TEN FAQS ABOUT SOLAR THERMAL POWER
1. What is the difference between the terms “solar thermal power," “concentrating solar power,” and “CSP”?
thermal power is sometimes called concentrating solar power or
CSP. These labels refer to technologies that use the energy of
the sun to produce steam, directly or indirectly. The steam is
then piped to a convention power generation system to make
electricity. The difference between a solar thermal plant and a
conventional fossil-fueled power plant is that conventional plants
create steam by burning fuels that release carbon into the atmosphere.
2. What is the difference between solar thermal power plants and photovoltaic (also known as PV) systems?
thermal power plants, often also called Concentrating Solar Power (CSP)
plants, use sunlight to produce steam, which is then used to generate
electricity. By contrast, photovoltaic (also known as PV) systems
use special panels to collect sunlight and convert it directly to
electricity. “Thermal” refers to the fact that it is the heat of
the sunlight that is used, and “concentrating” refers to the fact that
solar thermal systems concentrate the sunlight, in much the same way
that a magnifying glass does, to harness its heat.
plants are large utility-scale projects that generate enough power to
serve tens of thousands of homes. Their power is usually sold to
public utilities, which then sell it to their customers.
Photovoltaic systems are usually much smaller and are usually installed
on residences, schools, or office buildings.
3. Where can solar thermal plants be built?
theory, a solar thermal plant can be built anywhere that the sun
shines, however cost considerations dictate that they be built in areas
of high solar radiation – a measure of how much power can be generated
in a single square meter of surface area in a typical year. The
best solar radiation is found in high desert areas, such as the Mojave
Desert in Southern California, where the sun shines reliably 330 to 350
days a year. Another major consideration is that solar plants
need to be built in the vicinity of power transmission lines serving
markets large enough to use all of the power generated by the plant.
4. How much land do solar thermal plants require?
answer depends on two factors: a) the solar insularity (see FAQ
3) of the plant location, and b) the specific technology being
used. In general, a typical 100 MW solar thermal plant will
occupy 600 to 800 acres. Installing solar power plants on an area
covering only 1% of the Mojave Desert would provide enough solar power
to serve 75% of the homes in California.
5. How much are atmospheric carbon emissions reduced by solar thermal power plants?
emissions are reduced by 600 pounds for each MW hour of solar power
that displaces an equal amount of fossil-fuel power. Installing
solar power plants on an area covering 1% of the Mojave Desert would
reduce annual carbon emissions by over 20 million tons.
6. Is solar thermal power reliable and available when needed most - during peak demand hours?
peak demand period for electricity is the hottest part of the day, when
air conditioners are running in offices and homes. This is the
same time of day when solar power is produced. In addition,
because sunshine is reliable and consistent in the desert areas where
solar power plants are typically built solar power is also consistent
and reliable. Conversely, another common form of renewable power
production, wind power, normally has its peak production period during
the nighttime hours, and is much less predictable and reliable.
7. Are there ways to use solar power to provide electricity power both day and night?
the photovoltaic systems typically installed on rooftops, CSP plants
produce their electricity by first producing steam then using that
steam to generate electricity. Thus, CSP plants can be fitted
with gas-fired boilers to produce steam when the sun is not shining,
enabling the plants to produce electricity at any time. This
provides valuable back-up generation capacity to utility companies for
use when wind power is not available, or demand is unusually high.
Another method is to install thermal storage to store heat during the
daylight hours and release that heat during the night to make
electricity. At this time, such storage systems are not
economical, but it is anticipated that the cost will come down and make
the use of solar power viable around-the-clock.
8. Will the cost of electricity produced by CSP plants vary in the future?
cost of fuel represents about 60% of the cost of producing electricity
from fossil-fueled plants. CSP plants require no fuel, thus the
cost of the power they produce is not affected by the vagaries and
risks associated with fossil fuel prices. Other than very slight
increases in maintenance and operating expenses due to inflation, the
cost of power produced by a CSP plant will not change over its economic
9. How does the cost of electricity produced by CSP plants compare to the cost of electricity produced by fossil fuel plants?
thermal power is probably cheaper than power from fossil fuels when all
cost externalities are considered. While many of the costs of
fossil fuels are well known, others (pollution related health problems,
environmental degradation, the impact on national security from relying
on foreign energy sources) are indirect and difficult to calculate.
These are traditionally external to the pricing system, and are thus
often referred to as externalities. In order to better control this
matter, legislative and regulatory bodies are moving to require the
sequestration of carbon to keep it out of the atmosphere, or apply a
corrective pricing mechanism, such as a carbon tax, to fossil-fueled
power plants. Either measure will lead to the cost of solar
thermal power becoming cheaper to the consumer than fossil fuel based
Even without pricing cost
externalities, the cost of solar thermal power is going down. As
more plants are built and technologies improve, this price should
continuously drop over the next ten years with the result that the
price of solar power seems likely to be in the same range as power from
fossil fueled plants, even without carbon emissions costs considered.
10. How does today’s regulatory environment impact the development of solar energy plants?
combination of environmental concerns and persistently higher prices
for commodity fuels has caused a number of states to adopt Renewable
Portfolio Standards (RPS) that require their utilities to purchase as
much as 33% of their power from renewable energy sources such as wind,
hydro and solar by specified dates. These and other regulatory
mandates including federal mandates and tax incentives provide an
environment conducive to the development of alternative energy
solutions and make the building of solar power plants cost effective.
A favorable governmental and regulatory climate makes the delivery of
renewable energies possible. And, these requirements, such as the
RPS in place for California that requires utilities to purchase 20% of
its power from renewable sources by 2011 and 33% by 2017, help to
encourage utilities to make the development of alternative energy
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