Sun Strides Foundation Solar~power~africa Wind~power~africa

7/28/2019 Sun Strides Foundation Solar~power~africa Wind~power~africa

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bdoulaye~Mouke~YansaneMouke~YansaneAbdoulaye~Mouke Abdoulaye~M~Yansane

Sun Strides Foundation

With reference to the map above, it has been estimated that the solar power systems if installed inthe red areas, that is those corresponding to the North-West USA, Chile, Argentina, North Africa, SaudiArabia and China, could meet the world's current total primary energy demand, with a certain surplus ofenergy, with a conversion efficiency of 8 per cent8. This can be shown in quantitative terms. Forexample, photovoltaic systems, with conversion efficiency of 8 percent, if installed in the red areasdiscussed above would produce an average electric output of 18TWe. This figure corresponds to anenergy output of 13,567 Mtoe per year. Such projected output is larger that the world electric output of11, 741 produced in 20069. This effectively means, as the analysis byYansane indicates, that electricitprovided by solar cells can be gainfully substituted for other forms of energy production, whilesuccessfully providing for all the daily needs associated with energy consumption. These facts indicatequite clearly the potential that solar powered electricity generation systems have even at the currentstage of its technological development.

How Solar Panels WorkSolar panels collect solar radiation from the sun and actively convert that energy into electricity. Solar panels are comprised of severalindividual solar cells10. The functioning of these solar cells can be compared to the similar functioning of large semiconductors. The solarcells utilize a large-area p-n junction diode11. When the solar cells are exposed to sunlight, the p-n junction diodes convert the energy fromsunlight into usable electrical energy12. The energy generated from photons striking the surface of the solar panel allows electrons to beknocked out of their orbits and released; the electric fields in the solar cells pull these free electrons in a directional current, from whichmetal contacts in the solar cell can generate electricity13. A larger number of solar cells in a solar panel and the higher the quality of thesolar cells, the greater will be the total electrical output that the solar panel can produce14. This conversion of sunlight to usable electricalenergy has been dubbed the Photovoltaic Effect15. It has been reported that as of May 2009 the solar energy industry's highest conversionefficiency of solar panel stands at 22.8 percent16.

There are various crucial factors which have to be considered when designing and operating solar panels for energy generation. One ofthe central features for the design of solar panels has to do with its ability to provide electricity during the absence of sunlight. The fact tha

the amount of electric current generated by a solar cell is directly proportional to the intensity of sunlight shows the importance of such a


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design feature. For it is self-evident that there will be times when the absence of sunlight is quite pronounced, such as when there is aheavy cloud cover or during night time. At such periods, no electricity can be generated unless stored energy from sunlight is available forelectricity generation. Consequently, a photovoltaic energy storage system is required. The most common of which are batteries equippedwith a voltage regulator to prevent an overcharge of batteries.

When operating solar panels, their efficiency can be optimized by using movable mounts that follow the position of the sun in the sky.This is important since one of the central features of the solar panels is their direct dependence of their performance on the amount ofsunlight received. Rotation of the dynamic mounts has the advantage of increasing the solar panel efficiency, and hence its electricityoutput, by enabling the solar panel to get the maximum amount of direct exposure to sunlight17.

Choosing the right system18Determining the size of the photovoltaic system is crucial. If system design is undersized, this will result in the undergeneration of

electricity. Conversely if the system is over sized, this will result in excess capacity and will represent an unnecessary expenditure offinancial resources. The PV system design starts with a definition of the electrical loads. The initial system cost will be d irectly proportionalto the amount of energy that the system is designed to provide. The electrical load is directly proportional to the electrical consumption ofappliances which use the generated power. Consequently, a reduction of the load requirement (kWh) by 50 per cent will lead to a pricereduction of the PV system by 50 per cent, thereby saving a substantial amount of capital for the potential investor.

The potential costs of running a solar panel system can be illustrated below:

The daily load can be calculated as follows:

Daily Load = Watts used by appliances x Time in use

In order to determine an approximate cost of a photovoltaic system to power the total daily load, various types of the photovoltaic (PV)

system have to be taken into account. Provided that the PV system is simple, the total daily load has to be multiplied by three. Similarly, ithe system is typical, then it should be multiplied by four and when it is complex, it should be multiplied by five. Let us say that a simplephotovoltaic cell generates 500 watt-hours per day. Then we can determine the approximate cist of such system will be represented by500x3 that amounts to $1500.

Solar Energy19About 1.9 x 108 TWh per year is absorbed by the land surfaces of the Earth, from a continual energy input to the upper atmosphere of

1.8 x 1017 W. When we compare this with the total energy requirement of humanity (excluding food and wood) of 1.3 x 105 TWh/yr, wefind that there is a sufficient amount of sunlight reaches the land in 6 hours capable of supplying the humanitys energy needs for onewhole year.

The Advantages of Solar Energy Production20There are significant advantages to solar energy production. Clean Energy Ideas have provided an exhaustive list of some of these

advantages which I would like to highlight here. The first advantage has to do with the fact that solar energy production is environmentallyfriendly. During their operation solar panels do not produce any pollution. The only pollution connected with solar panels may be associatewith the process of their manufacture, transportation and manufacture. This is a very significant advantage for the use of solar panels sincit not only limits the utilisation of the diminishing supply of fossil fuels in energy generation but as a consequence instantly eliminates all thdevastating environmental effects that the latter have had and continue to have.

The second advantage of solar panels, as illustrated by Clean Energy Ideas, is their convenience. To begin with, solar panels operatvery quietly and, as such, do not contribute to noise pollution. Secondly, electricity can be generated using solar panels in remote locationthat are not linked to a national grid. An important example of such location is space, where satellites are powered by high efficiency solacells. An added benefit of the installation of solar panels in remote locations is that such panels are usually much more cost effective sincthe laying of required high voltage wires is not required. Similarly, solar panels can be installed on rooftops, which eliminate the problem ofinding the required space for solar panel placement. Solar energy can be very efficiently produced over a large area of the globe, and newtechnologies will allow for a more efficient energy production on overcast days. Finally, solar panels are financially convenient as welDespite the fact that the initial investment of solar cells may be high, once installed, they will provide a free source of electricity, which wpay off over the coming years.

