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Also: Parabolictrough.org
Also: Heliostat.org
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"" =====News===== October 2009: We are now working with suppliers and building engineers to compile a ready to go and easy method to construct a solar bowl. =====Donate===== [[http://www.sunreign.com/info/ProjectDonate What do we do with your money?]] [[SolarBowlDevelopment]] =====Introduction===== The Solar Bowl is a solar concentrator design that uses a spherical dish. Most common dish type solar concetrators use a parabolic shape, which creates a single focus point. THe parabolic mirror however has to be pointed straight at the light source, which requires tracking of the entire dish. A sperical mirror has a different image, basically a central line (although much of the light ends up at 1/2 radius. ""
"" =====Focus Line===== The light focusses on a central line. Because a spherical bowl is a lot like a parabolic bowl the light concentrates most at half radius. The intensity profile is shown here. One of the reasons why solar bowls are less efficient is because of heat losses due to the larger cilindrical reciever area. """" =====Efficiency===== The shape of the mirror with respect to the sun always remains the same. only the effective apperture size changes. The mirror can remain fixed and the focal line automatically tracked. The effective apperture of the mirror changes following a sinus wave during the day, so this design is somewhat less efficient than a parabolic tracking mirror. The cost of construction however is considerably less. Below half a days output curve of a solar bowl constructed in Auroville, India. The Auroville Bowl is made using silvered glass mirrors and produces 450 Kg steam per day, equating to 261 Kwh energy. """" The temperature of the focus is important because it determines how much energy can be extracted by f.i. a steam turbine. Solar Bowls can generate steam at 300-500 degrees celcius. The total efficiency of a Solar Bowl can be between 38 and 43%. =====Comparative cost===== The cost per square meter of different systems gives a rough indication of the wisdom of one alternative over another. The insolation per square meter is a given for any location, making it easy to convert the number into capital cost per Kwh/year. """" Data from Solar Thermal Power for India by Dr. Shireesh B. Kedare, Solar Bowl data corrected by Auroville. The cost shown are for the mirror bowl, which is the principal cost element. When water is used as a medium maintenace is low, but this of course depends on the way the heat is used downstream. =====Auroville cost===== """" The Auroville mirror was originally build to use [[http://www.merchantos.com pos systems]] thermal oil and cost included a diesel backup heat source. Construction material was ferrocement (thin cement with light rebar) and doubled as a roof. Diameter is 15 meter giving an apperture of 176 square meter. Below a calculation of per Kwh cost when including a 5% loan payed off in full in 5 years. It is used to provide cooking heat for about 300 people daily, which actually underuses the capacity (due to the cooking schedule, namely before 11 am). Mirror bowl construction 21,000 Euro Reciever construction 1,400 Euro Miscellaneous 2,000 Euro Total cost 24,400 Euro Annual Maintenance 10% 6,738 Euro Cost per KWh 0,07 Euro =====Building a Solar Bowl===== We provide components, consulting and assistence for people wanting to construct a Solar Bowl. Please become a member of [[buildingcsp.ning.com buildingcsp]] to recieve more information or contact us [[info@sunreign.com here]] with your questions. ====References==== 1) [[http://en.wikipedia.org/wiki/Solar_bowl Solar Bowl:Wikipedia definition]] - The Solar Bowl is a type of solar energy collector. 2) [[http://solar.calfinder.com/blog/going/the-solar-bowl-solar-vs-electric-water-heaters/ Solar Bowl: Solar vs. Electric Water Heaters]] - The rivalry between solar hot water systems and conventional electric systems is an old one. Although the very term ‘conventional’ when referring to electric water heaters is a bit of a misnomer, considering that the sun far preceded electricity in the history of producing hot water. But let us not get bogged down in semantics.