Across the US, dozens of cities and states have passed laws or resolutions targeting 100 percent carbon-free electricity — most recently 20 communities in Utah and the state of Virginia. But is it even possible to power a modern economy with a carbon-free grid? And if so, what are the best energy sources and technologies for getting there? These questions have been the source of raging debate among energy wonks for many years but have moved closer to mainstream political discourse since the introduction of the Green New Deal. (For a brief introduction to the terms and players involved in the debate over 100 percent clean electricity, see here and here.) Now there is a growing list of jurisdictions that face stringent emissions targets in years ahead and urgently need to figure out answers. We’ll discuss the most notable such jurisdiction, California, and a cool new(ish) technology that it may help it reach its 100 percent target, in a moment. First, though, let’s look at the problem to be solved, the dilemma that comes with an energy grid run mostly on renewable sources of energy. The core issue is variability. Whereas fossil fuel power plants can be turned up or down to meet demand (they are “dispatchable,” in the lingo), the big sources of renewable energy — sun, wind, and water (hydropower) — cannot. They come and go on nature’s schedule. Sun disappears each night and on cloudy days. Wind and precipitation vary daily and seasonally. All three show longer-term variations over years and decades. All these variations in supply cannot be controlled by power grid managers, so they must be accommodated. To some extent, sun, wind, and water balance one another out; where it is not sunny, it is often windy. With a good national transmission system, renewables could supply up to 60, maybe 80 percent of electricity in the US, but after that, things get expensive and something else is needed to fill the gaps. Is there a carbon-free way to fill the gaps? This is where the debate comes in. Some renewable energy advocates argue that the gaps can be filled with energy storage, what at least at the moment mainly means batteries. But getting to 100 means covering for any foreseeable seasonal or even decadal dip in renewable sources, which means a lot of batteries. Without some other, cheaper form of energy storage, which can hold more energy for longer, that gets expensive. Some people take this to mean that 100 percent clean electricity can’t be done. Some use it to argue that small nuclear plants will be necessary. Some argue that coal or natural gas plants should stay online, with their emissions captured and buried, or that biomass electricity generation (which can conceivably be carbon-negative) should scale up. And that’s where the debate typically gets stuck. But there’s a new(ish) energy technology on the scene these days that promises a neat and satisfying resolution to the variability dilemma. It’s called power-to-gas, or PtG. A new study argues that PtG could help California, and by implication other jurisdictions aiming for clean grids, reach ambitious clean energy targets without spiking electricity costs. If that’s true — and to some extent, whether it is true depends on policy choices made in coming years — it could make the 100 percent target safer, luring other jurisdictions to jump on board.
Vox 28th March 2020 read more »