Cons of Solar Energy21The major obstacle to the adoption of solar energy is the initial cost of solar cells. Currently, prices of highly efficient solar cells can be

above $1000, and some households may need more than one. This makes the initial installation of solar panels very costly. Solar energy isonly able to generate electricity during daylight hours. This means for around half of each day, solar panels are not producing energy for ahome requiring power storage batteries, which can take up private space. Equally important is the effect of the inconstancy of weather. Thweather patterns directly affect the efficiency of solar cells and areas with low sunlight or high cloud cover wont utilize solar panelsefficiently. Due to the fact that significant levels of atmospheric pollution can interfere with the level of sunlight received by the solarpanels, there is an inevitable risk of inefficiency in heavily polluted areas such as large cities and urban centres.


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Author:Dennis OriaiResearch Analyst, Sun Strides Foundation

Citation

1-2.Africa's natural resources key to powering prosperity. May 2008. pg 3

www.grida.no/_res/site/file/publications/povertty-times-05_screen.pdf

3-8.Abdoulaye M. Yansane. National Solar Power Research Institute, Inc.

http://userwww.sfsu.edu/~ciotola/solar/asn_94nuclear.html

9.Matthias Loster. Total Primary Energy Supply.

http://www.ez2c.de/ml/solar_land_area/

10-15, 17.Solar Panel Information (SPI). How Do Solar Panels Work.

http://www.solarpanelinfo.com

16.SANYO Develops Ultra-thin HIT Solar Cell with the World's Highest-level Conversion Efficiency of 22.8%

http://sanyo.com/news/2009/09/18-1.html

18.The Solar Electric Option. A joint Publication of the Arizona Corporation Commission and the Arizona Department of Commerce Energy Office.

http://publicservice.vermont.gov/energy-efficiency/ee_files/solar/the_solarelectric_option.pdf

19.Help Save the Climate (HSC). How Much Energy Does the Sun Provide?

http://www.helpsavetheclimate.com/solar.html

20.Clean Energy Ideas. The Pros and Cons of Solar Energy.

http://www.clean-energy-ideas.com/articles/pros_and_cons_of_solar_energy.html

Wind Energy

An Introduction to Wind Power GenerationThe conversion of wind power into forms of energy which can be used to power everyday, home appliances is one of the most attractive

solutions from environmental and ecological perspectives. Of similar importance is the fact that wind power generation is a sustainable and

economically advantageous form of energy generation. There is a general consensus among scientists that widespread reliance on fossilfuels, and the resulting high-levels of pollution, has contributed to global climate change. This global climate change has the potential forcausing an adverse environmental impact, as well as possibly contributing to a significant loss of human lives in the future. As a result, thecapability to generate power from a clean source of energy such as wind is an important technological development. Moreover, apart fromthe self-evident environmental benefits of wind power, it should be emphasized that in economic terms it is also a cost-competitive energyresource. For example, research within the United States Department of Energy has shown that the cost of wind power generation acrossthe nation has fallen from 25 cents/kWh in 1981 to an average of 4 cents/kWh in 2008, with half of the projects being conducted in therange of 3.3 to 5.2 cents/kWh, including the federal production tax credit.

A Case Study: Wind Power Generation in AfricaGiven the advantageous nature of wind power generation, particularly in economic terms, it presents an important answer to some of

the current energy problems facing the African climate. Despite the fact that levels of technological development are not uniform across thcontinent, several African countries have inadequate and intermittent provisions of power. This suggests a pressing need for a viablealternative to the conventional forms of power generation to be implemented on the continent. Despite the prima facie attractiveness of

wind power development on the African continent it should be noted that natural obstacles to such realisation will remain. The Africancontinent has a much lower wind resource due to the continents average low altitude as well the atmospheric heating caused by itsproximity to the equator1. However, two factors make the rapid expansion of wind power production a viable and important substitute tofossil fuels. The first factor is the relatively low economic cost of generating energy from wind. The second factor is that the rapid growthand global momentum of the wind power industry makes it an alternative energy source of energy which may be disadvantageous toignore. It has been estimated that the global, infrastructural capacity for wind power generation has increased by 36% in the 2007-2008period, which accounts for a potential generation of an additional 27,000 megawatts (MW) of power across the globe, as well as shows aninfusion of $51.5 billion into the wind power industry2. Such a significantly large increase in global investments will ultimately increase theefficiency and cost competitiveness of the global wind industry, thereby making it a very attractive power generating source for Africancountries.

How Wind Power WorksAt this point of our introduction to wind power generation, it may be useful to go over some of the details involved in the process. In th

case of wind power generation, there is a direct and proportional relationship between the wind conditions, such as strength and frequency

and the amount of power that is generated. This means that in any instance an increase in the strength and frequency of the wind there


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will be a corresponding increase in power produced by the wind turbines. The relationship between the wind speed and the powergenerated is also proportional in a ratio of 1:3. For every increase in the speed of the wind, there will be a three-fold increase in the poweroutput, which means that a doubling of the wind speed will increase power output by eight times 3 . This fact demonstrates that theutilization of wind power generating turbines at specific times when there is a notable and recurring presence of higher-wind speeds has aclear economic advantage. As a result, the practical consideration of seasonal and daily variations prior to installation will ensure optimumpower yields for the wind turbines.

Due to the determining influence of wind speed on the corresponding wind power, a classification of wind speeds has been constructedWind speeds are classified into seven classes in a continuous gradation from class one, which is the lowest class, to the highest, which isclass seven. The calculation of wind speeds is usually undertaken by a wind resource assessment team. This team makes their estimatesbased on the recorded, average wind speeds above a section of land. These estimates are used to determine the wind class that is to beassigned to the area under consideration4.

