WO2011041767A1

WO2011041767A1 - Heat pump water heater having a sub-cooling arrangement

Info

Publication number: WO2011041767A1
Application number: PCT/US2010/051242
Authority: WO
Inventors: Yoav Ben-Yaacov; Ori Asher; Amir Harel; Shalom Lampert; Harold Wiener
Original assignee: Phoebus Energy Ltd.
Priority date: 2009-10-02
Filing date: 2010-10-03
Publication date: 2011-04-07
Also published as: WO2011041768A3; WO2011041768A2

Abstract

A system for supplying heated water to a consumer, including: a first heat exchanger, fluidly communicating with a refrigerant circulation pipe, and adapted to effect an indirect exchange of heat between a first flow of water and a compressed refrigerant gas, to heat the first flow of water, and to condense the gas into a refrigerant fluid including a refrigerant liquid; a second heat exchanger, fluidly communicating with the pipe, and adapted to effect an exchange of heat between a second refrigerant liquid and a heat source, whereby a second refrigerant gas is produced; a compression arrangement, associated with the pipe, adapted to compress the second gas to produce the compressed gas; a tank adapted to operate at a superatmospheric temperature, and to provide a heated flow of water for the consumer.

Description

Heat Pump Water Heater having a Sub-Cooling Arrangement

This application draws priority from U.S. Provisional Patent Application Serial No. 61/247,962, filed October 2, 2009, which is incorporated by reference for all purposes as if fully set forth herein.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to heat pump water heaters, and more particularly, to a heat pump water heater having a sub-cooling and/or a pre- heating arrangement, and a method of operating the heater.

A typical heat pump works between two heat sinks. In a heat pump water heater, the first sink may be ambient air, which transfers energy to the refrigerant fluid in the evaporator. The second sink may be hot water, which is further heated by the refrigerant fluid in the condenser.

In facilities such as hotels, hospitals, sports centers, etc., hot water is constantly circulated between a storage tank and the heater, in a first circulation loop, and between the storage tank and the water consumers, in a second circulation loop. These circulation loops may be used to make a hot water supply readily available to relatively distant consumers. To this end, the second heat sink mentioned above (i.e., the hot water) is stored in a tank in which is maintained a relatively narrow temperature range, typically 45°C - 65°C.

In a typical heat pump water heater, a Freon® (one or more of a family of fluorinated hydrocarbons used as refrigerants) or another refrigerant is evaporated in the evaporator, in a relatively low pressure, accumulating energy from the ambient air in the form of latent heat. The Freon® is then compressed, the temperature typically rising in the process to about 55°C - 75 °C. In the condenser, water is heated (typically from 40°C - 55°C to 45 °C - 65 °C) drawing the latent heat energy from the gaseous Freon®. The condensed Freon®, which may typically have a temperature of 40°C - 70°C, is then passed through an expansion valve, lowering its pressure and cooling the Freon® to (typically) ~ - 5°C - 25°C.

A successful approach to heat pump water heating systems is provided in our PCT Patent Application No. WO/2010/058397, which is incorporated by reference for all purposes as if fully set forth herein.

We have recognized a need for further improvements in heat pump water heater systems, and in methods of constructing and operating such systems, and the subject matter of the present disclosure and claims is aimed at fulfilling this need.

SUMMARY OF THE INVENTION

According to the teachings of the present invention there is provided a heat pump water heating system for supplying heated water to at least one consumer, the system including: (a) a first heat exchanger, fluidly communicating with a refrigerant circulation pipe, and adapted to effect an indirect exchange of heat between a first flow of water and a compressed refrigerant gas, to heat the first flow of water, and to condense the compressed refrigerant gas into a refrigerant fluid including a refrigerant liquid; (b) a second heat exchanger, fluidly communicating with the circulation pipe, and adapted to effect an exchange of heat between a second refrigerant liquid and a heat source, whereby a second refrigerant gas is produced; (c) a compression arrangement, associated with the circulation pipe, adapted to compress the second refrigerant gas to produce the compressed refrigerant gas; (d) a storage tank adapted to operate at a superatmospheric temperature, and to provide a heated flow of water for the consumer; (e) a circulation arrangement adapted to circulate the first flow of water to the first heat exchanger, and after being heated therein, to return the first flow of water to the storage tank or to the consumer, and (f) a third heat exchanger, having a first flow path fluidly communicating with the circulation pipe, and a second flow path, fluidly sealed with respect to the first flow path, and adapted to receive and discharge a second flow of water, the flow paths juxtaposed to effect an indirect exchange of heat between the refrigerant fluid and the second flow of water, the second flow of water adapted to have a temperature below a temperature of the first flow of water, whereby the refrigerant fluid undergoes sub-cooling to produce the second refrigerant liquid, and whereby the second flow of water is heated to produce a heated second flow of water.

