Thursday, September 15, 2011

About that plug-in automobile ...

David Cohen is a classmate, an engineer, and a writer on energy topics. Here is his take on the Nissan Leaf, Chevy Volt, and other super-green plug-in vehicles:

Our government is embarked on a mission to support the development and production of rechargeable electric vehicles. The reason for this support is to place vehicles on the street that produce no carbon dioxide (CO2) emissions and other exhaust pollutants and greenhouse gases in the air of our city streets.

On the surface we can see and understand the desire to minimize the release of carbon products into the earth's atmosphere. However few people in our society seem to realize that at the present time this is a serious mistake. The cost in money and fossil energy actually exceeds that of a vehicle powered by an internal combustion (IC) engine. In addition, the greenhouse gas release and CO2 emission also exceeds that of a normal IC

What is going on here? How is that possible?

The answer is simple and is obvious to those who know where our electricity comes from. 50% of our electric power originates in power plants fueled by coal. Another 20% is derived from the combustion of natural gas. Up to 3% is derived from burning fuel oil.

Only about 27% of our electric power typically comes from green or carbon free [i.e., nuclear] sources. In fact our electric grid is responsible for more greenhouse gas and carbon emissions than our entire fleet of fuel burning vehicles.

This simply means that we will increase atmospheric pollutants and carbon bearing products into the atmosphere instead of reducing them for every rechargeable electric vehicle that is placed on the road....

Will rechargeable electric vehicles ever be a good idea? Yes indeed, but it requires a green energy source. That is in the far distant future. At present our transportation fleet can save green house gas by raising efficiency and not tapping into our electric grid. Hybrid vehicle technology is our best hope for the near future. The all-electric vehicle may become attractive 50 to 100 years into the future if our power grid becomes 2 to 4 times larger than it is at present, and consumption of fossil fuel at the power source becomes significantly reduced below its current level.

There is currently one other potential flaw in the rechargeable electric vehicle idea. That flaw is grid capacity. Our electric grid is nowhere near big enough to support tens or hundreds of thousands of electric vehicles that may be recharging every night.

The electric vehicle potential must be guided by a professional systems engineering team that will control the growth of this idea to meet our needs as a society. We should not delude ourselves into believing that this is an idea whose time has now come. It hasn't.
Blue skies! -- Dan Ford


At 8:41 PM, Anonymous Anonymous said...

According to the media, an electric car requires about 8 hours to recharge enough to travel approximately 40 miles (+/-20). What has so far escaped me is the actual amount and cost of electical energy (1 kwh=3.6 million joules) stored in the battery bank, compared to the amount and cost of a similar amount of energy delivered by a standard IC engine. Delivery to the outlet in your house entails enormous fractional losses from generation and transmission, from the coal. Not only is CO2 vastly increased, but the grid could not handle the increased loads. And most people would be recharging at night, when solar and wind "green" power is at a minimum, meaning backup generation would be maximally strained.

At 6:43 AM, Blogger Dan Ford said...

As to the last point, isn't it true that electricity demand goes down at night? I think that was the idea behind pumped-storage facilities such as one I saw in New Jersey, where power from a nuclear plant pumped water uphill at night, so it could run downhill and run a hydro generator during peak power in the afternoons. When we have power cuts here in New Hampshire, they are generally on hot summer afternoons. Blue skies! -- Dan Ford

At 12:05 PM, Blogger Peter Buckner said...

Couple comments, as I've been driving an electric car for nearly ten years. Recharge rates depend on the input voltage: higher voltage systems charge faster. Toyota's Rav4EV (2002) uses a 300 volt system which charges the equivalent of 20 miles per hour. I'd guess your "according to the media" number would refer to trickle chargers which use household current, rather than your standard garage-installed system. EVEN BURNING COAL, we generate less pollution than most cars burning petroleum. The benefit, of course, is that we don't have to: with my increased electricity bill, I found Solar Energy to be economical. As for the grid, your observation is correct, the grid is underutilized at night: usage graphs tend to peak with air-conditioner usage in mid-afternoons. As long as charging is shifted away from peak periods, (easily done through time-of-use pricing!) the grid will not have a problem. Sure... if 100's of millions of cars convert to electric by the end of the year we may have a grid problem, but I think that's not a useful thing to worry about.


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