Abstract
Solar water heating is a technology of capturing the energy from the sun's radiation for the purpose of raising the temperature of water from water supply temperature to the desired higher temperature depending on the use. There are many views and discussions on the questions of thermal efficiency of solar water heaters and their associated cost, especially different customers/users want to replace their existing conventional water heating energy by solar water heating systems. In this present paper, a deep investigation has been accomplished to determine thermal efficiency and cost analysis of solar water heater made in Rwanda. During manufacturing of solar water heater, the collector was the main part to emphasize on. The high efficiency of the system was achieved by replacing galvanized iron sheet by aluminum sheet slotted and black painted as an absorber plate. The ambient temperature and average solar radiation of the three sites where solar water heaters are installed were investigated. The used materials, specifications and sizing were discussed in this paper.
Highlights
The aim of this paper is to investigate the efficiency and cost analysis of solar water heater made in Rwanda and to present the methods used to increase the efficiency of solar water heater during its manufacturing
Numerical analysis and some software have been used to study and design the thermal efficiency solar water heaters using U-type evacuated tube solar collector and the results showed that this solar collector should provide 40.5% of the total consumed energy in the year (Li et al, 2015)
The following formula is used for determining the efficiency of solar collector: gi mCpðTout À Gt:AC
Summary
Solar water heating systems are mostly used in a wider scale because they provide an environmental favorable heat for various areas such as household water heating, swimming pools heating and other areas where hot water is needed. This system collects the energy from the sun to use it for heating air or water. Many group of researcher focus on theoretical and experimental research for improving and measuring heat transfer losses in evacuated tube and flat collector using different approaches and methods (Liu et al, 2016, 2017; Yang et al, 2014). Some literature points out a high effectiveness and environment friendliness of solar water heater (Kalogirou, 2009) while others still questioning on the initial cost and maintenance cost of solar water heaters. Alberto and Ferrer (2017) investigated the economic point of view of solar water heaters installed in chosen municipalities in South Africa, the shortest and longest payback period have calculated, he found that the average payback period of 8 years exceeds the warranty period of solar water heater in South Africa which is 3 years
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