Intermittent energy source: Difference between revisions

Revision as of 21:04, 28 November 2017

Revision as of 21:11, 28 November 2017

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===Nuclear power===

Several authors have said that no energy resource is totally reliable. [[Amory Lovins]] says that nuclear power plants are [[intermittent power source|intermittent]] in that they will sometimes fail unexpectedly, often for long periods of time.<ref name=al2009>{{cite web|first=Amory |last=Lovins |author2=Imran Sheikh |author3=Alex Markevich |date=2009 |url=http://www.rmi.org/rmi/Library/E09-01_NuclearPowerClimateFixOrFolly |title=Nuclear Power:Climate Fix or Folly |publisher=[[Rocky Mountain Institute]] |page=10 |quote=All sources of electricity sometimes fail, differing only in how predictably, why, how often, how much, and for how long. Even the most reliable giant power plants are intermittent: they fail un-expectedly in billion-watt chunks, often for long periods. |accessdate=20 Oct 2012 |deadurl=yes |archiveurl=https://web.archive.org/web/20110927101054/http://www.rmi.org/rmi/Library/E09-01_NuclearPowerClimateFixOrFolly |archivedate=2011-09-27 |df= }}</ref> For example, in the United States, 132 nuclear plants were built, and 21% were permanently and prematurely closed due to reliability or cost problems, while another 27% have at least once completely failed for a year or more. The remaining U.S. nuclear plants produce approximately 90% of their full-time full-load potential, but even they must shut down (on average) for 39 days every 17 months for scheduled refueling and maintenance.<ref name=al2009 /> To cope with such intermittence by nuclear (and centralized fossil-fuelled) power plants, utilities install a "reserve margin" of roughly 15% extra capacity spinning ready for instant use.<ref name=al2009 />

Solid fuel nuclear plants have an additional disadvantage; for safety, they must instantly shut down in a power failure, but for nuclear-physics reasons, they can’t be restarted quickly. For example, during the [[Northeast Blackout of 2003]], nine operating U.S. nuclear units had to shut down and were later restarted. During the first three days, while they were most needed, their output was less than 3% of normal. After twelve days of restart, their average capacity loss had exceeded 50 percent.<ref name=al2009 /> Liquid fuel nuclear plants, particularly those with their fuel dissolved in salts, don't have the same downtime issues. Their nuclear fuel goes into a drain tank when any failure inside or outside occurs. This happens passively when the freeze plug melts because of the heat created by fission (in operation the freeze plug is actively cooled). The fuel is cooled passively and slowly, so when a restart is requested the fuel salt can simply be pumped back into the reactor core as it is still a liquid.<ref>http://moltensalt.org/references/static/downloads/pdf/FFR_chap17.pdf</ref> If the plant was shut down longer, the fuel needs to be reheated electrically and then pumped back. The reason a solid fuel reactor can't be restarted within seconds is because of the buildup of xenon, a radioactive gas that absorbs a lot of neutrons. As it is a gas it simply comes out of solution in a liquid fuel reactor<ref name='XenonMSRE page 95'>{{cite web|url=http://moltensalt.org/references/static/downloads/pdf/ORNL-TM-3464.pdf |title=Xenon Behavior in the Molten Salt Reactor Experiment |accessdate=2016-10-06 |date=October 1971 |work=OAK RIDGE NATIONAL LABORATORY Oak Ridge, Tennessee, operated by UNION CARBIDE CORPORATION FOR THE U.S. ATOMIC ENERGY COMMISSION }}</ref> and does not affect the restart process.<ref>http://moltensalt.org/references/static/downloads/pdf/ORNL-TM-3464.pdfTM-3464.pdf</ref>

==Solving intermittency==