Hi Ray
I was thinking about going only one way due to where I live. A combination could also be a good way to go and if you live in the States maybe the only way. In the Philippines there are two seasons, rainy and dry with temperature about the same and I can get scrap wood almost anywhere at anytime, if its used in a desert then solar would be it. I used to teach solar energy and I'm familiar with most of the devices presented. The problem with all of them is that they must track the sun to be useful. Compound parabolic concentrators can be used for a longer time with the time depending on the temperature that is required. One of these can be used all day if the maximum temperature is only about double what you can get with the thing just sitting out in the Sun. The Stefan-Boltzmann is M=esT^4 where M is the called the emissivity (the radiative flux), e is a dimensionless number between zero and unity, s is Stefan's constant and is equal to 5.67 X 10^-8 Watts/(square meter times Kelvin to the fourth power). The Sun puts out 1370 W/m^2 extraterrestrial just outside the Earth's atmosphere and about 1,000 W/m^2 on the surface of the Earth. If we let e equal to unity, T is equal to 364 Kelvin or 91 degrees Celsius. This is less than the 130 0C required to boil the water. If we double this we could get up to 160 0C which is enough assuming the optical efficiency is 100%, but it isn't. I'm working on something that doesn't need tracking, but it isn't ready yet and it's just a concept. Ken Gotberg --- On Sun, 8/1/10, Ray Menke <[email protected]> wrote: From: Ray Menke <[email protected]> Subject: Re: [Gasification] Can use some help with stoves To: "Discussion of biomass pyrolysis and gasification" <[email protected]> Date: Sunday, August 1, 2010, 9:06 AM Hello, Are you familiar with the work done by Alex Belonio? A google search on "belonio rice husk stove" will yield 3700 hits. He is also in the Philippines, and his work involves the utilization of Rice Husks (a small particle fuel) for producing a gas than can be burned on top of a stove, or piped to a remote burner. This burner could be located near a solar concentrator. Regarding the solar concentrator, I might add that I have recently completed an array consisting of 54 twelve inch mirrors (6 sq. meters) focused on a target (oven). I also have built (or purchased) and use wood gas cook stoves almost every day, and utilize a passive solar hot water heater for all our hot water requirements, except in those dreary overcast winter days. Here is a site that will show you the Surface meteorology and Solar Energy data for your location: http://eosweb.larc.nasa.gov/cgi-bin/sse/sse.cgi Check carefully to see how many hours of clear sky you might expect each day. If the weather service does a local forecast, they may also predict the percentage of sky cover for each day. This is valuable information. It is sort of a hassle to attempt to manually adjust the tracking of a concentrator if the sun is behind a cloud. ;) It might be possible to use a passive solar collector to pre-heat the liquids you want to boil, thus reducing the amount of additional energy required. For solar concentrators, check out http://www.solarfire.org/, and the Scheffler designs at http://www.solare-bruecke.org/ If you have enough direct sunlight, either of these can produce steam. Some solar ovens use a backup source of heat, so a gasifier could do that. The Villager Sun Oven is one that offers propane backup. http://solarcooking.wikia.com/wiki/Villager Last year we suffered through a severe drought, with about 50 days of over 100 degree temps, so I built a solar concentrator. This year, we might break 100 degrees F today for the first time. Yesterday was 2% cloud cover, and we loaded the solar oven with everything we could find to cook. This afternoon, we will roast a chicken. (We often have clouds every morning, and two tropical storms that brought weeks of overcast days.) Meanwhile, I continue to prepare the fuel stock for my stoves, knowing that eventually a tropical storm or hurricane will keep my mirrors in the shade. If possible, please download Alex Belonio's Rice Husk Gas Stove Handbook. It is a 3.6 MB file of 155 pages with photographs. Especially if you can find free rice husks. I have a series of articles in the blogs on the Solarfire.org site, under the English section. (The one about building a Helios in S. Texas.) There is a firm in India offering to sell some larger concentrators as well as steam engines. (There is a link on the solarfire.org site.) Are you working on air conditioning or dehumidification equipment or ? Hope this info is of some use. On Sun, Aug 1, 2010 at 12:15 AM, Ken Gotberg <[email protected]> wrote: > Philippines... > the salt stays behind and the water is re-condensed and saved. I'm > using CaCl2 as the deliquescent salt and everything works > fine on getting water out of the air. It's the boiling > see them are: 1. rocket stove, 2. gasification stove, 3. charcoal > stove, 4. solar thermal concentrator, etc. The 130 0C is > In the Philippines there is a lot of biomass lying around and the > rocket or gasification stoves would probably be the best way to go. > fuel in a shape for use in the rocket stove or grind for a > gasification stove? I would be happy to hear from anyone who knows > about this > Solar thermal concentrators would be the only way to go in a > desert, but getting fairly high temperatures is the problem. We may > be able to use a compound parabolic concentrator (CPC) reflector that > is orientated few times a day coupled with a receiver that is made > out of an evacuated glass tubes or spheres that are sputtered with > copper on the inside followed by stainless steel followed by aluminum > nitrite on the outside. Or we could go with Fresnel lenses covering > a sphere with no tracking required that are segmented with entidue > requiring a wide angle lens coupled with a separated converging lens > that is focused at the center of the sphere. Active tracking wouldn’t > be the way to go in my opinion, but maybe I’m wrong. -- Ray Menke _______________________________________________ Gasification mailing list [email protected] http://listserv.repp.org/mailman/listinfo/gasification_listserv.repp.org http://gasifiers.bioenergylists.org http://info.bioenergylists.org _______________________________________________ Gasification mailing list [email protected] http://listserv.repp.org/mailman/listinfo/gasification_listserv.repp.org http://gasifiers.bioenergylists.org http://info.bioenergylists.org