According to further features in the described preferred embodiments, the compression arrangement includes at least one compressor adapted to be electrically connected to a power supply and to fluidly communicate with the circulation pipe, the compressor adapted to compress the second refrigerant gas to produce the compressed refrigerant gas.

According to still further features in the described preferred embodiments, the system further includes an expansion valve, fluidly communicating with the circulation pipe and adapted to reduce a pressure and a temperature of the refrigerant liquid to produce the second refrigeration liquid.

According to still further features in the described preferred embodiments, the system further includes a recirculation loop fluidly communicating with the second flow path of the third heat exchanger, whereby at least a portion of the heated second flow of water is recirculated via the loop to an inlet of the second flow path.

According to still further features in the described preferred embodiments, the system further includes a buffer tank fluidly communicating with the second flow path of the third heat exchanger.

According to still further features in the described preferred embodiments, an inlet of the second flow path fluidly communicates with a grid water pipe.

According to still further features in the described preferred embodiments, an inlet of the second flow path fluidly communicates with, and is directly connected to, a grid water pipe.

According to still further features in the described preferred embodiments, an outlet of the second flow path is adapted to discharge at least a portion of the second flow of water to the buffer tank.

According to still further features in the described preferred embodiments, an outlet of the second flow path is adapted to discharge at least a portion of the second flow of water to the circulation arrangement.

According to still further features in the described preferred embodiments, the system further includes at least one sensor adapted to provide a temperature indication in at least one location within the heating system.

According to still further features in the described preferred embodiments, the system further includes at least one sensor adapted to perform a measurement of at least one system parameter including information pertaining to at least one flowrate within the heating system.

According to still further features in the described preferred embodiments, the system further includes sensors, each adapted to provide a temperature indication, the sensors disposed in at, or proximate to, at least two, at least three, or all four of the following locations: an inlet to the first flow path; an outlet to the first flow path; an inlet to the second flow path; an outlet to the first flow path.

According to still further features in the described preferred embodiments, the system further includes a processor adapted to receive at least one input including the temperature indication or the measurement, and to control an operation of the heat pump water heating system based on the input.

According to still further features in the described preferred embodiments, the storage tank fluidly communicates with a consumer network.

According to still further features in the described preferred embodiments, there is provided a method of supplying heated water to at least one consumer, substantially as described herein, the method including: (a) providing a system as described herein, and (b) operating the system according to any feature described, either individually or in combination with any feature, in any configuration. BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Throughout the drawings, like- referenced characters are used to designate like elements.

In the drawings:

Figure 1 is a schematic block diagram of a heating system in accordance with one embodiment of the present invention;

Figure 2 is a schematic flow diagram of a heat pump water heating system including a sub-cooling arrangement, in accordance with one aspect of the present invention;

Figure 3 is a schematic flow diagram of a heat pump water heating system including a sub-cooling arrangement having a buffer tank sub-system, in accordance with another aspect of the present invention; and

Figure 4 is a schematic flow diagram of a heat pump water heating system including a sub-cooling arrangement and having both a primary heat transfer loop and a secondary heat transfer loop, in accordance with yet another aspect of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS

The principles and operation of the heat pump water heating systems according to the present invention may be better understood with reference to the drawings and the accompanying description.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

Referring now to the drawings, Figure 1 is a schematic block diagram of a heating system 100 in accordance with one embodiment of the invention. Heating system 100 may provide hot water to at least a part of a building or facility (not shown in Figure 1). Heating system 100 may also include at least one conventional burning or heating system 110. Heating system 100 includes at least one heat pump water heating system 120, and in some cases, at least one chiller or reversible heat pump system 130 adapted to cool or heat at least one room or space of at least one conditioning customer 146. Chiller system 130 may be further adapted, in an opposite mode, to heat at least one room or space.

