WO2013123564A1

WO2013123564A1 - Energy recycling system for domestic hot water

Info

Publication number: WO2013123564A1
Application number: PCT/AU2013/000169
Authority: WO
Inventors: Ryan Gordon
Original assignee: Sun-Pak Pty Ltd
Priority date: 2012-02-23
Filing date: 2013-02-25
Publication date: 2013-08-29
Also published as: AU2013201129A1

Abstract

An energy recycling system for domestic hot water including: an air chamber enclosed by a chamber housing having a chamber wall; an air intake inlet penetrating the chamber wall to the air chamber and arranged to provide fluid communication between the air chamber and a source of domestic building envelope air; air pumping means associated with the air intake inlet for pumping air from the source through the intake to the air chamber; an air discharge outlet penetrating the chamber wall for discharging air from the air chamber; an air to water heat pump interposed between the source of domestic building envelope air and the discharge outlet for pumping heat from the domestic building envelope air to heat transfer means, and a water heater operatively associated with the heat transfer means and operable to transfer heat to the domestic hot water.

Description

ENERGY RECYCLING SYSTEM FOR DOMESTIC HOT WATER

THIS INVENTION relates to. an energy recycling system for domestic hot water. The invention has particular application to energy efficient recycling of latent and sensible heat energy in domestic wet-area air using an energy recovery apparatus. However, the invention has application more generally to energy recovery in applications where recoverable energy is found in air spaces. The invention also has particular application to the use of recovered energy to supplement or replace domestic hot water heaters. However, the invention has application more generally to the use of recovered energy for other uses, such as, for example, for heating.

Domestic hot water (HW) systems are typically one of the highest consumers of energy in a household. Present systems normally use electricity or gas. Some of the uses of hot water result in the generation of warm, moist air, particularly in the wet areas of the home such as shower stalls, bathtubs and laundries. However, the energy contained in such air has not been recoverable due to its low density. Moreover, warm moist air so generated increases the load on air conditioning in structures where air conditioning is in use. Moreover, where a clothes drier is installed and used, additional moist warm air is discharged from the clothes drier into the home. For convenience, such air will be referred to herein as domestic wet air.

In the past because of the low-grade nature of the energy in domestic wet air, recovery of energy therefrom has been placed in the "too hard basket". Some of the reasons given are that an adequate footprint for heat recovery equipment is not available, particularly in smaller dwellings, such as apartments. Floor area has a sale value and build cost, these being optimised in the architecture. Low energy (HW) has not been a developer consideration. Therefore, the developer falls back to the least expensive option for installed hot water which is an electrical resistance water heater (ERWH) .

Some attempts have been made to make domestic energy consumption more environmentally friendly. However, conventional heat pumps are bulky and require a prohibitive volume of air. For a traditional flat plate or evacuated tube type solar water heater to be considered viable, only those installations with five hours insolation or more a day could produce sufficient energy to heat the water for normal domestic consumption. For reasons of orientation and shadow, perhaps less than 5% may be suitable. Sometimes, the development application for the building does not permit collectors to be mounted if they adversely affect the aesthetics of the building. The source of domestic wet air being apartment bathrooms or laundry rooms such locations are often at or adjacent the normal location of an existing ERWH.

Retrofit to ring mains or centralised hot water reticulation with gas fired ring heaters may cost well above an acceptable amount per apartment, particularly in medium to large apartment building (100 or more apartments). Consensus of apartment owners to proceed with a centralised hot water conversion would be required.

This invention aims to provide an energy recycling system for domestic hot water which identifies that there is a potential for energy recovery from domestic wet air contrary to the current teaching in the art. The invention also addresses one or more energy inefficiencies of the traditional arrangements of the prior art. Other aims and advantages of the invention may become apparent from the following description.

