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Re: Fuel Cells and "green" energy

I believe that it is a BIG jump from using solar and wind as peak energy-use
supplements to relying on these sources as THE MAIN energy sources (as some
environmental groups would have it.) As long as we maintain our coal, gas,
and nuclear plants then wind and solar can be used to avoid building more
plants. The question is, what happens when we finally agree to CO2 limits
or when the natural gas and petroleum either run out or become too damn
expensive to use? That's when we have to talk about renewables providing
most if not all of our energy demands. In the 'GreenPeace' model (only wind
and solar) you then need a 3000 fold increase in wind and solar (at today's
demand which will have increased due to population increases) and that is
using the wind and solar directly. In a model that eliminates gas and oil
and limits coal to 15-25% of total energy production, you pretty much have
to ramp up the wind and solar to about 50% or more (with hydro, geothermal,
and biomass making up the rest). At those percentages you will need a major
storage technique.

If hydrogen is used in a thermodynamic cycle, then I think my factor of 4
holds for each kWh provided. With more efficient systems it will still be a
factor of 2-3 kWh generated for each kWh actually delivered to consumers.
Granted that some of the wind/solar can be delivered directly but probably
not all that much for the eastern third of the U.S. I'm really only saying
that this needs to be factored into the cost estimates for renewable systems
so that the consumer/taxpayer is not 'surprised' by the final bill.

Here in the Midwest, we are still paying less than $.10/kWh with no peak
hour increases, at least to consumers. Let me suggest that it is a
difficult task to ask consumers to lower their usage during these times
because this IS when they are getting home, preparing meals, cooling down or
heating up their homes (with their efficient programmable thermostats),
turning on lights because night is falling, etc. It will probably take a
lot more in the way of staggered work shifts (much as is done in DC to ease
the traffic problems) to really redistribute the energy use (and we're
primarily talking ELECTRICAL use here) more uniformly over the day.

I'm also curious as to what happen to these solar panels on roofs during
hail storms and during typical northern winters!


Richard W. Tarara
Associate Professor of Physics
Department of Chemistry & Physics
Saint Mary's College
Notre Dame, IN 46556

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----- Original Message -----
From: "Daniel Schroeder" <DSCHROEDER@CC.WEBER.EDU>
I think your factor of 4 is overly pessimistic. Again, remember that
the conversion losses will apply only to a portion of the energy, not
to all of it. Besides immediate use of electricity, there's also solar
space heating and water heating which don't even suffer from the
low efficiency of photovoltaics. Some energy can be stored in
pumped hydropower facilities, which are much more than 25% efficient.
Even when we need to use hydrogen for energy storage, it is
quite possible to convert that hydrogen to electricity at better
than 50% efficiency. Combined-cycle gas-fired plants already do
better than 50%, and fuel cells may do better still, as you say.
For transportation, we currently live with engines that are only
about 25% efficient. Replace those with 50%-efficient fuel cells
and you can probably live with the energy cost of producing the
hydrogen in the first place.

Currently, many utility customers pay higher rates for electricity
at times of peak demand, because it costs more to generate the
extra electricity at those times. In the western U.S., peak
electricity prices paid by utilities have been skyrocketing, as
I'm sure you've read in the news. In a future economy based
mostly on renewables, electricity prices will probably be much
higher at times when the sun isn't shining and/or the wind isn't
blowing. This will encourage customers to use less electricity
at those times, just as many large industries already use less
electricity when they have to pay peak rates. It isn't obvious
to me that the overall inconveniences will be any greater than
the ones we currently live with (especially when you factor in
the environmental costs of current energy sources).