EP2406837A2

EP2406837A2 - Combustion system for generating heat and power

Info

Publication number: EP2406837A2
Application number: EP10713109A
Authority: EP
Inventors: Ali Asghar Enkeshafi
Original assignee: Alpcon AS
Current assignee: Alpcon AS
Priority date: 2009-03-11
Filing date: 2010-03-11
Publication date: 2012-01-18
Also published as: WO2010102634A8; WO2010102634A3; WO2010102634A2

Abstract

A combustion system for generating heat and power is presented. The combustion system comprises a combustion chamber having a combustion source 2, and a Thermo Electrical Unit having a high temperature region and a low temperature region. The Thermo Electrical Unit comprises a first heat element 12, 112 being arranged in the combustion chamber such that in use heat emitted from the combustion source 2 is absorbed by the heat element 12, 112 and transmitted to the high temperature region whereby power is generated by the Thermo Electrical Unit.

Description

Title of the invention

Combustion system for generating heat and power

Field of the invention The present invention relates to a combustion system for generating heat and power.

Background of the invention

In a combustion system, e.g. in a household, energy from the combustion is transported to a hot water system that supplies heat and hot water to the household. Despite this a lot of the energy from the combustion is wasted.

DE 4028375 discloses a method and system for converting heat into electrical energy. The system for carrying out the method is provided with a heat source and an energy converter in form of a Thermoelectric Generator (TEG). The heat system is designed for a catalytic combustion.

WO 96/36077 discloses a combustion system where thermophotovoltaic cells are positioned such that a fraction of infrared radiation emitted by the combustion is absorbed by the thermovoltaic cells.

Summary of the invention

The object of the present invention is to provide a combustion system that has a high energy efficiency and at the same time is able to operate at high temperatures.

This object is fulfilled by a combustion system for generating heat and power, comprising a combustion chamber having a combustion source, a Thermo Electrical Unit having a high temperature region and a low temperature region, characterized in that the Thermo Electrical Unit comprises a first heat element being arranged in the combustion chamber such that in use heat emitted from the combustion source is absorbed by the heat element and transmitted to the high temperature region whereby power is generated by the Thermo Electrical Unit.

This allows heat from the combustion to be absorbed indirectly by the Thermo Electrical Unit and thus prevent a direct heating of high temperature region of the Thermo Electrical Unit, and further part of the heat is absorbed by the heat element such that the temperature in high temperature region of the Thermo Electrical Unit will be lower than the temperature in the hottest part of the heat element. In this way it is higher combustion temperatures can be used compared to the catalytic combustion in DE 4028375 where the temperature of the

Thermoelectric Generator is controlled directly by the combustion parameters in order to avoid damage of the Thermoelectric Generator.

A Thermo Electrical Unit should be construed as a device adapted to convert a temperature difference between a high temperature region in the Thermo Electrical Unit and a low temperature region in the Thermo Electrical Unit into power.

Combustion source should be construed as a source that during combustion emits heat and radiation.

The Thermo electrical Unit may further comprise a first thermo electric element and a heat sink adapted to in use cool the low temperature region of the first thermo electric element. This provides for a higher temperature difference and thus a higher power output. Furthermore the heat sink sees to that the Thermo Electrical Unit is cooled thus preventing damage thereof and further allowing higher temperatures during combustion.

The Thermo electrical Unit may furthermore comprise a second thermo electric element and a second heat element adapted to in use absorb heat from the combustion chamber and to transmit the heat to a high temperature region of the second thermo electric element. This allows a more efficient use of the Thermo Electrical Unit. For example may the first thermo electric element and the second thermo electric element be arranged symmetrically around the heat sink, which pro- vides for a more compact design of the Thermo Electrical Unit, and or the first heat element and the second heat element may be arranged symmetrically around the heat sink. Preferably the first heat element and the second heat element abut in an acute angle. This provides a more narrow design of the Thermo Electrical Generator thereby allowing that more Thermo Electrical Units can be arranged in the combustion chamber.

The combustion system may further comprise a plurality of Thermo Electric units. This provides for more power to be produced. For example the plurality of Thermo Electric Units may be arranged in a circle in the combustion chamber. This allows more suitable and simple assembly form and easy mounting in a traditional tubular combustion chamber.

At least one first heat element may be positioned in a high temperature section in the combustion chamber that in use operates between 400⁰C and 550⁰C preferably around 500⁰C and or at least one first heat element is positioned in a medium temperature section in the combustion chamber that in use operates between 200⁰C and 350⁰C preferably around 300⁰C. This provides for a high temperature difference between the high temperature region and the low temperature region in the Thermo Electrical Unit thus providing for a higher power output. By positioning the first heat elements in various temperature sections in the combustion chamber heat from the combustion may be used more efficiently.

In an embodiment of the combustion system the system may further comprise a radiation converter operable to convert radiation into power, the radiation converter arranged in optical communication with the combustion source such that in use a part of the radiation emitted from the combustion source it converted into power. In this way more energy originating from the heat from the combustion may be used.

