Solar Thermal Electricity: Can it Replace Coal, Gas, and Oil?
One of the most common arguments against large-scale use of renewable energy is that it cannot produce a steady, reliable stream of energy, day and night. Ausra Inc. does not agree. They believe that solar thermal technology can supply over 90% of grid power, while reducing carbon emissions.
“The U.S. could nearly eliminate our dependence on coal, oil and gas for electricity and transportation, drastically slashing global warming pollution without increasing costs for energy,” said David Mills, chief scientific officer and founder of Ausra.
You may be wondering, how will we have electricity at night or during cloudy weather?
Will we use large banks of batteries or burn candles?
The ability to utilize solar thermal technology after the sun sets is made possible by a storage system that is up to 93% efficient, according to Ausra’s executive vice president John O’Donnell.
High efficiency is achieved because solar thermal plants do not need to convert energy to another form in order to store it and do not rely on battery technology. Flat moving recflectors or parabolic mirrors focus solar energy to generate heat. This heat generates steam that turns turbines, thus generating an electric current.
If you want to generate electricity-at, say, 3 am-heat from the sun can be stored for later use. This gives solar thermal technology the ability to not just produce peak power, but also generate base load electricity.
Peak Power: The First Wave of Solar Thermal Plants
The maximum amount of electricity demand on the power grid occurs during weekday afternoons and evenings in the summer months in most regions of the United States. This is largely caused by air conditioning loads, which gobble up electricity.
Because the electric grid needs to be able to handle these peak loads, capacity is built to specifically handle these loads. Natural gas and oil typically comes to the rescue to produce this electricity. Although these plants are expensive to operate, they are cheaper to construct than most of the alternatives. They are fast to start, producing power in 30 minutes or less. Additional power plants are constructed just to generate electricity for the times when it is needed most.
This causes peak electricity to be more expensive. A kilowatt hour of electricity at 3 pm and 3 am does not come with the same price tag to the utility company.
“Adding solar plants that reliably generate until 10 pm displaces the highest cost alternative power,” said John O’Donnell. “That is the first wave of solar thermal plants. The daily and seasonal variation in grid load in the United States matches solar availability.”
Base Load: Replacing Coal Power
Base load is the minimum amount of electricity demand placed on the power grid over a 24 hour period. Coal and nuclear plants commonly supply this energy. These plants can take hours or even days to heat up to operating temperatures and are run more continuously than peak power plants.
Due largely to the lower cost of fuel, these plants can produce electricity at a lower cost. If a carbon tax is implemented in the future, this will increase the cost of electricity generated from coal.
Generating electricity around the clock with solar thermal technology relies on storage systems that run turbines long after the sun sets. “Ausra has a very active energy storage R & D group and we will be prototyping a couple of systems this year here in the US,” said John O’Donnell.
Solar Energy Storage
This is not a new technology, having been used for plastic manufacturing and petroleum production for a long time. Solar thermal plants have a cost advantage compared to photovoltaic technology because energy can be stored as heat without being converted to another form or relying on batteries.
“My favorite example in comparing energy storage options is on your desktop,” said John O’Donnell. “If you have a laptop computer and a thermos of coffee on your desk, the battery in your laptop and the thermos store about the same amount of energy. One of them costs about $150 and the other one costs maybe $3 to $5. On the wholesale level, storing electric power is at least 100 times more expensive than storing heat.”
The future certainly looks bright for solar thermal technology as concern over climate change increases. Global demand for electricity is growing rapidly, requiring clean solutions.
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Photo: Ausra’s facility in New South Wales, Australia. Courtesy Ausra.
Great article! Solar Thermal electricity can play a big role in providing for our energy needs if we continue to develop it. But to reduce our dependence on foreign oil especially for our transportation needs we’re going to need to increase our capacity by magnitudes to utilize some type of replacement like fuel cell technology.
