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Concentrating On The Important Things - Solar Thermal Power
Posted by Big Gav on April 2, 2008 - 6:00pm in The Oil Drum: Australia/New Zealand
Topic: Alternative energy
Tags: concentrating solar power, solar hot water, solar power, solar thermal power [list all tags]
While we spend a lot of time talking about traditional energy sources based on depleting resources that are extracted from the ground, I think its important to remember that the fastest growing sources of energy are solar and wind, and that these will never run out. As M King Hubbert put it regarding solar power in particular :
The biggest source of energy on this earth, now or ever, is solar. I used to think it was so diffuse as to be impractical. But I’ve changed my mind. It’s not impractical…This technology exists right now. So if we just convert the technology and research and facilities of the oil and gas industries, the chemical industry and the electrical power industry—we could do it tomorrow. All we’ve got to do is throw our weight into it.
Both Stuart Staniford's recent "Powering Civilization to 2050" post and (to a lesser extent) Scientific American's "Solar Grand Plan" concentrated on using photovoltaic solar cells to provide the bulk of our energy needs. While both thin film and traditional silicon based PV cells seem to set new efficiency records every couple of months (a CIGS cell recently reached 19.9% efficiency in lab tests, and multi-crystalline silicon PV cells recently reached 19.5% efficiency), the most promising mechanism for large scale solar power generation seems to be solar thermal power (often referred to as concentrating solar power, or CSP).
While this subject has been covered previously at TOD (from a slightly UK-centric viewpoint), I thought it was worth revisiting as solar thermal power has received a lot of press attention lately, as experience with generating power in this way grows and the potential becomes clearer to a larger number of parties.
History
Concentrated sunlight has been used to perform useful tasks for many centuries. A legend claims Archimedes used polished shields to concentrate sunlight on a Roman fleet to repel them from Syracuse in 212 BC. Leonardo Da Vinci considered using large scale solar concentrators to weld copper in the 15th century. Auguste Mouchout successfully powered a steam engine with sunlight in 1866 - the first known example of a concentrating solar-powered mechanical device.
Concentrating Solar Power (CSP) systems use lenses or mirrors combined with tracking systems to focus sunlight which is then used to generate electricity. The primary mechanisms for concentrating sunlight are the parabolic trough, the solar power tower (not to be confused with solar updraft towers) and the parabolic dish. The high temperatures produced by CSP systems can also be used to provide heat and steam for a variety of applications (cogeneration). CSP technologies require direct sunlight (insolation) to function and are of limited use in locations with significant cloud cover.
Solar thermal power plants have been in commercial use in southern California since 1985. An area of desert around 250 km by 250 km covered with CSP power generation could supply all the world's current electricity demand.
Solar thermal plants can be built in their entirety within a few years - much faster than many conventional power projects. Solar thermal plants are built almost entirely with modular, commodity materials (and thus have short development and construction times) and do not encounter the sort of opposition on environmental grounds that traditional forms of power generation like coal and nuclear face.
Operational plants include :
* US (California) - 354 MW FPL's Solar Energy Generating Systems (SEGS) plant, using parabolic troughs
* US (Arizona) - 1 MW Acciona Energy's Saguaro Solar Generating Station using parabolic troughs
* Spain (Seville) - 11 MW Abengoa's PS10 solar tower
* Australia (NSW) - 35 MW Liddell Power Station using fresnel reflectors
* US (Nevada) - 64 MW Acciona Energy's Nevada Solar One plant (not to be confused with the Solar One / Solar Two experimental plants) using parabolic troughs
Plants currently under construction :
* Spain (Seville) - 20 MW Abengoa's PS20 solar tower
* Spain (Seville) - 20 MW (each) Abengoa's PS20 and AZ20 solar towers
* Spain (Seville) - 50 MW (each) Abengoa's Solnova 1 and 3 using parabolic troughs (5 plants planned in all)
* Spain (Andalusia) - 17 MW Sener's Solar Tres solar tower (molten salt energy storage)
* Spain (Andalusia) - 50 MW (each) Sener's Andasol I, II and III plants (molten salt energy storage)
Solar Thermal Heating Up
There has been a spate of new announcements regarding solar thermal power over the past year - there are over 5,800 MW of solar thermal plants in the planning stages worldwide.
The company receiving the most attention seems to be Ausra, a company set up by Dr David Mills (who pioneered the CSP plant at the Liddell power plant in New South Wales using compact linear Fresnel-reflector technology) with backing from Vinod Khosla and Kleiner, Perkins, Caulfield & Byers (see here for a brief demo of how their technology works). Mills estimates that solar thermal plants could provide more than 90 percent of current U.S. power demand at prices competitive with coal and natural gas. "There's almost no limit to how much you can put into the grid," he says.
