Pumped Storage: what is the scale needed?

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OldGeek

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#272949 27-Jul-2020 10:02

From the Beehive site:
https://www.beehive.govt.nz/release/100-renewable-electricity-grid-explored-pumped-storage-%E2%80%98battery%E2%80%99

I understand the principle and wondered why this idea was not thought of long ago. The answer is scale - the pumped storage lake (PSL) would need to be many times the size of the hydro power station lake it augments unless the backup the PSL represents is a stop-gap measure designed to last just a few days. Given that recent droughts have lasted months this does not appear to be the answer to insufficient hydro storage during a drought period.

The press release cited has no technical detail (because its purpose is to publicise the funding it announces). The larger the PSL is the greater the RMA approval obstacle, as well as construction costs, site availability etc. Does anyone on GZ know more about the technical detail on this?

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#2529293 27-Jul-2020 10:10

Pumped storage isn't designed to run the country for a month. It is designed to take advantage of excess generation in a demand dip (usually at night) to pump up, and drain down to provide a boost during a demand peak. It is a battery, but with a running time measured in hours rather than minutes as with a lithium-ion grid store.

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wellygary

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#2529302 27-Jul-2020 10:29

SaltyNZ:

Pumped storage isn't designed to run the country for a month. It is designed to take advantage of excess generation in a demand dip (usually at night) to pump up, and drain down to provide a boost during a demand peak. It is a battery, but with a running time measured in hours rather than minutes as with a lithium-ion grid store.

This one could....

NZ's current hydro storage is abut 4500Gwh, about 6 weeks national winter load , this scheme would add between 7-10,000Gwh so basically freeing the network from winter droughts, as it would be able to run 12-18 weeks without any inflows....

Its the lake Onslow proposal that has been kicking round for 15 years, proposed by Professor Earl Bardsley

"A simulation evaluation is presented of the seasonal operation a possible 1,300 MW pumped storage scheme in New Zealand. The simulations are with respect to a site in Central Otago, where the existing Lake Onslow is expanded to serve as the upper reservoir. The lower reservoir would be Lake Roxburgh on the Clutha River.

the short version is here ,

http://erth.waikato.ac.nz/staff/bardsley/download/pumped_storage_note.pdf

A Phd thesis was done on it by one of his students, and that is here

https://researchcommons.waikato.ac.nz/bitstream/handle/10289/12423/thesis.pdf?sequence=4&isAllowed=y

SaltyNZ

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#2529304 27-Jul-2020 10:32

Ah, that's much bigger than most then. Nice.

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nickb800

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#2529305 27-Jul-2020 10:34

Presumably the role for pumped storage in dry years is to carry surplus electricity from night time into the day, rather than save (say) a months worth of water. Stations like Manapouri are relatively resilient to 'dry years' so could be relied on to provide plentiful night time power even through a dry year

Edit: I see the comment above about capacity - wow! I wonder how they manage the lake margins with such a range - would end up as a dust bowl

wellygary

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#2529327 27-Jul-2020 10:51

nickb800:

Presumably the role for pumped storage in dry years is to carry surplus electricity from night time into the day, rather than save (say) a months worth of water. Stations like Manapouri are relatively resilient to 'dry years' so could be relied on to provide plentiful night time power even through a dry year

Edit: I see the comment above about capacity - wow! I wonder how they manage the lake margins with such a range - would end up as a dust bowl

The range in margins is dependant on how big a lake they decide to make,

if it was fully drained it would only likely be for a matter of weeks at the end of Winter, and the spring melt /rains would be use to replenish it...

jonb

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#2529335 27-Jul-2020 11:10

I've visited the station in Dinorwig, North Wales. That's an impressive setup, and helps boost the peak capacity for Liverpool, Manchester areas.

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

Basically if we are going more wind and solar stuff like this is a pre-requisite, but with NZ (and similar in UK) electricity market structure makes investment case tricky?

Scott3

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#2529360 27-Jul-2020 11:19

Report here makes good reading, and where most of my numbers are from:

https://www.iccc.mfe.govt.nz/assets/PDF_Library/daed426432/FINAL-ICCC-Electricity-report.pdf

With regard scale, we are talking in the region of 1000MW generation (&presumably pumping) capacity & storage of 5000GWh. This is big (by New Zealand standards).

With the above numbers, if we ran the pumped storage flat out, it would last for 5000hours, or 208days (approx 7 months).

NZ Produced 42,900Gwh in 2017, so the 5000GWh of storage would be roughly 12% of our annual consumption.