This estimation of wind speed, and the corresponding ranking according to wind class, has its first practical significance in its relation tothe operational capability of the wind turbines. The technical particularity of the wind turbines resides in the fact that they only operate ovea limited range of speeds. The implication of this feature of the wind turbines is that their performance or lack of performance is to asignificant extent determined by the wind speed in a particular area. For example, a wind with a low speed may not be able to turn thewind turbines, while in the presence of a strong wind the turbines may have to be shut down in order to avoid structural damage5. Thesecond practical significance of the classification according to wind class is that it clearly demarcates the range of wind speeds that aremost suitable for generating sufficient quantities of power for public consumption. In this respect, it has been noted that wind speeds inclasses three and above, that is, those wind speeds which are in the range of 6.7 7.4 meters per second m/s and above, are typicallymost suited to power production on a scale that can satisfy the basic needs of potential consumers6. It follows from the precedingconsideration that in order to maximize the production of power, there is a strong preference for the construction of wind turbines on siteswhich have an abundant supply of the higher wind classes. I have included a table below which shows the wind class ranking, a categorywhich is known as the wind power density, and the ranges of wind speeds corresponding to each wind class.

Classes of Wind Power Density at Heights of 10m and 50m

Several important features of the wind power generation process can be summarised from the table shown above. The table provides asummary of the estimates of the different ranges of wind speeds and links them to the particular wind classes and elevation. The table alsointroduces the concept of the Wind Power Density (WPD) mentioned above which provides an estimate of the wind energy per unit areawhich can be generated from the wind resource in a specific site. This means that it is possible to determine, in watts per square meter, thspecific power productivity of turbines located at different sites. This WPD range is specified with respect to the elevation above the groundof a specific site: at a relatively low elevation of 10 meters above the ground and its lower wind speed to the higher elevat ion of 50 meterswith its correspondingly larger wind speeds. It can be observed that the wind speeds tend to increase with a greater level of elevation.


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The 'specific yield' is a term that is used to describe the annual energy output per square meter of area swept by the turbine blades asthey rotate 8. The current conversion rate of wind power to electricity stands at 40 per cent. At sites with average wind speeds of sevenm/s, a typical turbine will produce about 1,100 kilowatt-hours (kWh) per square meter of area per year. The production of power is directlyrelated to the length of the turbine blades. For example, provided that a turbine has blades that are 40 meters long, with a total swept areof 5,029 square meters, the power output will be about 5.5 million kWh for the year. This means that an increase in blade length, and acorresponding increase in the total swept area, will have a significant effect on the energy per square meter swept by the turbine blades 9.As a result, the technical features of the wind turbines are very important in the consideration of the amount of power that a specific siteneeds to generate for its consumers.

Other Technical Features of the Wind TurbinesUnder external observation, it can be shown that horizontal axis wind turbines consist of three big parts: the tower, the blades, and a

box behind the blades which is called the nacelle. The nacelle is a central feature of the wind turbine. It is responsible for the wind turbinegeneral function of converting the motion caused by the wind resource at a specific site into electricity. Large turbines don't have tail fans-they have hydraulic controls that orient the blades into the wind in the place of the tail fans 10 . In the most typical design, the blades areattached to an axle that runs into a gearbox. The gearbox, or transmission, steps up the speed of the rotation, usually from about 50 rpmup to 1,800 rpm. The faster spinning shaft spins inside the generator which produces AC electricity 11. Electricity must be produced at justthe right frequency and voltage to be compatible with a utility grid 12. Since the wind speed varies, the corresponding variable speed of thegenerator can produce fluctuations in the electricity. One solution to this problem is to have constant speed turbines, where the bladesadjust, by turning slightly to the side, in order to slow down when wind speeds are particularly high. Another potential solution is to usevariable-speed turbines, where the blades and a generator change speeds in accordance with the wind conditions. Such variable-speedwind turbines use sophisticated power controls to fix the fluctuations of the electrical output. A third approach is to use low-speedgenerators.

Specifications of Wind TurbinesModern electric wind turbines come in a few different styles and many different sizes, depending on their use. The most common style,

irrespective of the size of the turbine is the "horizontal axis design", that is, with the axis of the blades being horizontal to the ground. Interms of size, small wind turbines are generally used for providing power off the grid: these range from highly compact 250-watt turbinesdesigned for charging up batteries on a sailboat, to 50-kilowatt turbines that power dairy farms and remote villages. Large wind turbinesare mostly used by utility companies to provide power to a grid system. Usually, turbines in this size range have a markedly large range ofpower provision: they can provide anything from 250 KW to the 3.5 to 5 MW, the latter representing the performance of significantly bulkiewind turbines which are located for use offshore. It has been estimated that in 2008, the average land-based wind turbines had a capacityof 1.67 MW 13. These different types of wind turbines are usually placed in groups in known windy locationsA collection of such wind "farms" can consist of a few or hundreds of turbines, providing enough power for tens of thousands of homes 14.

