GB2449498A

GB2449498A - Heating system for retrofitting to a building

Info

Publication number: GB2449498A
Application number: GB0710067A
Authority: GB
Inventors: Stephen Edward Ellwood
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-05-25
Filing date: 2007-05-25
Publication date: 2008-11-26
Anticipated expiration: 2027-05-25
Also published as: GB0710067D0; GB2449498B

Abstract

A heating system for retrofitting to a building comprises a set of ducts for connecting to rooms or zones of a building, an inlet manifold coupled to a first subset of the ducts for extracting heat from the rooms or zones, an outlet manifold coupled to a second subset of the ducts and configured to deliver heat to the rooms or zones, at least one heat extraction device coupled between the inlet and outlet manifolds to recover extracted heat for the delivery to the rooms or zones. The system also comprises a plurality of temperature sensors to sense temperature of the rooms or zones, a plurality of occupancy sensors to detect occupancy of the rooms or zones, and a controller coupled to the temperature and occupancy sensors and outlet manifold to distribute heat between the rooms or zones. The heat extraction device may be a heat pump or heat exchanger. A solar heating system, which may be a roof tile incorporating a solar collector to heat the delivery air may be coupled between the inlet and outlet manifolds and a water circuit linking the heat extraction device to a radiator (fig 3) may be used for heating the delivery air to be passed to the rooms or zones. An additional heat extraction device may be provided to extract heat for heating a pre-existing water tank.

Description

Heating Systems

FIELD OF TilE INVENTION

This invention relates to heating systems, in particular to systems designed for retrofitting to a domestic dwelling to reduce carbon emissions.

BACKGROUND TO THE INVENTION

Aspects of the invention relate to apparatus, methods, controllers, computer program code and solar collectors.

There is a desire to reduce carbon emissions by a substantial percentage in order to address questions of climate change or global warming. In particular the UK Government has made a commitment under the Kyoto initiative of 2005 to reduce carbon dioxide emissions by at least 60% by 2050. This target is very challenging, in particular given the legacy of relatively inefficient heating already installed in UK housing stock. Other countries have similar problems.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is Ihereibre provided A heating system fbr retrofitting to a building to reduce a carbon footprint of the building, the system comprising: a set of ducts for connecting to rooms or zones of said building; an inlet manifold coupled to a first subset of said ducts for extracting heat from said rooms or zones; an outlet manifold coupled to a second subset of' said ducts and configured to cnable selective delivery of heat to ones of said rooms or zones; at least one heat extraction device coupled between said inlet manifold and said outlet manifold to recover said extracted heat for said selective delivery; a plurality of temperature sensors to sense temperatures in said rooms or zones; a plurality of room or zone occupancy sensors to detect occupancy of said rooms or zones; and a controller coupled to said temperature sensors, to said occupancy means, and to said outlet manifold, for selectively redistributing heat between said rooms or zones.

In preferred embodiments the ducts comprise air ducts and air is employed as a working fluid of the retro-fitted heating system. This provides a number of significant advantages, in particular because air heating can employ relatively low temperatures, for example less than 50 C or less than 40 C and still achieve efficient heating whereas water filled radiators typically require much higher temperatures because of their limited radiating surface. Use of lower temperatures facilitates the use of an efficient heat extract device, in particular a heat pump, which may have a co-efficient of perfbrmance (power in: power out) of better than 3:1, 4:1 or 5:1). In some preferred embodiments a heat exchanger is employed in addition to a heat pump to heat air delivered to the outlet manifold using air from the inlet manifold prior to passing the (now cooler) air from the inlet manifold through the heat pump. In some preferred embodiments the heat pump comprises an electrical heat pump.

In preferred embodiments, therefore, the controller is configured to selectively reduce a temperature in a room or zone when it is unoccupied and to selectively heat reheat the room or zone when it is reoccupied, using the extracted heat. Thus forced re-heating may be employed to rapidly increase the temperature of a room or zone the moment it is re-occupied. This rapid heating can he ef!ècted firstly because, in preferred embodiments, the controller is able to control the legacy heating system, typically a boiler with controllable-valve radiators, to preferentially direct heat to the room which has just become re-occupied. however, secondly and more significantly, the retro-fitted hot air heating system can be used for rapid re-heating of a re-occupied room or zone and, moreover this can he achieved without a signilicant total power capacity since the hot air may be selectively directed to where it is needed. Thus in embodiments, for example, a room or zone may be heated to within 1 C of a target temperature within at least 30 minutes, preferably within 20, 15 or 10 minutes. In this way the need for large overall capacity may be substantially reduced.

The relatively reduced total capacity requirement also facilitate the use of a solar heating system. Moreover because in embodiments air is used as the working fluid a solar collector of the solar heating system need only raise the air temperature to a relatively modest temperature, as previously mentioned, by comparison with a water-based solar heating system. Preferably, therefore, a solar collector or collector array is selectively coupleable between the inlet and outlet manifolds to enable the system to rely at least partly on solar power, when available (in embodiments of the system useful amounts of solar power may be available in the UK at most times of year except winter).

