Feasibility Study of a Hybrid Solar/Bio-Oil Thermal Power Generation Plant in Northern Ghana

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Solar energy plants benefit from the use of a freely available source of energy but suffer from the intermittency of the day/night cycles and also from periods of reduced irradiation. Bio-oil power plants are comparatively less expensive to build but have to confront the higher cost associated with the continuous supply of large amounts of a seasonal and relatively expensive bio-oil for fuel. Concentrating Solar Power (CSP) with supplementary bio-oil combustion evidences the possible integration of these two technologies in the generation of electricity. This thesis provides a preliminary technical and economic analysis of a 20MW stand-alone Power Tower at Wa, a location with daily average DNI of 4.288 kWh/m2/day. The analysis, using RETScreen software version 4 established a capacity factor of 17.87% for Wa, with a negative NPV at a bulk supply tariff of US$ 0.08 /kWh. Three technical concepts for hybrid solar/bio-oil combustion power plants are developed and the concept of integrating flat plate collectors into a bio-oil combustion steam power plant selected because of the relatively low DNI simulated for the selected site. At the current PURC Bulk Generation Charge of US$ 0.086 /kWh, and Jatropha oil prices of US$ 950 /Mt, a 20 MW hybrid solar/bio-oil thermal power plant at a capital cost of US$ 1,748 /kW would yield a negative NPV. The financial viability of the plant is confirmed at a tariff of US$ 0.34 /kWh, at the prevailing Jatropha oil prices. A 40% drop in the Jatropha oil prices will however yield a positive NPV and a payback period of 3.2 years at tariffs of US$ 0.26 /kWh. This study concludes that a combination of low bio-oil prices and relatively low feed-in-tariffs is the way to improve the financial viability of bio-oil combustion power plants in Ghana.
A thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirement for the award of Master of Science degree in Mechanical Engineering, September-2012