Solar Generator Performance with Load Matching to Water Electrolysis Longterm Averages and Range of Instantaneous Efficiencies

Summary

The efficiency of producing hydrogen by solar energy conversion via solar cells and water electrolysis is determined by the performance of the solar cells, the efficiency of the electrolyser and the quality of load matching. The strong variations of solar generator characteristics in the varying conditions of Central European climate necessitate longterm monitoring of system performance. A solar generator is directly wired to an electronic simulation of an advanced water electrolyser. System performance is monitored from January 15 to July 7, 1980. Instantaneous generator efficiencies are capricious, but average generator efficiencies at specified solar irradiance and ambient temperature are well behaved. Load matching losses amount to only 8.9 % of the solar generators MPP output. Hydrogen production is calculated from the current through the load assuming 100 % current efficiency of the water electrolysis. Starting from 10.0 % generator efficiency an overall energetic efficiency of 8.0 % is achieved for hydrogen production. The exergetic efficiency is 9.4 %.