Showing papers on "Photovoltaic thermal hybrid solar collector published in 2004"

PV Thermal systems: PV panels supplying renewable electricity and heat

Abstract: With PV Thermal panels sunlight is converted into electricity and heat simultaneously. Per unit area the total efficiency of a PVT panel is higher than the sum of the efficiencies of separate PV panels and solar thermal collectors. During the last 20 years research into PVT techniques and concepts has been widespread, but rather scattered. This reflects the number of possible PVT concepts and the accompanying research and development problems, for which it is the general goal to optimise both electrical and thermal efficiency of a device simultaneously. The aspects that can be optimised are, amongst others, the spectral characteristics of the PV cell, its solar absorption and the internal heat transfer between cells and heat-collecting system. Another important level of optimisation is for the PVT device geometry and the integration into a system. The electricity and heat demand and the temperature level of the heat determine the choice for a certain system set-up. With an optimal design, PVT systems can supply buildings with 100% renewable electricity and heat in a more cost-effective manner than separate PV and solar thermal systems and thus contribute to the long-term international targets on implementation of renewable energy in the built environment.

Microprocessor-controlled new class of optimal battery chargers for photovoltaic applications

Abstract: A simple, fast and reliable technique for charging batteries by solar arrays is proposed. The operating point of a battery is carefully forced near the maximum power point of solar cells under all environmental (e.g., insolation, temperature, degradation) conditions. Optimal operation of solar arrays is achieved using the Voltage-Based Maximum Power Point Tracking (VMPPT) technique and the charger operating point is continuously adjusted by changing the charging current. An optimal solar battery charger is designed, simulated and constructed. Experimental and theoretical results are presented and analyzed. The main advantages of the proposed solar battery charger as compared with conventional ones are shorter charge time and lower cost.

Solar power generation apparatus, solar power generation system, and method of manufacturing solar power generation apparatus

Abstract: A solar cell assembly including a plurality of solar cells is formed on a common substrate, and a DC/DC converter which converts the output from the solar cell is connected to each solar cell to constitute a solar power generation apparatus. The output from the solar power generation apparatus is converted into an AC power by an inverter and supplied to a load or commercial AC power system. Since the arrangement is simplified, the manufacturing cost can be reduced, and the influence of partial shade or a variation in characteristic decreases.

Toward ultrahigh-flux photovoltaic concentration

Abstract: We report experimental results with a miniature fiber-optic photovoltaic concentrator with (a) deliverable power density up to 104 suns (10 W/mm2), (b) solar cell efficiencies above 30%, (c) completely passive cooling, (d) uniform and individualized cell illumination, and (e) assembly from readily available components. Measurements include the sensitivity of the conversion efficiency of tandem III–V cells to (1) power input, (2) flux distribution, and (3) the modified spectrum from the fiber-optic concentrators. Our results augur favorably for the feasibility of such designs at concentration levels as high as thousands of suns.

Concentrating solar roofing shingle

Abstract: This invention describes a non-imaging, non-tracking, integrally-formed solar radiation concentrator that passively concentrates both diffuse and direct solar radiation onto photovoltaic cells to produce electricity, incorporating its features into a shingle-like element useful as a roofing material and in other structural applications. The substantially transparent, solar concentrating elements of the invention may also incorporate a system to remove waste energy in the form of heat that is not utilized in the generation of electricity. The invention further provides a thermal energy recovery system including a forced convection air system for removing waste heat from the concentrating shingle assembly and using it, if desired, for building space heat or domestic water heating.

Solar photovoltaics: Trends and prospects

Abstract: Key areas in the development of photovoltaic methods of solar energy conversion, which open up wide prospects for semiconductor solar energy conversion, are discussed The article focuses mainly on photovoltaic cells based on III-V heterostructures, primarily on cascade solar cells, which provide the highest efficiency of solar energy conversion and are produced by high-tech methods such as MBE or MOCVD It is shown that the use of intermediate sunlight concentration makes the area of solar cells smaller and, hence, lowers their cost proportionally to the sunlight concentration ratio

Experimental investigation of thermal performance of a solar assisted heat pump system with an energy storage

Abstract: An experimental solar assisted heat pump space heating system with a daily energy storage tank is designed and constructed, and its thermal performance is investigated. The heating system basically consists of flat plate solar collectors, a heat pump, a cylindrical storage tank, measuring units, and a heating room located in Gaziantep, Turkey (37.1°N). All measurements are automatically collected as a function of time by means of a measurement chain feeding to a data logger in combination with a PC. Hourly and daily variations of solar radiation, collector performance, coefficient of performance of the heat pump (COPHP), and that of the overall system (COPS) are calculated to evaluate the system performance. The effects of climatic conditions and certain operating parameters on the system performance parameters are investigated. COPHP is about 2.5 for a lower storage temperature at the end of a cloudy day and it is about 3.5 for a higher storage temperature at the end of a sunny day, and it fluctuates between these values in other times. Also, COPS turns out to be about 15–20% lower than COPHP. Copyright © 2004 John Wiley & Sons, Ltd.

System and method for thermal to electric conversion

Abstract: A system and method for lower cost, solar thermal generation includes a thermal input block, and an energy storage block.

Solar blackbody waveguide for efficient and effective conversion of solar flux to heat energy

Abstract: A solar blackbody waveguide that captures and uses sunlight to heat a thermal working or heat transfer fluid. Solar cell arrays capture the sunlight. The arrays are movably mounted on solar towers to track the daily movement of the sun and to maintain the proper angle with the horizon throughout the year. The arrays direct the light into a series of light pipes to deliver the light into a solar coil located within an underground insulated pipeline. Energy from the light rays is absorbed by the solar coil and transferred to the thermal working fluid or heat transfer fluid flowing between the solar coil and the insulated pipeline. The energy laden thermal working or heat transfer fluid is removed from the downstream end of the insulated pipeline so that it can be used with existing technologies, such as with a combined cycle gas turbine, boiler, or steam generator.