A radiation converter should be conceived as a device adapted to transform radiation into power, such a converter could e.g. be a photovoltaic cell, such as a solar cell. The radiation converter may e.g. be adapted to convert radiation varying from infrared light to visible light i.e. in the spectrum varying from 400 nm to 1000 nm, e.g. in the spectrum from 400 nm to 700 nm, or in the spectrum varying from 700 nm to 1000 nm. It is advantageous to use photovoltaic cells as they are widely spread in the market and thus it makes the manufacturing of the combustion system easier. In one embodiment the photovoltaic cell is adapted to absorb visible light. This requires a higher combustion temperature. For example may a heat sink be arranged on the opposite side of a radiation absorbing side of the photovoltaic cell. In use this cools down the photovoltaic cell thus preventing it from being damaged by the heat from the combustion. Furthermore a screen may be positioned between the radiation converter and the combustion source, such that in use part of the heat is absorbed by the screen. This provides that part of the heat is absorbed by the screen but at the same time it allows that part of the radiation is still transmitted to the radiation converter. Thus the combustion can be operated at higher temperatures without damaging the radiation converting means.

A screen should be conceived as an optical component adapted to allow part of the radiation emitted from a combustion source to be transmitted, the screen further being adapted to absorb heat.

In another embodiment of the combustion system a plurality of radiation converters are arranged around the combustion source. This allows that more power can be generated.

In still another embodiment of the invention the heat sinks are adapted to in use be cooled by cooling water. This is an effective way of leading heat away, and further the cooling water will be heated during use, and the heated cooling water may e.g. be used in a household in to warm up e.g. water in a hot water tank.

In yet another embodiment the combustion system further comprises a transformation unit adapted to convert power generated by the combustion system to be compatible with power delivered by a grid. This provides for the generated power to be delivered to e.g. a household.

A grid should be conceived as a power network which may support all or some of the following three distinct operations: power generation, power transmission and power distribution. For example the transformation unit may further be adapted to transmit power to the grid. This allows for more efficient use of the generated power. It is noted that the invention relates to all possible combination of features recited in the above.

In view of the above, another objective of the present invention is to provide a system comprising a device capable of converting heat into electricity. The purpose of said system is to generate electricity and distribute said electricity accordingly.

Yet another objective of the present invention is to provide an improved method for operating such a system comprising said device.

In view of at least these objects, the invention relatesto a system for generating and supplying power, said system being adapted to be connected to a first power source, said first power source being a power network, said system comprising at least one power generation device arranged to be, when in a mounted state, in thermal contact with a hot fluid supply line and a cold fluid supply line, said device being adapted to generate power when fluid is running through at least the hot fluid supply line, a second power source, said second power source being a power storage device, said power being generated by the power generation device, a controller configured to determine the source that supplies power as a function of the quantity of power stored in the power storage device. By providing said system it may be achieved that the power may at all times be supplied to e.g. a load. This power may originate from the power generation device, said device being in thermal contact with the fluid supply lines. In this way, the temperature gradient between the fluid supply lines may provide for power generation. Power generated in the said device may subsequently be stored in the power storage device and, later on, supplied to said load. As an alternative, necessary power may be supplied from the power network. In order to determine which power source should be used, a measurement of power level in the power storage device may be performed. This information may thereupon be used to enable the suitable power source to supply power. Advantageously, the system may supply power from the power source that is most appropriate. Said controller may determine that power supplied originates from the power storage device when the quantity of power stored in said device exceeds a predetermined value. In this way, whenever possible, the necessary power may be supplied from the power storage device. Since this power originally is a result of a thermal gradient between the fluid supply lines, i.e. heat conversion into electricity, it may as such offer a positive contribution in the efforts to convert a low quality energy form into a higher quality, and thus more usable, energy form. When the power storage device supplies power to the load there is no need for power network to supply power to said load. The power network may, in fact, be viewed as a back-up power source that should be used only when the quantity of power stored in said device drops below a predetermined value. As power available from the power network typically originates from fossil fuels, then a significant positive environmental effect may be achieved. Should the power network be required to supply power, then the changeover from the power storage device is seamless and instantaneous.

Said power generation device may be a thermoelectric generator. As an advantage, a simplified mounting of the device on the fluid supply lines may be achieved. Said system may comprise a device adapted to increase the power voltage supplied by said power generation device and arranged to supply power to said power storage device. To this purpose a DC-DC converter may be used. By using said DC-DC converter the power voltage may be stepped up to an appropriate value. By introducing said DC-DC converter it may be assured that a stable voltage is supplied to the power storage device, regardless of the value of the power voltage generated by said thermoelectric generator. This renders the overall system more stable.

Said system may comprise a power inverting device arranged to supply power. In this way, at least the value of the power may be suitably modified. Power may originate either from the power storage device or from the power network. Said power may, furthermore, be converted, i.e. its type may be changed, if necessary, and subsequently supplied to said load. This renders the overall system more versatile and usable in a wide range of applications. Said controller may control relay means, said relay means being arranged to be in an open state when power supplied originates from the power storage device. In this way, it may be achieved that power network is prevented from supplying power when the quantity of power stored in the power storage device exceeds a predetermined value. Thus, a simple and robust regulation of the origin of power supply may be obtained.

Said system may comprise at least one current direction control means. In this way, current flow may be restricted to one direction only. As an advantage, a simplified system regulation may be achieved. Furthermore, system components may be protected from damage in case of system failure.

According to a second aspect, the invention relates to a method for operating a system, said method comprising generating power by means of a thermoelectric generator, determining a source that supplies power as a function of the quantity of power stored in a power storage device, said source being chosen from a group comprising said power storage device and a power network and supplying said power.