With the foregoing in view, in one aspect the present invention resides broadly in an energy recycling system for domestic hot water including: an air chamber enclosed by a chamber housing; an air intake penetrating the chamber housing to the air chamber and arranged to provide fluid communication between the air chamber and a source of domestic building envelope air; air pumping means associated with the air intake for pumping air from the source through the intake to the air chamber; an air discharge penetrating the chamber housing for discharging air from the air chamber; an air to water heat pump interposed between the source of domestic building envelope air and the^' discharge for pumping heat from the domestic building envelope air to heat transfer means, and a water heater in heat transfer operatively associated with the heat transfer means and operable to transfer heat to the domestic hot water. The building envelope air is taken to refer to the air within the envelope of the building, apartment, lot or part thereof. Preferably, building envelope which is, or is likely to be, moisture saturated or heated or both, such as air from kitchens, laundries, bathrooms, indoor pools and spas and such like. It will be seen that the higher the energy content, the greater the opportunity to recover energy from such air.

Preferably, the intake includes an intake passage through which the domestic building envelope air may pass. Preferably, the discharge includes a discharge orifice through which the air processed by the apparatus may be discharged. The discharge orifice may be arranged to be in fluid communication with ducting to direct spent air into the building or outside the building.

Preferably, the air intake passage, air pumping means, air discharge orifice and air to water heat pump are embodied in a blower apparatus. More preferably, the blower apparatus is sized to fit atop a typical domestic water heater.. In such form, it is preferred that the heat pump have its hot side cooperatively associated with the water heater for heating, or at least assisting with the heating, of the water to be used as hot water.

In one form of the invention, the blower apparatus may be retrofitted to an existing water heater. Alternatively, the blower apparatus may be integrated with a new water storage heater.

The heating capacity of the heat pump is not necessarily equivalent to the existing ERWH, but in use, the apparatus is able to provide hot water for the residents as fit for purpose for residential hot water, and to at least any minimum standard that may apply. It will be appreciated that the heating capacity is limited to and governed and controlled by available low grade energy air. Preferably, the apparatus is of a physical size that allows installation in typical apartments adjacent an existing hot water heater cylinder, thereby permitting installation substantially without detracting from the utility of and enjoyment of the living space of apartment. Similar considerations apply, though to a lesser extent, in freestanding dwellings. Of course, the invention also has application to commercial and industrial installations. Such a form also permits installation to be effected with minimum interruption to existing architecture.

Once installed, the apparatus may be serviced with minimum cost, interruption to service, and replaced if required without interruption to any structural or architectural elements that were customized on the original installation.

It is also preferred that the blower be powered by an electric motor and a control system be electrically connected to the electric motor for controlling the blower apparatus. In such form, the control system is so arranged that it may be customised for individual apartment hot water requirements. More preferably, the control system has service and fault- alert diagnostics operable to provide owners with information which may be used to minimise service or fault lifecycle costs. It is suggested that by its very function, the present invention provides other benefits, including assisting in climate control with dehumidification and cooling. Moreover, the heat pump may include condensation collecting means for collecting moisture condensed from the domestic wet air. In such form, an additional benefit includes, in certain operational situations, a limited and conditional supply of distilled but not necessarily potable water.

In a preferred form, the apparatus is formed as a modular unit. In such form, the modular unit is a heater only, and has no integral storage cylinder. The modular unit has an internal or external pump that circulates the heating water through an existing or new storage cylinder. It can also be mounted close coupled on an atmospheric pressure (non pressurized) storage vessel that has a secondary heat exchanger for a supply of potable water.

An exemplary preferred form of the modular unit will now be described: The modular unit has a case comprising two chambers close or remote coupled. The dimensions of the combined chambers are such that the entire unit can be fitted into a standard laundry closet above an existing electric water heater if required. Locations for fitting can vary from outside under the eves on . brackets to laundry and bathroom cupboards where duct access is available for air flow management. Heat pumps require a volume of air maintained within a particular temperature range in order to function

The modular unit is designed with a recovery rate factored from the building thermal mass capacity to maintain or regenerate the air temperature, or in the case where air energ expressed as volume by temperature cannot maintain temperature from the building room envelope, supplementary ducting can be fitted to move air in or out of the building room envelope and direct it to the apparatus of the invention for recovery of energy therefrom.

The primary air chamber is able to swivel through 360°, able to be positioned to suit- the individual application. For. example, a position is selected during installation to facilitate connection to ducting, passages or openings to wet' areas for air egress or ingress.

Both chambers may be roto-moulded or injection-moulded polypropylene or equivalent composite plastics. In such form, the chambers are formed for the sliding engagement of a mechanical services chassis which may be installed into the lower chamber from a front opening.

