[jacquesm]

Scotland (and other countries besides) has a lot of 'pumped storage', lakes at a relatively high point that are fed from lakes at a lower point by running pumps that push the water from the lower lake to the higher one when energy is cheap and then back into the grid when it is more expensive (when there is a scarcity).

The net effect of this is that electricity originally generated by nuclear plants and other fossil fuel plants gets 'converted' into (more expensive!) 'green' energy.

It's a kind of white-washing for electrons. The price difference can be substantial more than making up for the cost of the pumping and subsequent re-generation.

And of course it's the energy sold to the public that matters, not how it was originally generated so by double counting this energy it changes the balance considerably without there actually being more renewable energy to begin with.

[jsingleton]

Pumped storage is typically reported separately from Hydro. So much so that Hydro is officially referred to as "Non-pumped storage Hydro". Pumped isn't included as a renewable because the energy mix will depend on when it's recharging as a consumer of the grid. Typically this is overnight so usually nuclear power and wind is used as coal and gas spin down then.

Currently both pumped and hydro are making up about 1% of the UK grid each: http://www.gridwatch.templar.co.uk

It's only useful to think about it in the short term as long term it adds nothing. It just functions as a buffer.

You can go round one in Wales: http://www.electricmountain.co.uk

[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.

[teh_klev]

Scotland only has one pumped storage scheme (Cruachan). It's annual generation was only 705 Gwh (as at 2009), which is only 13% of total hydro generation. Sure there might be "green electron" washing going on, but it's probably not significant.

https://en.wikipedia.org/wiki/Cruachan_Power_Station

[jacquesm]

I visited the station a few years ago and it is the reason for my original comment, at the time this was explained in some detail by one of the people on the tour. Very impressive by the way and highly recommended if you're in the region.

As for the bookkeeping:

A certain amount of electricity is produced using renewables which is always < the current baseload. It is then (much) more profitable to sell this energy to consumers directly and then to use the reduced base load requirements to top off the lakes before reducing base load generation capacity. At night the process reverses and now the 'newly minted green electrons' get added to the green energy already being sold. This makes more money than selling the nuclear/coal/NG generated electricity directly even though there is some loss from the whole pumping operation.

Note that the scheme already made money based on the demand pricing of electricity, the 'green' aspect simply made it more profitable.

[logfromblammo]

You are describing some blatantly fraudulent bookkeeping right there.

Let's say you charge $0.15/kWh for "green" electricity and $0.10/kWh for "black" electricity. You can't change the color of the electrons once they are in the grid, just to make more money.

To say otherwise is to end up with stupid schemes like using a sulfur plasma lamp, powered by coal-burning, to shine artificial light on a solar cell. Or run air fans with your nuclear steam turbine to blow air across your wind turbines. Or endlessly pump the same water over a hydro turbine.

Power from pumped storage generates the same "color" of electricity as the electricity used to run the pumps. If the grid was 15% green when it went up, it will be 15% green when it comes down.

[teh_klev]

I too have visited it and can highly recommend visiting as well. My dad worked on its construction.

[jacquesm]

http://pics.camarades.com/v/jacques/trips/scotland08/dscf158...

Awesome trip, we took a mini clubman (the real deal) to Scotland.

[teh_klev]

Excellent. If you're interested in the history of hydro electric in Scotland I can thoroughly recommend "The Dam Builders: Power from the Glens":

http://www.amazon.co.uk/dp/1841582255

Also this chap has a fairly good bunch of images and maps of various scheme throughout Scotland, apparently blagging his way into some facilities to take photographs:

http://www.corestore.org/hydro.htm

It's a bit "Web 1.0" but there's some interesting stuff to look at if you like that sort of thing (which I do :) )

[danmaz74]

> The net effect of this is that electricity originally generated by nuclear plants and other fossil fuel plants gets 'converted' into (more expensive!) 'green' energy.

In some situations, even pumped storage storing non-renewable power power is "greener" than you seem to imply. The problem is that nuclear generators can't stop producing electricity when it's not needed; let's say you are France and a large part of your electricity is generated with nuclear power. If you can't store your energy, during the night you're producing power that you need to waste away. And during peak hours, you need to turn on many gas turbines to get additional power.

If instead you can store your additional energy during the night, and use that one during peak hours, you burn less fuel and pollute less.

[pjc50]

By "a lot" we mean "two power stations for a maximum of 0.7GW and 16GWH": http://www.withouthotair.com/c26/page_191.shtml

[protomyth]

I thought the whole point of pumped storage was to use solar / wind to do the pumping and release the water back (thus running the turbines) when it was dark or not windy. Why are they using nuclear or fossil fuels?

[jacquesm]

Yes, that's another use. But when it is favorable economically speaking then fossil fuels and nuclear will be used as well. The pumps don't care what color the electrons are. It's mostly a matter of bookkeeping and less one of technology. And as long as demand for electricity during peak times does not coincide with the point in the day when the peak amount of electricity is generated this is a nice way to make some money for the operators.

[maxerickson]

The owners of coal and nuclear plants are the ones that paid for the pumped storage, they had the idea of making their plant operations more efficient, not of storing renewable energy.

This is one of the early large ones, built by the local utilities:

https://www.consumersenergy.com/content.aspx?id=6985

[seren]

I am not sure about coal, but you can't easily shutdown a nuclear reactor, so there are times during the day when you are overproducing. So pumping some water is a way to not totally lose the energy produced during that time.

[jacquesm]

Shutting down a nuclear reactor can be done very fast (emergency shutdown, underload shutdown) but increasing the load takes much longer.

This is one of the reasons that the blackout of 2003 lasted as long as it did, due the rapid decrease in load a couple of nuclear plants did a rapid shut-down.

Most base-load generating plants are difficult to adjust to a rapidly varying load.

[Retric]

You could set a bypass around the generators to the cooling tower to reduce energy production without reducing the rate of nuclear reactions. They don't do this for a number of reasons which basically boil down to nuclear fuel being cheap so they would much rather shut down just about everything else.

This does create a minor issue if the grid fails, but that’s a rare event and doing an actual shutdown is considered safer.

[jacquesm]

Ah, so that's the reason. I actually wondered about this after the 2003 event, I was caught right in the middle of it and had plenty of reason for reflection on the theme of power generation (that plus a lifelong interest in renewables also caused me to look into the various alternatives).

[logfromblammo]

"Neutron poisons" that accumulate in fuel rods during normal operation can also interfere with a re-start. Sometimes a shutdown core has to sit for a few weeks to let those reaction poisons decay before it even becomes possible to sustain a controlled chain reaction in that core again.

[zurn]

Nukes are actually much better at load following than is commonly believed. It's used a lot in countries without significant hydro production, like Germany and France, and load following capability is a regulatory requirement in many/most markets. For rapid anomalous load events in the grid you of course revert to the shutdown mechanisms, but the load-following is used to keep up with everyday demand variations.

http://www.oecd-nea.org/ndd/reports/2011/load-following-npp....

https://www.oecd-nea.org/nea-news/2011/29-2/nea-news-29-2-lo...

[Gmo]

Hydraulic is far from negligible in France, around 10% of the total production (source in French from 2012 : http://www.france-hydro-electricite.fr/lenergie-hydraulique/... ).

What's more, we have dammed almost everything we could dam ...

[teh_klev]

Sure, but during a suitably windy night who's to say that a good number of those electrons used to refill pumped storage schemes aren't sourced from wind farms?