Solar energy is the origin of most forms of energy. This energy can be made use of in two ways: the thermal route, i.e., using heat for drying, heating, cooking or generation of electricity or through the photovoltaic route which converts solar energy into electricity that can be used for numerous purposes such as lighting, pumping and generation of electricity. With its pollution- free nature, virtually inexhaustible supply and global distribution, solar energy is a very attractive energy resource.
Solar water heating (SWH) is the conversion of sunlight into renewable energy for water heating using a solar thermal collector.
In a "close-coupled" SWH system, the storage tank is horizontally mounted immediately above the solar collectors on the roof. No pumping is necessary as the hot water naturally rises into the tank through thermosiphon flow. In a "pump-circulated" system, the storage tank is ground- or floor-mounted and is below the level of the collectors; a circulating pump moves water or heat transfer fluid between the tank and the collectors.
Residential solar thermal installations fall into two groups: passive (sometimes called "compact") and active (sometimes called "pumped") systems. Both typically include an auxiliary energy source (electric heating element or connection to a gas or fuel oil central heating system) which is activated when the water in the tank falls below a minimum temperature setting such as 55 °C. Hence, hot water is always available.
In thermosiphon systems, a passive type, water flows through the system when warm water rises as cooler water sinks. The collector must be installed below the storage tank so that warm water will rise into the tank. These systems are reliable.
The objectives of the present work are given below:
1) To design a solar water heater which develops a better convective heat transfer compared to that of the conventional water heaters.
2) To study water heaters with various types of water tube cross sections and compare them for improved performance.