The method allows, as has been discussed above in view of the system, that the power may at all times be supplied to e. g. a load. This power may originate from the thermoelectric generator, said device being in thermal contact with the fluid supply lines. In this way, the temperature gradient between the fluid supply lines may provide for power generation. Power generated in the said device may subsequently be stored in the power storage device and, later on, supplied to said load. As an alternative, necessary power may be supplied from the power network. In order to determine which power source should be used, a measurement of power level in the power storage device may be performed. This information may thereupon be used to enable the suitable power source to supply power to said load. Advantageously, the system may supply power from the power source that is most appropriate.

In one embodiment said method is comprising arranging relay means in such a way that said power storage device is enabled to supply power when the quantity of power stored in the device exceeds a predetermined value. As has been discussed above, in view of the system, by suitably arranging said relay means it may be achieved that power network is prevented from supplying power when the quantity of power stored in the power storage device exceeds a predetermined value. To this purpose relay means may be arranged to be in an open state. Thus, a simple and robust regulation of the origin of power supply may be obtained.

In this way, whenever possible, the necessary power may be supplied from the power storage device. As an advantage, power generated by the device that is adapted to generate power may be supplied. Since this power originally is a result of a thermal gradient between the fluid supply lines, i.e. heat conversion into electricity, it may as such offer a positive contribution in the efforts to convert a low quality energy form into a higher quality, and thus more usable, energy form. When the power storage device supplies power to the load there is no need for power network to supply power to said load. The power network may, in fact, be viewed as a back-up power source that should be used only when the quantity of power stored in said device drops below a predetermined value. As power available from the power network typically originates from fossil fuels, then a significant positive environmental effect may be achieved.

In a further embodiment, said method is comprising increasing the voltage of the generated power and supplying said power to the power storage device.

As has been discussed above, in view of the system, by using suitable means the power voltage may be stepped up to an appropriate value. Thus, it may be assured that a stable voltage is supplied to the device adapted to store power, regardless of the value of the power voltage generated by said thermoelectric generator. This renders the overall system more stable. In another embodiment said method is comprising adapting at least the value of said power prior to supplying it.

As has been discussed above, in view of the system, by adapting the power the value of the power may be suitably modified. The power may originate either from the device adapted for power storage or from the power network. Said power may, furthermore, be converted, i.e. its type may be changed, if necessary, and subsequently supplied to the load. This renders the overall system more versatile and usable in a wide range of applications.

Other objectives, features and advantages of the present invention will appear from the following detailed disclosure, from the attached claims as well as from the drawings.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [unit, device, component, means, step, etc]" are to be interpreted openly as referring to at least one instance of said unit, device, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

Brief description of the drawings

These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing an embodiment of the invention. Like numbers refer to like features throughout the drawings.

Fig. 1 is a cross section of a combustion system.

Fig. 2 is a bottom view A-A of the combustion system in Fig. 1.

Fig. 3 is an exploded view of a water cooled heat sink with two photovoltaic cells.

Fig. 4 is a cross section view of the thermoelectric units in section B-B and section C-C of the combustion system in Fig. 1.

Fig. 5 is an exploded view and a perspective view of a thermoelectric unit in the medium temperature section. Fig. 6 is an exploded view of a thermoelectric unit in the high temperature section.

Fig. 7 is the water management in connection with the combustion system when implemented in a household.

Fig. 8 is the electrical management for the power output of the combustion system when implemented in e.g. a household.

Fig. 9 shows schematically a system for generation and supply of power according to an embodiment of the present invention;

Fig. 10 illustrates diagrammatically a system for generation and supply of power according to an embodiment of the present invention;

Fig. 11 shows a thermoelectric generator that is mounted on fluid supply lines according to an embodiment of the present invention;

Fig. 12 shows a flow-chart of a method of operating a system for generation and supply of power according to one embodiment of the present invention :

Detailed description of preferred embodiments

Fig. 1 shows a combustion system according to an embodiment of the invention. Fuel is supplied by the fuel inlet 1 to a combustion source, such as an emitter 2 in form of a ceramic cylindrical emitter coated e.g. a Yb203. Preferably the fuel is a carbonaceous fuel, such like natural gas. The emitter 2 is positioned in a combustion chamber with a cylindrical shape. The emitter 2 is surrounded by a first screen 3 in form of a cylindrical glass screen and a second screen 4 also in form of a cylindrical glass screen. A number of photovoltaic cells 6 are arranged around the emitter 2 such that during combustion light is radiated by the emitter 2 through the screens 3 and 4 to the photovoltaic cells 6. The photovoltaic cells are cooled by heat sinks 5. The photovoltaic section of the combustion chamber is shown in greater details in Fig. 2. For example may combustion temperatures be between 1800-2000⁰C in the photovoltaic section, such that visible light is emitted by the emitter 2. The first screen 3 and the second screen 4 absorb part of the heat from the combustion such that the temperature on the photovoltaic cells 6 is around 90⁰C on the absorbing surface. The heat sinks 5 see to that the 5 warmed up photovoltaic cells 6 are cooled, in order to avoid damage of the photovoltaic cells 6.