SaltyNZ:

Pumped storage isn't designed to run the country for a month. It is designed to take advantage of excess generation in a demand dip (usually at night) to pump up, and drain down to provide a boost during a demand peak. It is a battery, but with a running time measured in hours rather than minutes as with a lithium-ion grid store.

We are talking about running the country (in a dry year, along side other generation capacity) for month's - see my numbers above.

Beehive press release:

The $30 million allocated will pay for the detailed development of a business case for a solution to address New Zealand’s dry year storage problem. This analysis will mostly focus on a pumped hydro storage project at Lake Onslow in Central Otago, but will also include the assessment of smaller potential pumped storage options in the North Island, as well as other alternative technologies.

I haven't done analysis, but I am fairly confident the handling of daily peaks can be done most effectively using conventional (non pumped) hydro, Combined with a few more pricing incentives to move consumption away from peak time, and a bit of additional load shedding. Existing hydro schemes could be made more "peaky" at relative low cost

Take a look at https://www.em6live.co.nz/

The overview tab shows a graph of NZ generation over the past 24 hours. Demand went from around 3800MW at 4am to 6500MW at 9am. Roughly 300MW of this demand increase was met via gas, and the remaining cria 3500MW was met via hydro. The following are running baseload, and don't significantly track demand: Geothermal, Cogen, Coal & Wind. As such, daily peaks are mostly handled by hydro anyway, with only a small contribution by gas.

MikeAqua

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#2529362 27-Jul-2020 11:19

wellygary:

This one could....

NZ's current hydro storage is abut 4500Gwh, about 6 weeks national winter load , this scheme would add between 7-10,000Gwh so basically freeing the network from winter droughts, as it would be able to run 12-18 weeks without any inflows....

Its the lake Onslow proposal that has been kicking round for 15 years, proposed by Professor Earl Bardsley

"A simulation evaluation is presented of the seasonal operation a possible 1,300 MW pumped storage scheme in New Zealand. The simulations are with respect to a site in Central Otago, where the existing Lake Onslow is expanded to serve as the upper reservoir. The lower reservoir would be Lake Roxburgh on the Clutha River.

That could get interesting, it's a good fishing lake. There may be support/opposition (probably both!) depending on likely effects on fishing.

Mike

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#2529374 27-Jul-2020 11:39

MikeAqua:

wellygary:

This one could....

NZ's current hydro storage is abut 4500Gwh, about 6 weeks national winter load , this scheme would add between 7-10,000Gwh so basically freeing the network from winter droughts, as it would be able to run 12-18 weeks without any inflows....

Its the lake Onslow proposal that has been kicking round for 15 years, proposed by Professor Earl Bardsley

"A simulation evaluation is presented of the seasonal operation a possible 1,300 MW pumped storage scheme in New Zealand. The simulations are with respect to a site in Central Otago, where the existing Lake Onslow is expanded to serve as the upper reservoir. The lower reservoir would be Lake Roxburgh on the Clutha River.

That could get interesting, it's a good fishing lake. There may be support/opposition (probably both!) depending on likely effects on fishing.

Interestingly most of the water storage (for potable supply) reservoirs in the UK are stocked with trout and the water companies make money selling day tickets to fishermen!

shk292

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#2529386 27-Jul-2020 12:06

And already we have environmentalists saying it shouldn’t be done because it’s a nationally significant wetland or something. Still searching for that zero carbon zero impact energy solution...

Earbanean

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#2529388 27-Jul-2020 12:16

From my recollection, one of the use cases for pump/storage is in countries with nuclear baseload power. It's expensive to back nuclear off at night, so they run them constant and where there's excess at night, they run the pumps to move water back up into storage. You're effectively storing your excess (cheaper) electricity in a 'gravity battery'.

SaltyNZ

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#2529390 27-Jul-2020 12:18

There is no such thing as a zero impact solution and there never will be. Only more or less impact solutions, all of which have their advantages and disadvantages. Only people who want to try to gotcha with silly strawman arguments would bring up 'zero impact'.

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Scott3

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#2529393 27-Jul-2020 12:31

Personally I think the goal of a 100% renewable electricity gird isn't a good idea at this stage.

Rather I think we should focus on a "Near 100% grid", keeping around a 1 GW of fossil fueled thermal capacity on standby to get us through dry year events with a return period between 15 and 150 years.

Frankly the cost to build out sufficient renewable capacity to cover the rarest of dry year events, could be better spend abating emissions elsewhere. (Or even just to allow power to be cheaper, hence encouraging more energy use be shifted from fossil fuels to electricity).

