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04778 Installation and operation of the first city centre PV monitoring station in the United Kingdom
07
Alternative
energy sources (solar energy)
Development 97104774 film substrate solar cells
of process
technologies
for plastic-
Yoshida, T. ef al. Solar Enerb~~ Muter;& uncl Solar Cells. lYY7, 4X. (l-4), The paper focuses its study on process technologies developed for plasticfilm substrate solar cells. The solar cells have a monolithic series-connected structure named ‘SCAF’ and are fabricated by a developed fabrication process hased on roll-to-roll systems. A newly developed roll-to-roll vacuum laminator is used to encapsulate the fabricated cells. Pilot productions for SCAF cells are carried out and the process reproducibility is confirmed. The details of the processes are presented and their advantages discussed.
Experimental investigation cluster of photovoltaic panels
97104775
on
a series-parallel
lYY7. hl, (4), 231-240. Kattakayam, T. A. and Srinivasan, K. SolarEN!r~, Results of experimental investigations on a field of eight photovoltaic panels assembled two in series and four such parallel combinations are presented. The diurnal and environmental effects have heen characterized systematically. The panels are hoth clean and dusty and the centres of each series combinations both shorted and unshorted. The curvature at the maximum power point of the I-V curve, it is claimed, could be an indicator of the panel characteristics. The temperature effects on the voltage at the maximum power point are also discussed. Field evaluation is deemed essential and often maximum power point tracking can he dispensed with if a known load exists and a judicious choice of battery bank capacity is made.
High efficiency solar air heater 97104776 Mohamad, A. A. Solar E?lesy, lY97, 60, (2). 71-76. A novel type of solar air heater is analysed. The main idea is to minimize heat losses from the front cover of the collector and to maximize heat extraction from the absorber. Forcing air to flow over the front glass cover (preheat the air) before passing through the absorber can achieve this objective. Hence. this design needs an extra cover to form a counter-flow heat exchanger. Porous media forms an extensive area for heat transfer, where the volumetric heat transfer coefficient is very high; it will enhance heat transfer from the absorber to the airstream. In the design of this type of collector, which comhines double air passage and porous media, pressure drop should be minimized. However, the thermal efficiency of this type of collector is significantly higher than the thermal efficiency of conventional air heaters, exceeding 75% under normal operating conditions. The pressure drop is not so significant if high porous medium is used and careful design of U-return section is considered. Improvement 97104777 teries for PV systems
of performance
in redox
flow
bat-
Tsuda. 1. et al. Solar Enerp Mu!erinl,y urld Solar Cell.\, 1997, 47. (l-4). 101-107. A new type of battery, called the redox flow battery (RFB), is introduced with a new piping system to improve the performance of RFBs for PV systems is introduced. In this new system, the piping for the electrolytes also connects each stack in series just like the electric circuit. In this system, the leak current through the electrolytes is suppressed in the piping between each stack. It is called the multitank system because it has many mini tanks between each stack. Experimental and simulation results confirm this system improves the performance of RFBs. 97104776
monitoring
Installation and operation of the first city centre PV station in the United Kingdom
Wilshaw, A. R. ef ul. Solar E‘ner~. 1997, 59, (l-3). 19-26. The application of PV in buildings throughout northern Europe has become the subject of increasing interest. In turn this has developed a need for long-term records of the solar resource in urban situations. Previous records have usually been collected from locations quite remote from city centre sites and, furthermore, at hourly sampling frequencies which are not rapid enough for photovoltaic applications. The installation of a photovoltaic monitoring station in a city centre in the north-east of England is described. Weather monitoring instruments were installed to measure ambient temperature, wind speed and direction, relative humidity and solar irradiance. Four types of photovoltaic modules arc mounted on the rig in typical building orientations in order to assess their performance with respect to PV cladding applications. Preliminary investigations have shown that the electricity generated by PV cladding on vertical surfaces experiences much less seasonal variation than that on a horizontal surface. The performance of north and south facing modules has also been compared and this has shown that the north facing modules generate reasonably large amounts of electricity, particularly during the summer months.
Integrated high-concentration PV-near-term alter97104779 native for low-cost large-scale solar electric power Garhoushian, V. e/ al. S&r Enemy Marer~a1.s and Solar Cells, 1997, 47, (l4), 31.5-323. Economic, as opposed to technical, constraints now dictate the path of large-scale photovoltaic electric power generation utilization. Other renewable or traditional options remain more attractive in terms of costs. A nearterm alternative option for cost-effective solar electric power generation based on a novel sunlight concentrating technology is presented: integrated high-concentration PV (IHCPV). The advantages of high-concentration systems have been thoroughly analysed. but the absence of a solar cell capable of withstanding the rigors of concentrated sunlight has hindered
414
Fuel and Energy Abstracts
November
1997
development. A stable, high-concentration back-junction. point-contact cell, by Amonix, paved the way for high-concentration system development. The IHCPV system was a success for designers as savings resulting from the reduction of costly solar cell content were not over-shadowed hy the ancillary costs of structure and tracking elements used in concentrating arrays. Economic factors specific to the IHCPV system are presented including (I) low cost of entry. (2) enhanced energy production, (3) reduced land utilization, and (4) accelerated henefita of volume production.
