The DOE Contemplates The Dawn Of Global CSP


The sun rises over the monolith. Cue the Strauss.

In September, the Ivanpah Solar Electric Generating System produced its first output of energy when the Unit 1 station was synced to the power grid for the first time. Ranga Pitchumani, director of the concentrating solar power (CSP) program of the U.S. Department of Energy's (DOE) SunShot Initiative was there, and he was smiling.

Photovoltaic installations are setting records in both mature and emerging economies, in part because of their widespread availability and relatively low cost. The market has gone through an extended period of oversupply, to the chagrin of PV manufacturers in the West but largely to the delight of installers and developers of PV power plants.

Undaunted, the Solar Power And Chemical Energy Systems (SolarPACES) organization held its 2013 conference in Las Vegas as Ivanpah was ramping up its wattage. The group was formed under the aegis of the International Energy Agency to focus on the development and commercialization of CSP systems. The DOE's Pitchumani delivered the message to the 700 participants that CSP is the utility-scale solar power technology of the future that is taking shape today.
The size and complexity and comparative expense of CSP technology relative to PV will not count against it forever, advocates say. In fact, many countries relatively new to solar power are investing heavily in CSP technology. In particular, South Africa and Saudi Arabia are in various stages of planning and building utility-scale CSP installations – and CSP plants are, almost by definition, utility-scale.

Pitchumani believes this is a good thing, as CSP plants integrate naturally into electrical grids as they are currently deployed. Because CSP plants turn turbines, they produce AC current, which contributes to the grid in exactly the same way as conventional power plants with no need for inverters. This ability to plug into existing infrastructure is why CSP technology is so attractive in developing economies blessed with extensive solar resources.

Moreover, CSP plants can easily be co-located with conventional power stations in co-generation scenarios. CSP can pipe steam into conventional plants to improve their performance or to save on fossil fuel. They all drive the same turbines.

‘CSP is a synergistic technology,’ Pitchumani says. ‘When the sun is up and demand is high, CSP plants function at their best.’
Another defining characteristic of CSP plants is their ability to incorporate cost-effective thermal energy storage. The molten salt and related materials used to provide energy storage are able to continue heating fluids and boiling water to turn turbines, providing electricity long after the sun has set. Attractively, thermal energy storage is more cost-effective than other grid storage systems, such as batteries and flywheels.

‘Thermal energy storage and grid interaction are the two key reasons CSP is going to be a part of many countries' energy future,’ Pitchumani says.

For all its apparent advantages, CSP is not yet widespread in mainstream deployment. This is almost entirely a function of cost. In 2010, on average, electricity from CSP cost approximately $0.21/kWh in the U.S. without subsidies. Current numbers are reported as low as $0.13/kWh. SunShot's goal for CSP is to get it down to about $0.06/kWh without incentives.

A study conducted by the Renewable and Appropriate Energy Laboratory (RAEL) at the University of California, Berkeley, says this target would indeed make solar power mainstream in the western U.S. If such a target could be achieved, the RAEL says, then utility-scale solar power would account for about a third of all power generated in the western region of North America by 2050. On the other hand, the RAEL study does not specify the practical measures required to meet the goal.

Pitchumani says organizations such as SolarPACES and its members are working steadily to define those practical measures and put them into action. One avenue of cost reduction is achieved through experience in planning, developing, building and operating grid-connected CSP plants. Pitchumani says this is why the success of those plants nearing completion is so important, and why he took a break from the Las Vegas conference to visit the Ivanpah CSP facility for its first grid interconnection test.

‘Looking at a plant in operation gives the technology much more credibility,’ he says. ‘I think the data from the plants now entering service will lead to future development.’

However, over and above operational experience, Pitchumani says there is an extremely important role for technology development in the future of CSP. For example, the solar field of heliostats currently accounts for about 45% of the cost of a CSP facility. There is room for improvement in manufacturing and finishing the mirror collectors through industrial automation.

Also, the oil-based fluids typically used to transfer the heat to the boilers to produce steam are limited to temperatures of under 750 degrees F. Pitchumani says improved fluids could be used to achieve higher temperatures and thus greater efficiency in the power block, which now have conversion efficiencies of about 35% to 42%. High temperature fluids that can sustain 1,200 degrees F will enable the development of power blocks that use air-cooling, eliminating the consumption of water by while achieving efficiencies of 50% or more.

At the end of the day, Pitchumani is extremely optimistic that the SunShot's targets can not only be met but that they can be replicated throughout the world.

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