GB2247072A - Heating or cooling system - Google Patents

Abstract

A heating or cooling system uses a heat pump and a phasechange thermal storage tank (1) to supply space heating, space cooling, and domestic hot water to a building. A heat exchanger (12) in the exhaust air stream and another one attached to the building grey water drain pipe (11) extract heat from the stale air and grey water for delivery to the thermal storage tank (1) via an ethylene glycol loop. Subsequently, this heat is extracted from the thermal storage tank to supply the evaporator (2) in the heat pump when a heating demand occurs. A potable water loop extends through the condenser (4), a hot water tank (15) and if required, an air conditioning unit heat exchanger (14). Cooling is supplied via an extension of the ethylene glycol loop passing to a heat exchanger (10). <IMAGE>

Description

INTEGRATED HEATING, COOLING AND VENTILATION SYSTEM TECHNICAL FIELD This invention relates to residential and small commercial building mechanical systems.

The device integrates many mechanical components and functions into a single packaged in a typical house it replaces the furnace, hot water heater, whole-house ventilation system or heat recovery ventilator, and central air conditioner.

Using heat pump technology, the device captures waste energy from multiple sources (i.e. warm exhaust ventilation air, excess heat gain to house air due to solar input and household activities, and warm grey water from showers, sinks, and clothes washing, and any other low grade heat source), stores it, and then extracts the energy as it is needed to satisfy heating demands. Since the captured waste energy is "free heat", only the energy required to transfer the heat from one side of the heat pump to the other is the purchased energy. This results in actual energy use that is typically 1/3 the amount being supplied for heating loads.

The system can perform both space heating and space cooling/dehumidification without the need for a reversing valve, typically required for a heating/cooling heat pump.

Packaging of the main components in a single unit, except for the thermal storage tank, eliminates multiple installation procedures that would be necessary with equivalent equipment that is packaged discreetly, and reduces floor space usage as compared to equivalent equipment that is packaged discreetly.

BACKGROUND ART With respect to integration, examples of prior art and their deficiencies are: Reversible heat pumps providing space heating, hot water, and space cooling. Deficiencies: Ventilation is not provided. If the unit is an outdoor air or ground source heat pump, the evaporator/condenser is located outside or buried in the ground. The former can be a source of noise and the latter can be expensive to install. Both require penetrations through building walls.

Domestic hot water units that also supply space heating (electric or gas). Deficiencies: Full integration of functions is not provided (no cooling or ventilation). They do not employ heat pump technology and therefore are not as energy efficient.

Exhaust air heat pumps providing domestic hot water, partial space heating and cooling, and ventilation. Deficiencies: Full integration of functions and full space conditioning is not provided (limited energy recovery sources).

With respect to heat pumps, examples of prior art and their deficiencies are: Reversible and non-reversible outdoor air heat pumps. Deficiencies: Outdoor air heat pumps (reversible and non-reversible) are ineffective for space and hot water heating when the source temperature (i.e. air) is very cold. Backup electrical resistance heating is required and energy efficiency is reduced. Reversible heat pumps require a refrigerant reversing valve to be able to perform both heating and cooling. This can be a more expensive and complicated solution, and, if there is a failure, can be an expensive repair. Also, defrost cycles are required which increase energy usage and complexity of controls.

Reversible ground source heat pumps.

Deficiencies: Reversible ground source heat pumps utilize the near constant ground temperature of the earth as a source, or a dump, of energy, depending on heating or cooling needs. While employing thermal storage, these systems are not designed to utilize phase-change properties of the storage medium and are typically much more expensive to install.

Exhaust air heat recovery heat pumps.

Deficiencies: Exhaust air heat recovery heat pumps provide hot water, ventilation, and partial space heating. Typically, supplementary electrical heat is required for heating demands as there is limited heat recovery in exhaust air only (i.e. where there are not multiple sources). Energy efficiency, in this case, is lower. Also, the use of direct expansion evaporators in these systems makes it necessary to restrict minimum exhaust air flow rates to avoid freeze-up, which lowers the fraction of recoverable heat.

