Powered by the Sun: Hot Water on the Cheap
A Malaysian architect's solar innovation
By JOHN COLMEY Kuala Lumpur
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Teoh Siang Teik. Chris Brown--Saba for TIME
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Teoh Siang Teik didn't set out to design the world's most powerful solar water heater. He just wanted to go trekking. As an architecture student in Scotland in 1979, the young Malaysian was looking for a way to prolong a visit to Nepal when a local businessman asked him to design a hotel in a rural area with no electricity. His energy-efficient solution won first prize from Scotland's Royal Incorporation of Architects. He returned with his architecture degree and designed 69 rural buildings for the Nepalese government, incorporating solar water heating. "My professors had told me to leave engineering to engineers and be an architect," Teoh recalls. "I was just looking for a way to save money on materials."
That quest resulted in a stunningly simple engineering breakthrough. At the time, there was essentially one way to build solar water heaters, using a 1976 Japanese patent that is still commonly applied today. In that basic design, an array of tubes in a flat glass panel is placed on a slope or roof and connected to a water tank. The water in the tubes is heated by the sun, rises slowly and enters a pipe running across the top of the panel, where it pushes forward and empties into the tank. The circle is completed when cold water is forced out of the bottom of the tank into a pipe running to the bottom of the panel. From there it begins the journey through the panel and back up to the tank again. Standing on the roof of one his houses in Nepal, Teoh was watching the hot water rise and shoot into a black 55-gallon drum when he realized how much heat was being lost pushing the water through the system. Says Teoh: "The first rule of solar water heating was that the tank was separate from the panel" and connected by a single tube. "I knew there had to be a more efficient way."
There was. After pondering the problem for several years, Teoh designed a heater in which each tube in the panel pours hot water directly into the tank. That shortens the path the water has to travel by nearly a meter and thus slashes the energy loss in transport. Building on the notion of reducing resistance to hot water flow, Teoh's research over the next decade led to several more design improvements. For example, he added an additional lower panel with exposed tubes suspended over a mirror that allows the heater to receive additional sunlight and even work on a cloudy day.
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