Weather

Hot sand – Rise with that?


Guest Post by Willis Eschenbach

I live at the top left of the map in Figure 1, in Northern California between Santa Rosa and the Pacific Ocean. Down the coast on the far side of San Francisco is Monterey Bay, and the town of Moss Landing.

Monterey Bay is famous for fishing and fishing as there is a submarine gorge that runs all the way to the shore at Moss Landing. This gives the deep water currents a wealth of nutrients, nurturing a rich marine ecosystem.

Half a century ago, I fished commercially for three years in Monterey Bay, two of them out of Moss Landing. There’s a huge old power station in Moss Landing that’s a friend to everyone who fishes that water, because it has two huge chimneys. We fish by night, not by day, and at any point of the night it is infinitely comforting to see the rings of red lights on the chimneys, visible from across the Bay. They mark home, land, and safety. These are the stacks on a full moon day.

Now, fifty years later, the power station is decommissioned but the chimneys are still there, the muted towers of an earlier time. You can see their silhouettes in the upper right of this aerial view of Moss Landing.

And what are the white squares at the dark end of the chimney? They are one of the topics of this post. They make up one of the largest battery installations on the planet. It includes hundreds of Tesla Megapack batteries. It stores on the order of 7.3 gigawatt-hours of electrical energy (GWh, or 109 watt-hour). This is a photo taken from the ground.

So… what’s not to like about megabat lithium batteries?

Well, the first thing not to like is the cost. The Tesla Megapacks price about $327 per kilowatt hour of storage, a huge amount. And with lithium prices skyrocketing, that will only increase. So building them at grid scale is extremely expensive.

The next problem is environmental destruction. Lithium mines are not beautiful and have the potential to damage the environment without special processes… processes that are unlikely to happen in lithium mining countries.

The next issue is safety. Here is a recent story

Second battery failure in less than 6 months reported at Moss Landing power plant

7:11 PM PST February 14, 2022: MOSS LANDING, California – At Moss Landing, firefighters responded to another battery failure at the Vistra Energy Storage Facility on Sunday night, as they When it arrived, about 10 battery holders were melted.

This is the second incident at the plant in just the past five months.

The fire brigade says the two incidents will provide a learning opportunity to make any necessary adjustments or improvements.

One concern is that this tree will get bigger.

A Tesla Megapack costs about a million dollars… and ten of them have gone up in smoke. It was an expensive “learning opportunity”.

And one last problem is lifetime. Lithium batteries can only cycle a certain number of times before they run out and need to be replaced.


With the list of problems with lithium batteries as the preamble, those who know me know that I am highly skeptical of new technologies. I have seen many and many “great breakthroughs” announced with great fanfare that never got on the drawing board.

But today, I found an energy storage technology that might actually work. Here is the drawing of the idea. It is being developed both privately and by the National Renewable Energy Laboratory (NREL). NREL calls the embodiment of this technology a “Durable” system.

ORIGINAL CAPTION: In a new particle thermal energy storage system developed by NREL, silica particles are gravity fed through resistive heating elements. Heated granules are stored in insulated concrete silos. When energy is needed, the heated particles will be passed through a heat exchanger to generate electricity for the grid. The system discharges during times of high demand and recharges when electricity is cheaper. Image by Patrick Davenport and Al Hicks, NREL.

TL; DR version: Electricity is used to heat the sand. When you need electricity, hot sand is used to boil water to run steam turbines to provide electricity.

So why do I think this is possible? Many reasons:

First, it’s very cheap. Instead of using expensive lithium for storage, it uses cheap silica sand. This reduces the cost from the lithium battery’s $327 per kilowatt-hour (kWh) to the NREL’s estimated cost of $2 – $4 per kWh. And even if the final cost is three times higher, it’s still only a few percent of the cost of a lithium battery.

Next, it’s safe. Sand cannot catch fire. Lithium can and does, and is very difficult to discharge once it starts burning.

