Renewable energy is growing fast in California. The state has mandated 33% renewable energy by 2020. That's a long way to go and a short time to get there. Wind, solar, geothermal, big and small hydropower, tidal power, and wave power can probably get California to generate that much power by 2020. But that's just half of the problem. The power needs to be transmitted hundreds, sometimes thousands of miles. The grid needs to be kept in perfect balance too. Supply must always equal demand, never more, and never less.
Old school energy like coal, nuclear, and natural gas generally produce power from a few very large locations sending it on existing massive transmission lines to the destinations. Renewable energy works differently. The power is distributed, and it comes in smaller amounts from many locations. The transmission lines, especially for new installations, may not have even been built yet. Obviously they need to be, and there will be many of them, all intersecting with existing big transmission lines. You can begin to see where the problem is.
A big coal or nuclear plant can output 2-4 GW of power and do so steadily, assuming it has fuel. There are no renewable energy sources that are anywhere that size. There might be a few approaching 1 GW, but most are far smaller. Thus, the power is distributed over a far wider geographical location and comes from many more locations.
Compounding this is the variability of renewable energy production. A solar power plant can be producing at 100 KW then drop to nothing in seconds if a cloud passes in front of the sun. Wind power has the same problem, but the grid must always be in balance. That means it must be able to instantly find power elsewhere if, say, 500 GW of wind power suddenly stops in Altamont Pass. Big hydropower is in a category all by itself. California doesn't consider it to be renewable energy because of the changes it brings to the ecosystem. However, it too can generate power steadily.
These and other challenges were explored at the recent Verdexchange conference in Los Angeles where a panel discussed "Utility Scale Renewable Energy in California." The transmission problem is magnified by a ponderous regulatory process that can take years just to get permits to build a renewable energy facility. Unfortunately, many simply choose to build outside California. This of course makes for long transmission lines and bottlenecks, which simply complicates existing problems.
California is not alone here. Germany’s hugely ambitious plan to have 80% renewable by 2050 is currently threatened by a grid that is at its limit. It can’t handle any more power. Construction and permitting delays in upgrading the grid have become their “Achilles Heel.” Let’s hope California doesn’t soon have the same problems.