Embodiments of the system also facilitate redirecting of an uncontrolled heat source such as a fire or log burner to supplement heat from the heat pump and/or heat exchanger and/or solar collector. Embodiments of the system thus implement a three-tier approach, that is in which the system is able to employ a selected one or more of three modes, a base heating system mode (boiler and any uncontrolled heat sources), a recovery mode (using a heat pump) and a solar mode, embodiments of the system enabling the use of one, two or all three modes simultaneously.

Preferred embodiments of the system also include one or more water circuits linking the heat extraction device (more particularly the heat pump) to the outlet manifold, more particularly to a radiator for heating air for delivery by the outlet manifold. Broadly speaking in preferred embodiments a water circuit is provided to link all heat sources with all heat sinks except for solar air heating (where the air circuit performs this function) and heating of a hot water tank by the base or legacy system (boiler).

Preferably, therefore, the heating system includes a heat extraction device such as a radiator to extract heat from the air for heating a pre-existing hot water tank of the legacy system, for example to supplement the existing system.

One further advantage of the above-described selective heating supplementing a legacy heating system is that the air ducts may be relatively small compared with, for example, an air duct heating system used as the sole source of heat for a room or zone. Thus in embodiments the air ducts have a cross-sectional area of less than 500 cm2, 400 cm2, 300 cm2, 200 cm2 or 100 cm2.

In a related aspect the invention provides a method of heating a house, the house comprising a heating system conligured to enable heat from a heat source to be directed selectively to rooms or zones of said house, the method comprising: sensing which of said rooms or zones of said house are occupied; controlling said heating system to reduce the temperature in an unoccupied said room or zone to below a target temperature for an occupied said room or zone; detecting when a said room or zone becomes occupied and, responsive to said detecting, controlling said heating system to rapidly reheat said re-occupied room or zone by selectively directing heat from said heat source and from one or more additional heat sources to said re-occupied room or zone.

In some preferred embodiments a heating controller learns an occupancy profile of some or all of the rooms or zones, for example comprising a pattern of probability of occupation of a room or zone over time. For example particular rooms of a house such as a lounge, kitchen, bathroom, bedroom, dining room and so forth tend to be used at particular times of day and thus a system can learn to anticipate where one or more people are likely to be present and hence a controller heating system in response to this.

For example heating may be turned up in anticipation of a room or zone being occupied or, more preferably, the temperature of an unoccupied room or zone may be reduced to a degree dependent upon the probability of occupancy of the room so that if it is unlikely a room is occupied the temperature can be reduced significantly whereas if it is relatively likely that a room is occupied temperature can be reduced only slightly. This facilitates rapidly bringing the room temperature up to the target, desired temperature.

It would be appreciated that an occupancy pattern may be learned over a period of more than 24 hours, for example 7 days, one month or even, potentially one year since often occupancy patterns may be different over a weekend as compared with week days.

In a similar way in some preferred embodiments the controller is also able to learn a transient response of re-heating of a room or zone by monitoring the change in temperature of the room or zone, optionally further taking into account heat input or types of heat source available, for example whether or not solar heating is employed.

The invention further provides processor control code to implement the above-described methods, in particular on a data carrier such as a disk, CD-or DVD-ROM, programmed memory such as read-only memory (Firmware), or on a data carrier such as an optical or electrical signal carrier. Code (and/or data) to implement embodiments of the invention may comprise source, object or executable code in a conventional programming language (interpreted or compiled) such as C, or assembly code, code for setting up or controlling an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array), or code for a hardware description language such as Verilog (Trade Mark) or VHDL (Very high speed integrated circuit Hardware Description Language). As the skilled person will appreciate such code and/or data may he distributed between a plurality of coupled components in communication with one another.

In a related further aspect the invention further provides a heating system controller for controlling a heating system configured to enable heat from a heat source to be directed selectively to rooms or zones of a building, the controller comprising: means for sensing which of said rooms or zones of said house arc occupied; means for controlling said heating system to reduce the temperature in an unoccupied said room or zone to below a target temperature for an occupied said room or zone; means for detecting when a said room or zone becomes occupied; and means for controlling said heating system responsive to said detecting to rapidly reheat said re-occupied room or zone by selectively directing heat from said heat source and from one or more additional heat sources to said re-occupied room or zone.

The invention still further provides a controller for a heating system, the controller comprising: an input for a plurality of temperature sensors to sense temperatures in said rooms or zones; an input for a plurality of room or zone occupancy sensors to detect occupancy of said rooms or zones; an output tbr controlling said selective delivery by said outlet manifold; and a processor coupled to receive signals from said temperature and occupancy sensors and coupled to said output and configured to control said outlet manifold to selectively redistribute heat between said rooms or zones responsive to said sensed temperatures and occupancies.

