Outdoor Testing in Qatar of PV Performance, Reliability and Safety

Abstract

Although PV has made remarkable progress in reducing costs, the absolute cost is highly related to the reliability of system components, which is determined by the life span in which PV remains fully functioning. Longer life is especially required for the solar panels when their initial cost is relatively high and therefore longer life guarantees their pay back and increases their profit. Indeed great efforts have been spent by manufacturers to make the panels more reliable and durable to the hard environmental conditions. In spite of careful design and production conditions during manufacturing, the environmental cyclic stresses cause irreversible changes in the solar cells that cause them to partially totally malfunction gradually with time. An accurate measurement of power drop over time, (or degradation rate), is essential to all stakeholders, industry, and investors.What are the factors affecting the reliability of solar PV technology in harsh environments?PV technologies are designed to deliver amounts of solar electricity, which is varying differently when submitted to harsh environments (temperature, soiling, UV radiation, wind). The temperature is one of the main factors affecting the power output of a PV system. Researchers may explore the so-called NOCT rating or “normal operating cell temperature” which is indicative of module temperature.Based on the difference between module temperature and ambient temperature, NOCT can be calculated for crystalline Silicon [1], and thin films [2]. However the influence of other environmental factors must be taken into account when determining the amount of energy (in watt-hour or Wh) produced during a period of time to ensure the consistency and performance criteria of PV systems. Solar Test Facilities in Qatar Foundation: In Qatar, prediction of PV performance can be improved through statistical data collected from PV fields. QEERI is collaborating with Qatar Science & Technology Park and GreenGulf on research at the Solar Test Facility, and developing state of the art solar test laboratory facilities, in order to provide information to stakeholders and industry for better deployment of PV technology in Qatar to meet the Energy grand challenges of the country. A wide variety of equipment, tools, and techniques are used to explore and follow-up failures of PV modules for different technologies. Since March 2013 around 20 photovoltaic technologies have been continually tested at the outdoor Solar Test Facility at Qatar Science & Technology Park. Solar energy technologies at the STF include: Crystalline, thin film, including concentrating (thermal Linear Fresnel collector) as well as battery storage. Overview of Solar Test Facility in QEERI: Two years of investigations have revealed the relative performance of different solar technologies in Qatar's climate, their reliability and degradation, and the impact of heat and dust on their efficiency. We found that flat-plate PV yields more energy than concentrating PV, due to diffuse light conditions at the STF [3]. Crystalline silicon and thin film PV had similar average yields. Of all PV technologies tested, only one-showed signs of severe degradation in the first two years. Dust and heat significantly reduced power output, but high levels of insolation in Qatar compensated this problem. Roadmap: • 2010: Initiated by QSTP, GreenGulf and Chevron• 2011–12: Systems installed• 2013: Testing commenced• 2014: QEERI joins collaboration Final Remarks: • We observed from our experimental data analysis that ordinary flat-plate PV is well suited to Qatar's conditions, provided it is cleaned occasionally.• Still a need to explore NOCT taking into account module and ambient temperature, available solar irradiance.• Correlation with simulated yearly module generation, module temperature, solar irradiation (GHI, DNI,) as well as soiling conditions. Acknowledgements: We thank GreenGulf and QSTP for providing data from the STF for this study