A Conceptual Framework for a Cogeneration Plant at the KNUST Campus

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Ghana is currently plagued with a persistent trend of inadequate power supply, which has a ripple effect on all sectors of the economy. Efforts are being made at the national level via the Ministry of Energy and Ghana Energy Commission to arrest the current situation, through policies and agreements with multinational investors. Modular biomass-based generation of electricity presents a promising avenue to harness locally available fuel resources in order to increase the national installed capacity. In this study, the technical and economic viability of a 6MWe cogeneration plant to be sited at KNUST campus was assessed as a model of community based electricity generation system. In addition to analysing the cost and thermodynamic efficiencies of the proposed system, an exergy analysis was also performed in order to establish a correlation between the exergetic measures of performance and the overall system’s performance in terms of cost, energy savings and greenhouse gas (GHG) emissions. A 6MWe biomass-based cogeneration plant is proposed with a capital cost of 11.21 US$ million and a levelised generation cost of US$ 0.08079/kWh. It has a second law efficiency of 50.6% and exergy destruction of 0.45 kW per KW of useful power generated. It is observed that second law thermodynamic assessment of a thermal system gives diverse ways of quantifying its performance because measures like the second law efficiency and the rates of exergy destruction depend on the extent of irreversibilities in the system.
A Thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the Degree of Master of Science in Mechanical Engineering, September-2012