Technology could rescue drivers worried about having to wait in sweltering heat without air conditioning after an engine-idling ban comes into effect in December.
Solar-powered air conditioning can cool a vehicle for two to three hours if the battery is fully charged.
It can save up to 40 per cent on fuel, its developer claims.
But taxi and minibus drivers worry about cost. 'The government should at least provide a subsidy of half the cost, since the device can make the environment better and allow us to switch off idling engines,' said Leung Hung, chairman of the Hong Kong, Kowloon and New Territories Public & Maxicab Light Bus Merchants' United Association.
The system, still at an early stage of commercialisation, will cost about HK$40,000 for a taxi and up to HK$120,000 for a minibus to retrofit.
The developer is seeking approval for the system from the Transport Department. 'We have filed to the department, and, once approved, we can start retrofits on a commercial basis,' said Jacky Lau Yun-hong, vice-president of Green Power.
The system was retrofitted on 10 vehicles of different types and successfully tested on the road over the summer. Inventors said a taxi using the system could save an average of 21 per cent in fuel, and a minibus 27 per cent. The temperature inside can be chilled to 22 degrees Celsius.
The system is powered by a soft solar panel mounted on the roof. Charging for six to seven hours can provide two to three hours of air con.
Cheng Hak-wo, permanent chairman of the Taxi Dealers and Owners Association, said he would support the retrofit, to improve roadside air pollution. But he declined to comment on whether the price was affordable and whether costs would be passed on to taxi passengers.
Ling Chi-keung, chairman of the Public Light Bus General Association, said cost, quality and availability of post-installation maintenance would be factors for professional drivers to consider. 'Objects falling from a height are common in Hong Kong, so we must know how expensive it is to replace the solar panel on the roof,' he said.
Dr Kitty Poon Kit, undersecretary for the environment, said the engine-idling law would come into effect on December 15 if lawmakers approved related subsidiary legislation.
Under the ban, which has been debated for 14 years, no vehicle engine would be allowed to idle after a three-minute grace period, unless it has an exemption.
Critics say the proposed law will have far too many exemptions and will be difficult to enforce.
The South China Morning Post recently found abnormally high pollution levels at idling hot spots in Mong Kok and Causeway Bay.