U.S. patent application number 12/387776 was filed with the patent office on 2010-11-11 for method of control of thermal energy module background of the invention.
Invention is credited to Michael Burdett, Daniel Reich, Vladimir Reich.
Application Number | 20100281889 12/387776 |
Document ID | / |
Family ID | 43061521 |
Filed Date | 2010-11-11 |
United States Patent
Application |
20100281889 |
Kind Code |
A1 |
Reich; Daniel ; et
al. |
November 11, 2010 |
METHOD OF CONTROL OF THERMAL ENERGY MODULE BACKGROUND OF THE
INVENTION
Abstract
A control system measures the pressure/temperature of the
refrigerant within a Thermal Energy Module having a heat exchanger
and calculates the thickness of ice within the Thermal Energy
Module. A controller calculates an integral starting from the
moment when ice accumulation begins: I(t)=.intg.Tr(.tau.)*d.tau.
where Tr is the refrigerant saturation temperature changing with
time t. The thickness of the ice on one side of the heat exchanger
can be calculated using the following formula: X=
(2*I*K*Ui/.rho.i/ci) where Ui is the thermal conductance of ice
.rho.i is the density of the ice Ci is the latent heat of the ice K
is a correction coefficient associated with the type of the heat
exchanger.
Inventors: |
Reich; Daniel; (Tucson,
AZ) ; Burdett; Michael; (Tucson, AZ) ; Reich;
Vladimir; (Tucson, AZ) |
Correspondence
Address: |
MICHAEL BURDETT
9353 E STAR WATER DR
TUCSON
AZ
85749
US
|
Family ID: |
43061521 |
Appl. No.: |
12/387776 |
Filed: |
May 7, 2009 |
Current U.S.
Class: |
62/66 ;
700/275 |
Current CPC
Class: |
F24F 5/0017 20130101;
Y02E 60/14 20130101; Y02E 60/147 20130101; F28D 20/021 20130101;
Y02E 60/145 20130101; F28D 2020/0069 20130101 |
Class at
Publication: |
62/66 ;
700/275 |
International
Class: |
F25C 1/00 20060101
F25C001/00; G05B 15/00 20060101 G05B015/00 |
Claims
1-9. (canceled)
10. A Method of Controlling an ice formation process of a thermal
energy module, said thermal energy module comprising a tank, said
tank comprising a first heat exchanger and water, said first heat
exchanger comprising liquid refrigerant, refrigerant vapor, and a
first heat-exchange surface for exchanging heat between the water
and the liquid refrigerant, a suction line attached to the first
heat exchanger adapted to remove the refrigerant vapor from the
first heat exchanger, and a pressure sensor placed within the
suction line adapted to measure the pressure of the refrigerant
vapor, said method comprising: experimentally deriving a correction
coefficient (K) for the first heat exchanger; injecting liquid
refrigerant into the first heat exchanger; removing refrigerant
vapor from the first heat exchanger through the suction line;
forming ice on the first heat-exchange surface; measuring the
pressure of the refrigerant vapor; deriving the saturation
tempurature (Tr) of the refrigerant vapor corresponding to the
pressure of the refrigerant vapor; calculating an integral of
saturation temperature I(t) according to a first equation:
I(t)=.intg.Tr(.tau.)*d.tau., where Tr is the saturation temperature
of the refrigerant which varies with time (t) and the integral of
saturation temperature is taken over a period of time that begins
with the start of the ice formation process; calculating a
thickness of ice X(t) according to a second equation: X(t)=
(2*I(t)*K*Ui/.rho.i/ci), where Ui is a variable representing a
thermal conductance of ice, .rho.i is a variable representing a
density of ice, and ci is a variable representing a latent heat of
ice; establishing a desired thickness of ice; and suspending the
ice formation process when the calculated thickness of ice X(t)
reaches the desired thickness of ice.
11. The Method of Controlling an ice formation process of claim 10,
wherein the tank comprises a tank wall substantially parallel to
the first heat exchange surface and the desired thickness of ice is
the shortest distance from the first heat exchange surface to the
tank wall.
12. The method controlling an ice formation process of claim 10,
wherein the tank further comprises a second heat exchanger, said
second heat exchanger comprising a second heat exchange surface
substantially parallel to the first heat exchange surface and the
desired thickness of ice is half the distance between the first
heat exchange surface and the second heat exchange surface.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to cold and hot thermal energy
storage systems as well as using such systems to optimize and
reduce the electric and natural gas energy consumption of a
building. In particular, this invention relates to a method of
controlling the operation of a thermal energy storage device
including a novel method of calculating the thickness of
accumulated ice within the device.
