The Experts below are selected from a list of 1035 Experts worldwide ranked by ideXlab platform

Ramesh K Agarwal - One of the best experts on this subject based on the ideXlab platform.

  • some aspects of a pv t collector forced circulation flat plate solar water heater with solar cells
    Energy Conversion and Management, 1995
    Co-Authors: H P Garg, Ramesh K Agarwal
    Abstract:

    Solar energy is mainly utilized via two routes—thermal and electrical. Two forms of energy are generated by two separate systems. The present work is about the study of a system which combines thermal and photovoltaic systems in one unit. The system is basically a conventional forced circulation type water heater. It is converted into a combined system by pasting solar cells directly over the absorber plate. The system equations are solved by a finite difference method. The simulations are done for different solar cell areas, mass flow rates and different water masses. The Differential Temperature Controller, i.e. pump-off and pump-on, are used. It is shown that the pump-on time is more or less independent of the total stagnant water mass in the collector unit. The pump-off time is a sensitive function of the water flow rate. At higher flow rates, the pump is switched off early in the afternoon. Since the total working time decreases, the efficiency also decreases. There is an optimum flow rate for which the collector efficiency is a maximum. The cell efficiency, which is a function of Temperature, is calculated using an iterative method. The average cell efficiency turns out to be more or less independent of the solar cell area on the absorber plate. This result helps in saving calculation time because the total electrical energy available for any solar cell area can be calculated simply. A normal domestic solar water heater of about 2 m2 generates sufficient electrical energy (after taking into account the various losses in storage, etc. and the energy required by the pump) to run 2 tube lights of 20 W each for 5 h and 1 television of 30 W for 4 h.

  • SOME ASPECTS OF A PV/T COLLECTOR/FORCED CIRCULATION FLAT PLATE SOLAR WATER HEATER WITH SOLAR CELLS
    Energy Conversion and Management, 1995
    Co-Authors: H P Garg, Ramesh K Agarwal
    Abstract:

    Solar energy is mainly utilized via two routes—thermal and electrical. Two forms of energy are generated by two separate systems. The present work is about the study of a system which combines thermal and photovoltaic systems in one unit. The system is basically a conventional forced circulation type water heater. It is converted into a combined system by pasting solar cells directly over the absorber plate. The system equations are solved by a finite difference method. The simulations are done for different solar cell areas, mass flow rates and different water masses. The Differential Temperature Controller, i.e. pump-off and pump-on, are used. It is shown that the pump-on time is more or less independent of the total stagnant water mass in the collector unit. The pump-off time is a sensitive function of the water flow rate. At higher flow rates, the pump is switched off early in the afternoon. Since the total working time decreases, the efficiency also decreases. There is an optimum flow rate for which the collector efficiency is a maximum. The cell efficiency, which is a function of Temperature, is calculated using an iterative method. The average cell efficiency turns out to be more or less independent of the solar cell area on the absorber plate. This result helps in saving calculation time because the total electrical energy available for any solar cell area can be calculated simply. A normal domestic solar water heater of about 2 m2 generates sufficient electrical energy (after taking into account the various losses in storage, etc. and the energy required by the pump) to run 2 tube lights of 20 W each for 5 h and 1 television of 30 W for 4 h.

António Joyce - One of the best experts on this subject based on the ideXlab platform.

  • On Differential Temperature Controller Setpoint Selection for Active Photovoltaic-Thermal (PV-T) Systems
    European Journal of Sustainable Development Research, 2019
    Co-Authors: Pedro M. L. P. Magalhães, João Martins, António Joyce
    Abstract:

    Active photovoltaic-thermal (PV-T) systems for solar heating and electricity generation are likely to employ the same Differential Temperature pump Controllers as equivalent non-hybrid solar thermal (ST) systems. However, the typical Controller setpoint selection methods for cost-effective and stable pump operation fail to consider the effect on photovoltaic (PV) electricity generation taking place in PV-T systems. Analytical relations for the same goals were derived to anticipate this influence using the steady-state Florschuetz PV-T collector model and compared with equivalent numerical methods relying on an extension of the Perers model designed to encompass PV-T collectors, namely by modelling electricity generation and the associated thermal performance reduction. Both methods indicate the minimum turn-on and turn-off setpoints for cost-effective and stable operation increase and decrease, respectively, relative to those for non-hybrid operation of PV-T systems or equivalent non-hybrid systems, and more so at higher irradiance levels, though the variations are shown not to be significant for a range of PV-T systems represented and can be reasoned to be inflated or of limited practical relevance. In conclusion, the effect of pump operation on electricity generation is not predicted to be a determining factor for Differential Temperature Controller setpoint selection in PV-T systems.

