Carbon Conservation & Energy Efficiency


Bruce Rowse & Team

Solar Air Conditioning – Cool Technology!

September 7th, 2009 at 18:07

A recent Sustainability Assessment job took me to the corner of Victoria to the town of Mildura.  A town of around 30,000 people, Mildura borders NSW on the Murray River.  In summer the maximum temperature averages over 30 degrees and naturally there is a high demand for air conditioning and water.  Conventional air conditioning systems contribute substantially to greenhouse gas emissions through the consumption of electricity (predominantly generated from burning coal) and water, for cooling towers and evaporative cooling systems.

The idea of solar air conditioning was mentioned, which sounds great, but does it exist and is it practical?

After doing some reading, yes, solar air conditioning does exist, but despite Australia’s sunny climate there does not seem to be much awareness, knowledge and skills in this area.  So how does it work and why isn’t it widespread in Australia?

From my understanding, there are essentially two categories of solar air conditioning.

  1. Ventilation based systems that use photovoltaic power to power fans via heat exchangers or  through desiccant filters  that remove moisture from the air and improve thermal comfort and;
  2. Solar thermal systems that harness the sun’s thermal energy (heat) to drive the cooling system.

Photovoltaic powered ventilation based systems are very much dependent on climatic conditions and building design.  These kinds of systems take advantage of fresh air intake to a building and remove unwanted levels of humidity, improving thermal comfort and reducing cooling (heating) requirements.  These kinds of systems have generally been adopted for smaller-scale applications, including the residential market.  This form of solar cooling does not actively cool the air supplied to a building space and is therefore limited to the right environmental conditions to work effectively.

Solar active thermal systems are expensive, more complex and generally too big for smaller applications such as residential housing.  The common system uses an absorption chiller, which compared to a conventional compressor based chiller, does not use electricity to power the system, but instead uses solar collectors to heat water that is then used to produce chilled water through interaction with a refrigerant or desiccant solution.  Such systems can also be used to generate hot water for heating requirements and general hot water needs.  Such systems make good sense where ample sunlight is available and for large-scale or remote applications.

Absorption Chiller

Solar Absorption Chiller


Australia has a high demand for air conditioning and therefore a high demand for electrical energy through use of conventional compressor driven coolers.  The high demand of air conditioning in summer puts a huge strain on the electricity network and contributes substantially to global warming through burning fossil fuels and use of refrigerants (which have an extremely high global warming potential) in air conditioning systems.

Why then is solar air conditioning not widespread, at least for large-scale applications?  The main barriers to solar cooling include:

  • The high cost of solar collectors
  • Lack of skills in solar cooling technology and increased complexity
  • Abundant, cheap energy with no environmental cost
  • Minimum incentive to reduce peak power consumption

Overcoming these barriers really requires government intervention through subsidies, research funding, introduction of interval metering to pass on peak costs to electricity users and introducing a carbon tax or trading scheme to factor in an environmental cost on energy.

The Australian National University (ANU) is currently developing a hybrid solar air conditioning that is aimed at replacing conventional residential air conditioners.  The design employs a solar thermal powered compressor that can provide cooling and heating just like a reverse cycle air conditioner. The break-through is the ability to generate cooling like an absorption chiller, but without the need for a bulky and complex system.

The system employs what is called an ‘ejector pump’, which is capable of generating low pressure (necessary for refrigeration) and is low cost to manufacture.  A refrigerant is pumped to high pressure and then heated by solar collectors (the same used for solar hot water systems).  The ejector creates a drop in pressure (the cooling effect) by converting the energy in the refrigerant into kinetic (movement) energy by firing fluid into the ejector at supersonic speed.

Ejector Pump

Ejector Pump


Amazingly, the only electricity needed to power the ejector unit is 150 watts or 1/10 the power minimum of a conventional air conditioner.  This is set to revolutionise air conditioning as we know it and the project is moving closer to commercial viability.  With the onset of a carbon trading scheme, the rollout of smart meters beginning, energy rates set to increase and summers increasing in temperature, the economic case for this upcoming technology holds great promise.   I certainly can’t wait for this ‘cool’ technology!