[0003] 2. Description of the Prior Art
[0004] Improving the energy efficiency of building comfort systems
has become progressively more important due to rising energy costs
as well as increased awareness and concern over global warming as a
result of humanity's rising consumption of carbon fuels for
electrical energy generation, direct burn heating, and domestic hot
water appliances. One area where these concerns can be addressed is
through leveling demand by shifting some of the load during peak
hours of a day to off-peak times, thereby eliminating the need to
build and run expensive peak generator turbines. These turbines are
costly to build, install and operate and are typically used for
only a very limited number of hours during the hottest days of the
year. This invention addresses these concerns by increasing the
efficiency of building comfort systems and helping to control
electricity demand while increasing the general comfort level in
the installed facilities.
[0005] Demand control and increased efficiency is primarily
accomplished by shifting the burden of cooling from the hottest
time of the day to the night when ambient temperatures as well as
demand are considerably lower. Refrigeration equipment efficiency
increases when the temperature lift requirement decreases. The
difference in temperature lift between a hot day and a cool night
can often be as high as 50%, thereby resulting in a massive drop in
refrigeration equipment lift requirements and a corresponding
efficiency increase. The problem is typically this equipment is
required to operate during the day, due to the lack of
cost-effective, efficient energy storage. And worse yet, the
resulting demand in electricity consumption peaks requiring the use
of low-efficiency gas turbine peak generators. The efficiency of
these generators are generally 40-50% lower than good steam
turbines which generate most of our electricity. Reducing or
eliminating these peaks can be accomplished by storing energy for
later use, and is the basic principle of Thermal Energy Storage
(TES) technology. By storing cold water or ice during off-peak
"cool hours" and then using this thermal energy to cool a facility
during peak times will considerably reduced power consumption from
the grid as well as helping to balance generating loads over a
24-hour period. In the same respect, hot water can also be
generated during the daytime using, for example, solar and stored
for later use in domestic hot water or nighttime heating.
[0006] While there are different types of thermal storage systems
on the market the most common designs are based on cold water or
two-phase ice/water storage. In recent years the ice storage
systems have increased in popularity due to a considerably higher
energy storage density. Currently ice storage systems are commonly
used in large buildings and campuses. Such systems will generally
contain chillers which cool a secondary heat transfer media such as
brine to temperatures lower than water freezing temperatures. The
brine circulates through tubes in ice storage tanks and cools water
thereby generating ice. These systems are very complex, bulky,
expensive and difficult to scale down for use in small commercial
buildings or residential applications.
[0007] More recently a different approach to ice storage systems
design was introduced. These systems generate ice through direct
expansion of the refrigerant in a coil submerged in a tank of
water. When it is time to use the accumulated cold energy the coil
serves as a condenser in a secondary refrigerant loop where it
condenses the refrigerant evaporated in an air conditioning unit
coil. These types of systems are better suited for smaller
buildings but they too suffer from being too complex, expensive and
bulky for small businesses and homes. Moreover, such systems do not
provide a high level of comfort due to their inherent deficiency of
controlling temperature by cycling the system on and off. Also,
these direct expansion systems can be used only for cooling
purposes and are very difficult or impossible to combine with solar
heating solutions which are becoming increasingly more important in
energy conservation strategies.
SUMMARY OF THE INVENTION
[0008] The present invention overcomes the disadvantages and
limitations of the prior arts by providing a means of storage for
not only cold, but also hot water energy which can be generated by
solar heaters. Another advantage is that the proposed design is
capable of a very high level of energy efficiency by retaining the
extracted heat energy and reusing it for heating or hot water use,
rather than dissipating this energy from the premises into the
atmosphere as in most prior arts. The system is also capable of
providing a considerably higher level of comfort over previous
designs by gradually modulating the cooling and heating capacity
and maintaining accurate temperature set points.
[0009] The main part of the invention is the Thermal Energy Module
(TEM) comprising of an insulated flat tank with a flat heat
exchanger located inside. The heat exchanger is comprised of two
manifolds at the top and one at the bottom of the tank connected to
a micro channel or pipe-in-plate panel which allows refrigerant
liquid and vapor to move from the inlet manifold through the plates
or channel down to the bottom manifold and then back up to the
outlet manifold. The heat exchanger is located at the center
section of the tank and its width is designed to prevent the water
on the both sides of the tank from freezing during the ice
generating process thereby providing pockets of unfrozen water
where water jet generating inlet pipes are located. Both water jet
pipes are connected to a manifold located at the top of the tank.
