Back in 2011 Stanford professor Mark Jacobsen envisioned what that might require, and followed that up with an analysis of how to accomplish it in New York State. (Our coverage of that, by the way, was by far our most commented story in recent memory.) Now he's extended his analysis to all 50 U.S. states, laying out a resource roadmap to how each of them could meet 100 percent of their energy needs (electricity, transportation, heating) through renewable sources by 2050 — excluding nuclear, ethanol and other biofuels. Note that none of these calculations are geared to optimize for the least-cost mix to get to 100 percent renewables usage. Levelized electricity costs from that renewables mix by 2030 are projected to be 4-11 cents/kWh (including local transmission), compared with 20-25 cents/kWh from fossil-fuel energy with added health and climate costs.

His latest results include two more deep-dives as he did for New York, showing how they could achieve all new energy capacity powered by renewables (under the aforementioned definition) by 2020, 80-85 percent of existing energy converted by 2030, and 100 percent by 2050. California, he finds, can get to a 100-percent renewables footprint with the following portfolio: 55 percent solar (both distributed and large-scale, including a lot of CSP), 35 percent wind (both on- and offshore), 5 percent geothermal, and 4 percent hydroelectric, plus a big contribution from energy efficiency. (Blending wind with solar, and combining that with hydro and CSP with storage, will largely smooth out intermittency problems, he concludes.) Ultimately that will create a net 178,000 permanent jobs, avoid $131 billion in annual healthcare costs, and pay off the 631 GW of new installed power within six years.

In Washington State, Jacobson et al calculate a 2050 fully-renewables mix as: 43 percent wind, 28 percent solar PV, 26 percent hydro, 2 percent geothermal, and half a percent each of wave and tidal. New capacity additions of 137 GW would cost $228 billion but be paid off in 13 years. Note that Washington has an abundance of hydro power, and thus has a head-start for built-in storage to match up with energy demand; no new hydro will be necessary (more on that later) but he assumes existing hydro capacity will be updated to improve efficiency.

Change in percent distribution of California energy supply for all purposes (electricity, transportation, heating/cooling, industry) among conventional fuels and WWS energy over time based on the roadmap proposed. Credit: Stanford/Jacobson

Overall the methodologies were pretty much the same: "look at the footprints and areas, and how many devices of each type we would need," Jacobson explains. Compared to his previous calculations, these new findings extend the timeframe out to 2050, instead of just 2030. They're also more updated to account for current installations, such as an extensive wind energy buildout since his 2011 study, and the most recent insight into job creation.

He is also struck by the addition of mortality calculations, based on air quality data for each state spanning three years in every county, and illustrating how renewables will reduce air pollution and its direct connection to mortality. Around three percent of the U.S. GDP goes into health costs due to air pollution he says (quick math: the U.S. GDP is roughly $17 trillion, so that's $500 billion in health costs). Quantifying that at the state level with concrete numbers proves how renewable energy could address and reduce "a significant burden on society."

So which states have the smoothest pathway, relatively speaking, to achieving 100 percent renewables? The key, he says, is tapping and improving existing large-scale hydro, without adding any new ones. "Any state with hydro is amenable to making this easier," he says. Washington State would lead this pack due to its abundant hydro resources — up to 30 percent of what they'd need — plus a small but growing amount of wind and solar. He also notes the state has policies and leadership that are "very supportive of changing things." Other states that could best leverage hydro include Idaho and New York. The growing influence of wind energy in some states (Iowa, South Dakota) will help, too.

On the other hand, it won't be as easy a journey in the southeastern states, which have fewer renewables to tap into and must rely more on interconnection. (Note that his estimates don't restrict states from obtaining renewables outside their borders; this brings things like Canadian hydro into play for some northern states, as well.)

Maybe the biggest takeaway from Jacobson's updates is that broadly speaking none of it is new. "We don't have to invent a new technology to get this to work," he says. "We have to get more efficient from a cost point of view."

Lead image: Green US map, via Shutterstock

http://www.renewableenergyworld.com/rea/news/article/2014/02/powering-the-u-s-with-renewables-a-state-by-state-roadmap?cmpid=WNL-Wednesday-February26-2014