Energy, Exergy and Economic Analyses of Energy Sourcing Pattern in a Nigerian Brewery

Abstract

Energy, exergy, and economic analyses of energy sourcing pattern in a Nigerian brewery have been carried out. The mean annual energy efficiencies have varied from 75.62% in 2004 to 81.71% in 2006, while the mean annual exergy efficiencies have varied from 42.66% in 2004 to 57.10% in 2005. Diesel fuel combustion, whether for local electricity generation via internal combustion engines or for process steam raising in boilers, has adversely affected the efficiencies of energy utilisation in the company. The negative effect of steam raising on efficient energy utilisation is more, although steam raising is unavoidable, due to the nature of the company under investigation. The annual mean energy unit costs have also varied from 27.86 USD per Giga-Joule in 2006 to 32.80 USD per Giga-Joule in 2004, confirming the inverse proportion of energy efficiency and costs. On the other hand, the annual mean exergy unit costs have varied from 40.19 USD per Giga-Joule in 2005 to 58.46 USD per Giga-Joule in 2004. The most efficient year has been 2006 energetically and 2005 exergetically. The difference in the two years lies in the proportions of generator diesel and boiler diesel utilised as the system exergy is most sensitive to boiler diesel use while the system energy is more sensitive to generator diesel utilisation due to their different device efficiencies.