Advantages of Wind Energy15Zero emissions- There is no emission of CO2, sulphur, nitrogen oxide, particulates, trace metals, or solid waste as opposed to thetraditional reliance on fossil fuels. This means that the implementation of wind energy production can have a marked impact on humancaused global warming and the acid rain, pollution, asthma, and other negative environmental/health consequences that this is known toproduce.Renewable- Wind is in constant supply. This has an advantage over alternative sources of energy such as coal, oil, and gas, whose supplymay significantly diminish in the future.Free- Because wind is an abundant natural resource without the need for processing, it can power production with operational costs whichare effectively zero.Declining costs- As installed capacity has increased, costs have dropped 85% in 15 years to


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Author:

Dennis OriaifoResearch Analyst, Sun Strides Foundation

Citation:

1.Graham Richard, Michael. Enercon E-126: The Worlds Largest Wind Turbine (For Now).http://www.treehugger.com/files/2008/02/enercon_e126_largest_wind_turbine.php

2.Global Wind Energy Council (GWEC). 2008. Global Wind 2008 Report Onlinehttp://www.gwec.net/index.php?id=153

3.US Department of Energy, Office of Energy Efficiency and Renewable Energy. 2009 20 Percent Wind Energy by 2030: Increasing Wind Energys Contribution to US Electricity Supply

http://www.20percentwind.org/20percent_wind_energy_report_revOct08.pdf 44.Afriwea. There is Wind in Africa! Published in African Development Bank (ADP FINESSE Africa newsletter, August 2004)

http://www.afriwea.org/en/summary.htm

5.UCSUSA. How Wind Energy Works.

http://www.ucsusa.org/clean_energy/technology_and_impacts/energy_technologies/how-wind-energy-works.html

6.Health link. Wind Pros and Cons, Myths and Misconceptionshttp://www.citizensinaction.org/windproscons37.html

Resources

Science in Africa: Africa's First On-Line Science Magazine

Alternative Energy: Africa

Alternative Energy: Alternative energy news and information resources about renewable energy technologies

Africa News: The largest network of African reporters

Renewable Energy Focus

Wind Energy News

Interesting energy facts: Interesting facts about energy sources, energy news, and energy articles

Country Profiles

TradeInvest Africa

African Wind Energy Association

Articles

Alternative Energy: Small Wind Farm Ready to Generate Power

Alternative Energy: African Solar Could Power all of Europe

Solve Climate: Solar Power From Africa, The Best Investment the EU Can Make

AllAfrica: Africa, Electricity Access Projected to Worsen

Afrik: GE considers investing in wind energy in Africa

EUREC Agency: Various

Energy in Africa: Chapter 7, Environment and Renewable

Alternative Energy Country Analysis

U.S. Energy Information Administration, Independent Statistics and Analysis: Country Analysis Briefs
http://www.scienceinafrica.co.za/index.htmhttp://www.scienceinafrica.co.za/index.htmhttp://www.ae-africa.com/http://www.ae-africa.com/http://www.alternative-energy-news.info/http://www.alternative-energy-news.info/http://www.africanews.com/http://www.africanews.com/http://www.windenergynews.com/http://www.windenergynews.com/http://interestingenergyfacts.blogspot.com/http://interestingenergyfacts.blogspot.com/http://www.tradeinvestafrica.com/http://www.tradeinvestafrica.com/http://www.afriwea.org/en/country.htmhttp://www.afriwea.org/en/country.htmhttp://www.alternative-energy-news.info/small-wind-farm-ready-to-generate-power/http://www.alternative-energy-news.info/small-wind-farm-ready-to-generate-power/http://www.alternative-energy-news.info/african-solar-power-europe/http://www.alternative-energy-news.info/african-solar-power-europe/http://solveclimate.com/blog/20080421/solar-power-africa-best-investment-eu-can-makehttp://solveclimate.com/blog/20080421/solar-power-africa-best-investment-eu-can-makehttp://allafrica.com/stories/200912100768.htmlhttp://allafrica.com/stories/200912100768.htmlhttp://en.afrik.com/article13587.htmlhttp://en.afrik.com/article13587.htmlhttp://www.eurec.be/htm/projects/PISA%20II/Press%20Releases.htmhttp://www.eurec.be/htm/projects/PISA%20II/Press%20Releases.htmhttp://www.eia.doe.gov/emeu/cabs/chapter7.htmlhttp://www.eia.doe.gov/emeu/cabs/chapter7.htmlhttp://www.eia.doe.gov/emeu/cabs/Region_af.htmlhttp://www.eia.doe.gov/emeu/cabs/Region_af.htmlhttp://www.eia.doe.gov/emeu/cabs/Region_af.htmlhttp://www.eia.doe.gov/emeu/cabs/chapter7.htmlhttp://www.eurec.be/htm/projects/PISA%20II/Press%20Releases.htmhttp://en.afrik.com/article13587.htmlhttp://allafrica.com/stories/200912100768.htmlhttp://solveclimate.com/blog/20080421/solar-power-africa-best-investment-eu-can-makehttp://www.alternative-energy-news.info/african-solar-power-europe/http://www.alternative-energy-news.info/small-wind-farm-ready-to-generate-power/http://www.afriwea.org/en/country.htmhttp://www.tradeinvestafrica.com/http://interestingenergyfacts.blogspot.com/http://www.windenergynews.com/http://www.africanews.com/http://www.alternative-energy-news.info/http://www.ae-africa.com/http://www.scienceinafrica.co.za/index.htm


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INTRODUCTION

(Image courtesy of NASA)

Our contemporary society is heavily dependent on the provision of energy, in particular in the form of electricity. Despite many nationand international efforts aimed at making energy provision accessible in most parts of the world, more than two billion people in the wordo not have access to affordable energy services today. A significant majority of such people reside on the African Continent. One of thkey problems facing African energy supply has to do with the inability of local governments to efficiently perform both the collection o

biomass material such as crop residues or wood and the conversion of these materials into fuels1. The problem of energy supply haimportant repercussions for the socio-economic level of African countries. This is evidenced in the fact a convenient, affordable energstimulates households marginal productivity, as a result enabling households, and even whole communities, to escape poverty and begtheir socio-economic development 2. It becomes evident that developing a dependable energy sector in African countries is a very importangoal.

