Efficiency and Annual Output of a Monocrystalline Photovoltaic Module under Actual Operating Conditions

Abstract

This work covers extensive outdoor testing of a mc-Si module from Jumao Photonics (JM-050W-S4-G). All tests were performed at PSI’s Solar Test Facility. The location of PSI represents a typical site in the Swiss Midland. The module was fixed on a sun tracker and tested under clear sky conditions as well as under a cloudy sky. During testing, the global-normal irradiance varied between 56 and 1087 W/m2, the cell temperature between 9 and 67°C, and the relative air mass between 1.1 and 9.6. About 2000 current/voltage characteristics were automatically acquired, leading to the efficiency as a function of irradiance, cell temperature and air mass. The data were used to develop a new efficiency model to calculate the efficiency under all relevant operating conditions. The model contains six parameters. They were determined by applying non-linear fitting techniques. Applying mathematical transformations reported on earlier, measurements and the efficiency model can be compared and validated in two-dimensional representations. The module shows a modest efficiency behavior over the irradiance range (bad part-load efficiency). The STC efficiency (referred to the active cell area) was found to be 12.6%, corresponding to an STC module output power of 45.5 W (manufacturer: 50 W). An efficiency maximum of 12.7% was found at 832 W/m2. The efficiency linearly decreases with temperature. Its temperature coefficient was found to be –0.0507 percentage points/°C. Regarding the impact of air mass, the efficiency exhibits a maximum value of 12.7% at an air mass of 3.77. The module shows fairly good red light sensitivity in the late afternoon.