It’s great to see an enthusiastic discussion about how to improve our energy future. With the cost of gasoline predicted to reach $4.00/gallon by summer and other sources such as coal and natural gas following suit, more and more people are interested in learning about the promise of alternative energy options. Many government and industry leaders believe hydrogen is an important part of the energy mix to help reduce oil consumption and improve our environment. Later this week the NHA Annual Hydrogen Conference and Expo US, March 30 – April 3, is taking place in Sacramento, CA. Please visit hydrogenconference.org to learn more. If you live near or if you’re traveling to Sacramento, we invite you to join us and experience how hydrogen can have a positive impact on our lives. The latest hydrogen technologies from all over the world will be on display, and there will even be opportunities to drive hydrogen vehicles from several leading auto manufacturers – all this is free and open to the public on Monday, March 31 at the Sacramento Convention Center. Stay tuned for upcoming announcements from the Hydrogen Expo.
In addition, the Hydrogen Education Foundation has recently launched a website to help people better understand hydrogen as a fuel. Please visit http://www.h2andyou.org to improve your knowledge about hydrogen as an alternative fuel.
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Storing the heated element (water, etc) overnight would probably not be too big of a problem. Many of these solar and thermal generating plants use a product called pentane to drive their turbines. Pentane boils at around 86 degrees, so it doesn’t take much heat to flash it into steam to get the turbines running. The pentane is then recaptured. I used to haul this product and it could freak people out. Sometimes when I would have to overnight at a truck stop during the delivery trip, the pentane would begin to boil in the tanker. When it does this, it begins to swirl around inside the tank because it is seeking oxygen. When it does this, the whole truck starts doing the Watucci.
In answer to Dave’s question, it seems like part of the beauty of heat storage is that it can actually be stored without having to convert the energy to another form. 6 hours of storage can have an efficiency as high as 93%. Typically, converting energy to another form causes some energy to be lost. Also, because the idea is to have these systems in the desert, water is scarce.
The discussion above has allready been worked out and is about to be put into action. The Trident Energy Power Plant is about to began it’s construction phase.
This power plant was to be a 5,200mw plant with the ability to expand. As of this moment, we are preparing to build the worlds largest power plant using this technology as part of the operating structure.
If interested, go to tridentenergypower.com
Gordon
the company where I work is supplying materials to build the plants here in the U.S.
this is a very good technology, and the water is actually recirculated in the process so larger amounts of water are not needed beyond the initial supply.
all they are doing is focusing the sun on a pipe system that generates heat to turn existing turbines. the costs to build is much lower than convention power plants, massive storage batteries that use heavy metals and whose production pollutes the environment are not used as in photovoltaic systems. costs to erect this type of facility is less than conventional power plants… and the “fuel” is free.
this technology has a great deal of promise and uses conventional construction methods that don’t rely on exotic materials that make this type of technology cost prohibitive.
as far as testing the process…it is being used in Austrailia now. so it has been tested. it is just being scaled up to service larger power generation needs.
I would suggest that you check out their website http://www.ausra.com for more info.
tridentenergypower.com ??????
looks like just a concept, and your management team ? doesn’t appear to have much experience in the power generation field.
Have you built anything yet ????????????????
your website doesn’t have much real detail… looks more like an ambition rather than real technology..
I’m just saying….
why do people have a hard time realizing that although the production of these technologies take money, they are an investment. The coal plants didn’t miraculously appear for free either. A solar thermal plant, of which there are many in existence, is an easy to maintain, very cost effective way of producing energy.
Also did you seriously ask why they can’t apply steam to cars? Ummm they did. Unfortunately no one is really pursuing this in the main stream right now even though the technology today would allow for seamless operation of a steam powered car.
not mentioned in the article is how the heat is stored for later 3am usage? is it just stored in a giant thermos tank for later electricity steam generation? how much steam do you lose? Does scale mean higher efficiency? Can a homeowner just slap one together and generate electricty?
how much water is used? water reliance may become another issue.