Gathering and using the energy from the sun must be a critical part of our future. As your article mentioned, solar power generation peaks at exactly the time when electric load peaks. In fact, it's the same cause: the sun. Load peaks because the sun heats our houses and businesses, pushing up electric cooling loads. Unlike the wind, which blows when electric load is low, solar power doesn't need to be stored. It can be used as peaking generation like a combustion turbine in many ways, although solar power is not very dispatchable.


Efficiencies and reliability may be low and cost high, but every technology common today had those maladies at one time. With continued investment, solar power will mature to a critical part of our energy supply.


William Quaintance


I applaud and support efforts by utilities and government agencies to support the development and growth of renewable energy sources such as solar. We need that type of energy in our mix.


Your article states that the upfront capital cost of the proposed Arizona 250MW solar concentrator project starting up in 2008 is $250 million. It is highly unlikely that this project can be built for this price tag, in my view. Fossil fuel energy projects today cost approximately $2 million per megawatt of power put in place. Construction costs are escalating due to inflationary pressure on labor costs and higher costs for materials due to strong demand oversees. Power project costs have doubled in the past five years. Solar projects are less economical and likely to be even higher than fossil fuel project capital costs.


Jim Greer


I believe a nuclear plant producing four times the energy of the proposed solar facility can produce electricity at under 10 cents per kwH without subsidies. It will also occupy maybe as much as 1/10 the land area of the proposed solar facility.


I am glad to learn that someone is again working on methods for storing solar heat, a process that was well studied and documented in the 1980s when I worked at the Solar Energy Research Institute (now NREL.) If there have been major breakthroughs in new storage methods, they certainly have not been publicized. The Barstow solar concentrating solar plant was to serve as a test bed for the dispersed reflector and it did so admirably. I presume that the designers of the new facility will build on that technology. Or, as often is the case, will they spend more money to re-invent the wheel?


Here are some concerns about dispersed reflectors that are never addressed or ignored.


Laws of physics. If a facility is to store energy to run for 20 hours without the sun, then it must have a reflector field large enough to both generate electricity and fill the storage. Exact calculations can be done, but here's a rough estimate:


If the plant is to produce 250 mW electrical, assuming 25% conversion from heat to electricity (very high for 1. sun to thermal, 2. transfer medium to steam, 3. steam to mechanical, 4. mechanical to electricity - four conversions) it will need to collect 1,000 mW thermal. At peak sunlight, a collector receives about 1 kW per square meter. The facility will need 1,000,000 square meters of collector (.386 square miles, or 247 acres.) That is for immediate electrical production. Suppose the facility has full sunlight for 10 hours per day. If it is to store, during that 10 hours, enough energy to operate for 20 hours without sunlight, then it must store twice as much energy as it uses, (assuming that there are no storage losses) making a total collector field equal to three times the electrical output. (One times the field for sunlight operation and two times the field for storage.) Thus the total collector area must be 3 million square meters or 741 acres, twice the figure in your ar ticle. However, this is just the collector area, not taking into account the facility buildings and the area required for the storage facility.


Environmental impact. While it may be argued that the solar facility is non-polluting and it certainly emits no direct "greenhouse" gases, there are a number of real impacts.


Bird deaths. I believe the Barstow facility has documented data, and maybe even pictures, of birds being fried/vaporized by flying into the concentrated beams.
Endangered plants. What happens to the plant life below the reflectors as its source of sunlight is cut off?
Endangered animals. What happens to the animals who lived in the desert and depended on the heat provided by the sun to keep them alive?

Survivability. Sand storms. It takes only one really good sandstorm to destroy the reflectors. Ask anyone who has had a car windshield rendered opaque by blowing sand.


Distribution. Attempts to run new power lines to distribute exiting power are opposed by almost every "environmental" group. Why do you think that power distribution from a solar facility will be treated any differently?


Real costs. The article mentions several times that tax breaks, financial incentives, regulations, etc. are necessary for solar energy to be successful. Translated, this means that we will all pay extra to subsidize the development of an energy source that is uneconomical and could never survive in the free market.


There may be a reason why solar energy as baseline power has not made any real impact on the energy supply mix. Could it be that baseline use of intermittent energy sources is not a very good idea? I suggest we spend our money supporting solar cells, which make a great deal of sense in specific applications (not baseline energy,) solar thermal which makes a great deal of sense in individual facility heating and cooling (not baseline energy,) and clean and safe nuclear energy, which has a long track record of producing cost-completive baseline energy.


Michael Z. Lowenstein, Ph.D.
Chief Technology Officer
Harmonics Limited
 

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