Mills presented a paper (pdf) at the IEA SolarPACES conference in Las Vegas recently which revealed some interesting statistics about the construction cost of solar-thermal technologies: US$3,000 per kW of capacity, estimating this will drop to US$1,500 per kW over the next "several" years. The New York Times last year quoted GE Energy executives estimating coal plant construction between US$2,000 and US$3,000 per kW. Ausra says it can generate electricity for 10 cents per kWh (close to the current cost using natural gas), and it expects the price to drop even further.
According to Technology Review:
What distinguishes Ausra's design is its relative simplicity. In conventional solar-thermal plants such as Solel's, a long trough of parabolic mirrors focuses sunlight on a tube filled with a heat-transfer fluid, often some sort of oil or brine. The fluid, in turn, produces steam to drive a turbine and produce electricity. Ausra's solar collectors employ mass-produced and thus cheaper flat mirrors, and they focus light onto tubes filled with water, thus directly producing steam. Ausra's collectors produce less power, but that power costs less to produce.
Ausra is initially planning a 177 MW plant in California, and has committed to supply 1,500 MW of power to Californian utilities PG&E and FPL. They are also rumoured to be moving in to Texas as well.
PG&E have also signed a 25-year deal with Ausra competitor Solel Solar Systems of Israel to buy power from a 553 MW solar thermal plant that Solel is developing in California's Mojave Desert. FPL has also hired Solel to upgrade the SEGS solar-thermal plants it operates in the Mojave.
Another PG&E contract is with BrightSource to supply between 500 MW and 900 MW of power per year from solar tower plants in California, beginning in 2011, with the first of a number of 100 MW facilities being built in Ivanpah.
Other companies active in the US include eSolar (linked to Google's energy initiatives), RocketDyne and SkyFuel.
Abu Dhabi's Masdar Initiative and Spain's Sener are have formed a joint venture to build and operate concentrating solar power plants across the world's sunbelt regions called Torresol Energy.
Independently of Torresol, Masdar is developing its 100 MW "Shams 1" CSP plant in Abu Dhabi.
Algeria and Germany have signed a a joint research agreement for the development of a new generation of large-scale, low-cost solar thermal power plants (which could contribute to the Desert-TREC vision of large scale CSP in North Africa powering Europe, which I once dubbed "Deserts Of Gold").
More new plants are being planned in :
* Algeria - 20 MW Abengoa's plant in Hassi-R'Mel
* Australia - 10 MW Queensland State Government facility in Cloncurry
* Australia - 154 MW Solar Systems and TRUEnergy's plant in Mildura
* Egypt - 70 MW plant in Kuraymat
* Iran - 17 MW plant in Yazd
* Israel - 250 MW plant in Ashalim
* Morocco - 20 MW Abengoa's plant in Ain-Ben-Mathar
* US (Arizona) - 280 MW Abengoa and Arizona Public Service's plant in Gila Bend
* US (California) - 50 MW Inland Energy's plant in Victorville
* US (California) - 250 MW FPL Energy's Beacon Solar Energy Project
Feasibility studies are also being done in Oman, China and Mexico.
Most of the plants in the middle east are combined gas / solar thermal plants, with the numbers above representing the solar component only.
Energy Storage
One of the key differentiating factors between solar thermal power and solar PV is that heat energy is more easily (and efficiently) stored than electricity, with solar thermal plants often combining energy storage into the design to enable around-the-clock, dispatchable electricity generation.
Most solar thermal plants are looking to use molten salt for storing energy - other alternatives being developed are graphite (in the Cloncurry development), heated water / steam (for the Ausra plants) and heat-transfer oil such as therminol (for the Abengoa plant in Arizona).
Cost
The existing plants prove that concentrated solar power is practical, but costs must decrease. Electricity from solar thermal plants currently costs between US$0.13 per kilowatt hour (kWh) and US$0.17 per kWh, depending on the location of the plant and the amount of sunshine it receives. Conventional power plants generate electricity for between US$0.05 and US$0.15 per kilowatt hour (not including any carbon taxes or cap and trade related costs) but in most places it's below US$0.10 (wind power generally costs around US$0.08 per kWh).
An economic analysis released last month by Severin Borenstein (pdf), director of the University of California's Energy Institute, notes that solar thermal power will become cost competitive with other forms of power generation decades before photovoltaics will, even if greenhouse-gas emissions are not taxed aggressively.
In 2006 a report by the Solar Task Force (pdf) of the Western Governors’ Association concluded that CSP could provide electricity at US$0.10 per kWh or less by 2015 if 4 GW of plants were constructed.
According to Bernhard Milow from the German Aerospace Center (DLR) electricity from solar thermal plants could cost as little as €0.04 per kWh [US $0.06/kWh] by 2020, with well sited plants potentially generating power at lower prices than coal.