The bottom of the tank contains a water outlet manifold. The heat
exchanger also can be located in the tank in a way that its
manifolds are located on the sides and the refrigerant is flowing
horizontally. Top and bottom water manifolds are located inside
insulation to prevent the water from freezing. Instead of water,
other two-phase liquids can be used in this invention. The total
thickness of the TEM tank can be made shallow enough to enable its
incorporation inside wall framing of a typical building. Multiple
TEMs can be built in array(s) in a wall or walls simultaneously
serving as wall insulation. TEMs in an array can simultaneously
work in different modes at any moment in time.
[0010] A control system measures the pressure/temperature of the
refrigerant and calculates the thickness of the ice. A controller
calculates an integral starting from the moment when ice
accumulation begins: I(t)=.intg.Tr(.tau.)*d.tau. where Tr is the
refrigerant saturation temperature changing with time t. The
thickness of the ice on one side of the heat exchanger can be
calculated using the following formula: X= (2*I*K*Ui/.rho.i/ci)
where Ui is the thermal conductance of ice .rho.i is the density of
the ice Ci is the latent heat of the ice K is a correction
coefficient associated with the type of the heat exchanger
(experimentally derived).
[0011] Various other purposes and advantages of the invention will
become clear from its description in the specification that follows
and from the novel features particularly pointed out in the
appended claims. Therefore, this invention comprises the features
hereinafter illustrated in the drawings, fully described in the
detailed description of the preferred embodiments, and particularly
pointed out in the claims. However, such drawings and description,
as well as this Summary of the Invention, disclose just a few of
the various ways in which the invention may be practiced and are
not limiting on the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1A is an illustration of a cross section of an
embodiment of the Thermal Energy Module in ice formation and in ice
harvesting mode.
[0013] FIG. 1B is an illustration of the horizontal cross section
of the Thermal Energy Module of FIG. 1A in ice formation mode.
[0014] FIG. 1C is an illustration of the horizontal cross section
of FIG. 1B in cold harvesting mode.
[0015] FIG. 2 is an illustration of the Thermal Energy Module of
FIG. 1 A configured to work in condenser mode.
[0016] FIG. 3A is an illustration of an array embodiment of a
plurality of Thermal Energy Modules of FIG. 1A.
[0017] FIG. 3B is an illustration of the array embodiment of FIG.
3A showing ice growth among parallel heat exchangers.
[0018] FIG. 4 is an illustration of an air conditioning system with
energy storage using Thermal Energy Modules.
[0019] FIG. 5 is a graph of the changes in suction temperature and
pressure at the exit of a TEM heat exchanger and ice thickness over
time.
[0020] FIG. 6 is a graph of ice formation in multiple Thermal
Energy Modules which are connected in parallel with respect to a
refrigeration circuit through electrical expansion valves.
[0021] FIG. 7 is an illustration of a cooling and heating system
which utilizes a plurality of Thermal Energy Modules, some for
cooling and some heating applications.
[0022] FIG. 8 is an illustration of a Thermal Energy Module
utilized for thermal energy storage in domestic hot water
heating.
[0023] FIG. 9 is an illustration of the application of a Thermal
Energy Module within the wall framing of a building.
[0024] FIG. 10 is an illustration of a Direct Expansion system
utilizing Thermal Energy Module ice storage and a water source heat
exchanger.
DESCRIPTION OF THE INVENTION
[0025] The present invention is a means of storage for cold water
(or similar energy transfer medium), ice, or hot water which may be
generated by solar heaters wherein the means of storage allows for
the ability to control demand and achieves a high level of energy
efficiency by retaining extracted heat energy and reusing it for
heating or generating hot water.
[0026] The present invention is a Thermal Energy Module comprising
a tank and a flat heat exchanger. The heat exchanger is comprised
of an intake manifold, a pass-through manifold, and an outlet
manifold connected via micro-channel, pipe-in-plate panel, or
similar thermal energy transfer structures which allow refrigerant
liquid and vapor to move from the inlet manifold though a first
energy transfer structure to the pass-through manifold and then
through a second energy transfer structure to the outlet manifold.
The heat exchanger is located within a tank and its size relative
to the tank is designed to prevent ice from forming within a pocket
or channel on at least one side of the tank during the ice
generating process thereby providing a non-freezing space wherein
water inlet pipes are located. These water inlet pipes are
connected to a water inlet manifold. The Thermal Energy Module also
includes a water outlet manifold tasked with collecting water that
has been introduced into the tank via the water inlet manifold and
water inlet pipes. Alternatively, the non-freezing space may
comprise an insulating material to prevent the water within the
water inlet manifold, the water outlet manifold and the water inlet
pipes from freezing. In alternate embodiments of the invention,
other thermal transfer liquids may be utilized instead of
water.