Heat from the combustion flows downstream from the photovoltaic section to a high temperature section adapted to operate at temperatures between 400⁰C and 10 550⁰C preferably around 500⁰C. In the high temperature section heat is transported from the high temperature section to a number of high temperature thermo electric elements 107 via a number of high temperature heat elements 112.

15 From the high temperature section heat flows further downstream to a medium temperature section adapted to operate at temperatures between 200⁰C and 350⁰C preferably around 300⁰C. In the medium temperature section part of the heat is absorbed by a number of medium temperatures heat elements 12 and from there part of it is supplied to a number of medium temperature thermo

20 electric elements 7. The medium and high temperature section can be studied in greater details in Fig.4.

After the medium temperature section the heat flows further downstream to a heat exchanger 17, in the presently illustrated example an air-water heat 25 exchanger, and thereafter out via a heat outlet distribution cap 18.

Fig. 2 shows a bottom view of section A-A of the combustion section shown in Fig. 1. The emitter 2 is positioned in the centre and surrounded by a first screen 3 and a second screen 4 e.g. in form of cylindrical glass screens. Photovoltaic cells 6 are

30 arranged in optical communication around the emitter 2 such that in use radiation from the emitter is transmitted to the photovoltaic cells 6, which transform absorbed radiation to electrical energy. The photovoltaic cells 6 are in the presently illustrated case arranged in an octagonal around the emitter 2 but other arrangements that resemble a circle such as a hexagonal could be used. This has

35 the advantage that it allows a suitable and simple form which is easy to mount in a traditional tubular combustion chamber. The photovoltaic cells 6 are in used cooled by cooling water cooled heat sinks 5 that are connected by water connection tubes 20. When the system is in use a water inlet manifold 21 supplies cooling water to the water cooled heat sinks 5 and cooling water is transported away via a water outlet manifold 22. The arrows in the figure illustrate the flow direction of the cooling water when the combustion system is in use. The cooling water is supplied from a water inlet manifold 21 to two diagonal opposed first water connection tubes 20 and from there the cooling water is led in two directions and in each direction led through two water cooled heat sinks 5 via a second water connection tube 20 to third water connection tubes that are connected with a water outlet manifold 22. The water outlet manifold transports cooling water away from the system via two diagonal opposed third water connection tubes. The cooling water flow is dimensioned such that in use there is a uniform flow of cooling water in each of the water cooled heat sinks 5.

Fig. 3 shows an exploded view of a water cooled heat sink 5 with two photovoltaic cells 6 adapted to absorb radiation from the emitter.

Fig. 4 shows the cross section B-B in Fig. 1 of the medium temperature section and the cross section C-C in Fig. 1 of the high temperature section . For reasons of simplicity the figure will be explained for the cross section B-B. In the medium temperature section heat is transported from the medium temperature section to sixteen symmetrically circular arranged thermo electric units. Each of the thermo electric units has a water cooled heat sink 8 that is position between two thermo electric elements 7, 7'. The water cooled heat sinks 8 are supplied with cooling water from a manifold arranged around the circle of the thermo electric units (not shown in the figure). Each of the thermo electric elements 7, 7' adjoins on their opposite side a medium temperature heat element 12, 12'. The thermo electric units in cross section C-C are arranged in a similar manner.

Fig.5 shows an exploded view of a thermoelectric unit and a perspective view of a mounted thermoelectric unit. The thermo electric unit has a water cooled heat sink 8 with a rectangular cross-section that is symmetrical positioned between two thermo electric elements 7, 7' likewise with like rectangular cross-sections, such that in a mounted position the surface area of a low temperature region of the thermo electric element 7, 7' and the water cooled heat sink 8 overlap. The thermo electric elements adjoin on their opposite second side a medium temperature heat element 12. The medium temperature heat element 12 has a fist heat transmitting part with a surface area that in a mounted position overlaps and extends the surface of the high temperature region of the thermo electric elements 7. The medium temperature heat element 12 further has a second elongated, heat absorbing, part that is connected with the first heat transmitting part via an intermediate part. When the thermoelectric unit is mounted the second elongated, heat absorbing, parts meet in an acute angle. The medium temperature heat elements 12, 12' are adapted to absorb heat from the medium energy heat section and transport it to the high temperature region of the thermo electric element 7, 7' such that in use the high temperature region of the thermo electric element 7, 7' is heated, and the low temperature region of the thermo electric element 7, 7' is cooled by the water cooled heat sink 8, thereby creating a potential difference between the first and the second side of the thermo electric element 7,7'. In this way power is generated. The high and medium temperature heat elements 12, 12', 112, 112' are e.g. made of copper which is coated with a corrosion resistant material. The high and medium temperature heat elements 12, 12', 112, 112' are e.g. nickel plated or chromium plated. Each of the medium temperature heat elements 12, 12' is designed such that during use it has a surface temperature about 250⁰C on the heat transmitting part and such that the heat transport to the thermo electric element 7, 7' is equal to the heat transport to the heat sink 8. The surface area of the medium temperature heat elements 12, 12' is e.g. between 80-100 cm² such as around 90cm².

