Abstract
AbstractIncreasing the number of subcells in a multijunction or “spectrum splitting” photovoltaic improves efficiency under the standard AM1.5D design spectrum, but it can lower efficiency under spectra that differ from the standard if the subcells are connected electrically in series. Using atmospheric data and the SMARTS multiple scattering and absorption model, we simulated sunny day spectra over 1 year for five locations in the United States and determined the annual energy production of spectrum splitting ensembles with 2–20 subcells connected electrically in series or independently. While electrically independent subcells have a small efficiency advantage over series‐connected ensembles under the AM1.5D design spectrum, they have a pronounced energy production advantage under realistic spectra over 1 year. Simulated energy production increased with subcell number for the electrically independent ensembles, but it peaked at 8–10 subcells for those connected in series. Electrically independent ensembles with 20 subcells produce up to 27% more energy annually than the series‐connected 20‐subcell ensemble. This energy production advantage persists when clouds are accounted for.
Highlights
The most efficient photovoltaic devices under the AM1.5 spectrum use the design concept of dividing the solar spectrum among multiple photovoltaic subcells, or “spectrum splitting” to improve performance beyond the capabilities of single junction designs [1,2,3]
This paper extends the analysis to large numbers of subcells and locations that exhibit wider variation in atmospheric conditions, which are important areas of inquiry as spectrum splitting photovoltaics become increasingly ambitious in terms of subcell number and deployment scope
The electrically independent ensembles have a significant energy production advantage that increases with the number of subcells
Summary
The most efficient photovoltaic devices under the AM1.5 spectrum use the design concept of dividing the solar spectrum among multiple photovoltaic subcells, or “spectrum splitting” to improve performance beyond the capabilities of single junction designs [1,2,3]. While efficiency measurements under the AM1.5 spectrum provide an essential means of standardized comparison between different photovoltaic technologies, the true product of photovoltaics is cumulative energy production over days and months with conditions that can vary widely from the standard test. The photovoltaics community has an increasing interest in predicting both the standard test efficiency and the energy production behavior of different photovoltaic technologies, in particular identifying the effects of design decisions on energy production [6,7,8]. A. Atwater splitting designs with 2–20 subcells that are either connected electrically in series or are electrically independent of one another
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