Renewable Energy Wol. 2, No. 3, pp. 299 303, 1992 096~1481/92 $5.00+.00 Printed in Great Britain. Pergamon Press Ltd SOME THEORETICAL AND EXPERIMENTAL ASPECTS OF BUILT-IN SOLAR STORAGE M. A. HAMDAN and B. A. JUBRAN Department of Mechanical Engineering, University of Jordan, Amman, Jordan (Received 9 January 1991 ; accepted 28 November 199 I) AImtraet--The possibility of using a built-in storage solar water heater in Jordan has been investigated. Experimental and theoretical results were obtained using a 90 x 90 x l0 cm solar heater which was tilted at an angle of 30 ° to the horizontal. It was found that the efficiency of the built-in storage solar heater may reach as high as 78% with a maximum increase in the water temperature of 70°C and at low cost compared to the conventional itat plate collector. It is therefore expected that such solar system may be used to provide reasonably sufficient hot water in Jordan. Analytical solution, based on the assumption that the water temperature equals that of the plate, was used to solve the governing equations. While a numerical solution was used to solve the equations under the condition that the plate temperature is not equal to that of the water. It was found that the assumption of the temperature of the plate (Tp) is equal to the temperature of water (Tw) is only justifiable at early hours of operation in the morning. I. INTRODUCTION Many countries in the world have recently become more conscious of their energy requirement. They have found it economically necessary to explore alter- native sources of energy to reduce dependence on other nations for energy-producing fuel. Solar energy is considered to be a major source of energy in Jordan, a country characterized by an average daily solar radi- ation of about 5.5 kWh/m 2 [1] which could be used in different applications. At present the only type of solar collector employed in Jordan is the fiat plate collector which is mainly used to supply domestic hot water. This type of col- lector, which consists of separate collector and a stor- age tank, has been studied to a great extent [2-7]. A1 Saad et al. [2] developed an inexpensive and reliable solar heater for Jordan. The criteria used in their design were minimum cost, ease of manufacture, local availability of materials and maintenance free oper- ation. AI Saad et al. concluded that a locally manu- factured system can provide energy for domestic hot water with relatively good efficiency at a very com- petitive cost. A1 Saad [3] conducted an experimental investigation to study a thermosyphon solar domestic hot water system under Jordanian climate. It was found that the conventional solar water heater gave a relatively high efficiency and solar contribution to hot load for most of the year, however in winter months, the investigation indicated that the system efficiency and solar fraction were reduced due to low level of radiation as well as the increase in heat losses from the collectors. Such systems suffer a large amount of heat loss from the hot water as it is transferred from the collector to the storage tank. Also, there is a sig- nificant amount of heat loss from the collector to the ambient due to the high temperature difference between the absorber plate and the ambient. Further- more such collectors are expensive due to the require- ment of highly conducting material to obtain high collector efficiency, and it is also due to the installation of separate storage tank and an absorber unit. A built-in storage type solar water heater was pro- posed by Garg [7] in which the storage tank is inte- grated within the absorber unit leading to increased efficiency and a low cost compared with the traditional fiat plate collector. The performance of this system was extensively studied [9-12]. This paper concentrates on the utilization of the built-in storage solar water heater in Jordan. A theor- etical analysis of the system with various assumptions is presented from which the variation of the stored water temperature is compared against experimental values. 2. SYSTEM DESIGN The solar heater consists of a rectangular, 18 gauge, galvanized iron tank measuring 90 × 90 × 8 cm with an optimum volume of 0.081 m 3, and a collecting surface area of 0.81 m 2. The absorber plate is made of a black-painted galvanized steel plate. The heater was covered by a single glass plate of 0.032 cm thick. 299