Journal of Energy Technologies and Policy www.iiste.org ISSN 2224-3232 (Paper) ISSN 2225-0573 (Online) Vol.3, No.6, 2013 1 Performance of Solar Water Heater in Akure, Nigeria Samson A. Arekete Mathematical Sciences Department, Redeemer’s University, Redemption City, Mowe, Nigeria E-mail: Samson_Arekete@yahoo.com Abstract Solar water heating is a process of tapping energy from the sun for the purpose of raising the temperature of water from local water supply to some desirable higher temperature. Water left in a container and exposed to the sun, has been observed to increase in temperature. However, this natural gain of temperature is not usually efficient; partly because water is a poor absorber of solar energy and partly because a large chunk of energy gain is used in evaporation of water, which will not result into temperature raise. A solar water heater was designed, constructed and tested in Akure, South West, Nigeria (Latitude 7.30 o N and Longitude 5.25 o E). A flat plate collector covered with double glazing layers at 20 o angle of tilt to the horizontal was employed. The surface of the collector was darkened to improve its absorption capacity. Readings were taken for a period of six days. With an ambient temperature of 36 o C, a maximum hot water temperature of 73 o C was recorded during the experiment. In addition, hourly collector’s efficiency increased slightly until 2.00 when steep increase was obtained which peaked at 92% at 4.00 pm. The outcome of the experiments established the fact that solar water heater is feasible in South West Nigeria, and of course, in most parts of the country, since insolation is even higher in most other parts of the country, particularly South East and the Northern regions. Keywords: Solar water heater, insolation, radiation, solar energy, thermosiphon. 1. Introduction Solar water heating is one of the prime application areas of solar energy. According to (Kishor et al., 2010) water heating by solar energy for domestic use is one of the most successful and feasible applications of solar energy. Other areas of application of solar energy include solar drying, electricity generation using photovoltaic cells, solar cooling and refrigeration, solar still (or solar distillation) and solar cooking. An ambitious solar plan that would result in the generation of 20,000MW of solar energy by 2022 had been put in place by India (Renewable Energy World, 2009). Using the sun's energy to heat water is not a long known idea (Marshall, 2009). The Romans warmed their baths with large south-facing windows and modern-prototype solar water-heating systems of copper tubes in glass- enclosed boxes were already invented by the late 1800s. These pioneering forays, however, seemed to be lost on Americans until the 1970s, when oil shortages prompted the then President Jimmy Carter to grant generous federal and state solar-energy tax credits for solar water heaters. Solar water heating has been reported to enjoy much popularity in places like Australia, Israel, the United States of America, Germany, Sweden, India, Jordan, Cyprus, China, Greece and Japan (Reeves, 2009; Garg, 2009). Nigeria, like many other tropical countries are blessed with abundant solar energy which is beamed over the geographical entity and received freely on daily basis. Tapping solar energy for the purpose of heating water is based on a simple natural phenomenon. Cold water in a container exposed to the sun undergoes a rise in temperature. However, this natural temperature gain is usually very low, being only a few degrees Celsius. The reasons for this low temperature gain are twofold. One reason is due to the low heat absorption of water. The second reason is because much of the heat that is absorbed goes into increase evaporation, a change of state from liquid to gas phenomenon, thus reducing temperature rise. A solar water heater employs a solar collector with good absorption capacity and with the ability of collecting energy from over a wider area and harnessing the energy collected to raise the water temperature significantly. The issue of evaporation of the working liquid is significantly minimized since the fluid flow is within insulated pipes and storage tank. Solar water heaters, also called solar domestic hot water systems, can therefore be a cost-effective way to generate hot water. They can be used in any climate, and the fuel they use the most, sunshine, is absolutely free (Revees, 2009). There are two basic types of solar water heating systems on the market, one known as passive (no pumps, also called thermosiphon system) and the most popular known as active, which has pumps that circulate heated water through the system. Solar collectors are of three main types — evacuated tube, copper glazed and polymer. Traditional glazed collectors are large heavy glass covered boxes that need roof loading engineering equipment or cranes to install. On the other hand, polymer collectors are lightweight and are easy to install by one person and require no roof loading or special equipment to install (Revees, 2009). A passive solar design works without