The skilled person will appreciate that, depending upon the implementation; a common communications system may be employed to provide inputs for both the temperature and occupancy sensors, for example a wireless communications system.

In some particularly preferred embodiments the controller also has a secure, encrypted communications link, for example based on SSL (Secure Sockets Layer) tecimology, to enable the controller to communicate with an electricity power supply company. This is particularly advantageous in embodiments which employ a heat pump since even with a relatively low power device, for example of order of 500 watts, large scale deployment of the system has the potential to put a significant extra burden on electricity supply.

Thus in embodiments the controller is able to report electrical power consumption of the heating system, more particularly of a heat pump of the heating system, to such a power supply company. In particularly preferred embodiments, however, the controller is configured to enable negotiation with the power supply company, for example to allow the power supply company to control or define a time or period when use of the additional heating system, more particularly use of the heat pump or use of electrical power above a threshold value such as 200 watts, 500 watts, or 1 kilowatt, is permitted or not permitted. In this way a power supply company can manage the additional burden on the national grid so that in, say, initial phases of the system's deployment use of the heat pump may only be permitted at certain times of day or when the electricity supply cornpaiy deteriniiies that overall demand is such that use of heat pumps can be tolerated. It will he appreciated that such control be performed by time and/or geography or connectivity to local or national supplies.

Thus in a further aspect the invention provides a home heating controller for controlling a domestic heating system, wherein the controller comprises a secure communications link for communicating with an electricity power supply company for negotiating an electrical power consumption of said heating system with said power supply company.

As previously mentioned, it is particularly advantageous to employ air as the working fluid, and it is desirable to be able to implement a system which can be relatively straightforwardly retro-fitted to an existing house.

Thus in a still further aspect there is provided a roof tile incorporating a solar collector, and wherein said solar collector is configured to use air as a heal transfer working fluid.

Preferably the solar collector includes a heal exchanger which projects at the back of the tile, the tile having a border on at least the upper and lower edges (when fixed to the roof) to allow the tiles to be filled together one above another on a roof whilst leaving a gap for a roof truss between the tiles, for example of at least 1, 2, 3, 5 ems or more.

Further preferably the tile tapers in thickness toward the top edge so that, when mounted on a roof a rear surface of the collector may be substantially parallel to the roof pitch, which again facilitates retrofitting. Further preferably the solar collector incorporates a steel heat exchanger, which can be used efficiently in a device in which air is used as a working heat transfer fluid since the temperature differentials are relatively low, thus providing a low cost, robust tile.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will now he further described, by way of example only, with reference to the accompanying figures in which: Figure 1 shows a air based solar collector according to an embodiment of an aspect of the invention.

Figure 2 shows one of the more complex implementations of the air circuit. The left of the drawing is common to all installations. The right (starting from the manifolds) depends on the number of zones defined. In this example 8 zones arc defined.

Figure 3 shows the additional water circuit for the heating system over and above the previously installed hot water and central beating system.

Figure 4 shows the control circuit Figure 5 shows an example total energy profile for an average sized detached dwelling.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

COMPONENTS

The system controller is central to the heating system. it is preferably a low power, single chip embedded microcomputer running a program in ROM either internal or external to the device. The system controller has interfaces that provide the input stimuli and output control signals including the user interface and optional service provider interfaces.

The control interface is connected to a network of sensors. The sensors give the controller the following information: The time of day or night The outside temperature The amount of solar heating available fbr use The temperature of each zone The occupancy of each zone The status of the hot water cylinder The status of each controlled energy source The outgoing air temperature from the ventilation system The control interface is connected to a network of actuators. The actuators allow the control circuit to control every aspect of the heating system. The actuators control: The master onloff control for each controlled energy source Individual zone controls for each controlled energy source Configuration of the water circuit Configuration of air circuit Fan speeds of the master air fans Fan speed of the individual zone air fans On/off and direction of heat pump heat transfer Control of DC supply The controller preferably utilises a 1 OOMbit/second full duplex signalling rate using I OOBaseT as the transmission medium over Category 5 Ethernet cable. The controller is preferably connected to the Local Area Network (LAN) of the dwelling and has a WEB based interface to a PC for configuration and monitoring by the occupants. Remote sensors and/or actuators are preferably connected to a POE enabled Ethernet huh and utilise a lOMbit/second full duplex signalling rate usinglOBaseT as the transmission medium over Category 5 Ethernet cable. The Ethernet switch is cable of auto sensing and communicating between lOMbit/second devices and I O0Mbilisecond devices. The outstations communicate with a Control Interface by means ola simple UDP (User Datagram Protocol) message set. The Ethernet switch prevents individual outstations from being swamped with TCP-TP traffic. The controller terminates the UDP packets and utilised the information so gathered as input to the control program running on the Controller.

Preferably the controller will have a secure interface to allow service providers with pre-defined access rights to communicate with the controller. Should there be a sudden surge in demand for electricity the remote server could request the controller to reduce its electrical load, thus alleviating the grid energy deficit. Additionally a reverse channel back to the Electricity Provider could warn of impending usage by the product allowing the whole national grid time to react as devices turn on.

