Patent Application
20150318815
The present invention relates to a combustion, heat-exchange and emitter device, a method for providing such and a thermophotovoltaic device comprising the same.
With the high demand of electricity and even more of clean, CO2 neutral energy sources, the efficiency with which the energy is harvested plays a more and more important role. As gradually many industrialized countries aim for shifting away from nuclear power production, the demand for alternative energy sources is greater than ever. However, so far few if any really viable alternatives are known. Many of the “classical” renewable energy sources such as wind-turbines or solar power plants have significant drawbacks preventing their wide-spreading.
Still, even if these drawbacks of “classical” renewable energy sources such as wind-turbines or solar power plants would be solved, there is still the major problem that quite often these sources of renewable energy are available at a very different locations than where the electrical energy is needed. The great distances between the generation location and the energy consumers require very complex, expensive and environmentally unfriendly infrastructure to transport the produced electrical energy. Furthermore, regardless of the improvements of such infrastructures in the latest period, there are still significant losses in the transport of electrical energy over long distances. Therefore there is an urgent need for decentralized energy production. In other words, the future of energy production lies in producing energy as close as possible to the consumer. This not only reduces/eliminates transmission losses but relives the electrical grid while ensuring much higher levels of flexibility.
One of the fields of great interest for decentralized energy production is the field of thermophotovoltaic devices, devices designed to transform chemical energy stored in a fuel into electro-magnetic radiation and then into electricity. However, the relatively reduced efficiency of the existing thermophotovoltaic devices has limited their use and mass-deployment.
As for efficiency, one of the most problematic aspect of these chemical-to-electric energy converters is the inefficiency of the conversion of chemical energy into electro-magnetic radiation. A critical component of the chemical-to-electric energy conversion is the combustion, heat-exchange and emitter device which transforms chemical energy into radiation. Combustion, heat exchange and emitter can be realised either separately or in one combined device, the latter having the advantage of reduced losses and compactness.
Various heat-exchange and emitter devices are known in the art aimed at improving their efficiency by loss heat recovery of the exhaust gases or by using emitters with high efficiency in the desired spectral band. However, known heat-exchange and emitter devices are complex and expensive to manufacture.
Irrespective of the type and construction of the thermophotovoltaic devices, an efficient heat transfer to the emitter and efficient transformation of this heat into electromagnetic radiation of optimal wavelength is desired.
The objective of the present invention is thus to provide a heat exchanger and emitter structure which enables a highly efficient transfer of heat and its transformation into electromagnetic radiation suitable for conversion into electrical energy. In addition to providing high efficiency, it is an objective of the present invention to simplify and thus reduce the manufacturing costs of such heat exchanger and emitters.
The above-identified objectives of the present invention are solved by a combustion, heat-exchange and emitter device for converting chemical into electro-magnetic radiation, the device comprising:
a radiation emitter section comprising a selective emitter configured for emitting predominantly near-infrared radiation when heated up to high temperatures;
a conversion section arranged adjacent to said radiation emitter section and comprising a catalytic coating in order to provide for surface specific fuel combustion to maximize heat transfer between a thermal energy carrier and the radiation emitter section;
a heat recovery section configured such as to transfer excess heat of the thermal energy carrier from an exhaust outlet section to an inlet section such as to pre-heat the thermal energy carrier (fuel) entering the device therethrough.
