It’s been a bad year for solar power. Last year’s Solyndra scandal was one of the biggest public relations setbacks the industry has faced in years. And in recent months, more solar companies have been filing for bankruptcy, and even those that remained have had difficulty securing the government-provided loan guarantees they depend on.Now yet another solar dream is collapsing. Solar Trust of America LLC, which was planning to open an ambitious 1,000-megawatt solar field in Southern California, has declared bankruptcy after transmissions-rights agreements with local utility authorities fell through. The loss of these agreements rendered the project “near, if not completely, valueless,” according to the Wall Street Journal. The company’s other projects had likewise failed to generate revenue, leaving it to rely on infusions of cash from its owners.I was still in college when the first wave of solar power enthusiasts started selling the world on the vision of cheap, unlimited power from the benign and eco-friendly sun. It was a beautiful idea then and it still is one today. But then as now, there was one tiny little catch: for this beautiful dream to come true, governments needed to give solar companies a lot of money. It is more than 35 years since I first heard this beguiling promise: time enough for Jesus of Nazareth to be born, crucified and raised from the dead. It was time enough for the personal computer to take the world by storm and for the internet to come out of nowhere and change the way we all live. It was time enough for China to emerge from the shadows of the Cultural Revolution and the abyss of late Maoism and grow into a world class industrial power and to become by some measures the second largest economy in the world. It was time enough for the U.S. Marine Corps to accept openly gay marines. It was time enough for apartheid to give way to multiracial democracy in South Africa.And solar power is still a beautiful dream with just one tiny little catch.The prettiest unicorns have a way of dancing so tantalizingly, just out of reach.