Solar-assisted heat pumps. Deficiencies: Solar-assisted heat pumps can utilize solar collectors to increase the energy supply to a heat pump. However, this requires more equipment, outside installation, more complexity, and higher cost.

With respect to thermal storage, examples of prior art are: Large commercial phase-change thermal storage tanks employing water as the storage medium.

Deficiencies: Presently, phase change thermal storage tanks that utilize the latent energy released/absorbed as water/ice changes phase are available only for large installations, typically in commercial buildings, and are designed for peak cooling load reduction and load shifting.

Water storage that employs sensible heat properties. Deficiencies: Water storage systems employing sensible heat storage require a volume of water approximately seven times that of a phase change system of similar capacity.

Ground/aquifer storage. Deficiencies: Ground and aquifer storage systems are typically more expensive and require external components. Installation can be costly.

Rock storage. Deficiencies: Rock storage systems require a large volume of rocks to have a similar storage capacity as compared to a water or phase change storage system. The loss in building floor area and expense of the system can be a disadvantage.

DISCLOSURE OF INVENTION It is an object of the invention to provide an integrated system which overcomes or reduces some of the problems of the prior art.

The invention involves utilizing waste (or low cost) energy generated in the building, and provides space heating, space cooling, whole-house ventilation and domestic hot water heating in the most energy and space efficient manner using heat pump technology and thermal storage.

The system is essentially totally indoors, therefore eliminating penetrations in building envelope to outdoors, premature aging and weathering of outdoor components, and exterior noise, which is a problem with outdoor air-conditioner condenser fans referred to above.

The invention utilizes heat pump technology and a phase-change thermal storage tank to supply space heating, space cooling, and domestic hot water to the building. A heat exchanger in the exhaust air stream and another one attached to the house grey water drain pipe (does not include sanitary fixtures) extract heat from the stale air and grey water for delivery to the thermal storage tank. Subsequently, this heat is extracted from the thermal storage tank to supply the evaporator in the heat pump when a heating demand (space or hot water) occurs.

The thermal storage medium in the preferred embodiment is water. The large latent heat properties as it changes phase from liquid to ice (energy extraction) or ice to liquid (energy addition) are utilized in order to make the storage tank size small without compromising storage capacity.

The use of a thermal storage tank at a minimum temperature of 0 degrees Celsius restricts the antifreeze solution loop circulating via the evaporator cooling coil, exhaust coil, and grey water heat exchanger to just below freezing, effectively avoiding frost build-up in these components, unlike conventional heat pumps referred to above.

Unlike conventional outdoor air heat pumps, whose backup heating element is controlled by outside air temperature, the backup heater is controlled by the amount of available energy in the storage tank. This point occurs when the storage tank is almost completely frozen solid.

Reversing valve inefficiencies and dampered air flow reversal for space heating/cooling changeover is avoided by using liquid heat transfer dual coils.

Motorized control valves permit different components in the loops to act as suppliers or extractors in the system, depending upon whether heating or cooling is required.

Equipment redundancy, floor-space requirements, and capital cost is reduced by component integration.

Energy is saved by employing heat pump technology and thermal storage of waste heat to satisfy building loads.

Development of high performance windows (high R-value) allows larger glazing areas to be used in buildings resulting in higher passive solar contribution to reduce heating loads. The system can capture excess solar gains, resulting from larger window areas, and deliver it to the storage tank to supply heating at a later time.

The thermal storage tank takes advantage of non-coincidental and nighttime waste heat capture to supply loads during peak power demand with much less energy. Peak energy input is only required to transfer heat from the storage tank to the building (i.e. energy to run the compressor, circulating pumps, and fans). The thermal storage capability can also be of advantage in areas where credits are available for off-peak demand.

Further features of the invention will be described or will become apparent in the course of the following detailed description.