The above-identified objectives of the present invention are further solved by a method for producing a combustion, heat-exchange and emitter device in a layered fashion, the method comprising the steps:
providing an emitter layer having an outer surface facing away from the combustion, heat-exchange and emitter device and an inner surface;
at least partially coating said inner surface of the emitter layer with e.g. a catalytic coating in order to provide for surface specific fuel combustion;
providing said emitter layer with a selective emitter configured for emitting predominantly near-infrared radiation in the direction of said outer surface when it is heated up to high temperatures via said inner surface;
providing a pre-heat layer;
joining said emitter layer with the pre-heat layer such as to define a combustion chamber adjacent to the inner surface of the emitter layer;
providing a heat conduction layer with a heat dissipating surface and a heat absorbing surface;
joining the pre-heat layer and the heat conduction layer, such as to define a pre-heat chamber in-between and thermally connect the pre-heat chamber to said heat dissipating surface;
providing a first flow-through passage connecting the pre-heat chamber with the combustion chamber;
providing a heat conduction inhibition layer;
joining said heat conduction inhibition layer with the heat conduction layer such as to define a heat recovery chamber adjacent to said heat absorbing surface; and
providing a second flow-through passage connecting the combustion chamber and the heat recovery chamber,
the heat recovery chamber and the pre-heat chamber being arranged and configured such that heat absorbed by the heat absorbing surface is dissipated by the heat dissipating surface such as to pre-heat a thermal energy carrier within the pre-heat chamber.
The separation of the particular functions of a combustion, heat-exchange and emitter into well-defined sections allows each section to be fully optimised for the specific function. Thus the radiation emitter section is produced such as to provide optimum emission in the desired spectral band; the conversion section is optimised to provide for surface specific fuel combustion to maximize heat transfer between a thermal energy carrier (fuel) and the radiation emitter section; whereas the heat recovery section is optimised for maximizing heat recovery from the exhaust gases. Separating the functions into well-defined sections also allows each section to be produced of materials with properties suitable for the specific function.
Furthermore, the separation of the sections allows each section to be produced to an appropriate standard, enabling a particularly cost-effective production of the combustion, heat-exchange and emitter device by providing the option to produce the most technologically demanding and thus costly section (i.e. radiation emitter section comprising a selective emitter) separately from the other sections.
A particularly preferred method of producing the heat-exchange and emitter device of the present invention in a layered manner allows the emitter layer being produced and coated with a catalytic coating separately from the other layers. As the manufacturing requirements for the emitter layer and coating are much stricter, the process is much more elaborate and the technology much more expensive, by producing all other layers separately (in less demanding and thus less expensive production environments) provides for an essentially improved cost-effectiveness. Separating the production of “high-precision/high-tech” components also allows for an increase in productivity as not all components must be produced according to the same strict standards.
The combustion, heat-exchange and emitter device of the present invention finds particularly advantageous applicability for example in:
Further characteristics and advantages of the invention will in the following be described in detail by means of the description and by making reference to the drawings. Which show:
Note: The figures are not drawn to scale, are provided as illustration only and serve only for better understanding but not for defining the scope of the invention. No limitations of any features of the invention should be implied form these figures.
Certain terms will be used in this patent application, the formulation of which should not be interpreted to be limited by the specific term chosen, but as to relate to the general concept behind the specific term.
The combustion, heat-exchange and emitter device 10 comprises a radiation emitter section A configured for transforming heat from combustion into predominantly near-infrared radiation.
As shown on
In the most preferred embodiments of the combustion, heat-exchange and emitter device 10 according to the present invention, the selective emitter 1.3 comprises a selectively emitting material such as a rare-earth containing layer, preferably an Ytterbium-oxide Yb2O3 or a Platinum emitter layer. Alternatively or in addition, the selective emitter 1.3 comprises a selectively emitting nanostructured layer, such as a photonic crystal comprising temperature-resistant metal or ceramic.
In an even further embodiment, the selective emitter 1.3 comprises an inventive photonic crystal made of a selective emitter material such as e.g. Ytterbium-oxide Yb2O3.
In addition to a selective emitter 1.3, the radiation emitter section A may comprise a spectral shaper, which supports the functions of the selective emitter 1.4 and is:
configured as a band pass filter for a first, optimal spectral band of the radiation emitted by the selective emitter 1.3 when exposed to high temperature; and
configured as a reflector for further, non-optimal spectral band(s) of the radiation emitted by the selective emitter 1.3, so that said second, non-optimal spectral band radiation is recycled as radiation redirected towards the selective emitter 1.3 and/or the conversion section 1.2.
