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Solar vs. solar

by DoDo Thu Sep 1st, 2011 at 06:39:37 AM EST

Some recent news got me to look at the state of concentrated solar power (CSP), in particular in Spain. In short, the technology matured and entered series production in the last couple of years, however, in spite of that, the recent radical price reductions for photovoltaic solar cells eliminated their price advantage in utility-scale projects. The CSP supply chain is dominated by Spanish and German companies.


There is a multitude of technologies used to convert solar radiation into electricity. From an economic point of view, it makes sense to separate them into two categories: (classic) photovoltaic (PV) power, in which solar cells of various materials are exposed directly to sunlight; and concentrated solar power (CSP), in which mirrors concentrate sunlight on a receiver. If I got the categories right, CSP includes the more mature solar-thermal power technologies, in which a heat-absorbing medium passing through the receiver drives a generator; as well as concentrated photovoltaic (CPV), in which the concentrated sunlight is absorbed by a high-quality multijunction solar cell. (Update [2011-9-1 1:36:55 by DoDo]: Discussion in the comments indicates that CPV is not, after all, part of CSP.)

For photovoltaic power, the bulk of the cost is in the manufacture of the solar cells, thus the cost of a single large project is not much higher than the cost of several small projects that together generate the same amount of electricity. This makes the use on any free surfaces greater than a few square metres viable.

The most expensive parts of CSP are the receiver and the generator (turbine), thus there are significant economies of scale to realise by adding more mirrors. That means a viability as utility-scale project, and also means a need for cheap non-arable land. In addition, solar-thermal technologies can also store energy and thus continue to generate by night, reducing intermittency and even enabling some controlled variable output.

With these different characteristics, how does the spread of PV and CSP compare?

First let me note that there is a common misconception about scale: the notion that for the installation of large amounts of generating capacity, a technology needs single projects to have large power. However, if the technology and regulations are such that small projects can draw in more investors (i.e. even homeowners) and can be realised by mastering less bureaucratic hurdles, the opposite can be true.

In spite of a higher cost of electricity produced, PV took off earlier than CSP: annual new PV installations were in the gigawatts worldwide every year since 2004, with 14 GW added last year. Booms in Germany and Italy included mostly rooftop installations, but large on-ground projects also spread, and were the bulk of the 2008 boom in Spain.

In the last few years, however, CSP also entered the series production phase, with dozens of plants built or being built in Spain alone. Capacity and production data for Spain by the end of June 2011 from Comisión Nacional de Energía:

Year Total generating
capacity
(MW)
Net
change
(MW)
Electricity
generated
(TWh)
PV CSP PV CSP PV CSP
2005 47 0 25 0 0.040 0.000
2006 146 0 98 0 0.105 0.000
2007 690 11 545 11 0.484 0.008
2008 3,398 61 2,707 50 2.528 0.015
2009 3,416 232 18 171 5.939 0.103
2010 3,847 532 432 300 6.388 0.692
H1/2011 3,931 699 84 167 3.546 0.650

(Note that due to the collapse of the PV market with the 2008 FIT changes, we can estimate the overall PV capacity factor for 2009: a respectable 19.9%. For CSP, my guess from the numbers is that it was similar or somewhat lower.)

What about support schemes?

In Spain, there are two schemes: one giving a surcharge on the market price, another giving a guaranteed price. For simplicity, I look at the latter only.

Currently (Q3/2011), the guaranteed feed-in tariff for newly installed PV ranges from 13.0324 c€/kWh for (large) on-ground farms to 28.1271 c€/kWh for rooftop installations below 20 kW. If I read the laws right, these rates are now fixed for the first 25-30 years of operation of a plant (like in the German feed-in law).

The rates are re-set every quarter since late 2008 (when they ranged between 32-34 c€/kWh), and have been cut strongly this year, especially for on-ground installations (their FIT was practically halved). It does appear that the measure again throttled the PV market in Spain, however, not to a standstill: even with this quarter's super-low FIT, 39 MW of new on-ground PV capacity was added.

