Renewable Energy Archive

Community Solar: Ellensburg, Washington Gets It Just Right

Thursday, May 2nd, 2013

The Ellensburg, Washington’s publicly owned solar utility is one of  many community solar models we’ll discuss in upcoming articles. (This article was originally published a “Your Ecological House” syndicated newspaper column.) 


The city of Ellensburg owns its community solar utility… citizens gather to learn how the system works (photo: City of Ellensburg)

The city of Ellensburg owns its community solar utility…
citizens gather to learn how the system works (photo: City of Ellensburg)


Why don’t we just get the renewable-energy revolution over with and build one giant solar plant in Missouri to power the whole country?

Just think of the economy of scale. Bigger is better, right? “SolarCorp USA” would take care of everyone’s power needs at the lowest possible rates. Until it didn’t; until there was a cloudy week in Missouri or the transmission line to New York went down in a superstorm.

OK. Maybe a giant, centralized power company isn’t the way to go. Lots of environmentalists tout the advantages of distributed power generation, preferably with all the energy producers hooked up to a “smart grid” that can properly distribute the variable, intermittent input from thousands or millions of sources — a version of the “million solar roofs” scenario that Bill Clinton and Al Gore were promoting in the 1990s.

I had my doubts about the efficacy of that approach even then. Solar, yes. You can’t beat a free, limitless, nonpolluting source of energy. But a million solar roofs? Or, closer to 120 million, since that’s how many houses there are in the U.S. Where’s the economy of scale in that?

There are other problems with the plan. The National Renewable Energy Lab has determined that only 22 to 27 percent of U.S. houses have proper solar access and orientation. Then there is the enormous redundancy of the millions upon millions of circuit-breaker boxes and meters needed for the individual residential or small-building systems — their embodied energy adds up. Finally, there’s the cost: even with the renewable energy credits (RECs) — tax credits and the like — designed to lessen the burden, residential solar systems simply cost more than a lot of people can afford. (Also, RECs seem to have an ephemeral life of their own, coming and going with the political winds.)

Having pondered these problems of scale for decades, I was excited when I learned that the city of Ellensburg, Washington, has built a community solar system. At last, somebody has gotten the scale — and a great deal more — just right. And although there are many approaches to developing “community solar” which we’ll explore in subsequent columns, I must confess that Ellensburg’s model — purportedly the first community solar system in the country — remains my favorite.

The city of Ellensburg owns its photovoltaic system, which sits on an optimum solar site in a city park. (A cooperative ownership model would work too, so long as the physical system is locally owned by citizens.) Savings and system control remain in the hands of the people.

The system’s economy of scale reduces upfront costs and investment risks compared to those of individual residential systems. Overall maintenance costs of the consolidated system are lower than the cumulative costs of maintaining multiple residential systems. Meanwhile the continuous expansion of the system, as more citizen investors opt in, creates good, local construction, maintenance and service jobs.

As a community project and source of pride, the system brings the town together — without regard to wealth or even homeowner status. Anyone, even renters, can (and do) buy a “part of a solar panel” — actually, a certain amount of electricity — for as little as $250. Wealthier people or institutions can buy as many “solar panels” as they can use.

The payback for your investment in a community solar system usually comes as a credit on your utility bill for the proportion of your electricity that was produced by the portion of the solar system you own. That is, for now at least, Ellensburg and most other “community solar cities” get most of their electricity from conventional sources, but the community solar system reduces that supply and credits the reduction to its owners. The system can also remunerate its owners with RECs which can vary in value and type depending on the particular regulations that apply.

But there are other paybacks. Building a community solar system can educate your community, from pre-schoolers to MBAs, about where energy comes from. There is peace of mind: properly wired, the system could keep essential services such as hospitals operating during a regional blackout. And there’s the knowledge that your community is taking a step toward a sustainable future at your ecological house.

Concentrated Solar Power Generates Electricity 24/7!

Saturday, April 28th, 2012
Gemasolar concentrated solar power plant near Seville, Spain

Gemasolar concentrated solar power plant near Seville, Spain (Image courtesy of Terresol Energy, reproduced by permission.)

The receiver sits atop a slender column, 40 stories above the desert floor. It glows like a giant, white-hot torch in the clear blue sky as it gathers limitless free energy from outer space. The energy is converted first into heat, and then into electricity which is transmitted hundreds of miles across the earth — almost at the speed of light.

