The sun is now California’s cheapest power source. This remarkable milestone in the changing energy economy, owed to advances in photovoltaic technology, comes as the curtains fall on the fossil fuel age. But a complete transition to renewable energy remains many years away. While California’s leaders have set progressive goals for reducing greenhouse gas emissions and tapping into clean energy, it will take bright minds in the private sector to reach and realize those targets. More than half a million Californians now work in jobs related to clean energy, and among several hubs of activity, the Capital Region has emerged as a center of action.