For solar-thermal, there is still one FIT for all plants (old and new) which is re-set regularly, and this year it is set to 29.0916 c€/kWh. That's actually higher than in earlier years. It appears no price cuts were achieved yet that would warrant FIT reductions in Spain.

Although the support schemes differ too much to say for sure, it appears that utility-scale on-ground PV is now cheaper than CSP, in spite of the latter entering series production. The impression is confirmed by a decision two weeks ago to covert the first two units of a monster 4x250 MW project in the USA from CSP to PV. This was reported by melo in the Salon, but I quote the company press release:

Erlangen, 19 August 2011 With respect to the development of the world's largest solar energy location with a capacity of up to 1,000 MW in the Californian city of Blythe, U.S., Solar Millennium AG (ISIN DE0007218406) decided to take a new path in the last week. Instead of the previously projected concentrated solar power (CSP) technology in the form of parabolic trough power plants, the first two 250 MW plants are now to be equipped with photovoltaics (PV). With this decision, the managements of Solar Millennium and Solar Trust of America are reacting to the changed market conditions in the U.S. featuring far more profitable prospects for the use of PV in solar power plants that do not require storage.

They are quite frank about PV being the cheaper option – even accounting for special US support schemes benefiting CSP:

The decision to revert to the significantly less costly PV variant also means that Solar Millennium will finance the power plants on the free capital market and forego the loan guarantee by the U.S. Department of Energy for Blythe 1 and 2.

Then they insist that they haven't given up on the technology outside the USA, underlining the non-financial benefits of CSP:

"The decision to use photovoltaics in Blythe does not mean the Solar Millennium Group is turning away from its core technology of solar-thermal power plants. According to our understanding, the market differentiates between base load solar-thermal electricity generation or concentrated solar power on the one hand and photovoltaics for peak load demand on the other. Whereas the electricity from solar-thermal power plants was more economic only less than two years ago, this relation has changed completely due to the sharp drop in PV module prices, particularly from Asia. Due to its suitability for base load supply, many regions still attach great value to CSP in their energy mix, thus supporting the Solar Millennium Group's growth opportunities."

Putting it more bluntly, there is no overall energy plan and market short-termism rules in the USA. However, I think the more important difference is the way regulations (support schemes) are set up. As much as a surprise it is that PV can be cheaper than CSP, the latter is still at its infancy, so it's not necessarily a valuation of baseload, but fostering an industry in the hope of future lower prices that justifies higher supports.

Update [2011-9-1 4:54:18 by DoDo]: I also looked at the supply chain.

The generous support system in Spain did lead to the development of domestic companies, but not yet across the whole supply chain:

  • Receivers: SCHOTT Solar (Germany) and Siemens subsidiary Solel (Israel; successor of Luz, which made the plants in Califormia two decades ago) dominate the market, there is also Archimede Solar Energy (Italy; Siemens has 45% stake).
  • Mirrors: manufacturers include Flabeg (Germany; already supplied the plants in California), Abengoa/Rioglass (Spain; took market leadership from Flabeg last year) and Saint-Gobain Cristalería (Spanish subsidiary of a French company). Both Flabeg and Rioglass established factories in the USA; now I wonder how much work those will get.
  • Pumps: Ensival-Moret (France; market leader), Flowserve (USA), Friatec (Germany).
  • Turbines: Siemens and MAN Turbo (both Germany) are the only suppliers I could find.
  • Mayor developers include the Spain-based companies COBRA (300 MW on-line), Acciona (264 MW) and Abengoa (181 MW); as well as Germany-based Solar Millennium (initial partner in 200 MW of projects in Spain) and Japan-based Mitsubishi (partner of Acciona in most of its projects).
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I note that there is a discrepancy between the list on Wikipedia and the official data at CNE: one 50 MW plant built in 2010 is apparently not accounted for in the latter.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Wed Aug 31st, 2011 at 01:14:18 PM EST
terrific post dodo--and muchas gracias for the cne link.

paul

Paul Gipe

by pgipe (pgipe(at)igc.org) on Wed Aug 31st, 2011 at 05:57:08 PM EST
[ Parent ]
I updated the diary with a section on the supply chain. Any additions/corrections welcome.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Thu Sep 1st, 2011 at 04:56:02 AM EST
[ Parent ]
European Tribune - Comments - Solar vs. solar
If I got the categories right, CSP includes the more mature solar-thermal power technologies, in which a heat-absorbing medium drives a generator; as well as concentrated photovoltaic (CPV), in which the concentrated sunlight is absorbed by a high-quality multijunction solar cell.

