A recent state sponsored study shows that California could reduce its greenhouse gas emissions 60% compared to 1990 by 2050 with today’s technology(pdf). That has sparked a debate. The glass-half-full crowd, among whom I usually count myself would argue that if we have the technology today to achieve a 60% reduction, if we start implementing now, normal technological progress will take care of the rest. The glass half-empty crowd say that 60% means it is hopeless to do anything now, that we should wait for breakthroughs before doing anything.
I find myself in the glass is 100% full crowd. Well, “crowd” is not exactly the word. Because this study by some of the nations leading experts got the technology wrong, and greatly underestimated potential savings. No, the experts were not stupid, not short-sighted, not missing the obvious. They gave a good set of answers to question they were asked. It is not even the fault of those doing the asking. The study was done for the state of California. That made the sensible question: what technologies available today or in the near future can the state of California deploy to reduce greenhouse emissions? Unfortunately, that question meant that technologies existing today but mostly needing deployment on a national scale were excluded from the study.
One example: the study looked at both nuclear and renewable electricity and found that either (or both combined) still need a lot of natural gas as supplementation. Renewable electricity requires natural gas when the sun is not shining and the wind is not blowing. Nuclear power provides mainly baseload electricity and needs supplementation when demand exceeds baseload. The study included good reasons biomass did not help in this respect. What the study could not consider, because it confined itself to California, was long distance transmission that connected California to far-away states. There is wind available in the Midwest when it is not blowing in California, and sun available in California when the wind is not blowing in the Midwest. Both regions would have more reliable renewable energy if they were connected by high capacity long distance transmission. And while I remain an opponent of increased use of nuclear electricity, the same connection would increase baseload as a percent of demand, which would reduce the need for natural gas backup for nuclear plants as well. High Voltage Direct Current transmission has been a mature technology for at least half a century, but the study as defined could not consider its possible role in reducing emissions from backup for a renewable or nuclear grid.
Long distance transmission in the context of a renewable grid also means most of the time backup is needed is for very short periods(paywall), less than two hours of peak generation, mostly less than a half hour. Utility scale batteries can handle storage at that level today. In addition, because the gas generators would be run fewer total hours than the study scenario, concentrated over more hours at one time, it would be possible to use new generation commercially available combined cycle turbines that start up with 15 minutes as single cycle turbines, but bring the second cycle on-line within 45 minutes. The overall efficiency with which natural gas was burned could be well above the ~one third estimated by the study. Thus, short term storage combined with natural gas backup could result in far fewer emissions over a long distance than in one state.
One other possibility the study seems to have overlooked that could be done in one state: curtailment. If low carbon electricity is built with capacity greater than the peak needed, then even in low wind and sun conditions it can provide more electricity. The excess can simply be discarded during high sun or wind conditions. The same thing can be done with nuclear generation. In the U.S., nuclear plants average well above 90% of peak capacity. French nukes run at about 70% of peak capacity. This raises their capital costs, but the tradeoff is that nuclear power can provide a much higher percent of total generation there than here. (For those who wondering if I’ve suddenly become pro-nuclear: no. I’m just pointing out the limitations of this study underestimate the potential of nuclear generation as well as of solar and wind.)
Electricity generation is only one area where the one-state focus underestimates potential reductions. Another is in heavy vehicle transport. It rightly points out that while short-haul trucking might be electrified (though even there it is more difficult than with passenger vehicles), electrifying long haul trucking is close to hopeless. But there is another possibility: Alan Drake has been pointing out for years that if we electrify freight rail (which the study advocates) and also make other improvements to freight rail, including double tracking along the most heavily used routes, signal upgrades, more switchyards, more freightyards, bottleneck removal and so on, we could switch about 85% of long-haul truck freight to rail(pdf). We would still use trucks to move freight to the rail system and from the rail system, and for short haul needs. Because electric freight trains could move at about 110 mph, if we upgrade rail reliability at the same time, end-to-end delivery time would remain the same or even drop compared to truck-only today. But, upgrading a rail system in only one state limits how useful the upgrade is. Freight sent from or to other states is still hitting all the non-California bottlenecks. To upgrade freight rail properly would require about a trillion dollar investment at a national level. An examination of the money spent annually on long haul trucking will show that is an investment that can pay for itself easily at the national level, but probably not in California alone. A similar case could be made for high speed passenger rail as replacement for much air traffic.
Now again, this is not a criticism of the experts who compiled the report. They answered the question they were asked, and in spite of my quibble about curtailment came as close to an accurate answer as humanly possible. Nor is this a critique of state officials who commissioned the report. Concentrating on issues they have power to affect is their job. But it is a critique of anyone who looks at this report and says “well, 60% is the upper limit of the greenhouse gas reduction that could be made in California with today’s technology.” Because the study does not examine the limits of what is technologically possible to reduce emissions in California. It studies the technological limits of what California could do on its own to reduce emissions, rather than as part of a national effort.