The heating system is designed for the retrofit market. In the majority of retrofit situations a pre-existing heating system will be present. In order to achieve energy savings the system controller must allow the temperature in unoccupied rooms to fall below what the occupants would consider a minimum liveable temperature. This will only be acceptable to the occupant if the minimum liveable temperature can be re-established quickly upon entering the room. It is almost certainly the case that there is not sufficient overcapacity in the pre-existing heating system to allow the liveable temperature to be re-established in an acceptable time. To achieve this a second high thermal capacity heat source, the hot air system is part of the heating system. This hot air system will preferably be sized to supply 80% or more energy than the pre-existing heating system on a zone by zone basis, allowing rapid room temperature increases to be achieved.

Modifications will be made to the pre-existing heating system to allow control of this equipment to be taken over by the new controller, both centrally and zone by zone as required. This modified system shall be referred to as the Base Heating System (BHS).

Previously installed central heating will typically supply 1 30% to 1 50% of dwelling worst case winter heating requirements; this will not present a problem for the controller, which will learn this and use the BHS accordingly. The BHS will be used to supply heat only when there is insufficient solar energy and heat recovery energy available.

A solar thermal array will preferably be included within the heating system for collection of incident solar radiation on suitable days. The solar array will preferably be sized to supply around 20% of the total heat requirement on a cold but sunny winter's day. For a typical I 50m2 dwelling an array with an aperture of 5m2 is suitable. The preferred heat carrying medium is air for the reason that air does not freeze in sub-zero temperatures, does not boil when subjected to high temperatures and therefore can tolerate zero flow for extended periods of time. The system topology could be realised with a water based solar collector providing the system provides some mechanism for coping with energy overcapacity in summer.

A suitable solar collector would take the form of a solar roof tile that is fully compatible with standard concrete roof tile systems. Specifically the solar tile would typically be the same height as a standard roof tile but four or five times wider so as to be able to straddle several roof joists. Ihe collector is fuily integrated into the roof and becomes part of the roof structure such that the roof is not compromised by having to take water or air connections from the outside of the roof to the inside. A galvanised steel collector is used. It is cheaper than either aluminium or copper and has far greater strength for the same thickness of material without a significant degradation in efficiency. A simple folded galvanised steel heat exchanger is welded to the back of the collector and transfers the solar energy into the air surrounding the heat exchanger. A galvanised steel back plate is used as a substitute for the felt system and provides a transition back to roofing felt at its lower edge. Insulation is used behind the back plate to prevent heat loss into the loft space. The tile is profiled so as to be thicker at the bottom than at the top such that the solar collector presents a near continuous flat surface to the underside of the roof. With roofjoists set at 300mm centres and a tile height of 400mm the system is suitable for deployment in arrays from 3 tiles to 10 tiles in height or

II

approximately I to 4 linear meters. The output per tray (300mm wide track, 4 meters long) will be approximately 900W peak after loss due to the transrnissivity of the glass.

This will generate a 40 C rise in the transmission medium with an air flow rate of I 9litres/s, 68m3/hour. The air velocity across the collector will be approximately 0.75m!s peak. An array equal to 2 tiles wide by 12 tiles high will span 4 trays with a collector surface area of 4.8m2 and will capture approximately 3.5kW peak. Loss through the insulation will be of the order of 50W or 1.5% of the total incident radiation if incoming air is at ambient temperature.

Figure 1 shows a air based solar collector according to an embodiment of an aspect of the invention.

Preferably a heat recovery system is included in the system. The heat recovery system comprises an air to air cross-flow heat exchanger to recover heat from outgoing, stale air and transfer it to incoming, fresh air and a reversible air-water heat pump capable.

The combination is sized to provide 30% or more of dwelling worst case winter space heating. Heal recovery ventilation is a natural part of the heat recovery unit. The heat recovery system will be fully controlled by the HTC.

The energy required to run the product (possibly including the heat pump) will preferably be arranged to be low voltage DC and could be powered from a renewable energy source. A PV array or wind turbine could supply low voltage DC power to fans, solenoids and control circuitry.

TOPOLOGY

The following is an appraisal of the operation of the product. The temperatures described are used only for the purposes of illustrating the operation of the product and are not representative of final system parameters.

The preferred product topology logically comprises three "circuits" which are an air circuit, a water circuit and a control circuit. These circuits arc interdependent and together create the heating system.

The air circuit resembles a typical HVAC system with some extensions. An air based solar thermal array can either be switched into the incoming air stream (air selector in position shown), or can operate as a completely independent loop (air selector in opposite state). Fans are placed at the output of the inlet manifold and are individually speed controlled by the control circuit to vary the flow and therefore the amount of heating to each zone. Preferably downstairs rooms that require the most heat are heated directly, with a return air path through the hail. Bedrooms have the opposite conliguration. This saves on air ducting. The hail exhaust vent can be closed at night so that downstairs air naturally travels upwards. Wet rooms that need high air change rates for moisture extraction preferably have both inlet and outlet manifolds.

