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#71842 - 11/07/06 11:08 PM Solar power efficiency  
WFO  Offline
Joined: Sep 2005
Posts: 202
Cat Spring, TX
In a previous thread on energy consumption, several comments were made about the efficiency of solar energy (i.e., the cost of producing it versus the energy it produces).

Being from a de-regulated state that has requirements to allow distributed generation, (and working for a Poco) I'm very interested in this and would appreciate any of those contributors that would like to post links to support their claims.

I'm not for or against at this point.... I'd just like to do a little research.

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#71843 - 11/08/06 04:06 AM Re: Solar power efficiency  
Kenbo  Offline
Joined: Apr 2006
Posts: 233
Good topic
I also wish to know more about this subject so will be watching this trhread closely.

As some of you may know I am writting teaching modules for the "Scottish Qualifications Authoritiy" at the moment and have written in that students are to look at renewable sources of generation. Not only lage scale systems but also small micro generation sets.


der Gro├čvater

#71844 - 11/08/06 07:49 AM Re: Solar power efficiency  
SteveFehr  Offline
Joined: Mar 2005
Posts: 1,198
Chesapeake, VA
At the moment, amorphous silicon (a-Si) panels are the most common for residential use, as they're by far the cheapest watt-for-dollar. The technology is changing all the time, and this promises to be cheaper. Last I checked, the cost of 8% efficient a-Si solar panel was approximately $1000/square meter. These panels will convert about 8% of the solar flux reaching them into DC electricity. (Inverter required, batteries optional) Higher efficiency panels exist, but are outrageously expensive and really only practical for satellites and mars rovers.

About 1370W/m2 of the sun's energy reaches the earth. Multiply that by the cosine of your lattitude. Additional energy is absorbed or reflected by the atmosphere. And then factor in the efficiency of your cell. In the very best case scenario (high noon on a clear day in Texas), you might get 540W/m2 or so striking your panel and about 43W out. In areas further north, it's obviously far less.

Now, panels are always touted as 60W or 100W panels, but that's PEAK, and the actual output depends greatly on your geographic area. The average amount of solar energy hitting that panel on a clear day (nights factored in) can be anywhere from 71W/m2 to 240W/m2- which on an 8% panel would provide about 6-20W of power per square meter (time averaged). Net energy output in a the arizona desert might be as high as 175kWh/year for each square meter of panel. (That's about $12 At 7 cents per kWh)

Here's a good cross-section of solar panel prices:

[This message has been edited by SteveFehr (edited 11-08-2006).]

#71845 - 11/08/06 10:27 AM Re: Solar power efficiency  
Zapped  Offline
Joined: Oct 2002
Posts: 482
Huntington Beach, CA, USA
Very interesting stuff Steve. I'm glad you posted.

My problem is still the cost of the generation units. Low competition and equally low interest by the general public contributes to a very high mark-up factor. Add to each unit sold the cost of R & D, and the W:$ ratios is still very high.

If you doubt my statement that the mark-up is high, check out the cost for the 2 diodes on the page that Steve linked. They want $14 for a couple of $.50 diodes.

With the rising cost of power, hopefully more companies will enter the market and renewable energy, such as solar, will start to become more effecient, and the costs low enough to be implimented by the average family.

#71846 - 11/08/06 11:50 AM Re: Solar power efficiency  
Almost Fried  Offline
Joined: Sep 2006
Posts: 98
Madison County, Ark. USA
A good source of the panels and associated hardware, awa technical information can be found at Real Goods, Ukiah, Calif. they have a web site, probably but I'm not sure of that.

#71847 - 11/08/06 12:41 PM Re: Solar power efficiency  
SteveFehr  Offline
Joined: Mar 2005
Posts: 1,198
Chesapeake, VA
amorphous silicon is WAY cheaper than monocrystalline silicon, but still WAY expensive to process. New polymer based technologies will hopefully bring costs down further.

I hope we all recognize that solar isn't terribly practical (regardless of cost) for a primary source of power due to the super-low energy density, but if it was affordable and widespread (EG, if solar panels replaced asphalt shingles), it could still make a few %dent in our energy consumption.

#71848 - 11/08/06 02:28 PM Re: Solar power efficiency  
JJM  Offline
Joined: Oct 2005
Posts: 100
This link will give you some insight into silicon wafer processing:

Pennsylvania State University has quite a bit of interesting information regarding solar technology, as well as new solar technologies and nanotechnology which shows promise in improving manfacturing processes:

Professor Craig Grimes of the Materials Science Department has an intricate knowledge of these facts:

He has been working to reduce manfacturing costs and the energy input to make solar somewhat viable.


[This message has been edited by JJM (edited 11-08-2006).]

#71849 - 11/08/06 02:36 PM Re: Solar power efficiency  
winnie  Offline
Joined: Sep 2003
Posts: 649
boston, ma
Perhaps a slightly different question is in order. The _energy efficiency_ of solar energy is very much secondary to the _monetary efficiency_ of solar energy.

The total solar energy hitting the Earth's surface is something like 10000x the total energy that humans use (electrical power, nuclear, fuel burning, etc.) It doesn't matter if your power source converts solar power to electrical power with 95% efficiency or 5% efficiency, what really matters is how much it costs to get each watt of output. Efficiency does come into play, because a low efficiency system will require more surface area, and this means greater installation costs.

Photovoltaic solar power is still way to expensive to replace most of our electrical power use, although it is currently quite viable for small loads away from the grid, where the cost of the solar cells is less than the cost of installing wires.

_Wind_ power is essentially very inefficient solar power, where the solar collector surface already exists and is free. Wind power is currently almost at break-even with new natural gas fired power plants.


#71850 - 11/08/06 10:16 PM Re: Solar power efficiency  
WFO  Offline
Joined: Sep 2005
Posts: 202
Cat Spring, TX
In other words, the energy input needed to manufacture a PV solar panel will far exceed the expected energy output over its anticipated lifetime

This is no longer true. New a-Si PV cells have full energy payback in as little as 2 years, and flexible polymer cells are being developed that are even cheaper, both in terms of dollars and energy.

Perhaps a slightly different question is in order. The _energy efficiency_ of solar energy is very much secondary to the _monetary efficiency_ of solar energy.

These three quotes (two from a previous thread) sum up my question. I have heard before that it took more energy to produce this product than could be recovered from it. What I'm looking for is a reference supporting or refuting it.

[This message has been edited by WFO (edited 11-08-2006).]

#71851 - 11/08/06 11:06 PM Re: Solar power efficiency  
Almost Fried  Offline
Joined: Sep 2006
Posts: 98
Madison County, Ark. USA
Not pertaining to efficiency, but to possibility, some folks live where the cost of poco 'lectric is prohibitive. I have friends who live down in a remote valley, an hour and a half from the city. They own 10 acres, free and clear, have a comfortable home, spacious shop, huge garden. Their electricity is from PV with a small pelton wheel driven generator that supplements the PV cells in the winter when the spring flows well. They have an inverter for the 120 volt stuff, have a table saw but no drier, and the only bills they have to pay is telephone and real estate taxes. (the telco wanted
$ 3,000, Scott and his neighbors bought a mile+ of cable, hired a friend to plow the cable in and they had phone service for
$ 300 up front)He has a Woodmizer sawmill which he carts around to do contract cutting, drive 2 nice vehicles. Their lifestyle is not for everyone, but the level of stress in their lives is miniscule compared to most of us. They are physically active and stay in good health, grow most of their own food.The cash from the sawmill replaces vehicles and pays for Dr. visits(rare) Their lifestyle is admirable, but I need to be a little closer in.

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