Solar cooker/water sterilizer, new developments

[spinningmagnets]

These have been around for a while, but I have noticed a couple new developments that are very beneficial. I thought a few readers over the past year may have not seen them yet. Most can be built cheaply and easily. But PLEASE, exercise extreme caution when asembling any type of solar concentrator. A split-second mis-step can cause a serious burn and/or permanent blindness.

Concerning third-world survival, nothing is more immediately neccessary than clean water. Cholera, dysentery, a wide variety of parasites, etc, plague these countries through poor water quality. Also, deforestation is increasing the soil erosion, loss of topsoil, and desert growth in these areas. The deforestation is sped by rural villages chopping down trees to burn for cooking. A conversion to solar cooking can ease the stress on forests.

The recent earthquake/tsunami troubles in Japan show that even a modern country can make use of improvised solar water purification in disaster-relief areas. Multi-faceted flat reflectors and single-curve concentrators can be easily made from gathered junk. Here are many examples so that we benefit from the research of many previous experimenters (scroll down to see pics):

Wikipedia "solar cooker"
http://en.wikipedia.org/wiki/Solar_Cooker

Solar Cookers International wiki
http://solarcooking.wikia.com/wiki/Category:Solar_cooker_designs

I would recommend using a cast-iron "Dutch Oven". If you get the style that has a concave lid (rather than a dome) it can hold coals on top when using it on a camp-fire (broken wood is usually easy to find after a disaster). They are virtually unbreakable, and should last a lifetime. Since the heat-profile of a solar cooker and a Dutch oven are the same, here's one of many websites with over 1,000 recipes for campfire Dutch oven cooking: http://www.justdutchovenrecipes.com/index.html

The two new things I recently saw are the "Phaeton Array", and also a double-trough concentrator using a single curve (rather than a bowl-shape) on each reflector. Dish-style concentrators are not very difficult to make, however, if you have chosen a double-concentrator style to build, it is easier to make the single-curve reflectors.

The Phaeton is mounted on wheels so it can be rotated to follow the sun easily, and also its made of many flat facets on the main reflector, which focuses onto a low reflector that directs the heat upwards to the bottom of the pan.

For the single-curve reflectors, there is no need to use math to derive a "perfect" parabola (dish) shape. Instead, you tighten cords to slowly bend the shape of the single-curve until the resulting focused light is the size and shape you desire. Mylar peel-and-stick film from an automotive customizing shop (or ordered online) can be applied to something as simple as thin plywood.

Due to the high heat (a good thing!) the smaller secondary reflector may need to be made from polished sheet-metal. It may also be useful to focus the heat onto the bottom of a steel plate for safety and ease of cooking (such as in the Phaeton configuration).

http://solarcooking.wikia.com/wiki/Parabolic_solar_reflectors

 

[spinningmagnets]

Heres a two-minute video on You-Tube about using a satellite mini-dish as the parabolic reflector (covered by a mylar reflective sheet). Very good results from a surprisingly small concentrator. Running a tube from the lid through an air-cooled coil down into a collection pot would make this a water-distiller. It just doesn't get much simpler than this, eh? (Thanks to Scott B. in Michigan for this link!)

http://www.youtube.com/watch?v=U220eTxHmvw

 

[fechter]

I love the recycled satellite dish. I have one on the roof that's unused. I was going to turn it into a parabolic microphone.

I made a cooker out of a surplus reflector from a surgical light. It was polished aluminum and about 3 feet in diameter. That much sun can boil a liter of water in a few minutes. If found it a little tricky to aim, so a good stand is important. I'd like to figure out an easy way to turn it into electricity, but PV panels are just hard to beat (except for the cost).

 

[spinningmagnets]

I'd like to figure out an easy way to turn it into electricity, but PV panels are just hard to beat

I have a long list of alternatives that are useable when the preferred resource is unavailable. I can't make a solar-PV panel, but I can use junk to make a solar heat Organic-Rankine-Cycle (ORC) which can be easily understood by calling it freon-steam. Freon, butane and propane boil at much lower temps than water, so a solar-powered ORC "steam" engine works well even just using an air-fan for the condenser.

If a device can spin a shaft with some force, it can spin a generator to charge a battery. Some types of motors can be converted to generate electricity.

Given a choice, I would prefer the off-the-shelf solution of several PV arrays charging a battery bank. My most basic electrical need is for lights at night and music, along with an electric bike! If the cost of electricity jumps up a lot, or there are severe shortages in the grid due to a local disaster, plan on the conventional solutions being quickly sold-out.

I am reminded of the recent earthquake/Tsunami in Japan, hurricane Andrew in Florida, and extensive tornado damage to Chapman Kansas.

edit: April 2011 tornado in Alabama, worst in US history.

 

[texaspyro]

I'm rather surprised that it works so well... I'm too smart to have ever wasted my time building something can't possibly work Now I need to sneak up on my neighbor's roof with a hacksaw.

 

[amberwolf]

I keep wanting to collect all the old 15-foot satellite dishes I see rusting away in backyards now and then, but I can't ever get hold of the owners. Either they won't answer the door or they won't talk to me or aren't home. They haven't called back when I've left offers on notes on the door/etc., either.

At one point I used google maps in satellite mode, just looking for round things in yards and then biking around to see if they were still there if they looked enough like dishes; usually they were still there but again, no contact results.

Those big dishes would make some nice reflectors, and I have a big backyard.

Put them up just above head level and they'd be nice shade for the yard, too.

 

[Harold in CR]

Have you put a wanted ad in Craigslist ??

I also noticed there is a "Freecycle" page on the Internet, and, you can put wanted ads there, also.

 

[TylerDurden]

Ja, there are still large dishes for the taking. If you can find a DISH installer or such, they can tell you who still has the big dishes and want them removed.

That DaS engine system is still intriguing. It's on my list of stuff to try.

 

[scotticeberg]

I've been using a Global Sunoven for about a year. It works especially great during the summer when it makes little sense to turn on the oven and unnecessarily burden the air conditioning. It is made in Illinois as well. I initially purchased it while living in San Diego, but it still works well on any clear day in Michigan.