The Viability of supplying an industrial park with thermal energy from Menengai geothermal field, Kenya

Abstract

Kenya has an installed geothermal capacity of more than 600 MWe, and more geothermal energy projects are under development (Matek, 2016). One of the fields under development is Menengai, which is owned by the Geothermal Development Company (GDC). Besides developing the Menengai field for electricity generation, GDC intends to establish and industrial park which will be powered using geothermal energy in the same field. The industries located in the park will not only benefit from green electricity but they will also utilise the other by-products of electricity generation such as excess heat in separated brine and/or low pressure wells, dissolved substances in the geothermal brine, non-condensable gases such as carbon dioxide and hydrogen sulphide among other by-products. Analysis of the demand for industrial process heat in the park resulted in the creation of three scenarios with a demand of between 6 MWt and 22 MWt. This energy would be obtained from hot geothermal brine produced in the Menengai field. Five possible options for supplying this energy to the industries were analysed. The options considered for energy supply were separated brine from power generation, brine from low pressure wells or a combination of both. This energy would be extracted through heat exchangers and delivered to the industries through pipes, a distance of 6 km. The energy was cascaded among different thermal processes in order to achieve a high degree of energy utilisation.

This resulted in a 60% reduction in the amount of water required to transport thermal energy to the industrial park. Since water is the energy carrying medium, a suitable tariff for the hot water was determined to have a floor of 2.39 $/m3 and a ceiling of 7 $/m3. The floor price was determined using the operating costs as the basis while the ceiling price was determined using the price of alternative sources of fuel for industrial applications. All the analysed scenarios and options proved to be profitable after 25 years of operation with a payback period of between 6 and10 years and an Internal Rate of Return of between 20% and 30%. The most suitable option for supplying thermal energy to the industrial park for each of the scenarios was then determined by considering a number of criteria.