Load matching and performance of a non-tracking stand-alone photovoltaic generator in Sana'a University

Abstract

This work provides an economical combination of the number of modules composing a non-tracking solar electric generator, the storage battery system and the load requirements in Sana'a University. The load is composed of solar radiation recording equipment, lighting of the solar laboratory, an infra-red spectrophotometer and the computer system. The load requires 142 Ah day −1 . The power needs for the load are calculated as 1249 W at 25°C, which corresponds to 1561 W at 75°C internal cell temperature. An average of 4 years of global solar radiation measurements in Sana'a University is presented. Average daily global solar radiation of 21·8 MJ m −2 on an inclined surface orientated 15·5°N to the horizontal proves high annual insolation in Sana'a. The solar array is composed of four panels comprising 1680 single crystal silicon solar cells of 100 mm diameter arranged in 48 modules. The active solar cell efficiency η is calculated to be 10·7%, as based on the active cell area of the panel. Taking the solar cell internal temperature into consideration η′ becomes 12·1%. Barker and Power's method for predicting an array output has been investigated and is in good agreement with field measurements. Array output of 1594 W ± 11% at 25°C internal cell temperature is obtained. The storage battery system is composed of 28 lead-calcium batteries of 12 V and 105 Ah. The batteries are distributed in seven rows connected in parallel. Each row is constituted of four batteries connected in series. The batteries are almost fully charged throughout the year, except in August. The charging in that month is only 73%, which proved to be of no great harm to the batteries. Performance over a 1-year period is presented in detail. Reliable photovoltaic power has been generated over a period of 2 1 2 years. This research work will be extended to cover the power needs of one of the villages near Sana'a.