Posted on 07/15/2003 3:16:56 AM PDT by Boot Hill
Here is what the acolytes of solar power don't want you to know...
These are the essentials you need in order to appreciate the absurdity of using solar cell power systems as any kind of sensible alternative. After you read this, ask yourself again how much sense solar power really makes.
THIS IS WHAT HAPPENS TO THE SUN'S ENERGY WHEN
WE USE SOLAR CELLS TO GENERATE ELECTRICITY:
| SOURCE | LOSS - % | POWER - W/m2 | |
|---|---|---|---|
| 1. | solar constant | -- | 1370W |
| 2. | atmosphere | 27 | 1000W |
| 3. | clouds | 21 | 790W |
| 4. | sun angle1 | 49 | 403W |
| 5. | night2 | 50 | 201W |
| 6. | cell efficiency3 | 85 | 30W |
| 7. | dust/reflection4 | 10 | 27W |
| 8. | packaging5 | 20 | 22W |
| 9. | DC to AC inverter | 25 | 16W |
| 10. | storage | 30 | 11W |
| Source Notes: 1. Calculated for both hour angle and a latitude angle of 37º. 2. See link. Continental U.S. average sunshine is 4.8 kilowatt-hours/ square meter/day, or 200 watts/square meter. That value is nearly identical with total losses shown for items 1-5 above. 3. See table on linked page. 4. Dust, bird droppings, scratches, etc. estimated to be about 4%. Reflections, per Fresnel's Law, would be another 6%. 5. See link for data sheet on typical solar panel. Data shows an overall efficiency of 10.3%, at nominal conditions. This is nearly identical with total losses shown for items 6-8 above. |
|||
Net efficiency = 11.4 Watts/m2 or a mere 0.83% (!)
But read on, it gets worse.
Here is an example:
Siemens Solar (now Shell Solar) produces a popular line of large solar arrays intended for commercial, industrial and consumer applications. A big seller is their SP-150, supposedly a 150 watt unit that measures 1.32 square meters. The problem is, it only produces 150 watts under carefully controlled laboratory conditions where the incident light intensity is boosted to 1000 watts per square meter (unrealistically high, see items 2 and 3 in above table) and the PV cells are artificially cooled to 25º C. But when Shell tests that same unit under more realistic conditions of 800 watts per square meter and little cooling for the PV cells, the output drops to 109 watts. When sun angle and night time are factored in (see items 4 and 5 in above table), the average level of power production drops to a piddling 28 watts. (That is only 21 watts per square meter(!) which is nearly identical to the value shown for item 8 in the above table.) [+] [+]
In quantity, this unit sells for $700. That calculates out to $25 per watt. By way of comparison, the initial capitalization cost for a conventional power plant is on the order of $0.75 to $1.00 per watt. That makes the solar "alternative" 33 times more expensive than the conventional power plants of today, and we haven't even figured in the additional cost of the inverters and power storage systems that solar needs (or the land acquisition costs).
Solar proponents would be quick to point out that, while the capitalization costs may be higher for solar, they don't need to purchase the expensive fossil fuels that conventional plants use. While that is true, what they aren't telling you is that the cost of financing the much higher initial debt load for solar, is greater than the cost of the fuels that conventional plants use. (TANSTAAFL !)
Is there any use for solar power that makes sense?
Yes, solar power makes sense in those limited applications where the customer does not have convenient or economic access to the power grid, such as with remote country or mountain top homes. It is also useful for powering mobile or portable equipment such as utility, emergency, scientific devices, etc., where it is not otherwise feasible to hook to the power grid.
But other than those narrow exceptions, it makes no economic, engineering, ecological or practical sense to use solar power as a replacement for, or even as a compliment to, conventional power plants. Solar may have its' own specialty niche, but in no way does that rise to the level of an "alternative" to conventional power plants.
TABLE 8.1 (p. 159)
Projected Human Use of Energy Resources
Year.........Power(TeraWatts)
2000...........15
2025...........28
2050...........53
2075..........101
2100..........192
2125..........365
2150..........693
2175........1,320
2200........2,500
Humanity used 15 TeraWatts total in 2000; Zubrin goes back over the data available and assumes a 2.6 percent rate of growth. What this basically shows is an exponential rate of growth in 'Power Usage'.
First of all, the SP-150 does not sell anywhere NEAR $25 a watt in quantity... retail cost on that module is under $5 per watt.
The current average rate of U.S. energy consumption is about 3.3 trillion Watts. Based on the above efficiency data, we would need to cover the entire state of New Mexico with solar cells just to generate this amount of energy!
Why would we want to do that? Solar is mostly useful for distributed generation applications, not central power.
The initial capitalization cost of a solar PV generating plant is at least 10 times the cost of a large conventional plant. And that is exclusive of the mammoth land acquisition costs necessary to accommodate the vast expanse of solar cells.
Very large solar arrays (>1 MW) can be installed for under $6 per watt--much more than conventional power plants, but far less than your "ten times" number. And large solar arrays can be sited on remote, otherwise unused land, as long as it is sited fairly close to transmission lines.
PV cells have a limited lifetime. As a consequence, manufacturers offer only limited warranties on power output, some as short as 20 years.
