Efforts to harness the sun’s energy are spreading in the heartland.
The Housing Board recently bought solar photovoltaic panels worth about $2.3 million for various residential estates. In total, the panels are expected to produce 170 megawatt-hours of energy each year which, said an HDB spokesman, would represent about $40,000 in savings a year per precinct.
The HDB began installing solar panels in the estates of Serangoon and Wellington in December 2008. Since then, the price of solar panels has dropped by more than half, from $5.17 a watt-peak to $2.33 a watt-peak.
While there are many options for renewable energy - hydropower, biofuel and wind among them - solar power could become a significant energy source in Singapore.
Solar energy is usually understood as harnessing the sun’s capacity for electricity production through photovoltaic (PV) panels, which convert part of the solar radiation into electricity. But such systems often do not use thermal energy.
Another kind of system can harness solar energy for heating purposes, using a solar thermal collector. Thermal energy can then be transferred by water or other refrigerants for a range of uses.
In places such as hospitals or industrial kitchens, thermal collectors can be coupled with heat exchangers, so the heat can be used for sanitation or food preparation. An example would be the solar hot water plant installed at Changi International Airport Services. With a collection area of 1,200 sq m, the plant provides enough heat to meet 68 per cent of the ground-handling company’s annual demand, while dramatically reducing its carbon emissions.
PV-only systems have garnered much attention, due to their ease of use and track record. But in recent years, advancements have led to the integration of the two forms of solar technology into hybrid photovoltaic thermal (PV/T) systems, which can produce electricity and heat simultaneously.
PV/T systems are generally more efficient than non-hybrid solar ones, as solar energy with lower heat content can be recovered for use. A 2004 study conducted in the Netherlands for the 19th European PV Solar Energy Conference and Exhibition showed that the PV/T system was more economically competitive than the PV-only system and at least 40 per cent more efficient than the thermal collector and PV-only system.
We believe PV/T systems will become more popular with greater interest in ‘green’ buildings. Other than producing electricity for office appliances, PV/T systems can also generate heat for space heating. For instance, in cooler climates, heated air can be introduced into a building as ventilation air during the colder months, and shunted outside in summer.
Examples of PV/T systems are those in Thailand’s Banglamung and Queen Sirikit hospitals, which save about 4,320 kilowatt hours (kwh) and 14,856 kwh of electricity, and 42,330 kwh and 164,885 kwh of heat, respectively, a year.
At the current price of electricity in Singapore - 24 cents a kwh in the second quarter of this year - this amounts to $1,037 and $3,565 a year in electricity savings for the respective hospitals. In Singapore, the heat could be used to boil water, which would help to reduce electricity bills further.
Global warming and diminishing resources have added urgency to the search for alternative energy. The sun seems to be the most viable of these sources. And of the range of solar energy technology, hybrid systems hold the greatest promise. PV/T systems will in all likelihood gain popularity and dominate the future solar market.
The writers are analysts at the Energy Studies Institute, National University of Singapore.