[0027] The total thickness of the Thermal Energy Module tank can be
made shallow enough to enable its incorporation inside wall framing
of a typical building. Multiple Thermal Energy Modules can be built
in an array in a wall or walls and simultaneously serve as wall
insulation. Different Thermal Energy Modules within an array can
simultaneously work in different modes at any moment in time, i.e.,
some of the Thermal Energy Modules may be generating cold water or
ice while other Thermal Energy Modules are storing heat, possibly
even the heat generated from the process of generating the cold
water or ice.
[0028] Referring to figures, wherein like parts are designated with
like reference numerals and symbols, FIG. 1A is an illustration of
a cross section of an embodiment of the Thermal Energy Module 98 in
ice formation and in ice harvesting mode comprising a relatively
flat, thermally insulated tank 102 filled with water, ice, or
similar heat transfer medium such as an alternate two-phase
substance. A heat exchanger 106 comprising a first energy transfer
structure 105 and a second energy transfer structure 107 is located
within the tank 102. The heat exchanger 106 includes an first
manifold 101 and a second manifold 201 which may be connected in
series with an external vapor-compression refrigeration loop (not
shown) and may be utilized as either as an evaporator or a
condenser. In this embodiment of the invention, the first manifold
101 is connected to a pass-through manifold 108 via a first energy
transfer structure 105 such as a micro-channel or pipe-in-plate
panel and the pass-through manifold 108 is connected to the second
manifold 201 via a second energy transfer structure 107.
Alternatively, the invention may be practiced by omitting the
pass-through manifold 108 and connective the first manifold 101 to
the second manifold 201 via a single energy transfer structure
105.
[0029] As indicated, the energy transfer structure 105 may comprise
an aluminum microchannel extrusion or similar structure. The
function of the first manifold 101 and the second manifold 201 are
interchangeable. In other words, the flow of refrigerant through
the heat exchanger 106 may be from the first manifold 101 to the
second manifold 201 or vice-versa. During this process the
refrigerant exchanges heat with water, cooling it or converting it
into ice when it functions as an evaporator, or heating water when
it functions as a condenser.
[0030] One or more water inlet pipes 112 are also located within
the tank 102. These water inlet pipes have nozzles 103 tasked with
introducing water or similar material into the portion of the tank
102 occupied by the heat exchanger 106. In this embodiment of the
invention, the water inlet pipes 112 are located in pockets of
water where ice is not allowed to form. These water inlet pipes 112
are connected to a water inlet manifold 100 which can, in turn, be
connected to an external water system (not shown) through
connectors on the end(s). The tank 102 also contains a water outlet
manifold 109 with connectors on the end(s) that collects water from
the tank 102. In this embodiment of the invention, the water inlet
manifold 100 and the water outlet manifold 109 are located inside
the tank walls 99. In this application of the invention, it is
advantageous that the tank walls 99 be thermally insulated to
prevent the water inlet manifold 100 and the water outlet manifold
109 from freezing during the ice formation process as well as
minimizing the heat exchange (energy loss) of the water with the
outside environment. The water inlet manifold 100 and the water
outlet manifold 109 may include caps 110 when only one external
water loop is connected to the Thermal Energy Module.
[0031] FIG. 1B is an illustration of the horizontal cross section
BB of the Thermal Energy Module for FIG. 1A in ice formation mode.
In this embodiment of the invention, the simple shape of the heat
exchanger (a uniform plate with a relatively constant temperature
across the flat areas) makes the ice formation process relatively
simple, predictable and susceptible to mathematical analysis, and
as a result can be easily controllable. This figure shows the state
of the Thermal Energy Module when the ice 104 reaches the tank
walls 99. The formation of the ice on the flanges of the heat
exchanger is much slower than in the direction perpendicular to the
flat plan of the heat exchanger thereby preventing the freezing of
the inlet water pipes 112.
[0032] FIG. 1C is an illustration of the horizontal cross section
of FIG. 1B in cold harvesting mode. Water jets formed by nozzles
103 create water turbulence 111 which facilitates thawing of the
ice 105 and mixing water before exiting through the water outlet
manifold 109.
[0033] FIG. 2 is an illustration of the Thermal Energy Module of
FIG. 1A configured to work in condenser mode. The heat exchanger
106 is connected to an external liquid-vapor loop (not shown) as a
condenser. Hot gas from a compressor (not shown) flows into the
heat exchanger 106 through the first manifold 101 and is cooled by
the surrounding water 113 and condensed into liquid which exits
through the second manifold 201. Cold water enters the Thermal
Energy Module 98 through the water inlet manifold 100, the water
inlet pipes 112, and the nozzles 103 which generate water jets
washing over the heat exchanger 106. The warm water leaves the
Thermal Energy Module through the outlet manifold 109.
