Major U.S. market indexes on Thursday continued their week-long slide, but renewable energy stocks kept up their heady growth amid crude oil price volatility and investor concerns over climate change.

The solar sub-sector was the biggest winner on the day. Phoenix, Arizona-based First Solar muscled up 34.29 percent, to close at $224.43. Ningjin, Hebei Province-based JA Solar Holdings was also impressive, with a 15.70 percent gain, to end at $69.56.

Sector wide, the Nasdaq Clean Edge U.S. Index finished 14.19 points, or 2.39 percent, higher while its cousin the Nasdaq Clean Edge U.S. Liquid Series rose 16.07 points, or 4.46 percent.

That compares with a volatile Dow Jones Industrial Average that ended 33.73 points lower at 13,266.29 and the Nasdaq Composite Index that lost 52.79, or nearly 2 percent, at 2,696 by close of trading.

The clean indexes—each up more than 45 percent on the year—track the performance of major U.S.-listed clean energy companies.

“It’s not all related to oil prices, but there is an emotional connection people make,” said Clean Edge principle Ron Pernick, whose research and consulting firm launched the two clean-energy indexes in 2006.

“There is a psychological impact of watching oil approach $100 a barrel that is having an effect on companies in the clean-energy sector,” he said.

Mr. Pernick said fears of climate change and the need for technologies that reduce greenhouse gas emissions have also made clean energy companies more attractive to investors. Increased consumer demand for green products and an awareness that rising global energy demand requires more alternative fuel sources have contributed as well.

The global market for clean energy was worth $50 billion in 2006 and is projected to reach $220 billion by 2016, according to Clean Edge.

But Mr. Pernick cautioned that some of the growth in clean energy stocks, especially solar companies, is due to a misunderstanding of petroleum. While solar and wind technology is directed at electricity generation, most petroleum is used in the transportation and plastics industries.