Figure 2 shows an air Circuit Block Diagram for a Large Dwelling. The water circuits connects three heat inputs from the BFIS, the heat pump water output and the Solar Thermal Array to two heat outputs to space heating and hot water.

Figure 3 shows a Water Circuit Block Diagram. Preferably the water circuit can operate as two completely independent circuits. Radiator 1 is used to heat or cool the incoming air in the air circuit. With water valve 2 in position B' Radiator I can take heat from the BHS; In position A' Radiator 1 can heat or cool (when the heat pump is in cooling mode) by virtue of being connected via the heat pump. Note that there is no requirement to connect Radiator 2 output to Radiator 1 input as this is already achieved using the air circuit.

The hot water cylinder connection has a similarly flexible arrangement. With water valve 1 in position A' the hot water system can take heat from the Solar Thermal Array via Radiator 2; In position B' the hot water cylinder can heated (or cooled, though the latter is not generally useful) using the heat pump. Note that there is no requirement to connect the I3HS to the hot water cylinder as it is assumed that this is already a function olthe (legacy) BHS.

The partitioning between the air circuit and water circuit is a particular feature of this design. A water based Solar Thermal Array could have been used; this would have simplified the air circuit but added complexity to the water circuit. Water to water heat pumps are available as are air to air heat pumps with similar tradeoffs as above.

Figure 4 shows the Control Circuit. In preferred embodiments the control circuit is based around EthernetTM LAN technology. The wiring between devices is Category 5 Ethernet cable, wired to an Ethernet patch panel. DC power to the Zone Controllers is fed via the spare wires in the cable according to the Power Over Ethernet (POE) standard. A commodity 10/100 Ethernet switch completes the picture and provides an interface to the main LAN and/or the dwellings internet connection. Wireless connectivity can also be provided as an option depending upon customer preferences.

The Zone Controllers are built using a 1 OBaseT Ethernet enabled PICTM or similar device. In a simple form it comprises a PIR detector configured for reliable detection of room occupants and a temperature detector with an accuracy of +0.5 C and a resolution of 0.25 C. Preferably a simple indicator system allows feedback to the occupants.

DC Power for the system can be derived either from an AC-DC converter or, optionally, from a renewable DC power source.

OPERATION

The fact that the controller does not need to heat the whole house simultaneously creates generous overcapacity on a zone by zone basis. The controller is aware of the instantaneous energy cost of each heat source, its instantaneous capacity and its impact on the environment particularly with regard to carbon efficiency and uses an algorithm to balance heat demand, cost of energy supply and environmental parameters. The controller electronically configures the heating system according to the outside temperature, whether dwelling is calling for heating or cooling, whether the water in the hot water cylinder needs heating or not and whether the output of the solar array is at a use lId temperature or not.

On cold sunny days there will be a need to heat the inside of the dwelling to maintain a liveable temperature. The BHS will provide abaseline level of heating as required. In the steady state the air inside the dwelling will be warmer than the outside air. Fresh incoming air, say at 1 C, is brought in through the heat exchanger and is preheated by the wanner outgoing stale air to 13 C. The air is then redirected through the air selector and through Radiator 2 fan and Radiator 2 which in this case has no water flow SO contributes nothing. The air then passes over the collector of the solar array and gains solar energy. The incoming air should now be at a useable temperature but if it is not it can be topped up by a water connection between Radiator 1 and the BUS to 30 C or more. The ventilation air now contains enough heat energy to remove a significant load from the BuS. As the air transfers its energy into its surroundings it cools and the now stale air is removed at around 18 C. The air finally passes again through the heat exchanger giving up even more heat to the new incoming air and the cycle repeats.

Before finally being discharged to the atmosphere the outgoing air, still at 8 C, is used as a source of heat energy for the heat pump, which is configured to cool its air connection and heat its water connection. The heat thus recovered is used to provide hot water while producing substantially lower CO2 than would have been the case with a fossil luel boiler (the BHS) or using electricity directly. The water circuit can also be configured such that Radiator 1 can be topped up by the heat pump water output if hot water is not being called for.

In cold overcast conditions the solar array will produce little or no solar gain. In this circumstance Radiator 2 fan is not driven and the air circulation is stopped. The ventilation loop runs as on sunny days except that the solar array is cut out oIthe loop.

In conditions where the BuS and heat pump are used at the same time, the controller will configure itself such that the heat pump is running with the minimum temperature lift so as to maxiniisc the COP.

On sunny days in summer there will be a need to cool the inside of the dwelling to maintain a liveable temperature. In the steady state the occupants will benefit from the air inside the dwelling being cooler than the outside air. Fresh incoming air at, say 30 C is brought in through the heat exchanger and gets pre-chilled by the cooler outgoing stale air down to 24 C. The heat pump is configured to cool its water connection and heat its air connection. The cold water from the heat pump passes through Radiator 1 and provides additional cooling to the incoming air down to 9 C. The heat extracted by the heat pump is transferred to the outgoing stale air and out into the atmosphere. The now chilled incoming air is distributed by the manifold fans to cool those rooms that are occupied.

