Clever idea for bulk power storage

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#2948865 1-Aug-2022 11:22

DjShadow:

I still like the idea of using turbines that work off the current in the Cook Strait

Tidal stream turbines are still far from a mature technology.

One of the key issues is the marine environment is very harsh, especially in places with high tidal flows. Ain't going to be easy to install or maintain such a turbine.

At the same time as the above NZ, has some of the best onshore wind resource in the world, a technology that is fairly mature, and no need to antifoul etc.

frankv

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#2948866 1-Aug-2022 11:22

gzt: Brilliant. I heard of sand batteries recently. For the most part sand is good for localized storage only:

https://www.bbc.com/news/science-environment-61996520

I like this idea. But it could probably be low enough tech to do in your own home. I'm thinking of the typical winter usage pattern in NZ, where heating is on only in the evenings. So you could use solar during the daytime (or cheap off-peak power from the grid) to heat water (rather than sand) for home heating in the evening. Of course, people are doing this already by using solar to heat their hot water cylinders. Water is about 5 times more efficient than sand for storing energy (4190J/kg vs 830J/kg), but only between 0C and 100C. Sand is about twice as dense as water, so you would need 2.5 times the volume of sand to store the same amount of heat, but if you heat it to 500C instead of 100C sand becomes about twice as efficient.

From https://www.engineeringtoolbox.com/energy-storage-water-d_1463.html

Example - Energy stored in a 1000 liter water tank

Water is heated to 90oC. The surrounding temperature (where the energy can be transferred to) is 20oC.

The energy stored in the water tank can be calculated as

E = (4.2 kJ/kgoC) ((90 oC) - (20 oC)) (1000 liter) (1 kg/liter)

    = 294000 kJ

    = (294000 kWs) (1/3600 h/s)

    = 81.7 kWh

So that would be the equivalent of 4 * 2kW heaters running for 10 hours, which should be more than enough to keep all but the largest mansions warm. You do need some good insulation so you don't lose heat when you don't want to, and somewhere to store a tonne of water. Perhaps the obvious place would be underneath the house, so that any heat losses would still heat the house.

tdgeek

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#2948870 1-Aug-2022 11:30

Scott3:

You do need storage for that. Peak demand in NZ is cold winter evenings and mornings. When there is no solar output, and it is often still (no wind).

Fortunately we are already well placed with hydro storage, but this might require further optimization if we want to get rid of gas peakers.

My thought was use wind and solar for on demand when its there, that can conserve hydro lake levels. While you cannot turn hydro on and off easily you can reduce the load somewhat. As you say, EV, etc, more hydro, or more hydro storage

wellygary

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#2948977 1-Aug-2022 12:05

tdgeek:

My thought was use wind and solar for on demand when its there, that can conserve hydro lake levels. While you cannot turn hydro on and off easily you can reduce the load somewhat. As you say, EV, etc, more hydro, or more hydro storage

The biggest problem with that is transmission capacity, most of the Solar and Wind are in the North Island ( along with most of the load -ex Tiwai)

The Transpower network ( and cook strait cable) are still a limit to how much juice can get to Auckland from the South Island,

tdgeek

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#2948980 1-Aug-2022 12:11

wellygary:

tdgeek:

My thought was use wind and solar for on demand when its there, that can conserve hydro lake levels. While you cannot turn hydro on and off easily you can reduce the load somewhat. As you say, EV, etc, more hydro, or more hydro storage

The biggest problem with that is transmission capacity, most of the Solar and Wind are in the North Island ( along with most of the load -ex Tiwai)

The Transpower network ( and cook strait cable) are still a limit to how much juice can get to Auckland from the South Island,

Im in ChCh we have plenty of solar, and wind is a daily thing here. So should Chch (I mentioned regional earlier) add a solar farm or three, and turbines, whatever they use conserves the lakes and also reduces the trans Tasman load , as other N.I. regions would also have solar farms and turbines. If its evening and still, no gain, but the Sun and wind are frequent so whatever they feed locally is an amount of power not drawn from the lakes

MikeAqua

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#2948981 1-Aug-2022 12:15

If this pans out, then excess energy could be stored as heat, then converted back to electricity.

Extraordinary New Material Converts Waste Heat Into Energy (scitechdaily.com)

Still in the lab at this stage.

Mike

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#2949029 1-Aug-2022 12:18

Not sure how far along the idea is, but there is a plan for a bigish solar farm In Christchurch.

Kōwhai Park - A new concept in renewable energy - Christchurch Airport

tripper1000

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#2949382 1-Aug-2022 16:38

New Zealand is flush with grid-level storage. We have tonnes of the most commercially viable grid level storage in the world - hydro. Hydro is great for switching on and off to align with demand - far better/cheaper than thermal generators like coal and nuclear and arguably better than gas-turbine, and without the millennia long after-taste for the environmental types.

