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The influence of the incident spectral irradiance on the electrical and thermal behaviour of triple-junction solar cells has been investigated. A spectral dependent electrical model has been developed to calculate the electric characteristics and quantify the heat power of a multijunction solar cell. A three-dimensional finite element analysis is also used to predict the solar cell’s operating temperature and cooling requirements for a range of ambient temperatures. The combination of these models improves the prediction accuracy of the electrical and thermal behaviour of triple-junction solar cells. The convective heat transfer coefficient between the back-plate and ambient air was found to be the significant parameter in achieving high electrical efficiency. These data are important for the electrical and thermal optimisation of concentrating photovoltaic systems under real conditions. The objective of this work is to quantify the temperature and cooling requirements of multijunction solar cells under variable solar spectra and ambient temperatures. It is shown that single cell configurations with a solar cell area of 1 cm 2 can be cooled passively for concentration ratios of up to 500× with a heat sink thermal resistance below 1.63 K/W, however for high ambient temperatures (greater than 40 °C), a thermal resistance less than 1.4 K/W is needed to keep the solar cell operating within safe operating conditions. [ABSTRACT FROM AUTHOR]

Monitoring the performance of concentrating photovoltaic technologies under actual operating conditions is crucial for the prediction of energy yield. This requires an in-depth understanding of the behaviour of such systems through extensive outdoor characterisation and modelling. Detailed information on the outdoor performance of concentrating photovoltaic technology, taking into account the parameters that influence it, is therefore necessary for the evolution of the technology. In this work, a concentrating photovoltaic monomodule was characterised in a high desert climate (in Albuquerque, New Mexico). Due to the complexity of the outdoor performance evaluation of this technology, three relatively clear-sky days that exhibited different atmospheric conditions were selected in order to reduce the noise on the measured parameters and therefore provide a better understanding of its behaviour. One-minute resolution data were accumulated in order to assess the behaviour of the monomodule under real operating conditions. Initially, the monomodule is electrically characterised based on spectral changes. Different spectral indices are evaluated to enable a direct comparison amongst them. The diurnal electrical characteristics and temperature of the monomodule as a function of spectral, irradiance and ambient conditions is then analysed. The results of the three selected days show a maximum operating efficiency of 23.2% while maximum temperatures of 70.3 °C and 67.6 °C are observed on the diode and heat sink respectively. The importance of considering the influence of the atmospheric parameters on the performance of concentrating photovoltaics is also highlighted. In particular, spectral gains of up to 5% are exhibited due to lower aerosol content and higher precipitable water combined. [ABSTRACT FROM AUTHOR]

The spectral sensitivity of a concentrating triple-junction (3J) solar cell has been investigated. The atmospheric parameters such as the air mass (AM), aerosol optical depth (AOD) and precipitable water (PW) change the distribution of the solar spectrum in a way that the spectral, electrical and thermal performance of a 3J solar cell is affected. In this paper, the influence of the spectral changes on the performance of each subcell and whole cell has been analysed. It has been shown that increasing the AM and AOD have a negative impact on the spectral and electrical performance of 3J solar cells while increasing the PW has a positive effect, although, to a lesser degree. A three-dimensional finite element analysis model is used to quantify the effect of each atmospheric parameter on the thermal performance for a range of heat transfer coefficients from the back-plate to the ambient air and also ambient temperature. It is shown that a heat transfer coefficient greater than 1300 W/(m 2 K) is required to keep the solar cell under 100 °C at all times. In order to get a more realistic assessment and also to investigate the effect of heat transfer coefficient on the annual energy yield, the methodology is applied for four US locations using data from a typical meteorological year (TMY3). [ABSTRACT FROM AUTHOR]