The US DOE began supporting large scale CSP last year, aiming to reduce the cost of CSP power to 7-10¢/kWh by 2015 and 5-7¢/kWh by 2020. The DOE estimated that reaching these cost targets could lead to installation of up to 35,000 MW of new generating capacity by 2030 in the US. James Fraser at The Energy Blog commented at the time that it was 5 years too late (given recent commercial activity in the area) and that PV solar may beat these price goals before solar thermal does, but that more solar options are good in any case, as both PV and thin film solar manufacturing will be constrained by availability for materials for some time as production continues to accelerate.
Another estimate from Sandia labs showed solar thermal costs (for solar towers) could fall to around 4 cents per kWh by 2030.
Stirling Engines
Another variant on the solar thermal power theme are Stirling engine based power plants, which generate electricity directly rather than first storing the energy as heat.
Stirling Energy Systems seems to be the leader in this field, with some reports talking about agreements with Southern California Edison and San Diego Gas & Electric for up to 1.75 GW of power. The company recently set a new world record of 31.25% for Solar-to-Grid conversion efficiency.
Other companies pursuing stirling engine based solutions are Infinia and SunPower (not to be confused with its larger namesake in the PV industry).
Passive Solar Thermal - Solar Hot Water And Others
Generating power isn't the only way to utilise solar thermal energy of course - solar hot water is a very cheap and efficient way of replacing gas or electricity usage with solar energy. Solar hot water systems are in widespread use in Australia, with state and federal governments encouraging people to upgrade their home hot water systems to solar - almost cost free in some states. The New Zealand government is also encouraging the use of solar hot water systems.
Some larger scale uses of solar thermal hot water are being put in place by Abengoa in Texas and Colorado.
Solar hot water is in wide use in China as well, with the city of Rizhao becoming somewhat famous for achieving widespread takeup of the units.
An unusual variation of the direct capture of solar energy in the form of heat is from a Dutch company that has developed a "Road Energy System" that siphons heat from roads and parking lots to heat offices and homes.
And one final use of solar thermal power - it can keep your house warm, if your windows face the right way, and even better, have insulating glass that doesn't let the heat out again - which could help make your building energy positive.
Cross-posted from Peak Energy
Personally I think thin film solar in conjunction with car or house based batteries will go closer to solving the baseload problem. That's if the price can come way down. The levels of storage envisioned for CSP plants seem to be generally less than 24 hours. Maybe that needs to be extended several times.
Also I'd take the 'comparable to gas fired' price suggestions with a pinch of salt. The gas generator can be switched on or off at random (if it has fuel) and the electrical connection usually already exists, not way out in the desert. It appears CSP promoters cite marginal costs, not average costs of a system that includes backup.
Sidenote: during Adelaide's heatwave some rellies went to Yorke Peninsula to catch the sea air. It too was like an oven despite being in effect way offshore. They sent a phone photo of the wind farm not stirring, the same time that every AC in Adelaide was switched on. CSP would have helped more.
California gets power from out of state alot so these might to closer to electrical connections than thought.
Boof - many of the plants mentioned were either combined CSP / gas generation, or had energy storage included (in the case of Ausra in particular).
The desert sites used for these plants get a couple of days a year of cloud cover - they aren't exactly likely to be out of action often. Why do you think 16 hours of storage is insufficient ?
Including storage also means you don't have the on/off problem to deal with.
If you combine a week of cloud cover (a common occurrence) with a natural gas shortage (an increasingly likely occurrence) your power station will be offline for 90% of that week.
A week of cloud cover in the locations that are best suited for solar thermal is unheard of - what are you talking about ?
These things are built in deserts that get (maybe) a few days of cloud cover in a year.
Look at a global solar insolation map - find the best bits. Match against rainfall records.
You'll find vast areas in the south-west US, north africa, middle east, western china, kalahari desert, northern chile and central australia that have great sun and hardly any rain.
Of course, cloud cover isn't the only cause of reduced insolation in desert-like environments:
http://www.mapsofworld.com/referrals/weather/severe-weather-conditions/s...
Good point (and very effectively made).
I was thinking of our local deserts here, which you don't see sandstorms in very often (not sandy enough) - but my one trip into the Sahara ran into one of these things and they are pretty awesome.
Does the Mojave get these things or is it more rocky than sand ?
My sand filled, 6 year old eyes testify to the Mojave having sand storms. Ah, memories...
Two miles, I tell ya! TWO miles!
Cheers
I don't mean to rain on your parade, but a check of the number of clear days for major cities across the US SW returns a lot of cloudy and partly cloudy days. 16 hours of storage only takes you through the night. If the next day is cloudy, your power station isn't generating. You need more storage than that. The following SW US cities have these numbers of clear, partly cloudy, and fully cloudy days, on average. They are in the area which has the highest potential for solar production in the US, according to http://www.energyatlas.org/.
Tucson is clear 53% of the time.
Tucson AZ, clear days: 193, partly cloudy: 91, cloudy: 81
http://www.cityrating.com/cityweather.asp?city=Tucson
Phoenix is clear 58% of the time.
