The Potentials of Wind Energy

Applications in Eritrea

S. Habtetsion¹, D. Ghebrehiwet¹, R. Van Buskirk², B. Lebassi³

  ¹Department of Energy, P. O. Box 5285 Asmara, Eritrea, e-mail: semere@ec1.doe.gov.er

 ²Eritrea Technical Exchange, 3217 College Ave., Berkeley, CA 94705, e-mail: robert@punchdown.org

³Department of Meteorology San Jose State University, One Washington Square, San Jose, CA 95192-0104 e-mail: bereket@metsun1.met.sjsu.edu

Abstract

Eritrea is embarking in a program to assess its renewable energy resource. The purpose of this paper is to critically analyse the potentials of the wind resources for various applications including grid connected, decentralised stand-alone or hybrid systems, and even for mechanical water pumping.  Socio-economic and environmental benefits have been highlighted.

Preliminary results from the wind resource analyses show that there is strong potential for wind electricity conversion in the southern coastal areas and in two highland passes, where the yearly wind speed averages are over 6m/s.  All stations indicate average speeds greater than 2.5m/s, i. e., good enough for mechanical water pumping.  Scientific analysis on the capacity factors, wind speed frequencies and distributions, determination of Weibul parameters, effects on elevation on wind speeds etc. have been conducted.

1. Introduction:

Eritrea is one of the least developed countries of the world facing acute modern energy shortages especially in the rural areas. The comprehensive energy survey of 1998 by the Department of Energy (DoE, 1998) estimated the total final energy consumption to be around 619,580 toe of which 68% was accounted by the household sector, 16% by the commercial/public sector, 13% by transport and 3% by industry. The sources of energy were 66.3% biomass based (fuelwood, dung, charcoal, agri-residue), 31.6% oil products and 2.1% electricity, which is all generated by thermal means using oil products.  It is also noted that 98% of the rural population and 20% of the urban residents do not have access to electricity; national electrification level was 20.7% in 1998.  Over 80% of the energy needs of rural enterprises is met by biomass or animate/human labour.

Eritrea has the formidable task of providing modern energy to the growing economy as well as to the over 70% rural population to give services to their development needs. The major constraints and barriers encountered in the country's effort to meet the growing demand for commercial energy include: lack of finance and technical capability, lack of proper and reliable assessment of the potential of endogenous energy resources, inefficiencies in energy production, distribution and consumption and lack of awareness in energy conservation, renewable energy technologies etc. The overall energy situation in the country calls for prompt action aimed at the development of the sector in a manner that is sustainable.

The overall rural-focussed development objective in the energy sector is to help increase the standard of living for the rural communities in Eritrea through the delivery of modern energy services while protecting the environment. Of the various intervention options being initiated by the Government for realising this objective include: -

1.       rural electrification through grid extension,

2.       improvement of biomass energy resources through various afforestation and reforestation programmes,

3.       dissemination of improved stoves which has the potential of reducing biomass energy by 50% and CO₂ reduction of 0.6 ton/year per household, and

4.       assessment of the potentials of renewable energy resources for eventual development.

Eritrea has installed 25 wind and solar monitoring stations distributed throughout the country during 1999-2000, with the co-operation of its development partner, Sida (SWECO,2000/2001). Earlier in 1997/8, the GEF financed a feasibility study for wind energy applications in the southern coastal areas with five stations installed for that purpose (Lahmeyer,1999). All of these stations have additional temperature, humidity and pressure sensors.

We provide some preliminary analysis regarding the wind energy potential of Eritrea based on recently collected data from the 25 recently installed meteorological stations. Wind power is becoming the most dynamic sub-sector of power generation in the world, growing at above 30% annually since 1998 and accelerating (UNDP, 2000). The technology is constantly improving and bringing down both investment and operating costs. At the best sites, the cost of wind power now equals that of the most efficient new fossil-fuelled utility scale plants, about 3 US cents/kWh for the large-scale wind turbines.

2. Wind Monitoring Network

The wind and solar stations installed for resources monitoring purposes, and the average wind data for the year 1999/2000, their geographical co-ordinates are given in Table 1.

Table 1: List of Meteorological Stations, location and yearly average wind speeds

Asmara defies the 1/7 power law for the effect of vertical elevation on wind speeds. Local surface roughness causes an underestimate of the 10 meter wind speed. For the relatively flat areas of Tio, Alighider and Assab, the wind speed increases slowly with vertical elevation which could be approximated by the 1/7 power law.  Based on the wind power class denominations of 1-7 (Grubb & Meyer, 1993) where a wind class of 7 indicates the highest potential, all the 25 stations are classified as given in Table 2.

The historical data that existed suggested that the southern coastal region has very good wind conditions (Rosen, 1998). Indeed this is the case as shown in Table 2 for Assab and Gahro, south of Assab, which are in Classes 6 and 7 respectively. At 30-meter height, Assab changes class from 6 to 7, Asmara and Alighider from 1 to 2, Tio from 2 to 3, Nakfa stays where it is at 2 probably due to the location of the station on a hilltop. Moreover, the wind measurements have identified two promising sites in the highland areas for wind electricity conversion, namely Gizgiza (Class 5) and Dekemhare (Class 4). These places are along the windy passes that connect the eastern and western escarpments. Areas classified in Class 1, with average wind speeds ranging from 2.5-4.4 m/s are expected to be suitable only for wind water pumping and not for electricity generation. As the minimum yearly average speed recorded is above 2.5m/s, mechanical wind water pumping could be installed practically everywhere.