97i94789 Long-term scenarios for the integration of photovoltaics into the global energy system Sflrensen. B. Solar Erww md Solar Ce/l~. IYY7. 47. ( l-4). 2113-2 I I, The role of photovoltaics in current energy scenario work on a local. regional or global scale is discussed for the middle of the next century.
97i947at
Low cost photovoltaic
roof tile
Wenhama. S. R. et al. Solar Emrgy Marrriuls untl Solrrr C’e//\. 1007. 47. (I4). 325-337. Concentration ratios approaching the theoretlcal limit have heen achieved in new static concentrator design\. Concentration ratio< in excess of 4: I have been predicted although this reduces to 3.(,:1 for the practical design used for photovoltaic roof tile applications. A new encapsulant based on’ solid white oil’ has been evaluated for use in the optical cavity. exhibiting both excellent optical properties and low cost. Prototype roof tile efficiencies of approximately 15% are well helow the expected 17-1X%. primarily due to optical losses associated with the rear reflector and poor rear surface performance for the photovoltaic devices. This problem ha5 been approached with some success, although further work is required to accommodate solar grade substrates with much shorter diffusion lengths for the hi-facial cells in this application.
97104782 Microcontroller-based alone photovoltaic systems
charge
controller
for stand-
Masheleni, H. and Carelse. X. F. So/or Emp, lYY7. 01, (4). 775-2.31). The use of PV systems for rural electrification is widespread in the Third World. In order to improve the efficiency of the system and to protect the storage batteries charge controllers are needed. An intelligent charge controller, incorporating an SGS-Thompson microcontroller, STh2E20, has been designed aiming to prolong battery life. The nred for and advantage\ of such charge controllers arc discussed. A versatile working prototype has provision for more monitoring and control functions than are possible with the conventional logic or relay system\: it has been subject to testing. A photovoltaic charge control algorithm is discussed.
97104783 photovoltaic
Microprocessor systems
based
load voltage
regulator
for
Anis, W. R. and El-Samahy, A. E.-S. M. Euerp C’orrt,cu. .&Q/n,.. lYcJ7. 3X. (I), 13-20. The voltage of typical lead-acid batterie<. widely used in PV systems. varies between 93.5 and 120%~ of its nominal voltage according to its state of charge. Such voltage variations are accepted for many d.c. load\. However. critical loads, such as some communication systems. require a regulated voltage and such battery voltage variations are therefore unacceptable. The conventional solution of this problem is to operate the PV system at a higher voltage and to include a control circuit that introduces passive elements so that the load is operating within the allowed limits. Power dissipation occurs in the passive elements when using this method and this presents power loss. An alternative solution based on a microprocessor that keeps the load voltage at the predetermined level is discused. The proposed technique avoids the power loss, and as a result, the required PV array size becomes smaller, thus improving the economics of the system.
97194784 climates
Optimal
sizing
of photovoltaic
systems
in varied
Samimi, J. ef al. Solar Ener~, 1997, 60, (2). 97-107. From an economic standpoint, optimal utilization of solar cell modules in varied climates is critical. In many locations, especially in the rural areas and remote sites, because of the lack of solar irradiation and climatological data, uneconomic utilization of the solar modules is common. In thi\ work. using solar irradiation estimation and cloud cover data interpolation techniques, and incorporating the irradiation dependent efficiency function of the solar cells, the tilt angle of the modules is first optimized. The cloud cover data is then used to estimate the expected number of \ucccssivc cloudy days in each month with the result applied for optimal sizing of the storage battery. This optimization technique has been applied to the varied climates of Iran.
