摘要:

Even though TPV energy converters may have weight, size, and cost advantages over other direct energy conversion techniques, TPV shares a low conversion efficiency with its direct energy conversion counterparts. Consequently, the virtues of TPV may be confined to low power applications where fuel costs are not significant. A number of commercial organizations are developing portable power systems embracing the full breath of TPV options. Fuels, which govern many system characteristics, range from methane to diesel fuel. Photoconverters are narrow band GaSb or InGaAs to wide band Si. Emitters are either broadband black body types, selective, or matched. Filters, particularly resonant filters, play a role in spectrum control. Optical and thermal recuperation are important. Fuel delivery, combustion control, ignition means, and thermal management impact overall performance. The design details of a recently developed TPV system will be covered. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539359

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

In this paper we report on the development and characterisation of a small TPV prototype system, which uses silicon photocells and a rare earth selective emitter. A simulation model of this system was developed, which allows studying the system theoretically. The fabrication of the selective incandescent mantle emitter from Yb2O3and detailed measurements of its radiation power and emissivity are presented. The maximum emissivity was 0.85 at 1.27 eV. An emitter temperature of 1735 K was obtained for an approximately 75 cm2large emitter heated by a butane burner. A SnO2filter tube was developed. The photocell generator is composed of monocrystalline silicon solar cells and a water‐cooling circuit. The prototype system reached, without a selective filter and without preheating of the combustion air, a record electricity‐to‐gas power efficiency of 2.4 &percent;. We compare the experimentally achieved system efficiency with simulations using our model. The possibilities to further increase the system efficiency are discussed. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539360

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

A thermophotovoltaic (TPV) system was built using a 12 to 20 kWthmethane burner which should be integrated into a conventional residential heating system. The TPV system is cylindrical in shape and consists of a selective Yb2O3emitter, a quartz glass tube to prevent the exhaust gases from heating the cells and a 0.2 m2monocrystalline silicon solar cell module which is water cooled. The maximum system efficiency of 1.0 &percent; was obtained at a thermal input power of 12 kWth. The electrical power suffices to run a residential heating system in the full power range (12 to 20 kWth) independently of the grid. The end user costs of the TPV components ‐ emitter, glass tube, photocells and cell cooling circuit ‐ were estimated considering 4 different TPV scenarios. The existing technique was compared with an improved system currently under development, which consists of a flexible photocell module that can be glued into the boiler housing and with systems with improved system efficiency (1.5 to 5 &percent;) and geometry. Prices of the electricity from 2.5 to 22 EURcents/kWhel(excl. gas of about 3.5 EURcents/kWh), which corresponds to system costs of 340 to 3000 EUR/kWel,peak, were calculated. The price of electricity by TPV was compared with that of fuel cells and gas engines. While fuel cells are still expensive, gas engines have the disadvantage of maintenance, noise and bulkiness. TPV, in contrast, is a cost efficient alternative to produce heat and electricity, particularly in small peripheral units. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539361

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Major changes in the regulation of electric and natural gas industries during recent years have forced energy companies to explore opportunities in small‐size Combined Heat and Power systems. These differ fundamentally from the traditional model of central generation and delivery since small, modular electric generators can be located very close to end‐users inside a building or a single house within an industrial area, combined with the production of heat and cold. In particular, interest is growing in the new technologies for sub‐100kWe units, including systems based on thermophotovoltaic (TPV) technology. TPV generator tubes can be inserted into hot furnaces to generate electricity and low‐grade heat. In this generator tube, a water‐cooled GaSb photovoltaic converter array inside the tube faces outward toward an infrared emitter liner mounted on the inside surface of the closed‐end tube. Each tube can be sized to generate several kW and a given furnace can heat several tubes. We have conducted pilot experiments on key components in order to develop the concept just described. This includes a pilot scale array tested in an electrical furnace that heat a 3″ diameter alumina tube with an infrared emitting liner. Also, a silicon carbide tube with a water‐cooling system was tested in a ceramic fiber lined furnace equipped with a commercial 200 kW flameless regenerative burner, simulating a TPV generator tube in such a system. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539362

