Solar collector field and thermal energy storage for auxiliary component in organic rankine cycle for bottoming unit to utilize exhaust steam from back pressure turbine of Ulumbu geothermal power plant

Abstract

Flores has a vast geothermal energy sources, one of the fields, Ulumbu, producing electricity from the geothermal power plant (PLTP). PLTP Ulumbu has two back pressure turbines generating 2.5 MW electricity. Besides geothermal power, Flores has potential solar energy sources that are recorded as much as 5 to 6 kWh/m2/day. The exhaust steam from the backpressure turbine adds the binary cycle as the bottoming unit. It is able to generate electricity continously to supply the baseload. Currently, the peak load of electricity usage in Flores is supplied by the diesel power plant (PLTD). This paper studies the addition of solar collectors and thermal energy storage (TES) as auxiliary components in the binary cycle and simulates the system by using the Aspen Plus. The solar energy is stored in TES during the day and then released to the heat exchanger in the evening. This idea reduces the dependency on diesel power plants in the evening. To increase power as much as 500 kW, the collector area needed to supply the system is 1.1 ha using synthetic oil as HTF. The volume of TES to stored the energy by using nitrate salts as HTF is 1,120 m3. As a result, the efficiencies of the non-hybrid system and hybrid systems are 11.38% and 11.31% subsequently.