solar dryer

File:Direct Solar dryder.svg

Direct solar dryers expose the substance to be dehydrated to direct sunlight. Historically, food and clothing was dried in the sun by using lines, or laying the items on rocks or on top of tents.{{Cite book|author1=Heinz, Gunter |author2=Hautzinger, Peter |name-list-style=amp |year=2007 |chapter=Meat drying |title=Meat processing technology for small- to medium-scale producers |series=RAP Publication 2007/20 |location=Bangkok, Thailand |publisher=Regional Office for Asia and the Pacific, Food and Agriculture Organization of the United Nations |isbn=978-974-7946-99-4 |url=http://www.fao.org/docrep/010/ai407e/ai407e18.htm |archive-url=https://web.archive.org/web/20100523163235/http://www.fao.org/docrep/010/ai407e/AI407E18.htm |archive-date=23 May 2010 |url-status=live}} In Mongolia cheese and meat are still traditionally dried using the top of the ger (tent) as a solar dryer.{{Cite web|author=Oyunbayar, N. |title=Mongolian Food: Meat, milk and Mongolia |publisher=Mongoluls.Net |url=http://www.mongoluls.net/ger/meatmilk.shtml |archive-url=https://web.archive.org/web/20050405194906/http://mongoluls.net/ger/meatmilk.shtml |archive-date=5 April 2005 |url-status=live}} In these systems the solar drying is assisted by the movement of the air (wind) that removes the more saturated air away from the items being dried. More recently, complex drying racks{{Cite magazine |year=1999 |author=Shaffer, Marcella |title=Solar Food Drying |magazine=Backwoods Home Magazine |issue=58 |url=http://www.backwoodshome.com/articles/shaffer58.html |archive-url=https://web.archive.org/web/20000816011755/http://www.backwoodshome.com/articles/shaffer58.html |archive-date=16 August 2000 |url-status=live}} and solar tents{{Cite book|author1=Trim, D. S. |author2=Curran, C. A. |name-list-style=amp |year=1983 |chapter=Solar dryers |title=Comparative Study of Solar and Sun Drying of Fish in Ecuator |location=London |publisher=Tropical Products Institute |isbn=978-0-85954-158-9 |url=http://www.nzdl.org/gsdlmod?e=d-00000-00---off-0cdl--00-0----0-10-0---0---0direct-10---4-------0-1l--11-en-50---20-about---00-0-1-00-0--4----0-0-11-10-0utfZz-8-00&cl=CL1.95&d=HASH014cec3765e4a2d742eeb5a8.6.2>=1 |archive-url=https://web.archive.org/web/20150902223513/http://www.nzdl.org/gsdlmod?e=d-00000-00---off-0cdl--00-0----0-10-0---0---0direct-10---4-------0-1l--11-en-50---20-about---00-0-1-00-0--4----0-0-11-10-0utfZz-8-00&cl=CL1.95&d=HASH014cec3765e4a2d742eeb5a8.6.2>=1 |archive-date=2 September 2015 |url-status=live }} were constructed as solar dryers.

One modern type of solar dryer has a black absorbing surface which collects the light and converts it to heat; the substance to be dried is placed directly on this surface. These driers may have enclosures, glass covers and/or vents in order to increase efficiency.{{Cite magazine|author=Fodor, Eben |year=2006 |title=Build a Solar Food Dehydrator |magazine=Mother Earth News |volume=2006 |issue=August/September |pages=66–70 |url=http://www.solarfooddryer.com/Info/Mother_Earth_News_Article.pdf |archive-url=https://web.archive.org/web/20151129044254/http://www.solarfooddryer.com/Info/Mother_Earth_News_Article.pdf |archive-date=29 November 2015 |url-status=live}}

In indirect solar dryers, the black surface heats incoming air rather than directly heating the substance to be dried. This heated air is then passed over the substance to be dried and exits upwards often through a chimney, taking moisture released from the substance with it. They can be very simple, just a tilted cold frame with black cloth{{Cite journal|author=Robishaw, Sue |year=1999 |title=Drying Food with the Sun |journal=Countryside & Small Stock Journal |volume=1999 |issue=July/August |url=http://www.countrysidemag.com/83-4-sue-robishaw/ |archive-url=https://web.archive.org/web/20150902232739/http://www.countrysidemag.com/83-4-sue-robishaw/ |archive-date=2 September 2015 |url-status=live}} to an insulated brick building with active ventilation and a back-up heating system.{{Cite web|author1=Weiss, Werner |author2=Buchinger, Josef |name-list-style=amp |year=2001 |title=Solar Drying |publisher=Austrian Development Cooperation and Institute for Sustainable Technologies (AEE INTEC) |url=http://www.aee-intec.at/0uploads/dateien553.pdf |archive-url=https://web.archive.org/web/20120526151427/http://www.aee-intec.at/0uploads/dateien553.pdf |archive-date=26 May 2012 |url-status=live}} One of the advantages of the indirect system is that it is easier to protect the food, or other substance, from contamination whether wind-blown or by birds, insects, or animals. Also, direct sun can chemically alter some foods making them less appetizing.

Solar drying is mostly carried out between 50-70 degree Celsius. Solar dryers such as Vyom and many other models now use polycarbonate sheets or UV preventive glass so that UV rays of the sun do not penetrate the food which leads to degradation of dried food. Solar dryers not only make the drying faster, it also prevents dust, pathogens, bird droppings, and interference of external agents that affect the quality of the food. Food items such as fruits, vegetables, spices and other items once dried in solar can be stored for longer period of time.{{fact|date=July 2022}}

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• {{Cite web|year=2014 |title=Links to articles, photos, and other sites related to solar food drying |publisher=SunWorks Technologies LLC |url=http://www.solarfooddryer.com/Info/Resources_links.htm |archive-url=https://web.archive.org/web/20150914182655/http://www.solarfooddryer.com/Info/Resources_links.htm |archive-date=14 September 2015 |url-status=live}}

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Category:Dryers

Category:Solar energy