The challenge of developing Africas energy sector is particularly difficult. At present, Africa as a continent produces less than 1% of thworld total electricity supply. Apart from the general scarcity of infrastructure in order to maintain an adequate level of electricity supplythere is an additional problem of the inefficiency of its provision where such infrastructure exists. In fact, countries in Africa undergo regulaelectricity outages which can last in duration from just a few hours to a succession of several days. This intermittent level of electricitsupply can be attributed to an inefficient and generally out of date infrastructure. Many of the electrical power stations date back to theinstallation during the colonial era. The severe problem in technical efficiency has been compounded by endemic poverty and the lack good management of funds allocated for the maintenance of existing power stations. In view of such problems and an urgent need tdevelop the energy sector in Africa, the provision energy derived from alternative energy sources is very attractive, especially now amidthe growing environmental concerns and increasingly competitive prices of alternative energy.

SOLARThere are several reasons why the provision of solar energy is particularly suitable to the African continent. The continents latitude and

the proximity of its land mass to the equator means that it benefits from constant and strong intensity of sunlight all year round, therebyshowing striking solar energy production capabilities3. The general availability of sunlight means African countries have a potentially costlessource of energy production. Unlike other forms of energy generation, solar energy can be harnessed for free. This means that it will notmake any demands on the already strained financial resources available on the African continent. Hence, the provision of capita for thelarge-scale infrastructural developments of complex power grids will not be necessary. Secondly, the relatively high level of sunlight in allAfrican countries means that any location on the continent can benefit from solar energy supply.

There are other implications of the need to change to solar energy production in Africa. It has been noted above that Africa generateless that 1% of the worlds total electricity. This energy generation is primarily achieved through nuclear power plants, whose rapid growton the continent since the mid-1980s had not brought a proportionate increase in the total output of electricity on the continent 4. Thproblem of nuclear power plants is also connected with the problems of provision of petroleum necessary for their functioning 5. It is wedocumented fact that the extraction, refining and the utilization of petroleum in the transport industry causes significant environmentaproblems through pollution. Solar energy production can significantly lower the environmental impact of the present forms of energgeneration in Africa. At the same time, Africas documented petroleum reserves of 60 billion barrels will not able to meet al l the energdemands of the African pollution in the long run6. Therefore, there exists a strong demand to promote and develop an alternative source oenergy production. The generation of energy from solar power can have the double advantage of keeping the commendably low levels oindustrial pollution while initiating a certain resource boom in the form of higher labour demand7.


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(Image courtesy of Center for energy and processes, Ecole des Mines de Paris/Armines/CNRS)

With reference to the map above, it has been estimated that the solar power systems if installed in the red areas, that is thosecorresponding to the North-West USA, Chile, Argentina, North Africa, Saudi Arabia and China, could meet the world's current total primaryenergy demand, with a certain surplus of energy, with a conversion efficiency of 8 per cent8. This can be shown in quantitative terms. Forexample, photovoltaic systems, with conversion efficiency of 8 percent, if installed in the red areas discussed above would produce anaverage electric output of 18TWe. This figure corresponds to an energy output of 13,567 Mtoe per year. Such projected output is larger

that the world electric output of 11, 741 produced in 20069. This effectively means, as the analysis by Yansane indicates, that electricityprovided by solar cells can be gainfully substituted for other forms of energy production, while successfully providing for all the daily needsassociated with energy consumption. These facts indicate quite clearly the potential that solar powered electricity generation systems haveeven at the current stage of its technological development.

How Solar Panels Work

Solar panels collect solar radiation from the sun and actively convert that energy into electricity. Solar panels are comprised of severindividual solar cells10. The functioning of these solar cells can be compared to the similar functioning of large semiconductors. The solacells utilize a large-area p-n junction diode11. When the solar cells are exposed to sunlight, the p-n junction diodes convert the energy frosunlight into usable electrical energy12. The energy generated from photons striking the surface of the solar panel allows electrons to bknocked out of their orbits and released; the electric fields in the solar cells pull these free electrons in a directional current, from whic

metal contacts in the solar cell can generate electricity13

. A larger number of solar cells in a solar panel and the higher the quality of thsolar cells, the greater will be the total electrical output that the solar panel can produce14. This conversion of sunlight to usable electricenergy has been dubbed the Photovoltaic Effect15. It has been reported that as of May 2009 the solar energy industry's highest conversioefficiency of solar panel stands at 22.8 percent16.

There are various crucial factors which have to be considered when designing and operating solar panels for energy generation. One ofthe central features for the design of solar panels has to do with its ability to provide electricity during the absence of sunlight. The fact thathe amount of electric current generated by a solar cell is directly proportional to the intensity of sunlight shows the importance of such adesign feature. For it is self-evident that there will be times when the absence of sunlight is quite pronounced, such as when there is aheavy cloud cover or during night time. At such periods, no electricity can be generated unless stored energy from sunlight is available forelectricity generation. Consequently, a photovoltaic energy storage system is required. The most common of which are batteries equippedwith a voltage regulator to prevent an overcharge of batteries.


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When operating solar panels, their efficiency can be optimized by using movable mounts that follow the position of the sun in the skyThis is important since one of the central features of the solar panels is their direct dependence of their performance on the amount osunlight received. Rotation of the dynamic mounts has the advantage of increasing the solar panel efficiency, and hence its electricioutput, by enabling the solar panel to get the maximum amount of direct exposure to sunlight17.

Choosing the right system18Determining the size of the photovoltaic system is crucial. If system design is undersized, this will result in the undergeneration of

electricity. Conversely if the system is over sized, this will result in excess capacity and will represent an unnecessary expenditure offinancial resources. The PV system design starts with a definition of the electrical loads. The initial system cost will be d irectly proportionalto the amount of energy that the system is designed to provide. The electrical load is directly proportional to the electrical consumption ofappliances which use the generated power. Consequently, a reduction of the load requirement (kWh) by 50 per cent will lead to a price

reduction of the PV system by 50 per cent, thereby saving a substantial amount of capital for the potential investor.