Fig. 6 shows an exploded view of a high temperature thermo electric unit adapted to be positioned in the high temperature section of the combustion chamber. A similar construction of the medium thermoelectric units is used in the construction of the high temperature thermoelectric units, though with the difference that the high temperature thermoelectric units are adapted to be used at high temperatures, e.g. the materialof a thermo electric element 107, 107' may be like the one described in EP 1 828 880. Furthermore the high temperature heat elements 112, 112' are adapted to transport larger amounts of heat. The high temperature heat elements 112, 112' have a larger surface area of the second elongated, heat absorbing, part than the medium temperature heat elements 12, 12'. Each of the high temperature heat elements 112, 112' is designed such that during use it has a surface temperature maximum of 400⁰C on the heat transmitting part that the heat transport to the thermo electric element 7, 7' is equal to the heat transport to the heat sink 8. The surface area of the high 5 temperature heat element 112, 112' is e.g. between 220cm² and 270 cm² such as 240cm².

Fig. 7 shows the water management system when the combustion system is implemented e.g. in a household. Cooling water is supplied to a water inlet

10 collector 26 distributing the cooling water to: the water inlet manifold 21 (not shown in the figure) in the photovoltaic section 9, the water cooled heat sinks 8, 108 ( not shown in the figure) in the high temperature section 15 and the medium temperature section 16, and to the air-water heat exchanger 17. After passage of the above mentioned elements the cooling water has been warmed up. The

15 warmed-up cooling water is led out from each of the elements to the water collector for outlet water 25. A thermo switch 27 can be adjusted to open when the cooling water has a certain temperature e.g. 85°C. The cooling water is then led through a pipeline system into a hot water tank 38 where heat from the pipeline is exchanged to the water in the hot water tank 38. In this way the

20 heated cooling water is cooled down and can re-enter into the combustion system. Thus the cooling water system forms a closelooped system. A pump 31 is used to regulate the cooling water flow by input from a thermo switch 29 that measures the temperature of the water in the hot water tank 38. When the temperature of the water in the hot water tank decreases to a certain adjustable temperature e.g.

25 50⁰C, the water pump 31 circulates the cooling water and when it exceeds the adjustable temperature it stops circulation of the cooling water. Consequently the water in the hot water tank 38 is warmed up and can be used for various purposes e.g. direct hot water supply 34 and to heat up a water in e.g. a radiator system 36, thus utilizing the heat from the combustion more effectively.

30

In an alternative embodiment of the invention the photovoltaic cells 6 and the Thermoelectric Units are cooled by a gas.

Fig. 8 shows the power management for the power output of the combustion 35 system. During use of the combustion system power is generated by the photovoltaic section 9, by the high temperature thermo electric units in the high temperature section 15 and by the medium temperature thermo electric units in the medium temperature section 16. The power generated by the photovoltaic cells is converted in a first converter 40 e.g. in form of a 100 Watt DC to DC converter, and the power generated by the high respectively medium temperature thermo electric units is converted in a second converter 41 e.g. in form of a 500 Watt DC to DC converter. The converted power of the first and second converter is send to a power bridge comprising a super capacitor 42 e.g. in form of a 24V Super Capacitor 42. From the super capacitor 42 the power is passed to an inverter 43 that transforms the power to comply with the power supplied by the grid 44. The power can thereby be delivered and consumed by e.g. a household 45 or it can be delivered to the grid 44. As an example it is ensured during the conversions that the voltage levels and the phases of the inverter 43 and the grid 44 are compatible so as to allow the inverter 43 to be coupled to the grid 44.

Fig. 9 shows schematically a system for generation and supply of power 2 according to an embodiment of the present invention.

A power generation device 4 is arranged to be in thermal contact with hot and cold fluid supply lines 5, 6. Typically, said fluid is water. In one embodiment said device is a suitably mounted thermoelectric generator 4. A thermal contact between the heat source, in this case hot water via the hot water supply line, and the thermoelectric generator 4 is ensured. The thermoelectric generator 4 is electrically connected with a battery 8 via a DCDC converter 10. Said battery 8 is, furthermore, electrically connected to a power network 12 via relay means situated in a casing 14. Moreover, said casing 14 contains a controller. The battery 8 supplies power to a power inverter 16. Likewise, the power network 12 is electrically connected to said power inverter 16. System components will be more thoroughly described below with reference tong 2.

The system may, as an alternative, operate without the said DC-DC converter 10. Consequently, this requires a very careful sizingof the thermoelectric generator 4 in order to at all times provide substantially the same power voltage to the battery 8. Said battery 8 may, when suitable, be replaced by another power storage device, such as super capacitor. The super capacitor is a type of capacitor with very high electrical energy storage capacity.

In certain embodiments, the relay means and the controller are integrated in one device. Such a device could be an over-under voltage relay. The heat required by the thermoelectric generator 4 to produce power may be provided by a steam or hot air supply line.

An evaporating liquid gas or liquid hydrogen may be used as a cold source.

According to one embodiment of the present invention, one section of the fluid supply lines 5,6 may be exchanged and the suitable piping setup comprising a thermoelectric generator 4 may be introduced. Said piping setup will be more thoroughly described below with reference to Fig. 11. By opening a hot water tap, the hot water starts flowing through a supply line 5. The temperature gradient to which the thermoelectric generator 4 is thereby exposed renders possible for power to be generated. As stated above, if the power supplied by the thermoelectric generator 4 has variable value, then the DC-DC converter 10 is used in order to ensure that the power supplied to the battery 8 at all times has substantially the same voltage. Power generated in the thermoelectric generator 4 is stored in the battery 8, with the purpose of supplying it to a load (not shown) when required. If the quantity of power stored in said battery 8 drops below a predetermined value, then a seamless and instantaneous power source changeover is made. Consequently, the power required by the load is then provided by the power network 12. Said changeover is controlled by a conveniently positioned controller and executed using relay means. Typically, said controller and relay means as well as ancillary equipment are situated in a suitable casing 14.

