Concrete blocks for energy storage

[Guest Alphonsox]

Probably not the answer for the piles of blocks I've got left over after the build but an interesting and simple idea nevertheless.

 

https://qz.com/1355672/stacking-concrete-blocks-is-a-surprisingly-efficient-way-to-store-energy/

[Ed Davies]

There's a British company doing something similar lifting a block up and down an old mine shaft and an Australian company running a train up and down a track on a hillside. That crane idea is neat in that it could be put anywhere - e.g., places without mineshafts or hills. All depends, of course, on whether they really can get that efficiency.

[Cpd]

Interesting read and a nice idea but I personally don’t see it as a long term success story, but would be great to be wrong  and it works out a total success! 

[ToughButterCup]

I came here expecting a fight about Thermal Mass. #DisappointedOrWhat

[ProDave]

Now if I had read that article on April 1st.......

 

Personally I think the overhead of all the other moves the crane has to do to traverse, pick up, set down etc will seriously eat into the stored power. But like others it would be nice to be proved wrong.

[Ed Davies]

2 hours ago, recoveringacademic said:

I came here expecting a fight about Thermal Mass.

 

OK, I'll bite. The article says:

 

Quote

whereas London peaks in winters because of household heating

 

Storing electricity for later use as heat, particularly low grade heat, is almost always a bad idea. Like many materials, concrete has a specific heat capacity of the order of 1000 J/(kg·K) (more than 500, less than 2000). In Earth's gravitational field all materials have a “specific potential energy capacity” of 9.81 J/(kg·m) (depending only slightly on where you are on the planet and how high you are). So raising the temperature of a block of concrete by 1 K (i.e., 1 °C) stores as much energy as raising it just over 100 metres.

 

(Some calculations I did a while ago showed store energy for heat in a lead acid battery would have a higher capacity if you just heated them up to about 80 °C (IIRC) rather than charge them.)

 

Water has many odd thermal properties including an unusually high specific heat capacity. It'd store about four times as much energy by being heated.

 

Of course, the advantage of raising the concrete 100 m would be that it would stay there (baring settlement) whereas heated material tends to cool down over time. Also, if you store electricity you can then use a heat pump getting (say) three times as much heat out whereas if you use a heat pump then store the heat you need to store three times as much energy.

 

One way to get longer-term energy storage is to use a phase change of the material so it's stored as latent rather than sensible heat. E.g., melt wax or salt or dry out some cat litter. Later you can allow the wax to solidify or the cat litter to absorb moisture releasing heat.

 

I'm rather taken by the phase-change inter-seasonal energy store concept being pioneered by a couple of materials science PhDs in SE Austria: they use a heat pump to extract energy from a tank of water in a cellar under their house. During harder winters this freezes a large proportion of the tank but that's OK, as water freezes it gives off a lot of energy. They have a very large low-grade thermal collector (a fence made out of black pipes) which trickles ambient energy into the store and heat pump even when it's cloudy and the outside temperature is below zero so something like half their heat-pump input comes from the environment over the winter and it quickly melts and warms the store in the spring. They can also use the heat pump in reverse to move heat from the house into the water in summer for a bit of cooling.

 

The latent heat of fusion of water (i.e., the amount of energy you need to extract to freeze it) is 334 kJ/kg so freezing an amount of water gives as much energy as lowering it from 34'000 metres (more than three times the height of Everest).

 

In general, I'd say electrify all the things but think very carefully about storing energy for heat as some form of heat near its point of use.

Edited August 19, 2018 by Ed Davies

[Jeremy Harris]

I've been using phase change heat storage for a fair time now, to heat our hot water.  Works exceptionally well, with much lower standing losses than a tank full of hot water.  Currently I'm running a very early, first generation, Sunamp PV (one of the pre-production models) that has been delivering hot water, primarily from charge from excess PV generation, for a couple of years or so. 