The potential costs of running a solar panel system can be illustrated below:

The daily load can be calculated as follows:

Daily Load = Watts used by appliances x Time in use

In order to determine an approximate cost of a photovoltaic system to power the total daily load, various types of the photovoltaic (PV)system have to be taken into account. Provided that the PV system is simple, the total daily load has to be multiplied by three. Similarly, ifthe system is typical, then it should be multiplied by four and when it is complex, it should be multiplied by five. Let us say that a simplephotovoltaic cell generates 500 watt-hours per day. Then we can determine the approximate cist of such system will be represented by500x3 that amounts to $1500.

Solar Energy19About 1.9 x 108 TWh per year is absorbed by the land surfaces of the Earth, from a continual energy input to the upper atmosphere of

1.8 x 1017 W. When we compare this with the total energy requirement of humanity (excluding food and wood) of 1.3 x 105 TWh/yr, wefind that there is a sufficient amount of sunlight reaches the land in 6 hours capable of supplying the humanitys energy needs for onewhole year.

The Advantages of Solar Energy Production20There are significant advantages to solar energy production. Clean Energy Ideas have provided an exhaustive list of some of these

advantages which I would like to highlight here. The first advantage has to do with the fact that solar energy production is environmentallyfriendly. During their operation solar panels do not produce any pollution. The only pollution connected with solar panels may be associatewith the process of their manufacture, transportation and manufacture. This is a very significant advantage for the use of solar panels sincit not only limits the utilisation of the diminishing supply of fossil fuels in energy generation but as a consequence instantly eliminates all thdevastating environmental effects that the latter have had and continue to have.

The second advantage of solar panels, as illustrated by Clean Energy Ideas, is their convenience. To begin with, solar panels operatvery quietly and, as such, do not contribute to noise pollution. Secondly, electricity can be generated using solar panels in remote locationthat are not linked to a national grid. An important example of such location is space, where satellites are powered by high efficiency solacells. An added benefit of the installation of solar panels in remote locations is that such panels are usually much more cost effective sincthe laying of required high voltage wires is not required. Similarly, solar panels can be installed on rooftops, which eliminate the problem ofinding the required space for solar panel placement. Solar energy can be very efficiently produced over a large area of the globe, and newtechnologies will allow for a more efficient energy production on overcast days. Finally, solar panels are financially convenient as welDespite the fact that the initial investment of solar cells may be high, once installed, they will provide a free source of electricity, which wpay off over the coming years.

Cons of Solar Energy21

The major obstacle to the adoption of solar energy is the initial cost of solar cells. Currently, prices of highly efficient solar cells can beabove $1000, and some households may need more than one. This makes the initial installation of solar panels very costly. Solar energy isonly able to generate electricity during daylight hours. This means for around half of each day, solar panels are not producing energy for ahome requiring power storage batteries, which can take up private space. Equally important is the effect of the inconstancy of weather. Thweather patterns directly affect the efficiency of solar cells and areas with low sun light or high cloud cover wont utilize solar panelsefficiently. Due to the fact that significant levels of atmospheric pollution can interfere with the level of sunlight received by the solarpanels, there is an inevitable risk of inefficiency in heavily polluted areas such as large cities and urban centres.

Author:Dennis OriaiResearch Analyst, Sun Strides Foundation

Citation


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1-2.Africa's natural resources key to powering prosperity. May 2008. pg

www.grida.no/_res/site/file/publications/povertty-times-05_screen.pdf

3-8.Abdoulaye M. Yansane. National Solar Power Research Institute, In

http://userwww.sfsu.edu/~ciotola/solar/asn_94nuclear.html

9.Matthias Loster. Total Primary Energy Supp

http://www.ez2c.de/ml/solar_land_area/

10-15, 17.Solar Panel Information (SPI). How Do Solar Panels Wo

http://www.solarpanelinfo.com

16.SANYO Develops Ultra-thin HIT Solar Cell with the World's Highest-level Conversion Efficiency of 22.8

http://sanyo.com/news/2009/09/18-1.html

18.The Solar Electric Option. A joint Publication of the Arizona Corporation Commission and the Arizona Department of Commerce Energy Offic

http://publicservice.vermont.gov/energy-efficiency/ee_files/solar/the_solarelectric_option.pdf

19.Help Save the Climate (HSC). How Much Energy Does the Sun Provid

http://www.helpsavetheclimate.com/solar.html

20.Clean Energy Ideas. The Pros and Cons of Solar Energ

http://www.clean-energy-ideas.com/articles/pros_and_cons_of_solar_energy.html

Wind Energ

An Introduction to Wind Power GeneratioThe conversion of wind power into forms of energy which can be used to power everyday, home appliances is one of the most attractiv

solutions from environmental and ecological perspectives. Of similar importance is the fact that wind power generation is a sustainable aneconomically advantageous form of energy generation. There is a general consensus among scientists that widespread reliance on fossfuels, and the resulting high-levels of pollution, has contributed to global climate change. This global climate change has the potential focausing an adverse environmental impact, as well as possibly contributing to a significant loss of human lives in the future. As a result, thcapability to generate power from a clean source of energy such as wind is an important technological development. Moreover, apart frothe self-evident environmental benefits of wind power, it should be emphasized that in economic terms it is also a cost-competitive energresource. For example, research within the United States Department of Energy has shown that the cost of wind power generation acrosthe nation has fallen from 25 cents/kWh in 1981 to an average of 4 cents/kWh in 2008, with half of the projects being conducted in thrange of 3.3 to 5.2 cents/kWh, including the federal production tax credit

A Case Study: Wind Power Generation in AfricGiven the advantageous nature of wind power generation, particularly in economic terms, it presents an important answer to some

the current energy problems facing the African climate. Despite the fact that levels of technological development are not uniform across thcontinent, several African countries have inadequate and intermittent provisions of power. This suggests a pressing need for a viabalternative to the conventional forms of power generation to be implemented on the continent. Despite the prima facie attractiveness owind power development on the African continent it should be noted that natural obstacles to such realisation will remain. The Africacontinent has a much lower wind resource due to the continents average low altitude as well the atmospheric heating caused b y iproximity to the equator1. However, two factors make the rapid expansion of wind power production a viable and important substitute tfossil fuels. The first factor is the relatively low economic cost of generating energy from wind. The second factor is that the rapid growtand global momentum of the wind power industry makes it an alternative energy source of energy which may be disadvantageous tignore. It has been estimated that the global, infrastructural capacity for wind power generation has increased by 36% in the 2007-200period, which accounts for a potential generation of an additional 27,000 megawatts (MW) of power across the globe, as well as shows ainfusion of $51.5 billion into the wind power industry2. Such a significantly large increase in global investments will ultimately increase thefficiency and cost competitiveness of the global wind industry, thereby making it a very attractive power generating source for Africacountries.

