September 25, 2007
Solar Power: Not the Brightest Idea
By Hiserodt, Ed
While it is true that the sun sends more energy to Earth than humans could ever need, the problems associated with harnessing this energy make solar power very impractical. With "free energy" shining down, it should be expected people would want to harness solar energy to replace polluting sources of electricity. Is this possible? Yes, but the question is not whether some source of energy could provide the amount of energy necessary to fuel our energy- driven economy, but whether or not it is a practical solution for providing electrical energy sufficient for industry. After all, even moonbeams have energy and, with a sufficiently large and efficient collection and generation system, energy could be harnessed from moonbeams. But it's not practical to do so, one reason being that the collection panels would have to be huge. The problem with solar generation is the same as for moonbeams, the difference being only in degree.Insolation
The energy of the sun shining down on a unit area of the Earth or its atmosphere is known as its insolation. At the outer limits of the atmosphere, insolation is at its maximum with 1,367 watts of energy striking each square meter (w/m^sup 2^). But insolation varies according to location on Earth, the time of day, the season, and weather conditions. On the equator, the maximum insolation on a cloudless day at noon is about 950 w/m^sup 2^. For power generation, however, the peak insolation is of little value. What matters primarily is the 24-hour average insolation at a particular location.
Physics Professor Emeritus Howard Hayden's very informative and well-documented book, The Solar Fraud, provides the following geographical information given here in both w/m^sup 2^, and the equivalent in kilowatts (1,000 watts, abbreviated kW) per acre that will be convenient for other comparisons.
This is the maximum solar energy available. It is relatively diffuse compared to what would be needed to make solar power practical (just not as diffuse as moonbeams!), and no amount of wishful thinking or new laws on the books is going to change it.
Sunlight In, Electricity Out
There are two methods of generating electricity from sunlight, one of which employs photovoltaic cells to convert light into direct- current electricity. On the micro-scale, photovoltaic cells power our calculators, which require only a few thousandths of a watt to operate. Orbiting spacecraft and remote monitoring stations have successfully used this technology for years with peaks of several hundred watts. The trouble occurs when very large amounts of power must be generated and available at all times.
Not all solar energy is converted to electricity in photovoltaic cells, and not from want of trying. The photovoltaic effect is produced by sunlight of a particular frequency (color) causing silicon - that has been "doped" with special impurities - to give up electrons. The part of the sunlight spectrum with a lower frequency doesn't have the energy to cause electrons to be ejected. Energy from higher frequency solar rathation is largely lost to heat after it has done its job of "kicking" an electron. The problem of maximizing power from sunlight has been known for at least 30 years, and is primarily one of physical limitations, not engineering technology.
In order to calculate the average output from a photovoltaic array, one would take the insolation per square meter or acre, allow for needed spacing, and multiply by the efficiency of the photovoltaic cell. Let's check what power could be generated in Albuquerque. Commercial photovoltaic cells turn about 10 percent of the sun's energy into electrical energy and, in order to keep the PV cells clean and to direct them toward the sun, 50 percent spacing is typical.
Doing the math, an acre of land with solar-cell arrays with 50- percent spacing in Albuquerque would theoretically produce an average of 48.5 kW. That is a good bit of power - enough for about 40 hand-held hair dryers, or eight to 10 kitchen ranges - but to get it requires an area four-fifths the size of a football field covered with expensive semi-conductors and miles of inter-wiring, not to mention inverters and transformers, to produce usable electricity. Because of its lower insolation, Hartford, Connecticut, would generate one-third less or 32.3 kW per acre. This is equivalent to 24 horsepower - not exactly what is needed to power homes, community services, and industrial needs.
Solar Thermal Generation
The second method of turning solar energy into electric power is solar thermal generation. The three most notable U.S. solar power electrical generation stations were sited in the Mojave Desert near Barstow, California. In each case solar energy was used to boil water, generating steam that drives a turbine, which in turn drives a generator - just as coal, natural gas, and nuclear plants do.
In the case of solar power, there is a problem: a pot of water put in the tropical sun at noon won't boil. And since the efficiency of a turbine generator is proportional to the difference between the ambient temperature and the temperature of the steam, water that's just boiling wouldn't be enough. A paltry 212[degrees]F wouldn't even get the turbine moving. For reasonable efficiencies the temperature should be raised in the boiler to about 600[degrees]F. In this process, water is not directly heated during solar thermal power generation. Instead, an oil with special heat-transfer characteristics (therminol) is heated far above the boiling point of water and circulated through a heat exchanger.
The first of the solar plants in the Mojave Desert, Solar 1, was destroyed by a therminol fire. Its very similar successor, Solar 2, used thousands of computer-controlled mirrors to focus sunlight on a boiler on top of a tower. The plant occupied 130 acres and could produce 10,000 kW of electricity at peak power, although it only averaged 16 percent of this output. Doing a little math shows 1,600 kW from a land investment of 130 acres, or about 12.3 kW per acre, about a quarter of the theoretical photovoltaic installation previously discussed.
