The wind-hydro energy mix: a case study for Zambia

Abstract

The aim of this research is to examine the wind-hydro energy mix by analyzing the characteristics of wind energy variation in a year and that of hydro. The research uses the calculated values of wind power from the wind speeds recorded at 80m above the ground and the values of the actual generated hydropower for seven years. The useful information used is for the monthly wind speeds in a year and the monthly hydro production profile in a year. The profiles are compared in the wet and dry seasons of the year in Zambia as the seasons are directly related to water levels in water reservoirs and hence hydro power production. The wet season is a regular period of the year when there is prolonged rainfall while the dry season is a prolonged period of continuous dry weather. The information about the wind speeds for power generation where obtained from the recently completed wind resource mapping in Zambia. The research found that the annual wind generation potential is at the minimum in the rainy season and maximum in the dry season and the daily wind energy production potential is at the maximum in the night when demand is at the minimum and vice versa. In the same vein, the annual hydro generation potential is the maximum during the rainy season and minimum during the dry season. This is because of the increase in the water levels in river, lakes and dams, which are the source of the water for power generation. Since wind is highest when hydro is lowest and vice-versa, wind energy can be used to complement hydropower to avert power shortages that occur during the dry season. Another aspect is that there is a difference in the relationship between the wind and large hydro as well as the wind and mini hydropower. The power generation from large hydro power plants is not necessarily low in any season except for the month of February in all the past seven years. This is because of the large dams in which water is stored and it is release in a regulated manner. Mini hydro’s however use weirs and run off rivers which are highly affected by water levels. The difference in the power generation over the seasons therefore is significantly visible in the mini-hydro power stations. The wind-hydro complementarity is therefore more applicable with mini hydropower. Most of the mini hydro power stations are in the Northern region of Zambia and the wind regime in the region is viable for power production. Therefore, there is need to consider the wind-hydro energy mix to reduce the seasonal power reductions which causes power outages in the country. From the average power produced from mini-hydro stations for seven years, the total maximum deficit during the year is 48%. The recommendation is that the installed capacity of wind in a network fed by mini-hydro power should be at least 48% of the total mini-hydro generation to cater for the reduction. Key words: Wind, hydro, energy, power