Concentrating (on) Utility-Scale Solar Energy

Last week, at the invitation of organizer Green Power Conferences, I attended their Solar Power Generation USA conference in Las Vegas.

Of course, there are innumerable events pertaining to the solar energy space, and each needs its own niche of differentiation.  This conference pertained solely to utility-scale solar power projects.  In other words, this is the remaining part of the solar industry when rooftop and off-grid installations are excluded.

“Focus” is a key word that describes this portion of the solar industry, because the two primary technologies for large-scale solar projects both employ lenses to concentrate sunlight to achieve lower costs per unit of energy produced.

Concentrating solar power (CSP) involves the use of lenses to focus sunlight on a vessel containing a liquid.  As the liquid is heated, it then drives a steam turbine to generate electricity.  At a conceptual level, this type of power generation has been used for decades in conventional utility powerplants fired by fossil fuels (coal, oil or natural gas), only with CSP the sun is being harnessed to provide the heat.

Concentrating photovoltaics (CPV) involves the use of lenses to focus sunlight on super high-efficiency PV cells.  In contrast to conventional PV modules, which have conversion efficiencies of less than 20% (i.e., less than 20% of the sun’s energy is converted into electricity), CPV enables conversion efficiencies approaching 40%.

Common to both technologies, a typical power project entails several modular installations spread over a sizable chunk of land — usually patches of desert — aggregating to tens or even hundreds of megawatts, with a common point of interconnection to the utility grid.  See, for example, the Ivanpah project of 392 megawatts being developed in California by BrightSource Energy.

The overall message was that CPV and CSP projects can be undertaken today, with power purchase agreements priced at 10 cents/kwh or lower.  A key theme expressed at the conference was the “bankability” of CSP and CPV — no doubt, to assure the risk-averse universe of bank financiers, utility off-takers, and project developers in the audience.   Although not necessarily household names for Americans, the involvement of such large publicly-traded (albeit European) corporations as Areva (Euronext: AREVA.PA), Acciona (BMAD: ANA), Abengoa (BMAD: ABG) and Soitec (Euronext:  SOIT.LN) should give comfort that adequate financial wherewithal stands behind CSP or CPV projects to support long-term warranties. 

Each of these concentrating solar technologies has its advantages and disadvantages.  CPV makes more sense than CSP where water is very expensive, because CPV doesn’t involve the steam cycle.  On the other hand, unlike CPV, CSP’s thermal inertia enables energy storage that can extend the power production period beyond solely the daylight hours, and also “rides through” passsing clouds with minimal power fluctuations, thereby reducing the need for CSP owners/operators to purchase ancillary services (e.g., voltage control, frequency regulation).  This tends to make CSP a higher-value power generation solution for grid operators than CPV.

In any event, CPV and CSP will not dominate the world.  They are only economically viable where direct normal irradiation (DNI) — known to the lay-person as clear sunlight — is very high.  Thus, CSP and CPV will not be ubiquitous, but rather a solution only in certain (typically sparsely-populated) parts of the world, and thus will remain only a minority segment of the solar industry, which will be dominated by conventional PV. 

Even so, it is possible to imagine these technologies being widely adopted in deserts in the decades to come — and there is a lot of desert footprint on this Earth.  That growth potential is why some of the big names listed above have been concentrating their attention on concentrating solar energy.

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