Dynamic simulation and exergetic optimization of a Concentrating Photovoltaic/ Thermal (CPVT) system

The development of a dynamic, theoretical model suitable for the prediction of the long-term performance of a parabolic-trough Concentrating Photovoltaic/Thermal CPVT system is discussed in the present study. The formulation of the mathematical model and the considered geometrical and operational parameters of the system, such as the characteristics of the employed PV modules and active cooling system are described in detail. The effect of heat capacity is taken into consideration in the thermal balances and thus the model is able to capture the transient behavior of the system. Besides, the model is validated using available experimental data of a manufactured prototype CPVT system. The daily performance of system is predicted for different values of the cooling fluid flow rate and temperature under various environmental conditions. At a second stage, an exergy analysis is conducted in order to point out the effect of the characteristics of the main system sub-components on the exergetic efficiency and exergy output of the CPVT system. It was established that the system exergetic performance is primarily influenced by the optical quality of the parabolic trough and the electrical efficiency of the PV module. Increasing these two factors to achievable values, e.g. ηopt = 0.75 and ηel = 0.25, can yield an increase of the system exergetic efficiency from 12% to 24%

Handbook of space environmental effects on solar cell power systems

Space environmental effects on solar cell power systems for earth satellite

Radiation Study of the Organic Photovoltaic Cell P3HT:PCBM

The need for inexpensive, dependable, radiation hard solar cells for use in space applications has led to attention being focused on organic semiconductor based solar cells. Such cells are lightweight, flexible and are potentially useful in conformal coverage applications. While these solar cells are less efficient (presently \u3c 12%) than traditional silicon or III-V semiconductor based solar cells, the reduced efficiency is compensated for by their lower weight. This leads to a higher specific power and hence a lower load for launch. Furthermore, their flexibility is a particularly positive attribute since this renders them less vulnerable to vibration damage during the launch process. It must also be added that since one envisages solution processing deposition of the organic cells on very large area sheets (roll by roll technology) one can then also imagine a scenario in which a chosen panel area can be simply tailored from a large roll, thereby speeding up the process of solar panel production. Before this somewhat futuristic approach to low power solar panel production can become a reality for space applications, a full evaluation/understanding of their behavior in a radiation environment is necessary. In this work, a detailed study has been performed on the archetypal organic photovoltaic P3HT:PCBM. The interest of the applicability of organic photo-cells for use in space based solar panels is derived from the recognition that unusual\u27 conditions exist which are not generally addressed by the organic photo-cell community. The defense presentation will cover the findings of pre-irradiation, irradiation, and post-irradiation characteristics; determination of the physical mechanisms resulting in the dominant photo-carrier loss mechanism, and a detailed investigation of the radiation effects. Transient photo-voltage (TPV) measurements were utilized to evaluate carrier relaxation times in P3HT:PCBM based photo-cells over a wide range of open circuit voltages. Satisfactory agreement is found with data obtained by low frequency impedance measurements. This data set offers valuable insight into the loss mechanism to help material scientists develop new material that has better power conversion efficiency. Furthermore, the results are promising for the development OPV technology for space based applications. We find that the experimental data is inconsistent with the theoretical behavior expected based on the generally accepted Langevin recombination model. In particular, the Langevin coefficient is three orders of magnitude smaller than the theoretical one and appears to be dependent on the carrier density. For the low light levels, the relaxation time variation is determined by the RC time constant behavior of the photodiode.\u2