Google Inc is closing in on its goal of producing renewable energy at a price cheaper than coal, the company's so-called green energy czar, the engineer in charge of the project, said on Tuesday.

The search company in late 2007 said it would invest in companies and do research of its own to produce affordable renewable energy -- at a price less than burning coal -- within a few years.

Green Energy Czar Bill Weihl said the odds of success had gone up in the last year or so from a long shot to a real possibility of demonstrating working technology in a few years.

It is even odds, more or less, I would say, he said in an interview with Reuters. In, you know, three years, we could have multiple megawatts of plants out there.

The company has made investments in advanced geothermal and wind, but engineers in the company are focused mostly on solar thermal, a type of solar energy in which the sun's energy is used to heat up a substance that produces steam to turn a turbine. Mirrors focus the sun's rays on the heated substance.

By contrast, photovoltaic solar cells, the most commonly known form of solar power, turn the sun's rays directly into electricity.

We are looking at ways of cheaply getting to much higher temperatures and also making the heliostats, the fields of mirrors that have to track the sun, reflect the sun, keep it focused on the target we are trying to heat up -- make those much, much cheaper. And I think we've made some really interesting progress in the last six to nine months, he said.

Weihl cautioned that the odds of missing the goal were still large, and he said that once the new ideas had been tried, it would cost substantial amounts to deploy them at utility scale.

Once the test project is done, We'll see whether we or us in combination with other people are prepared to fund much much bigger facilities, or if we want to get a few more years experience before we really start to scale it up, he said.

(Reporting by Peter Henderson; Editing by Nichola Groom, Gary Hill)