Rezumat
Present paper is aimed at describing a “closed cycle” power plant schematics(SOFT, Solar Oxygen Fuel Turbine) with macroalgae (seaweed) cultivation in a pond, combustion of its organic matter in a fluidized bed boiler of Rankine cycle and return the combustion products to the pond to feed algae. Used for combustion oxygen is released to atmosphere in photosynthesis. It is further elaboration of the paper in ECOS2005 in Trondheim. As a renewable fuel the seaweed Ulva lactuca is selected. Its growth rate from many experiments (in literature) is 0.1 – 0.2 1/day, heating value of dry weight is 19 MJ/kg, optimal concen- tration in salty water 1:1000. Energy efficiency is less than in Photovoltaics but energy expenditures to con- struct the pond as solar energy receiver are much less, it gives some economic benefits. For a power unit of 100 kW the pond surface is about 4 hectare. The cultivation of seaweeds in sea water ponds is well deve- loped in Italy and Israel either for water cleaning or chemicals production. Construction in some future of a SOFT system near to the Dead sea in Israelian desert would provide the country with needed power, chemi- cals and fresh water on account of solar energy. The system is protected by USPat 6,477,841 B1 of 12.11.2002 with priority in Israel of 22.03.1999. In the paper is highlighted much more benefits to customer, than in the patent text, including fresh water by desalination. In view of the active work in Italy on water cleaning due to Ulva using contaminants in water as nutrients with increase of biomass productivity the additional target of the SOFT cycle might be incineration. Some guesses of a desert surface for a massive scale use of ponds are given.