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Low bandgap TPV cells are preferred for electric power generation in TPV cogeneration systems. Recently, significant progress has been made in fabrication of low bandgap semiconductor TPV devices, such as InGaAsSb and InGaAs cells. However, it appears that only limited data are available in the literature with respect to the performance of these TPV cells in combustion‐driven TPV systems. In the research presented in this paper, power generation using recently‐developed InGaAsSb TPV cells has been investigated in a gas‐fired space heating appliance. The combustion performance of the gas burner associated with a broadband radiator was evaluated experimentally. The radiant power density and radiant efficiency of the gas‐heated radiator were determined at different degrees of exhaust heat recuperation. Heat recuperation is shown to have a certain effect on the combustion operation and radiant power output. The electric output characteristics of the InGaAsSb TPV devices were investigated under various combustion conditions. It was found that the cell short circuit density was greater than 1 A/cm2at a radiator temperature of 930°C when an optical filter was used. An electric power density of 0.54 W/cm2was produced at a radiator temperature of 1190°C. Furthermore, modeling calculations were carried out to reveal the influence of TPV cell bandgap and radiator temperature on power output and conversion efficiency. Finally, the design aspects of combustion‐driven TPV systems were analyzed, showing that development of a special combustion device with high conversion level of fuel chemical energy to useful radiant energy is required, to improve further the system efficiency. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539363

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Three new developments have now occurred, making economical TPV systems possible. The first development is the diffused junction GaSb cell that responds out to 1.8 microns producing over 1 W/cm2electric, given a blackbody IR emitter temperature of 1250 C. This high power density along with a simple diffused junction cell makes an array cost of $0.50 per Watt possible. The second development is new IR emitters and filters that put 75&percent; of the radiant energy in the cell convertible band. The third development is a set of commercially available ceramic radiant tube burners that operate at up to 1250 C. Herein, we present near term and longer term spectral control designs leading to a 1.5 kW TPV generator / furnace incorporating these new features. This TPV generator / furnace is designed to replace the residential furnace for combined heat and power for the home. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539364

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

In an earlier paper [1], we reported on a small grid‐connected thermophotovoltaic (TPV) system consisting of an ytterbia mantle emitter and silicon solar cells with 16 &percent; efficiency (under solar irradiance at Standard Test Conditions, STC). The emitter was heated up using a butane burner with a rated thermal power of 1.35 kW (referring to the lower heating value). This system produced an electrical output of 15 W, which corresponds to a thermal to electric (direct current) conversion efficiency of 1.1 &percent;. In the interim, further progress has been made, and significantly higher efficiencies have been achieved. The most important development steps are: 1) The infrared radiation‐absorbing water filter between emitter and silicon cells (to protect the cells against overheating and against contact with flue gasses) has been replaced by a suitable glass tube. By doing this, it has been possible to prevent losses of convertible radiation in water. 2) Cell cooling has been significantly improved, in order to reduce cell temperature, and therefore increase conversion efficiency. 3) The shape of the emitter has been changed from spherical to a quasi‐cylindrical geometry, in order to obtain a more homogeneous irradiation of the cells. 4) The metallic burner tube, on which the ytterbia emitter was fixed in the initial prototypes, has been replaced by a heat‐resistant metallic rod, carrying ceramic discs as emitter holders. This has prevented the oxidation and clogging of the perforated burner tube. 5) Larger reflectors have been used to reduce losses in useful infrared radiation. 6) Smaller cells have been used, to reduce electrical series resistance losses. Applying all these improvements to the basic 1.35 kW prototype, we attained a system efficiency of 1.5 &percent;. By using preheated air for combustion (at approximately 370 °C), 1.8 &percent; was achieved. In a subsequent step, a photocell generator was constructed, consisting of high‐efficiency silicon cells (21&percent; STC efficiency). In this generator, the spaces between the cells were minimized, in order to achieve as high an active cell area as possible, while simultaneously reducing radiation losses. This new system has produced an electrical output of 48 W, corresponding to a system efficiency of 2.4 &percent;. This is the highest‐ever‐reported value in a silicon‐cell‐based TPV system using ytterbia mantle emitters. An efficiency of 2.8 &percent; was achieved by using preheated air (at approximately 500 °C). An electronic control unit (fabricated of components with low power consumption, and including a battery store) was developed, in order to make the TPV system, described in [1] self‐powered. This unit controls the magnetic gas supply valve between gas supply cylinder and burner as well as the high‐voltage ignition electrodes. Both the control unit’s own power consumption and the battery‐charging power are supplied directly by the TPV generator. A small commercial inverter is used to transfer excess power to the 230 V grid. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539365

