Solar-powered air-conditioning system for vehicles

Oct 11, 2011 By Wilfred Lai
Solar private car. Credit: Partnership Development Office

Great news for drivers! They can now continue to keep the air-conditioning system on during the hot sunny days even when they stop the vehicle and switch off the engine. In collaboration with Green Power Industrial Ltd, PolyU's Department of Electrical Engineering has developed an innovative air-conditioning system for vehicles that can turn scorching summer heat into cool air without a single drop of gasoline.

Motorists are so used to turn on the engine for air-conditioning. Our solar-powered air-conditioning system for vehicles (SAV) will break this convention. Featuring photovoltaic technology and intelligent power control, SAV switches on-board air-conditioner to when petrol engine shuts off, and the switch-over is automatic and seamless.

Principal investigator of this project Prof Eric Cheng explained, "Drivers of minibuses or taxis can now switch off the engine but continue to stay cool while waiting for passengers at the station. In fact, our system helps extend the operation of air-conditioner for two more hours." Prof Cheng further stressed that this device can also give good power output even during cloudy or .

Similar to a big , this system has on the rooftop of the vehicle to collect power for storage in a battery to support a stand-alone electric air-conditioning unit when the is not running. The solar panel is made from bendy materials which can fit perfectly on any vehicle rooftop, giving it a sleek appearance. It also serves as a good thermal insulation for the interior and other valuable equipments inside the vehicle.

Idling not only pollutes the air, but is also bad for the engine as it may contaminate and accelerate the deterioration of components due to higher operational temperature and unnecessary prolonged operation. According to recent statistics, leaving a vehicle on idle for as short as 10 minutes a day will consume an average of 100 litres of petrol in one year. In other words, adopting our SAV can help save drivers' petrol and fuel cost.

PolyU's President Prof Timothy W. Tong hailed the device as a practical solution that could benefit thousands of professional drivers and pedestrians in the city. The installation of our SAV on a Swire Coca-Cola Hong Kong truck was first announced in October last year. A series of testing on the road have proven the system robust and effective. To make another milestone on the road to green transport, the system is now being widely deployed in public transport such as minibuses and taxis, as well as some commercial vehicles including an operation truck of the Airport Authority Hong Kong.

"We look forward to having more fruitful collaboration with Green Power Industrial Ltd and other industrial partners to build a low-carbon city. Together, we can jointly make a contribution for sustainable development of our community," said Prof Tong.

As part of an on-going mission in advancing technology that safeguards natural resources and our ecosystem, SAV is the latest from a stream of PolyU's green innovations with an aim to reduce harmful emissions and eliminate the effects of climate change. This system has also brought home two international awards from the 39th International Exhibition of Inventions of Geneva in April this year. This accolade will certainly serve as recognition of the hard work, the know-how and the dedication that PolyU researchers have put in creating meaningful innovations that move us towards a sustainable society.

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Provided by The Hong Kong Polytechnic University

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User comments : 10

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dschlink
5 / 5 (1) Oct 11, 2011
This would be especially useful for diesel vehicles. My van's manual explicitly states that repeated idling for more than 5 minutes at a time can damage the engine. I've seen the results, ain't pretty.
CapitalismPrevails
1 / 5 (1) Oct 11, 2011
I wonder how much charge this would provide for driving instead of a/c.
jerryd
5 / 5 (1) Oct 11, 2011
Won't work as not enough PV to power any known AC. Best to just use it to power a fan to keep temps at outside air temp.
tarheelchief
5 / 5 (1) Oct 11, 2011
This has been done on yachts for decades.If you could harness for recharging the batteries for power,and use it on freight trains as well you could make a fortune.
Howhot
3 / 5 (1) Oct 11, 2011
It's a great idea for EVs and if the AC isn't used, have the solar cells re-directed to charging that battery pack(s). Dump any excess back to the grid if you have enough spare battery capacity when you get home. For all of the million of commuters that drive to work, park the car for 8-9 hours we could solve the energy crisis.
Vendicar_Decarian
5 / 5 (1) Oct 12, 2011
"For all of the million of commuters that drive to work, park the car for 8-9 hours we could solve the energy crisis." - Howhot

Not even close.

Lets run some numbers. 400 million cars in the U.S. 1 square meter of roof area available, 8 hours of sunlight, 10 percent conversion efficiency.

1.5 kilowatts per square meter at 10 percent efficiency = 150 watts collected * 8 hours * 0.4 for the collection angle = 0.5 kilowatt hours of energy per car or roughly 200 million kilowatt hours of energy in total.

Average U.S. electric consumption is 24 kilowatt hours per day per household, so the amount of energy generated would be enough to power 8 million homes.
Bob_Kob
5 / 5 (1) Oct 12, 2011
Because every car is somewhere in direct sunlight 8 hours a day (i.e. not in undercover garage or parking lot).
a_n_k_u_r
5 / 5 (1) Oct 12, 2011
Harnessing energy from sun on vehicles make a LOT of sense:
1. Converting part of energy into electricity any way reduces heat.
2. The cost of electrical energy -- coming from gas/petrol -- is relatively higher than cost of electricity at home.
88HUX88
not rated yet Oct 12, 2011
First, for hot climates a safari roof is passive and cheaper and would reduce the load on any air conditioner. The world seems to have forgotten about safari roofs. Second, is this a fix for bad habits? Running a bus engine to cool one person; is there no alternative? What about providing shaded parking or somewhere cool for them to wait?
Howhot
not rated yet Oct 12, 2011
Vendicar, it also depends on the battery capacity carried with the vehicle too. I agree, i was stretching it a tad when I said "solve the energy crisis", but I could help play a part and if it help reduced you cost of ownership of an EV, or plugin hybrid, wouldn't everyone want to do it?

It seems very do-able technology-wise, just need solar panels shaped like body parts.