September 5, 2006
Quintessence of Solar Thermal Power System proposed is a combination of
(1) High concentrating of solar radiation by flat heliostat mirrors create high temperature. High-vacuum thermo-insulation invented prevents energy leakage from zones of high temperature. Intensive agitation of heat carrier into solar radiation absorber (AR) guarantees quick and uniform heat distribution.
(2) High-temperature thermo-chemical cycled process splits water. A choice of cheap and common reagents guarantees producing of cheap hydrogen, e.g. by Fe-Cl cycle.
(3) This cheap hydrogen is converted into artificial fuels (mainly with help of high temperature solar energy too) to guarantee compact and safe storage of energy for next applications accordingly to any consume time-table.
Methane or methanol as the artificial fuels could serve either as local energy storage if using cycled carbon oxides for the fuels production, or as fuels for transport and technological applications if using waste carbon oxides from existing conventional warm power stations. WNS (water-nitrates mixture) consisted of ammonium nitrate - NH4NO3 and urea - CO(NH2)2 can be another variant of such artificial fuel. WNS is effective and clean fuel for internal combustion engine, but the WNS needs in a few replenishment of carbon dioxide as reagent for its production
Hydrogen can be used directly for energy and technological needs. But if used for incessant electricity production the hydrogen has to be stored in huge amount, e.g. in liquidized form, and it could double a cost of the system. It is badly expensive and dangerous matter to store hydrogen, especially if in huge amount. So the hydrogen fuel must be used either for on-line applications or as a small buffering reserve.
Just below I intend to estimate economics of the system proposed and to show that solar concentrating systems can be quite competitive in temperate climate zones of Europe and North America too, despite common delusion in opposite.
Let a group of 2500 sq. m.- mirrors' solar systems are put for consideration and their towers to be 60 meter height. Low temperature chemical sub-systems and buffering reagents storage must be placed on the ground. Hi-Temp chemical sub-system is placed upper the AR on top of the tower. The AR is planar form and contains a heat carrier with high melting point of about 400-800 centigrade. In case of the 2500 sq. m. system and Fe-Cl cycle I have estimated the tower to carry about 30 ton on its top, and to weight less than 20 ton and to cost less than US$15,000, whereas AR and chemical system would cost about 15,000 and heliostats would less than 40,000. If summarized, total cost would be less than US$70,000, and the system proposed could produce about k * E / 143 (kg H2/year per sq. meter of the heliostats), there is k < 1 and E (MJ) is energy of direct solar radiation on normal surface of one sq. m in region of the system deployment. For Germany and North USA the E ~ 5500 MJ / year * n. sq. m., so our 2500 sq. m. system could produce roughly 70,000 kg of hydrogen per a your, and 350,000 kg per 5 years if that 5 years is a investment reimbursement period. So such hydrogen would cost 20 cent/kg!!! But hydrogen storage sore problem is forcing us to face for conversion of the hydrogen into more storable fuel form as upper offered.
For example, if the artificial fuel being methanol produced on other solar towers by CO2-H thermo-chemical cycle for following electricity producing, I have estimated a cost of such methanol as about 130,000 /(k * E (KWh) * N) + 12 + 120 (US$/ton), The first addendum is summarized share cost of heliostats and tower and hydrogen, the second addendum corresponds to share of a warm power station of US$1400/KW (full depreciation of 20 years), and the last addendum is chemical technology share. For our moderate climate region of 5500 MJ/n. sq. m./year = E(KWh) * k.~ 1000 KWh, the methanol cost would be US$160/ton and electricity cost would be 4.65 cent/KWh, produced by methanol, during sunless hours, and about 1.1 cent, produced by on-line hydrogen, during sunny hours, so if system capacity factor being 70% and for above-mentioned regions, the system electricity would cost 3.85 cent/KWh. Certainly, it would be bigger if northward or cloudy regions up to 4.5-5.0 cent/KWh .
Capacity factor of artificial fuels produced in summer is much bigger than in winter, but time-table of consume is tended on the contrary, so our system must be adjusted to produce stock of artificial fuel in summer half-year to use it in winter one. For moderate climate zones it would increase the prices nearly on third up to 5 cent/KWh and twice for northern zones like Helsinki, i.e. up to 9 cent/Kwh. Nevertheless it would be quite good price for better ecology and energy security and independency for fuel importers.
Much more expressive results would be if such artificial fuels, as methane, methanol, WNS or others, being used for transport and technological applications, when such fuel cost would be not more expensive than for oil and gasoline tax free equivalents even if our system deployed in poor sun regions of the world, and they would be twice cheaper if moderate climate zones.