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Realistic modeling of a TPV system is a very demanding task. For a rough estimation of system limits many of assumptions simplify the complexity of a thermophotovoltaic converter. It’s obvious that real systems can not be described by this way. An alternative approach that can deal with all these complexities like arbitrary geometries, participating media, temperature distributions etc. is the Monte Carlo method (MCM). This statistical method simulates radiative energy transfer by tracking the histories of a number of photons beginning with the emission by a radiating surface and ending with absorption on a surface or in a medium. All interactions in this way are considered. The disadvantage of large computation time compared to other methods is not longer a weakness with the speed of todays computers. This article points out different ways for realistic TPV system simulation focusing on statistical methods. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539366

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

A test‐bed 500 watt diesel fueled thermophotovoltaic (TPV) portable power supply is described. The goal of the design is a compact, rugged field portable unit weighing less than 15 pounds without fuel. The conversion efficiency goal is set at 15&percent; fuel energy to electric energy delivered to an external load at 24 volts. A burner/recuperator system has been developed to meet the objectives of high combustion air preheat temperatures with a compact heat exchanger, low excess air operation, and high convective heat transfer rates to the silicon carbide emitter surface. The burner incorporates a air blast atomizer with 100&percent; of the combustion air passing through the nozzle. Designed firing rate of 2900 watts at 0.07 gallons of oil per hour. This incorporates a single air supply dc motor/fan set and avoids the need for a system air compressor. The recuperator consists of three annular, concentric laminar flow passages. Heat from the combustion of the diesel fuel is both radiantly and convectively coupled to the inside wall of a cylindrical silicon carbide emitter. The outer wall of the emitter then radiates blackbody energy at the design temperature of 1400°C. The cylindrical emitter is enclosed in a quartz envelope that separates it from the photovoltaic (PV) cells. Spectral control is accomplished by a resonant mesh IR band‐pass filter placed between the emitter and the PV array. The narrow band of energy transmitted by the filter is intercepted and converted to electricity by an array of GaSb PV cells. The array consists of 216 1‐cm × 1‐cm GaSb cells arranged into series and parallel arrays. An array of heat pipes couple the PV cell arrays to a heat exchanger which is cooled by forced air convection. A brief status of the key TPV technologies is presented followed by data characterizing the performance of the 500 watt TPV system. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539367

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This paper aims to provide an overview of heat recovery by thermophotovoltaics (TPV) from industrial high‐temperature processes and uses the glass industry in the UK as an example. The work is part of a study of potential industrial applications of TPV in the UK being carried out by the Northumbria Photovoltaics Applications Centre. The paper reviews the relevant facts about TPV technology and the glass industry and identifies locations of use for TPV. These are assessed in terms of glass sector, furnace type, process temperature, impact on the existing process, power scale and development effort of TPV. Knowledge of these factors should contribute to the design of an optimum TPV system. The paper estimates possible energy savings and reductions of CO2emissions using TPV in the glass industry. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539368

出版商:AIP    

年代:1903

数据来源: AIP