A car air-conditioning system that runs on fuel-saving solar power is slowly gaining traction among firms and the government, with its Hong Kong makers saying the technology is unparalleled in the world.
Around 20 vehicles, including taxis and minibuses, have been testing the system jointly developed by private research firm Green Power and Polytechnic University - and one customer has already seen favourable results.
A 10-month test done by Swire Coca-Cola, which fitted some of its trucks with solar panels and the special air-conditioning system, concluded that it could cut carbon dioxide emissions by 12 tonnes each year.
'We have already been granted the approval [to test it on] a number of different vehicle types already and should be expecting more vehicle types to be [approved] this summer,' said Jacky Lau, the vice-president of Green Power, which is based in the Science Park in the New Territories.
The Hong Kong government is even selecting a few official cars from its fleet for a trial run of the new system. If approved, the government will join around 10 companies - including Hongkong Electric, the Airport Authority, Polytechnic University and several tour bus and taxi operators - that have already been using the technology.
The new system requires vehicles to be retrofitted with solar panels on the roof. These convert the sun's energy into electrical power, which is stored in a tailor-made battery that can be used for back-up power or to power air conditioning with the help of the car's compressor system.
The entire assembly is separated from the petrol engine, such that when the vehicle is running or when the engine is switched off, the air conditioner can run independently without burning any fuel.
In contrast, conventional air conditioners for cars are powered by the internal combustion engine, which are not as fuel-efficient.
Professor Eric Cheng Ka-wai, who led the research at Polytechnic University's electrical engineering department, said minibuses could save about 30 per cent of fuel using the solar-powered system while taxis or private cars could save about 20 per cent. Development began in 2009.
A full charge takes about 10 hours, and six to seven hours of charging could provide enough energy for about three hours of air conditioning, Lau says. 'If the battery runs out, the air-conditioning system will automatically switch to derive energy from the engine,' he said.
It also has a device called 'maximum power point tracking', which converts all forms of light - including ultraviolet rays, which are emitted by the sun and black-light fluorescent bulbs - into electrical energy. This means charging can be done even on cloudy or rainy days.
'Since the vehicle itself has very poor heat insulation, the air-conditioner system for the vehicle requires a large cooling capacity and we have developed the system with outstanding conversion efficiency together with optimal energy control,' Lau said. 'We have not yet found another company that can achieve similar technology.'
However, the system is not yet compatible with large buses.
Lau said Green Power was currently installing the system on more vehicles and had even received orders from Macau. 'So there will be more running on the road in the next two months,' he said.
'We also expect to see an exponential growth in [orders] in the coming few months, as the summer season is closing up, [based on the] enquiries we are getting now,' he said.
About 10 more orders have been placed by some local transport operators who wish to test the system on their vehicles, with help from the government's Pilot Green Transport Fund, the executive says. The fund provides subsidies for trials of green and innovative technologies.
A spokeswoman for the Environmental Protection Department said they were studying the feasibility and effectiveness of the system in reducing emissions and conserving energy. She said they were looking into its compatibility with various vehicle types, its fuel-saving projections, installation and maintenance costs, and the makers' method in collecting data from pilot tests.
While results are pending, the spokeswoman urged public transport operators and private-car owners to test the solar-powered air conditioner. She noted they could apply for funding from the green transport fund, which could cover up to 75 per cent of testing costs.
Retrofitting and testing the system costs between HK$40,000 and HK$120,000, depending on the model, and for privately owned cars it would require the approval of the Transport Department. But this steep price tag will be offset by saved fuel, Cheng, the professor, says.
Lau, from Green Power, says the innovation comes ahead of a similar system being developed in Europe, the Thermal Systems Integration for Fuel Economy project, set to be rolled out in 2015 and which aims to reduce fuel use by 15 per cent.
But a challenge for the Hong Kong researchers is fitting the system to different vehicle designs, which will take time to test. While details of the research are under wraps, Lau says his firm is looking at extending the solar-powered system for use 'not only in vehicles but also other mobile machinery, stations or devices'.