The government must swiftly begin spending $83 billion in the stimulus law for cleantech, or recent growth in the sector will quickly turn into bankruptcies, according to a study released on Tuesday.

Urgency surrounds numerous cleantech companies, said the report by PriceWaterhouseCoopers on the progress of venture-backed alternative energy companies.

Cleantech, or the use of technology to improve productivity while reducing costs and energy consumption, is a focus of President Barack Obama's new administration. Obama has said that stimulus money is needed for cleantech to address climate change and to create jobs.

Money must start flowing for cleantech from the $787 billion stimulus bill by July to avert a raft of potential bankruptcies or crippling retrenchments through 2009, the report said.

The capital and exit markets are shut down, said Tim Carey, U.S. cleantech leader for the PriceWaterhouseCoopers. The exit market means selling off start-up companies to other firms, or taking them public.

He said companies that had planned to ramp up instead found themselves on the sidelines, unable to take the next step.

The PriceWaterhouseCoopers report said venture capitalists have increased their investment in cleantech by 1500 percent in recent years, from $271 million in 2003 to $4.1 billion in 2008.

Solar energy, at $1.8 billion last year, has been the biggest beneficiary of the increase in venture money. That outstripped investments in alternative fuels at $639 million, pollution and recycling at $436 million, transport at $142 million and wind and geothermal at $117 million, the report said.

The number of deals involving alternative energy last year exceeded those in past years. There were a record 180 deals, led by 53 in solar.

The recession has meant venture capitalists have had a far more difficult time selling companies they develop to other companies or making initial public offerings, the report said.

But at least last year, the study found that venture capitalists had invested in 180 new projects, led by solar.

The top four venture-backed firms named in the report are all solar companies: Nanosolar at $300 million, Solyandra at $219 million, SolarReserve at $140 million and OptiSolar at $132 million.

(Reporting by David Lawsky, editing by Matthew Lewis)

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