Independent researcher, Germany.
The present paper is aimed at describing a “closed cycle” power plant schematic (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 of the combustion products to the pond to feed algae. The oxygen used for combustion is released to atmosphere in photosynthesis. As a renewable fuel for combustion after drying 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 concentration in salty water 1:1000. Energy efficiency is less than in photovoltaics but energy expenditures to construct the pond as solar energy receiver are much less, it gives some economic benefits. The present paper highlights the interest of immediate combustion of the dried biomass fuel without converting it in liquid transportation fuel. The latter is the cause of additional technological problems and energy losses.