[0034] While the Thermal Energy Module is in ice generation mode,
the tank 102 is filled with water 113 and the water supply (via the
water inlet manifold 100) is shut off. The first manifold 101 of
the heat exchanger 106 is connected to an external refrigeration
system (not shown) through an expansion device. Liquid refrigerant
is injected into the heat exchanger 106 and, during expansion, it
partly evaporates into a mixture of liquid and vapor and which
reduces its temperature. In this embodiment of the invention, the
desired temperature is one below the freezing point of water 113
and ice formation begins. As the ice 104 thickness increases so
does the thermal insulation between the heat exchanger 106 and
water 113, thereby reducing the heat transfer from water to the
refrigerant. As a result, refrigerant pressure and temperature
decreases which effectively sustains the ice growth. A control
system (not shown) measures the pressure/temperature of the
refrigerant and calculates the thickness of the ice.
[0035] A sample algorithm for this calculation is as follows:
[0036] The controller calculates the integral starting from the
moment when ice accumulation begins: I(t)=.intg.Tr(.tau.)*d.tau.
where Tr is the refrigerant saturation temperature changing with
time t. The thickness of the ice on one side of the heat exchanger
can be calculated using the following formula: X=
(2*I*K*Ui/.rho.i/ci) where Ui is the thermal conductance of ice
.rho.i is the density of the ice Ci is the latent heat of the ice K
is a correction coefficient associated with the type of the heat
exchanger (derived experimentally).
[0037] When the X value reaches the value of the distance from the
vertical plane of the heat exchanger 106 from the tank wall 99, the
ice formation process can be suspended. In this embodiment of the
invention, the growth of ice on non-planar sides of the heat
exchanger is much slower than in the direction perpendicular to its
planar surface. This allows retaining pockets of unfrozen water
where the water inlet pipes 112 are located. Additionally, these
pockets of water prevent the buildup of pressure inside the ice to
levels that could damage the heat exchanger and/or tank
integrity.
[0038] When used as a water cooler, the first manifold 101 of the
heat exchanger 106 of the Thermal Energy Module 98 is connected to
an external refrigeration system (not shown) through an expansion
device (not shown). An external water inlet valve (not shown) is
opened allowing water to enter the Thermal Energy Module 98 via the
water inlet manifold 100. Jets of water wash over the heat
exchanger 106 thereby transferring heat from the water 113 to the
refrigerant (not shown) located within the heat exchanger. Cooled
water exits through the water outlet manifold 109. A controller
(not shown) measures the temperature of the water leaving the water
outlet manifold 109 and controls the refrigerant flow to keep the
temperature of the water 113 at the set point within the tank 102
and above its freezing point to prevent ice formation.
[0039] A Thermal Energy Module 98 in water cooler mode can work in
parallel with one or more other Thermal Energy Modules (not shown)
working in ice formation mode. In such an embodiment, when water in
the first Thermal Energy Module drops to a low set point the
refrigerant flow to its heat exchanger 106 is suspended and the
refrigerant flow to ice generating Thermal Energy Modules is turned
on. The ice generation proceeds until the temperature measured in
the outlet pipe of the first Thermal Energy Module rises to a high
set point at which time the refrigerant flow is returned to the
first Thermal Energy Module. This sequence can go on until the ice
reaches the desired thickness or the requirement for cooling ends.
One of the advantages of this mode of operation is that the
compressor in the refrigeration system works with reduced cycling
which increases the efficiency of the system.
[0040] When operating in the harvesting cold mode, the flow of
refrigerant to the Thermal Energy Module heat exchanger 106 is
turned off. The water inlet valve 100 is opened and water jets
start thawing the ice and cooling the water 113. The cooled water
exits through the water outlet manifold.
[0041] When operating in hot water storage mode, the flow of
refrigerant to the Thermal Energy Module heat exchanger 106 is
turned off. The water inlet manifold 100 and the water outlet
manifold 109 is connected in series with an external hot water
source (not shown) such as a solar panel. The secondary loop to the
Thermal Energy Module is capped 110. Hot water is circulated
through the Thermal Energy Module gradually raising its
temperature. When the temperature is raised to the temperature of
the external hot water source, or it reaches a high temperature set
point, water flow is interrupted.
[0042] It is interesting to note that Thermal Energy Modules in hot
storage mode can work in tandem with Thermal Energy Modules in ice
formation mode. Such a system is capable of providing cooling
during the day and heating during the night.