97104785 The optimization power generation
of a holographic
system for solar
Ludman, J. E. ef al. Solar Emzrgy. 1997. ho, (I). 119-126. Solar energy conversion efficiency can be greatly improved using a recently developed holographic device. The single-element hologram focuses light. spectrally splits it and diverts unwanted infrared heat away from the solar cells. The output appears as a thin concentrated line, focused perpendicular to the hologram and displaced to the side. Solar cells are placed along this line such that each cell ahsorhs only the wavelengths which it can efficiently convert to electric power. The theoretical and experimental development of this system and its application in space and on Earth arc discusard. The system is excellent for space applications since the holograms are \ingle
Alternative
energy sources (solar energy)
Development 97104774 film substrate solar cells
of process
technologies
for plastic-
Yoshida, T. ef al. Solar Enerb~~ Muter;& uncl Solar Cells. lYY7, 4X. (l-4), The paper focuses its study on process technologies developed for plasticfilm substrate solar cells. The solar cells have a monolithic series-connected structure named ‘SCAF’ and are fabricated by a developed fabrication process hased on roll-to-roll systems. A newly developed roll-to-roll vacuum laminator is used to encapsulate the fabricated cells. Pilot productions for SCAF cells are carried out and the process reproducibility is confirmed. The details of the processes are presented and their advantages discussed.
Experimental investigation cluster of photovoltaic panels
97104775
on
a series-parallel
lYY7. hl, (4), 231-240. Kattakayam, T. A. and Srinivasan, K. SolarEN!r~, Results of experimental investigations on a field of eight photovoltaic panels assembled two in series and four such parallel combinations are presented. The diurnal and environmental effects have heen characterized systematically. The panels are hoth clean and dusty and the centres of each series combinations both shorted and unshorted. The curvature at the maximum power point of the I-V curve, it is claimed, could be an indicator of the panel characteristics. The temperature effects on the voltage at the maximum power point are also discussed. Field evaluation is deemed essential and often maximum power point tracking can he dispensed with if a known load exists and a judicious choice of battery bank capacity is made.
High efficiency solar air heater 97104776 Mohamad, A. A. Solar E?lesy, lY97, 60, (2). 71-76. A novel type of solar air heater is analysed. The main idea is to minimize heat losses from the front cover of the collector and to maximize heat extraction from the absorber. Forcing air to flow over the front glass cover (preheat the air) before passing through the absorber can achieve this objective. Hence. this design needs an extra cover to form a counter-flow heat exchanger. Porous media forms an extensive area for heat transfer, where the volumetric heat transfer coefficient is very high; it will enhance heat transfer from the absorber to the airstream. In the design of this type of collector, which comhines double air passage and porous media, pressure drop should be minimized. However, the thermal efficiency of this type of collector is significantly higher than the thermal efficiency of conventional air heaters, exceeding 75% under normal operating conditions. The pressure drop is not so significant if high porous medium is used and careful design of U-return section is considered. Improvement 97104777 teries for PV systems
of performance
in redox
flow
bat-
Tsuda. 1. et al. Solar Enerp Mu!erinl,y urld Solar Cell.\, 1997, 47. (l-4). 101-107. A new type of battery, called the redox flow battery (RFB), is introduced with a new piping system to improve the performance of RFBs for PV systems is introduced. In this new system, the piping for the electrolytes also connects each stack in series just like the electric circuit. In this system, the leak current through the electrolytes is suppressed in the piping between each stack. It is called the multitank system because it has many mini tanks between each stack. Experimental and simulation results confirm this system improves the performance of RFBs. 97104776
monitoring
Installation and operation of the first city centre PV station in the United Kingdom
Wilshaw, A. R. ef ul. Solar E‘ner~. 1997, 59, (l-3). 19-26. The application of PV in buildings throughout northern Europe has become the subject of increasing interest. In turn this has developed a need for long-term records of the solar resource in urban situations. Previous records have usually been collected from locations quite remote from city centre sites and, furthermore, at hourly sampling frequencies which are not rapid enough for photovoltaic applications. The installation of a photovoltaic monitoring station in a city centre in the north-east of England is described. Weather monitoring instruments were installed to measure ambient temperature, wind speed and direction, relative humidity and solar irradiance. Four types of photovoltaic modules arc mounted on the rig in typical building orientations in order to assess their performance with respect to PV cladding applications. Preliminary investigations have shown that the electricity generated by PV cladding on vertical surfaces experiences much less seasonal variation than that on a horizontal surface. The performance of north and south facing modules has also been compared and this has shown that the north facing modules generate reasonably large amounts of electricity, particularly during the summer months.
Integrated high-concentration PV-near-term alter97104779 native for low-cost large-scale solar electric power Garhoushian, V. e/ al. S&r Enemy Marer~a1.s and Solar Cells, 1997, 47, (l4), 31.5-323. Economic, as opposed to technical, constraints now dictate the path of large-scale photovoltaic electric power generation utilization. Other renewable or traditional options remain more attractive in terms of costs. A nearterm alternative option for cost-effective solar electric power generation based on a novel sunlight concentrating technology is presented: integrated high-concentration PV (IHCPV). The advantages of high-concentration systems have been thoroughly analysed. but the absence of a solar cell capable of withstanding the rigors of concentrated sunlight has hindered
414
Fuel and Energy Abstracts
November
1997
development. A stable, high-concentration back-junction. point-contact cell, by Amonix, paved the way for high-concentration system development. The IHCPV system was a success for designers as savings resulting from the reduction of costly solar cell content were not over-shadowed hy the ancillary costs of structure and tracking elements used in concentrating arrays. Economic factors specific to the IHCPV system are presented including (I) low cost of entry. (2) enhanced energy production, (3) reduced land utilization, and (4) accelerated henefita of volume production.
