Supercritical: Breakthrough for Solar With Storage
June 11, 2014
In all the hoopla about burgeoning growth of Photovoltaic solar, we forget that there are smart people plugging away at other kinds of solar tech.
We’ve been on a concentrating solar power/thermal energy storage tear this week, so let’s keep the ball rolling. The Australian science agency CSIRO is working on a super duper “supercritical” steam system for concentrating solar power plants, and in a lucky twist for us over here in the US it turns out that one of CSIRO’s partners in the project is Abengoa Solar.
We stand to gain because the partnership will complement Abengoa’s considerable experience in the field, and the company has just teamed up with our own Energy Department on an advanced new concentrating solar power/thermal energy storage system. The project is aimed specifically at bringing thermal energy storage technology into the competitive energy market.
–Now, here’s where it gets interesting. Australia’s CSIRO (short for Commonwealth Scientific and Industrial Research Organisation) teamed up with Abengoa and the Australian Renewable Energy Agency to create a CSP breakthrough that consists of a solar powered system for generating super hot, pressurized “supercritical” steam.
The project apparently resulted in the highest temperatures ever achieved globally for steam generated by non-fossil sources.
Currently, solar thermal power plants in commercial operation use subcritical steam, which is hot enough but performs at a lower pressure. Boost the pressure and you boost efficiency, leading to lower costs.
The supercritical steam achievements means that solar energy could have the same rate of performance as coal or gas in power plants. When you combine that with thermal energy storage capability or with other advanced battery technology, the need for building new fossil fuel power plants pretty much evaporates.
Here’s CSIRO Energy Director Dr. Alex Wonhas waxing enthusiastically about the project:
It’s like breaking the sound barrier; this step change proves solar has the potential to compete with the peak performance capabilities of fossil fuel sources.
Instead of relying on burning fossil fuels to produce supercritical steam, this breakthrough demonstrates that the power plants of the future could instead be using the free, zero emission energy of the sun to achieve the same result.
In Australia, supercritical steam is a new thing even for fossil fuel power plants. According to CSIRO, 90 percent of the electricity in Australia is generated by fossil fuel, but only a few of those power plants use supercritical steam.
According to the CSIRO blog, the R&D team achieved a temperature of about 570° Celsius, which is hot enough to start melting an aluminum alloy. The pressure reached 23 megapascals, equivalent to a two-kilometer diver under the ocean’s surface.
For those of you new to the subject, concentrating solar power (CSP) typically works by using mirrors to literally concentrate solar energy onto a narrow field containing a system of pipes. Liquid in the pipes is heated and circulated to an electricity generating station, where it boils water to run a steam-powered turbine.
The objections to CSP focus on cost (it’s expensive) and simplicity (it’s not) compared to directly converting solar energy to electricity with photovoltaic cells.
The advantage of CSP, though, is that once the liquid is heated you have a readymade “battery” for storing heat, aka thermal energy storage. If you can figure out a way to keep the liquid hot for several hours after sundown, you can still run your solar-powered generator in the dark (the new Crescent Dunes CSP plant in Nevada, for example, uses a molten salt thermal energy storage system).
The New NREL CSP With TES Report
The new NREL CSP with TES (thermal energy storage) report is called “Estimating the Value of Utility-Scale Solar Technologies in California Under a 40% Renewable Portfolio Standard.”In a nutshell, NREL found that when you compare the CSP/TES combo to variable technologies (yes we mean you, wind and solar), you get an increase in value of five cents per kilowatt hour.
That’s assuming California meets its mandatory 2020 renewable energy goal of 33 percent and includes a lot of wind and solar in the mix, especially distributed solar.
If you boost the goal to 40 percent, which Governor Jerry Brown sees as a possibility, NREL arrives at an added value of six cents per kilowatt hour.
