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Solar air-con to keep you cool – and off the grid

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We have heard about how rising power prices could be driving consumers off the grid; and we have written about how Australia’s booming air-con uptake is causing the kind of “super” spikes in peak power demand used to justify network operators’ disproportionate spend on poles and wires – which, in turn, has driven up power prices.

Now, there’s an Australian invention that could help address both of these problems at once. QUT researcher, Paolo Corrada, is developing a home solar cooling and heating system that will run independently of the electricity grid, and generate domestic hot water as a by-product.

Corrada, a PhD student in QUT’s Science and Engineering faculty says the system he has designed – which is based on well-proven and highly efficient absorption chiller technology – cuts energy consumption by 90 per cent.

“My target is to make it 100 per cent so that the system is self-sufficient to run off the main grid, costing the home owners nothing to run,” Corrada said in an report published late last month by the QUT-affiliated publication Phys.org.

“Heating and cooling account for about 65 per cent of energy consumption in a house, whereas cooking accounts for only 6 per cent so it is easy to see why air conditioning devices are the main targets to reduce our energy consumption.

“An absorption chiller uses a chemical process to reject heat and, when using waste heat or heat generated by renewable energy, is more effective than the more common mechanical process of vapour compression at deflecting heat,” he said.

“By using renewable energy from the sun we are providing an excellent technology to slash power consumption and the peak demand, especially in subtropical remote areas. The design is revolutionary because it incorporates also a desiccant wheel to remove moisture from the air and it uses the rejected heat from the absorption chiller to regenerate itself and to produce hot water for the house.”

Phys.org reports that by combining these two technologies, Corrada has managed to increase the unit’s efficiency by 40 per cent, compared to current solar cooling systems. Corrada’s system is also much quieter than others, because it uses a small pump instead of a compressor, like standard split systems.

Funnily enough, while Corrada is hoping that his technology will help free Australian consumers from the grid and from the sting of peak summer power prices, Queensland utility Ergon Energy – in partnership with the CSIRO, GWA and the Australian Solar Institute – is busy developing its own solar powered air conditioning solution, in an effort to even out demand, and prices, and thus keep hot-and-bothered customers from deserting in search of a cheaper alternative.

As we reported back in April, the Ergon-CSIRO plan is to create a “firming” solar resource which can support the electricity grid during times of stress. The technology developed by CSIRO uses panels similar to those used for solar hot water, to collect the sun’s heat as hot air, which is used, in turn, to create cool air.

CSIRO hope to retrofit these devices on houses, with gas backup, and couple them with an energy management device that – and here-in lies a big difference – links back to the grid operator. At peak times, a remote signal will instruct the air-con to switched from electricity to the solar source or, if there’s no sun about, a gas source.

“Air-con demand is a huge problem in Australia,” said Daniel Rowe, the project leader in the Demand Side Energy Systems group at CSIRO. “Renewables are intermittent, and utilities and power engineers want reliability, but we think we can transform renewable energy technology – solar cooling – into firm demand reduction that is callable by the network. This is about making link to utility during those few hours a year that really count and make it something they can rely upon.”

Corrada’s offering, of course, will look more attractive to consumers. But first, he will need to iron out a few kinks. As ZeitNews reported last week, Corrada noted in his report that “the system has some limitations that need to be addressed” if there is to be a practical application.

“A storage tank is required to make the domestic hot water available around the clock. Also, the availability of cooling power does not match with the cooling request; after 6.30pm and during the night, the demand for cooling could be still relevant because of the temperature and/or the humidity,” Corrada said.

But he adds that these limitations can be easily overcome by installing storage – although at an added cost. “To reduce the cost,” Corrada says, “a reduction of the cooling capacity could be considered if compensated by increasing the insulation of the walls, roofs and windows of the standard household.”

These speed-humps aside, it looks like Ergon and CSIRO had better get a wriggle on. Because as ZeitNews put it, once the technology for 100 per cent self-sufficient solar air-con becomes simple enough – and cheap enough – we might see more and more “small, high efficiency home(s) with a small, high efficiency air conditioner powered by a big honking bank of photovoltaics, and be done with it.”

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  • Mart

    ‘we will see more and more “small, high efficiency home(s) with a small, high efficiency air conditioner powered by a big honking bank of photovoltaics, and be done with it.”’

    That seems a very limited and shortsighted approach. Wouldn’t people want to integrate their electric car charging into this system?

  • John P Morgan

    A “low tech” version of this is already in use.
    It’s called “thermal mass”, especially when implemented in a reverse masonry veneer house.
    The mass soaks up summer heat keeping things cool in summer. The heat stays in the internal fabric until winter when it is then released maintaining thermal comfort without need for a heater.

  • http://wpowerproducts.com Max Stanford

    I really wouldn’t mind hearing more about this. I’m going to look into that “thermal mass” that you are talking about John.

    • John P Morgan

      Max, it is not possible in a standard brick veneer house but for a reverse brick veneer, the inner masonry wall can absorb summer heat and thus keep the internal temperature well down. Thus the inner temperature is always lower than outdoors and the 2nd law of thermodynamics requires that all that heat in the wall must stay in the house until outside temperatures drop below that of the indoors – winter time!!
      As the house slowly cools, heat will leak from the walls into the house to maintain thermal comfort.
      I’ve proved it.
      My house doesn’t even have a heater built in!
      I actually encourage summer heat to come in!
      It’s cheaper than running a heater in winter.

  • john258

    Solar power is an awesome money saver. I would definitely be interested in solar air conditioning units. http://www.aircon-johannesburg.co.za