I'm a big fan of wind and solar if properly sited to minimize impact to wildlife and ecosystems. I'm a fan because I know that nuclear energy can't replace fossil fuels on its own. I'm a fan of nuclear energy because the latest National Renewable Energy Lab study demonstrated that renewables can't do it alone. I wrote this article so that I (and others) can point to it the next time I (we) encounter someone claiming that storage is the answer for intermittency.
According to the U.S. Energy Information Administration there are only 40 pumped hydro storage sites in the entire United States (producing just 2% of our electric power) because the powerplants have to be situated near two bodies of water that have very different elevations and there are not many places with those characteristics located where powerplants need to be. From the EIA:
"The last pumped hydroelectric facility to come online in the United States was in 2002, with the prior facility built seven years earlier.
There has been increased interest in building new pumped storage plants, although construction has not yet been authorized. According to the National Hydropower Association, as of January 2012, the Federal Energy Regulatory Commission had granted preliminary permits for 34 GW of pumped storage capacity over a total of 22 states, which would more than double existing capacity. There are, however, significant challenges to building new pumped storage plants, including licensing, environmental regulations, and uncertainty in long-term electric markets.
In 2011, pumped storage plants produced 23 billion kilowatthours (kWh) of gross generation—roughly as much as petroleum-fired generation in that year [2 %]. Pumped storage plants, however, consumed 29 billion kilowatthours (kWh) of electricity in 2011 to refill their storage reservoirs, resulting in a net generation loss of 6 billion kWh. "
In other words, the relatively few potentially economically viable sites suitable for pumped hydro storage have largely already been spoken for. If pumped hydro were always an economically viable thing to do, all powerplants would have it. There are not anywhere near enough suitable sites to eliminate the intermittent nature of wind and solar power.
Ironically, it is thanks to pumped hydro that some nuclear power plants can produce both steady baseload power and extra power from its pumped hydro to help make wind power more viable by taking over when the wind quits blowing:
"Pumped storage plants play an important role in electric load shifting. They typically consume electricity during low-demand hours (e.g., nighttime), helping baseload plants to operate more efficiently by minimizing unwanted cycling on and off (a particular concern for nuclear plants, where cycling is extremely expensive and time-consuming). Subsequently, the gross generation that pumped storage plants put back on the grid is produced when electricity demand is high (daytime). This load shifting helps reduce generation from less efficient and more expensive plants, such as combustion turbines, that would otherwise operate during peak-demand hours."
Personally, I can't see humanity reducing GHG emissions in time, so this is largely an academic exercise for me. Because it is unlikely that renewables and nuclear together will be able to replace most fossil fuels in the time frame necessary to prevent the worst impacts of global warming, ocean acidification, etc, anyone who claims to know with certainty, or thinks we should take the risk that one or the other can do it alone has failed to grasp the sheer magnitude of the problem.