The key point to keep in mind is that the CSP technology alone is not doing the heavy lifting. The difference is the inherent ability of CSP plants to transfer solar energy into stored energy. Here’s how NREL runs it down:
Concentrating solar power (CSP) with thermal energy storage (TES) is a unique source of solar energy in that its output can be shifted over time and also controlled in response to system operator signals, allowing for provision of a wide range of grid services.
Climate Denial Crock of the Week 
June 11, 2014 at 10:52 am
In all the hoopla about burgeoning growth of Photovoltaic solar, we forget that there are smart people plugging away at other kinds of solar tech.
The way I understand it, there is no real conflict. Concentrating solar power needs direct sun light and is thus best for regions with almost no clouds. Photovoltaic can also use diffuse sun light and will be used in the rest of the world, where it sunny enough.
June 11, 2014 at 4:17 pm
What do you suppose the useful lifespan of this sort of power plant might be? Hundreds of years? Thousands?
Stainless steel is one of the longest-lived materials we have – it can withstand thousands of years of exposure to the elements. And in the desert, there are no elements.
If one of these plants has a useful lifespan twice or more times as long as a huge PV array, does that not make it far less expensive?
June 11, 2014 at 11:04 pm
Re: “What do you suppose the useful lifespan of this sort of power plant might be? Hundreds of years? Thousands?”
For a comparable, look at the stainless steel heat exchange tubes at the San Onofre Nuclear Generation Station. The original tubes had a service life of about 25 years (1984 to 2009). The replacement heat exchange tubing failed within one year of installation, resulting in the total loss of value of the plant.
The San Onofre heat exchangers (reactor pressure vessel head) was designed for stable high pressure operation.
In comparison, the situation with concentrating solar power systems is that they are going to go through a rigorous expansion-contraction cycle on a daily basis. Such a system, unless extremely well designed and flawlessly manufactured is doomed to have a very short MTBF (mean time before failure) lifetime. This is not a trivial problem.
As an analogous situation, compare the condition of sidewalks in cities that either never freeze or freeze completely for months on end to other cities such as the one I live in, Bend, Oregon where all winter long the temperature excursion is cycling above and below freezing. The lifetime of concrete here before spalling becomes egregious is very, very short, on the order of four or five years, in comparison with much longer service lives for concrete pavements in, for example, Los Angeles or Minneapolis.
June 12, 2014 at 12:05 pm
It’s not the steel that’s the limiting factor, it’s the mirrors. The more sandblasting they get, the worse they perform. No “elements” in the desert? Only on the Moon.
June 11, 2014 at 9:36 pm
Unfortunately though, Australian Prime Minister Tony Abbott, currently on tour in Canadia (that’s what he called it) and the US and who is looking to form an Axis of Stupidity against “job killing carbon taxes” which “other countries are moving away from”, has just sacked hundreds of CSIRO scientists for, you know, researching the wrong stuff. Like climate change.
Now anyone want to buy up some ground-breaking technology on the cheap?
June 12, 2014 at 2:19 am
Most supercritical steam experience comes from coal. NPP have the difficulty of neutron embrittlement and other unique factors irrelevant to ordinary steam PP.
In short, supercritical steam PP are mainstream, the kinks have been ironed out. Thus, for CSP, the issues have more to do with the physics of creating the temperatures and pressures, and less to do with the downstream materials outside the CSP receiver. Receiver design has been the focus of intense research for decades.
Here is the lowdown:
“The technology is now considered reliable and economically viable. The main technical challenge with supercritical plants is that the higher steam pressure and temperature require components (superheaters, headers, water tubes, steam chests, rotors and turbine casings) which are produced from nickel-based alloys.”