 

I'm just about to switch over to the newer, simpler and higher capacity Sunamp UniQ eHW 9, which will increase our hot water storage capacity to about 10.5 kWh yet only increase the standing loss per day by around 150 Wh. 

 

We found that the decrease in standing loss from our old double foam sprayed 210 litre thermal store, which was then fitted with an additional layer of 50mm PIR foamed in place all around it, when we first fitted the Sunamp PV was massive - our daily heat loss dropped from around 2.5 kWh with the old well-insulated thermal store running at around 65 deg C to around 600 Wh with the Sunamp PV.  This made a really big difference to the temperature in the services room, which had reached over 40 deg C with the old well-insulated thermal store; enough to damage the oak door between it and the adjacent bedroom and contribute to that bedroom over-heating in summer.

 

Both these phase change "heat batteries" use a sodium acetate based mixture, and operate at about 58 deg C.  In practice the case of the Sunamp PV never feels even slightly warmer than ambient, which is distinctly odd when a tap is turned on and the outlet pipe quickly gets very hot.  It works very like a thermal store, with a heat exchanger internally that quickly heats incoming cold water up to 58 deg C on demand.  There's some cunning system to control the phase change, by allowing nucleation to be stopped and started at will, which seems to be the key to getting a practical phase change material thermal store.

[Nickfromwales]

Cost of maintenance and replacing the ( crane ) cables etc I fear has been downplayed a bit. I don't see that running for 30 years without a major overhaul. 

I do like the concept, and there are some ingenious ways of storing / balancing. 

Pumping water has to be a contender. 

Edited August 19, 2018 by Nickfromwales

[Jeremy Harris]

Pumped water has been working well at places like Dinorwig ( https://en.wikipedia.org/wiki/Dinorwig_Power_Station ) for many years, I think the main issue is finding suitable sites where there is both a large enough volume and sufficient head between two lakes or reservoirs.

 

 

[ProDave]

There is a new pumped storage scheme proposed above Loch Ness  https://www.bbc.co.uk/news/uk-scotland-highlands-islands-44560894

 

This is in addition to the smaller one already in operation at Foyers that is a combination of conventional hydro generation with an element of pumped storage.

[Ferdinand]

I think the concrete block solution may not be competitive with eg Sunamp Container-Size.

 

The 400ft High by 100ft (guestimated) diameter of the concrete tower stores 20mWh of energy.

 

A Sunamp container is quoted as ‘Multiple mWh’, which I make as perhaps 3mWh based on 50 pallets in 2 layers each storing 60kWh.

 

That makes the Sunamp equivalent a 8ft x 40ft  footprint to a height of 8ft x 7 = 60ft, Or I expect rather more energy storage in a single layer of standard containers on the same footprint as the tower.

 

Lots of approximations and guesstimates and fiddle-factors, but I make the Sunamp storage density more than 50x higher, which is some barrier to overcome even if I have estimated everything 100% out the wrong way.

 

So my call is interesting but unlikely.

 

And I wonder what the emissions are from manufacturing all that concrete.

 

Ferdinand

[Onoff]

There was an Israeli idea a few years back that was a wall made from rotatable concrete columns. The outside was "black" concrete and there was an insulating core.

 

The black concrete heated up during the day and the sections were rotated at night to face into the building. 

 

Not sure what they did, if anything about heat loss and air tightness at the gaps between columns.

[ToughButterCup]

54 minutes ago, Onoff said:

[...]

The black concrete heated up during the day and the sections were rotated at night to face into the building. 

[...]

 

Now this is more like it.  Warming up nicely, (as it were) Go on son, give it some !   #ThermalMassMyth

[ragg987]

1 hour ago, Ferdinand said:

I think the concrete block solution may not be competitive with eg Sunamp Container-Size

I see these as complementary rather than one being better.

 

The concrete shifts excess electricity towards peak, the sunamp is about heat so is useful in a local context (house / factory / district).