The combustion, heat-exchange and emitter device 10 further comprises a conversion section B arranged adjacent to the radiation emitter section A. The conversion section B comprises e.g. a catalytic coating in order to provide for surface specific fuel combustion to maximize heat transfer between a thermal energy carrier (fuel) and the radiation emitter section A in order to heat up the selective emitter 1.3 to high temperatures. The conversion section B either comprises a material which provides sufficient stability and/or it comprises a substrate made of a high temperature resistant material, preferably a ceramic material coated by a material supporting surface specific fuel combustion processes. The thermal energy carrier (fuel) enters the combustion, heat-exchange and emitter device 10 through an inlet section E connected with the radiation emitter section A.
The fuel is a chemical energy source, wherein the chemical energy carrier is preferably a fossil fuel such as methanol or hydrogen.
As shown on
The selective emitter 1.3 is preferably configured and arranged with respect to the combustion chamber 9 such as to provide an essentially constant radiation over its entire outer surface 1.1 when it is heated up to high temperatures. This ensures an optimal use of the radiation and enables the use of the combustion, heat-exchange and emitter device 10 in a thermophotovoltaic device in a particularly efficient manner enabling homogeneous radiation of the entire surface of a photovoltaic cell.
The third main function of the combustion, heat-exchange and emitter device 10 is provided for by means of a heat recovery section F configured such as to transfer excess heat of the thermal energy carrier from an exhaust outlet section G (after exiting the conversion section B) to the inlet section E such as to pre-heat the thermal energy carrier (fuel) entering the device 10 therethrough. This way the efficiency of the combustion, heat-exchange and emitter device 10 is greatly improved as heat losses are minimised and also the surface specific combustion in the combustion chamber 9 is improved as the fuel is pre-heated in the inlet section E before it enters the conversion section B.
In order to minimise heat loss outwards the device 10, a heat conduction inhibition section C is provided adjacent to the exhaust outlet section G of the device 10. The heat conduction inhibition section C adjacent the exhaust outlet G allows that a higher proportion of the excess heat of the thermal energy carrier is efficiently used to pre-heat the intake fuel in the inlet section E.
In addition, to prevent heat in the conversion section B to be also transferred to the inlet section E (which would lower the temperature and thus efficiency in the combustion chamber 9), a further heat conduction inhibition section C may be provided between said inlet section E and said conversion section B. This further heat conduction inhibition section C between said inlet section E and said conversion section B preferably comprises heat reflector layers, configured to reflect heat within the conversion section B resp. within the inlet section E. By using reflecting layers in the further heat conduction inhibition section C, energy loss is greatly minimized and unnecessary heating up of the device 10 is prevented as compared to using heat absorbent material.
For conducting excess heat of the thermal energy carrier from the exhaust outlet section G to the inlet section E, a heat conducting section D is provided within the heat recovery section F, between the exhaust outlet section G and the inlet section E.
In the following, the advantages of the present invention resulting from separation of the combustion, heat-exchange and emitter functions shall be described referring to a particularly preferred layered construction of the combustion, heat-exchange and emitter device 10 as shown in
Within the radiation emission section A, an emitter layer 1 having an outer surface 1.1 facing away from the device 10 is provided. The outer surface 1.1 at least partially defines the radiation emission section A whereas its inner surface 1.2 at least partially defines the conversion section B.
Within the conversion section B, a combustion chamber 9 is defined adjacent the inner surface 1.2 of the emitter layer 1.
A heat conduction layer 5 is provided with a heat dissipating surface 5.1 arranged towards said inlet section E and a heat absorbing surface 5.2 arranged towards said exhaust outlet section G, the heat conduction layer 5 at least partially defining the heat recovery section F.
The layered construction of the combustion, heat-exchange and emitter device 10 further comprises a heat conduction inhibition layer 6 adjacent to said exhaust outlet section G arranged to minimise heat loss outwards the device 10.
For providing a space for pre-heating the fuel entering the combustion, heat-exchange and emitter device 10, a pre-heat chamber 15 is defined within the inlet section E of the heat recovery section F, the pre-heat chamber 15 being thermally connected to said heat dissipating surface 5.1.
