Power up with solar thermal energy

The government has raised petrol prices several times and the unpredictable global weather is not helping. It will mean poorer production of vital crops, and as a result, we can be sure that food prices will rise again this year.

Merely fretting over rising costs is counter-productive, so why not think of ways to lower costs. For one, we can use the one naturally occurring, abundant and free resource — the sun — and the power of solar thermal energy to produce free heat and electricity.

Solar thermal collectors, in simple terms, collect heat from the sun for use in other forms. In their most basic form, flat plates collect heat which is then used for heating water (or swimming pools in cold countries).

More advanced systems such as those already in widespread use in China and Japan are very efficient and require little sun to produce heat.

Again, as with most things “green” nowadays, none of this technology is earth-shatteringly new, and in fact has been in widespread use for many years (though mainly in the West). It’s just that with climate change becoming an ever-present danger, these technologies are advancing much more rapidly than before.

For instance, a type of solar thermal collector, called the evacuated tube collector, has proven to be highly efficient in capturing and storing heat even at very low temperatures. It is also becoming more available to common folks, since mass innovation and high demand are driving down costs.

The principle behind its effectiveness is quite simple and rooted in basic physics. Water normally boils at 100°C but in the mountains, water boils at a lower temperature. The reason: lower pressure reduces the boiling point of water.

The evacuated tube collector takes advantage of this principle. The (glass) tubes are vacuumed, and in this vacuumed condition, the pressure inside the glass is extremely low. That means the boiling point of water is brought down to around 26°C. This is a very efficient way of obtaining heat.  

Hence, scientists, governments and businesses are beginning to realise that solar power can be used for base load power generation as well as peak power generation. More importantly, it has the potential to displace both coal- and natural gas-fired power plants. This is a real issue in Malaysia since the vast majority of our power is produced using natural gas, oil and coal, which are expensive, short in supply and dirty. Using solar thermal collection in industrial cooling has allowed us to significantly reduce our energy costs.

Imagine big quantities of hot water made virtually free and used to produce cold water for your air-conditioned chillers.

Enter the absorption chiller.

An absorption chiller (or refrigerator) uses a heat source to provide the energy needed to drive the cooling system. Not surprisingly, absorption chillers are possible alternatives to regular compressor refrigerators because electricity is expensive and the noise from a regular compressor can be quite inconvenient.

And in instances where there is surplus heat available (for example from turbine exhausts or industrial processes), then this proposition becomes even more compelling.

For example, a pulp and paper mill factory which wants to reduce electricity cost may find it useful to harvest the excess extraction steam instead of venting it out into the atmosphere (thus wasting this latent energy).

An absorption chiller could utilise this excess steam to air-condition its office buildings, thus killing two birds with one stone, since its electricity costs are vastly reduced and it need no longer spend money to cleanly rid the surplus heat.

Both the absorption chiller and the conventional electric chiller offer equivalent cooling capacities, but by some calculations, the absorption chiller uses much less electricity than a conventional electric chiller.

Absorption chillers could be mated with solar thermal collectors, and voila! Costs are lowered significantly.

In Japan, heating, ventilation and air-conditioning systems account for more than a quarter of the energy used in commercial buildings and nearly half of the energy used in residential buildings. I don’t have the details for Malaysia but we can’t be far off these statistics in the main cities of Kuala Lumpur, Penang and Johor Bharu.

Solar heating, cooling and ventilation technologies have the potential to significantly offset this energy usage. The sooner we recognise its potential and utilise this proven technology, the earlier we can help reduce our carbon footprint.

This article appeared on the Property page, The Edge Financial Daily, May 20, 2011.

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