In such form, a primary air chamber is provided to introduce or exhaust air. An electric motor is preferably provided, more preferably as a variable speed motor coupled to a centrifugal fan operable to urge air to an evaporator of the heat pump which is fitted in the secondary or main chamber. Dimensions are selected to provide fitting to a range of standard installation configurations.

The secondary main chamber consists of an open fronted box configuration with a tube-in-fin evaporator inset in a panel. This allows for left, right or other positions.

This allows for the lower chamber to be rotated. The front facing edges of the chamber may have multiple moulded sockets to facilitate self-latching door pins. The base of the main chamber has a raised front lip and outer drain port flange to allow the base to act as a water condensate collection tray.

The two sides of the secondary chamber have integrally moulded internal rail protrusions (runners) to align and facilitate a slide-in chassis. Each of the two sides, top and back has an interchangeable snap in panel. One panel incorporates a filter slide and snap in grill or optional flange as duct adaptor. The other panel is a blank.

Similarly, the plumbing and the electrical port or ports are ambidextrous. A front panel (door), with a moulded aperture allows to enclose the chamber. The door has a rectangular aperture in an upper quadrant to facilitate a snap in display and control module. Note this module has a bayonet pin locator for quick disconnection. The air to water heat-pump elements are mounted on a chassis. The chassis slides into the chamber with runners matching the rails on the inside left and right sides of the chamber. In the final fitted location in the chamber, adjacent the two water pipe entry ports, on the chassis, are corresponding quick fit adaptors. This enables two external water pipes to enter the chamber and with complementary quick fit adaptors attach external water pipes to the heat pump. A plug is mounted on the heat-pump chassis adjacent the electrical socket port on the alternate side. A sealed electrical control module is located on the top front with, front facing controls and a display that aligns with the rectangular aperture on the front door.

The heat-pump includes a fixed displacement tube-in-fin evaporator (but with operational variable capacity) , a compressor, accumulator, a TX valve, or other cyclic control device, a condenser and a variable speed condenser magnetically or direct coupled water pump and associated piping, control sensors and actuators, a solid state sealed control module. The refrigerant employed may be a Hydrofluorocarbon (HFC) such as R134A alternatively a hydrocarbon (HC> such as R290 with mass of up to 250 grams.

In another aspect, the present invention resides broadly in energy recovery apparatus including an air chamber; an air intake passage arranged to provide fluid connection of the air chamber with a source of building envelope air; air pumping means mounted for pumping air from the source through the intake passage to the air chamber, the air pumping means having variable speed control; an air discharge orifice for discharging air from the air chamber; an air to water heat pump interposed between the source and the discharge orifices for extracting heat from the building envelope air to a mass of water; sensing includes sampling the condition of air being drawn into the air chamber for process management; control means and includes controlling the speed of the air pumping means; programming means for programming the control means to modulate the air flow rate to maximise the overall individual components induced by the air pumping means for higher temperature and moisture content of the domestic wet air and increasing air flow rate for lowe temperature and moisture content of the domestic wet air. The building envelope air is preferably moisture saturated air when available, or otherwise available building envelope air. However, it will be appreciated that the building envelope air may not be wet, or the air may be wet only if sourced from a bathroom, kitchen or laundry area or the like which is in use or operation at the time, eg., clothes drier.

The energy recovery apparatus according to the invention may be considered as an integral unit whose primary function is as an air-to-water heat pump. However unlike prior designs, the energy recovery apparatus according to the invention includes feedback loop control to optimize the performance of the compressor at 100% rated efficiency. Previous designs allow the compressor to cycle up from low load to a point of co-incidence of full load and thermostat cut out. By reducing the condenser water pump flow rate and thereby increasing head pressure, refrigerant temperature is raised to a level only achieved in prior designs close to thermostat cut out. From that point, as the water temperature circulated from the separate storage cylinder by the pump through the condenser rises, the head pressure is regulated by ^' increasing the water pump flow rate. A second feedback loop regulates the evaporator's primary energy scavenging capacity by increasing or decreasing the air flow rate of the centrifugal or selected fan. At lower air ambient temperatures, typically the air flow is increased to extract the maximum energy to maintain the compressor at as close to 100% operational efficiency as possible. At higher ambient temperatures and high latent heat loads, the fan can cycle down, again to regulate the energy available to the compressor. The net outcome is a relatively high coefficien of performance (COP), enabling reduction of compressor size whilst maintaining hot water recovery requirements.

