From: cir@festival.ed.ac.uk (C Revie)
Newsgroups: sci.energy
Subject: Re: Renewable energy from the sun
Date: 18 Nov 92 14:21:25 GMT

gary@ke4zv.uucp (Gary Coffman) writes:

>Our current energy consumption, from all sources, is 1/100,000th of
>the energy received by Earth from the Sun. That's 0.001%, the change
>in the Solar Constant during a 22 year solar cycle is more than an
>order of magnitude greater than that. Our energy use is an *insignificant*
>fraction of the natural *variation* in solar input to the Earth. We
>are *not* overloading the Earth's energy balance due to the heat liberated
>by burning fossil fuels.

Ok, no arguement, but by burning fossil fuels we are increasing the
amount of CO2 in the atmosphere. There is good evidence to support this.
Granted over the long term, the the amount of Co2 in the atmosphere has
been steadily decreasing. But in the short term (ie in several human
lifetimes) we are producing more CO2 that this system can cope with. The
effects of this may be profound and in some case disasterous

>>Admittedly these system are expensive, but this is due to the present
>>miserly levels of investment that they receive, compared with fossil
>>fuels. 

>Your naive faith in the power of government directed R&D is touching,
>but there is *no* assurance that *any* amount of R&D funding can break
>fundamental Carnot limits on the low grade energy of diffuse sunlight.

I'm not suggesting for one minute that by throwing money at the problem
we will be able to change physical laws, or subvert them or whatever. I
was just trying to point out the imbalance in research. 

>>The other advantage of solar systems is that you don't get any
>>problematic side effects, unlike fusion and fission. Yes burning
>>biofuels gives off CO2, however this is CO2 which was verily recently in
>>the air taken in by plants, it should not therfore alter the amount of
>>CO2 going round the system. 

>Nor does burning fossil, on a longer timescale. We can't say *what* timescale
>is the proper one to measure this. The carbon cycle isn't understood to
>within several orders of magnitude. There is considerable evidence that
>some of the larger CO2 sinks are inorganic. Therefore it doesn't matter
>much whether the CO2 is generated by burning wood or coal. In fact, the
>deforestation from burning wood changes the albedo of the Earth a measurable
>amount and may cause more harm than burning coal. Use of fission has
>demonstrably less damaging effect on the environment than burning wood,
>or coal, or oil. Fusion should be even cleaner.

Two Words - Radioactive waste. Without trying to be prejudiced, it is a
problem. Yes the effects on greenhouse gas emissions would be
beneficial, but at what price? 

>>As the population grows, living within the capacity of the planets
>>systems will become more important, a move to solar tecnologies is thus
>>of prime importance.

>That hasn't been proven. Indeed it is just an article of faith in some
>quarters. 
  
Yes but equally it has not been proven that this is not the case. And
I'd rather not carry out some giant experiment to prove it either way. At the
moment the G7 nations account for a very large proprtion of energy use
in the world (I'm sorry I'don't have exact figures to hand). 7 countries
out of over 150 (ok some of these are very small). But nations China and
India have nearly 2 billion people between them, just under half the
present population of the planet! Imagine that these two countries raise
their energy consumption per capita to something like Uk or the USA?
Under these conditions a 100 fold increase in present energy consumption
is quite likely.

Solar technologies include very simple and easy to use ideas and
techniques, which can be used now. There is potential in fusion but
current estimates are that it will not be available as a viable source
of power for 40 - 50 years.

Chris