BRIEF DESCRIPTION OF DRAWINGS In order that the invention may be more clearly understood, the preferred embodiment thereof will now be described in detail by way of example, with reference to the accompanying drawings, in which: Fig. 1 is an illustration of the components of the system; Fig. 2 is a schematic of operation of the system; Fig. 3 is an illustration of the thermal storage tank; Fig. 4 is an illustration of the ground storage configuration; Fig. 5 is a block diagram illustration of the concept of the invention; and Fig. 6 is a schematic illustration of the operation of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION The system, in a single package, physically and thermally integrates space heating and cooling, ventilation, and hot water supply. Coupling these functions with thermal storage capability enables the system to recover waste heat from exhaust air, drain grey water, overheated indoor air and other "free" or inexpensively generated energy sources. These gains are collected whenever they occur and are stored in the thermal storage tank. A liquid-to-liquid heat pump extracts gains from the thermal storage tank to heat water in a hot water storage tank. This supplies hot water for occupant use and space heating when required.

Cooling is supplied via a chilled liquid loop circulating via the thermal storage tank. Heating/cooling is supplied via a fan coil while a smaller fan coil exhausts continuously to outside, providing central ventilation from kitchens and bathrooms.

The physical configuration of the main integrated appliance is modular in nature, consisting of two modules. The first module is the thermal transfer unit, and includes four distinct component packages (see Fig. 1): hot water tank section heat pump section space conditioning fan coil exhaust fan coil Module 2 is the thermal storage tank, and is connected to Module 1 via antifreeze solution lines. The thermal storage tank is an insulated metal storage tank with a waterproof vinyl liner that contains a flexible PVC heat exchanger in a coiled configuration that is surrounded by water. The heat exchanger is suspended vertically and the heat transfer fluid enters and exits via the ends of the vertical manifolds. Depending upon the amount of energy extracted or supplied to the water by the heat exchanger, the water will be either in liquid or solid (ice) state.

The integrated system typically replaces the furnace, hot water tank, air conditioner, and central ventilation with heat recovery (heat recovery ventilator).

In greater detail, referring to Fig. 2 in particular, the various components are as follows: Phase change thermal storage tank 1: The antifreeze solution circulating via the heat exchanger adds or extracts heat from the tank water or ice.

Evaporator 2: Transfers thermal energy from the antifreeze solution to the liquid refrigerant, causing the refrigerant to evaporate into a gas.

Compressor 3: Compresses gaseous refrigerant to a higher temperature and pressure.

Condenser 4: Double-walled heat exchanger that transfers thermal energy from hot refrigerant to potable water for use as domestic hot water or for space heating via a fan coil.

Capillary tube 5: Pressure reducing device that closes refrigerant loop between condenser and evaporator. It introduces low pressure and temperature liquid refrigerant to the evaporator.

Ethylene antifreeze solution circulating pump 6.

Potable water circulating pump 7.

Space cooling valve 8: Motorized valve that opens when cooling is asked for by house thermostat and diverts antifreeze solution to the space cooling coil.

Heat recovery valve 9: Motorized valve that opens when system is in winter or backup mode (space cooling valve off). It allows antifreeze solution to circulate through the grey water heat exchanger and exhaust air heat recovery coil.

Space cooling coil 10: Coil that is supplied by cool antifreeze solution to reduce temperature and humidity of building air as it passes over the coil. The warmed antifreeze solution transfers heat to the evaporator or thermal storage tank.

Grey water heat exchanger 11: Counterflow heat exchanger that, via antifreeze solution, extracts heat from warm household drain water and transfers it to the evaporator or thermal storage tank.

Exhaust air heat recovery coil 12: Coil that antifreeze solution flows through to extract heat from exhaust air before it is exhausted to the outside. The antifreeze solution transfers heat to the evaporator or thermal storage tank.

Space heating valve 13: Motorized valve that, when heating is asked for by house thermostat, diverts hot water to the space heating coil.

