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Photovoltaics - sustainable futures
RESEARCH TRENDS
Research Trends Photovoltaics ¯¯ sustainable futures As both population and energy use per capita increase, modern society is approaching physical limits to its continued fossil fuel consumption. The immediate limits are set by the planet's ability to adapt to a changing atmospheric chemical composition, not the availability of resources. In order for a future society to be sustainable while operating at or above our current standard of living a shift away from carbon based energy sources must occur. An overview of the current state of active solar (photovoltaic) energy technology is provided here to outline a partial solution for the environmental problems caused by accelerating global energy expenditure. The technical, social, and economic benefits and limitations of PV technologies to provide electricity in both off-grid and on-grid applications are critically analyzed in the context of this shift in energy sources. It is shown that PV electrical production is a technologically feasible, economically viable, environmentally benign, sustainable, and socially equitable solution to society's future energy requirements. Joshua M. Pearce: Futures 34 (7) 663-674 (September 2002).
A grid-connected Greek PV installation This paper describes the installation, technical characteristics, operation and economic evaluation of one of the largest grid-connected photovoltaic (PV) systems installed in Greece, and in particular, in the island of Paros in the Aegean Sea. Attention is drawn to the impact of PV utilisation on ecological tourism, which is growing very fast in Greece. Also, several issues are considered when assessing the value of PV electricity. The value of PV has been examined from various consumer, utility and environmental perspectives and for central and decentralised PV systems in conjunction with the benefits for all the involved parties, i.e. the owners, operators, users, tourists, investors, renewable system industry and local authorities. G.C. Bakos, M. Soursos: Energy and Buildings 34 (7) 753-758 (August 2002).
J-band of organic dyes: lineshape and coherence length Self-organised J-aggregates of dye molecules, known for over 60 years, are emerging as remarkably versatile quantum systems with applications in photography, optoelectronics, solar cells, photobiology and as supra-molecular
August 2002
fibres. Recently there has been much effort to achieve quantum entanglement and coherence on the nanoscale in atom traps and quantum dot aggregates (for use in quantum computing). We point out that the excitonic state of the Jaggregate is a text-book case of mesoscopic quantum coherence and entanglement. The establishment of coherence can literally be seen since the dye changes colour dramatically on aggregation, due to strong shifts in the absorption spectrum. Here, in a simple theory the shifts and shapes of optical absorption spectra upon aggregation to a polymer is reproduced and the coherence length of quantum entanglement of monomer wavefunctions is calculated. Alexander Eisfeld, John S. Briggs: Chemical Physics 281 (1) 61-70 (15 July 2002).
Argentine solar cells performance in space On December 1998, the Endeavour space shuttle launched the Argentine satellite SAC-A. Among several technological experiments, this satellite included a set of crystalline silicon solar cells fabricated in Argentina, to test them in the space environment. In this paper, the experiments associated with these solar cells are described and the corresponding telemetry data received from January to July 1999 are analysed. Fabrication and characterisation of modules are presented. Some preliminary radiation damage experiments using 10 MeV protons supplied by a cyclotron accelerator were also performed. C.G. Bolzi, C.J. Bruno, J.C. Durán, E.M. Godfrin, M.G. Martínez Bogado, L.M. Merino, J.C.Plá, M.J.L. Tamasi, M. Barrera: Solar Energy Materials and Solar Cells 73 (3) 269-280 (July 2002).
SiGe multicrystals with microscopic compositional distribution for highefficiency solar cells The growth technique and physical properties of SiGe multicrystals with microscopic compositional distribution are demonstrated for new high-efficiency solar cells in which the wavelength dependence of the absorption coefficient can be freely designed by controlling the compositional distribution in the SiGe multicrystals. This growth technique is suitable for the practical casting method, and it is made up of melt growth of SiGe multicrystals with wide and microscopic distribution of the composition from Si to Ge all over the crystals. How widely the microscopic compositional distribution in SiGe multicrystals, grown from binary Si-Ge melts can be controlled by the melt composition and the cooling process is studied.
