As technology improves, here comes the sun
By Amiram Cohen
The prices of solar energy are likely to plummet, and to approach those of conventional energy. In other words, the price of electricity produced by solar-powered stations is likely to drop to that of electricity produced in power stations fueled by coal, crude oil or gas, according to the estimates of the Giza Financial Consulting firm, in a survey published recently.
At present, the price of electricity produced from solar energy is about 10 cents per kilowatt/hour, twice the price of electricity produced from conventional energy. However, the production of electricity from solar energy, as opposed to conventional energy, does not cause air or water pollution; it is completely clean energy ("green energy"). Therefore, solar energy has public advantages - its use does not require public expenditures stemming from damage to the health of the population.
In addition, there is no loss to the economy caused by damages to agriculture and to construction, from air and water pollution. Therefore, claims Giza, the price gap between the production of electricity from conventional energy and production from solar energy has already narrowed. This, despite the fact that we cannot quantify the price difference precisely, due to the difficulty in calculating the public advantages.
Giza vice president Yuval Zilberstein and analyst Sigal Yissachar, who conducted the survey, claim that the remaining price gap must be narrowed even further - by means of government encouragement to increase the demand for solar energy. Such demand will bring about the allocation of public and private resources to research and development in the field of solar energy, and the achievement of technological improvements that will lower its prices.
The condition for equalizing the costs of the two methods of power production, say Zilberstein and Yissachar, is to create a critical mass of demand for solar energy, by means of government subsidies. Subsidies will be the catalyst for increasing demand. They say that subsidies are justified even in a competitive economy, in which the government should not intervene: "Subsidies for the use of electricity from solar energy will be returned by savings in public expenditures (external advantages)."
The survey points to water desalination as a model that should be valid in the field of solar energy as well. According to Zilberstein and Yissachar, the critical mass of worldwide demand for building desalination plants created a lever for achieving technological improvements, especially the development of efficient membranes that cost relatively little. In this way, the cost of desalination decreased within a decade from one dollar per cubic meter to 50 cents.
The Israeli company Luz, now Solel, was the first in the world to build solar energy stations for commercial production of electricity from solar energy. In all, the company set up nine solar stations in the Mojave Desert in California in 1984, with an overall capacity of 350 megawatts. The capacity of each one of the two largest stations is 80 megawatts. Power stations were built by private investors with the support of the U.S. government, and are owned by California's two large energy companies. Although the technology has already become outdated, the stations supply energy to the state of California. That is the only commercial implementation thus far for the production of electricity from solar energy.
Generally, there is a distinction made between two main technologies for the use of solar energy for producing electricity. One is based on photoelectric cells that convert sunlight into an electric current. This technology uses these cells, which are also known as photovoltaic cells, to supply electricity to small plants in remote regions, where there is no economic justification for supplying energy from distant power stations - these include electricity for communications systems, and for home water heaters. However, this technology is expensive, and therefore its use is limited to remote places.
The second technology is based on a solar-thermal system, and is used for building high-capacity solar energy stations. Recently, the Ministry of National Infrastructure approved the Israel Electric Corporation's solar-thermal installation in the Negev, with a capacity of 100 megawatts, with the intention of expanding it in the future to 500 megawatts.
In this technology, the rays of the sun are concentrated by means of "solar fields" - systems of sun absorbers that work like absorbers in solar heaters. The energy created by concentrating the sun's rays in solar fields heats water or oil, and produces steam that operates a generator for creating electricity.
A solar-thermal power station usually includes a conventional production unit, such as a turbine operated by natural gas. This allows the power station to operate even in cloudy conditions and at night.
Some additional advantages of solar power stations are:
l The power station can be located where the electricity will be used, without need for transport and distribution systems. This advantage is relevant for remote places with no transport infrastructure.
l Production capability can be adapted precisely to the amount required for consumption, and thus minimizes the waste of production capability.
l High reliability and relatively low costs of maintenance and operation.
Nevertheless, solar power stations have limitations, which must be considered during planning:
l Without government or international subsidies, the cost of energy from solar energy stations is still higher than that from conventional power stations. After the subsidies a price gap remains, but it should narrow in the foreseeable future.
l The efficiency of a solar energy plant is directly dependent on climatic conditions and location. Solar technology is most efficient in latitudes 0-40, and in extreme desert conditions, where there are long periods of strong and direct radiation.
l Solar energy stations require a relatively large area. However, the climatic limitations that require that they be built in desert regions, greatly minimize this shortcoming.
l A sufficiently efficient and reliable system for storing solar energy accumulated during the hours of sunshine has yet to be developed. |
