Simple Solar Power Production

[hvirtane]

The simplest devices I know for utilizing the direct solar energy for electricity are solar pumps working on thermal principles. Pumps pumping water up, the gravitational energy utilized by running the water down through water turbines.

I've designed myself a couple of them and I know that some other people have built devices based on very similar ideas.

One design is based on thermal expansion and contraction of metals. Basically a long metal tube rod working as the pump rod. The tube is cyclically filled with hot water heated by sun rays and cold water from a well or a lake. The long tube rod is connected with a large piston pumping water up.

The other pump works by creating steam by concentrated solar rays. Steam is put to work on the water piston. Cyclically the steam chamber is cooled by the cool water pumped up.

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Still another simple way to pump water up is to use a similar device as with your coffee maker. You can see, how a coffee maker works to pump water up by opening it. Instead of electricity you will use concentrated solar rays to heat the water.

As far as I know that principle to utilize solar pumping energy has been used only by an American company to make a solar heating system. They didn't use the water gravitation energy, just pumped water up and took the heat out of it while the water is running down.

I've been thinking that it is maybe also possible to use the principle of the coffee maker to make mixed steam and water to run a special turbine or even a piston steam engine (to make electricity). I've already made a tiny prototype.

The efficiencies of these solar pumping machines are not known to me. But it is very efficient to get energy out of the water running down, the conversion rate into electricity can get up to 90%.

[wdyasq]

Back in the late 50's and early 60's, the US Space program was looking for ways to power space craft. They prototyped things similar to what you are proposing.

Almost all of the work on these devices stopped with the invention and development of the solar call.

I think your efficiency claims are a bit over the top.

Ron

[wooferhound]

can't you just skip the pumping step, and turn your electric generators directly ?

how could you power a spacecraft by pumping water "up" in weightless space ?

if you want to boil water with concentrated solar rays, you will need some serious tracking.

[fcfcfc]

Very inefficient..... you are wasting a ton of BTU's...

.....Bill

[stop4stuff]

Solar Electric Generating System (SEGS) has been in operation in the US for a while... claimed efficienties of 18% solar to electricity conversion. And for you lucky peeps in the states, the generators here total 160MW

more info here & here

A solar cogen system (electricity & hot water) could increase solar energy efficientcy loads.

[wooferhound]

More stories about pumping water uphill to make power

http://www.fieldlines.com/story/2004/9/24/8125/03434

http://www.fieldlines.com/story/2007/10/18/45127/063

[hvirtane]

Yes, I know about these big systems quite well.

I've got in my mind a system, which would use the water as running down to generate electricity.

It was my last choice to power the turbine directly by the steam. The last choice because it is not easy to make an efficient turbine.

- Hannu

[hvirtane]

There was a pump patented and made in Denmark, which utilized flat solar panels, the same as for solar space heating. The 16 square m solar panels produce steam, which powers the pump.

According to the specifications of the pump the water as pumped during one day would contain about one kW hour energy potential if the water would be run down. The designer of that pump was probably never thinking to use it as a power system, just as a water pump.

- Hannu

[hvirtane]

"I think your efficiency claims are a bit over the top."

I wrote that the efficiency to get power out of running water down can be as high as 90%.

I don't know how high you can get the efficiency to utilize solar energy to pump water up. I guess it might be about 15%...

So you could get even almost the same efficiency as with PV cells but with a very low tech design. PV cells are high tech things, which have not became at all cheaper during last ten years.

- Hannu

[hvirtane]

That Danish pump you can find here:

http://www.fastonline.org/CD3WD_40/JF/JF_OTHER/SMALL/Soby-Sunice%20-%20water%20pump.pdf

A few years back in India with a company I started making a prototype of a similar pump, but we had so many other projects (including wind turbines...) that we didn't finish the prototype building job at that time.

- Hannu

[Ungrounded Lightning Rod]

Pumping water with solar heat means you're making a heat engine.  It is limited by the carnot cycle - which means if the hot end is only slightly hotter than the cold end you only get a tiny amount of the energy out of the heat as work.  The "thermal expansion" one looks like such a low-difference engine.  Steam is better - but still only in the ballpark of photovoltaic.

If you're making a solar heat engine, why not make an efficient one, run a genny off it, and store the power in a battery?  There are SO many loss mechanisms in pumped-water gravity storage that I hesitate to go into them here.  If carefully engineered they CAN be good enough to store cheap nighttime energy for peak demand periods.  But for smaller loads you'll likely be far ahead in price-performance using batteries.

[hvirtane]

"But for smaller loads you'll likely be far ahead in price-performance using batteries."

One goal is to get rid of batteries, too. Nobody has invented 'a good battery storage' yet.

For storing big quantities of energy we don't have yet any other means that water pumped up.

For small energy systems you might be right that the price-performance in short term is better with lead acid batteries. But batteries have got several problems. It is quite difficult to make them yourself 'at home', they don't last more than a few years and they contain toxic materials.

Water tanks you can do yourself. Almost any blacksmith can make a reasonable efficient Banki water turbine. As the generator you can use an induction generator, because you can put your water turbine to run fast and with a steady speed.  

- Hannu

[hvirtane]

"you're making a heat engine. It is limited by the carnot cycle"

I'm not sure, if the principle of heating and cooling metals would be limited by the carnot cycle. Heating and cooling a metal (copper) tube rod with solar heated water and using that rod as the rod of a big water pump piston rod, is one of the ideas as presented above.

So far I know only about one pump built based on that idea. The pump was built by a Danish man, whose name I cannot recall just now.

Both those Danish stories were told to me by the great man, John Furze, 'JF' on this board. He has got more knowledge about renewable energy devices as built in the world, than anybody else I happen to know.

- Hannu

[Ungrounded Lightning Rod]

I'm not sure, if the principle of heating and cooling metals would be limited by the carnot cycle.

ALL heat engines are limited by the Carnot cycle.  This is because the Carnot cycle is reversible.

If you COULD make a heat engine that could beat the Carnot cycle efficiency you could use it to drive an efficient heat pump at near the Carnot cycle efficiency and use the heating/cooling of that to power the heat engine - with energy left over to power other stuff.

That's a perpetual motion machine of the first type:  violating the first law of thermodynamics ("You can't get something for nothing.")  They can't exist in this universe.