Solar Ponds

[coldhead]

Is there any progress or studies going on in this area?

 

A solar pond is basically a large body of very salty water with a layer of purer water on top. The sun heats the water and the lower brakenish water heats quicker. This lower, hotter water starts moving, rising & lowering as it heats and cools. This movement is captured converted to electricity via turbines.

[UncleAl]

Look up Carnot efficiency as a function of source and sink temperatures. You gotta be kidding.

 

Area necessary to generate 1 GW electrical, theoretical minimum

 

Area, mi^2 Modality

==============

1000 biomass

300 wind

60 solar

0.3 nuclear

[coldhead]

You gotta be kidding.

I would not kid around if I thought large areas of 'useless' land could be used to generate electricity for no cost.

As for the maths you gave me, I'll look up "Carnot efficeincy as a function of source and sink temperatures" b4 I even think about the other bits You posted.

[UncleAl]

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html

 

Let's have a source at 122 F (50 C, 323 K) and a sink at an ambient temperature of 72 F (22 C, 295 K). Assuming an incredible 80% conversion efficiency of maximum theoretical to real world, we get

 

(323-295)/323 times 0.8 = 7%

 

Given high noon, no clouds, equinox, ground level solar constant of 500 W/m^2, you'd harvest 35 watts/^m2 maximum. Gasoline has an energy of combustion of 33.16 KWh/gallon. To get the energy equivalent of one gallon of gasoline you would need a solar pond of 1000 m^2 area (104 feet on a side) going maximum theoretical full blast for an hour. How do you plan to harvest its energy at 80% efficency given its area?

 

A middling powerplant is a gigawatt thermal. You would need a pond 5.3 kilometers on a side (11 square miles) - and that assumes maxed out. It cannot run at night. It will have smaller numbers averaged over time of day and time of year. How long will it take to generate the energy used for its parts' fabrication, its construction, and everything's transport?

 

Photosynthesis is very optimistically equivalent to producing 15 bbl/day-mile^2 of diesel fuel and ignoring all energy inputs - irrigation, pesticides, fertilizer, transportation, processing. In the real world you need 1000 mi^2 to harvest biomass energy equivalent to 1 GW thermal. It requires 131,000 Btus to produce one gallon of ethanol frm corn. It yields 77,000 Btus of fuel energy. That's a 70% net energy loss.

[CraigD]

Is there any progress or studies going on in this area?

Yes. According to google, quite a bit.

... A solar pond is basically a large body of very salty water with a layer of purer water on top. The sun heats the water and the lower brakenish water heats quicker. This lower, hotter water starts moving, rising & lowering as it heats and cools. This movement is captured converted to electricity via turbines.

I've never heard of this kind of solar pond. The ones I’ve heard of, like the “nonconvecting ponds” described here, use pumps and/or heat exchangers to keep the warmer, saltier lower layer from rising – the less salty upper layers act as insulators to prevent heat escaping into the air. The actual heat engine has its cool sink outside of the pond.

 

Though solar ponds seem an effective and proven way to generate electricity (the link above mentions a 70 kW, 3200 m^2 pond in El Paso, TX), and are better than direct photovoltaic panels both in cost and their ability to generate power 24 hours/day, they’re not without construction and operating cost, and don’t appear to be competitive with fossil fuel generators (yet).

[sony]

hi friends ,

i read about this word in news paper.that is,

A pond which can produce eletricity.