The heat from the solar array will be several kW in full summer sun. This is directed via the air selector to Radiator 2 where it is transferred into the water system. The water circuit is so designed such that at the same time as carrying cold water between the heat pump and Radiator 1, it can carry hot water between radiator 2 and the hot water cylinder. An ample supply of free and more importantly zero CO2 hot water is 1)rOduced.

In warm but overcast conditions the Solar Array will produce little or no solar gain. In this circumstance Radiator 2 fan is not driven and the air circulation is stopped. The ventilation systems runs without heating or cooling, simply replacing the stale air with fresh air. The outgoing air is used as a source of heat energy for the heat pump, which is configured to cool its air connection and heat its water connection. The heat thus recovered is used to provide hot water while producing substantially lower CO2 than would have been the case with a fossil fuel boiler or using electricity directly.

Pseudo code for operation of a heat targeting algorithm of a preferred embodiment of the system is given below. (l'hc skilled person will understand that embodiments may also include code to implement other features, for example an SSL communications protocol, as mentioned elsewhere in this specification).

main_control_loop: # Calculate nominal and HTC heat values # ref heat required to achieve internal house temperature hot_in = get_exhaust_air tempo cold_in = get_outside air tempo cold_out, hot_out = Heat_exch.Find exch exit t(cold in, hot_in) time = now() panel_kW Sol_panel.output() if (cold in <hot_in): # outside temperature is lower than inside temperature, # we are nominally in heating mode.

# map available recovery power available based on air temperatures recovcrykW = Recovery_unit.Space heat(cold out, hot_out, hot_in) zone error = False for zone in dwelling: if is_occupied(zone): zone is occupied make temperature liveable rqdtemp(zonc) = USER_TEMP HEAT(zone, time) elif is_likely_occupied(zone, now): zone is un-occupied but is likely to be occupied soon rqd_temp(zone) = USER_TEMP HEAT(zone,time) -SAFE_BACKOFF(zone, time) else: rqd_temp(zone) MIIN_TEMP(zone, time) if (get_zone_temp(zone) <rqd_ternp(zone) -1.0): zone error = True if (zone error = l'rue): # we are not in steady state, throw all available heat into required zones solarsh 1DM = 1 solar_hw_TDM = 0 recovery shTDM = 1 recovery hwTDM = 0 # do we also need BHS to get accelerate temperature rise? rqd_kw = gel_excess_energy(zone tempO,get zone tempO, cold_in) if (rqd_kw> panel_kW + rccovcry_kW): BI1SshTDM = 1 BHShwTDM 0 else: BHSsbTDM =0 BHShwTDM = 1 else: # we are in steady state # find heat required based on zone requirements rqd_sh_kW = get_HTC_heatloss(zone tempO,get zone tempO, cold in) #split any available solar heat between space heating and hot water use for heat first, remaining heat can be used for hw heating? if (panel_kW > rqd_sh_kW): we have spare solar, use spare to heat water sol ar_sh_TDM = rqd_sh_kW/panelkW solar_hw_TDM (1 -rqd_sh_kW)/panel_kW rqd_sh_kW = 0 else: # use all for space heating solarshTDM = 1 solar_hw_TDM = 0 rqd_sh_kW = rqd_sh_kW -panel_kW # now do the same for recovery energy if (recovery_kW> rqd_sh_kW): # we have spare recovery, use spare to heat water recovery_sh_TDM rqd_sh_kW/rccovery_kW recovery_hw_TDM = (1 -rqd_sh_kW)/recoverykW rqd_sh_kW = 0 else: use all for space heating recovery_shJDM = 1 recovery_hw_TDM 0 rqd_sh_kW = rqd_sh_kW -recovery_kW # remainder must be supplied by BUS BI IS_sh_TDM = rqd_sh_kW/BHS_kW BHS_hw_TDM (1-rqd_sb_kW)/BHS_kW else: we need cooling from HVAC # map available recovery power available based on air temperatures recovery_kW = Recovery_unit. Space_cool(cold_out, hot_out, hot in) zone_error = False for zone in dwelling: if isoccupied(zone): zone is occupied make temperature liveable rqd_temp(zone) = U SER_TEMP_COOL(zone, time) elif is_likely_occupied(zone, now): zone is un-occupied but is likely to he occupied soon rqd_temp(zone) = USER_TEMP COOL(zone,tirne) + SAFE_BACKOFF(zone, time) else: rqd_lemp(zone) = MAX TEMP(zone, time) if (get_zone_ternp(zone) < rqd temp(zone) + 1.0): zone error = True # calculate cooling required rqd_sc_kW = get HTC heatloss(zone ternpQ,get zone tempO, cold in) if (zone error True or rqd_sc_kW > recovcrykW): recovery_sc_TDM = I recovery_hw_TDM 0 else: recovery_sc_TDM rqd_sc_kW/recoverykW recovery_hw_'l'DM = (1 -rqdsckW)/recoverykW BHSshTDM 0 BHShwTDM solarshTDM = 0 solahwTDM = I # calculate hot water configuration if (get_tank_temp(top)> IIW_MIN): BI1ShwTDM = 0 if (get_tank_ternp(bottorn) > HW_MAX): solar hw 1DM 0 Recovery_hw_TDM = 0 # now we know how to set all the outputs Sct_outputs()

