February in Australia can be sweltering. Searing heat melts tar from the road, blistering rays burn human skin, and forget about getting into any car that’s been parked in the sun for more than five minutes.
Just about the best place on a hot summer day is kicking back on the couch, an icy pole in one hand, cold drink in the other, with the air-con blasting.
But in the context of carbon reduction targets, national water shortages and privatised electricity grids, are the days of escaping the heat in our air-conditioned homes numbered?
During a series of searing heatwaves across the United States in 2000 and 2001, residents in California felt the full effect of a deregulated power industry in complete meltdown. The power industry failed to keep up with the surge in power demands caused by air-conditioning, resulting in a series of rolling blackouts across the state and some very hot and bothered residents.
Dr Mike Dennis says this should be a warning to Australians, because although we’re not quite at the Californian stage, we are steaming down a very similar path.
“The problem is multifaceted,” Dennis says.
“The first problem is to do with investment. Companies don’t want to invest large amounts of money beefing up transmission grids – which would be very expensive, given that they’re going to be utilised for only a small part of the year.
“In Sydney the peak 10-15 per cent of transmission capacity is only used for 24 hours a year, so that’s a very poor return on investment.
“What’s happening is the peak demand is soaring, the ability of the transmission grid to support that is flat-lining, and we get blackouts because the grids can’t support the demand for extra power. The grid goes into self-protection mode by limiting the amount of power that it can transmit, resulting in entire geographical regions being shut down.”
Dennis, a senior research fellow in the Centre for Sustainable Energy Systems in the ANU College of Engineering and Computer Science, believes that peak period power shortages and blackouts are just around the corner for Australia.
“According to the National Electricity Market Management Company, Queensland was to be the first cab off the rank in terms of maximising transmission capacity and that was forecast to hit the wall sometime last year.
“Queensland power companies have had to do an emergency investment in their transmission grids. Transformers and lines have had to be upgraded and that has occurred at a huge expense. They pretty much jumped in at the last minute and did an emergency band-aid fix which may not be a wise long-term strategy.”
Instead of trying to fix the supply problem, Dennis began to think about the demand side – in the form of a solar-powered air-conditioning system. He says the air-conditioning industry faces a number of difficult challenges over the coming decade, the most prominent being banned fluorocarbon refrigerants, carbon pricing and water consumption.
“And then, of course, there is the greenhouse problem.
“Notwithstanding the emissions from electricity consumed by the air-conditioners, the refrigerants circulating in these units are several thousand times more potent greenhouse gases than carbon dioxide
“For every kilogram of refrigerant you have in your split system at home, you’ve got two or three thousand kilograms of carbon dioxide equivalent locked up in there which is about as much as the average car puts out in a year.
“There is a question mark over what becomes of this refrigerant upon disposal of the air-conditioner.
“There was a clear incentive to develop sustainable residential air-conditioning and the obvious solution was solar. The sun shines when we need to cool and Australia has an excellent solar resource,” Dennis says.
“We’re trying to pre-empt the problem and the sooner we can do that the better.”
His design replaces the electrical compressor in a conventional air-conditioner with a solar-powered thermal compressor. Solar power is provided in the form of heat, not electricity, from conventional solar water heater panels.
“Ruling out unsuitable options like evaporative coolers that consume a lot of water, and absorption chillers that require a lot of maintenance and contain many corrosive chemicals, I was left with one choice, a system with no moving parts, very little power consumption and no water consumption. It was the obvious pick for residential housing,” he says.
The technology is known as ejector cooling and works like an airbrush, where compressed air expands out of a jet, sucking paint and air into the airbrush body and then expelling it on to a target surface.
“I’ve replaced the paint with refrigerant. When that refrigerant evaporates as it gets sucked up the line, it draws in a lot of heat – so that’s the cooling effect. When it comes out of the jet, I’ve got to recirculate it back to where it came from and that’s the second part of my technology - recompressing it. So it’s a closed loop - no refrigerants escaping into the atmosphere.
“The nice thing is that you can use any refrigerant you like in this system - you can even use water if you want,” he adds.
The system has been designed so that it can also be used for solar-powered space heating in winter and solar water heating all year round, dramatically reducing the costs and environmental impact of heating and cooling a residential property.
“The air-conditioner is very similar to a household split system that most people are familiar with, the indoor unit remains unchanged. Everything is the same except for the power source - the remote control even looks the same.”
An extensive two-year commercially driven development program is due to begin in 2009, with commercial and manufacturing issues expected to be addressed in 2010. With only one moving part and no potent chemicals, Dennis predicts the cost to manufacture the system will be low.
Dennis claims that he’s not an environmental crusader, rather an engineer with a problem trying to find a solution.
“It just seemed like the right thing to do. I can’t see that in 50 years’ time from now, we’ll still be producing electricity by burning coal to the degree that we are now - that just doesn’t make sense to me. I don’t call myself a Greenie, seeking out research in this area was a rational choice rather than an emotional choice.
“Solar air-conditioning does make sense to me. We’re trying to pre-empt the problem and the sooner we can do that the better.”
2009
2008