Assessment of Air Quality for Development Options at Olkaria Geothermal Field in Kenya

摘要

Utilization of geothermal energy for direct and indirect uses is inexorably gaining momentum in many parts of the world endowed with the resource. Kenya has plentiful geothermal resources estimated to be over 10,000 MWe that have not been exploited to full potential. The power demand in Kenya exceeds the supply and has been growing at 8% per annum. Consequently, the Country has developed ambitious strategy, and intends to inject into the national grid an additional 5,000 MWe by the year 2017, which is about three times the existing capacity. Out of this, 700 MWe is expected to be generated from the Olkaria Geothermal Field. Kenya Electricity Generating Company (KenGen), the leading power producer in Kenya, owns and operates 430MWe at the Olkaria Ⅰ, Ⅱ and Ⅳ power plants. In addition, KenGen has employed well head technology and is currently generating 46.1MWe from well head generators. Olkaria Ⅰ & Ⅱ Power Stations and some of the well head generators are located within Hell's Gate National Park and are at close proximity to commercial flower farms and Lake Naivasha which is a Ramsar site. Geothermal operations emit hydrogen sulphide gas which may impact negatively on commercial flowers, vegetation and wild animals. Hence there is need to consider the cumulative effects of hydrogen sulphide gas emitted from the power plants. This paper assesses the potential air quality impacts associated with the existing and proposed development options at Olkaria Geothermal Field. CALMET and CALPUFF dispersion models, which are recognised by US EPA, have been employed to assess the air quality associated with emissions from geothermal operations. Three different emission scenarios, representing the existing and the proposed geothermal development options have been considered.