Heating system 100, and more particularly, heating systems 110 and 120, may fluidly communicate with at least one thermal storage tank 125. One or more consumers 144 may receive a supply of hot water from thermal storage tank 125.

Conventional heating system 110, heat pump water heating system 120, and chiller system 130 may be controlled by a processor 150. Various inputs 152 may be introduced to processor 150, including environmental inputs, system inputs, fuel and/or electricity cost inputs, efficiency inputs (e.g., boiler efficiency, heat pump efficiency, etc.), and demand forecast inputs.

Figure 2 is a schematic flow diagram of a heat pump water heating system 220 in accordance with one aspect of the present invention.

Thermal storage tank 125, which may be operated as a pressurized vessel (typically at least 2-3 barg), is heated by heat pump water heating system 220. Hot water may be circulated to hot water consumers 144 via a hot water delivery line 229 of thermal storage tank 125. Unused hot water may be returned to storage tank 125 via a recirculation line 228. Alternatively or additionally, the unused hot water may be returned directly to a cold or inlet water line or pipe 206 of the heat pump condenser, as will be better understood from the description hereinbelow.

Heat pump water heating system 220 may include a compressor 221, a first heat exchanger or condenser 222, an expansion valve 223, a second heat exchanger or evaporator 224, and a refrigerant (not shown) disposed within and circulated within heat pump water heating system 220.

The cyclic operation of heat pump water heating system 220 may work substantially as follows: compressor 221 compresses the refrigerant gas, raising the pressure and temperature of the gas. In first heat exchanger 222, the refrigerant gas is subjected to an indirect (surface) heat exchange arrangement with respect to a flow of water coming from storage tank 125, via a cold or inlet water line or pipe 206. The refrigerant condenses to form a liquid phase, whereby the latent heat of the refrigerant may be substantially transferred to the flow of water.

Subsequently, the liquid refrigerant flows through expansion valve 223, reducing the pressure and temperature of the liquid refrigerant. The evaporation takes place in evaporator 224. The cooled refrigerant is then heated by a heating fluid (e.g., forced air circulation using ambient air, water from a water reservoir) in second heat exchanger 224, where the refrigerant is evaporated. The cycle then repeats: the refrigerant gas is then delivered to, and compressed by, compressor 221, as described hereinabove.

While heat pump water heating system 220 has been described as an electrically powered, compressor driven system, one of ordinary skill in the art will readily appreciate that various heat pump systems may be employed. One prominent example is a fuel-powered heat pump system (e.g., operating on natural gas) in which a chemical process may substitute for the motor-driven compressor.

Similarly, while Freon® has been used as an exemplary refrigerant, one of ordinary skill in the art will readily appreciate that various refrigerants or mixtures of refrigerants may be employed, including water, carbon dioxide and ammonia.

We have observed that in various practical heat pump water heater systems, the refrigerant may exit the condenser in a less than fully condensed state. Moreover, even if the heat exchanger is oversized to always, under all process conditions, produce a fully condensed refrigerant liquid, subsequent processing (typically in an expansion valve) leaves the refrigerant liquid at a disadvantageously high temperature. Consequently, the refrigerant liquid may have trouble absorbing heat in second heat exchanger or evaporator 224. This problem may be particularly acute during cold ambient conditions, when the temperature differential between the ambient heat supply and the refrigerant liquid may be small, substantially zero, or even negative.