The report I quoted in my above post estimates the pumped storage option to have an emissions abatement cost of $250/t Co2e. This is good vs the $89,000/t Co2e of long term battery storage, or the $1,270/t Co2e cost of overbuilding renewable, but is still an order of magnitude higher than the current $25/ tonne emissions cost in NZ.

My thoughts (as an engineer with experience & interest in the sector, but with no detailed modeling or analysis) is that the best option will be a slight overbuilding of renewable energy schemes, combined with a small upgrade's for more peaking ability of existing north island hydro, and retention of existing thermal to cover us for dry year events with a greater return period than 15 years.

Regarding the additional renewable, Base load geothermal is especially attractive, but also wind & hydro where the catchment hydrology is diverse from the big south island schemes (i.e. North Island & West Cost of south island), along with wind (while weather depended, dependency is diverse from that of the big south island hydro scheme). There are a lot of suitable schemes consented and ready to go, that will be parked for an extended period of time without intervention due to the smelter announcement.

With regard's to the roughly 1MW of dry-year thermal capacity I propose, might as well use existing stuff to keep capital cost down:

500MW from the 2 remaining units of Huntley 1-4 (coal & gas compatible) (baseload)
155MW From Whirinaki Diesel (open cycle turbine peaker)
9MW From Bream Bay Diesel (Recip. peaker)
4MW from QE2 Park Deisel (Recip. peaker)
Cira 350 - 400 MW natural gas combined cycle - Either Huntley 5 or stratfield CC (baseload).

Sadly the above is the pick of the dirtiest of our generation asserts, but the natural gas combined cycle would be run first in the 1 in 15 year event, with the coal only being needed in much higher return period events. The high cost of running the diesel plants would make them the last resort (but handy to have in case there is a HDVC link or major north island plant outage).

Full analysis would need to be run, but generally natural gas isn't a great for a rarely used standby plants - it is basically uneconomical to store at this scale (requires expensive cryogenic LNG facilities), and as such requires signing supply contracts, which often have a substantial take or pay component.

The issue with too much reliance on pumped storage is the risk of consecutive dry year events (like we have for Auckland potable supply at the moment).

If we have an dry year in year 1, and largely run down the pumped storage, yet analysis of snow pack shows that supply is going to be very thigh through the next summer & subsequent winter, we will need to start a major conservation campaign. This will be politically unpopular, and will cause significant kickback against our good environmental intentions.

The other thing to note is that being anywhere a near 100% renewable grid will completly break our electricity market system. This will need to be complexity reworked (Would be nice if it was feasible to the government to take the sector back, and it be run with the sole goal of providing reliable, low emmisions, reasonably priced power)

jonb:

Basically if we are going more wind and solar stuff like this is a pre-requisite, but with NZ (and similar in UK) electricity market structure makes investment case tricky?

Not necessarily. We already have a lot of (non-pumped) storage on our grid. Wind supply is diverse from dry years, and works well with out existing hydro.

Solar is not a great option for NZ (at a policy level, quite happy for people to install solar if they want to). In short, our peak demand is in winter, while solar's peak output is in summer (longer days, better sun angle). We have heaps of consented grid scale renewable schemes that work out cheaper than solar, and that produce stable year round power (i.e. geothermal), or that favor generation in the winter (i.e. north island hydro). Essentially lots of solar will crowed out those schemes, making meeting peak winter demand more challenging.

You are right about the electricity market. A complete re-work (or elimination) will be needed as we approach 100% renewable.

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#2529395 27-Jul-2020 12:35

Earbanean:

From my recollection, one of the use cases for pump/storage is in countries with nuclear baseload power. It's expensive to back nuclear off at night, so they run them constant and where there's excess at night, they run the pumps to move water back up into storage. You're effectively storing your excess (cheaper) electricity in a 'gravity battery'.

This proposal is different from most pumped storage. We are talking about 5000 hours of storage.

Our existing hydro already soaks up the bulk of daily peaks without breaking a sweat. This is about seasonal demand, and long term storage to cover extreme dry year events.

As a comparison Snowy 2.0 (in Aussie - lots of coal combined cycle plants, also slow to ramp up and down) has twice the generation capacity, but only 175 hours of storage.

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#2529479 27-Jul-2020 14:01

nickb800:

Presumably the role for pumped storage in dry years is to carry surplus electricity from night time into the day, rather than save (say) a months worth of water.

That might be true if there was a large thermal generation component to electricity supply but with 90% hydro that can be brought online quite quickly it's easier to generate less at night time.

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