S. Mohan - One of the best experts on this subject based on the ideXlab platform.

H P Garg - One of the best experts on this subject based on the ideXlab platform.

  • some aspects of a pv t collector forced circulation flat plate solar water heater with solar cells
    Energy Conversion and Management, 1995
    Co-Authors: H P Garg, Ramesh K Agarwal
    Abstract:

    Solar energy is mainly utilized via two routes—thermal and electrical. Two forms of energy are generated by two separate systems. The present work is about the study of a system which combines thermal and photovoltaic systems in one unit. The system is basically a conventional forced circulation type water heater. It is converted into a combined system by pasting solar cells directly over the absorber plate. The system equations are solved by a finite difference method. The simulations are done for different solar cell areas, mass flow rates and different water masses. The Differential Temperature Controller, i.e. pump-off and pump-on, are used. It is shown that the pump-on time is more or less independent of the total stagnant water mass in the collector unit. The pump-off time is a sensitive function of the water flow rate. At higher flow rates, the pump is switched off early in the afternoon. Since the total working time decreases, the efficiency also decreases. There is an optimum flow rate for which the collector efficiency is a maximum. The cell efficiency, which is a function of Temperature, is calculated using an iterative method. The average cell efficiency turns out to be more or less independent of the solar cell area on the absorber plate. This result helps in saving calculation time because the total electrical energy available for any solar cell area can be calculated simply. A normal domestic solar water heater of about 2 m2 generates sufficient electrical energy (after taking into account the various losses in storage, etc. and the energy required by the pump) to run 2 tube lights of 20 W each for 5 h and 1 television of 30 W for 4 h.

  • SOME ASPECTS OF A PV/T COLLECTOR/FORCED CIRCULATION FLAT PLATE SOLAR WATER HEATER WITH SOLAR CELLS
    Energy Conversion and Management, 1995
    Co-Authors: H P Garg, Ramesh K Agarwal
    Abstract:

    Solar energy is mainly utilized via two routes—thermal and electrical. Two forms of energy are generated by two separate systems. The present work is about the study of a system which combines thermal and photovoltaic systems in one unit. The system is basically a conventional forced circulation type water heater. It is converted into a combined system by pasting solar cells directly over the absorber plate. The system equations are solved by a finite difference method. The simulations are done for different solar cell areas, mass flow rates and different water masses. The Differential Temperature Controller, i.e. pump-off and pump-on, are used. It is shown that the pump-on time is more or less independent of the total stagnant water mass in the collector unit. The pump-off time is a sensitive function of the water flow rate. At higher flow rates, the pump is switched off early in the afternoon. Since the total working time decreases, the efficiency also decreases. There is an optimum flow rate for which the collector efficiency is a maximum. The cell efficiency, which is a function of Temperature, is calculated using an iterative method. The average cell efficiency turns out to be more or less independent of the solar cell area on the absorber plate. This result helps in saving calculation time because the total electrical energy available for any solar cell area can be calculated simply. A normal domestic solar water heater of about 2 m2 generates sufficient electrical energy (after taking into account the various losses in storage, etc. and the energy required by the pump) to run 2 tube lights of 20 W each for 5 h and 1 television of 30 W for 4 h.

Pedro M. L. P. Magalhães - One of the best experts on this subject based on the ideXlab platform.

  • On Differential Temperature Controller Setpoint Selection for Active Photovoltaic-Thermal (PV-T) Systems
    European Journal of Sustainable Development Research, 2019
    Co-Authors: Pedro M. L. P. Magalhães, João Martins, António Joyce
    Abstract:

    Active photovoltaic-thermal (PV-T) systems for solar heating and electricity generation are likely to employ the same Differential Temperature pump Controllers as equivalent non-hybrid solar thermal (ST) systems. However, the typical Controller setpoint selection methods for cost-effective and stable pump operation fail to consider the effect on photovoltaic (PV) electricity generation taking place in PV-T systems. Analytical relations for the same goals were derived to anticipate this influence using the steady-state Florschuetz PV-T collector model and compared with equivalent numerical methods relying on an extension of the Perers model designed to encompass PV-T collectors, namely by modelling electricity generation and the associated thermal performance reduction. Both methods indicate the minimum turn-on and turn-off setpoints for cost-effective and stable operation increase and decrease, respectively, relative to those for non-hybrid operation of PV-T systems or equivalent non-hybrid systems, and more so at higher irradiance levels, though the variations are shown not to be significant for a range of PV-T systems represented and can be reasoned to be inflated or of limited practical relevance. In conclusion, the effect of pump operation on electricity generation is not predicted to be a determining factor for Differential Temperature Controller setpoint selection in PV-T systems.