Monday, March 30, 2009

Why cars can't really be green with today's technology

Instead of trying to make the car green, we should just be using the car less and trying to make our cities green with more density, transit and pedestrian amenities.

Green cars are kind of an oxymoron.

For instance, electric cars have a lot of technical obstacles to being green and practical. According to a December 5 NPR Science Friday show that I blogged about then, our best battery for storing power in a car isn't that good. The lithium ion battery only stores around 1/100Th the amount of energy that similar weight in gasoline stores. Thus the electric car doesn't have much of either power or range.

* That tidbit from a book titled "Physics for Future Presidents," by a Richard Muller.

Of course, we might be able to improve the battery, but I don't think that technology is here yet.

I would guess, most electric cars save energy by just being lighter and more aerodynamic. This means it's scary to be on the freeway around all those other heavy cars and trucks if you and your family are in a pop can.

No wonder bigger cars become more popular when gas prices are low, as gas prices currently are. Low compared to summer of 2008.

Then the power has to come from somewhere.

Coal power plants?


Wind and solar are OK, but expensive and we get very little of our energy from those sources currently.

Hybrid "gas electric" cars are another idea.

From my understanding of the physics, these are better at lower speeds where there is stop and go driving.

Gas engines don't take well to "stop and go" so the hybrid allows the gas engine to run more steady and efficient while the electric motor takes care of the stop and go.

Also the gas motor can be smaller since it gradually builds up charge while electric motors provide those brief moments of "get up and go" for acceleration.

Electric motors provide regenerative braking for downhill.

Problem is, hybrids aren't much of an advantage at steady highway speeds; especially on the flat, from what I understand. If one is just driving down the freeway at 70 mph, that means pushing against the constant wind. At traditional highway speeds, one just needs lots of power over the long haul. I don't think the hybrid is an advantage here.

Maybe we need lower speed limits?

Then there's a whole raft of other problems associated with automobiles.

Space taken for parking and traffic means impervious surfaces; one of our biggest water resource problems.

The automobile makes sprawl more likely. Often sprawl is even mandated with parking requirement and zoning rules.

I can go on, and on.

Really, if we want a greener tomorrow, we need to change city planning so cars are less needed.

I bicycle, for instance. I live close enough to my work to walk. Our local transit is getting better. I'm a fan of density and pedestrian oriented city planning.

Changing lifestyles also. There is a whole lot more that we can do for a greener tomorrow than just bang our heads against a brick wall trying to come up with green cars.

For both safety and fuel efficiency, the answer isn't tiny cars, at least on the highway.

A better answer is public transit. Per passenger mile, the bus is both safe and green if close to fully occupied.

Cars can't really be green until we get even more advanced technology.

Maybe someday there will be a car that, for instance, takes up no space for parking. A car that one can fold up and put in their pocket when not in use.

Can Detroit build such a car? Asking for the improbable?


David Barts said...

Heh. One of my nicknames for electric cars is "coal-fired cars". Because, in most of the country (not here in the Pacific Northwest, where hydro is still the #1 power source), that's precisely what they are.

Robert said...

Thanks for the comment. That's a very good point. Even here in the Northwest more and more of our power is coming from non hydro sources as time goes on. The hydro power sources are limited and population keeps growing. Wind power helps, but we have some coal plants also. Pacific Northwest has been adding some natural gas fired power plants in recent years.