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Vietnam Low-Cost Solar Water Heater

by Tran Quoc Giam

Vietnam is a tropical country which can make good use of a considerable amount of its solar energy potential, particularly in its south and central regions, but less so in the north because of the unsettled weather conditions.

In the past, there has been some use of solar applications, such as solar water heaters, solar cookers, solar dryers, PV-modules, etc. but in most cases, these technologies are still at the experimental stage.

Focusing systems, such as the solar reflector (parabolic) cooker, or highly sophisticated solar tower plants, should be installed mainly in the region below 17 degrees latitude because of their need for direct radiation.

The solar energy group of RERC has designed a highly efficient solar water heater (SWH) with integrated storage.

This consists of three collector cum-storage tanks which are designed as small units each of 30 litres (0.1 m x 0.1 m x 0.3m) capacity, combined to get a volume of 90 litres. Inside the tank, a wavy metal or plastic plate is linked under the absorber surface. The water heating mechanism is based on the thermosyphon effect. With solar radiation, the space and the wavy metal plate decreases which makes the heated water rise to the upper part of the tank' Normal convection circulation within the tank then occurs with the cold water from the top taking the lower space.

Since 1994, more than 40 systems of 1 m2 have been installed on an experimental basis in Hanoi and in Ho Chi Minh City. RERC aims to set up a production line for this new model of SWH sometime in the future.

Renewable Energy Research Centre (RERC), Hanoi National Institute of Technology, Hanoi, Vietnam. Reproduced from RERIC News, Vol 18 No 2/3 (June/Sept 1995)