Assessment of renewable energy resources potential for rural electrification in Kenya
Wekesa, Cyrus Wabuge
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Increased international prices of petroleum-based products, rapid depletion of fuel-wood supplies and increased environmental concerns over air quality, global warming and acid rain, among other factors, have prompted a world-wide growth of interest in the utilization of renewable energy resources for electrification purposes, especially in the isolated rural areas. This research study was done in order to know quantitatively, how much potential electrical power can be harnessed from the hydro and solar resources in Kenya as well as its seasonal and daily profiles for the purpose of rural electrification. The daily profile of the rural loads was also determined and compared with the profiles of the two renewable energy sources (solar and hydro). Further, the cost of electrical energy from the two renewable energy sources was compared with that obtained from extension of the grid network. Mini- and micro-hydropower sites and the potential electrical power at each site were determined with the aid of 1:50,0000 scale topographic maps and river flow data available at the Survey of Kenya Institute and Ministry of Water Development respectively. On the other hand, solar sites and the potential electrical power associated with each site were determined with the aid of solar radiation data from Kenya Meteorological Department, Nairobi. The potential electrical power at each solar site was determined assuming 12% solar cell conversion efficiency. A daily rural load curve was determined from consumption data taken at Gachororo Village, Thika District. Further data on country-wide rural loads was obtained from Kenya Power and Lighting Company. The discounted cost of electrical energy from small hydropower, solar and grid supplies was determined with the aid of cost data from Kenya Power and Lighting Company, Tenwek Hospital and Brooke Bond Kenya Limited (Kericho], Chloride Exide (K) Ltd., Baumann (K) Ltd., Total Solar (K) Ltd., Solar BP (K) Ltd., Salogen (K) Ltd., and Telesales (K) Ltd. The thesis documents investigations that have been made in the areas mentioned. The comparison of the cost of electrical energy from grid, mini/micro hydro, and solar energy supplies was done with reference to Gachororo Village, Thika District. In total, 50 hydro sites were identified with a total average annual electrical power of 12917 kW,while 80 solar sites were identified, with the highest average potential electrical power of 74.8 W/m2 available at Lokori in Northwestern Kenya. At Gachororo Village, it was found that the highest amount of potential electrical power from solar radiation is about 90 W/m2 experienced at mid-day, showing the low energy density in solar radiation. This makes solar photovoltaic supply systems unsuitable for providing motive power or even runmng refrigeration and ironing equipment. unless batteries of suitable size are employed. It was found also that about 71% of the electrical energy supplied to rural areas serves mainly domestic consumers whose power demands are less than 25 kW. This was further confirmed by the load study at Gachororo Village, where the electrical power consumption was found to be low with a daily load factor of 26.8%. The cost of electrical energy from both small hydropower and grid supplies was found to be strongly dependent on the annual capacity factor and the supply-to-load distance. The cost of solar supplies was strongly influenced by the fact that the ratings of the solar panels available on the market are low. being mostly less than 100 peak watts. Hence solar PV installations have very high cost per kW of installed capacity. which reflects high cost per kWhof electrical energy delivered. Gachororo Village is about 100 metres from the nearest grid point and 10 km from the nearest small hydro site. At an annual capacity factor of 30%. grid extension was the cheapest way of power supply to the village (KSh 2.60 per unit). followed by small hydropower (KSh 16.60 per unit) and finally by solar photovoltaic supply (KSh 155.30 for a 51 W installation). The distance beyond which grid supply becomes more expensive compared to small hydro supply was found to be 35.33 km at 30% annual capacity factor.