How Wind Power Works

At this point of our introduction to wind power generation, it may be useful to go over some of the details involved in the process. In thcase of wind power generation, there is a direct and proportional relationship between the wind conditions, such as strength and frequencand the amount of power that is generated. This means that in any instance an increase in the strength and frequency of the wind therwill be a corresponding increase in power produced by the wind turbines. The relationship between the wind speed and the powegenerated is also proportional in a ratio of 1:3. For every increase in the speed of the wind, there will be a three-fold increase in the poweoutput, which means that a doubling of the wind speed will increase power output by eight times 3 . This fact demonstrates that thutilization of wind power generating turbines at specific times when there is a notable and recurring presence of higher-wind speeds has clear economic advantage. As a result, the practical consideration of seasonal and daily variations prior to installation will ensure optimupower yields for the wind turbines

Due to the determining influence of wind speed on the corresponding wind power, a classification of wind speeds has been constructedWind speeds are classified into seven classes in a continuous gradation from class one, which is the lowest class, to the highest, which iclass seven. The calculation of wind speeds is usually undertaken by a wind resource assessment team. This team makes their estimatebased on the recorded, average wind speeds above a section of land. These estimates are used to determine the wind class that is to b

assigned to the area under consideration

4

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This estimation of wind speed, and the corresponding ranking according to wind class, has its first practical significance in its relation tthe operational capability of the wind turbines. The technical particularity of the wind turbines resides in the fact that they only operate ovea limited range of speeds. The implication of this feature of the wind turbines is that their performance or lack of performance is to significant extent determined by the wind speed in a particular area. For example, a wind with a low speed may not be able to turn thwind turbines, while in the presence of a strong wind the turbines may have to be shut down in order to avoid structural damage 5. Thsecond practical significance of the classification according to wind class is that it clearly demarcates the range of wind speeds that armost suitable for generating sufficient quantities of power for public consumption. In this respect, it has been noted that wind speeds classes three and above, that is, those wind speeds which are in the range of 6.7 7.4 meters per second m/s and above, are typicalmost suited to power production on a scale that can satisfy the basic needs of potential consumers 6. It follows from the precedinconsideration that in order to maximize the production of power, there is a strong preference for the construction of wind turbines on sitewhich have an abundant supply of the higher wind classes. I have included a table below which shows the wind class ranking, a categowhich is known as the wind power density, and the ranges of wind speeds corresponding to each wind class

Classes of Wind Power Density at Heights of 10m and 50m

Several important features of the wind power generation process can be summarised from the table shown above. The table provides summary of the estimates of the different ranges of wind speeds and links them to the particular wind classes and elevation. The table alsintroduces the concept of the Wind Power Density (WPD) mentioned above which provides an estimate of the wind energy per unit arewhich can be generated from the wind resource in a specific site. This means that it is possible to determine, in watts per square meter, thspecific power productivity of turbines located at different sites. This WPD range is specified with respect to the elevation above the groun

of a specific site: at a relatively low elevation of 10 meters above the ground and its lower wind speed to the higher elevation of 50 metewith its correspondingly larger wind speeds. It can be observed that the wind speeds tend to increase with a greater level of elevation

The 'specific yield' is a term that is used to describe the annual energy output per square meter of area swept by the turbine blades athey rotate 8. The current conversion rate of wind power to electricity stands at 40 per cent. At sites with average wind speeds of sevem/s, a typical turbine will produce about 1,100 kilowatt-hours (kWh) per square meter of area per year. The production of power is directlrelated to the length of the turbine blades. For example, provided that a turbine has blades that are 40 meters long, with a total swept areof 5,029 square meters, the power output will be about 5.5 million kWh for the year. This means that an increase in blade length, and corresponding increase in the total swept area, will have a significant effect on the energy per square meter swept by the turbine bladesAs a result, the technical features of the wind turbines are very important in the consideration of the amount of power that a specific sitneeds to generate for its consumers

Other Technical Features of the Wind TurbineUnder external observation, it can be shown that horizontal axis wind turbines consist of three big parts: the tower, the blades, and

box behind the blades which is called the nacelle. The nacelle is a central feature of the wind turbine. It is responsible for the wind turbine

general function of converting the motion caused by the wind resource at a specific site into electricity. Large turbines don't have tail fans


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they have hydraulic controls that orient the blades into the wind in the place of the tail fans 10 . In the most typical design, the blades arattached to an axle that runs into a gearbox. The gearbox, or transmission, steps up the speed of the rotation, usually from about 50 rpmup to 1,800 rpm. The faster spinning shaft spins inside the generator which produces AC electricity 11. Electricity must be produced at juthe right frequency and voltage to be compatible with a utility grid 12. Since the wind speed varies, the corresponding variable speed of thgenerator can produce fluctuations in the electricity. One solution to this problem is to have constant speed turbines, where the bladeadjust, by turning slightly to the side, in order to slow down when wind speeds are particularly high. Another potential solution is to usvariable-speed turbines, where the blades and a generator change speeds in accordance with the wind conditions. Such variable-speewind turbines use sophisticated power controls to fix the fluctuations of the electrical output. A third approach is to use low-speegenerators.