At the base of the column a small team of earthlings performs low-cost, routine maintenance tasks. Occasionally they look up at the receiver and marvel at its simplicity, its efficiency, its beauty. They chat about how it will render obsolete polluting, fuel-based electricity production from coal, oil, gas and uranium.

This could be a scene from a futuristic science fiction movie, but it’s not. It’s a description of Gemasolar, the world’s first commercial electricty facility driven by concentrated solar power (CSP) and equipped with a central tower receiver and a molten-salt thermal storage system. The plant was completed and brought online in 2011.

Located in southern Spain’s “sun belt,” the Gemasolar plant generates 19.9 megawatts of electricity, enough to power 25,000 homes. But that’s not the big news, since other solar-power plants have similar capacities. What makes Gemasolar a game changer is that it continues to produce a steady stream of electricity after the sun goes down — and until the sun comes up the next morning, reenergizing the system.

Here’s how it works. Gemasolar’s central tower is surrounded by a circular array of 2,650 “heliostats” (mirrors) that focus the sun’s rays on the receiver. Pipes inside the receiver are filled with common salts which melt in the intense, 900-degree heat. The molten salts are circulated through a heat exchanger where some of the heat is used to boil water which in turn drives a steam turbine that generates electricity. The salts, in a closed loop, are then returned to the tower for reheating.

But more salt is heated than is needed to drive the steam turbine, and the excess hot salt is stored in tanks and used to generate steam for up to 15 hours after the sun wanes and sets.

Concentrated Solar Power Changes the Energy Game

That’s a game changer because the big drawback of solar electricity has been its inability to provide “baseload” power, keeping up with demand as the sun begins to set and people return home from work and turn on their air conditioners and TVs and cook dinner. That’s when conventional power, mostly provided by coal-fired or nuclear power plants, comes on — and stays on until the next day.

But with Gemasol leading the way, reliable baseload CSP plants are beginning to crop up all over: in the American Southwest, Israel and, most important from a worldwide energy perspective, in Morocco and Tunisia.

Enter Desertec, the non-profit foundation working toward developing “power tower” concentrated solar power plants in the world’s desert latitudes, and transmitting the electricity wherever it’s needed.

The brainchild of a German nuclear engineer who, after the Chernobyl nuclear accident, decided that we must find a clean source of energy, Desertec has assembled an international consortium of investors and developers using three selling points: (1) concentrated solar power with molten-salt storage works, (2) enough sunlight strikes the world’s deserts in six hours to power human civilization for one year, and (3) high-tension power lines can transmit electricity more than 1500 miles with minimal power loss (about 10 percent).

Based on studies by the German Aerospace Center — and backed by investments from heavy hitters such as Deutsche Bank and Siemens and the governments of Germany, France, Italy, Spain, Morocco and Tunisia — Desertec’s pilot project involves building concentrated solar power plants in North Africa. The electricity will energize the host countries and transmit a portion of the power to Europe where it will enter a developing European super-smartgrid providing baseload backup for local wind and solar installations.

One plant is already under construction in Morocco and, in 2014, a larger plant that will produce as much electricity as two average-sized nuclear power plants will be built in Tunisia. Among the byproducts of the development: creating hundreds of thousands of jobs and cutting million of tons or CO2 emissions.

CSP is already coming to America and, who knows? The day may soon come when you can turn on the lights without causing global warming at your ecological house.


Note: A version of this article originally appeared in the syndicated newspaper column Your Ecological House, by Philip S. Wenz, in March, 2012.


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Editor’s Note:

Ecotecture normally recommends books or other reading materials so supplement its articles. However, we could find no reliable references on the subject of concentrated solar power, perhaps because the field is so new or is a sub-field of general solar engineering. Available books with the words “concentrated solar power” in their title ranged from collections of wikipedia articles to surveys by authors with no apparent qualifications.

The exception is an engineering textbook which is highly recommend by a number of reviewers and is described as a good introduction to solar technology in general (see below).  If you find a good book for the general reader on the concentrated solar power, please let us know so we can bring it to the attention of our readers.

Solar Engineering of Thermal Processes, Duffle and Beckman