At least two of the four energy companies profiled in Yale’s 2009 annual investment report are struggling.

Suntech Power Holdings Co. — once the world’s largest supplier of solar panels — announced Thursday that its main subsidiary in Wuxi, China, was declaring bankruptcy. A day later, Mascoma Corporation, a cellulosic ethanol technologies company, withdrew its long-planned initial public offering, or IPO, citing “market conditions.” These two companies — along with Silver Spring Networks, which develops network applications enabling utilities to manage their electricity grids, and HT Blade, a wind power company — were profiled in two three-page spreads on promising green ventures and investments in the 2009 annual Yale Investments Office report.

Though it is unclear whether Yale still invests in these companies because the Investments Office does not disclose its holdings, experts interviewed said predicting which companies will come out on top is particularly difficult in the energy sector because of capricious changes in public policy, noting that these companies may eventually overcome their current setbacks. Chief Investment Officer David Swensen declined to comment for this article.

“There are many fine investments in the energy sector, but there is an added level of risk, namely policy risk, that is not present in many markets,” said Christopher Knittel, a professor of energy economics at the Massachusetts Institute of Technology, in a Monday email, adding that this increased risk can sometimes result in better returns. “Investors in companies like these should expect to see more frequent negative investments that are offset with less-frequent, but larger, positive investments.”

In Yale’s 2009 report, the Investments Office described Suntech’s dominant role in the solar power industry, along with its rise to prominence in the 2000s, and noted potential challenges to the industry, but also cited Suntech CEO Shi Zhengrong’s confidence in the company’s long-run market position.

Suntech’s stock prices peaked at $85.16 in December 2007 before proceeding to drop precipitously during the financial downturn, with shares valued at $0.45 as of Monday. Experts said the company, though commended in the 2009 Yale report for its “culture of cost consciousness and innovation,” has suffered because of oversupply in the market for solar panels.

When prices for solar panels were high, many solar companies built up their production capacity with the help of large government subsidies, said Michael Giberson, a professor of energy economics at Texas Tech University, adding that the resulting glut in the solar industry is now driving prices down.

Suntech must also wrestle with large fixed costs for its production facilities and with import duties the U.S. placed on Chinese panels, which have given an advantage to panels constructed in places like Taiwan, said Kenneth Gillingham, an economics professor at the Yale School of Forestry & Environmental Studies, in a Monday email.

Recent policy changes, such as the expiration of ethanol subsidies in November 2012 and the recent renewal of the production tax credit for wind power, have strongly influenced the profitability of energy companies in these industries, Knittel said.

The alternative energy sector is also grappling with the market effects of hydraulic fracturing, or fracking, which is a technique used to extract natural gas that gained widespread use and media attention over the past decade, experts said.

“Fracking has opened up the supply of natural gas, which has put downward pressure on electricity prices,” Gillingham said. “With relatively lower electricity prices, alternative energy is less attractive.”

Mascoma, the company that withdrew its long-planned IPO of up to $100 million last week, is the fourth prominent biofuel company to delay or cancel an IPO since last year.

Knittel said the elimination of the ethanol subsidy likely had a negative impact on Mascoma, adding that companies like Mascoma will struggle to be profitable unless policies are implemented that either indirectly or directly subsidize the expensive technologies needed for cellulosic ethanol production.

If the Yale Investments Office is still invested in Mascoma, it is likely because the officers see the company as a “long-run investment,” Gillingham said.

However, the other two companies profiled in the 2009 report appear to be doing well. Though the wind power company HT Blade remains privately owned and does not release public records as a result, Silver Spring Networks, a developer of smart grids, successfully completed its IPO last week, raising $81 million. The IPO was considerably smaller than the $150 million offering for which Silver Spring had originally hoped, and Silver Spring has yet to turn a profit since its founding in 2002, but experts said the company’s successful IPO suggests that investors have confidence in its future.

Suntech declined to comment for this article, and Silver Spring did not respond to requests for comment.