[liotier]

No, pumped storage is not "white-washing" : energy storage is the key piece to making unpredictable energy sources viable, by storing during low demand and having a buffer instantly available to respond to peaks. It displaces having extremely expensive gas turbines on standby or lighting up fuel burners during peak loads, so it has a direct impact on reducing fossil fuel consumption.

[jacquesm]

Of course it is. The arbitrage is what makes it happen because that's what makes it profitable. If the energy so generated were labeled with the point of origin then it would count as fossil fuel and then it would yield less on the energy market. The load variations are not such that the generating capacity could not be reduced in time, but there is less money in that.

This is not renewable energy though it masquerades as such. Note that before green energy became a thing this was already happening so it is simply a re-labeling rather than that these lakes suddenly got re-purposed for renewable energy storage.

If the source of the electricity is not originally renewable energy then it is deceptive to sell it as such. People pay a pretty premium for renewable energy.

[msandford]

> Of course it is.

Not necessarily!

It may be, it may not be. It depends on the time and place and whatnot. Pumped hydro today might be mostly "white washing" today in Scotland. It might not be "white washing" tomorrow in Germany. It depends on a lot of factors.

If the electrical rates do occasionally go negative in mainland Europe (from wind) and there are pumped hydro stations there then it's entirely possible that the wind electrons are the ones pushing the water uphill rather than the fossil fuel electrons, and then when that water eventually does generate electricity again, it's technically still renewable.

https://en.wikipedia.org/wiki/List_of_pumped-storage_hydroel...

It sounds like the plant that you visited in Scotland was white washing, at least when you visited. But that doesn't mean that all pumped hydro everywhere in the world definitely, for sure, guaranteed, is also doing the same.

[pjc50]

You've still not provided citations that the UK energy market actually classifies it that way.

[logfromblammo]

Pumped storage has the same "greenness" profile as the whole grid had when the pumping was happening, minus the efficiency loss from the round-trip conversion.

Pumping upward typically happens when the renewables are overproducing and the (controllably) variable power plants are idling. It makes no sense to run the pumps for storage when you could throttle back the gas turbines instead. But you can't adjust cloud cover, or tweak windspeed. So when the sun is shining, and the wind blowing, and the methane not burning, you store that excess for later.

That may also include relatively constant baseline power plants. But even then, the storage is often allowing those plants to run at their optimally efficient design capacity. If you idle the coal plant to 80% rated output, you may still be using 85% as much coal (made-up numbers for illustrative purposes). Trying to adjust the output of a nuclear plant is rather complicated, and may involve altering shutdown and maintenance schedules such that the output capacity several months in the future is affected by a decision made today.

So on the whole, re-generation from pumped storage is going to be greener than the baseline plants, and definitely greener than other types of adjustable peak load power plants, like natural gas turbines.

[liotier]

> Pumped storage has the same "greenness" profile as the whole grid

Yes !

> Trying to adjust the output of a nuclear plant is rather complicated, and may involve altering shutdown and maintenance schedules such that the output capacity several months in the future is affected by a decision made today.

Older nuclear power plants may take many hours, if not days, to achieve a steady state power output but modern nuclear plants with light water reactors are designed to have strong manoeuvring capabilities. Nuclear power plants in France and in Germany operate in load-following mode.

http://www.world-nuclear.org/info/Country-Profiles/Countries... says:

"There are two ways of varying the power output from a PWR: control rods, and boron addition to the primary cooling water. Using normal control rods to reduce power means that there is a portion of the core where neutrons are being absorbed rather than creating fission, and if this is maintained it creates an imbalance in the fuel, with the lower part of the fuel assemblies being more reactive that the upper parts. Adding boron to the water diminishes the reactivity uniformly, but to reverse the effect the water has to be treated to remove the boron, which is slow and costly, and it creates a radioactive waste.

So to minimise these impacts for the last 25 years EdF has used in each PWR reactor some less absorptive "grey" control rods which weigh less from a neutronic point of view than ordinary control rods and they allow sustained variation in power output. This means that RTE can depend on flexible load following from the nuclear fleet to contribute to regulation in these three respects:

- Primary power regulation for system stability (when frequency varies, power must be automatically adjusted by the turbine).

- Secondary power regulation related to trading contracts.

- Adjusting power in response to demand (decrease from 100% during the day, down to 50% or less during the night, etc.)

PWR plants are very flexible at the beginning of their cycle, with fresh fuel and high reserve reactivity. But when the fuel cycle is around 65% through these reactors are less flexible, and they take a rapidly diminishing part in the third, load-following, aspect above. When they are 90% through the fuel cycle, they only take part in frequency regulation, and essentially no power variation is allowed (unless necessary for safety). So at the very end of the cycle, they are run at steady power output and do not regulate or load-follow until the next refueling outage. RTE has continuous oversight of all French plants and determines which plants adjust output in relation to the three considerations above, and by how much.

RTE's real-time picture of the whole French system operating in response to load and against predicted demand shows the total of all inputs. This includes the hydro contribution at peak times, but it is apparent that in a coordinated system the nuclear fleet is capable of a degree of load following, even though the capability of individual units to follow load may be limited.

Plants being built today, eg according to European Utilities' Requirements (EUR), have load-following capacity fully built in."

http://www.neimagazine.com/features/featureload-following-ca... says:

"Slow ramps of =1.5% Pr per minute are most often used in France and the typical low power level is about 50% Pr. However, sometimes nuclear power plants operate at power levels below 50%. Some plants operate in a special operating mode (18 hours at rated power and 6 hours at low power) with steep ramps of 2-5% Pr per minute. In this mode the reactor is always capable of returning to the rated power level in a very short period, with a fast ramp of 5% of Pr per minute."

More on load following in nuclear power plants: http://www.oecd-nea.org/ndd/reports/2011/load-following-npp....

[logfromblammo]

And if this sort of thing interests you, also read up on "neutron poisons" and the "iodine pit".

Basically, it takes about 500 hours (3 weeks) before a chain-reacting fission core reaches equilibrium with neutron-absorbing reaction products. A core that is late in its fuel cycle might not be able to achieve a self-sustaining chain reaction from a shut down state until after the radioactive neutron absorbers have been left a while to decay.

The longer the fuel rod has been in the reactor, the less you are able to modulate its output.

You really do have to look at Europe (especially France) for operating nuclear plant best practices, because most plants in the US are not built to a common design, and they may not be able to adopt improvements pioneered at another site. The US solution is usually to put the upgrades into the next-generation reactor designs, which never quite get to replace the old existing designs because of radfear and NIMBYism.

[Gravityloss]

Gas turbines are not that expensive in capital. Instead they cost a lot to run, since they use gas that's much more expensive than coal. (Nevermind Uranium or wind or the sun.)

A big part of US climate strategy seems to be to install a lot of wind and solar power and fill the rest with natural gas, phasing out coal. Keep the nukes that are there. That's possible since in the USA, natural gas is cheaper than in many other places.