Phoenix AZ, clear days: 211, partly cloudy: 85, cloudy: 70
http://www.cityrating.com/cityweather.asp?city=Phoenix
Flagstaff is clear 44% of the time.
Flagstaff, AZ, clear days: 162, partly cloudy: 102, cloudy: 102
http://www.cityrating.com/cityweather.asp?city=Flagstaff
Albuquerque is clear 46% of the time.
Albuquerque, NM, clear days: 167, partly cloudy: 111, cloudy: 87
http://www.cityrating.com/cityweather.asp?city=Albuquerque
Roswell is also clear 46% of the time.
Roswell, NM, clear days: 168, partly cloudy: 113, cloudy: 84
http://www.cityrating.com/cityweather.asp?city=Roswell
Las Vegas is clear 58% of the time.
Las Vegas, NV, clear days: 210, partly cloudy: 82, cloudy: 73
http://www.cityrating.com/cityweather.asp?city=Las+Vegas
As you can see, it's a lot more than "a few days."
Nice line about raining on my parade - you've brightened up my evening.
However - you seem to be conflating partly cloudy and cloudy with "no sun", which is more than a bit of stretch.
It's still possible to have 12 hours of sunlight on a "partly cloudy" day.
If you look at some of the technical discussions of the solar thermal plants, you'll find they actually have to dump energy in optimal conditions - they aren't expecting to get the absolute best possible solar exposure at all times.
When selecting appropriate locations (using detailed insolation data) they are looking for places which really do get very reliable sun - not somewhere which gets 130 days of sun per year.
16 hours of storage is more than enough except in rare cases (don't forget, plants don't always generate at peak output - and that includes traditional gas and coal fired power too - they get adjusted up and down to match demand - and there is much less demand at night, weekends and days where the weather is mild).
I think the issue of how much solar intensity decreases during winter is probably more important - which points towards locations closer to the equator - and if you do a plot of all the plants being built, you'll see that is where they are heading (as far as is practical - right on the equator is generally too cloudy).
Ausra already used real climatic data (although they arranged them randomly throughout the year) and found >90% correlation with the national load. If the plants are geographically dispersed then the problem of climatic extremes is reduced. But, it makes sense to be prepared for the worst.
Substantially more storage than 12-16 hours to deal with longer climatic irregularities is suboptimal from an economic viewpoint. If CST is to be the main supplier in the national grid, then it will make more sense to install emergence natural gas heaters (relatively cheap). A strategic natural gas reserve, and the existing natural gas networks could be used for this purpose. A month at full load would be more than enough to survive even the longest cloudy periods. In the future, biogas could be used with modest modifications on infrastructure. The quantity required is very low, just for the occasional emergence, not for regular operation, so this should be quite feasible.
Oh, and dealing with the winter load isn't that big a deal. An east-west axis orientation line focus plant, in a good location, has very consistent seasonal output. Most of the parabolic troughs built in the Mojave were north-south oriented to get a high summer bias, which is good for California, but if CST must provide a large chunk of the national generation then most plants would have to be in the east-west orientation.
Thanks for the feedback.
I agree with the natural gas / biogas backup idea - I guess that is why David Mills is only aiming for 90% of the power supply :-)
Thanks. They did say 100% would be possible if required, but that it would increase the cost a bit.
Now, I don't suggest it's a good idea to rely on solar thermal for 100% of electric needs, but in the hypothetical case that it does happen, it's better to use the backup heaters for this last bit as well, as much less energy would have to be dumped from the array and the occasional week or two of bad weather/sandstorms could be dealt with as well. And most of the existing infrastructure could be used, which is great.
With enough biogas in strategic reserve (use existing/depleted natural gas fields), this is one renewable energy scheme that is actually full proof at a plausibly reasonable cost. And that's rare.
Thank you, this is very interesting information. Unless it is certain that solar produced energy will be effective, then we must not get to enthusiastic about it. I must admit however that if it is realistic , it should be seriosuly considered.I believe, however, that with a few selected locations , this proposal could be successful. Even if solar power only works to take over even 5% of fossil fuel production, it is still better than nothing; considering that it remains feasible. The fact mentioned in the article that solar thermal plants could provide more than 90 percent of current U.S. power demand at prices competitive with coal and natural gas is very interesting. This illustrates that there is potential; espescially considering The fact that other nations are investing in solar energy research as well. Costs are apparently an issue. I believe it is essential for government funding to play a role.This woudl facilitate testing otu whether the proposed solar producing sites would be productive.
I must conclude however that we should give solar energy a try because it has many positives.It can be converted to thermal energy and be used to heat homes, and buildings, relieving stress from other non renewable energy sources. After all, soalr energy is a natural "free" resource that never technically runs out. It is essential to at least try other alternatives in order to elminate this dependence on fossil fuels.
