A novel method of current matching the ideal series-connected subcells tandem solar cell system maintaining optimal the conversion efficiency

Abstract

A novel method is explored that maintains optimal the overall conversion efficiency of series-connected subcells tandem solar cell system ( same as the theoretical overall conversion efficiency ( ƞ_opt ) of the stacks of independently-operated optimized subcells tandem solar cell system ). Series-connected optimized-subcells tandem solar cell systems suffering of un-matching ( unequal ) their subcells currents and as a result their conversion efficiencies drop down the optimal ( ƞ_opt ) ones because the output current of the series-tandem solar cell system is limited to the smallest of the current produced by any of the individual subcells. If this is the case, the currents through each of the subcells are constrained to have the same value. This novel method, we so called by “ The Averaging Method “, solves this problem of un-matching the current through the series-connected subcells by; averaging the sum ( dividing the sum by the number of subcells ) of all the maximum currents of individual independently-operated subcells, next; applying the resulting average maximum current ( as a matching maximum current ) to search for what several candidate subcells ( other than the optimized ones ) such that this matching maximum current is satisfied between each of these candidate subcells. It is proved that the sum of, maximum currents, power, and overall conversion efficiency, of the     independently-operated subcells versus those referred to this approach of series-connected candidate subcells, tandem solar cell systems, are equal. Applying this approach method requires no extra than a single; controller, load, as compared to the independently-operated subcells tandem solar system where necessarily is the provision of a special; controller, load, for every subcell utilized; this is simply because now the subcells, both, are current-matched, and in addition, the resulting matching current being maintained equal regardless of solar radiation variations. Calculations are carried under applying solar radiation spectrum of air mass zero ( AM0 ) at several solar intensities and temperatures, for a tandem solar cell systems their subcells ranged, from two up to twelve subcells.