In people’s technologies more than technology, social and cultural factors have also to be taken into consideration. In Japan there are 6 million solar water heaters even though the maximum ambient temperature there is the minimum in some Sunbelt countries. The success story is Japanese have the habit of taking bath in the evening and as such do not need overnight storage.

More over most of the solar water heater designs (for example, in India) are adopted from Europe. We don’t need so much of sophistification.

I have designed a vertical and cylindrical solar water heater which costs Rs 6000(about US$ 135) compared to commercially available soar water heaters $450.

The unit consists of two cylindrical drums of 50 liters capacity (Stainless steel) coated with mat black (for absorption) and placed one over the other with insulation at the bottom. There is an opening at the top to pour cold water. The bottom of the top drum is connected to the bottom of the lower drum through a pipe. There is a vent at the top of the drum to create pressure. There is an outlet (Tap) at the top of the bottom drum as hot water rises up. There are three concentric rings attached to the drums at 3cm spacing and over it transparent polyethylene cover to simulate green house effect. At the bottom of the drum a lotus shaped (Omni directional (stainless steel reflector is placed which increases the temperature in the bottom drum. There is a drain (Tap) to take out the water completely from bottom drum. Hot water, + 25 degrees ambience is obtained in South India.(If the ambient temperature is 30 degrees celsius,55 degrees hot water). A bamboo basket slightly bigger than the system covered with polyethylene sheet covered is placed on the system to prevent overnight cooling. Hot water is poured in the system (if tap is available one can connect it)at 9 am and bamboo basket is covered at 4 pm. The hot water can be used in the evening or next morning. In 12 hours of storage drop of 6 degrees Celsius has been found. The unit is mobile. All the parts can be made locally in workshops. Stainless steel drums have been chosen as hot water from the solar water heater can be used as Pre-Heated water for cooling.

The details of the system can be had from:

Dr.A.Jagadeesh
Renewable Energy Specialist
Nellore(AP),India
E-mail: anumakonda.jagadeesh@gmail.com