Next, it’s scalable and cheap to scale. Add more insulated sand pools and you have more storage.

Next, it could be built on the site of closed coal-fired power plants. All the infrastructure is there — railroad tracks to bring in the sand, turbines, generators, substations, transmission lines, and the like.

Next, it doesn’t require any new or unproven technology. We know how to heat sand, how to build boilers and steam turbines, and how to do all of the things shown in the figure above.

So is this the secret technology that reduces solar and wind power to make a difference in the real world? Because so far, solar and wind have not been working properly.

It seems doubtful that it will change things that much. Storage is only a minor issue with sun/wind. A much bigger problem is that most of the electricity from the sun/wind is used immediately, and so there isn’t much left to put into storage. Next, both technologies require hazardous/rare/poisonous materials, which have a short lifespan and are difficult to recycle. In addition, wind turbines slaughter raptors, for a strange reason already discussed here.

And there’s another big problem… there’s not a lot of solar/wind power there to harvest because it’s so spread out and lots of good sites are already in use. So this storage technology can help a lot, but it won’t be revolutionary.

However, sand storage will still be useful for load balancing on the grid and must rapidly rise and fall to accommodate changes in demand.

There is already a Finnish company that is commercially testing this technology. It is called Polar night energy, and they’re using direct heat, not electricity, to heat the entire district of the northernmost towns. Here are their test settings:

Storing heat in the summer when it’s not needed, and releasing it in the winter when needed… works for me.

Anyhow, that’s good news for today… yes, I know that compared to the ongoing global madness, it’s not much, but it’s what I got.

My best wishes to all,

w.

Postscript: As always, I politely ask that when you comment on you quote the exact words you are discussing. This lets us all know exactly what and to whom you’re responding, and avoids endless misunderstandings.

Technical note: I ran some numbers to see if this would run out of pencils…it seems to happen. R code the computer language and the results below. Lines starting with “[1]”It’s the output of the computer. Anything on a line after the pound sign (#) is a comment.

(us_electric_consumption = 3.9e15)# watt-hours Wh
[1] 3.9e+15
(moss_landing_battery = 7.3e9)
[1] 7.3e+09
(enduring = 26e9) # enduring storage, watt-hours Wh
[1] 2.6e+10
(ca_electric_consumption = 280e12) # Wh
[1] 2.8e+14
(sf_electric_consumption = 5e12) # Wh
[1] 5e + 12
(ny_ electro_consumption = 51e12) # Wh
[1] 5.1e + 13
(enduring / ny_ electrical_consumption * secsperyear / 3600/24) # supply date for the City of NY [1] 0.19 (moss_landing_battery / ny_ Electrical_consumption * secsperyear / 3600/24) # days of supply NY city, Moss Landing Battery
[1] 0.05225152
(degrees_ temperature_swing = 900) #°C
[1] 900

(sand_specific_heat = 800e3) # joules/tonne/°C
[1] 8e+05
(storage = degrees_temperature_swing*sand_specific_heat) #storage joules/tonne
[1] 7.2e+08

(storage_whr = j2wh(storage)) # storage wh per tonne
[1] 2e+05
(tonnes_needed = enduring/storage_whr) # tonne
[1] 130000
(sand_density = 1.6) #tonnes/m^3
[1] 1.6
(volume_needed = tonnes_needed/sand_density) # cubic metres
[1] 81250
(tank_num = 5) # number of tanks
[1] 5
(cube_side = volume_needed^(1/3)) #metres per side
[1] 43.31196
(cube_side_per_tank = (volume_needed/tank_num)^(1/3)) #metres per side
[1] 25.32899
(cube_side_ft = m2ft(cube_side)) #metres per side
[1] 142.0993
(sand_per_ton = 40) # sand cost, $/tonne
[1] 40
sand_cost=tonnes_needed*sand_per_ton
paste0("Sand cost = $",format(sand_cost,big.mark=","))
[1] "Sand cost = $5,200,000"



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