Prior to supplying power to said load, the value of the power might need to be suitably modified. Power may originate either from the battery 8 or from the power network 12. Said power may, furthermore, be converted, if necessary. The above actions may be carried out by means of the power inverter 16. On average, a person's daily consumption of hot water corresponds to about 3 kWh. Using standard system components, in accordance with what has been described above, this gives rise to 135 Wh that are supplied to the battery 8. By way of example, the battery 8 may be adapted for 24 V OCcurrent. In the above cirumstances it takes approximately five days to fully charge the battery 8. Such a battery, when fully charged, typically has a capacity of around 720 W. Power generated in this way may be used for various applications. By way of example, it may be used to power light sources in a household.

By using the system described above the necessary power may, whenever possible, be supplied from the battery 8. Said power is, as it has been explained above, generated by the thermoelectric generator 4. Since this power originally is a result of the thermal gradient, i.e. heat has been converted into electricity, it may as such offer a positive contribution in the efforts to convert a low quality energy form into a higher quality, and thus more usable, energy form. The power network 12 may be viewed as a backup power source that should be used only when the quantity of power stored in the battery 8 drops below a predetermined value. As power available from the power network 12 typically originates from fossil fuels, then a significant positive environmental effect may be achieved. Should the power network 12 be required to supply power, then the changeover from the battery 8 is seamless and instantaneous. Consequently, a power loss may be avoided.

Fig. 10 illustrates diagrammatically a system for generation and supply of power 2 according to an embodiment of the present invention.

The system 2 generates power by means of a thermoelectric generator 4. The thermoelectric generator 4 is electrically connected with a battery 8 via a DC-DC converter 10 and a current direction control means 18. By way of example said control means may be a diode 18. Said battery 8 is, furthermore, electrically connected to a power network 12 via relay means 20. Operation of said relay means 20 is controlled by a controller 22. As stated above, with reference to Fig. 9, relay means 20 and the controller 22 are typically situtated in a common casing (not shown). The power network 12 as well as the battery 8 are electrically connected to a power inverter 16. Another diode 18 is arranged between the battery 8 and the power inverter 16. As explained above, the system with a reduced number of components may be envisaged.

The system 2 may, with regard to its components, be customized in many different ways, depending on load requirements. Consequently, power supplied to the load may have different voltage values and both AC-and DCcurrents are envisageable.

As stated above, with reference to Fig. 9, power is generated by a thermoelectric generator 4. Typically the thermoelectric generator 4 will generate power whose value will range between 5 and 20 V. This value will depend on the magnitude of the temperature difference. The power will subsequently be supplied to a DC/DC converter 10. In one embodiment, the DC/DC converter 10 converts this power to a steady voltage of 27 V and supplies it, via a diode 18, to a battery 8. The diode 18 prevents current from flowing in an undesired direction.

In order to determine which power source should be used, a measurement of power level in the battery 8 is continuosly performed. A controller 22 is configured to use the information obtained by said measurement and determine the source that supplies power. When the controller 22 has registered a prohibitively low voltage level of the battery 8, a signal is sent to the relay means 20. Consequently, said relay means 20 are set to a closed state, enabling thereby power supply from a power network 12. In this way, the power network 12 supplies a 230 V AC-current that may, in this embodiment, be modified to e.g 24 V, and supplied to a load. In order to prevent the battery 8 from being charged by the power network 12 the current direction control means 18 is adequately arranged. Analoguously, once the battery 8 has been fully charged a signal is sent by the controller 22. Relay means 20 are subsequently set to the open state and the electrical connection between power network 12 and the power inverter 16 is interrupted. A fully charged battery 8 is a prerequisite for relay means 20 to be switched. Henceforth, the battery 8 delivers the power.

The system 2 is capable of supplying power to a load simultaneously with loading the battery 8. By providing said system 2 it may be achieved that power may at all times be supplied to the load. This power may originate from the thermoelectric generator 4 and subsequently be stored in the battery 8. As an alternative, necessary power may be supplied from the power network 12. In order to determine which power source should be used, a measurement of power level in the battery 8 may be performed. This information may thereupon be used to enable the suitable power source to supply power to said load. In this way, the system may supply power from the power source that is most appropriate. The above-mentioned functionality is achieved using relay means 22. Thus, a simple and robust regulation of the origin of power supply may be obtained.

By using said DC-DC converter 10 the power voltage may be stepped up to an appropriate value. In this way, it may be assured that a steady voltage having a constant value is supplied to the battery 8 regardless of the value of the power voltage generated. This renders the overall system more stable.

By providing said current direction control means 18 the current flow may be restricted to one direction only. As an advantage, a simplified system regulation may be achieved. Furthermore, components may be protected from damage in case of system failure.

By providing said power inverter 16 the value of the power may be suitably modified. Said power may, furthermore, be converted, if necessary, and subsequently supplied to the load. This renders the overall system more versatile and usable in a wide range of applications.