97i94789 Long-term scenarios for the integration of photovoltaics into the global energy system Sflrensen. B. Solar Erww md Solar Ce/l~. IYY7. 47. ( l-4). 2113-2 I I, The role of photovoltaics in current energy scenario work on a local. regional or global scale is discussed for the middle of the next century.
97i947at
Low cost photovoltaic
roof tile
Wenhama. S. R. et al. Solar Emrgy Marrriuls untl Solrrr C’e//\. 1007. 47. (I4). 325-337. Concentration ratios approaching the theoretlcal limit have heen achieved in new static concentrator design\. Concentration ratio< in excess of 4: I have been predicted although this reduces to 3.(,:1 for the practical design used for photovoltaic roof tile applications. A new encapsulant based on’ solid white oil’ has been evaluated for use in the optical cavity. exhibiting both excellent optical properties and low cost. Prototype roof tile efficiencies of approximately 15% are well helow the expected 17-1X%. primarily due to optical losses associated with the rear reflector and poor rear surface performance for the photovoltaic devices. This problem ha5 been approached with some success, although further work is required to accommodate solar grade substrates with much shorter diffusion lengths for the hi-facial cells in this application.
97104782 Microcontroller-based alone photovoltaic systems
charge
controller
for stand-
Masheleni, H. and Carelse. X. F. So/or Emp, lYY7. 01, (4). 775-2.31). The use of PV systems for rural electrification is widespread in the Third World. In order to improve the efficiency of the system and to protect the storage batteries charge controllers are needed. An intelligent charge controller, incorporating an SGS-Thompson microcontroller, STh2E20, has been designed aiming to prolong battery life. The nred for and advantage\ of such charge controllers arc discussed. A versatile working prototype has provision for more monitoring and control functions than are possible with the conventional logic or relay system\: it has been subject to testing. A photovoltaic charge control algorithm is discussed.
97104783 photovoltaic
Microprocessor systems
based
load voltage
regulator
for
Anis, W. R. and El-Samahy, A. E.-S. M. Euerp C’orrt,cu. .&Q/n,.. lYcJ7. 3X. (I), 13-20. The voltage of typical lead-acid batterie<. widely used in PV systems. varies between 93.5 and 120%~ of its nominal voltage according to its state of charge. Such voltage variations are accepted for many d.c. load\. However. critical loads, such as some communication systems. require a regulated voltage and such battery voltage variations are therefore unacceptable. The conventional solution of this problem is to operate the PV system at a higher voltage and to include a control circuit that introduces passive elements so that the load is operating within the allowed limits. Power dissipation occurs in the passive elements when using this method and this presents power loss. An alternative solution based on a microprocessor that keeps the load voltage at the predetermined level is discused. The proposed technique avoids the power loss, and as a result, the required PV array size becomes smaller, thus improving the economics of the system.
97194784 climates
Optimal
sizing
of photovoltaic
systems
in varied
Samimi, J. ef al. Solar Ener~, 1997, 60, (2). 97-107. From an economic standpoint, optimal utilization of solar cell modules in varied climates is critical. In many locations, especially in the rural areas and remote sites, because of the lack of solar irradiation and climatological data, uneconomic utilization of the solar modules is common. In thi\ work. using solar irradiation estimation and cloud cover data interpolation techniques, and incorporating the irradiation dependent efficiency function of the solar cells, the tilt angle of the modules is first optimized. The cloud cover data is then used to estimate the expected number of \ucccssivc cloudy days in each month with the result applied for optimal sizing of the storage battery. This optimization technique has been applied to the varied climates of Iran.
97104785 The optimization power generation
of a holographic
system for solar
Ludman, J. E. ef al. Solar Emzrgy. 1997. ho, (I). 119-126. Solar energy conversion efficiency can be greatly improved using a recently developed holographic device. The single-element hologram focuses light. spectrally splits it and diverts unwanted infrared heat away from the solar cells. The output appears as a thin concentrated line, focused perpendicular to the hologram and displaced to the side. Solar cells are placed along this line such that each cell ahsorhs only the wavelengths which it can efficiently convert to electric power. The theoretical and experimental development of this system and its application in space and on Earth arc discusard. The system is excellent for space applications since the holograms are \ingle