SolarTurbineGroup

[chrisser]

I came across this site and found it pretty interesting. I've never had a huge interest in solar, but this really got me thinking...

http://www.solarturbinegroup.org/how-it-works.html

Unfortunately, according to their FAQ, they won't release plans or details. However, there's enough info there that one could probably put something together. Supposedly, they build it with common (mostly automotive) materials.

From what I saw, they build some basic parabolic modules using aluminum sheet as the reflector. They focus light on what appears to be basoc black iron pipe, which is housed within glass tubes (possibly with the air evacuated). The iron pipes have antifreeze in them which is pumped to a heat exchanger.

The heat is transferred to a heat engine, (which I suspect is composed of A/C parts, although it contains a turbine which may be a turbocharger from a car) and runs on some sort of refigerant. This drives either a pump or an alternator. A byproduct of the condensing process is hot water.

Their installation is in Lesotho, which is in South Africa, about the same latitude as southern Australia. There are pics of at least some snow, which leads me to believe it is operating with some success at around the same climate of some of the southern U.S. states.

The pics on the site manage to show a lot of the details, although there are still some aspects I'm fuzzy on. It does seem to track throughout the day by means of a cable actuating system, and they alter the angle of the collectors based on the season. They avoid any use of electronics, as its designed for the third world.


Curious if anyone knows any sites that would give calculations of how much sun can be focused by a parabola at a given latitude, season, cloudiness. Wondering if one of these could work in the winter farther north with larger collectors, possibly with glass faces (to keep the snow off). I've noticed that sunny days can make the car quite warm even here in Cleveland, even when the outside temps are freezing.


Also been thinking about the closed heat engine system. I wonder if its possible to tweak the boiling point/condensing point of the refrigerant by varying the system charge - if you could move the point at which the "steam" is created, then you could take advantage of other heat sources, such as less sun (or the warmer ground) in the winter when its freezing outside, or waste heat from a diesel or propane generator.


What are your thoughts?

[JAK]

I like the idea of combining systems, like space heating, hot water heating, refrigeration, and power generation, especially if you can design and build the system yourself. It doesn't neccessarily lend itself to mass market, but if you are doing something DIY there may be opportunities depending on your individual needs and climate. As thinner film technology improves it might be hard to beat conventional solar panels for power generation, but for DIY projects a solar/wood steam or solar/wood stirling system might be competitive, especially for combined heat and power. Fun to play with if nothing else, and affordable if you keep things very small.

[chrisser]

I agree. I also believe the best way to approach self-sufficiency is to have a certain degree of systems overlap.

I see this device as having a lot of flexibility. Sort of like a standby generator, that runs for free the rest of the time to supplement your power needs.

I also think this heat engine could have some really great uses as part of a systems approach. Maybe one of your collectors is a coil in your wood stove, or even a burner attached to your propane tank. You wouldn't want to use it that way all the time, but if the sun isn't shining, you've got options without massive system reconfiguration.

Ditto with electricity - maybe you have PV, and a standby generator, but you could also be creating it (perhaps inefficiently, but its there) by burning extra wood in the stove and activating that circuit.

After the capital investment, this thing doesn't need any fuel, and the initial investment appears to be pretty reasonable.

[JAK]

I'm going to have to study that one a bit closer to see what's going on.

This is something I want to build as a hot water heater.

http://www.aprovecho.org/web-content/media/vita/vita.html

Maybe solar heated in summer, and wood fired in summer, and a little of both in between. Still thinking about how it might be used for power generation also. I don't want to go to high power steam, but in winter we have cold enough temperatures to get pretty good efficiency with an atmospheric steam engine. Thinking maybe solar panels in summer, and solar panels supplemented with some steam power in winter, for combined heat and power.

Very low power though. I figure if I only get the life cycle cost down to the equivalent of $0.50 per kwh, it will still only be $60 per month if I can keep my electrical needs down to 4 kwh per day.

In winter, if I get only 10% efficiency on electricity, while getting 30% on hot water, and 30% on heat, and the other 30% up the chimney, then I can get my 4 kwh of electricity plus 50 (US) gallons of hot water, plus another 40,000 BTU of space heat on about 20 pounds of wood each day. On the very coldest days I could run a wood stove separate from this system, or run this system 2 or 3 times to boost the batteries up and use the extra power and hot water for one thing or another, heat if nothing else.

[davidlj]

Build it in the USA first but again the world bank is in on this one.