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13 Responses to “Solar Air Conditioning – Cool Technology!”

  1. Jason Rogers Says:

    Good story, just for information Clear Solar are finalising the approval for the worlds most effecient A/C to be developed. It is currently on sale in the US and Europe, as well as installations throughout Singapore, India and Dubai.
    This system is scaleable and very efficient as well as green. it only uses a maximum of 650 watts for the largest system of 22KW.

  2. Graham Davies Says:

    Hi Jason,

    Thanks for letting us know about Clear Solar’s efficient AC system. It’s great to see more and more energy efficient solutions entering the market. I look forward to having a read.


  3. Peter Harrison Says:

    Northern Australia has to be asignificant market for almost year round solar airconditioning plus the major emerging markets in Singapore, Malaysia, Indonesia. Year round hot weather moderated by A/C is the norm.

    Why oh why has ther not been much progress in over 30 years? ARCO had solar energised absorption systems available then and they installed in many sites across the S of the USA. We even seriously considered such a system for a new home in Darwin, but it all got a bit tricky, as we were building after Cyclone Tracy.

    BUT……we need a new a/c ! Solar driven heat pumps and heat exchangers seem obvious for whole house systems, I am a bit stunned that nothing much seems ot have happened in 30 years. Or is the industry driven by energy vandals in the US where heating is the major need?

    We need to a while lot better. the Clear Solar a/c seems promising if energy needs are that low.

  4. Houston Air Conditioning Says:

    Good ! very good information . This system is not easy task but is very efficient . its very great to sharing this information .

  5. Ross Hastings Says:

    Thanks for your contribution to informing people of the options.

    Sorry I wasn’t able to speak with you first as I have been in this industryn for 10 years and have agencies for several ground coupled and water coupled cooling systems, absorption chillers etc..

    The breakthrough for me came when I found a condensing gas air conditioner which uses solar thermal superheating of the gas prior to condensing it. This method improves efficiency dramatically as the whole face of the condenser is now productive. It can save up to 50% of the electricity required and has an average energy efficiency ratio of 3.88. This means it only requires ikW of electricity to produce 3.88kW of cooling.

    As with the ANU system you still need electricity for fans and the circulating pump(compresser). It is available for installation anywhere in Australia by contacting us or visiting our website which is under construction.

  6. Serah Says:

    Dear Manager,

    Have a nice day!

    I am Serah from Beijing HaiLin Energy Saving Inc. Very pleased to get the information from your website and contact with you, it may be one of your choices in your business.

    Our main products are:
    • Thermostats (heating,fan coil, non-programmable/programmable,)
    • Valves (zone valves, ball valves, floating/modulating valves,butterfly valves)
    • Solar Heating Collectors (hot water, hot air solution & conrols), Advantages: Tinox coating, laser welding technology…
    • Sensor (temperature & humidity sensor)
    • Damper Actuator (2Nm-30Nm)
    We could accomplish the linkage of boiler, solar heating and heat pump. For more info., you are welcome to visit:
    HaiLin products were applied in all Beijing Olympic buildings, including Water Cube, Birds’ Nest etc. Do hope we have the opportunity to support your business as well.

    Appreciating for your reply.

    Best Regards.


  7. Greg Says:

    The government would also double – from $500 to $1000 – ceiling insulation subsidies for owners of 500,000 rental properties.

  8. casement air conditioner Says:

    Wow .. I’ve heard of solar air conditioning technology. This of course is useful because it can reduce the cost of electricity bills. What is the price of a solar air conditioning unit?

  9. Dylan White Says:

    in our place, the weather could turn out to be uncomfortably humid that is why we bought an air conditioner at home to reduce h’*~

  10. Nathaniel Wood Says:

    we have a 5 year old General Electic air conditioner at home, GE makes some of the finest air conditioners out ther.:~*

  11. Melatonin Supplement  Says:

    air conditioners are really needed specially if you have people with respiratory problems~-;

  12. Cooling Systems Says:

    Saving energy is a great way to go for your pocket, the planet, i have had solar cooling installed to my house and i think its great free cooling from the sun

  13. Philippine Lotto Results : Says:

    fresh air is hard to come by specially on those heavily populated cities”-’

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