Cosine factor in low-potential solar installations

Instantaneous and average cosine factors of low-potential solar installations (LPSIs), i.e., fixed and single-axis tracking collectors, and solar batteries, are investigated. It is confirmed that in the case of year-round operation the optimum tilt to the horizon of a fixed LPSI is close to the site’s latitude. It is shown that for a fixed LPSI in the case of permissible variations of the solar flux on a receiver at ±20%, the daily LPSI operation time for Uzbekistan’s latitudes is about eight hours. It is also shown that depending on the season of the year the single-axis tracking increases the average cosine factor by 6–14% if the LPSI is active six hours a day and by 14–30% if it is active nine hours a day. The instantaneous cosine factor increase using tracking is more significant and is 25–50% after 3:00 p.m. and 50–100% after 4:00 p.m., depending on the season. The effect of discrete additional turns of a single-axis tracking LPSI manifests itself for the average cosine factor only in the winter time and ranges from 11 to 15%.

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