Fig. 11 shows a thermoelectric generator 4 that is mounted on fluid supply lines 5, 6 according to an embodiment of the present invention. The flowing direction of the fluids are indicated by arrows.

According to the present embodiment, said thermoelectric generator 4 comprises a plurality of thermoelectric elements 24 that are, in this embodiment, arranged in pairs. Typically, said thermoelectric elements 24 are connected in series. Each element 24 is positioned in such a way that its two faces are in thermal contact with cold and hot water supply line 5, 6 respectively. As it may be seen, the cold water supply line 6 forks into two cold water supply conduits 25, 26. This arrangement provides for each thermoelectric element 24 to be sandwiched between the cold water supply conduit 25 and the hot water supply line 5. At least the surfaces that are in direct contact with the thermoelectric elements 24 are usually made in a material that promotes heat transfer and, accordingly, has large specific heat capacity, such as aluminium.

It is equal lyenvisageable for hot water supply line 5 to fork into two hot water supply conduits.

As an alternative, two fluid supply lines 5, 6 may be straight and thus non-forking. Thus, only individual thermoelectric elements 24 may be arranged between the two supply lines.

When, at least, hot water flows through the supply line 5 a thermal gradient between the two sides of the element 24 arises. Power is hereby generated. As explained above, said power is subsequently appropriately managed by the system 2. In the present embodiment, the thermoelectric generator 4 with the corresponding water supply lines 5, 6, as depicted in Fig. 11, are part of a dedicated kit that is to be retrofitted onto existing water pipes upon removing a section of said pipes. Obviously, said kit may be incorporated in new water supply line installations. Alternatively, the system may only comprise the thermoelectric generator that is to be arranged in direct thermal contact with the existing water pipes.

Refering to the above stated example of power generation and with reference to Fig. 9, the thermoelectric generator 4 should be able to produce approximately 55 W in order to provide the required 135 W of 24 V OCcurrent, given a normal hot water consumption pattern. Depending on the size of the particular thermoelectric element 24 the appropriate number of element pairs is needed in order to suitably size the thermoelectric generator 4. Even element pairs, or individual elements as described above, having different capacities may be used. The number and the capacity of the particular thermoelectric element 24, implicitly even the capacity of the thermoelectric generator, may be customized in order to satisfy load requirements as well as hot water consumption patterns. By generating power using the thermoelectric generator 4 arranged to be in 5 thermal contact with water supply lines 5, 6, the heat is converted into electricity. In this way a positive contribution is made in efforts to convert a low quality energy form into a higher quality, and thus more usable, energy form.

Fig. 12 shows a flow-chart of a method of operating a system for generation and 10 supply of power 2 according to one embodiment of the present invention. In step 400 the opening of a hot water tap causes power to be generated in a thermoelectrical generator 4. Subsequently, in step 410, this power is stepped up by a DC-DC converter 10, whereupon, in step 420, it is supplied to a battery 8. In step 430 the power voltage level of the battery 8 is measured. Step 430 is 15 performed on a continuous basis. Information gathered by said measurement is received as an input signal by a controller 22 in step 440. The purpose of said controller 22 is to control the operation of the system 2. Based on the information contained in this signal, the controller 22 determines, in step 450, which power source should supply power. A signal is sent from the controller 22 to relay means 20 20 in step 460, whereupon said relay means 20 are suitably arranged in step 470. Power is thereafter supplied, either by the battery 8, step 471, or by the power network 12, step 472.

As explained above with reference to Fig. 10, power supplied originates from the 25 battery 8 when the quantity of power stored in said battery 8 exceeds a predetermined value. It is desirable to supply power from the battery 8 whenever possible. Should the power network 12 be required to supply power, then the changeover from the battery 8 is seamless and instantaneous.

30 If battery 8 is fully charged, the load doesn't require power to be supplied and electricity may potentially be generated in the thermoelectrical generator 4, due to the hot fluid running through the supply line 5 then the thermoelectric generator 4 is typically set in a state where it doesn't generate any power. A person skilled in the art will readily recognize that not all steps described above may be necessary in order to successfully operate said system.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the number and Thermo Electrical Units and the number of photovoltaic cells may be varied.

The aspects of the invention disclosing the combustion system for generating heat and power as described and claimed may be combined with the aspects of the invention disclosing the system for generating and supplying power as described and claimed.

Claims

1. A combustion system for generating heat and power, comprising

- a combustion chamber having - a combustion source (2),

- a Thermo Electrical Unit having a high temperature region and a low temperature region, said Thermo Electrical Unit comprising a first heat element (12, 12' , 112, 112') being arranged in the combustion chamber such that in use heat emitted from the combustion source (2) is absorbed by the heat element (12, 12', 112, 112') and transmitted to the high temperature region whereby power is generated by the Thermo Electrical Unit, wherein at least one first heat element (12, 12' , 112, 112') is positioned in one of the following temperature sections: a high temperature section in the combustion chamber that in use operates between 400⁰C and 550⁰C, or a medium temperature section in the combustion chamber that in use operates between 200⁰C and 350⁰C, wherein the Thermo Electrical Unit further comprises thermo electric elements (7, T₁ 107, 107') and a heat sink (8, 108) adapted to in use cool the low temperature region of the thermo electric elements (7, 7', 107, 107'), characterized in that

- said high temperature region of the thermo electric elements 7, 7' is to be heated by the combustion zone (2), and

- said low temperature region of the thermo electric element 7, 7' is to be cooled by the water cooled heat sink 8,

- wherein the water cooled heat sink 8 is positioned between two thermo electric elements 7, 7',

- thereby creating a potential difference between the first and the second side of the thermo electric element 7,7'.

