Singapore experiments with energy saving home for the tropics

Dec 24, 2009, 10:28 GMT

Singapore - From outside Singapore's Zero Energy Home it looks like the garden has been extended onto the building's facade. A thick layer of small green plants cover the houses' walls, held there by wire mesh. This is not a home for a wood goblin but Singapore's first home that attempts to produce at least as much energy as it consumes.

The south-east Asian city is trying anything the energy saving market has for tropical countries plus a few ideas it has come up with itself.

Singapore has been forced to be inventive. 'Most energy saving homes were developed in the West. Insulation to preserve warmth is the main focus there but that's not what we need in tropical countries,' says project manager Alice Goh. In regions that have cold winters it makes sense to use insulation as 80 per cent of the energy used in private households is for heating.

That does not apply to homes in the tropics however. Instead of keeping warmth in, the goal is to keep heat out. Instead of directing the sun's power inside a home, tropical energy saving homes aim to stay cool.

Singapore is 150 kilometres from the equator and on average is over 30 degrees Celsius all year round. It wants to become the leader in energy saving among tropical countries and its government has established the Solar Energy Research Institute of Singapore (SERIS) to do that.

'We're concentrating on technologies and services for tropical countries,' explains the institute's head, the German atomic physicist Joachim Luther.

Singapore's Zero Energy Home is where the institute experiments with new ideas. The three storey building with 4,500 square metres of space once housed a workshop. It's the first home of its kind in south-east Asia that has been renovated to produce as much energy as it uses.

'The plants on the walls are an additional form of thermal insulation,' says Goh. The plants prevent the rays from the hot tropical sun heating the walls and Singapore's housing authority HDB has already decided to cover the roofs of its high-rise buildings with plants.

It's a mammoth project: 80 per cent of Singapore's three-and-a-half million residents live in the 900,000 apartments the authority has built. 'Greening the roofs will reduce temperatures in the buildings by two degrees,' says HDB engineer Koh Guan Bian Goh.

The Zero Energy Home is also being used to test double glazed windows that have blinds between the panes of glass. Depending on the sun's strength the blinds descend, covering the windows with a foil that blocks heat. There are also mirrored shafts that cleverly direct the sun's light inside the house as well as 'light shelves' - horizontal mirrors attached to the windows that both create shadow and direct light inside.

There is also a Singapore air conditioning invention of two jets that blow cool air precisely where it's needed at an area where people sit and work. One room is used to simulate a school gym and has been equipped with ventilation chimneys; large metal pipes in the roof expel warm air outside while drawing cool air into the room through side windows.

The sun collectors on the roof come from Japan while the heart of the solar electricity generation plant was made by the German firm SMA: an inverter that connects the solar module to the electricity network.

'It's the best of its kind on the market,' says German engineer Stephen Wittkopf who also works at SERIS. 'Most things work differently in the tropics than they do in more northerly climes,' he says. 'In Germany the sun tends to shine at specific points in the sky whereas here it shines in the entire sky.'

The solar cells get hotter in the tropics and as a result are less efficient. Among other things SERIS is working on is a transparent solar foil for windows that will generate energy and direct it to solar controlled air conditioners.

The Zero Energy Home generated 13,316 kilowatts of electricity in its first three weeks and consumed 10,925. That compares to the 24,502 kilowatts a conventional house of this size would use. The house also saved 6,872 kilograms of climate-warming carbon dioxide emissions during the same period.