Breakthrough improvement of solar thermal plants

Method of breakthrough improvement of solar thermal plants

Author: David Judbarovski, judbarovski@gmail.com

Linkedin.com

Background

Conventional solar thermal power plant can comprise a field of heliostats (i.e. large planar mirrors equipped by sophisticated tracing system being principle different each to others) and very high and expensive tower and a tank on its top. The said heliostats redirect solar beams on the said tank and heating the said tank content. Because solar irradiation being very variable, ordinary we need to store solar energy to release if in low irradiation and in sunless periods, and for such purpose a melted salt is used by special two tanks system.  

The larger heliostat, the more expensive of each squire meter proportionally to its linear dimensions to resist wind loads and to own weight, but correspondingly the control system sufficiently to be simpler and cheaper. So about 100 m2 area of each heliostat with USD 100.0/m2 was as a compromise to minimize their total cost being totally very expensive, and solar electricity is expensive too.

Another disadvantage is very expensive solar energy storage, and the said salt was earlier quite suitable by its cost, for the last ten years it is now some times more expensive in the markets. 

My method can allow breakthrough to improve solar thermal power plant by its cost and by the cost stability. 

Some years ago I sent several appeals to several professors of USA to create their students’ competitions briefly for most cheap solar thermal concentrator. The cheaper it, the cheaper electricity of it. No one answer me, but several month letter the Department of  Energy (a kind of federal government ministry of USA) called for brief three steps competition for the same purpose with some prizes of some million dollars totally. I don’t know the competition results. For foreign participation there were financial obstacles, while realization.  

My estimations showed there that USD 10.0/m2 of solar flux was quite achievable for single concentrator. 

Here bellow I disclose my system now sufficiently changed, upgraded and updated.

Disclosure for experts

Solar thermal power plant comprises blocks of many solar concentrators each and a tank for the block.

The said block consists of a line of solar concentrators from both sides of the tank.

The said solar concentrator consists of a planar square mirror of about 2 m2, equipped by tracing control system, a dish concentrator of 1.0m2 solar flux, a small curved mirror, two small tilted mirrors, and pedestals for the all of them.

The said planar mirror serves to redirect solar flux on the said dish concentrator. The small curved mirror straightens and then redirects the concentrated solar beams on a pair of small tilted mirrors. The said tilted mirrors successively redirect concentrated solar beams at first vertically and then horizontally, and then on the said tank surface. Pedestals of the small tilted mirrors of the all blocks serve to distribute the concentrated solar beams uniformly on the said tank surface.  

If the said tank is 2.5 m2 one side area, so 5.0 m2 for the both sides, and if concentrated spot from one block being 7 cm * 7 cm = 50 cm2, so 5 m2 /50 cm2 = 1000 concentrators, can heat one tank controlled supplied by the recycled water near 100 C to create the water vapor at about 600 C temperature.

For southern regions one tank gives 10.0 million kWh heat in 5 years payback, or 4.0 million kWh of electricity. Even if USD 20.0 for one concentratin pair, while other COPEX is negligible, and if heat loses 20%, so USD 20 * 1000 / 4,000,000 kWh * 0.8 = USD 0.0063 /kWh.  For moderate climate is 1.5 times more expensive, up to 1.0 US cent/kWh.

For heat storage I can recommend such common and abundant resource as Ca(OH)2 =  heating =  CaO + H2O – 650,000 kJ heat/ton Ca(OH)2, can be bought by USD 100-150/ton. Reverse reaction can bring the stored heat back. It adds negligible share to a cost of electricity, while conventional salt (mix of KNO3/NaNO3) as a heat storage medium badly variable with international relations and much more expensive.