Is this really how CPV is categorised by the industry? It certainly doesn't make any sense in terms of your discussion to group CPV with solar-thermal:

  • no storage potential
  • little economy of scale.

It is, however, possible that the emergence of CPV may be swamped, just like solar-thermal, by the cost reductions in classic PV.

It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II
by eurogreen on Wed Aug 31st, 2011 at 01:21:46 PM EST
Is this really how CPV is categorised by the industry?

I looked up a few sites and wasn't sure myself (as indicated at the start).

little economy of scale.

Is that true? For all types of CPV? Does the requirement of tracking systems not result in economies of scale? For that matter, how big can a single concentrated solar unit (concentrator + single receiver solar cell) be? (I'm really asking, I don't know much of CPV.)

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Wed Aug 31st, 2011 at 03:22:24 PM EST
[ Parent ]
The simplest CPV I have seen had two slanted mirrors at the sides of a PV film and the opening in line with the suns trajectory. Needs tilting over the year but not tracking during the day.

Sweden's finest (and perhaps only) collaborative, leftist e-newspaper Synapze.se
by A swedish kind of death on Wed Aug 31st, 2011 at 03:30:22 PM EST
[ Parent ]
I have, however, seen CSP elaborated as Concentrated (Thermal) Solar Power, which suggests that CPV is a subcategory of PV and CSP a subcategory of TSP.

The ambiguity if that CPV needs to be cooled, and if you use the heat contained in that coolant to some useful purpose, then you have a hybrid CPV/CSP system, even if the CSP element is essentially co-generation.

The built in advantage that PV has in generating electricity is that it generates electricity originally, rather than collecting heat and converting it. The flipside for an application actually required heat of a grade that CSP could deliver would suggest an application for CSP to provide that heat, either directly or upgraded by using it as the above ambient temperature source for a heat pump.

Which clips around the vision of a decade ago of utility scale CSP installations and dispersed PV installations, to utility scale CPV installations and a mix of dispersed CSP and PV installations.

On the residential side of the grid, where a fair incentive would include the reduction in load at the substation serving that residential neighborhood, a mixed CPV/TSP panel that harvests both heat and electric power would seem to offer some potential utility.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.

by BruceMcF (agila61 at netscape dot net) on Wed Aug 31st, 2011 at 06:56:34 PM EST
[ Parent ]
I do not know what terminology is used, but solar-thermal has historically ran all the way from smallish (without storage potential and little economy of scale) to large plants.

In real terms I think PV and concentrated solar-thermal are the two big ones, which makes the exact drawing of the lines less relevant as long as these are two are in seperate cathegories.

And just to mix things up, there also exists combined PV and thermal like Zenith Solar.

Sweden's finest (and perhaps only) collaborative, leftist e-newspaper Synapze.se

by A swedish kind of death on Wed Aug 31st, 2011 at 03:28:09 PM EST
[ Parent ]
One point about concentrated solar power is if it's used to collect heat for a turbine (for example, to boil water), then you're running a heat engine and have to have a cooling facility.

As may have been mentioned here in the past, there is concern about whether Arizona may effectively ship a meaningful fraction of its precious water rights to California in the form of electricity by this method.

http://www.azcentral.com/arizonarepublic/news/articles/2010/01/17/20100117water-solar0117.html

I think it's pretty clear that PV and batteries are going to be the way to go ultimately. Timeline is uncertain...

by asdf on Wed Aug 31st, 2011 at 07:33:35 PM EST
Yes, that's the advantage of the Stirling cycle versions in the desert setting ~ its closed cycle and air cooled in the shade behind the mirror array. OTOH its not a stored heat system.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.
by BruceMcF (agila61 at netscape dot net) on Wed Aug 31st, 2011 at 11:12:11 PM EST
[ Parent ]
I got MY stored heat system working again. Gotta put a tempering valve in the hot water line now. I can collect forty gallons of 150F water from a dead stop with a 4x10 thermal collector.