As Prof Goose would say, thanks for your support :
http://reddit.com/info/6edxp/comments/
Because of the recent EROEI discussion, I'd give this link for a CSP estimate: http://www.ases.org/divisions/electric/newsletters/2006-04.html#roi
27 with storage and 44 without with Eout in electricity, not thermal.
By combining CSP district water heating with PV I get a cost estimate for electricity at under a penny per kWh here: http://mdsolar.blogspot.com/2008/03/lux-lucis-tepida.html
The water cools the silicon allowing a much higher concentration of sunlight. Also, the water shields the silicon from cosmic ray induced defects so that it lasts much longer. There may be immediate potential for 3 GW average electric power in the US by this method.
There is a lot of potential for CSP.
Chris
Hey read this: http://www.abc.net.au/science/articles/2008/01/16/2139711.htm
Imagine 99.95% of the light energy absorbed as heat through a coat of these nano-tubes on the inner tubes of these CSP stations. I imagine with use of vacuums and Stirling engines that it would essentially be 50 % + efficient solar power. A revolution in nano-tube production is needed to bring down cost though, they can run more than 250,000$ a ton. I can't see how coal or nuclear could compete with a system like this, plus the only emissions are from the materials manufacture which could be converted over too renewable sources essentially, emission free power.
I'm gonna stop before I start to sound like a techno-phile, ewww
Regards,
Crews
The standard coatings on domestic vacuum tube solar thermal water heaters using multilayers of materials like nickel sulphide and oxide and aluminium nitride already achieve absorptances in the visible of 94% while having emittances in the long infra-red (to stop re-radiation) of 8%. The gain from going from 94% to 99.95% is very little and the cost of going from a relatively low technology of such multilayer films to carbon nanotubes is at present huge. It will have to fall a long way to make it worth such a small gain
The article does not quote the infra-red emittance of the carbon nanotubes but this is a vital parameter. Since by Stefan's law, radiated energy rises as the fourth power of the absolute temperature and these utility sized solar thermal units operate with their absorbers at a much higher temperature than domestic units the re-radiation losses will be much higher. A small increase in infra-red emittance will easily wipe out the gain from a slightly higher visible absorptance.
I think that reducing reflectivity helps quite a bit, that was one of the main effects in improving efficiency in BigGav's second PV link on multicrystalline silicon. But, the main limit for this type of PV is the electronic bandgap which ends up only being responsive to a portion of the solar spectrum. Usually, PV is used with concentrators when it is multijunction so that there is more than one bandgap. That material is expensive because it is complex to manufacture and it is optimized to run hot, though not as hot as concentrated solar thermal. It is sometimes worth it though because you need less of it. What I have in mind is to use regular silicon and run it cold, but then use the low grade heat from the cooling water to save some energy in home water heating thoughout a small town. Because there is no need for really high tempertures and because existing infrastructure is reused, the cost comes in pretty low. Lower reflectivity in the panels means that much more heat for the water.
Chris
Chris;
In response to your blog entry, am I clear that the PV is in the water, facing UP (clear tank-roof), or is it attached to the underside, facing heliostats?
In either case, it sounds like an interesting synthesis.
-If immersed, do you have a sense of the Visible Light transmissivity through that much water, and it's effect on PV absorbtion?
-Second, did you find a good source of info for how much light a water-cooled PV panel can be subjected to, and how this affects it's potential output and lifespan? You touch on these, but I'd love to see some documents on test-results for such setups.. I would hope that it's possible to toss maybe 3 to 6 'Suns' at a panel that is aggressively cooled to boost it's yields, without compromising on its durability. Your proposal to shield the PV from cosmic rays with water sounds good up front, so has it been tried out to any degree that you are aware of?
Best,
Bob Fiske
Hi Bob,
The idea is to hang the panels from the bottom of the tower and cool them with running water on the unilluminated side. There is a program in New Mexico that just got funded to do this kind of plumbing. I mentioned it here:
http://mdsolar.blogspot.com/2007/07/new-mexicans-conspire.html
Sunlight does not harm silicon though it can have an effect on epoxies and such in the rest of the panel structure. Heat cycling can cause delamination of electrical contacts. On the cosmic rays, this has been an issue in the semiconductor industry for a while, and is quite well known for space applications. Water is used as a cosmic ray shower detector in the Auger Observatory and it would not see them if it could not stop them. Basically, at those energies it is mass that makes a difference though some metals can produce a secondary X-ray flux which can be a problem for shielding humans. Since ground radioactivity is lower energy, 50 meters of air should be a help. It seems to me that all you would need to do to check would be to put a scintillation counter in place and hang a second off a boom or put it up on a pole nearby. You should have enough data in a week or less. If you have a tower in mind, I can try to do a more detailed calculation of the relative flux just below and out away from the tower. I know of one proposed experiment to put some panels in the Goldstakes mine for a long time to check their degradation. Don't know if it went forward. It is easier to look at data from space or take a panel to an accelerator to understand the degradation mechanism.