[0043] In hot water energy harvesting mode, the flow of refrigerant
to the Thermal Energy Module heat exchanger 106 is turned off. The
water inlet manifold 100 and the water outlet manifold 109 are
connected in series to an external hot water source (not shown)
such as a solar panel creating a primary loop. These manifolds are
also connected in series with an external heat sink (not shown)
such as the water coil of an air conditioning unit creating a
secondary loop. The flow through the secondary loop is regulated to
provide adequate heating input to an air-conditioning unit or
similar device. Both loops can work simultaneously enabling the
Thermal Energy Module to act as a buffer as well as thermal energy
storage. Alternatively, the primary loop can be shut off.
[0044] While operating as a water source condenser, the refrigerant
inlet manifold 101 and the refrigerant outlet manifold 201 are
connected in series to an external refrigeration loop (not shown)
after a compressor comprised within the refrigeration loop. Water
manifolds 100 and 109 are also connected in series to a loop with a
heat sink such as a cold water supply. Hot, compressed refrigerant
transfers heat to the water loop while simultaneously being
condensed within the heat exchanger 106. The heat transferred to
the water loop can be used as preheat for a domestic hot water
supply or as a heat source for space heating in forced air or
radiant floors systems.
[0045] The Thermal Energy Module 98 may also be used in a Direct
Expansion cooling system. In such an embodiment, the refrigerant
loop of an external water cooled condenser (not shown) is connected
in series after the external air cooled condenser (not shown). The
refrigerant loop of the Thermal Energy Module is connected in
parallel with the Direct Expansion coil of the air conditioning
unit. An external water pump (not shown) circulates water between
the TEM and the water loop of the heat exchanger. Expansion valves
turn on and control the evaporation in the TEM or in the AC unit's
heat exchanger. During off-peak hours the AC unit cools the space
to the set point and when the set point is reached the cooling is
switched to the TEM. Ice accumulation then begins. During peak
hours the water pump is turned on circulating cold water through
the water-source condenser. As a result refrigerant is condensed at
a considerably lower temperature than that of air-source
condensers. This process increases energy efficiency of the system
and reduces demand.
[0046] FIG. 3A is an illustration of an Thermal Energy Module Array
198 utilizing a plurality of heat exchangers 106 within a single
tank 102. FIG. 3B is an illustration of the embodiment of FIG. 3A
showing ice growth among parallel heat exchangers 106.
[0047] FIG. 4 is an illustration of an air conditioning system 298
with energy storage using Thermal Energy Modules 98. The system
consists of a condensing unit 402 comprising of a compressor 403,
condenser 401 which is cooled by an air stream 406, and refrigerant
receiver 400. The condenser is connected to the heat exchangers of
the Thermal Energy Modules 98 by tubing. Expansion devices 408 are
installed on the supply side of the heat exchangers. In this
embodiment of the invention Electrical Expansion Valves are used as
expansion devices which have the ability to completely prevent
refrigerant flow when closed. On the common outlet manifold 407 a
pressure sensor 404 is installed. The refrigerant inlet and outlet
temperatures on each Thermal Energy Module are measured
respectively by temperature sensors 405 and 421. These temperature
sensors are used by the control system to control the refrigerant's
rate of flow to maintain superheat levels which prevent the liquid
refrigerant from leaving the heat exchangers in the Thermal Energy
Module units while keeping them as full of a liquid-vapor mixture
as possible.
[0048] On the water side all Thermal Energy Modules are connected
in parallel to the water loop 424 which includes a circulating pump
416 and a balancing valve 415. The supply pipe of the loop has a
temperature sensor 426. Control valves 413 are installed on the
inlet side 412 of the Thermal Energy Modules 98. The Thermal Energy
Module outlets 414 have temperature sensors 420. The temperature
sensors are used by the control system to regulate the control
valves to put each Thermal Energy Module in one of the possible
modes and control the temperatures to achieve the desired cooling
effects. The heat exchanger of the air handling unit 419 is
connected to the water loop through a bridge 425. A variable rate
pump 417 removes the necessary quantity of heat from the air
handling unit heat exchanger to cool the air and maintain the space
temperature set point measured by the space temperature sensor 423.
The removed heat is injected into the loop by pump 417. An
expansion tank 418 creates a constant pressure in the entire
hydronic system and compensates for thermal water expansion and
contraction.