The range of the microscopic compositional distribution widens as the start Si concentration in the growth melt becomes larger. SiGe multicrystals with various microscopic compositional distribution can be freely controlled by optimising the melt composition and the cooling process. The wavelength dependence of the absorption coefficient of such SiGe multicrystals can also be freely designed. Using the experimentally determined absorption coefficient of a SiGe crystal, with microscopic compositional distribution, the short circuit photo-current of solar cells was calculated. It is demonstrated that the short circuit photocurrent can be much larger for SiGe with microscopic compositional distribution than for SiGe with uniform composition. Si thin film can be easily grown on such a SiGe multicrystal and the Si/SiGe heterostructure can be obtained. These results show that SiGe multicrystals, with microscopic compositional distribution, are hopeful for new high-efficiency solar cell applications by using the practical casting method. K. Nakajima, N. Usami, K. Fujiwara, Y. Murakami, T. Ujihara, G. Sazaki, T. Shishido: Solar Energy Materials and Solar Cells 73 (3) 305-320 (July 2002).
Thermotropic polymer blends give facade systems variable control Thermotropic layers, integrated into glazing or transparent insulation systems, reversibly reduce the total solar energy transmittance by becoming opaque when heated. Characteristics of both systems have been measured as a function of temperature and incidence angle, including the total solar energy transmittance for a thermotropic heat-mirror insulating glazing unit (IGU). Properties of complex thermotropic glazing systems have been simulated, starting from data characterising the thermotropic layer. The results show good agreement with measured data. A prototype system sample of a thermotropic heat-mirror IGU was integrated into an outdoor test facility and a thermotropic TEIF (transparent exterior insulation and finish) prototype system was installed into the facade of a demonstration house. Both systems have been monitored and showed the expected switching properties, resulting in the desired overheating protection. Computer simulations of the building integration of the thermotropic TEIF system have been performed, showing a strong dependence of the optimum switching temperature on the total solar and internal gains of the building. A. Raicu, H.R. Wilson, P. Nitz, W. Platzer, V. Wittwer, E. Jahns: Solar Energy Materials and Solar Cells 73 (3) 305–320 (July 2002).
Photovoltaics Bulletin
13
Research Trends Photovoltaics ¯¯ sustainable futures As both population and energy use per capita increase, modern society is approaching physical limits to its continued fossil fuel consumption. The immediate limits are set by the planet's ability to adapt to a changing atmospheric chemical composition, not the availability of resources. In order for a future society to be sustainable while operating at or above our current standard of living a shift away from carbon based energy sources must occur. An overview of the current state of active solar (photovoltaic) energy technology is provided here to outline a partial solution for the environmental problems caused by accelerating global energy expenditure. The technical, social, and economic benefits and limitations of PV technologies to provide electricity in both off-grid and on-grid applications are critically analyzed in the context of this shift in energy sources. It is shown that PV electrical production is a technologically feasible, economically viable, environmentally benign, sustainable, and socially equitable solution to society's future energy requirements. Joshua M. Pearce: Futures 34 (7) 663-674 (September 2002).
A grid-connected Greek PV installation This paper describes the installation, technical characteristics, operation and economic evaluation of one of the largest grid-connected photovoltaic (PV) systems installed in Greece, and in particular, in the island of Paros in the Aegean Sea. Attention is drawn to the impact of PV utilisation on ecological tourism, which is growing very fast in Greece. Also, several issues are considered when assessing the value of PV electricity. The value of PV has been examined from various consumer, utility and environmental perspectives and for central and decentralised PV systems in conjunction with the benefits for all the involved parties, i.e. the owners, operators, users, tourists, investors, renewable system industry and local authorities. G.C. Bakos, M. Soursos: Energy and Buildings 34 (7) 753-758 (August 2002).