Other degradation mechanisms owing to water getting into the panel frame might be avoided in this enviroment as well. It should not be too difficult to keep the panels warmer than the ambient environment at night since the warmed water is available so that even with a small leak, condensation within the panel might be avoided. This would tend to protect anti-reflection coatings and electrical contacts.
Chris
There are at least 2 typos in the table. The sum of the listed embodied energies (without storage) totals to 175.2GWh, not 174.2GWh. The EROEI calculates to 34, not 44. Still good, but not 44.
I agree. Thanks for catching that. I notice also that no estimate is made for running the heliostats or pumping the salts. I'd like to see more thorough work on CSP if you know of any.
Chris
I would like to see an EROI estimate of Ausra's CLFR. Considering the compactness and lower structural (mirrors close to the ground) and material requirements (low temperatures and pressures) it should do pretty good.
Very nice! I was wondering when someone would innovate a combined PV/CSP array.
Thanks Big Gav - this is the best summary I have seen on Solar Thermal.
Excellent Article;
Thanks a lot.
An excellent guide to solar thermal power - thanks.
A couple of points, firstly the estimates I have seen are perhaps a bit more conservative on present costs, with figures of around 20-30cents/kwh hour mentioned:
http://www.renewableenergyworld.com/rea/news/story?id=51889
As against that though, you don't really need to compete initially with base-load costs, as in most of the most suitable areas power use tracks very well with solar incidence as it is mainly used for cooling.
There is a lot more flexibility in costing when it is for peak power, so you don't need to hit baseload costs. Increasing costs for natural gas which is the fuel of choice for peaking power should rapidly mean that solar thermal is the preferred option.
Many of the hot areas are also short of water, which makes it easier to use solar thermal than coal or nuclear power with their large cooling requirements. It should be noted though that water use in solar thermal is not negligible, as you need to clean the mirrors.
There is also no free lunch on environmental concerns, as you are using substantial areas of land and affecting the ecology. This would seem to me to be very manageable in most areas though.
There are also possibilities for using solar thermal power in some fuel cycles to replace oil use, for instance in a zinc cycle where the heart for a solar tower directly transforms zinc oxide into zinc, for use in batteries which are very dense in energy terms as they can use air as one of the inputs.
http://www.meridian-int-res.com/Projects/The_Zinc_Air_Solution.pdf
The_Zinc_Air_Solution.pdf
Many areas of Australia would appear to have the needed sunlight and access to forestry resources - ideally you would not want to transport the timber far.
This is a very advantageous process, as you are not transforming the energy form one form to another, which is always done at a cost.
There is also the possibility of using boron in a fuel cycle, as this fascinating site details:
http://www.eagle.ca/~gcowan/boron_blast.html#TOC
A car running on boron could have cross-continent range!
In either case the chance to turn out a useful portable fuel would seem to mean that perhaps even if solar thermal were around 20c/kwh, then perhaps it would be cost effective.
Dunno about sunlight and forests but I live near to zinc mines http://www.zinifex.com/ and forests. The sunlight bit is unreliable. The zinc concentrate is shipped by coast (ie skirting around the central forests) to an electrolytic smelter that allegedly pays 3c/kwh 24/7. Their hydropower is runoff from the same forests. Just don't eat the fish downriver of the smelter. Zinc oxide + charcoal is not on their radar yet they would seem to have the head start.
Sometimes I just hate being years ahead.
Three things not mentioned above:
Sometimes I just hate being years ahead.
And without returning the micro-nutrients in the charcoal back to the soil, years wrong.
It should be noted though that water use in solar thermal is not negligible, as you need to clean the mirrors.
True, but it's not a big problem either (water for wet cooling would be in most arid areas). The water use is much lower than most agricultural practices. Although, in the areas best suited for CST, most agriculture wouldn't work very well!
Chemical heat storage is interesting, but so far only demonstrated on small scale and it was very expensive. Perhaps scale-up would reduce the cost enough.
Could you please clarify whether or not the costs cited for solar thermal includes distribution and all other costs associated with actually transmitting the electricity to the retail customer. I assume this varies, but is there some sort of agreed upon range for comparison purposes.
Or perhaps we only need to be concerned with the marginal distribution costs of producing from the mojave desert.
A project recently in the news is Southern California Edison installing 250 mw on commercial rooftops in Los Angeles. The advantage of this approach is that it can feed into the existing local greed and not require additional transmission lines, etc. to make it all work. Might this approach reduce some of the advantage that solar thermal may have other PV?
No - the costs don't include transmission costs - they would vary wildly depending on where the plant is located and how far it is to the grid.
A plant in the middle of the Sahara or Simpson desert would have much higher additional costs than the Mojave, which is close to the Californian grid (and has interconnects to elsewhere going across it I suspect).