The present issue with our power system is that as our population/demand has grown, we've not been building complimentary base-load generation, which is eating into our hydro storage capacity. We need to either build more hyrdro storage, or more base-load generation - many of the options above are a best experimental - maybe they will do, maybe not, but geothermal is proven and we have plenty going wanting.

Someone above mentioned peak-shifting. Everyone except NZ does this. This is good for flattening demand and minimising the scale of network upgrades necessary, and minimising the grid-level storage needed, however Transpower discourages it - by charging off-peak users, to upgrade the system for the benefit of on-peak users. Growing the value of their network has eclipsed serving kiwis (an SOE behaving like a commercial monopoly).

MikeAqua

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#2949385 1-Aug-2022 16:45

An issue in NZ is that the storage is mostly in the bottom half of the SI, where as the population is in the top half of the NI.

We need more generation (realistically, base load) in the upper NI. There must be plenty more opportunity for geothermal. Taupo to Rotorua is more or less one big volcanic field.

Mike

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#2949400 1-Aug-2022 17:26

MikeAqua:
An issue in NZ is that the storage is mostly in the bottom half of the SI, where as the population is in the top half of the NI.

We need more generation (realistically, base load) in the upper NI. There must be plenty more opportunity for geothermal. Taupo to Rotorua is more or less one big volcanic field.

The answer is for the Mainland to declare independence and sell the power to Wellington.

SomeoneSomewhere

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#2949500 1-Aug-2022 20:27

MikeAqua:

SomeoneSomewhere:

or the ideal of just shifting demand to meet generation.

The idea of demand shifting from a domestic perspective is interesting, because the thrust of govt policy from decades now has been towards use of electricity as an energy source in the home.

- Air quality statutes pushed people away from fire to heat pumps (an effectively banned wetbacks).

- Push for EVs

- Banning natural gas connections for new houses

So people get home of an evening, turn on a couple of heat pumps, plug in the car, bath the kids and turn on the induction hob. Maybe 8 kW of load all at once.

Very peak loady.

Lots of that load doesn't need to be peaky, though.

EV can charge overnight.
Ripple control of HWC has been in place for decades. The move to smart meters should have included a move to smart load control, but instead we're treating the concept as obsolete.
Basically every heat pump has a schedule that can be set so it heats up before you get home, then ramps back during the 5PM+ peak period.

A lack of pricing signals (and being easy to avoid by just choosing a 24h plan) means we've stagnated in this regard. In some areas a maximum demand charge is essentially considered standard.

gzt

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#2949510 1-Aug-2022 21:13

Ripple control of HWC

To some extent I can understand quitting h/w ripple control. The standard h/w cylinder properly installed has little loss and requires little management. Is h/w load shedding really going to help where it's needed in 2022?

gzt

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#2949515 1-Aug-2022 21:31

EV can charge overnight.

EV power plans are readily available, and EVs tend to have a time schedule charging option available.

eonsim

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#2949519 1-Aug-2022 21:44

Scott3:

Long term in NZ, with a move towards 100% renewable energy I would expect the following:

Construction of a lot more renewable generation. Will need to re-work the market, as we will want to overbuild, meaning when production conditions are good, we have to turn down / off renewable generation, which under the current system would send the market price to near zero.

Alternatively to turning off renewable power sources like wind or solar, would be some sort of quick response load generation/power sink. Ideally you would keep your renewables running at full spec then dump the power into something useful in the smart grid, ie EV charging, hot water heating (could be a couple of GWs there), or hydrogen generation or desalinization or sewerage treatment, crypto (shudder), AC (spin up 1-100% of the heat-pumps in NZ), SPA pools or swimming pools (est 40,000 swimming pools in NZ, spin up there pumps and that's close to a 100MW of distributed load, ignoring heating systems). With enough overbuild of widely distributed renewables, a proper smart grid and distributed load that can spin up rapidly you could potentially build a profitable product/service, or at least a service that returned a proportion of the value of the excess electricity to consumers or the country... Would need a proper national smart grid and some very careful modeling.

gzt

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#2949521 1-Aug-2022 21:53

In NZ looks like there are times even in winter when hydro and renewables do not meet peak demand. If we are throwing away renewable energy in any form when it could have become electrical energy then storage to meet peaks starts to make sense.

“Much of the power will have to be stored for days or weeks at a time. Lithium batteries cannot do the job: their sweet spot is two hours, and they are expensive. You need "long duration" storage at a cost that must ultimately fall below $100 (£82) per megawatt hour (MWh), the global benchmark of commercial viability

If we are not throwing any energy away then this will not be useful. How much are we losing from hydro? If we are losing any I expect it will be used by EV overnight charging before too long. Then there's EV to grid that has to become an attractive storage option before long.

EV2G is not "day or weeks at a time". Highview Power is still attractive if we are throwing enough away.

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