The pre-heat chamber 15 is connected to the combustion chamber 9 by a first flow-through passage 13.1.
For providing space for the exhaust fuel to transfer its excess heat to the heat absorbing surface 5.2, a heat recovery chamber 11 is defined between the said heat absorbing surface 5.2 and the heat conduction inhibition layer 6 within the exhaust outlet section G of the heat recovery section F.
The combustion chamber 9 is connected with the heat recovery chamber 11 by means of a second flow-through passage 13.2.
As illustratively shown on
A further heat conduction inhibition layer 3 may be provided between the emitter layer 1 and the heat conduction layer 5, the further heat conduction inhibition layer 3 separating the pre-heat chamber 15 from the combustion chamber 9 to prevent heat in the conversion section B to be also transferred to the inlet section E (which would lower the temperature and thus efficiency in the combustion chamber 9). The further heat conduction inhibition layer 3 also at least partially defines the second flow-through passage 13.2 respectively first flow-through passage 13.1.
For at least partially defining the pre-heat chamber 15 and the second flow-through passage 13.2, a pre-heat layer 4 is provided between the emitter layer 1 and the heat conduction layer 5 whereas an output layer 6 is provided between the heat conduction layer 5 and the heat conduction inhibition layer 7 for at least partially defining the heat recovery chamber 11.
As well shown on
Optionally, for reducing heat-loss, the combustion, heat-exchange and emitter device 10 (except for the outer surface 1.1 of the radiation emission section A) may be provided with an insulation layer.
providing an emitter layer 1 having an outer surface 1.1 facing away from the combustion, heat-exchange and emitter device 10 and an inner surface 1.2;
at least partially coating said inner surface 1.2 of the emitter layer 1 with a catalytic coating in order to provide for surface specific fuel combustion;
providing said emitter layer 1 with a selective emitter 1.3 configured for emitting predominantly near-infrared radiation in the direction of said outer surface 1.1 when it is heated up to high temperatures via said inner surface 1.2;
providing a pre-heat layer 4;
joining said emitter layer 1 with the pre-heat layer 4 such as to define a combustion chamber 9 adjacent to the inner surface 1.2 of the emitter layer 1;
providing a heat conduction layer 5 with a heat dissipating surface 5.1 and a heat absorbing surface 5.2;
joining the pre-heat layer 4 and the heat conduction layer 5, such as to define a pre-heat chamber 15 in-between and thermally connect the pre-heat chamber 15 to said heat dissipating surface 5.1;
providing a first flow-through passage 13.1 connecting the pre-heat chamber 15 with the combustion chamber 9;
providing a heat conduction inhibition layer 7;
joining said heat conduction inhibition layer 7 with the heat conduction layer 5 such as to define a heat recovery chamber 11 adjacent to said a heat absorbing surface 5.2; and
providing a second flow-through passage 13.2 connecting the combustion chamber 9 and the heat recovery chamber 11,
The finished construction of the combustion, heat-exchange and emitter device 10 as shown on
In order to produce the particularly preferred embodiment of the combustion, heat-exchange and emitter device 10 of the present invention as depicted on
providing a combustion layer 2 between the emitter layer 1 and the heat conduction layer 5, configured and arranged to at least partially define said combustion chamber 9;
providing a further heat conduction inhibition layer 3 between the emitter layer 1 and the heat conduction layer 5, the further heat conduction inhibition layer 3 separating said pre-heat chamber 15 from the combustion chamber 9; arranged and configured to at least partially define said second flow-through passage 13.2 and at least partially define said first flow-through passage 13.1; and
providing an output layer 6 between the heat conduction layer 5 and the heat conduction inhibition layer 7, arranged and configured such as to at least partially define the heat recovery chamber 11.
The method for producing the combustion, heat-exchange and emitter device 10 configures and arranges the layers as shown on
It will be understood that many variations could be adopted based on the specific structure hereinbefore described without departing from the scope of the invention as defined in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 12195732.8 | Dec 2012 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2013/075717 | 12/5/2013 | WO | 00 |