One of the articles I linked to for a southern Californian CSP plant also discussed the 250 MW "distributed" PV power plant in LA. I think this is a great idea - putting PV on commercial buildings makes excellent sense, though I'm not sure it will be quite as cheap as CSP in the long run.
Nevertheless, I don't see PV and CSP as competitors - CSP fits the centralised generation model well (especially when storage is included) but I'm very keen on distributed generation, which means lots of PV and thin film.
We'll see how the relative economics work out in a decade or so.
Thanks for your response.
I have been successful in getting my local utility to provide net metering. Next step is to convince them to provide a rebate for installation of solar panels on customer's homes. But here's the rub. Since it is clearly cheaper to use a centralized approach to solar power, whether using panels or CSP, the utility may take the position that it does not make any sense to encourage distributed generation.
From a utility's perspective, why would distributed generation be a good thing if the costs are not advantageous.
Net metering is a good first step - ideally your regional government will legislate for feed-in tariffs as well.
Utility companies are unlikely to see much benefit in encouraging distributed generation (especially if they don't own the generation equipment), so encouraging this is more in the domain of government - especially if the government owns the transmission infrastructure - in which case it can build a business case for subsidising solar panels and avoiding building more transmission capacity (ditto for smart meters to a certain extent).
Thanks Gav,
Your work and references fill an important gap in the post-carbon toolkit. Now to get it into the hands of those who do the heavy lifting (and jaw-dropping piano-smashing!) in the capital markets. Try cleantech.com and others. Is it not time for solar bonds? Maybe Aussies can configure them if too much of a departure from US energy values/norms.
I like the SciAm piece because it locates its central project in the heart of the US electrical demand beast, across 32,000 km2 of bare-earth right next to the backyards of the most innovative souls on earth, at least per their own self-image! Economic with relatively tiny rate subsidy (under certain potentially reasonable assumptions of course).
Beats bashing bitumen and other innocent tarbabies. We didn't ask to be born near the oilsands or heavy oil and sour gas fairways. From one sick and tired native Albertan...
Just do it.
Big Gav
Thanks for the excellent summary of the status of this technology. A couple of comments about the economics:
- Australian power generators, up until a year ago, were selling in to the grid at average prices of between $25 and $30 per MWhr(2.5c - 3.0c /kWhr). The power stations were still turning a profit at this price level. There has been a bit of a change in the pricing structure over the past year. The reasons are a bit too complex to deal with here. The point is that any competing technology needs to either be subsidised or taxed into competition with coal at these price levels.
- Through my work I have done extensive study into costing of Solar Thermal. My company built one of the only full scale solar troughs in the country. The figures quoted for the construction of a large scale solar thermal facility are pretty accurate. We have estimated it at around A$3100/kW.
- A solar thermal plant utilises the same technology as a coal fired plant for the bulk of the facility i.e. the solar collectors only replace the boiler component of a conventional plant. The boiler constitutes only 40% of the plant costs. You can therefore consider A$1900/kw of the cost fixed and not subject to either volume or technology induced improvement. The claim that the build costs can be reduced to US$1500 is simply wrong. It won't happen.
- Utilising the build cost of $3100/kW and feeding it into a financial model with a few other inputs for operations and maintenance results in a electricity sale price of around $230/MWhr.
I sincerely wish otherwise but the above are the plain economic facts. Either through tax or subsidies the electricity generation price would need to increase 7 fold to make solar thermal viable for stand alone base load operation. On the positive side the retail price of power will "only" have to increase around 150%.
Either Solar thermal or large scale PV will happen, but there will be a lot of screaming and nashing of teeth before it gets there.
Hi Phoenix,
If 60% of the cost is fixed and is common between coal and solar thermal plants, how did the they turn out power at 2.5-3cents/kwh if they have $1900 of fixed costs in common with solar thermal?
The coal-fired plants would not only have build costs, but also the cost of the actual coal.
Presumably a lot of the difference is due to utilisation rates, as the solar plant only operates at around 25% of capacity, and a lot less in winter, even in latitudes as southerly as the Mohave.
Do your calculations take into account the proposals for storage which are an integral part of why Ausra, for instance, say that they can actually reduce costs whilst building storage.
I wonder if you would comment on the costs of maintenance? And the water use for cleaning? It is no trivial matter to maintain a set-up which covers vast areas.
Davemart
There are a number of reasons for the differential:
- Higher efficiencies achieved by the coal plant due to higher operating temperatures
- Lower cost of the equipment because the optimal size for the coal plant is 1000MW while the solar plant size will be less than 100MW.
- Equipment utilisation, the coal plant runs for 8100 hr/year while the solar plant will only operate effectively for 2100 hr/year.
That being said, I realise I did in fact make a mistake in my post. The "common" equipment constitutes around 60% of the cost of the coal plant but only 25% of the cost of the solar plant. The cost reduction required for the solar portion of the plant (to get to US$1500 /kW) would be from a current level of A$2300/kW down to $850 /kW. I still don't think this is credible.
