Solar and air con - a marriage made in heaven

A new reverse cycle air-conditioning unit has hit the market with remarkable energy efficiency. Directly powering it with solar is the logical next step.

Daikin Australia has just released a new small agile reverse cycle air conditioner (that's a heater and air-conditioner all-in-one). The 3.6kW heating/2.5kW cooling FTXZ25N/RXZ25N is the highest performance heat pump air-conditioner ever offered on the Australian market and, as a direct response to the carbon tax, it uses a new low GWP (Global Warming Potential) refrigerant known as R32.

The unit is made in Japan and, when compared to what much of the country are buying new for heating (a gas or LPG heater), the unit is more than seven-times as efficient (725 per cent). When compared to the worst-case scenario, a 20-year or older ducted gas heating system with flue losses (35 per cent) and ducting losses (60 per cent) for a total system efficiency of 39 per cent, the new Daikin 7-star COP 5.9 air-conditioner is 1487 per cent more efficient in terms of heat (energy) delivered to the space than an old heater. (Check out the energy rating here.)

Daikin is approaching the thermodynamic limits of what is possible for an air-conditioner and, short of using a more flammable but still safe gas, such as R290 – we are not likely to see too many units that go significantly above 600 per cent efficiency (co-efficient of performance). For comparison, a bar radiator or oil-filled heater is 100 per cent efficient while an average gas wall heater is 70 per cent efficient and a typical reverse cycle air-conditioner running in heating mode is 200-300 per cent efficient.

So what's left for product innovation in this space?

There is a direct solar electric/grid AC air-conditioner hybrid available that is designed to have four 200-300 watt solar panels connected for a total of 600-900 watts of peak power generation, with appropriate fuse protection the air-conditioner can be run oversized by 200 per cent (six panels) or 300 per cent (nine panels) to make sure that it runs most daylight hours directly off solar.

The only downside of this product is that its COP is only 3.9 or, to put it another way, the unit is only 390 per cent efficient – a far cry from the 590 per cent efficiency of the Daikin.

That means that you are getting just two-thirds the air conditioning or two-thirds the heating that you would get directly out of the same panels if the panels were – hypothetically – connected to the high performance 600 per cent efficient Daikin unit.

It also means that when the unit falls back to the grid in the evening it will be running at the lower COP of 3.5.

So here is Daikin's, or one of the leading Japanese air conditioning manufacturer's, chance to completely revolutionise the global air conditioning and heating market. Release a COP 6.0 (600 per cent) efficient air conditioner that is hybridised with four panels (so it runs 34 per cent of daylight hours directly off solar) six (so it runs 65 per cent) or nine (so it runs 72 per cent of daylight hours off electricity) and then start selling them into the market. The advantage here is that there will be no need to deal with the distributors, it's low voltage so you do not need a licensed electrician involved (though, I could see them getting involved anyway) and they should qualify for RECs as a stand-alone system.

These hybrid options do not feed electricity into the grid, they just take what they need from the grid to top-up the solar contribution if it's very cloudy or at the very end or beginning of the day. And at night time they get their power directly from the grid just like a normal air-conditioner.

So put simply, Daikin could easily adapt their super-duper 600 per cent efficient air conditioner to preferentially run directly on DC electricity generated from solar panels while the sun is out and, seamlessly and progressively (as solar contribution reduces) switch back to the grid for nighttime.

So what can we do to hurry this along?


Let the likes of Daikin know that this is a world beating product and there would be huge demand for a high performance high quality solar photovoltaic hybrid DC inverter air conditioner/heat pump.

Australian states

At the state level it's time that the Victorian VEET scheme and other energy efficiency schemes in other states recognised the highest performing air conditioners. Given the VEET is an efficiency scheme when a consumer chooses a COP 5.8 unit such as the Daikin 2.5kW/3.6kW should be given considerable financial assistance (VEET certificates) towards replacing an old gas heater or an old air conditioner. The VEET currently supports lots of things with questionable environmental benefit but not high COP air conditioners which have an awesome ability to cut energy consumption. In my home using reverse cycle air conditioning we reduced our annual heating from 15,000MWh to just 3000MWh.

Federal government – Minister Hunt

At the federal level it's time for some direct action. Greg Hunt has the ability to sign off on new minimum standards. Air conditioning/heat pump units that have C.O.P. of less than 5.0 when measured at 7 degree heating and 35 degree cooling should be phased out and be removed from shelves under the nations successful Minimum Energy Performance Standards scheme. This is a simple consumer protection and environmental measure.


Finally for the Australian Renewable Energy Agency, it can back the application of the solar photovoltaic hybridisation technology to be integrated with the high performance Daikin 600 per cent efficient unit or any other brand/model of high performance air-conditioner that is above 500 per cent efficiency.

Matthew Wright is the executive director of Zero Emissions Australia, a not-for-profit volunteer based energy and climate research organisation.

*Note for readers: Stay clear of so-called solar air-conditioners that boost with a solar thermal panel on the roof. There is no proof available that these systems offer any sort of performance increase over not having the panels connected and they have low COP. You'd be better off just buying a unit that is better than COP 5.0, such as the Daikin.

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