Yeah, I know you're talking about electricity.

Align culture with our nature. Ot else!

by ormondotvos (ormond.otvosnospamgmialcon) on Thu Sep 1st, 2011 at 03:17:24 AM EST
... to state the obvious. Spain is doing the strategic thing, with a higher tariff for CSP than for PV.

The parts of the US which are especially suited for CSP (both thermal and PV) happen to have a peak period which is largely driven by air conditioning, if I have understood directly. This means that PV can actually get the best tariffs, and that the storage possibilities of thermal CSP are negated.

This is a severe handicap for thermal CSP, because the southwest USA is where it's at currently for utility-scale solar.

PV CSP is starting to take off in a big way there, for that reason.
SDG&E, Soitec Add 2 Local Solar Sites | Xconomy

San Diego Gas & Electric has added two more 25-year contracts with French-based Soitec, which will supply a total of 125 megawatts from solar energy sites using Soitec's Concentrix CPV (Concentrating Photo-Voltaic solar panel modules.

In a statement today, the two companies say Soitec Solar Development will manufacture the modules in a new factory to be built in San Diego. The two local agreements follow three previous contracts for 30 megawatts of CPV-generated solar power.

(Note that the Concentrix system doesn't require water cooling.)

Will there be only one cost-competitive technology, at the end of the day?

Tracking the CPV Global Market: Ready to Fulfill Its Potential? | Renewable Energy World Magazine Article

As with all forms of renewable energy the first question anybody usually asks is 'What does it cost?'. With an emerging sector like CPV there is currently no simple answer. The big hope for CPV is that by using smaller amounts of photovoltaic material at high efficiencies it will be able to drive down costs and compete with fossil fuels - a hope shared by thin-film PV and concentrating solar thermal.

At present, CPV still has some way to go, although it does have some factors in its favor. Certainly, in terms of installation costs per kW, CPV is far from the cheapest. According to GTM, the pre-profit cost for a high-concentrating multi-junction system is roughly $3.35/W installed, compared to $2.04/W for thin-film CdTe and $2.52/W for polysilicon.

What really matters, though, is the cost per kWh produced, and here things are a little better for CPV - it can operate at capacity factors of up to 26 percent, compared with 20 percent for CdTe. Once that is taken into account, CPV is considered to be broadly competitive with non-concentrating PV.



It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II
by eurogreen on Thu Sep 1st, 2011 at 06:48:08 AM EST
Will there be only one cost-competitive technology, at the end of the day?

I think multiple technologies may survive in different niches, e.g. I don't see CPV playing much of a role in the building-integrated market and I don't see the latter collapsing even if CPV becomes decisively the most cost-competitive on the open field segment.

Then again, Solar Millennium said just back in June that they want to build combined PV-CSP plants, with CSP on flat ground and PV on
hillsides within the area of permit.

What really matters, though, is the cost per kWh produced, and here things are a little better for CPV - it can operate at capacity factors of up to 26 percent, compared with 20 percent for CdTe.

But the capacity factor is not the only factor making the difference in cost per kWh. Compared to the common fixed flat panels, CPV also requires a tracking mechanism and usually cooling, both of which result in extra maintenance costs.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Thu Sep 1st, 2011 at 09:43:03 AM EST
[ Parent ]
Though as noted above, the correct linear or parabolic mirror concentrator makes tracking adjustment a once per day task, which will be less demanding to maintain.

And the Zenith Solar system linked to above by a swedish kind of death turns the necessity for cooling from a maintenance cost into an advantage by providing both electricity and process heat from the same unit.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.

by BruceMcF (agila61 at netscape dot net) on Thu Sep 1st, 2011 at 11:08:51 AM EST
[ Parent ]
I might be in the minority here, but I am rooting for thermal solar power. And that is mainly because I like decentralisation of power.

