| dc.description.abstract | Hybrid solar photovoltaic-thermal systems (PV-T) generate electricity and heat simultaneously. The Nanosol project aims to develop such a PV-T system by combining a thin-film flexible amorphous Silicon solar module with tube shaped lamination to extract the heat. However, it was unclear whether it was favorable to cool the solar cell with air or with water, what the optimal design would be, what annual yield could be expected in the Netherlands and how the solar cell would be affected by longer periods of elevated temperatures.
To investigate these issues, a theoretical model was presented to simulate different PV-T systems. The model was based on the one from Hegazy (2000) that was used to simulate air-cooled collectors. For the purpose of this study, this model was improved and extended to also simulate water-cooled collectors. Two designs were simulated with either air or water to cool the solar cell, resulting in a total of four models; ' P1 Air' , ' P1 Water' , ' P2 Air' and ' P2 Water' . Prototype 1 is cooled from both the front and the backside of the solar cell and prototype 2 is only cooled from the backside. These models were simulated under standard test conditions and under real Dutch climate conditions. Also an experiment was conducted to investigate the effect of thermal annealing. Three modules were degraded in a light soaker and subsequently heated in different ovens at 60ºC, 90ºC and 120ºC for about 300 hours. The efficiencies were regularly measured during the degradation and heating process.
Results from the simulations at mass flow rates of 0.015 , showed annual electrical performances, including the required pumping power, of 7.88, 8.61, 7.46 and 8.64 percent for ' P1 Air' , ' P1 Water' , ' P2 Air' and ' P2 Water' respectively. A reference PV cell under the same conditions provided an annual electrical efficiency of 8.58 percent. The annual thermal efficiencies proved to be 23.77, 35.06, 14.52 and 29.70 percent for the four models. The annealing experiment showed a relative increase in efficiency of 0.031%, 0.130% and 0.339% per hour during the first 24 hours of thermal annealing at 60°C, 90°C and 120°C respectively. Thereafter, only a gradual improvement of the efficiency could be observed.
Model ' P1 Water' resulted to be the most favorable PV-T design. Water is beneficial for its superior properties compared to air, allowing for higher thermal and electrical yields. Additionally, water requires much less pumping power and is better compatible with other thermal applications. The effect of thermal annealing of this particular module in Dutch climate conditions is expected to be limited. | |