We believe that under such conditions, the introduction of a sub-cooling arrangement may greatly improve the thermal efficiency and/or thermal capacity of the system. In such sub-cooling arrangements, a sub-cooling heat exchanger may be disposed downstream (with respect to the flow of the refrigerant fluid) to the refrigerant condenser. A heat-exchange fluid may be introduced to the heat exchanger, whereby any uncondensed refrigerant fluid is condensed by indirect heat transfer, releasing latent heat, and the liquid refrigerant transfers additional, sensible heat to the heat-exchange fluid flowing through the sub-cooling heat exchanger.

The return stream of unused hot water recirculated from at least one hot water consumer such as consumers 144 may be used as the heat-exchange fluid, whereby the heating system recovers additional heat from the refrigerant fluid. However, we have found that in many cases, the temperature of the unused hot water is disadvantageously high, such that the available temperature differential for indirect heat transfer (between the refrigerant fluid and the return stream) is impractically low.

Another possible sub-cooling arrangement involves the use of an external heat transfer fluid such as ambient air. This arrangement is advantageous in that the characteristic temperature differential (between the refrigerant fluid and the ambient air) is relatively high, and the supply of ambient air may be practically unlimited. However, the overall heat transfer coefficient is relatively rather low, requiring an inordinately large and expensive heat transfer arrangement. Moreover, in this arrangement, the heat gained by the ambient air is disadvantageously lost to the environment.

In analyzing the structure of various institutional water heating systems, we have found an additional, third potential heat sink: grid water such as grid water 262, which is typically used to fill hot water tank 125 as make-up water, in place of water consumed, for example, in showers, by consumers 144 (via hot water delivery line 229). The temperature of grid water 262 may typically be within a temperature range of 0°C - 35°C.

Thus, in one aspect of the present invention, heat pump water heating system 120 may include a sub-cooling arrangement such as sub-cooling arrangement 275, which may have a third, sub-cooling heat exchanger 260 disposed downstream (with respect to the flow of the refrigerant fluid) to condenser 222. Grid water 262 may be introduced in counter-current fashion to the flow of the refrigerant fluid, whereby any uncondensed refrigerant fluid is condensed, releasing latent heat, and the liquid refrigerant transfers additional, sensible heat to the low-temperature water flowing through sub-cooling heat exchanger 260.

The foremost advantage of the inventive arrangements is the substantial saving in energy. Moreover, in contrast to various other sub-cooling arrangements such as the air-cooled sub-cooling arrangement described hereinabove, the heat value removed from the refrigerant may be recovered and utilized in producing the heated water product.

The heated grid water may be delivered via water line 264 to tank 125. It may be advantageous, however, to deliver the heated grid water directly to heat pump, e.g., via cold or inlet water line 206, as shown in Figure 2.

Figure 3 is a schematic flow diagram of a heat pump water heating system 320 in accordance with another aspect of the present invention. The cyclic operation of heat pump water heating system 320 may work substantially as described hereinabove with respect to system 220.

As with sub-cooling arrangement 275, sub-cooling arrangement 375 may have a third, sub-cooling heat exchanger 260 disposed downstream, with respect to the flow of the refrigerant fluid, to condenser 222. Grid water 262 may be introduced in counter-current fashion to the flow of the refrigerant fluid, whereby any uncondensed refrigerant fluid is condensed, releasing latent heat, and the liquid refrigerant transfers additional, sensible heat to the low-temperature water flowing through sub-cooling heat exchanger 260.

We have found that the flowrate of make-up water may largely depend on the highly fluctuating rate of water consumed by consumers such as consumers 144. Consequently, the make-up water flowrate may be correspondingly sporadic or highly fluctuating. Under such conditions, we have further found that both the sub-cooling process and the pre -heating process may be greatly compromised.

Sub-cooling arrangement 375 may advantageously include a buffer tank sub-system including a water buffer tank 365, which fluidly communicates with sub-cooling heat exchanger 260. Grid water 262 may be introduced directly to buffer tank 365, or to a bypass line or pipe 361, through which water from buffer tank 365 is introduced to heat exchanger 260. It is also possible for grid water 262 to be directly to heat exchanger 260.