This might seem contradictory, but we should not forget that political power does not only reside in owning power-production, but also in producing the machinery that collects power. As I see it PV is for the forseeable future a high-tech industry, requiring ultra-clean rooms and really expensive machinery. Like the manufacture of medicines or chemicals. Thermal solar is more akin to refrigerators, it is no piece of cake to build but it is on a lower level of technology.

The countries around the equator where sunlight is plentiful rarely have medical and chemical industry. On the other hand, there is probably more refrigerator repairmen then in rich (and therefore wasteful socities). So when it comes to global power balances I am rooting for thermal solar power because it is more likely to decentralise political power to the countries having plentiful sunlight and little power - in both senses - today.

Sweden's finest (and perhaps only) collaborative, leftist e-newspaper Synapze.se

by A swedish kind of death on Fri Sep 2nd, 2011 at 02:29:01 PM EST
Well, if you look at my list of companies at the end of the diary, the opposite appears to be true: specialists have to be involved in most key components, and 90-100% of those sub-markets is squared by one or two companies. The receivers are high-quality, high-tech material. While mirrors are cheaper than solar cells, these mirrors are still high-precision mirrors. The requirement on generators is no less stringent than on those in gas-fired power plants. Energy storage using molten salt is a tricky technology; there are just four companies in the world that manufacture pumps for it (from what I read up, one of them did not enter CSP market so far, and two more were involved in pilot projects only).

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Fri Sep 2nd, 2011 at 03:31:09 PM EST
[ Parent ]
Well, thermal is smaller so it can be expected to be more concentrated.

And yes, now it is developed by the west for the west. My line of thought is which branch is later easier adopted for production and usage along the equator, and my bet is on really on small thermal, which I think will benefit from advances in large solar.

Molten salt is storage and storage depends usage. But yes, if you need molten salt storage for it to make sense you are probably on a technological level where PV is as attractive as thermal.

Sweden's finest (and perhaps only) collaborative, leftist e-newspaper Synapze.se

by A swedish kind of death on Fri Sep 2nd, 2011 at 04:24:10 PM EST
[ Parent ]
My line of thought is which branch is later easier adopted for production and usage along the equator, and my bet is on really on small thermal, which I think will benefit from advances in large solar.

I'm not sure what you mean. If by "small thermal", you mean heat-generating solar thermal, that tecnology in fact has little to do with CSP and is really low-tech. As for CSP, I don't see how you get it small and cheap, and how you "low-tech" the receivers, generators and mirrors.

Meanwhile, even though PV is high-tech, half of production now shifted to domestic companies of low-wage East Asian countries.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sat Sep 3rd, 2011 at 03:27:16 AM EST
[ Parent ]
Part of that depends on the thermal solar technology. The systems with collectors that collect the heat into a central generator is one approach, but there is also the system where each individual unit is a generator, such as the Stirling generator systems.

And of course, for the hybrid system linked to above that concentrates the solar onto a CPV module and harvests heat from that module ~ which also serves to provide the required cooling ~ the heat is more likely to be used directly, for solar Heating / AC, or solar hot water, or industrial process heat, so there is not necessarily any central thermal generator in the system. That is an especially interesting approach for urban uses in low income nations.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.

by BruceMcF (agila61 at netscape dot net) on Fri Sep 2nd, 2011 at 05:34:22 PM EST
[ Parent ]
there is also the system where each individual unit is a generator, such as the Stirling generator systems.

Aren't all of those even more high-tech?

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sat Sep 3rd, 2011 at 03:29:14 AM EST
[ Parent ]
You mean in the sense that being a Stirling Engine repairman is a more technically demanding occupation than maintaining and repairing a centralized thermal generation and molten salt heat storage?

No, I don't think the maintenance of those units is higher tech than the maintenance of the centralized systems. The reverse.

As far as keeping them maintained, a country like the DR Congo would obviously need to have a means of payment to a country like Brazil, but a country that can produce to the tolerance of modern automobiles ought to be able to produce to the tolerances of those type of thermal CSP's.


I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.

by BruceMcF (agila61 at netscape dot net) on Sat Sep 3rd, 2011 at 10:38:09 AM EST
[ Parent ]


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