By Sam Phipps

BrightSource Energy’s 500MW Rio Mesa complex in California might be nearing approval but a host of economic and permitting variables makes it hard to predict whether that project will turn out to be an industry landmark as well as a physical one.

After an 11-month examination of the scheme, the California Energy Commission (CEC) signalled in late September in its preliminary assessment that environmental and wildlife impacts could be offset with mitigation. Later, the California Public Utilities Commission (CPUC) also gave the green light for the contract with Southern California Edison (SCE).

A final staff assessment by the CEC will follow, then formal hearings and an eventual decision.
If Rio Mesa goes ahead, as seems likely, its solar receivers atop two power towers will generate enough electricity to serve more than 200,000 homes in California during the peak hours of the day and cut carbon emissions by almost 13 million tonnes over its planned 25-year life cycle, according to BrightSource.

The project, based on about 4,000 acres of mostly privately owned land in Riverside County, would reduce land use by at least 33% compared with both a typical photovoltaic farm and parabolic trough solar thermal plant, as well as create more than 2,000 jobs during construction. It would be due for completion by 2016.

The company is already involved in the building of the biggest solar thermal power tower system in the world to date, the $2.2bn Ivanpah complex, also in California, on federal land managed by the Bureau of Land Management. Owned by NRG Energy, Google and BrightSource, the last of three units there will be ready next year and the combined base will power more than 140,000 homes.

Two other BrightSource CSP schemes, Sonoran West and Siberia, which would employ molten salt energy storage systems that continue generating electricity after sunset, are also awaiting environmental reviews by the CEC. Siberia has drawn objections from the Department of Defense, which alleges that rising heat from the project would affect pilots’ use of infrared viewers during night-time operations from a nearby training base.

Financial concerns

However, a bigger hurdle to future CSP development in the States is more likely to be financial, namely that the loan guarantee programme has ended. This granted about $4.2bn for a total of five CSP projects, with combined capacity of 1312MW.

BrightSource declined to comment on funding arrangements for Rio Mesa and its other CSP schemes but Jennifer Rigley, a spokeswoman for the company, said: “Worldwide CSP growth is being fuelled by the growing recognition by utilities and grid operators of the need for power at scale that is both renewable and reliable.

“As more intermittent renewables come online, this demand only grows. We’re seeing this today in US states, like California, that have high renewable mandates. CSP is uniquely qualified to a meet a utility’s cost-effective and reliable power needs at a meaningful scale.”

However, power purchase agreements with utilities will only be granted if they are deemed to represent fair value, raising the question of how much subsidy will be needed to make the likes of CSP viable. Questions surrounding the continuation Investment Tax Credits look to be announced in early 2013. 

The Large Scale Solar Association, which represents the sector, responds that technological advances and economies of scale will bring electricity prices down as the industry develops.

Failing that, another argument cited by some supporters of CSP is simply that it is worth paying more in order to cut carbon emissions drastically and tackle climate change.

Integrating Storage

Storage is increasingly becoming part of the requirements for new CSP plants. As mentioned above the Siberia and Sonoran West projects proposed by BrightSource will both be using molten salt storage. CSP plants that are integrated with thermal energy storage (TES) can offer significant benefits over other forms of renewable energy, including photovoltaic, according to a report by the National Renewable Energy Laboratory (NREL), published on November 30.

NREL described the implementation of CSP in a commercial production cost model, with results for grid operations with CSP in a test system consisting of two balancing areas located primary in Colorado.

Incremental operational value of TES was about $6.6 per megawatt hour (MWh) over and above that of a plant without TES, assuming a scenario of low overall market penetration of renewable energy (13%) by 2020.

With high renewable penetration (34%), the difference grew to $16.7/MWh as the cost of midday generation was reduced. Also, the capacity value of CSP systems with TES remained high in this scenario, bringing total value, including operational and capacity, up to a maximum of $35.8/MWh over PV systems.

Power boost

Last month’s re-election of President Obama for a further four years is also seen as positive for the industry. A few days before the vote, the Obama administration announced a programme to spur development of solar energy on public lands in six western states.

The Programmatic Environmental Impact Statement (PEIS) provides a blueprint for utility scale permitting in Arizona, California, Colorado, Nevada, New Mexico and Utah. It does so by establishing solar energy zones with access to existing or planned transmission, incentives for development and a process by which to consider extra zones and solar projects.

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