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Currently available silicon solar cells have efficiencies that are about
and amorphous silicon sheet converters have efficiencies of 18 to 20%.
However, not all the solar energy has to go into electricity. Solarthermal
for hot water and heating is quite practical, at much higher efficiencies.
From: Rick Tarara [mailto:rbtarara@SPRYNET.COM]
Sent: Wednesday, June 20, 2001 10:41 AM
Subject: Re: Solar and renewable energy
A couple of nitpicks:
The 30 square meter figure generates 7.2 kW AT 100% EFFICIENCY! At least
the photovoltaic world, currently 15% is about tops and maybe 30%ultimately
attainable. So that number looks too low by a factor of at least 3 andthought
To supply transportation needs (portable fuel) and the like, there will be
considerable conversion losses and then perhaps some thermodynamic
efficiency factors depending on how the fuels are used.
The .02% solar harvest figure doesn't agree with the 30 m^2 figure either.
At 30 m^2 the total collection area would be 180,000 km^2 while the .02%
figure gives 515 million km^2.
All calculations were done quickly, so I might have made an error--have to
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: "Larry Woolf" <larry.woolf@GAT.COM>
Sent: Wednesday, June 20, 2001 11:25 AM
Subject: Solar and renewable energy
To: Phys-L list
Given all of the discussions about solar energy and renewables, I
heat.you might find the following letters of interest. The IEEE is quiteof
involved in this area.
Following is an interesting and fundamental perspective on the abundance
solar energy from Professor Helmut Burkhardt of Ryersonrenewables,
For an overview forecast of economic and practical potential of
including solar, to meet our long term energy needs, see
Walter Short's Seattle presentation recorded in IEEE Power Engineering
Review, April 2001, Page 12.
Secretary and Acting Chair
IEEE WG on Implementing Technology to Limit Climate Change
Ryerson; June 19, 2001
Thank you for the information. You have created a most interesting IEEE
group . I would like to get a message to groups like yours.
Scientifically, humankind has no energy problem. The sun delivers to
the surface of the earth 25 000 kW for each one of the planets 6 billion
citizens, 0.24 kw/m2 on a yearly global average on a horizontal surface.
The global average total energy use rate is presently 2.3 kW per person.
A decent European life style can be sustained with 5 kW for each human
being. This means, we have to harvest only 0.02% of the sunlight to
energy needs forever.
With technically reasonable efficiency, and solar cogeneration we need a
collector surface of 30 m2 /person to have all the energy needs,
including transportation hydrogen, industry and home electricity and
comparison, sustainable agriculture requires 2000 m2 of fertile land to
grow the food for one person. Everybody should know this scientific
feasibility of solar energy; it is a simple back of the envelope
A solar world energy system is also technically feasible, and economic
feasibility is already achieved in some situations, and close in general
if we consider the environmental and social cost of other options.
However, few realize that we have this abundance of power delivered to
doorsteps. We are stuck in the idea of needing fossil fuels or nuclear
lack of awareness of the huge potential of solar energy is obvious in US
President Bush's reaction to the California electricity shortage: --
Drill for more oil.
Helmut (Ken) Burkhardt
Adjunct Professor of Physics
Ryerson Polytechnic University
Toronto ON Canada M5B 2K3
Tel: 416-979-5000 x 7246