” In most industrialised countries, supercritical plants have become commercially viable, with capital costs only slightly higher than those of conventional subcritical plants, but with significantly lower fuel costs due to increased efficiency. Presently, over 500 SPF plants are in operation worldwide, including a number in developing countries. Most of the new power plants in Europe and Asia are equipped with supercritical coal-fired technology and in China this technology has become the standard on all new plants of 600 MW and more capacity (http://knol.google.com/k/supercritical-coal-fired-power-plant)”
http://www.climatetechwiki.org/technology/sup_crit_coal
June 12, 2014 at 10:52 am
The breakthrough on CSP is that they might be able to lower costs thru increased efficiency using higher temps. This, with storage gives them complete capability to compete straight up with the lowest cost conventional sources.
June 12, 2014 at 12:09 pm
It’s not poor efficiency which makes CSP uncompetetive, it’s the huge amount of energy collection area required (i.e., large capital cost) for the modest amount of power you get out of it. And there’s no way around that one.
June 12, 2014 at 7:50 pm
Over at Brave New Climate, guest author Dr. Ted Trainer runs the numbers on CSP and gets some highly pessmistic results:
http://bravenewclimate.com/2014/06/02/critique-100pc-renewables-edm/
One of the problems is that CSP needs nearly full sun to generate much at all. If I’m reading him right, clouds that would cut PV output only marginally can reduce CSP output to zero.
June 14, 2014 at 12:57 am
That’s not what I’m getting from his critique of solar thermal which is more than a bit confused / confusing.
It doesn’t look like he has hard numbers for power towers, only that troughs don’t perform well under cloudy conditions & Stirling dishes seem to be or should be better.
And his assertion that power drops off sharply below 6 kWh / m^2 is questionable as it means Gemasolar & Ivanpah would be poor producers more than 1/2 the year.
June 14, 2014 at 8:58 am
A certain someone is a confirmed biased renewable basher and bent on moving the discussion off topic. You are correct in that the breakthrough with concentrating solar is twofold. One, higher temperatures lead to higher efficiencies, bringing CSP to competitiveness with FF. Two, CSP brings storage with it. Those are breakthroughs. The discussion of area and shading is old. It’s not like we are running out of places to put them or places with good sun. There is a wealth of articles on the subject at Cleantechnica.
http://cleantechnica.com/2014/06/10/new-nrel-report-concentrating-solar-power-adds-value/
http://cleantechnica.com/2014/06/06/low-cost-concentrating-solar-power-gets-1-mil-boost/
June 14, 2014 at 10:17 pm
Very passive-aggressive of you. A certain someone who posts here keeps getting major claims of fact very wrong, and appears to be innumerate. Shall I name him?
On the contrary. Renewables can be wonderful in the right application. It’s just that running the 24/7 electric grid required by 20th-century society (let alone 21st) is not one of those applications. If it was, Denmark would have per-kWh CO2 emissions on the order of Sweden instead of 15 times as high.
With WAIS allegedly doomed and Greenland in the balance, we cannot waste time hoping for favorite schemes to work out. We need to go with things already proven to work and tested in the field. Sweden and France are existence proofs that even 1980’s technology can do the job. Until we can prove other options in the field, we should be building what’s already proven just as fast as we can.
For an example of things that renewables can do very well, let me bring up the example of Holland. Wind-powered pumps dried the polders reclaimed from the Zuider Zee, as fine an example of environmental remediation as you could ask for. If your process has buffers bigger than the daily or weather cycles which drive the availability of solar and wind, then they may be excellent choices to drive it.
Why does that matter? The “fuel” is free. What matters is EROEI, energy return on energy invested. Cost is a reasonable proxy for energy (adjusted for energy quality).
Ivanpah has no storage; it burns natural gas for supplemental heat. And at its cost of around $18,000 per average kilowatt, it is a very long way from being a solution to GHG emissions.
June 14, 2014 at 9:25 am
More on sand and heliostats. CSP has been a subject of research for decades. Shading, sand and dirt, and dozens of other issues have been studied. It’s not new. CSP plants have been around a long time.
http://www.sciencedirect.com/science/article/pii/S1876610214004640
http://en.wikipedia.org/wiki/Concentrated_solar_power
September 15, 2014 at 7:15 am
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