[0049] In this embodiment, all three Thermal Energy Modules 98 can
work in the same ice accumulation mode or in different modes. For
example, the first couple of Thermal Energy Modules may work in ice
generating mode while the third Thermal Energy Module works in
cooling mode. In this case, valves 413 on the first couple of
Thermal Energy Modules are closed and the third Thermal Energy
Module is open. Water propelled by pump 416 flows only through the
third Thermal Energy Module. Initially the Electrical Expansion
Valve 408 on the first couple of Thermal Energy Modules are closed
and the Electrical Expansion Valve 408 on the third Thermal Energy
Module controls refrigerant flow using superheat information from
temperature sensors 405 and 421. Water washes over the heat
exchanger transferring heat to the liquid refrigerant and
evaporating it. Cooled water exits the third Thermal Energy Module
and flows through water loop 424. When the temperature in the water
loop 424 measured by temperature sensor 426 drops to the low set
point, valve 408 on the third Thermal Energy Module is closed and
valves 408 on the first two Thermal Energy Modules start
controlling refrigerant flow to their heat exchangers using the
superheat information from the pressure sensor 404 and temperature
sensor 405 thereby starting or resuming ice formation. The first
couple of Thermal Energy Modules may also work simultaneously or
sequentially in ice formation mode. In the latter case valve 408 on
the second Thermal Energy Module is closed until ice formation
process is complete in the first Thermal Energy Module. This mode
of operation will considerably decrease cycling of the compressor
thus increasing its life span and efficiency of the system.
[0050] When a command to reduce electrical demand is received by
the system but there is still a requirement for cooling, the
compressor is turned off, and valves 408 are turned off on all
Thermal Energy Module units. Valves 413 are modulated to control
water flow thereby controlling the outlet temperature measured by
the temperature sensors 420 and 426. The balancing valve 415 is
controlled to maintain the water flow through the loop 424
constant.
[0051] FIG. 5 is a graph of the changes in suction temperature and
pressure at the exit of a TEM heat exchanger and ice thickness over
time. In this embodiment, ice formation usually starts at
temperatures of -5.degree. C. for R410A refrigerant. The ice
thickness starts growing very quickly which creates a thermal
insulation layer on the heat exchanger surface. As the result, the
heat transfer from the water in the tank to the refrigerant drops,
the expansion valve closes reducing refrigerant flow and the
saturation temperature and pressure drops accordingly. The drop in
temperature of the heat exchanger assures further growth of the
ice. The process of ice formation will stop only when the
temperature drops to a level where the low pressure switch in the
suction line is activated thereby turning off the compressor.
[0052] The ice thickness in the direction perpendicular to the
planar surface of the heat exchanger at any particular moment (t)
can be calculated if the historical data of temperatures of the
surface Tr(.tau.) up to this moment is known. Then an integral can
be calculated by the control system: I(t)=.intg.Tr(.tau.)*d.tau.
where Tr is close to the refrigerant saturation temperature
changing with time .tau.. The integral is calculated in the process
of ice grow from the moment .tau.=0.
[0053] The thickness of the ice on one side of the heat exchanger
can be calculated using the following formula: d=
(2*I(t)*K*Ui/.rho.i/ci) where Ui is thermal conductance of ice,
.rho.i is density of ice, Ci is latent heat of ice, K is a
correction coefficient associated with the type of the heat
exchanger (derived experimentally)
[0054] FIG. 6 is a graph of ice formation in multiple Thermal
Energy Modules which are connected in parallel with respect to a
refrigeration circuit through electrical expansion valves. The
water flow to each Thermal Energy Module is shut off. At the start
of the process Electrical Expansion Valves of the second and third
Thermal Energy Modules are shut off and the Electrical Expansion
Valve of the first Thermal Energy Module starts to modulate to
maintain the superheat set point. The ice in the Thermal Energy
Module starts growing, the thickness increases thereby increasing
the thermal resistance and decreasing the saturation pressure and
the temperature. When the suction pressure measured by the pressure
sensor 204 drops to the set point, the Electrical Expansion Valve
208 of the second Thermal Energy Module starts modulating ice
growth within the second Thermal Energy Module. The process
continues, similar to what was described for the first Thermal
Energy Module except for the fact that the process of ice growth
continues when the second and third Thermal Energy Modules are
staged on.
[0055] FIG. 7 is an illustration of a cooling and heating system
which utilizes a plurality of Thermal Energy Modules 98, some for
cooling and some heating applications. The cooling portion of the
system can operate similarly to the one described in FIG. 2. For
heating, Thermal Energy Module heat exchangers are connected in
parallel to the condenser 701 of the condenser block 702. The
solenoid valves 728 facilitate the selection of the regular
condenser 701 or the Thermal Energy Module heat exchangers for
condensing the refrigerant hot gas exiting the compressor 703.
However, both valves 728 can be opened to achieve additional sub
cooling of the liquid refrigerant for increasing the efficiency and
capacity of the cooling system.
