Despite the planned efforts, transmission remains to be one of the biggest factors affecting CSP in the western US.

Efforts to increase transmission capacity for renewable energy resources are moving forward in the West with California’s Renewable Energy Transmission Initiative (RETI) and the Western Governors Association’s Western Renewable Energy Zone Initiative. While no new transmission lines have been built yet as a result of these initiatives, the collaborative planning process appears hopeful, the Solar Energy Industries’ Association recently highlighted in its annual report.

Still, despite the planned efforts, transmission remains to be one of the biggest factors affecting CSP.

Last year, Charles Benjamin, Director, Nevada office, Western Resource Advocates, in an interview with CSPToday.com, mentioned that the State legislatures will have to take the initiatives to build new transmission lines by creating transmission authorities and/or mandating their public utility commissions to develop competitive renewable energy zones.

Recent efforts show mixed results

Assessing the situation after few months, Benjamin says the results have been mixed so far.

In New Mexico, the Renewable Energy Transmission Authority (RETA), which has a 30% renewable energy requirement, has promoted transmission lines that are as likely to carry as much or more coal-fired generation as renewable generation.

“Obviously, this is contrary to the direction we think the industry should be headed,” says Benjamin, who is scheduled to speak during the 3^rd Concentrated Solar Power Summit US, to be held in San Francisco on June 30 – July 1 this year

On the other hand, the Kansas Electric Transmission Authority (KETA), which was developed for renewable as well as non-renewable generation, has initiated new transmission lines that will be dedicated to wind energy because the proposed new coal plants for Kansas have been cancelled or denied permits.

In Texas, the development of competitive renewable energy zones has been critical to the installation of over 7,000 MW of wind energy so far and the state is well on its way to its goal of 10,000 MW.

The Nevada legislature is considering the creation of competitive renewable energy zones and the creation of an Energy Commission that would have powers equivalent to a transmission authority.

“It is clearly the intent of Nevada legislators that these entities are to focus on transmission for Nevada-based renewable energy projects for native load and for export to California,” shared Benjamin. In Nevada, new transmission is generally not needed to deliver CSP to Las Vegas loads because the best areas for CSP are very near Las Vegas.

In Arizona, utilities, regulators and solar power developers are working together to match up transmission needs with solar resources.

“There is great interest by the Arizona Public Service and by the Arizona Corporation Commission in making sure transmission is made available for CSP development,” said Benjamin.

In Colorado, the public utility commission, the utility and environmentalists and developers appear to be successfully working to develop needed transmission to bring renewable energy resources to load. In Texas, the competitive renewable energy zone process is bringing thousands of megawatts of wind energy to Texas load.

The basic issues with transmission integration

The deeper assessment of the situation signals that there are two basic issues with transmission integration – economic and electrical.

The difficulty depends on the nature of the facility. CSP with storage can probably integrate well with transmission both electrically and financially. Solar with no storage is more difficult.

Western Resource Advocates in November last year pointed out that as new transmission capacity is being planned for the West, most current schemes are being designed to connect to coal or natural gas generation. Insufficient care is being given to the areas through which power lines would be routed. The western landscape is strewn with a patchwork of private, state and federal lands that contain critical wildlife habitat, pristine areas and some of the nation’s most treasured vistas.

What is lacking is the capacity to carry renewable energy to consumers through the existing power grid.

Benjamin agrees and says getting solar power to an interconnection point is a big challenge.

Having sufficient capacity available to move the power once it gets to the grid is also a challenge.

The lower the capacity factor the more difficult it is because the lower the capacity factor the less energy is transmitted within a reserved capacity thus making the economics more challenging.

Many CSP plants will have thermal storage. Initial solar projects with thermal storage will have capacity factors around 40 to 45%. Later generations of CSP may have higher capacity factors. In addition, CSP has a 100% capacity credit and all of it can be counted toward meeting the peak load. Moreover, the transmission distances to major load factors such as Phoenix and Las Vegas are relatively short.

It is also pointed out that rather than rely on a few large transmission lines, electricity may be transmitted over an interconnected grid of smaller transmission lines. This means that electricity can always by-pass any part or parts of the network that may be damaged.

Assessing the same, Benjamin explained that transmission is currently designed to meet an N-1 contingency in which the system can withstand any single line going down without the curtailment of service. This is an appropriate standard.

However, when developers claim that two lines in a 100 mile corridor represent a single contingency, the result is an over abundance of corridors.

“Currently, there are corridors in the U.S. available to serve every load in the U.S,” he said, adding that new corridors can involve significant impacts to lands and other public resources.

“So, whenever possible, we believe that existing corridors, along with new conductor technology to enhance the carrying capacity of existing lines should be used first to move additional power,” said Benjamin.

It is felt that opening new corridors should be a last resort, and exception can be settig up new corridors only needed to bring new resources onto the grid.

(Other than Charles Benjamin, his colleagues from Western Resource Advocates also contributed in this article. The team included David Berry, Energy Project Senior Policy Advisor; Tom Darin, Transmission Attorney; Nancy Kelly, Senior Policy Advisor; and Steve Michel, Energy Program Chief Counsel).

3rd Concentrated Solar Power Summit US

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Contact: Sara Lloyd-Jones by email sara@csptoday.com

Related links: Transmission, RETI, SEIA