Space heating coil 14: Coil that is supplied with hot water to warm building air.

Domestic hot water tank 15: Conventional, well-insulated domestic hot water storage tank heated by hot water circulated directly from the condenser (space heating valve off). In the space heating mode, hot water circulates via the space heating coil before returning to the tank.

Domestic hot water line 16: Feeds hot water to building when called for.

Cold water supply line 17.

Electrical backup water heating element 18: The backup heating element is powered when there is insufficient heat in the storage tank to meet the hot water temperature set point in the hot water tank, or when system is manually turned to the backup mode (e.g.

when there is a heat pump failure).

Hot water tank thermostat 19.

Exhaust air fan 20: Exhausts air continuously from the house at low speed. Manual timers or a dehumidistat controln high speed.

Supply air fan 21: Supplies warm or cool air to building.

Operation For heating, the cool antifreeze solution is circulated through the thermal storage tank 1, picks up heat from the water, and flows back to the evaporator 2 where it transfers its heat to the colder refrigerant, causing the refrigerant to evaporate to a gas. The refrigerant flows to the compressor 3, where its temperature and pressure is increased, and then flows to the condenser 4 to give off the heat to the water. The water flows to either the space heating coil 14, diverted by the space heating valve 13, or directly to the hot water tank 15. When hot water is drawn off the top of the tank for household use, cold water flows into the loop prior to the condenser, via cold water supply line 17. The heating mode is controlled by the hot water tank thermostat. When the building requires heat the space heating valve 13 is opened to allow hot water circulation via the space heating coil 14.

For cooling, when the building thermostat asks for cooling, the space cooling valve 8 opens and cool ethylene antifreeze solution is diverted to the space cooling coil 10. Exhaust air and grey water heat recovery are disallowed by closing the heat recovery valve 9. Building air is cooled and dehumidified as it passes through the coil. The antifreeze solution is warmed in the process and flows back to the evaporator 2 where, if the heat pump is on, it gives off its heat. If there is no heating demand (i.e. domestic'hot water), the antifreeze solution will transfer its heat to the thermal storage tank 1 as it flows round the loop. To maintain cold conditions in the storage tank, and therefore cooling capacity, a heating demand can be created to cause the heat pump to turn on and cool the antifreeze solution loop.This can be achieved, aside from a hot water or space heating demand, by dumping warm water via an additional loop (not shown) such as an outdoor hose or outdoor fan coil to reject heat to the outside.

For ventilation, operation is continuous at low speed by the exhaust air fan 20. Balanced ventilation is achieved by introducing preheated makeup air into the building return air (opening upstream from the space heating and cooling coils). High speed ventilation-is available by manual switching or automatically on a rise in humidity (with dehumidistat, not shown).

For heat recovery, in the winter mode, the heat recovery valve 9 is always open. The antifreeze solution flows from the thermal storage tank 1 and is diverted to the grey water heat exchanger 11 and the exhaust air heat recovery coil 12. The cool antifreeze solution picks up heat from the warm drain water and warm exhaust air as it flows through each heat exchanger. The warmed antifreeze solution then reaches the evaporator 2 where, if the heat pump is on, it gives off its heat to the cooler refrigerant. If there is no heating demand, the antifreeze solution will give off its heat to the storage tank 1, thereby recharging the tank for future heating needs.

When the system is switched to summer mode, the heat recovery valve 9 is closed. If there is a cooling demand, antifreeze solution circulates through the space cooling coil 10 where it picks up heat and then rejects it to the evaporator 2 or otherwise to the thermal storage tank 1 if there is a hot water demand.

For a backup, if the thermal storage tank 1 has been depleted (i.e. there is too little stored energy to maintain desired temperature of water in hot water tank) and a heating demand occurs, the system will switch over automatically to backup mode. The compressor will turn off, but the heat recovery valve 9 is turned on, and the antifreeze solution circulates through the grey water heat exchanger and the exhaust heat recovery coil picking up heat for delivery to the storage tank. Meanwhile, the electrical backup element 18 in the hot water tank is energized to satisfy the tank thermostat. The system will revert back to the mode that it was in before the backup switch-over (summer or winter) as enough energy from heat recovery becomes available in the storage tank.

