One of the Achilles' heals of the clean energy sector is its inability to produce large loads of electricity consistently - on sunny, cloudy or windless days.

While utility companies have grown their clean energy portfolio over the past few years, they have also maintained that coal or gas-fired power plants are the only ones that can produce enough electricity to meet current and future consumption on a consistent basis, whatever the weather patterns.

Utilities have a point. As is, wind or solar generation are not able to meet what's known as "baseload demand", which is the amount power utilities have to produce to meet the minimum electricity demand of the markets they serve. But that could change.

Now being constructed across the sun-drenched California desert and U.S. Southwest, are a string of large, utility-scale solar projects that once operational could each generate as much electricity as a natural gas power plant.

How do these plants work? The key is in two technologies. One known as Concentrating Solar Panels (CSPs) and another dubbed Concentrating Solar Thermals (CSTs).

Both solutions concentrate large amounts of solar lights into small areas of receptors, such as mirrors or photovoltaic cells, which enhances the amount of heat captured by each receptor. The process continues when the captured heat boils water, creating steam that powers electricity-generating turbines. That electricity is either distributed to consumers or, more importantly, stored, ensuring constant distribution rain or shine.

Today, more than 30 utility-scale solar power projects of one megawatt and higher are under development in the U.S. The Solar Electric Power Association (SEPA), estimates that combined, they could generate 5,500 megawatts of electricity.

Leading developers include eSolar and BrightSource Energy. Both companies are backed by Google and are developing projects mostly in California and the U.S. Southwest. Separately, Google has vowed to make serious investments in the clean energy sector, leading to speculation that after the Internet, cleantech could be the search engine giant's next focus.

Utilities set to buy power from these projects include San Francisco's Pacific Gas and Electric (PG&E), which plans to purchase more than 1,000 megawatts of solar-generated electricity from various projects: One is the 550 megawatt Topaz solar farm; the other is the 553 megawatt Solel project in the Mojave desert.

Another key development is the 280-megawatt facility developed by Abengoa Solar for Arizona Public Service. In New Jersey, Public Service Electric and Gas (PSE&G) is seeking regulatory approval to directly develop 120 megawatts of solar generation.

Back in California, Southern California Edison and Brightsource Energy have agreed to develop seven different projects that could generate 1,300 megawatts. The first of these plants, a 100-megawatt facility, could begin operating in 2013.

While impressive on paper, the big question in this bad economy is whether financing is available to even get these projects off the ground. After experiencing record growth, investments in the sector have ground to a halt, shut down by the credit freeze.

Utility-scale developer OptiSolar recently closed its two factories, cutting 200 jobs because it was unable to secure financing. A year ago the company grabbed headlines with its plan to build the 550-megawatt Topaz project for PG&E.  ....read more