The ovens that we drive

Unless you work in a steel factory, or a similar industrial plant, the hottest temperatures you experience occur when you get into a car parked in the sun.

Even on normal summer days, the inside temperature in a car with dark-colored paint can hit 160 degrees, and some of the metal or plastic surfaces can reach a skin-burning 200 degrees, according to experts at the Society of Automotive Engineers.

It is one of the most uncomfortable aspects of driving. It is also extremely dangerous, causing 35 to 40 deaths per year of children left in parked cars, according to the pioneering work of Janette Fennell, founder of Kids and Cars, a safety organization focused on child auto safety.

Auto manufacturers like to boast about the luxury of their interiors, citing such things as advanced instrument panels, navigational systems and high-end sound systems. And there have been plenty of convenience items of dubious merit, such as picnic benches in the hatchback.

How about a car that doesn’t bake the occupants when they get in?

I have been examining this issue for several months, convinced that simple solutions must exist to help reduce the interior temperatures of vehicles parked in the sun.

It’s been tried. Fifteen years ago, Mazda introduced a solar-powered ventilation system that would continuously flush hot air out of a vehicle parked in the sun. A solar cell array was mounted on the moon roof, supplying power to a small fan that drew in outside air.

The system worked only when the car was parked in the sun, exactly when it was needed. It was not hooked up to the car’s battery and therefore could not drain it. A Mazda spokesman confirmed that the system was offered as an option and that it was dropped for reasons he couldn’t explain.

Could such a fan work today? I asked safety experts, emergency room doctors and air-conditioning engineers.

Nobody seems to have a definitive answer, but most agree that anything that would help cool the interior temperature of a car would not only improve the comfort of adults but also perhaps make a small contribution to the safety of children trapped in cars.

Reducing a vehicle’s inside air temperature also would allow manufacturers to use smaller air conditioners. The highest demand on an auto air conditioner occurs after the car is parked in the sun, when occupants want hot air cooled quickly.

As a result, auto air conditioners are powerful enough to cool a medium-sized house, providing several tons of cooling capacity, said Ward Atkinson, chairman of the Society of Automotive Engineers committee that writes standards for vehicle air conditioning systems. That makes them extremely energy-hungry, particularly at start-up.

Conventional wisdom has long held that running a vehicle air conditioner causes a 20% drop in fuel economy, though Atkinson said the actual economy loss depends on many complex factors. The biggest drop occurs on start up after a car is parked in the sun and is then driven in slow city traffic. Conversely, the loss is much less at freeway speeds, particularly assuming the occupants would roll the windows down with the air conditioner off. The lowered windows upset a vehicle’s aerodynamics, which also hurts fuel efficiency, Atkinson said.

With gasoline above $3 per gallon, the heat is now on the engineers to find better technology.

SAE is convening a major conference in Phoenix this week to examine improvements to mobile air-conditioning systems, a program that aims to increase efficiency by 30%.

They have equipped a prototype car with a variety of improvements, including special paints and glass that reflect solar heat and insulation on the non-glass portions of the vehicle body. The experiment also includes a fan powered by solar cells to purge vehicle air. Engineers will compare two cars, the specially equipped vehicle and an identical production line car, to study temperatures after the vehicles are parked in the sun.

Atkinson said the jury is still out on the fan system. To reduce inside vehicle temperatures requires moving a lot of air, which requires a lot of power. He estimates roughly 65 watts of power is needed, which translates to a lot of solar cells.

It is important to remember that any fan system will not reduce the interior temperatures to the same level as the exterior. Solar heating of glass, plastic and metal causes tremendous radiation energy in a vehicle. But even a 10- to 15-degree reduction can be important.

It appears Mazda might have had the right idea 15 years ago.

Gadgets that use solar power for a fan are already sold on the Internet for as little as $30. These are typically placed in a crack in the window when you park, which is not particularly convenient. The solar arrays are also fairly small, leading me to think they don’t have the kind of capacity that would be useful.

Will people be willing to pay for a system that works?

I say yes. People will pay to not have their legs fried on hot leather seats and fingers seared on hot steering wheels. If people are willing to pay for heated seats to keep their rear ends warm in cold weather, why not devices for hot-weather relief?

Next, I’ll look into the tragic issue of children who die in parked vehicles and why so little is being done to address the problem. Are cooling fans part of the solution? Or would they encourage reckless behavior by parents who might think such systems make it safe to leave kids in the car?

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Contact Ralph Vartabedian at ralph.vartabedian@latimes.com.