Even SEGS, the largest operating solar plant in the world - also located in the Mojave Desert (fancy that) - which uses nine solar arrays with over 1,000,000 sun-tracking parabolic mirrors to concentrate solar energy, is not a wonder of efficiency. As advertised, the facility sounds great. It is rated at 354,000 kW of electrical output, roughly one-third the output of a major nuclear power plant. But its real average power is 77,000 kW - which means that the plant, which takes up a 1 ,600-acre site - generates 48 kW per acre and requires a natural gas boiler that contributes about 25 percent to its output.
As is typical of green propaganda, it is claimed that SEGS generates enough power to "meet the needs of about 500,000 people." Most company executives would go to jail for such untruths in advertising. For a year, the total kWh of SEGS would be 77,000 kW times 24 hours, times 365 days, or 674 million kWh. According to the California Energy Commission, the average U.S. per capita energy consumption is 1 1,997 kWh per year, so for 500,000 people their electrical usage would be 6 billion kWh. How does the U.S. Office of Solar Technologies, which propagates this figure, arrive at 500,000? It appears they use California's low per capita energy consumption rate andan insolation of 950 watts per square meter (the maximum insolation possible on Earth), 24 hours per day. Our government watchdogs, who count sheets of toilet paper to keep manufacturers honest, turn a blind eye to such green exaggerations.
This same trickery has just happened again. Pacific Gas and Electric proudly announced an August 1 agreement to "buy 553 Megawatts of Solar Power," which is a totally ridiculous statement, equivalent to a motorist at a gas station quipping, "I just purchased 27 miles per gallon." Again, watts are a rate of energy production, so 553 megawatts represents the production of energy at some given time - in this case it would represent the production of energy in the Mojave, provided that the desert was moved to the equator and the sun stopped directly over it. The statement bragged that the megawatts purchased would meet the annual needs of 400,000 homes. Using 3.15 persons per home, this would amount to energy for 1,260,000 individuals. At even the low California per capita usage and the totally deceptive figure of 950 watts per square meter, the 400,000-homes figure is exaggerated by almost a factor of two. This should get someone 10 to 20, but won't. Most reporters don't do math, and green power is sacrosanct.
The movement toward "renewables" has been given a fearful advance by the U.S. House of Representatives, which voted in early August to require electric utilities to provide between 11 and 15 percent of their generating capacity from "renewables" - which would supposedly be achieved primarily through wind and solar power. For a medium- sized state, such as my home state of Arkansas, providing 11 percent of electrical generation via solar power would mean green generation by 2020 of about seven billion kWh of electricity. To meet this with solar generation, Arkansas would need 10-15 solar plants, each with the capacity of SEGS occupying 16,000 to 24,000 acres - 25 to 27 square miles. The cost? Who knows? Construction costs of green power facilities are carefully concealed in a twisted maze of grants, subsidies, credits, and other ways to disguise their outlandish costs. (Wind power is also not a good energy alternative. See "Blown Away" in our Sept. 3 issue.) Politicians and their green constituencies continually invoke the mantra of "wind and solar power" as the solution to our energy future. It is time to stop nodding our heads at this lunacy, take off the gloves, and ask them illuminating questions:
* How many wind turbines do you suggest, where do you plan to site them, what is the kW per wind turbine, and what are the anticipated capacity factors?
* What subsidies will the taxpayers be required to pay for green power, and how will this affect the utility ratepayers and stockholders?
* What type of solar power are you referring to? If photovoltaic, what efficiencies do you project? If thermal, how is this to be configured? In either case, on what average insolation are your calculations based?
* How do you propose to replace existing power plants when statistically there will be extended periods when both wind and solar power will not supply any energy to the power grid?
* How can you say that wind and solar power can significantly reduce carbon dioxide emissions when utilities must maintain on- line, fuel-burning "spinning reserves" to be instantly ready to produce power when wind or solar sources suddenly stop?
It is doubtful you will get answers. Most of those promoting green energy don't know a kilowatt from a kumquat.
The movement toward "renewables" has been given a fearful advance by the U.S. House of Representatives, which voted in early August to require electric utilities to provide between 11 and 15 percent of their generating capacity from "renewables."
Third World countries need serious electrification projects if they are to escape the misery common in primitive societies. Green power wastes resources on intermittent, puny solar generation arrays incapable of powering even high-school computers - much less air conditioning, water pumps, sewage treatment plants, or lighting.
Solar 1 (pictured) was rebuilt as Solar 2 with a second ring of 108 1,000-square-foot mirrors producing 10 MW of peak power at maximum sunlight. Its average output before being decommissioned in 1999 was approximately 12 kW per acre. In comparison a nuclear power plant typically produces 3,600 kW per acre - without resting at night.
Ed Hiserodt is the author of Under-Exposed: What If Rathation Is Really Good for You?
Copyright The New American Sep 17, 2007