Re: Seeking Fiscal Health Without Gas Tax

"Larry Gross" <gross.larry@xxxxxxxxx> wrote:

I presume you mean overhead/external lines for rail - right?

That would require fairly extensive new infrastructure, the price
which, would have to be traded off against the obstensibly lower price
of using grid-supplied electric. Not too different in some respects to
how long it would take for a hybrid car to recoup it's initial higher
price.

Yes, that is correct. There will be additional cost to upgrade the grid
to handle hybrid cars as well, since the power load will be so high.
That would include everything from central power plants, the
distribution network, local transformer substations, to the feed to
individual houses. It is not simply a matter of building a few power
plants. The cost of the general network upgrade would have to be retired
through increased energy rates, the same as the extra cost of the car.

One might presume that one "could" power a home with a backup
generator.

Backup power systems for homes are easily available and utilize
gasoline, desiel, natural gas, and propane but as far as I know -
home-based generation systems are more expensive (less efficient that
giant power plants?) - or else everyone would be buying their own
generators and power their own homes rather than buying electricity
off the grid - right?

The average thermal power plant in the US is something like 33%
efficient. There is also a loss of about 8% in the distribution
network, lowering the overall efficiency to about 30%.

The newest diesel engines are about 40% efficient at full load, but
their efficiency drops off at part load. A house has large swings in
demand, so a dedicated generator would have to have enough capacity to
handle the peak, and would run at partial load for the majority of the
time. For argument's sake, let's say they would be 35% efficient at the
duty cycle of a house. We also have to account for the efficiency loss
in the electrical part of the generator, which might be 5%. Therefore,
the efficiency of the home generator would be about 33%, or a bit better
than power from the national grid.

So why don't people just generate their own power? Because the price of
coal per unit if energy is about 1/4 that of the price of gasoline or
diesel fuel. In terms of energy input, it costs the power utility far
less to generate a kW of electricity than it would cost for small
diesel-driven plants. Even with infrastructure and labor, they can sell
power at about 10 cents a kW-h, while it would cost over twice that
price for an individual to generate power with his own diesel set, not
counting the capital cost and maintenance of the set.

Following this same logic... if you had a plug-in hybrid, you COULD
choose to power it off of your home-based backup power system.. but I
would suspect (perhaps wrongly) that buying your power off the grid
would be cheaper.

Is the claim that the gasoline engines in autos are more efficient
than large fixed power plants that provide grid power to your home?

An gasoline engine is about 35% efficient at rated load, but in a car
they run mostly a partial load, and their efficiency drops off
significantly at part load. A car in typical daily use has an overall
efficiency of about 22%.

If true.. why not use an auto engine to power your home? Just park
it.. take the wheels off,
disconnect the belts except for the water pump.. and keep on trucking.

A car would have even worse economics than a dedicated diesel generating
set.

Get yourself a junk car with a good engine.. and use the power grid as
a "backup" for the car engine.

I could be wrong.. but I think the economics are in reverse - and if
they are.. then it would seem that recharging your plug-in car would
be cheaper than using a gasoline-powered car.

It would be if the efficiency of the electric portion of the hybrid was
100 percent, but there are losses in charging and discharging the
batteries, and in the control system on the car. I understand that the
electric portion of Toyota's hybrid is something like 36% efficient, so
multiplying that by the efficiency of the power grid gives an overall
thermal efficiency of only about 11%.

Therefore, from an efficiency measure, a grid-powered hybrid would be a
disaster in comparison to other ways of powering a car. It's only the
lower cost of electricity that brings the hybrid somewhat closer to a
reasonable economic proposition. Much depends on the cost of
electricity, and how the cost of the grid upgrade would be passed on to
the users.
.

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