Optical Efficiency of Low-Concentrating Solar Energy Systems with Parabolic Reflectors

Abstract: Solar electricity is a promising energy technology for the future, and by using reflectors for concentrating solar radiation onto photovoltaic cells, the cost per produced kWh can be significantly ...

Improvement the thermal electric performance of a photovoltaic cells by cooling and concentration techniques

Abstract: A photovoltaic (PV) cell converts part of the solar energy impinging on it into electrical energy. The remaining part is converted into heat. This heat inversely affects the efficiency of the solar cell. The effect of the cell temperature on the performance of a PV cell is investigated. The effect on the performance of PV cells of concentrator direction and maximum number of reflectors is also presented. Two PV cell cooling methods are used, direct water-cooling and cooling using a heat pipe technique. It is found that the terminal voltage of the PV cell decreases as the temperature of the cell increases. Using parabolic concentrating collectors (dish) in order to maximize cell output minimizes cell area. PV cells have high output power at lower operating temperatures. The heat pipe cooling technique is the better cooling method. The average cell operating temperature is necessarily rather low in order to maintain a reasonable conversion efficiency.

Power generation by solar/pneumatic cogeneration in a large, natural or man-made, open pit

Abstract: This patent describes a method for power generation combining a solar concentrator and a pneumatic power tube system. Solar energy is concentrated to solar thermal receivers by a plurality of heliostat mirrors placed along the embankment of an open pit mine. The air in the pneumatic tubes is heated by direct and/or waste heat energy recovered from a solar power system and/or from a variety of sources. The invention is novel in its integration of a solar powered heat engine and a modular design, pneumatic power tube wherein a means of structural support for the tube(s) can be provided by the geophysical surroundings. The novel design features of the power tube pit include: its use of state-of-the art wind turbine power recovery, solar reflective surfaces for solar energy collection, heat pipe arrays for ground source heat recovery and air diffuser subsystems for enhanced wind turbine efficiency.

A solar concentrating photovoltaic/thermal collector

Abstract: This thesis discusses aspects of a novel solar concentrating photovoltaic / thermal (PV/T) collector that has been designed to produce both electricity and hot water. The motivation for the development of the Combined Heat and Power Solar (CHAPS) collector is twofold: in the short term, to produce photovoltaic power and solar hot water at a cost which is competitive with other renewable energy technologies, and in the longer term, at a cost which is lower than possible with current technologies. To the author’s knowledge, the CHAPS collector is the first PV/T system using a reflective linear concentrator with a concentration ratio in the range 20-40x. The work contained in this thesis is a thorough study of all facets of the CHAPS collector, through a combination of theoretical and experimental investigation. ...

Development of “Low-tech” Solar Thermal Water Pumps for Use in Developing Countries

Abstract: Solar water pumps, based on electro-mechanical pumps powered by PV arrays, are commonly used and commercially available. However, one of the difficulties for their wider application in developing countries, where there is a high average insolation, is their relatively excessive cost. This arises mainly due to the high cost of the PV elements. Hence, this paper describes some developmental work and results of experimental tests on "low-tech" solar thermal water pumps which were built on the basis of Stirling engines with fluid pistons coupled to flat-plate solar collectors. Temperatures and pressures in the cycle are comparatively low, thus cheap design materials, such as glass and plastic, and a simple technology, available in the majority of mechanical workshops, can be used for their manufacture and consequently reduce their cost. Several design modifications of the above solar thermal water pumps have been developed and tested. The results obtained demonstrate that existing installations can be effectively applied for water pumping with a dynamic head which varies between 2-5 m. Furthermore, data from experimental tests shows that the pulsating motion of water in channels of the flat-plate solar collectors increases the collector's efficiency by approximately 8-10%, which is a considerable advantage when a pump is used as part of a house solar heating system.

Solar thermal aircraft

Abstract: A solar thermal powered aircraft powered by heat energy from the sun. A heat engine, such as a Stirling engine, is carried by the aircraft body for producing power for a propulsion mechanism, such as a propeller. The heat engine has a thermal battery in thermal contact with it so that heat is supplied from the thermal battery. A solar concentrator, such as reflective parabolic trough, is movably connected to an optically transparent section of the aircraft body for receiving and concentrating solar energy from within the aircraft. Concentrated solar energy is collected by a heat collection and transport conduit, and heat transported to the thermal battery. A solar tracker includes a heliostat for determining optimal alignment with the sun, and a drive motor actuating the solar concentrator into optimal alignment with the sun based on a determination by the heliostat.

Shadow variation on photovoltaic collectors in a solar field

Abstract: Stationary solar collectors deployed in rows in a solar field may be subjected to shading by adjacent rows during the day The amount of shading depends on the distance between the collector rows and the shading may be taken into account in an optimal solar field design The variation of the shadow on the photovoltaic (PV) collector is investigated to assess the energy output from the solar field The shadow analysis provides the solar field designer with information on interconnecting schemes of the photovoltaic modules to form the photovoltaic array

Optimization of the solar energy collection in tracking and non-tracking photovoltaic solar system

Abstract: Experimental and theoretical analysis is made of the conditions of collection of solar radiation in solar tracking system without concentration, and in non-tracking system with standard and bifacial photovoltaic solar panel. For the experiments with solar tracking, an original Sun tracker was developed. The tracking effect calculated and measured shows an increase in energy collection around 30 - 40 %; bifacial panels with a reflector collecting solar radiation for the rear face give the corresponding increase of 50 - 60 % for the same panel area.