2. A combustion system according to claim 1, wherein the Thermo Electrical

Unit further comprises

- a first thermo electric element (7, T₁ 107, 107') and

- a heat sink (8, 108) adapted to in use cool the low temperature region of the first thermo electric element (7, 7', 107, 107').

3. A combustion system according to claim 2, wherein the Thermo electrical

Unit further comprises

- a second thermo electric element (7, T₁ 107, 107') and - a second heat element (12, 12', 112, 112') adapted to in use absorb heat from the combustion chamber and to transmit the heat to a high temperature region of the second thermo electric element (7, 7', 107, 107').

4. A combustion system according to claim 3, wherein the first thermo electric element (7, 107) and the second thermo electric element (7', 107') are arranged symmetrically around the heat sink (8, 108).

5. A combustion system according to any of the claims 3-4, wherein the first heat element (12, 112) and the second heat element (12', 112') are arranged symmetrically around the heat sink (8, 108).

6. A combustion system according to claim 5, wherein the first heat element (12, 112) and the second heat element (12', 112') abut in an acute angle.

7. A combustion system according to any of the preceding claims comprising a plurality of Thermo Electric units.

8. A combustion system according to claim 7 wherein the plurality of Thermo

Electric Units are arranged in a circle in the combustion chamber.

9. A combustion system according to any of the preceding claims, wherein at least one first heat element (12, 12' , 112, 112') is positioned in a high temperature section in the combustion chamber that in use operates between 400⁰C and 550⁰C.

10. A combustion system according to any of the preceding claims, wherein at least one first heat element (12, 12', 112, 112') is positioned in a medium temperature section in the combustion chamber that in use operates between 200⁰C and 350⁰C.

11. A combustion system according to any of the preceding claims, further comprising a radiation converter (6) operable to convert radiation into power, the radiation converter (6) arranged in optical communication with the combustion source (2) such that in use a part of the radiation emitted from the combustion source (2) it converted into power.

12. A combustion system according to claim 9, wherein the radiation converter

(6) comprises a photovoltaic cell (6).

13. A combustion system according to claim 12, wherein the photovoltaic cell (6) is adapted to absorb visible light.

14. A combustion system according to any of the claims 12-13, further comprising a heat sink (5) arranged on the opposite side of a radiation absorbing side of the photovoltaic cell (6). 5

15. A combustion system according to any of the claims 11-14, wherein a screen is positioned between the radiation converter and the combustion source (2), such that in use part of the heat is absorbed by the screen. 10

16. A combustion system according to any of the claims 11-15, wherein a plurality of radiation converters are arranged around the combustion source (2).

15 17. A combustion system according to claim 1-6 and claim 14, wherein the heat sinks (5, 8, 108) are adapted to in use be cooled by cooling water.

18. A combustion system according to any of the preceding claims, further 20 comprising a transformation unit (40, 41, 43) adapted to convert power generated by the system to be compatible with power delivered by a grid (44).

19. A combustion system according to claim 17, wherein the transformation 25 unit (40, 41, 43) further is adapted to transmit power to the grid

(44).

20. A system for generating and supplying power, said system being adapted to be connected to a first power source, said first power source 30 being a power network, said system comprising.

- at least one power generation device arranged to be, when in a mounted state, in thermal contact with a hot fluid supply line and a cold fluid supply line, said device being adapted to generate power based on a temperature gradient between the

35 hot fluid supply line and the cold fluid supply line when fluid is running through at least the hot fluid supply line,

- a second power source, said second power source being a power storage device, said power being generated by the power generation device,

40 - a controller configured to determine the source that supplies power as a function of the quantity of power stored in the power storage device.

21. A system according to claim 20, wherein said controller determines that 45 power supplied originates from the power storage device when the quantity of power stored in said device exceeds a predetermined value.

22. A system according to claim 20 or 21, wherein said power generation device is a thermoelectric generator.

23. A system according to any of the preceding claims, wherein said system further comprises a device adapted to increase the power voltage supplied by said power generation device and arranged to supply power to said power storage device.

24. A system according to any of the preceding claims, wherein said system further comprises a power inverting device arranged to supply power.

25. A system according to any of the preceding claims, wherein said controller controls relay means, said relay means being arranged to be in an open state when power supplied to said load originates from the power storage device.

26. A system according to any of the preceding claims, wherein said system further comprises at least one current direction control means.

27. A method comprising the steps of - generating power by means of a thermoelectric generator, determining a source that supplies power as a function of the quantity of power stored in a power storage device, said source being chosen from a group comprising said power storage device and a power network,and - supplying said power.

28. A method according to claim 27, said method further comprising the step of arranging relay means in such a way that said power storage device is enabled to supply power when the quantity of power stored in the device exceeds a predetermined value.

29. A method according to claims 27 or 28, said method further comprising the steps of

- increasing the voltage of the generated power, and - supplying said power to the power storage device.

30. A method according to any of the claims 27-29, said method further comprising the step of adapting at least the value of said power prior to supplying it.