A chilled future for solar power ?

The Climate Spectator has an article on research into a solar powered air cooling system which could help reduce the spiralling cost of network transmission expansion required to meet the growing summer peak loads created by air conditioning units - A chilling future for solar power.

Everyone seems pretty comfortable with the idea that the energy from the sun can be captured to heat stuff and create electricity. But what if we were able to use it to address one of Australia’s greatest needs: how to cool things down, particularly the air inside your home; and one of its greatest challenges – reducing peak loads on the network?

This is one of the ideas being developed by the CSIRO at its Energy Research Centre in Newcastle. And the technology – known as Solar Cooling – is now at the point of commercialisation. And it is so simple it can be bolted on to the solar hot water systems that are already so prevalent in suburbia – and add space heating in winter and cooling in summer to the hot water that is already delivered by the solar collectors.

The irony of this development is that it offers the opportunity for a renewable energy source to provide a solution for a problem it is often blamed for creating – rising electricity costs.
The reality is that the greatest component of rising energy bills is the cost of network upgrades, and the biggest reason for these is the growth in peak energy demand, driven largely by the rush to install household air conditioning systems, which now account for around 50 per cent of peak demand on some networks.

Indeed, such is the scale of the rollout of domestic air-con, and its impact on networks, that it now qualifies as the most heavily subsidised sector of the electricity grid – far greater than rooftop solar, or large-scale wind farms.

For every $1000 invested in an air-conditioning system, it is estimated that another $3000 is required to upgrade the network. That translates into an added cost of $100 per year on the electricity bills of those who either choose not to have air-con in their home, or who can’t afford it.

Reducing peak demand is one of the biggest challenges facing energy market operators. In Australia, it is estimated that one quarter of the nation’s electricity costs go to catering for around 40 hours of peak demand – those occasions of extreme temperatures when everyone turns on their air-con at the same time and when the electricity demand is nearly doubled. If this technology based around solar panels on the roof can be rolled out at scale, it could offer one of the best opportunities to significantly lower those peak loads and reduce the need to upgrade and expand networks and help flatten the anticipated spikes in domestic electricity bills.

The principle behind Solar Cooling systems being developed by the CSIRO is simply to integrate technologies that are already understood – the rooftop panels on the roof that heat the water, and which can then be used to heat air; a desiccant wheel to dry the air; and evaporative systems to cool the air.

Stephen White, the manager of the CSIRO’s Energy for Buildings division, says the advantage of this system is that it can operate at relatively low temperatures – 50°C to 70°C – which are common for solar hot water systems.

Incoming hot, moist, humid air is dehumidified using a desiccant such as a silica gel on a rotating wheel to create a dry air stream which is then cooled using an evaporative cooler. The desiccant absorbs the moisture from the air. This material is then stripped of moisture (regenerated) using solar heat.

The CSIRO believes that electricity costs could be reduced by half – and would be a much more efficient use of resources, because the solar collectors would be in use all year round, while a conventional air conditioner system might be in use for just 7 per cent of the time.
“We see it as three in one solar thermal product for the home – a solar hot water system, and space heating in winter, and cooling in summer when the sun is shining the hardest," Dr White says. “It matches very nicely." It is likely that these systems will be able to bolt on to already installed solar hot water systems.

The CSIRO has already developed a prototype called REDEcool which can be used in households and is now looking for a manufacturing partner to help refine the design, and the costs, for mass production. Dr White says the capital cost of the system will be more than the $1000 that people pay for the air-con systems they buy from shops, but it should be cheaper than the $4000 network cost.