The backup mode can also be selected manually if an emergency situation occurs with the heat pump unit.

This ensures that space and hot water heating can be maintained while the heat pump function is inoperative.

The system was designed for flexibility under different applications and site requirements. Energy supplied to the extraction side of the heat pump can be multi-source. Similarly, there are options for heating supply. Three variations on strategies described in the preferred embodiment are listed below: (1) For use as a hydronic space heating supply, the space heating function employs hot water via a fan coil unit to heat air returned from the building interior (forced air system). Hot water can be used directly in a hydronic heating system (i.e. hot water supplying roomby-room radiators).

(2) For use as an excess heat dump via exhaust (cooling function): In the preferred embodiment cooling capacity is maintained in the thermal storage tank by having the heat pump heat hot water for domestic use and disallowing any other heat gains than from the cooling function. For various reasons, such as a highly glazed house design or unusually low DHW loads in summer, this intrinsic cooling capacity may be insufficient. To ensure an increased cooling capacity a second coil is installed in the exhaust fan coil unit. This coil is supplied with hot water, when conditions in the thermal storage indicate that more waste heat from cooling needs to be dumped to outside. The coil heats the exhaust air above the interior building temperature as it leaves the structure.

(3) For dehumidification, some applications, such as spas or pool areas, experience high moisture loads. The space conditioning supply coil can be configured and controlled such that the return building air is chilled (by the cooling coil) and subsequently heated (by the heating coil) to create comfortable conditions in the supply air leaving the space fan coil unit.

As an alternative embodiment of thermal storage, to obtain the benefit of ground coupling, thermal storage may be located below grade outside the building enclosure (Fig. 4). This storage consists of a flexible liner filled with a soil-water mixture and is insulated from the above grade conditions. Similar flexible sheet heat exchangers as in the thermal storage tank described above are used to transfer heat in and out of the ground thermal storage. Since the storage contains water at all times the phase change of water accounts for the storage capacity.

It will be appreciated that the above description relates to the preferred embodiment by way of example only. Many variations on the invention will be obvious to those knowledgeable in the field, and such obvious variations are within the scope of the invention as described and claimed, whether or not expressly described.

Claims (7)

CLAIMS:

1. A heating, cooling and ventilation system characterised by heat recovery means for recovering excess heat from a plurality of sources within a building, thermal storage means for receiving and storing said recovered excess heat, and a heat pump connected to extract heat from said heat sink and to deliver same via a water loop to a hot water tank and other heat-requiring locations.

2. A system as recited in claim 1, characterized by a diversion valve positioned between said heat pump and said hot water tank to divert heated water from said heat pump to building space heating means and thence to said hot water tank, in response to a thermostat indicating a space heating need.

3. A system as recited in claim 1, characterized by an ethylene glycol loop between said heat pump and said thermal storage means, and a diversion valve between said heat pump and said thermal storage means for diverting cool ethylene glycol to building space cooling means in response to a thermostat indicating a space cooling need.

4. A system as recited in claim 2, characterized by an ethylene glycol loop between said heat pump and said thermal storage means, and a diversion valve between said heat pump and said thermal storage means for diverting cool ethylene glycol to building space cooling means in response to a thermostat indicating a space cooling need.

5. A system as recited in claim 4, where said space heating means and said space cooling means are one and the same, said heating/cooling means comprising a supply air fan drawing air across cooling and heating coils respectively in said ethylene glycol and water loops.

6. A system as recited in claim 1, in which said heat recovery means includes a heat exchanger in said ethylene glycol loop to extract heat from building drain grey water.

7. A system as recited in claim 1, in which said heat pump and said hot water tank are positioned within one module.