[article] Build a solar generator

[Sponge]

I got this idea while on vacation, but someone else wrote a nice article about it already:

http://www.technologyreview.com/read_article.aspx?id=17169&ch=biztech

It's about the usage of a mirror to heat up water.. generating steam which turns a generator. Very similar to the method used in power plants.

I think it might be worth a try for all you guys living in hot sunny areas .

[Slingshot]

I think it's interesting that the system actually uses an automobile power-steering pump (in reverse, I assume) as a steam turbine.

For anyone familiar with the internals of these, what is your opinion?  Would a ps pump, operating as a turbine, be capable of useful power and efficiency?  And would it rust out in short order?  After all, it's normally intended to be filled with oil, not hot steam.

[Countryboy]

Reread the article.  They are using a refrigerant to produce gasses to drive the turbine - not steam.  This should remove problems of stuff rusting out.  They do use groundwater as a coolant though - but you could always use a closed system with something other than water.

Did you notice that they said 15 square meters?  That's almost 160 square feet to get 1 Kw of electric.  Due to the space requirements, this isn't going to be very practical for urban environments.

They said this cost a couple thousand dollars - about half of what 1 Kw of solar panels would cost.

I think they would be further ahead to use the parabolic mirror solar collector focused on a solar panel, than trying to generate electric via steam turbine.

As a side note, it might be worthwhile to study this for an application for a refrigerator or freezer in remote locations.  This absords the heat from the sun - with a refrigerator, we want it to remove the heat from the inside of the fridge/freezer.  The liquification and gasification processes of the refrigerant would be the same in both applications.

[kitno455]

there are several types of PS pump out there (vane, slipper, ring and sun, two gear), but almost all of them have cast-iron or mild steel for the moving parts.

the vane type is the most common, and they are often entirely cast iron internally.

these things wont last long with water vapor passing thru them. many of them rely on centrifugal psuedoforce to keep the vanes in contact with the stator (much like a commercial vaccuum pump). those units will stop quite quickly once the vanes seize in the contracted position. besides the fact that the nose bearing has an external seal, but not an internal one, i dont think its a good long-term idea.

could the working fluid be something other than water?

allan

[powerbuoy]

I would say the one thing he has going for him is the use of common readily available materials. But, his system seems to be pretty complex and loaded with inefficiencies. He'll also need perfect sunny days and a tracking device to get the most out of it. It'll be a one axis tracker since he's not using a bowl dish.

I would have tried this with a stirling engine. Way less moving parts. The drawback to the stirling is that it's not an off the shelf item and involves some design work.

A very good book on the stirling was written by James Senft. ISBN 0-9652455-0-0

Powerbuoy

[Vince]

Low Cost Solar Furnace (Pics):

http://www.motherearthnews.com/gallery/4361/0/

Low Cost Solar Furnace Plans (Part 1):

http://www.motherearthnews.com/Alternative_Energy/1978_July_August/At_Last__A_Low_Cost_Solar_Furnace_

Low Cost Solar Furnace Plans (Part 2):

http://www.motherearthnews.com/DIY/1979_March_April/Mother_s_Solar_Furnace_Frame

Low Cost Solar Furnace Plans (Part 3):

http://www.motherearthnews.com/library/1979_May_June/Plumbing_Up_Mother_s_Solar_Furnace

(I couldn't utilize the hotlinks, as the 'Part 2' address ends with an underline "_", which does not display, and therefore goes to the wrong address. Oh well.)

[Goose]

Powerbuoy,

There is a Co. that is building right now with that technology.

http://www.stirlingenergy.com/

It would be cool if somebody would come up with a design for a stirling and sell the plans to make it, with around 2-5 KW's.  Then it would be easy somewhat easier to make a small system like this.

Wish we knew more about what these students are doing, and more about their design. with the auto parts.  

[Ungrounded Lightning Rod]

They said there were two working fluids:

 - Motor oil - for the collector (pumped by one power-steering pump).

 - "Refrigerant" - for the "steam" turbine (the other power steering pump).

I'm presuming the "refrigerant" is automotive air conditioning refrigerant, complete with the low vapor pressure oil used to lubricate power steering compressors.

Which brings up a question:  Why didn't they use an air conditioning compressor for the turbine?  It's designed for the working fluid and pressures in question and for extremely low leakage.  Is it just an issue with what happens if it gets a little liquid in it, or is there some other problem, such as incorrect valve arrangements?  Or perhaps just cost/availability in the third world?

[Ungrounded Lightning Rod]

A trough only needs tracking adjustment monthly or less.

[kitno455]

PS pump likely more common than AC in africa.

most PS pumps are going to be rotary vane type, with ports in the stator or endplates for intake/exhaust. something like 10 to 15 chambers, very even power production, no valves, no mods.

a piston type AC compressor would need some valve work, at bare minimum flipping over the reed holder, unless its machined into the case, then you have to do a bit more work. on some models the reeds cant be reached without tearing the thing wide open. though i will say that one of the variable swashplate units would give good low speed startup.

a scroll compressor might be a better choice? the seals in it are really designed for highpressure gas, unlike the ps pump, but it still has some of the ports not valve advantages.

alan

[powerbuoy]

Ah ... I was not aware of that.

[powerbuoy]

Goose:

The stirlings are in general not too difficult to built. A two to five KW unit is of course a daunting task, nevertheless, there are many small scale units out there. You can even buy some working models on ebay. I have seen stirlings that were made out of soda cans etc. There are entire groups out there dedicated to the stirling ... I wonder, the subject is actually huge enough to have it's own section on otherpower.

Powerbuoy

[Superchargingmachine]

I read the MIT article myself.  What about using a a rotary vane automotive AC compressor?  If you used R134 as the working fluid compressor would be in it's own environment so to speak.

Stirling would be great but a scratch design and build is daunting at best.