EXAMPLE PERFORMANCE

Computer simulations based on a typical dwelling calculated that the I1TC mitigated 19% of the total space heating energy or 14.4% of the total hot water and space heating energy over a 10 year period based on representative zone usage profiles. The nominal heating period, against which the above saving was estimated, was forced to 18 hours in the simulation by artificially forcing all room temperatures in the simulated dwelling to 16 C at night. The following chart generated by the simulation illustrates a typical annual breakdown of total energy utilisation: Figure 5 shows an Example Annual Total Energy Profile. The chart illustrates the operation of the whole system. The daily energy requirement can clearly be seen from tracing along the peaks. The utilised solar energy (in yellow) is present all year round and supplies the majority of the energy required from day 121 to day 253; roughly the middle 4 months of the year. An unseasonably warm patch around day 109 sees use of the BHS being discontinued; an unseasonably cold patch around day 115 shows the BHS being required. In general on sunny days, the recovery energy is higher than normal and the BHS energy reduces significantly. Several small red lines representing BI-IS energy can be seen on the chart even during the summer. This is an artefact of the simplified HTC algorithm used in the simulation. Much of this will be mitigated using a more sophisticated HTC algorithm for an even greater saving.

The simulation shows the hot water energy breakdown is roughly 39% by Solar, 39% by BHS and 22% by the recovery unit. Space heating shows a different ratio with roughly 7% solar, 21% by BI-IS and the remainder by the recovery unit.

The C02 saving in this simulation run was as follows: Solar energy displacement 13.9% Heat recovery 3 0.2% Not heating unoccupied rooms 14.4% Totaf Saving 58.4% The fuel bill was estimated to he 487 per year based on a condensing gas boiler and 271 total for both electricity and gas with the new product. The real dwelling upon which the simulation is based uses a relatively new oil boiler and has a seasonal oil cost of around 600 per year.

The peak efficiency of a condensing gas boiler is as high as 97%. The boiler is less efficient when operating at part load, exacerbated when the boiler is oversized.

Additionally, research has shown that domestic central heating circulation pumps also consume up to 15% of the household total annually. The controller can optimise both boiler efficiency and circulator efficiency by calling for BHS heat at specific times only and using the other heat sources as a fill in.

The average electricity consumption of the dwelling increases from 4200kWh/year to around 6700kWhlyear; an annual increase of 60%. The peak loading will increase by approximately 80%. The SSL tecirnology can be used to mitigate this until generation capacity is available.

No doubt many other effective alternatives will occur to the skilled person. It will be understood that the invention is not limited to the described embodiments and encompasses modifications apparent to those skilled in the art lying within the spirit and scope of the claims appended hereto.

