25 December 2012, Sweetcrude, Enugu – Energy shapes national economies and social development. Indeed, energy powers daily lives; runs factories, fuels vehicles, heats and cools homes and businesses, amongst others. The stability and reliability of energy supply systems is even more appreciated now as many people are becoming more dependent on electronic data and services.
Electricity supply that can lead to sustainable development has to be reliable, affordable, economically viable, socially acceptable and environmentally sound for the socio-economic well-being of all. Reliable electricity access is the life-wire of any country. Without energy there is no economy. Nigeria is presently faced with the challenge of providing sustainable, adequate, reliable and efficient electricity supply to residential, commercial and industrial consumers.
This situation has adversely affected the social and economic life of the citizenry. The contemporary deteriorating power condition in which the nation is entangled, is as a result of the over dependence on fossil fuels, to fuel the electricity generating plants. Consequently, sustainable renewable energy resources, in spite of their abundance, were relegated to the back, contributing little to the overall Nigeria energy supply mix.
Successive Nigerian governments have made some giant efforts to solve this dreadful energy crisis that threatens the economic growth of the nation, but all efforts have proved abortive. One of these efforts, is the quest to join the world’s 20 most developed economies. The present government has set an energy policy that seeks to exploit the abundant renewable energy sources to complement fossil fuel, with the hope of improving the current power supply in the country.
Solar radiation represents the largest energy flow entering the terrestrial ecosystem. After reflection and absorption in the atmosphere, some 100,000TW usually hit the surface of the Earth and undergo conversion to all forms of energy used by humans, with the exception of nuclear, geothermal and tidal energy.
This resource is enormous and corresponds to almost 6,000 folds, the current global consumption of primary energy (13.7TW). Thus, solar energy has the potential of becoming a major component of a sustainable energy portfolio, with constrained greenhouse gas emissions. Solar radiation being abundantly present in Nigeria, is one area of focus among the renewable energy resources that can be harnessed to solve Nigeria’s power crisis.
Nigeria receives an average solar radiation of about 7.0kWh/m2 (25.2MJ/m2 per-day) in the far north and about 3.5kWh/m2 per day (12.6MJ/m2 per day) in the costal latitudes. The estimate of potential solar energy in Nigeria, with 5% device conversion efficiency is 5.0×1014 KJ of useful energy annually. This is equivalent to about 258.62million barrels of oil produced annually and about 4.2×105 GWh of electricity production annually, in the country.
Effective harnessing and utilization of this abundant solar radiation, using solar energy technologies to augment energy supply from fossil fuel energy resources (using cleaner fossil fuel technologies), would enhance availability of energy for socio-economic activities and subsequently lead the nation to realize its 2020 Transformation Agenda.
The sun’s structure and characteristics determine the nature of the energy it radiates into space. The sun is a sphere of intensely hot gaseous matter with a diameter of 1.39x109m and is, on the average, 1.5x1011m from the earth. As seen from the earth, the sun rotates on its axis about once every 4 weeks. However, it does not rotate as a solid body; the equator takes about 27 days and the Polar Regions take about 30 days for each rotation. The sun has an effective blackbody temperature of 5777K. The temperature in the central interior regions is variously estimated at 8×106 to 40x106K and the density is estimated to be about 100 times that of water.
The sun is, in effect, a continuous fusion reactor with its constituent gases as the “containing vessel” retained by gravitational force. Solar radiation is an electromagnetic wave emitted by the sun’s surface that originates in the bulk of the Sun where fusion reactions convert hydrogen atoms into helium. Every second, 3.89x1026J of nuclear energy is released by the sun’s core. This nuclear energy flux is rapidly converted into thermal energy and transported towards the surface of the star where it is released in the form of electromagnetic radiation.
The power density emitted by the Sun is of the order of 64MW/m2¬ of which 1370W/m2 reach the top of the earth’s atmosphere with no significant absorption in the space. The latter quantity is called the solar constant. Radiation reaching the Earth’s surface is altered by a number of factors, namely: the inclination of the earth’s axis and the atmosphere that causes both absorption and reflection of part of the incoming radiation.
Accounting for absorption by the atmosphere, reflection from cloud tops, oceans, terrestrial surfaces and rotation of the Earth (day/night cycles), the annual mean of the solar radiation reaching the surface, is 170W/m2 for the oceans and 180W/m2 for the continents. Of this, about 75% is direct light, the balance of which is scattered by air molecules, water vapour, aerosols and clouds.
Solar Radiation in Nigeria
Nigeria lies within a high sunshine belt and thus has enormous solar energy potentials. The mean annual average of total solar radiation varies from about 3.5 KWh (m2 per day) in the costal latitudes to about 7 KWh (m2 per day) along the semi arid areas in the far North. On the average, the country receives 19.8MJ (m2 per day). Average sunshine hours are estimated at 6hrs per day.
Given an average solar radiation level of about 5.5KWh (m2 per day) and the prevailing efficiencies of commercial solar-electric generators, then if solar collectors or modules were used to cover 1% of Nigeria’s land area of 923,773km2, it is possible to generate 1850x103GWh of solar electricity per year, which is over one hundred times the current grid electricity consumption level in the country.
*To be continued…..Subsequent segments will review the various types of solar energy technologies and try to know which of them is most suitable for Nigeria.
Aliyu Musa Kofa wrote in, to SweetCrude, Enugu, from Nuhu Bamalli Polytechnic, Zaria, Kaduna State.