After passing through heat exchanger 260, the pre -heated water may be introduced to the hot water loop (e.g., tank 125 or to inlet water line 206 of condenser 222). The pre -heated water may be introduced to buffer tank 365. It may be advantageous to feed a first portion of the pre -heated water to the hot water loop, and a second portion of the pre -heated water to buffer tank 365.

In some cases, it may be advantageous to feed at least a portion of the pre- heated water to the hot water loop, via a discharge pipe or line 364 of buffer tank 365.

The above-described arrangements may help to overcome, or at least alleviate, various problems associated with the operation of hot water heat pump systems, some of which have been described hereinabove.

By way of example, the efficiency of the sub-cooler/pre-heater, and the efficiency and/or capacity of the heat pump system, may be compromised by the erratic flowrate of make up water. To solve this problem, a buffer tank or vessel such as buffer tank 365 may be filled by grid water to a pre-determined level (e.g., completely filled). The water may be circulated through heat exchanger 260. This circulation may gradually heat the water in the buffer tank until an equilibrium temperature, predetermined temperature, or control set point temperature is substantially reached. Typically the temperature is higher than that of the grid water, but lower than that of the water in the hot water tank 125. During this process, the system benefits from the additional cooling (subcooling) of the Freon®, as previously described.

When hot water from the hot water tank is consumed by at least one consumer such as consumers 144, the pre -heated grid water is used as make-up water, in place of grid water. Thus, the energy stored in the buffer tank is recovered and utilized within the hot water heating system. As the hot water is being consumed, grid water may be directed via the sub-cooler into the buffer tank, to maintain the water level and/or pressure in the tank. The buffer tank may be directly connected to the grid water outlet, such that the refilling operation may be performed without additional pumping equipment.

Alternatively, once hot water consumption from the hot water tank is stopped, grid water may be directed to fill the buffer tank to a particular or predetermined level, and water from the buffer tank water is again recirculated through the sub-cooler.

A processor such as processor 150 may control various flows of water within the heat pump system, the fill level of the buffer tank, and other control variables in the system. Various temperature measurements and/or temperature differentials temperature may serve as a basis for the control logic of the processor.

Figure 4 is a schematic flow diagram of a heat pump water heating system 420 in accordance with another aspect of the present invention. The cyclic operation of heat pump water heating system 420 may work substantially as described hereinabove with respect to systems 220 and 320.

However, unlike the previously described systems, system 420 has both a primary heat transfer path or loop 480 and a secondary heat transfer path or loop 490. Primary heat transfer loop 480 contains a first heat transfer liquid, typically water, which may be circulated in a substantially closed system between a water side of condenser 222, and a heating or hot water side of at least one heat exchanger such as heat exchanger 482 and/or heat exchanger 492.

After pre -heating the grid water in heat exchanger 260 (and effecting sub- cooling of the refrigerant passing therethrough), the pre-heated grid water is directed into the cold water side of secondary heat transfer loop 490, whereby the pre-heated grid water is further heated heat exchanger 492 to produce a fully heated flow of water, prior to delivery to consumers 144. Typically, and as shown in Figure 4, the fully heated flow of water is first returned to a storage tank 425, and is delivered therefrom to consumers 144, via line 229.

Similarly, heat exchanger 482 heats a flow of liquid, typically water, by means of the primary water flow heated in condenser 222, prior to delivery to at least one consumer such as conditioning customer 146 described with respect to Figure 1. The consumer may solely consume a portion of the sensible heat of the flow of liquid, which is recirculated in a substantially closed loop. Alternatively, the consumer may consume at least a portion of the heated water, which is circulated in an at least partially open configuration.

One exemplary consumer of the heat transferred in heat exchanger 482 is a heated swimming pool. We have observed that such a consumer may require substantially continuous, 24/7 heating. Consequently, it may be particularly advantageous to use the water flow from the pool as a heat transfer liquid within a subcooling heat exchanger (not shown) that may operate in a similar fashion or in a substantially identical fashion with respect to heat exchanger 260 as described hereinabove, with respect to Figures 2-4. The subcooling heat exchanger utilizing a closed loop source of liquid (in this case, water) may be incorporated within the Freon® loop of heat pump water heating system 420 instead of, or in addition to (e.g., in series with) heat exchanger 260.

