In very hot nations a solar pond is an inexpesive way to produce process heat and/or electricity:
A Solar Pond is a large shallow highly saline body of water. The salinity gradient actually traps the heat from the sun in the bottom layer. The temperature can get up to 100 C! Whilst the upper layers act as a form of insulation, this means that the heat is retained overnight.
In practice this heat can be used for a wide range of applications for a great many industries by various forms of heat exchanger systems within the bottom layer of the pond.
Alternatively the lower layer of water can be pumped out and replaced at the top.
The generation of electrical power can be done by introducing further heat exchanges and turbines into the mix.
As the water is not particulaly hot for electrical generation other means of improving the temperature gradient can be utilised to keep the generation fairly constant. Like any system energy in has to equal energy out. Therefore if you extract too much energy the system can collapse. However with careful monitoring this can be avoided.
Sun Earth Energy are proposing a pilot plant to initiate a larger Solar Pond developement right now. As the salt content of the water is the most crucial factor the locations are best next to the ocean, and even then 12 months of evaporation is needed to get to the required salinity content (about 500kg of salt for every square meter of surface)!
Wish us luck. The initial generation capacity will have a peak 5MW and the full cluster configuration will generate a peak 30MW. Not bad for just a boring stretch of water.
And by the way one of the principle directors of Sun Earth Energy did his PhD in 1991 on the computer modelling of solar ponds. And like all over-night success stories - there is some considerable history behind it!