SOLAR ENERGY: POTENTIAL FOR MITIGATING DEVASTATING EFFECTS OF CLIMATE CHANGE

ABSTRACT

Climate change has been identified as one of the greatest challenge by all the nations, government, business and citizens of the globe. The threats of climate change on our green planet ‘Earth’ demands that renewable energy share in the total energy generation and consumption should be substantially increased as a matter of urgency. Nigeria’s energy development programme has been put under severe pressure with the ever-increasing demand supply gap. Due to predominance of fossil fuels in the generation mix, there are large negative environmental externalities caused by electricity generation. So it has become imperative to develop and promote alternative energy sources that can lead to sustainability of energy and environment system. Renewable electricity has become synonymous with CO2 reduction.

Present communication provides a brief description about such alternative and sustained energy sources, i.e., renewable energy resources, their potential and achievements in Nigeria. Also role as important tool for climate change mitigation.

INTRODUCTION

The sun supplies the majority of the energy available on the Earth; wind power, hydropower, biomass and all fossil fuels can trace their energy source back to the sun. These indirect routes for deriving solar energy have certain advantages: storage of energy in the case of fossil fuels and hydropower, and transportation of energy in the case of wind. However, the challenges involved in harnessing solar energy directly and on a large scale are such that it remains an elusive but still fundamentally attractive way of mitigating climate change. This paper describes the present status of solar energy worldwide, and outlines the competing technologies, the magnitude of energy they could produce, and the extent to which they could be used.

Human use of solar energy spans natural lighting and agriculture, from simple technologies such as the outdoor clothesline through to centralized electrical power plants equipped with storage. It is almost impossible to quantify this habitual use, as most uses of solar energy, such as passive heating, are classed as energy efficiency measures. While these simple solar approaches are important, this paper is primarily concerned with active solar power conversion that can displace conventional power generation and contribute towards a truly sustainable energy supply.

The solar radiation continuously available to the Earth [162,000 terawatts (TW, 1012W)] greatly exceeds the average worldwide primary power consumption in 2004 (16TW), 86.5% of which came from fossil fuels. The combined output of active solar energy systems currently meets only 0.1% of the world’s primary energy consumption.

The efficiency of solar energy systems is rated according to their performance under a standard test irradiance of 1000 W/m2, which corresponds to the maximum irradiance expected on a clear day in summer at moderate latitudes. The actual level of solar irradiance will depend on the latitude and local climatic conditions, but the annual average solar energy density lies in a range

from 100-250 W/m2 for most locations. The capacity factor for solar a collector (actual output power / rated output power) therefore lies at 10-25% depending on location. This fluctuation is significant in determining the broad economic suitability of solar energy technologies. However, the extent to which solar energy can help mitigate climate change depends on the carbon intensity of the local energy supply being displaced and the matching between supply and demand.

Due to the nature of solar energy, two components are required to have a functional solar energy generator. These two components are a collector and a storage unit. The collector simply collects the radiation that falls on it and converts a fraction of it to other forms of energy (either electricity and heat or heat alone). The storage unit is required because of the non-constant nature of solar energy; at certain times only a very small amount of radiation will be received. At night or during heavy cloud cover, for example, the amount of energy produced by the collector will be quite small. The storage unit can hold the excess energy produced during the periods of maximum productivity, and release it when the productivity drops. In practice, a backup power supply is usually added, too, for the situations when the amount of energy required is greater than both what is being produced and what is stored in the container. 

Methods of collecting and storing solar energy vary depending on the uses planned for the solar generator. In general, there are three types of collectors and many forms of storage units. 

The three types of collectors are flat-plate collectors, focusing collectors, and passive collectors. 

Flat-plate collectors are the more commonly used type of collector today. They are arrays of solar panels arranged in a simple plane. They can be of nearly any size, and have an output that is directly related to a few variables including size, facing, and cleanliness. These variables all affect the amount of radiation that falls on the collector. Often these collector panels have automated machinery that keeps them facing the sun. The additional energy they take in due to the correction of facing more than compensates for the energy needed to drive the extra machinery. 

Focusing collectors are essentially flat-plane collectors with optical devices arranged to maximize the radiation falling on the focus of the collector. These are currently used only in a few scattered areas. Solar furnaces are examples of this type of collector. Although they can produce far greater amounts of energy at a single point than the flat-plane collectors can, they lose some of the radiation that the flat-plane panels do not. Radiation reflected off the ground will be used by flat-plane panels but usually will be ignored by focusing collectors (in snow covered regions, this reflected radiation can be significant). One other problem with focusing collectors in general is due to temperature. The fragile silicon components that absorb the incoming radiation lose efficiency at high temperatures, and if they get too hot they can even be permanently damaged. The focusing collectors by their very nature can create much higher temperatures and need more safeguards to protect their silicon components. 

Passive collectors are completely different from the other two types of collectors. The passive collectors absorb radiation and convert it to heat naturally, without being designed and built to do so. All objects have this property to some extent, but only some objects (like walls) will be able to produce enough heat to make it worthwhile. Often their natural ability to convert radiation to heat is enhanced in some way or another (by being painted black, for example) and a system for transferring the heat to a different location is generally added. 

According to experts, climate change is caused by the huge amount of greenhouse gas emissions in the planet. The increasing quantity of atmospheric carbon dioxide from burning of fossil fuels contributes and leads to global warming.

Countries around the world are looking for ways to reduce the problem. Experts say that in order for us to lessen the harmful effects of the world’s energy consumption, people should find ways to lessen their energy needs, be more efficient and less use energy as possible, and to use more renewable and alternative energy sources. These said ways are effective and are proven to reduce a percentage of greenhouse gas emissions.

Households are encouraged to use clean electricity that is generated through solar panels. Having solar modules installed at your home is a very good alternative and would help reduce greenhouse gas emission from your home. Not only you are helping the environment, you are also making yourself save a huge amount of cash