From: dietz@cs.rochester.edu (Paul Dietz)
Newsgroups: sci.energy
Subject: Re: SOLAR efficiency
Date: 15 Sep 92 16:51:33 GMT
Organization: Computer Science Department University of Rochester

In article <BuMECK.7I4@quake.sylmar.ca.us> brian@quake.sylmar.ca.us (Brian K. Yoder) writes:

  > You make it sound like this land is being used for nothing and has
  > no competing demands.

Not at all.  What I argued is that the land needs are small compared
to physical limits.

To compare against competing demands, we need only look at the *cost*
of land.  This is small in much of the west, much smaller than the
cost of the collectors.

  > need some kind of storage system to allow the power generated on sunny 
  > days to be used at night or on cloudy days.

Whoa.  Storage is needed if solar is to take on a major fraction of
electricity demand, say more than 10-20%.  Even 10-20% penetration is
not chicken feed.

  >> (2) is currently true, to some extent, but the cost/watt can be
  >> reduced without increasing the efficiency at all, simply by finding
  >> ways to make the collectors more cheaply.  

  > It is also necessary to have storage systems to allow people to use electricity
  > at night, and these multiply the inefficiency and cost.

This is only necessary if solar is to take up more than a certain
fraction of electricity demand, a fraction that is nowhere near being
filled.  Storage is not yet the constraint on PV cell market
penetration.  In fact, improved storage would likely *harm* the PV
cell market, by allowing baseload powerplants to supply peaking power.

  >> Economies of scale would no
  >> doubt apply to manufacture of collectors as they do to all other
  >> manufactured goods.  DOE estimates that costs will fall 70% for every
  >> tenfold increase in production experience and 40% for each tenfold
  >> increase in annual output.  PV has many profitable niche applications,
  >> and sales are growing about 20%/year in the US.

  > Economies of scale can help, but can't necessarily make the product cheap or
  > economical.  This sounds like wishful thinking to me.

No wishful thinking, just analysis of what goes into making PV modules
(mostly labor, now), coupled with experience in just about all other
industries.   Many people have looked at what can be done via
automation as PV cell manufacture gets large enough to justify
the investment.  Significant savings are possible.

The fact that the PV market is so small no (about 55 MW/year production,
worldwide) shows that there is a lot of room to run down that learning
curve.

  >> Module efficiency does affect balance of system costs (supports,
  >> installation, etc.)  DOE thinks 15% efficiency is the goal to shoot
  >> for for flat plate collectors.
  >
  > And then what?  Will PV power be at a break-even relative to coal or nuclear?
  > Or is that the point at which they think they will be able to ram it
  > down our throats and accept the economic losses?

If you look at the lowest cost coal and nuclear plants, then, no, I
don't think even this is immediately competitive, for the utility, for
baseload power, especially if PV is compared to avoided costs (as
low as $.01-.02/kWh for coal and nuclear plants).  This ignores
capital cost and (for coal) the cost of scrubbing and CO2 emissions
(if you want to include that).

However.  Many utilities pay more for their power, and charge much
more than this, especially to residential users.  There's a real
possibility that cheaper PV arrays will place a ceiling on utility
rates, beyond which they go only at the risk of permanent loss of
demand.  It's possible we could see some utilities entering a "death
spiral" of reduced demand leading to higher rates, and ultimately to
bankruptcy (cogeneration is another, perhaps more likely, road to this
end).

A datum: in Rochester, NY, users using > 25,000 kWh/year are being
placed on time of use electric rates.  The rate during the 500-hour
summer peak (weekdays, 11am-5pm) is nearly $.24/kWh.  PV systems need
not decline in price by very much to be able to beat this price, even
in Rochester.

	Paul F. Dietz
	dietz@cs.rochester.edu