Assessment of wind power generation along the coast of Ghana
Introduction
Global decline in fossil fuel reserves, damaging effects of global warming, and rising energy demand due to increasing population have necessitated the need for more research and development of low-carbon sources of energy. There is consensus that wind energy is the leading alternative energy source and the fastest growing segment of the global renewable energy industry [1], [2]. Investments in wind energy have been growing at 22% average for the past 10 years, with wind energy constituting 2.5% of the global electricity supply and projected to rise to 8–12% by 2020 [1]. Ghana is not considered a player in the wind energy sector and does not, in fact, currently produce any significant amount of wind power. Nevertheless, a conservative estimate suggests that over 1000 km2 of land area exist with moderate-to-excellent wind resource potential [3].
Ghana depended solely on hydro power from the mid-60s to the late 90s. However, the country added thermal power in the late 90s due to increased population and poor rainfall patterns. The country’s electricity supply is primarily from hydro and thermal power plants. According the Ghana’s Energy Commission, the total installed electricity generation capacity in 2012 was 2280 MW [4]. This is made up of 1180 MW from hydro (51.8%) and 1100 MW from thermal (48.2%). In the same year the electricity consumed was 9258 GW h, out of which 2931 GW h constituted residential use (i.e., ∼32%). Unfortunately, there still remains close to 28% of households that do not have access to electricity in the country [5]. As a result of cheap natural gas from Nigeria and Ghana’s newly discovered oil fields, Ghana’s electricity supply mix is likely to be dominated by thermal in the near future. The country is beginning to add renewable energy to its energy portfolio. The Volta River Authority, the main generator of electricity in Ghana has just completed a 2 MW solar power plant, which is the largest in mainland West Africa [6]. The company is also projected to generate additional 150 MW from wind power and 14 MW from solar energy by 2015 [6]. As the country diversifies its energy sources to meet its rapidly growing energy demand, due to the expanding economy and growing population, it should consider adding more wind energy. This is because advances in wind turbine technology are pushing down the cost of wind energy so quickly that it will be cost competitive with new thermal plants in the near future.
Wind data in Ghana is traditionally measured by the country’s Meteorological Services Department (MSD). It conducts measurements at its 22 synoptic stations across the country. The problem with MSD’s data is that the wind speeds are obtained at only 2 m (above ground level, a.g.l.). To obtain more suitable wind data for wind energy application, Ghana’s Energy Commission (EC) conducted its own wind data measurement along the coastal areas of the country at 11 stations in the late 1990s. The EC’s measurements were obtained at a height of 12 m (a.g.l.). In addition, the EC conducted new simultaneous measurements at both 2 m and 12 m (a.g.l.) at some of MSD’s locations, and used comparative studies and statistical techniques to extrapolate all wind data at the MSD’s 22 stations to 12 m and 50 m (a.g.l.) [7]. All these wind data measurement activities are well documented in a number of studies [7], [8], [9]. The data indicated that the coastal region of Ghana has the most promising wind energy potential in the country. Nonetheless, extensive analyses have not been performed on the data in order to provide energy policy makers diverse view points for better informed decision making.
The objective of this article is therefore to evaluate the wind energy potential in six selected locations (Adafoah, Anloga, Aplaku, Mankoadze, Oshiyie and Warabeba). These are all located along the coast of Ghana as indicated approximately on the map in Fig. 1 and Table 1. The study will use the existing data in [7] to perform the economic analysis on selected small to medium size commercial wind turbines. This information will help the government of the country and other stakeholders make better informed decisions regarding investment in wind energy resources.
Section snippets
Methodology
The wind speed data for the selected locations were obtained from the EC. Wind speed was captured at the height 12 m (a.g.l.) in all the selected sites, except for Anloga where wind speed was captured at the height of 20 m. In order to reasonably compare wind speed parameters in all the sites, the wind data at Anloga was converted to height of 12 m (using power law expression). The acquired data were obtained on an hourly basis over a period of 12 months (in Oshiyie, January 2001 to December 2001),
Power output of wind turbine
A wind energy conversion system can operate at maximum efficiency only if it is designed for a particular site, because the rated power, cut-in and cut-off wind speeds must be defined based on the site wind characteristics [25]. It is essential that these parameters are selected so that energy output from the conversion system is maximized. The capacity factor Cf is defined as the ratio of the mean power output to the rated electrical power () of the wind turbine [21], [25].
The performance
Results and discussion
For wind turbine performance assessment and economic analysis, four small commercial wind turbine models: Polaris 15–50 [32], CF-100 [33], Garbi-150/28 [34] and WES 30 [35] with rated power range from 50 kW to 250 kW are selected. These wind turbines were selected due to their relatively low cut-in wind speeds (range between 2.2 m/s and 2.7 m/s) and moderate rated wind speeds (range between 9.5 m/s and 13 m/s). The chosen wind turbines are appropriate for site with low to medium wind speed regimes,
Conclusions
In this study, the techno-economic analysis of wind energy development in six selected sites along the coastal region of Ghana was examined. The findings from this study can be summarized as follows:
- 1.
The wind resource along the coastal region of Ghana can be classified into Class 2 or less wind resource category. This makes wind resource in this area marginally suitable for large scale wind energy development or suitable for small scale applications and can be useful part of hybrid energy system.
Acknowledgements
The authors would like to thank the following for their help with additional energy information on Ghana: Mr. E. Nketsia-Tabiri, and Mr. I. Edjekumhene.
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