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I have used in my model a cost for operations and maintenance of around $25 /kW/year. This is a very agressive number and takes into account a good deal of the learning curve that will be experienced in the initial developemnt of large scale plants.
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For the most part water usage will be similar to coal fired plant. Mirror cleaning is trivial. The water will be used for cooling. In this respect the solar plant suffers from the same problem as a nuclear plant in that the lower efficiency means that more heat has to be removed from the cycle. It will therefore, if anything be a higher water user than a coal fired plant.
Hence the plants proposed for Morocco and Algeria are co-gens with natural gas, and in about those ratios, ie 75% of the power is natural gas, with the balance solar thermal.
Contrary to what some here think, that I am totally for nuclear energy only, I have looked hard to try to find renewables that will work at any reasonable cost, and about the only two which can generate any substantial amounts of power so far are residential solar thermal and on-shore wind, and neither will really power our society
Geothermal might have some potential, but it is very early days, and PV has it all to do, although certainly in off-grid situations it is about the most promising.
Otherwise, if you don't want greenhouse gasses and don't want to go bankrupt, every time it comes back to nuclear power.
Oh please (rolls eyes). If you add together all the possible unexplored efficiencies + smaller societal energy footprint + willingness to pay more for power and you have loads of potential for CSP, PV, wind, tidal, geothermal and more. It's only those who lack imagination who insist we need a monolithic, known, centralised solution (like nuclear energy) to keep powering us along in the luxurious lifestyle to which we've become accustomed.
If you extrapolate anything far enough, then you can come up with something that sounds as though it can work.
The problem is we need it now, not at some unspecified point in the future.
Tidal generation, for instance, is hopeful, but suffers from being, well, tidal, so it peaks twice a day without reference to when you need it, so you not only have to cost for equipment in difficult environments but build buffering facilities.
I find it difficult to understand how so many work without reference to cost - most folk are going to have to tighten their belts anyway, and there just will not be the money available for all of these 'cunning plans', and the higher costs some are so keen on will mean real suffering to real people.
Particularly when we have perfectly adequate possibilities open to us which will do the job just fine at reasonable cost and do not involve giving up a decent standard of living.
The uncharitable response to your comment would be that it is only those who can't face reality who would advocate that we should go for solutions that we don't know how to engineer.
At the moment billions are being made based on totally unrealistic prospectuses.
Want to buy the Brooklyn bridge? Projections show it will be a money maker real soon.
If you use cost as the only measure (ignoring externalities as per usual), the cheapest approach in the short-medium term is increasing efficiency (or negawatts, as Amory Lovins dubs this 'resource").
Mandatory fuel efficiency levels for vehicles, mandatory low energy lighting, better insulated buildings, mandatory gas or solar hot water, shifting more freight to rail and sea, urban planning that encourages walking, cycling and public transport etc etc etc
Every study I've seen shows this - even the pro-nuclear "The Economist" has pointed it out.
If you were concerned about cost above all then you'd be pushing efficiency first at every chance you got...
Most studies incorporate several scenarios - the optimistic, business as usual, and pessimistic. Those in the optimistic camp typically assume a degree (fairly mild to very aggressive) of efficiency and conservation programme implementation. But energy bulk demand increases in nearly all cases due to population growth and development (such as more people getting air-conditioning or that second TV for the bedroom).
Also, one worry I have is an unstated assumption that efficiency improvements and conservation are something new and are not already being aggressively pursued.
If you look at this chart from the IPCC, you will note that during the 1970's energy crisis, the emissions and GDP lines begin to diverge. This is due to efforts that were commenced at that time (and continue) to conserve energy and improve efficiency as well as programmes to introduce nuclear power.
Efficiency and conservation are good initiatives that will help, but - in total and considering the broader perspective of population projections and ongoing development - there is risk in presuming they will bear significant fruit with respect to real emissions cuts.
Here is a link to an old web page of mine, Gav, where it is very clear that as far as I am concerned it is less use and more efficiency every single time:
http://energy-futures.blogspot.com/2008/02/conservationour-best-route-to...
Please note also that my comments about the roles of different power sources are particular to the UK, and in Australia for instance solar, thermal and PV, can help a great deal towards peak load capacity - the problem is being too hot, not too cold as is the case in the UK.
However, it seems perfectly clear from the expert comments of Phoenix that the idea of running base load from solar thermal even in Australia is a non-starter - you have to buy too much equipment which stands idle most of the time due to solar intermittency.
I think I recollect that you were also fairly critical of the heat output to water from nuclear power - apologies if I am mistaken - it is clear from phoenix's comments that that is at least as severe for solar thermal, - water usage in desert areas along kills it.
But we must also note the following characteristics of solar thermal:
Hot