During his first two terms nearly four decades ago, Jerry Brown became famously known as Governor Moonbeam. Now he seems destined to become Governor Sunbeam.

With the epic battle over the state budget finally behind him, Brown’s first major policy initiative aims to fulfill the ambitious goal laid out in his campaign: to develop a clean-energy economy in California.

Brown wants the state to produce 20,000 new megawatts of renewable electricity — enough to power 20 cities the size of San Francisco and roughly one-third of the state’s current peak use — by 2020. That would nearly triple the amount of electricity that California currently gets from renewable sources.

The plan includes the fast-tracking of large, utility-scale renewable power plants. But 12,000 megawatts are to come from “localized electricity,” small systems located close to where energy is consumed that don’t require new transmission lines. A variety of technologies, from biogas to wind, will play a role. But solar panels — on the roofs of commercial buildings and along the banks of state highways — will be a dominant element.

“The future of energy is not Texas oil,” Brown said last month at the groundbreaking for the Blythe Solar Power Project, a massive solar power plant under construction in Riverside County. “It’s California sun.”

Richard Caperton, an energy policy analyst with the Center for American Progress, said the scale of Brown’s energy ambitions are unprecedented. “Doing it statewide, at this level, is unheard of,” he said. “This is the sort of goal that countries in Europe and Asia are operating with.”

But some business interests are worried about the potential costs of this plan. Gino DiCaro of the California Manufacturers and Technology Association said he is concerned that Brown is promoting clean technology at the expense of other parts of the economy. “Manufacturers are worried that this is going to further drive up electricity costs, and industrial electricity rates are already 50 percent higher here than in the rest of the country,” he said.

To get things rolling, Brown’s office has summoned top energy experts to UCLA for a two-day conference starting Monday to hash out the thorny details. At least 250 people are expected at the invitation-only event.

Among the big issues: How will renewables be integrated into the existing electric grid? How will the projects be financed? What kind of workforce training is needed to make sure jobs are created across the state?

“The history of renewable energy policy is boom and bust, and we’re trying to get out of that cycle and create a long-term plan,” said Matt Freedman, an attorney for the consumer advocacy group TURN, who is participating in the conference. “It’s clear to me that Governor Brown cares a lot about moving the ball forward, and he wants to debate the issues.”

One of the most formidable issues is cost.

“The goal of 12,000 megawatts (of localized electricity) is desirable and achievable,” said Mike Peevey, president of the California Public Utilities Commission. “The challenge will be to meet the goal in a cost-effective manner, without an undue burden being placed on consumers.”

Brown kicks off the conference with a panel discussion featuring David Crane, the CEO of NRG Energy, Rick Needham, Google’s (GOOG) director of green business operations and Lyndon Rive, CEO of SolarCity.

Michael Picker, one of Brown’s top energy advisers, stresses that the 12,000 megawatt goal won’t rely only on solar. Dairy farmers in the Central Valley, for example, could install so-called anaerobic digesters to turn cow manure into biogas.

“It’s very unlikely that you are going to have an anaerobic digester in your backyard, but it’s a way that a waste product can create energy and reduce air pollution at the same time,” Picker said.

Though renewable energy comes in many forms, Brown’s focus has been on harnessing energy from the sun. His first event after winning the Democratic primary in June 2010 was held at Solaria, a Fremont solar manufacturer. In April, he chose SunPower’s (SPWRA) Milpitas factory as the backdrop for signing the most ambitious clean energy standard in the nation, which requires one-third of the state’s electricity to come from renewable sources by 2020.

During his first stints as governor, from 1975 to 1983, Brown signed the first-ever tax incentive for rooftop solar and warned that oil and gas were finite resources.

“It is essential that this state invest in the future by insuring new energy supplies,” Brown said in his 1978 State of the State address. “I propose that substantial sums of state funds be invested in developing new technologies that will provide energy from coal gasification, geothermal, solar and biomass conversion.”

“Jerry was way ahead of his time on all things alternative, and he’s always been ambitious,” said Barbara O’Connor, director emeritus of the Institute for the Study of Politics and Media at Sacramento State. “He also plans ahead.”

Contact Dana Hull at 408-920-2706. Follow her on Twitter at Twitter.com/danahull.