Claims

CLAIMS: 1. A heating system for retrofitting to a building to reduce a

carbon footprint of the building, the system comprising: a set of ducts for connecting to rooms or zones of said building; an inlet manifold coupled to a first subset of said ducts for extracting heat from said rooms or zones; an outlet manifold coupled to a second subset of said ducts and configured to enable selective delivery of heat to ones of said rooms or zones; at least one heat extraction device coupled between said inlet manifold and said outlet manifold to recover said extracted heat for said selective delivery; a plurality of temperature sensors to sense temperatures in said rooms or zones; a plurality of room or zone occupancy sensors to detect occupancy of said rooms or zones; and a controller coupled to said temperature sensors, to said occupancy means, and to said outlet manifold, for selectively redistributing heat between said rooms or zones.
2. A heating system as claimed in claim 1 wherein said ducts comprise air ducts.
3. A heating system as claimed in claim 1 or 2 wherein said controller is configured to selectively reduce a temperature in a said room or zone when a said room or zone is unoccupied and to selectively reheat a said room or zone when the room or zone is re-occupied, using said extracted heat.
4. A heating system as claimed in claim 1, 2 or 3 wherein said at least one heat extraction device comprises a heat pump.
5. A heating system as claimed in claim 1, 2, 3 or 4 wherein said at least one heat extraction device includes a heat exchanger. -
6. A heating system as claimed in any one of claims 1 to 5 further comprising a solar heating system selectively coupleable between said inlet and outlet manifolds, and wherein said controller is configured to control said selective coupling.
7. A heating system as claimed in any one of claims I to 6 further comprising a solar heating system, wherein said ducts comprise air ducts, and wherein said solar heating system includes a solar collector having air in said air ducts as a working fluid.
8. A heating system as claimed in any one of claims I to 7 wherein said ducts comprise air ducts, the system further comprising a water circuit linking said at least one heat extraction device to a radiator for heating air for delivery by said outlet manifold.
9. A heating system as claimed in any one of claims I to 8 further comprising at least one additional heat extraction device to extract heat for heating a pre-existing hot water tank of said building.
10. A heating system as claimed iii any preceding claim wherein said ducts comprise air ducts and wherein said air ducts have a cross-sectional area of less than 500 cm2.
11. A method of heating a house, the house comprising a heating system configured to enable heat from a heat source to be directed selectively to rooms or zones of said house, the method comprising: sensing which of said rooms or zones of said house are occupied; controlling said heating system to reduce the temperature in an unoccupied said room or zone to below a target temperature for an occupied said room or zone; detecting when a said room or zone becomes occupied and, responsive to said detecting, controlling said heating system to rapidly reheat said re-occupied room or zone by selectively directing heat from said heat source and from one or more additional heat sources to said re-occupied room or zone.
12. A method as claimed in claim 11 wherein said heating system comprises a water-based heat distribution system for distributing heat from said heat source to said rooms or zones and an air-based heat distribution system for distributing heat from said one or more additional heat sources to said rooms or zones, and wherein said controlling to rapidly reheat said re-occupied room or zone comprises controlling both said water-based heat distribution system and said air-based heat distribution system to selectively direct heat to said re-occupied room or zone.
13. A method as claimed in claim 12 wherein said controlling of said air-based heat distribution system comprises controlling to selectively pass air extracted from one or more others of said rooms or zones past a heat exchanger to heat air for said re-occupied room or zone.
14. A method as claimed in claim 12 or 13 wherein said controlling to rapidly reheat said re-occupied room or zone comprises controlling a solar heating system to heat air in said air-based heat distribution system.
15. A method as claimed in claim 12, 13 or 14 wherein said controlling to rapidly reheat said re-occupied room or zone comprises controlling said air-based heat distribution system to direct heat from an uncontrolled heat source in one of said rooms or zones to said re- occupied room or zone.
16. A method as claimed in any one of claims 11 to 15 wherein said controlling to rapidly reheat said re-occupied room or zone comprises controlling a heat pump to extract waste heat from said heating system for using said extracted heat to reheat said re-occupied room or zone.
17. A method as claimed in any one of claims 11 to 16 wherein said method further comprises learning a pattern of probability of occupation of a said room or zone and wherein said reduction in temperature of a said room or zone is dependent upon a probability of occupation of said room or zone.
1 8. A method as claimed in any one of claims 11 to 17 further comprising learning a transient response of said reheating of a said room or zone and wherein said reduction in temperature of a said room or zone is dependent upon said transient response of the room or zone.
19. A carrier canying processor control code to, when running, implement the method of any one of claims 11 to 18.
20. A heating system controller for controlling a heating system configured to enable heat from a heat source to be directed selectively to rooms or zones of a building, the controller comprising: means for sensing which of said rooms or zones of said house are occupied; means for controlling said heating system to reduce the temperature in an unoccupied said room or zone to below a target temperature for an occupied said room or zone; means for detecting when a said room or zone becomes occupied; and means for controlling said heating system responsive to said detecting to rapidly reheat said re-occupied room or zone by selectively directing heat from said heat source and from one or more additional heat sources to said re-occupied room or zone.
21. A controller for a heating system as claimed in any one of claims 1 to 10, the controller comprising: an input for a plurality of temperature sensors to sense temperatures in said rooms or zones; an input for a plurality of room or zone occupancy sensors to detect occupancy of said rooms or zones; an output for controlling said selective delivery by said outlet manifold; and a processor coupled to receive signals from said temperature and occupancy sensors and coupled to said output and configured to control said outlet manifold to selectively redistribute heat between said rooms or zones responsive to said sensed temperatures and occupancies.
22. A controller as claimed in claim 21 Further comprising a secure communications link for communicating with an electricity power supply company for reporting or negotiating an electrical power consumption of said heating system to or with said power supply company.
23. A home heating controller for controlling a domestic heating system, in particular as claimed in any one of claims ito 10, wherein the controller comprises a secure communications link for communicating with an electricity power supply company for negotiating an electrical power consumption of said heating system with said power supply company.
24. A roof tile incorporating a solar collector, and wherein said solar collector is configured to use air as a heat transfer working fluid.
25. A roof tile as claimed in claim 24 wherein said solar collector includes a heat exchanger which projects at the back of the tile, the tile having a border on at least upper and lower edges to allow said tiles to be fitted together one above another on a roof whilst leaving a gap of at least 2 cm for a roof truss between their respective heat exchangers.
26. A roofT tile as claimed in claim 24 or 25 wherein the tile tapers towards a top edge.