The preferred option for refrigerant, hydrocarbon instead of a hydrofluorocarbon allows for higher condensing temperatures, reduction of refrigerant charge, and improved heat exchange rates in heat exchangers. This improves COP by up to 20% over conventional hydro luorocarbon (HFC) refrigerants and outright heating by up to 5%. Hydrocarbon refrigerants have a low global warming potential (G P) , typically 3, in contrast to 1300 for R134a HFC (1,1,1,2 tetrafluoroethane) . At a charge of 250 grams, this means the carbon footprint for HC refrigerant charged is 1.2 kg instead of 812 kg.

Using a natural refrigerant such as HC, it is suggested that the hot water heat pump (HWHP device) is future proofed against phase out of HFC refrigerants. However, HFC refrigerant will be offered as an option in the event that HC which as a class 3 flammable refrigerant ^υ cannot be used for compliance or other reasons, such as market acceptance or customer choice.

The H HP device is designed to minimise installation complications and cost. It is also designed for flexibility of air flow egress and ingress, compact physical size and low operational noise. It may be mounted up to 3 metres from the water storage vessel, additional length of piping may require a supplementary circulating pump and extended pipe kit. Once fitted, the case need never be removed. The initial install requires a qualified plumber and electrical mechanic. The plumber fits isolating valves external to the HWHP device. The plumber also fits a condensate drain that is piped to the the existing water heater pressure/temperature relief valve (PTR). drain.

For retrofit, it is suggested that the electrician intercepts the existing water heater wiring and fits a two- position and off switch. A 15 amp circuit breaker and general purpose outlet (GPO) arc fitted for the HWHP device, power supply wiring. The switch allows for selection between either the heat pump, or as a standby, the element in the original hot water heater. It is suggested that such switching not be automated but retained as an isolator and changeover separate to the appliance. The installation is documented with image and barcode details necessary for warranty and an after sales service database.

Device fault assessment is simplified for. the owner with a display (such as a light-emitting diode (LED) display) indicating operational status and such like. Service and replacement is simplified by virtue of the pop off front panel, quick fit water connectors, and socket and plug electrical connection, and the slide out chassis. Service may be conducted by trained personnel without plumbing, electrical or ref igeration qualifications. The electrical connection is isolated by unplugging at the GPO, the water is isolated by the two water valves, the front is "popped off" and laid aside, the two quick fit water connections are broken, the internal electrical plug and socket disconnected, and the complete chassis and heat pump is slid out in one piece. Note that any water in the condenser that drains out collects in the condensate drain base of the lower chamber. An exchange or replacement chassis may then be slid in, water pipes connected, the loop purged of air by sequence on connection, power connected internally, the front refitted, and externally the cord plugged in to the GPO and switched on.

It is believed that the above arrangement will minimise on-site time for service and a full change over should take less than 30 minutes. The chassis removed for service is then returned for centralised service or repair in batch with others and then returned for duty as an exchange in due course.

It is suggested that the energy recycling apparatus according to the present invention provides several advantages and features not present in the prior art, including a novel condenser heat exchanger, including the following: The construction is from a combination of proprietary materials, with conventional reversed direction flow for refrigerant and water. Also conventional, the refrigeran carrying tube i3 double skinned, the inner tube selected for inducing turbulence of refrigerant and an open to atmosphere fine tolerance air gap to outer tube that is in contact with circulating water. The arrangement is to comply with all relevant Australian Standards.

The class of heat exchanger is tube in shell, preferably as a novel coaxial double water pass with a single refrigerant pass heat exchanger, the primary water pass has induced partial helical flow interacting with laminar flow to turbulate water for enhanced heat exchange. The laminar flow swept area is of sufficient capacity to reduce internal dynamic head at maximum rated water flow to a point where it has no effective dynamic head enabling a smaller circulating pump to be employed. The second pass is at very low velocity again with no effective dynamic head, heat exchanging with a tubular sink . with tight tolerances to the inside of the helical refrigerant pass coil. An advantage over tube-in-tube heat exchangers is that there is no trade off between dynamic head increase and reduction of water velocity where the water has a close temperature gain gradient.

