Can skyscrapers be turned into "gravity batteries?"

Yes, but why would you? It makes no sense. We have to stop this stupid green halo stuff.

Bloomberg describes buildings proposed by Skidmore Owings and Merrill (SOM) as giant gravity batteries, where surplus green power from solar panels in the daytime or wind turbines at night is used to winch giant blocks of concrete to the top of the tower, creating potential energy that is released when the blocks are dropped, turning generators to create electricity. Does this make any sense? Will Wade of Bloomberg writes:

Building owners and designers have a growing number of tools to limit carbon emissions from day-to-day operations, from better insulation to heat pumps. However, there are no substitutes for steel and concrete that are critical components of modern buildings, both of which are major sources of carbon emissions. There are efforts to decarbonize those materials, but they remain far from reaching a meaningful scale. For building owners looking to zero out emissions, turning a skyscraper into a massive battery is one avenue, according to Bill Baker, a consulting partner at Chicago-based SOM.

The first thing that makes no sense is this paragraph, which starts off talking about operating carbon emissions, then mentions upfront or embodied carbon emissions from concrete and steel, and then suggests that turning the building into a battery somehow zeroes out those upfront emissions, as if. And talk about being far from reaching a meaningful scale!

SOM is working with Energy Vault, a company that according to Wired, built a prototype 110 meter tall tower that hauled up 35 tonne concrete blocks. According to Bloomberg, SOM is talking a 300 meter tall tower that could include residential, retail and office spaces.

On their website, SOM says they are “engineering the future of renewable energy."

“When integrated into tall buildings, these systems can maximize sustainability, accelerate carbon payback of building construction, and lower the levelized cost of energy consumption. They can also bring sustainable energy storage to natural landscapes with minimal environmental impact.”

I did the math on gravity batteries a few years ago and concluded that they were a lot of work (and upfront carbon) for not much power. Of course that post is gone, so I will do it again.

• The potential energy= the mass x the accelleration due to gravity x the height

• potential energy (for a tonne)= 1000kg X 9.8 m/s2 x 300 meters =2,940,000 joules = 2,940 kj

• That converts to 0.817 kWh.

• Energy Vault says their designs are 80% efficient, so that drops to 0.6536 kWh.

• Assuming the blocks are 35 tonnes, that’s 22 kWh per block.

• 35 tonnes of concrete is a 2.35 meter or 8' cube. I could calculate the upfront emissions of that but it is nothing compared to the shaft, the cables, and the hardware.

• So basically, unless I am misplacing a few zeroes somewhere or screwing up a conversion, dropping 35 tonnes of concrete 300 meters generates 22 kWh of electricity, I am assuming once per day. That’s less than the 27 kWh you can store in two Tesla Powerwall batteries.

Watch the SOM video here.

A physicist looked at gravity batteries and concluded, “My view on this is that the energy density of the arrangement is just too low, the gravitational field on earth is too weak.”

And at what cost? How much money does it take to build these shafts and how much upfront carbon was emitted? All to generate five bucks worth of electricity every day per shaft? It boggles the mind and makes no sense. So why is SOM participating in this?

We have seen this movie before.

I complained about SOM a few years ago when they proposed their silly "Urban Sequoia" tower that eats carbon dioxide and is made of all-natural materials. This is an architectural firm that builds giant glass and steel office buildings and airports all over the world, contributing to the carbon crisis that we are in the middle of right now.

SOM Airports

I wondered why SOM was proposing such a ridiculous and impossible building and concluded it was for the “green halo effect,” defined by Greenbiz, “which can result when a company makes such a strong positive impression in the mainstream market with an environmental product or innovation that the success burnishes the firm and its other activities.”

It also smells like what Alex Steffen called "predatory delay," which he defined as "the blocking or slowing of needed change, in order to make money off unsustainable, unjust systems in the meantime." I concluded:

It's where one can say, "Don't worry, we really are thinking hard about how to fix the architectural world, someday this will all work, but in the meantime, we will keep building airports and glass towers, with our eyes set on 2050 or maybe even 2100 while we ignore 2030.”

…SOM has the talent and ingenuity to build carbon positive buildings using technologies that are proven, legal, and actually exist. Show us those—that is what we need now.

The silly skyscraper batteries are more of the same.