Thursday, June 30, 2011

Cost of solar power (16)

Beyond Zero Emissions (BZE), the Melbourne-based advocacy group, has attacked the decision of the Solar Flagships program to fund the Solar Dawn project.  According to the BZE report, the hybrid solar-gas concept of Solar Dawn is outdated and the Compact Linear Fresnel Reflectors (CLFR) don’t deliver high enough temperatures for best-practice renewable power generation.  BZE identifies the recently-opened Gemasolar tower plant with molten salt storage as the way of the future, so that installation will be the subject of today’s post.

First, let me mention that I analysed the Solar Dawn project in Cost of solar power (13).  My finding was that the Levelised Electricity Cost (LEC) was pretty much the same as several other large projects commissioned recently.  I don’t at all dispute BZE’s contention that molten salt storage is preferable to hybrid firing with gas.  The resources of natural gas are finite, and gas combustion only exacerbates anthropogenic global warming.  The sooner we move away from gas as an energy source the better.

I do however dispute BZE’s view that tower technology is superior to CLFR, and by inference to other solar thermal technologies.  What is important is to have cheap electricity available on a despatchable basis, and I consider the jury is still out regarding the best solar thermal technology.  Indeed I can highlight my own technology based on passive solar heat collection as a contender for cheap large-scale solar thermal power generation; for details see

The Gemasolar installation was commissioned in late May 2011 and is located near Seville in Southern Spain.  This is a very sunny location with 2,062 kWhr/(m^2.yr) solar resource.  Gemasolar is the outcome of a joint venture, Torresal Energy, between Masdar (Abu Dhabi energy company) and Sener (Spanish engineering firm).

In Gemasolar, the sun’s rays are reflected by 2,650 heliostats, each of 120 m^2, to a receiver at the top of a 150 m central tower.  The heliostats are dispersed over a land area of 185 Ha.  Sufficient heat energy is stored in molten salt for 15 hours operation, so the facility can almost be considered to provide base-load power.  Temperatures in the receivers reach 900°C and the temperature range of the molten salt storage is between 290°C and 565°C.  The peak output is 19.9 MW and the annual output is given as 110 GWhr.  Heat energy in the molten salt drives a wet-cooled Rankine-cycle steam turbine.

The UK Daily Mail reports that the cost of Gemasolar was GBP 260 million or EUR 289 million.  One further snippet I gleaned from various press reports is that the project will involve an Operations and Maintenance crew of 45.

I now evaluate the Levelised Electricity Cost (LEC) using my customary assumptions
          there is no inflation,
          taxation implications are neglected,
          projects are funded entirely by debt,
          all projects have the same interest rate (8%) and payback period (25 years), which means that the required rate of capital return is 9.4%,
          all projects have the same annual maintenance and operating costs (3% of the total project cost), and
          government subsidies are neglected.

For further commentary on my LEC methodology, see posts on Real cost of coal-fired power, LEC – the accountant’s view and Cost of solar power (10).

The results are:

Cost per peak Watt EUR 14.52/Wp
LEC                                        EUR 326/MWhr

The components of the LEC are:
Capital           {0.094× EUR 289 ×10^6}/{110,000 MWhr} = EUR 247/MWhr
O&M  {0.030× EUR 289 ×10^6}/{110,000 MWhr} = EUR 79/MWhr

By way of comparison, LEC figures (in appropriate currency per MWhr) for all projects I’ve investigated are given below.  The number in brackets is the reference to the blog post, all of which appear with the title “Cost of solar power ([number])”:

(2)        AUD 199 (Nyngan, Australia, PV)
(3)        EUR 547 (Olmedilla, Spain, PV)
(3)        EUR 205 (Andasol I, Spain, trough)
(4)        AUD 257 (Greenough, Australia, PV)
(5)        AUD 432 (Solar Oasis, Australia, dish)
(6)        USD 177 (Lazio, Italy, PV)
(7)        AUD 295 (Kogan Creek, Australia, CLFR pre-heat)
(8)        USD 248 (New Mexico, CdTe thin film PV)
(9)        EUR 218 (Ibersol, Spain, trough)
(10)      USD 251 (Ivanpah, California, tower)
(11)      CAD 445 (Stardale, Canada, PV)
(12)      USD 315 (Blythe, California, trough)
(13)      AUD 310 (Solar Dawn, Australia, CLFR)
(14)      AUD 286 (Moree Solar Farm, Australia, single-axis PV)
(15)      EUR 381 (Lieberose, Germany, thin-film PV)
(16)      EUR 326 (Gemasolar, Spain, tower)

The Capacity Factor for Gemasolar is 110,000 / (19.9 × 24 × 365) = 0.63, which I think is the world’s highest CF for a solar power station.

To summarise, the cost per peak Watt for Gemasolar is high (indeed the highest I have analysed), but that is not surprising in view of the fact that it has 15 hours of thermal storage.  The Capacity Factor is excellent, approaching base-load, and the LEC is actually quite high compared to trough installations (also with storage) at Andasol and Ibersol. 

Moreover, at today’s exchange rates, I calculate the LEC for Gemasolar is around AUD 447/MWhr, or 44% more expensive than my estimate for Solar Dawn.  To conclude, I don’t agree with BZE’s contention that tower technology has been proved superior to CLFR technology as installed at Solar Dawn.

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