It will be appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A heat pump water heating system for supplying heated water to at least one consumer, the system comprising:

(a) a first heat exchanger, fluidly communicating with a refrigerant circulation pipe, and adapted to effect an indirect exchange of heat between a first flow of water and a compressed refrigerant gas, to heat said first flow of water, and to condense said compressed refrigerant gas into a refrigerant fluid including a refrigerant liquid;

(b) a second heat exchanger, fluidly communicating with said circulation pipe, and adapted to effect an exchange of heat between a second refrigerant liquid and a heat source, whereby a second refrigerant gas is produced;

(c) a compression arrangement, associated with said circulation pipe, adapted to compress said second refrigerant gas to produce said compressed refrigerant gas;

(d) a storage tank adapted to operate at a superatmospheric temperature, and to provide a heated flow of water for the consumer;

(e) a circulation arrangement adapted to circulate said first flow of water to said first heat exchanger, and after being heated therein, to return said first flow of water to said storage tank or to the consumer, and

(f) a third heat exchanger, having a first flow path fluidly communicating with said circulation pipe, and a second flow path, fluidly sealed with respect to said first flow path, and adapted to receive and discharge a second flow of water, said flow paths juxtaposed to effect an indirect exchange of heat between said refrigerant fluid and said second flow of water,

said second flow of water adapted to have a temperature below a temperature of said first flow of water, whereby said refrigerant fluid undergoes sub-cooling to produce said second refrigerant liquid, and whereby said second flow of water is heated to produce a heated second flow of water.

2. The heat pump water heating system of claim 1, wherein said compression arrangement includes at least one compressor adapted to be electrically connected to a power supply and to fluidly communicate with said circulation pipe, said compressor adapted to compress said second refrigerant gas to produce said compressed refrigerant gas.

3. The heat pump water heating system of claim 1 , further comprising an expansion valve, fluidly communicating with said circulation pipe and adapted to reduce a pressure and a temperature of said refrigerant liquid to produce said second refrigeration liquid.

4. The heat pump water heating system of claim 1, further comprising a recirculation loop fluidly communicating with said second flow path of said third heat exchanger, whereby at least a portion of said heated second flow of water is recirculated via said loop to an inlet of said second flow path.

5. The heat pump water heating system of claim 1, further comprising a buffer tank fluidly communicating with said second flow path of said third heat exchanger.

6. The heat pump water heating system of claim 1, wherein an inlet of said second flow path fluidly communicates with a grid water pipe.

7. The heat pump water heating system of claim 1, wherein an inlet of said second flow path fluidly communicates with, and is directly connected to, a grid water pipe.

8. The heat pump water heating system of claim 1, wherein an outlet of said second flow path is adapted to discharge at least a portion of said second flow of water to said buffer tank.

9. The heat pump water heating system of claim 1, wherein an outlet of said second flow path is adapted to discharge at least a portion of said second flow of water to said circulation arrangement.

10. The heat pump water heating system of claim 1, further comprising at least one sensor adapted to provide a temperature indication in at least one location within the heating system.

1 1. The heat pump water heating system of claim 1 , further comprising at least one sensor adapted to perform a measurement of at least one system parameter including information pertaining to at least one flowrate within the heating system.

12. The heat pump water heating system of claim 1, further comprising sensors, each adapted to provide a temperature indication, said sensors disposed in at, or proximate to, at least two, at least three, or all four of the following locations:

an inlet to said first flow path;

an outlet to said first flow path;

an inlet to said second flow path;

an outlet to said first flow path.

13. The heat pump water heating system of claim 1, further comprising a processor adapted to receive at least one input including said temperature indication or said measurement, and to control an operation of said heat pump water heating system based on said input.

14. The heat pump water heating system of claim 1, wherein said storage tank fluidly communicates with a consumer network.

15. A method of supplying heated water to at least one consumer, substantially as described herein, the method comprising:

(a) providing a system according to any of claims 1-14, and

(b) operating said system according to any feature described, either individually or in combination with any feature, in any configuration.