Table 2: Wind speed, power density, and power class of the 25 Eritrean wind stations

3. Potential Wind Energy Applications

From the previous GEF sponsored projects, the feasibility study on wind energy applications in the southern coastal areas and other historical data, it was known that the area has an excellent potential for utility level electricity generation as well as decentralised stand-alone or hybrid systems for small towns and villages. The barriers for wind energy development have been identified and measures to remove them proposed with GEF financing. A wind park of aggregate capacity 2.5 MW was proposed for Assab and many pilot and demonstration wind energy applications are expected to be installed soon in that area. The private sector and the Eritrea Electric Authority will have a joint venture arrangement for the wind park.

Figure 1 shows the hourly wind speeds at 10m height averaged for the whole year (mid 1999- mid 2000) for some of the better wind energy locations in Eritrea.  The two verified areas of high potential are the Southeast coasts represented by Gahro, and the highland passes.  The Gahro station in the figure can be seen to have an hourly pattern that matches the type of hourly pattern one might expect from commercial electricity demand. The site is representative of the Southeast coast which has the greatest wind power density and therefore potentially the cheapest cost production in Eritrea. Such a wind energy resource could therefore support commercial and industrial development driven by inexpensive clean energy. As a representative of the region, detailed evaluation of the wind potential characteristics, Weibul parameters and capacity factors for a hypothetical 600 kW wind turbine has been conducted and this is presented in the following figure.

The Dekemhare and Gizgiza stations represent the highland pass areas.  These sites have peak wind speeds in the late afternoon and early evenings when there is the domestic and lighting energy peak on the central grid.  This reflects a potential for wind energy to supplement existing central grid generating capacity in a way that helps ease the peak loads on the system.  

The Kerkebet station represents the far Northwest of the country where it will be economically difficult to extend the electricity grid. This area of the country also has some of the best and most consistent solar resources of the country, and the hourly pattern of the wind resource in this area shows a good potential for hybrid solar and wind systems.  At Kerkebet, the wind resources is at a minimum in the middle of the day when solar resources are at a maximum and the wind resource is at a maximum at night and evening when solar resources are unavailable and lighting demands are high.  

4. Socio-economic and Environmental Benefits

Sustainable development of Eritrea's wind energy resources will involve the development of the infrastructure to take advantage of the full economic and social potential discovered in the physical wind resource evaluation.  This economic potential includes the social, environmental, and national self-reliance value that can be realized through development of the resource.

Potential social benefits include the development and cheaper and more productive hybrid and village-level applications.  More economical development of modern energy sources for remote villages allows for development that decreases the inequality in electricity access between rural and urban populations.

Potential environmental benefits include the decrease in reliance on fossil fuels and more rapid conversion of the world economy to clean energy sources.  The Southeast coast of Eritrea has as much as 100 - 200 kilometers of  class 6 and 7 wind sites at which wind turbines may operate at 40% - 60% capacity factor.  The diurnal pattern of the resource also is correlated with the typical commercial and industrial loads.  As a very economical clean energy resource, this site may be used for energy-intensive production for export.  Such export production could displace petroleum-based energy intensive production and may substaintially contribute to decreasing the carbon intensity of selected industrial sectors globally.

Potential benefits to national self reliance include the decreased dependence on imported fossil fuels that wind energy investments may bring.  This will decrease the vulnerability of the developing Eritrean economy to economic shocks from fluctuating petroleum prices.

Conclusion

Eritrea has a potential for wind energy applications ranging from Class 1 to 7. The capacity factors for the best wind potential area of Gahro has been determined as part of this work. The more impressive and consistent result for the southern coastal areas is that the capacity factor estimates for selected »300 kW turbines are between 40% and 60%.  This is a very high capacity factor, which should indicate the potential of large-scale clean energy for industrial and commercial purposes near the major port of Assab and south of it towards the border with Djibouti where Gahro is located. In comparison, most of the wind turbines installed in Europe or USA have capacity factors in the range of 20-30%.

The wind passes along the highlands have also good potential for electricity generation as reprented by Dekemhare and Gizgiza, which are close to the central national grid system. The highland pass areas also have a good diurnal correlation with system demand that increases their economic value.  The Northwestern lowlands, represented by the Class 3 wind site of Kerkebet, also have also good potential for electricity generation that can hybridise a solar system as this site also has some of the best solar insolation in the country averaging around 5-6 kWh/m².

REFERENCES

DoE (1998), Updating the Energy DataBase of 1995 for the Year 1998, Asmara, Eritrea

Grubb, M. and N. Meyer. 1993. Wind Energy: Resources, Systems and Regional Strategies. In Renewable Energy: Source for Fuels and Electricity, edited by Thomas B. Johansson, Henry Kelly, Amulya K.N. Reddy and Robert H. Williams, 157-212. Washington DC: Island Press.

Lahmeyer International, Wind Energy Applications in Southern Coastal Areas of Eritrea, ERI/96/G41,1999.

SWECO International, Wind and Solar Resource Assessment in Eritrea, Progress Reports, 1999-2001.

UNDP (2000), World Energy Assessment, Energy and the Challenges of Sustainability, UNDP, UNDESA, World Energy council, New York.

Rosen, Karen, (1998), An Assessment of the Potential for Utility-Scale Wind Power Generation in Eritrea,

        Masters Thesis in Environmental Studies, San Jose State University