🚀 go-pugleaf

In this followup, I have uppercased Harry Spencer's comments to
make him look like a crude, boorish, shouting fellow. :) NOT REALLY. I did it
just to separate his text from my text, for readability. He is not really
shouting, and the tone of his posting was polite.

My sources for information are Encyclopaedia Britannica, Nasa Tech
Briefs, the CRC Handbook of Chemistry and Physics, Farrington Daniels'
"Direct use of the Sun's Energy", and a little personal research (the
stuff on the albedo of a solar cell, and its effective albedo).
Opinions and recollections are clearly marked.


In article <1990Dec28.210436.10601@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes:

>(1) SOLAR CELLS ARE EXPENSIVE TO MAKE AND DON'T LAST FOREVER.  (ALSO, THE
>	PRODUCTION PROCESSES ARE NOT PARTICULARLY "CLEAN" AND THE MORE
>	ADVANCED CELLS ARE OFTEN HAZARDOUS WASTES WHEN THEY ARE RETIRED.)

About a dollar a watt, for large installations. Five dollars a watt
for smaller installations. I wonder what the "real costs" of conventional
power are?

Dead solar cells can be found in a panel by photographing it with
infrared film. The cells that have died show up "brighter" in the photo,
because they are hotter,because they are not converting light to electricity,
and that difference shows up as heat. 

OPINION:Silicon solar cells do not represent much of a disposal
problem, at least not because of the silicon. They are probably good
candidates for recycling. Imagine how bad things would be with
selenium photocells.

>(2) EXTENSIVE ENERGY STORAGE OR EXTENSIVE LONG-RANGE POWER TRANSMISSION --
>	DIFFICULT AND EXPENSIVE EITHER WAY -- IS NEEDED TO COPE WITH
>	OUTAGES DUE TO NIGHT AND CLOUD.

OPINION:This a criticism more appropriate to small installations, that
are away from the power grid. The power grid would have a moderating
influence on local storage needs. A "large" power grid could also have
some portions of the grid illuminated while others were dark (the USA
don't stretch across enough time zones to make this one work).

RECOLLECTION:Frequently, it is cheaper to set up a solar/lead-acid
system than it is to run power to places that are not already on the
grid.

I couldn't find anything (in the time that I alloted to research this
posting) about the cost of lead-acid batters, which I guess to be the
most economical storage system.

>(3) SOLAR ENERGY IS THINLY SPREAD AND VERY LARGE COLLECTING AREAS ARE NEEDED.

1.920 calories/square centimeter/minute,
which is 22 watt-hours/square meter/minute.

These are calculations for a typical house (mine), which used 587 kwh
in november. I assume a 12 hour day, no degradation of the solar
constant during the morning and evening hours, and 16 percent
conversion efficiency. I come up with about 8 square meters of silicon
solar cell to satisfy my rather inefficient energy needs.


>(4) LARGE-SCALE SOLAR POWER SERIOUSLY CHANGES THE HEAT BALANCE OF THE
>	SURROUNDING AREA, SO IT IS NOT COMPLETELY CLEAN.  

Life systems are open systems. Nothing is completely clean.


>	IN PARTICULAR,
>	DESERT AREAS NORMALLY REFLECT MOST SUNLIGHT BACK OUT INTO SPACE,
>	BUT WHEN PAVED WITH SOLAR CELLS, MOST OF THE ENERGY IS RELEASED
>	AS HEAT INTO THE BIOSPHERE INSTEAD.

By "most" sunlight I assume that you mean more than 50%. Here are some
reflectivities of some common things:

		      percentage reflectivity
--------------------------------
EARTH (the planet)    36
concrete:             17 to 27
green forests:        5 to 10
moist plowed fields:  14 to 17
dark soil:            5 to 15
DESERT SOIL:          25 to 30
snow:                 45 to 90
clouds:               5 to 85
silicon solar cell:   about 6


Two thirds of the reflected light from the earth is caused by
reflection from cloud cover.

The low albedo of silicon solar cells is mitigated somewhat by the
fact that they convert about 16% of the sunlight that falls on them to
electricity. In this fashion, they display an "effective" albedo of
about 22% (6 + 16 percent). Looks like they would blend in well with
concrete.

Decide for yourself.

OPINION: Solar energy is a niche player now, but the niches are getting
larger.

>"THE AVERAGE POINTER, STATISTICALLY,    |HENRY SPENCER AT U OF TORONTO ZOOLOGY
>POINTS SOMEWHERE IN X." -HUGH REDELMEIER| HENRY@ZOO.TORONTO.EDU   UTZOO!HENRY


-- 
Dan Liddell    UUCP decwrl!teda!dll       TELEPHONE 4089805200 USA
curb your dogma.       The opinions and views expressed are Dan's.