Specifications of Wind TurbineModern electric wind turbines come in a few different styles and many different sizes, depending on their use. The most common style

irrespective of the size of the turbine is the "horizontal axis design", that is, with the axis of the blades being horizontal to the ground. Iterms of size, small wind turbines are generally used for providing power off the grid: these range from highly compact 250-watt turbinedesigned for charging up batteries on a sailboat, to 50-kilowatt turbines that power dairy farms and remote villages. Large wind turbineare mostly used by utility companies to provide power to a grid system. Usually, turbines in this size range have a markedly large range opower provision: they can provide anything from 250 KW to the 3.5 to 5 MW, the latter representing the performance of significantly bulkiewind turbines which are located for use offshore. It has been estimated that in 2008, the average land-based wind turbines had a capacitof 1.67 MW 13. These different types of wind turbines are usually placed in groups in known windy locationA collection of such wind "farms" can consist of a few or hundreds of turbines, providing enough power for tens of thousands of homes 14

Advantages of Wind EnergyZero emissions- There is no emission of CO2, sulphur, nitrogen oxide, particulates, trace metals, or solid waste as opposed to thtraditional reliance on fossil fuels. This means that the implementation of wind energy production can have a marked impact on humacaused global warming and the acid rain, pollution, asthma, and other negative environmental/health consequences that this is known t

produce.Renewable- Wind is in constant supply. This has an advantage over alternative sources of energy such as coal, oil, and gas, whose suppmay significantly diminish in the futureFree- Because wind is an abundant natural resource without the need for processing, it can power production with operational costs whicare effectively zeroDeclining costs- As installed capacity has increased, costs have dropped 85% in 15 years to


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http://www.20percentwind.org/20percent_wind_energy_report_revOct08.pdf 44.

Afriwea. There is Wind in Africa! Published in African Development Bank (ADP FINESSE Africa newsletter, August 20

http://www.afriwea.org/en/summary.htm

5.UCSUSA. How Wind Energy Wor

http://www.ucsusa.org/clean_energy/technology_and_impacts/energy_technologies/how-wind-energy-works.html

6.Health link. Wind Pros and Cons, Myths and Misconceptionshttp://www.citizensinaction.org/windproscons37.html

Resources

Science in Africa: Africa's First On-Line Science Magazine

Alternative Energy: Africa

Alternative Energy: Alternative energy news and information resources about renewable energy technologies

Africa News: The largest network of African reporters

Renewable Energy Focus

Wind Energy News

Interesting energy facts: Interesting facts about energy sources, energy news, and energy articles

Country Profiles

TradeInvest Africa

African Wind Energy Association

Articles

Alternative Energy: Small Wind Farm Ready to Generate Power

Alternative Energy: African Solar Could Power all of Europe

Solve Climate: Solar Power From Africa, The Best Investment the EU Can Make

AllAfrica: Africa, Electricity Access Projected to Worsen

Afrik: GE considers investing in wind energy in Africa

EUREC Agency: Various

Energy in Africa: Chapter 7, Environment and Renewable

Alternative Energy Country Analysis

U.S. Energy Information Administration, Independent Statistics and Analysis: Country Analysis Briefs
http://www.scienceinafrica.co.za/index.htmhttp://www.scienceinafrica.co.za/index.htmhttp://www.ae-africa.com/http://www.ae-africa.com/http://www.alternative-energy-news.info/http://www.alternative-energy-news.info/http://www.africanews.com/http://www.africanews.com/http://www.windenergynews.com/http://www.windenergynews.com/http://interestingenergyfacts.blogspot.com/http://interestingenergyfacts.blogspot.com/http://www.tradeinvestafrica.com/http://www.tradeinvestafrica.com/http://www.afriwea.org/en/country.htmhttp://www.afriwea.org/en/country.htmhttp://www.alternative-energy-news.info/small-wind-farm-ready-to-generate-power/http://www.alternative-energy-news.info/small-wind-farm-ready-to-generate-power/http://www.alternative-energy-news.info/african-solar-power-europe/http://www.alternative-energy-news.info/african-solar-power-europe/http://solveclimate.com/blog/20080421/solar-power-africa-best-investment-eu-can-makehttp://solveclimate.com/blog/20080421/solar-power-africa-best-investment-eu-can-makehttp://allafrica.com/stories/200912100768.htmlhttp://allafrica.com/stories/200912100768.htmlhttp://en.afrik.com/article13587.htmlhttp://en.afrik.com/article13587.htmlhttp://www.eurec.be/htm/projects/PISA%20II/Press%20Releases.htmhttp://www.eurec.be/htm/projects/PISA%20II/Press%20Releases.htmhttp://www.eia.doe.gov/emeu/cabs/chapter7.htmlhttp://www.eia.doe.gov/emeu/cabs/chapter7.htmlhttp://www.eia.doe.gov/emeu/cabs/Region_af.htmlhttp://www.eia.doe.gov/emeu/cabs/Region_af.htmlhttp://www.eia.doe.gov/emeu/cabs/Region_af.htmlhttp://www.eia.doe.gov/emeu/cabs/chapter7.htmlhttp://www.eurec.be/htm/projects/PISA%20II/Press%20Releases.htmhttp://en.afrik.com/article13587.htmlhttp://allafrica.com/stories/200912100768.htmlhttp://solveclimate.com/blog/20080421/solar-power-africa-best-investment-eu-can-makehttp://www.alternative-energy-news.info/african-solar-power-europe/http://www.alternative-energy-news.info/small-wind-farm-ready-to-generate-power/http://www.afriwea.org/en/country.htmhttp://www.tradeinvestafrica.com/http://interestingenergyfacts.blogspot.com/http://www.windenergynews.com/http://www.africanews.com/http://www.alternative-energy-news.info/http://www.ae-africa.com/http://www.scienceinafrica.co.za/index.htm

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