Temperature Effects on Photovoltaic Energy Output Under Real Conditions: Weibull Model

International audiencePhotovoltaic (PV) modules are given a power rating at standard test conditions (STC) of 1000 W/m2 , AM1.5, and a module temperature of 25∘C. However, these conditions do not represent what is typically experienced under outdoor operation. PV technologies have different seasonal output behavior under real operating conditions due to variations of irradiance and different temperature coefficients of voltage and current that do influence on energy output. Solar photovoltaic resources can be modeled probabilistically, and a probability density function of the solar generation can be estimated. In this paper, we applied the Weibull analysis for energy output estimation to a small-scale photovoltaic power generator in real conditions and undergoing environmental stresses for a specific location. We studied two types of modules: crystalline silicon (c–Si) and amorphous silicon (a–Si) in real outdoor conditions. We measured and calculated monthly and annual power output and compared each system performance

A Review on Recent Development of Cooling Technologies for Photovoltaic Modules

When converting solar energy to electricity, a big proportion of energy is not converted for electricity but for heating PV cells, resulting in increased cell temperature and reduced electrical efficiency. Many cooling technologies have been developed and used for PV modules to lower cell temperature and boost electric energy yield. However, little crucial review work was proposed to comment cooling technologies for PV modules. Therefore, this paper has provided a thorough review of the up-to-date development of existing cooling technologies for PV modules, and given appropriate comments, comparisons and discussions. According to the ways or principles of cooling, existing cooling technologies have been classified as fluid medium cooling (air cooling, water cooling and nanofluids cooling), optimizing structural configuration cooling and phase change materials cooling. Potential influential factors and sub-methods were collected from the review work, and their contributions and impact have been discussed to guide future studies. Although most cooling technologies reviewed in this paper are matured, there are still problems need to be solved, such as the choice of cooling fluid and its usability for specific regions, the fouling accumulation and cleaning of enhanced heat exchangers with complex structures, the balance between cooling cost and net efficiency of PV modules, the cooling of circulating water in tropical areas and the freezing of circulating water in cold areas. To be advocated, due to efficient heat transfer and spectral filter characters, nanofluids can promote the effective matching of solar energy at both spectral and spatial scales to achieve orderly energy utilization