By Debbie Yong

The Ngiam family of Serangoon North had a bright idea.

Why not fit a solar panel outside their Housing Board flat and get free electricity?

A few days later, HDB officials came a-knocking to ask about the structure. But they did not ask the Ngiams to remove the 1m by 0.5m panel fixed to a small roof extension outside the common corridor of the executive maisonette.

SOLAR THERMAL CELLS

How they work
Solar thermal cells convert the sun's energy to heat energy. When the sun's rays reach the heating panel, the heat generated can be used to boil water.

Mr Abhay Kumar Agarwal, 52, owner of Pacific Sun Systems, said there are two types of solar thermal systems.

The older type is a flat panel system. The newer type has vacuum tubes which absorb the heat from the sun, transferring it to the water in the tubes.

For more The Straits Times stories, click here.