Fine. Name me one other product that has a 20+year warranty. I've never once heard someone fault modules because they "only" have a 20-year warranty.
A violent storm, such as a hail storm, can decimate a solar power plant. A storm covering only one square mile (the size of a small 50 MW solar plant) could destroy a half billion dollars in solar panels.
Modules are glazed with tempered glass, and are much more durable than you suggest.
PV cells have a nasty little habit of loosing conversion efficiency when you put them out in the warm sunlight. A hot day can lower the output power by up to 20%!
This "nasty little habit" is otherwise known as temperature dependency, and is well known and accounted for in PV output estimation models. Next.
A solar PV generating plant is not without maintenance. How are you going to wash the tens of thousands of square miles of PV cells of the dirt, dust and bird droppings that will collect over time?
Ummm... you hose them down. Duh. Considering that that's the biggest routine maintenance item, it wouldn't even be a part-time job for one guy with a hose.
But other than those narrow exceptions, it makes no economic, engineering, ecological or practical sense to use solar power as a replacement for, or even as a compliment to, conventional power plants. Solar may have its' own specialty niche, but in no way does that rise to the level of an "alternative" to conventional power plants.
The recent efforts, particularly in California, New York and Florida, to accelerate the adoption of PV as a distributed generation technology has dramatically lowered the cost of PV systems and has driven new investment into the field. Technology is not standing still.
One point is very important to make: no one is, or at least should be, pushing solar as a replacement for central power. It's simply a clean, long-lasting, low-maintenance form of distributed generation (the only real one for most applications) that, as prices drop, becomes more and more attractive. That hardly amounts to the scandal or fraud that you're making it out to be.
Aren't those the same thing? Do you mean peak power output occurs...?
Yes.
Sorry, you are off by over a third. A solar power plant can be built for far less than that.
Also, lead-acid batteries are not the only option. Some systems use Edison (Iron-KOH) cells.
Me? I'm tied to the grid, no batteries.
Non-food grade oil is cheaper, used french FReedom fry oil has to be disposed of with associated disposal costs, or so I'm told...
This is not a true sine wave inverter. True sine wave inverters (often called synchronous inverters) are required for a utility grid tie in and run at far less efficiency than the unit you cite. Inverters running at the level of efficiency you referenced, are designed with switching power supplies that include heavy amounts of low pass filtering in order to simulate (but never actually achieve) a sine wave output. They are not capable of being tied to the utility grid, and either run as "stand alones" or tied only to a local power grid.
--Boot Hill
Like in DG applications, which is what solar is best at.
OH MY GOD!!! Some call PG&E and let them know!!! I've been tied to their grid for about 3 years!!!
The same roof collector surface that forces you to use air conditioning is what you propose to use to offset it?
An umbrella would be a cheaper alternative.
Where did I say it did?
kezekiel says: "Very large solar arrays (>1 MW) can be installed for under $6 per watt."
No they can't. Cite an example.
kezekiel says: "Name me one other product that has a 20+year warranty."
Irrelevant. The importance of the 20 year warranty is that the even the manufacturer recognizes the limited lifetime of PV cells.
kezekiel says: "Modules are glazed with tempered glass, and are much more durable than you suggest.."
Which adds cost, weight and higher losses through reflection and still without making them sturdy enough to survive a significant hail storm event.
kezekiel says: "This "nasty little habit" is otherwise known as temperature dependency, and is well known and accounted for in PV output estimation models."
It is not known as "temperature dependency", it is known as the coefficient of temperature (Tc). And it is not "accounted for in PV output" in any way that the average consumer can detect. Take for example the SP-150 model. It is rated as a 150 watt unit. But that does not account for the losses due to the temperature coefficient. It is only when looking at the foot notes to the data sheet that one discovers that because of Tc, this 150 watt unit barely manages to eke out 109 watts of power under real world conditions.
kezekiel says: "The recent efforts...to accelerate the adoption of PV as a distributed generation technology has dramatically lowered the cost of PV systems ."
No it hasn't. Provide examples.
kezekiel says: "[Solar power is]simply a clean, long-lasting, low-maintenance form of distributed generation ."
We have had distributed generation since the advent of electric utilities. It is called multiple conventional power plants. Name one concrete and realistic advantage to adding solar, wind, bio-mass, etc., to your concept of "distributed generation".
--Boot Hill
If Germany durring the war could convert coal to gasoline, then we should be able to do the same.
We have more coal in the ground that can be used for gasoline and power generation than 10 Saudi Arabias without the political and terrorist problems associated with that nation.
JUST SAY COAL!!!!!!!
You still haven't presented any evidence of that.
--Boot Hill
Would this be in the same way that you were getting 800 watts out of a 2m^2 solar array???
What are you trying to say? Are you saying you are tied to the public utility grid with an AEI GC-1000? When your PV array is making more power than you can use, is your excess (and only your excess) put out onto the utility power grid for other to use? When you use more power than the PV array can supply, does the utility makes up the difference (and only the difference)? If your answer is no to any of these then you need to re-think your last reply.
--Boot Hill
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.
![[+]](http://www.eia.doe.gov/emeu/aer/ep/images/figure1.jpg){kind=link}