Energy production Solar water heating

a laundromat in california panels on roof providing hot washing water.

the amount of heat delivered solar water heating system depends on amount of heat delivered sun @ particular place (insolation). in tropics insolation can relatively high, e.g. 7 kwh/m2 per day, versus e.g., 3.2 kwh/m2 per day in temperate areas. @ same latitude average insolation can vary great deal location location due differences in local weather patterns , amount of overcast. calculators available estimating insolation @ site.

below table gives rough indication of specifications , energy expected solar water heating system involving 2 m of absorber area of collector, demonstrating 2 evacuated tube , 3 flat plate solar water heating systems. certification information or figures calculated data used. bottom 2 rows give estimates daily energy production (kwh/day) tropical , temperate scenario. these estimates heating water 50 °c above ambient temperature.

with solar water heating systems, energy output scales linearly collector surface area.

the figures similar between above collectors, yielding 4 kwh/day in temperate climate , 8 kwh/day in tropical climate when using collector 2 m absorber. in temperate scenario sufficient heat 200 litres of water 17 °c. in tropical scenario equivalent heating 33 °c. many thermosiphon systems have comparable energy output equivalent active systems. efficiency of evacuated tube collectors lower flat plate collectors because absorbers narrower tubes , tubes have space between them, resulting in larger percentage of inactive overall collector area. methods of comparison calculate efficiency of evacuated tube collectors based on actual absorber area , not on space occupied has been done in above table. efficiency reduced @ higher temperatures.