J-band of organic dyes: lineshape and coherence length Self-organised J-aggregates of dye molecules, known for over 60 years, are emerging as remarkably versatile quantum systems with applications in photography, optoelectronics, solar cells, photobiology and as supra-molecular
August 2002
fibres. Recently there has been much effort to achieve quantum entanglement and coherence on the nanoscale in atom traps and quantum dot aggregates (for use in quantum computing). We point out that the excitonic state of the Jaggregate is a text-book case of mesoscopic quantum coherence and entanglement. The establishment of coherence can literally be seen since the dye changes colour dramatically on aggregation, due to strong shifts in the absorption spectrum. Here, in a simple theory the shifts and shapes of optical absorption spectra upon aggregation to a polymer is reproduced and the coherence length of quantum entanglement of monomer wavefunctions is calculated. Alexander Eisfeld, John S. Briggs: Chemical Physics 281 (1) 61-70 (15 July 2002).
Argentine solar cells performance in space On December 1998, the Endeavour space shuttle launched the Argentine satellite SAC-A. Among several technological experiments, this satellite included a set of crystalline silicon solar cells fabricated in Argentina, to test them in the space environment. In this paper, the experiments associated with these solar cells are described and the corresponding telemetry data received from January to July 1999 are analysed. Fabrication and characterisation of modules are presented. Some preliminary radiation damage experiments using 10 MeV protons supplied by a cyclotron accelerator were also performed. C.G. Bolzi, C.J. Bruno, J.C. Durán, E.M. Godfrin, M.G. Martínez Bogado, L.M. Merino, J.C.Plá, M.J.L. Tamasi, M. Barrera: Solar Energy Materials and Solar Cells 73 (3) 269-280 (July 2002).
SiGe multicrystals with microscopic compositional distribution for highefficiency solar cells The growth technique and physical properties of SiGe multicrystals with microscopic compositional distribution are demonstrated for new high-efficiency solar cells in which the wavelength dependence of the absorption coefficient can be freely designed by controlling the compositional distribution in the SiGe multicrystals. This growth technique is suitable for the practical casting method, and it is made up of melt growth of SiGe multicrystals with wide and microscopic distribution of the composition from Si to Ge all over the crystals. How widely the microscopic compositional distribution in SiGe multicrystals, grown from binary Si-Ge melts can be controlled by the melt composition and the cooling process is studied.
The range of the microscopic compositional distribution widens as the start Si concentration in the growth melt becomes larger. SiGe multicrystals with various microscopic compositional distribution can be freely controlled by optimising the melt composition and the cooling process. The wavelength dependence of the absorption coefficient of such SiGe multicrystals can also be freely designed. Using the experimentally determined absorption coefficient of a SiGe crystal, with microscopic compositional distribution, the short circuit photo-current of solar cells was calculated. It is demonstrated that the short circuit photocurrent can be much larger for SiGe with microscopic compositional distribution than for SiGe with uniform composition. Si thin film can be easily grown on such a SiGe multicrystal and the Si/SiGe heterostructure can be obtained. These results show that SiGe multicrystals, with microscopic compositional distribution, are hopeful for new high-efficiency solar cell applications by using the practical casting method. K. Nakajima, N. Usami, K. Fujiwara, Y. Murakami, T. Ujihara, G. Sazaki, T. Shishido: Solar Energy Materials and Solar Cells 73 (3) 305-320 (July 2002).
Thermotropic polymer blends give facade systems variable control Thermotropic layers, integrated into glazing or transparent insulation systems, reversibly reduce the total solar energy transmittance by becoming opaque when heated. Characteristics of both systems have been measured as a function of temperature and incidence angle, including the total solar energy transmittance for a thermotropic heat-mirror insulating glazing unit (IGU). Properties of complex thermotropic glazing systems have been simulated, starting from data characterising the thermotropic layer. The results show good agreement with measured data. A prototype system sample of a thermotropic heat-mirror IGU was integrated into an outdoor test facility and a thermotropic TEIF (transparent exterior insulation and finish) prototype system was installed into the facade of a demonstration house. Both systems have been monitored and showed the expected switching properties, resulting in the desired overheating protection. Computer simulations of the building integration of the thermotropic TEIF system have been performed, showing a strong dependence of the optimum switching temperature on the total solar and internal gains of the building. A. Raicu, H.R. Wilson, P. Nitz, W. Platzer, V. Wittwer, E. Jahns: Solar Energy Materials and Solar Cells 73 (3) 305–320 (July 2002).
Photovoltaics Bulletin
13