Compressor management is also optimized. Conventional air to water heat pumps operate with fixed compressor, condenser and evaporator design. In some cases a variable control in the form of a TX valve is provided which allows the unit to operate in a wider range of ambient temperatures. As the externalities vary and cycle, such as ambient air temperature and heated water temperature, the relative COP of the heat pump falls or rises. On aspect of novelty in this device is the manner in which control management maintains the electric motor and compressor at rated design optimum efficiency. To optimize compressor output, the externalities are scanned and the air flow at the evaporator and water flow output at the condenser are varied to constantly optimize the compressor to full load. Management control takes into account the possibility of the system "hunting" because of conflicting parameters. Mitigation of hunting is managed by initiating priorities . In a preferred form, "plug and play" on site servicing is provided. Recognizing the potential for service costs over the lifetime of a low energy water heater to be higher than the recurrent operational costs; and recognizing the relative high cost or service visits and on site labour, the device is designed with fast chassis changeover ability. The chassis assembly can be disconnected from externals, removed, and a replacement chassis fitted and connected in a service site visit of 30 minutes. An advantage of returning systems for service or fault rectification is that there Is a continual feedback capable of identifying quality, manufacturing, and design issues. From being alerted to a design or manufacture quality issue, design and manuf cture changes can b ' fast tracked for improvement. Further, any exchange systems returned for service can be upgraded rather than just serviced.

Although the invention has been described with reference to a specific example, it will be appreciated by persons skilled in the art that the invention may be embodied in other forms within the broad scope and ambit of the invention as herein set forth and defined by the following claims.

Claims

THE CLAIMS DEFINING THE INVENTION FOLLOW:

1. An energy recycling system fo domestic hot water including: an air chamber enclosed by a chambe housing having a chamber wall; an air intake inlet penetrating the chamber wall to the air chamber and arranged to provide fluid communication between the air chamber and a source of domestic building envelope air; air pumping means associated with the air intake inlet for pumping air from the source through the intake to the air chamber; an air discharge outlet penetrating the chamber wall for discharging air from the air chamber/ an air to water heat pump interposed between the source of domestic building envelope air and the discharge outlet for pumping heat from the domestic building envelope air to heat transfer means, and a water heater operatively associated with the heat transfer means and operable to transfer heat to the domestic hot water.

2. The energy recycling system according to Claim 1, wherein the building envelope air is selectively directed from areas which are, or are likely to be, moisture saturated or heated or both.

3. The energy recycling system according to Claim 2, wherein the ntake inlet includes an intake passage through which the domestic building envelope air may pass.

4. The energy recycling system according to Claim 3, wherein the discharge outlet includes a discharge orifice in fluid communication with ducting to direct spent air into the building or outside the building and through which the air processed by the apparatus may be discharged.

5. The energy recycling system according to Claim 4, wherein the air intake passage, air pumping means, air discharge orifice and air to water heat pump are embodied in a blower apparatus.

6. The energy recycling system according to Claim 5, wherein the blower apparatus is sized to fit atop a typical domestic water heater.

7. The energy recycling system according to Claim 6, wherein the heat pump has a hot side cooperatively associated with the water heater for heating the water to be used as hot water.

8. The energy recycling system according to Claim 6 or Claim 7, wherein the blower apparatus is of a physical size that allows installation in typical apartment adjacent an existing hot water heater cylinder within the apartment.

9. The energy recycling system according to Claim 8, wherein the blower is powered by an electric motor and a control system is electrically connected to the electric motor for controlling the blower apparatus, the control system being so arranged that it may be customised for individual apartment hot water requirements .

10. The energy recycling system according to Claim 9, wherein the control system has service and fault alert diagnostics operable to provide a owner with information.

11. The energy recycling system according to Claim 10, wherein the blower apparatus is formed as a modular unit being a heater only with no integral storage cylinder.

12. The energy recycling system according to Claim 11, wherein the modular unit has an internal or external pump for circulating heating water through a storage cylinder.