[0056] Each Thermal Energy Module heat exchanger has a solenoid
valve which allows controlling the condensing capacity by
connecting from 1 to 3 Thermal Energy Modules in the refrigeration
circuit. One hydronic circuit of the heating TEM units is connected
to the thermal solar system 738. This system consists of a vacuum
tube or plate type solar collector 725, hydronic manifold 723, and
a circulating pump 726. When the pump 726 is on, the water (or
other heat transferring liquid) circulates through the Thermal
Energy Modules heating the volume of water to the temperature
generated by the solar system. If the temperature in the Thermal
Energy Module tanks reaches the design temperature (which can be up
to 100.degree. C. or higher) or if the temperature in the tanks
exceeds the temperature generated by the solar system, the pump is
turned off.
[0057] Refrigeration and solar heating can work sequentially, for
example, refrigerant heating can work during night time when the
cooling system is in ice generating mode, effectively moving energy
from the first three Thermal Energy Modules to the last three
Thermal Energy Modules. In this mode the temperature in the last
three Thermal Energy Modules can reach 40.degree. C. or higher.
These temperatures are adequate for low temperature heating, for
example, radiant floors.
[0058] The other hydronic circuit of the heating TEM units is
connected to the main water loop 732 through the heating control
valves. If cooling control valves 713 are closed and one or more
heating control valves 739 are regulating the system, then it is in
heating mode. Hot water is circulated in the main loop by the main
circulating pump 716. The local circulating pumps 717 extract heat
from the loop, circulating water through the coils of the air
conditioning units 719 and 720. During the winter time when cooling
is not required and the solar heating system is capable of
generating high temperatures, all Thermal Energy Modules can be
switched to heating mode. In this mode the condensing unit 702 is
turned off, control valves 713 and 739 are open and the pump 716
circulates water through the main loop of all the Thermal Energy
Modules, effectively transferring thermal energy from units the
last three Thermal Energy Modules to units to the first three.
During a sunny winter day the system may store enough thermal
energy in this mode to heat the building during the night time.
[0059] FIG. 8 is an illustration of a Thermal Energy Module
utilized for thermal energy storage in domestic hot water heating.
The system has valves 841 and 842 installed on the solar heating
loop. These valves can direct hot water from the solar panel 825 to
Thermal Energy Modules for space heating or to the sixth Thermal
Energy Module for domestic hot water system. The domestic hot water
pump circulates water through the sixth Thermal Energy Module and
the heat exchanger 824 preheating from the cold water main 830
before it feeds into the water heater 827. Hot water from the water
heater 827 then flows to the domestic hot water distribution system
831. The sixth Thermal Energy Module can be installed without a
refrigerant heat exchanger.
[0060] FIG. 9 is an illustration of the application of a Thermal
Energy Module within the wall framing of a building. In this case
the Thermal Energy Modules also serve as thermal insulation for the
building. All the voids between the Thermal Energy Modules should
be filled with standard insulation.
[0061] FIG. 10 is an illustration of a Direct Expansion system
utilizing Thermal Energy Module ice storage and a water source heat
exchanger. Also this system has two Electrical Expansion Valves 008
and 015 which direct and control liquid refrigerant from the
receiver 017 to the Thermal Energy Module evaporator or the heat
exchanger of the AC unit 019. The water loop transfers heat from
water cooled condenser 013 to the TEM by a water pump 016. The
expansion tank 018 maintains constant pressure in the water
loop.
[0062] During normal operation the water pump 016 is off and all
the condensing of the refrigerant exiting the compressor 003 is
performed by the air cooled condenser 001. Liquid refrigerant from
the condenser 001 moves through the heat exchanger and into the
receiver 017. When the thermostat 023 calls for cooling the
Electrical Expansion Valve 015 opens and starts controlling the
refrigerant flow to maintain the superheat set point in the AC heat
exchanger. When the thermostat 023 is satisfied, refrigerant flow
through the AC heat exchanger is stopped by the Electrical
Expansion Valve 015 and another Electrical Expansion Valve 008
opens and starts controlling the flow through the Thermal Energy
Module evaporator. The ice production then begins or continues.
This process of alternating space cooling and ice production can
persist until the Thermal Energy Module(s) is completely charged or
the demand reduction request is received.
[0063] In demand reduction mode, pump 016 starts and varies the
rate of flow to control the heat exchanger outlet temperature at
set point. The Electrical Expansion Valve 008 is shut down. The
high temperature refrigerant exiting the compressor 013 passes
through the main condenser desuperheating but without condensation.
Condensation occurs in the water source condenser 013. On a hot
summer day the condensation temperature after the water source heat
exchange can be as low as 10-15.degree. C. in comparison with
50-55.degree. C. after the air source condenser. Respective
refrigeration cycle efficiency can be increased fivefold. The
energy consumption will also reduce respectively.
[0064] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. All changes
which come within the meaning and range of equivalency of the
claims are to be embraced within their scope.
* * * * *