before
causing the
supplemental heating element to operate, the controller may poll the condition
of ice
reservoir 46, may check against values stored in memory for expected heating
demand,
and may, if ice reservoir 46 is not fully charged (that is, it is not at or
below its low set
point temperature, and not at the minimum temperature that can be achieve by
refrigeration apparatus 42). Provided that the time of day, and the point in
the expected
load cycle is appropriate, the controller may then signal refrigeration
apparatus 42 to
maintain a higher than otherwise high side pressure, with corresponding higher
rejection
temperature, or it may cause the compressor to run at a higher mass flow rate,
while also
causing the heating load pumps to operate at a higher flow rate, the net
result being a
greater rate of heat transfer. Adjustment of the expansion device nozzle may
also permit
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a change in upstream pressure to be obtained. That is, where a specific
thermal rejection
temperature is desired to achieve, for example, an 80 - 95 F temperature in
the radiant
space heating apparatus, the system may operate both to increase massflow rate
of the
working fluid in the refrigeration apparatus 42, but, in addition, to choke
the system to
yield a higher pressure in condensor 76 to give a combination of higher
temperature and
higher mass flow rate. This may then be accompanied by direction of coolant
from the
hot side of evaporator 88 to ice reservoir 46. In the event that greater
heating is required,
and ice reservoir 46 cannot be charged further, electronic controller may
signal for
supplemental heat at boiler 66.
In the alternate embodiment in which ice reservoir 46 and the underfloor
cooling
loops may be put in series, controller 300 may cause coolant to flow through
ice reservoir
46 and cooling loops 134 while refrigeration apparatus 42 is dormant, or while
refrigeration apparatus 42 is running at a reduced mass flow rate, until such
time as ice
reservoir 46 reaches its high set point temperature. The high set point
temperature of ice
reservoir 46 may tend to be lower than the desired ice sheet temperature by a
few degrees
F, or, alternatively, at most, may be at the desired ice sheet temperature, by
which point
ice reservoir 46 may be considered to be substantially "discharged". At this
point,
electronic controller 300 may signal for the valves to be re-positioned to
cause coolant
from the hot side of evaporator 88 to flow directly to the underfloor cooling
loops 134 as
in the usual manner. Further "discharge" of ice reservoir 46 may then also be
obtained
by setting valves 146 and 150 to admit flow from pump 280 to pass through ice
reservoir
46, thereby tending to reduce the cold side inlet temperature at condensor
cold side inlet
202. In each case, the use of ice reservoir 46 to reduce the load on
compressor 70 (either
by providing cooling directly to a load, such as an air conditioning load, and
thereby
requiring the compressor not to run for a greater period of time, or by
reducing the
condenser heat rejection inlet temperature, or by permitting an increase in
evaporator
outlet temperature) may tend to reduce the work input to the system which may
typically
be provided by either an electrical motor or by a gas or oil fired engine.
'0
In one embodiment, the refrigeration plant (i.e., the ice making equipment
lying
within the dashed lines of item 110 in Figure lb) is employed to meet at least
50 % of all
of the building heating loads of the recreational center, on a year-round
basis. In another
embodiment, heat rejection from the refrigeration plant is used to meet at
least 80 % of
the building heating loads of the recreational center. In still another
embodiment, the
McCarthy Tetrault LLP TDO-RED #8221297 v. 2
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refrigeration plant of the ice rink arena is used to meet 100 % of the
building heating
requirements, and may be used to provide surplus heat to an adjacent building
or other
facility.
Where ice reservoir 46 is used to provide cooling to the condensor side, the
freezing point of the thermal storage medium may in some circumstances be in
excess of
32 F, but less than the desired heat rejection temperature of the condenser.
In an alternate embodiment, closed circuit cooler 224 may be replaced by an
open
circuit water cooler 290. In this instance, condenser 76 may be an array of
two (or more)
plate and frame heat exchangers mounted in parallel, such that one heat
exchanger 292
may be cooled by water that is carried to an external cooling tower 294 in an
open loop
heat rejection system.
In an alternate embodiment, the compressor may be a two stage compressor with
an intermediate heat exchanger between the first and second compression
stages.
The principles of the present invention are not limited to the specific
examples
given herein by way of illustration. It is possible to make other embodiments
that employ
the principles of the invention and that fall within its spirit and scope as
defined by the
following claims.
McCarthy Tetrault LLP TDO-RED #8221297 v. 2
