When Texas faced the biggest energy demand in history, it was renewable energy that stepped up. And storing energy in heat form may be the most economical solution available.

Texas gets by with a lot of help from renewable energy

When it gets hot in Texas, locals sometimes say, “It’s so hot the hens are laying hard-boiled eggs.”

There have been a lot of hard-boiled eggs in the Lone Star State lately. As a heat dome has settled over the region, the state has marked triple-digit highs almost daily, and on several days last month, it was in a showdown with the Sahara Desert for the hottest place on earth. (1)

And although Texas grid operator ERCOT had spent much of the Spring warning of possible brownouts and blackouts during the hottest months, a hero rode in from the East to save the day—the sun.

On June 27th, when the state saw the highest electricity usage on record (80,828 megawatts), solar and wind supplied 35% percent of that figure and allowed Texas to avoid significant outages. Texas has added over 6,300 megawatts of solar and wind capacity over the past year and paired that with 1,300 megawatts of battery storage. (2)

Texas has been installing solar at such a rapid clip that it will soon overtake California as the number one solar market in the country. (3)

Texas’s grid has been under increasing scrutiny since a 2021 winter storm shut down large swaths of the state for weeks, killing over 200 people.(4) Unlike other states in the Union, Texas maintains a separate grid and can’t access power generated from neighboring states. In other parts of the country, other utilities buy and sell electricity to buffer supply during extreme weather events.

July and August are often the most challenging months for Texas’s power grid, so the struggle to keep the state up and running continues. But the combination of renewable energy and storage has so far proven to be the answer to Texan’s’ energy needs to survive the effects of climate change.

Another brick in the renewable grid

It’s easy to see bricks as the enemy of technology. An angry mob throws bricks through windows and television screens. People use bricks to smash things. In the tech world, you can even “brick” something by installing software that makes it stop working.

But for startup Rondo Energy, bricks are now on the cutting edge of technology. And their ability to store energy efficiently may be one of the keys to achieving net zero.

Image credit to Rondo Energy

Energy storage continues to be key to a stable grid. Renewable energy like solar and wind are now the cheapest form of energy in history, but they have one big drawback—intermittency. In other words, solar energy is only available when the sun shines.

Cheaply storing renewable energy until it’s needed is the next technological hurdle in the clean energy revolution. Lithium-ion batteries—the type that power EVs and cellphones—are very good at storing energy, but the materials to make them are expensive and environmentally challenging to mine. Other chemical batteries are cheaper but are often less efficient.

Rondo Energy has taken a much different approach by creating a type of physical battery. Instead of storing energy in chemical form like lithium-ion, their batteries store it as heat.

Rondo lines a heavily insulated chamber with high-efficiency heating elements, much like the ones used in toasters. The chamber is filled with special heat-absorbing bricks. Using electricity drawn from renewable sources, the chamber can be brought to a scorching 1,500° Celsius. The insulated chamber can maintain that temperature for hours or even days with little loss. (1)

When energy is needed, the heat can send steam through a generator or be channeled out of the chamber and used for industrial purposes. The system offers a green solution for hard-to-transform sectors such as steel processing, cement manufacturing and low-carbon fuels.

At Rondo’s installation in Alameda, California, the stored heat energy is used by Calgren Renewable Fuels to process ethanol, significantly reducing the carbon footprint of their biofuels. The two-megawatt battery is 90% efficient and helps Calgren produce zero-carbon aviation fuel. (2)

The Alameda project is an important part of Rondo’s strategy. Although the technology around the specialized heat-retaining brick—known as refractory—has been in use for centuries in ceramic kilns and other applications, using it for energy storage is new. And because the refractory bricks are made with common materials using existing methods, the company has already begun to scale up production for new orders.

In June, Rondo announced a partnership with Siam Cement Group to manufacture a whopping 90 gigawatt-hours (GWh) of storage capacity per year. (3) To put that in perspective, Tesla’s Gigafactory in Sparks, Nevada, currently the largest battery production operation in the U.S., has 37 GWh of capacity. (4)

Although the company is focused on industrial applications, the heat battery model is also well suited for grid-based uses, including retrofitting existing steam-driven coal-fired plants.

Ninety GWh of capacity will keep 12 million tons of CO2 from the atmosphere—the equivalent of taking four million internal combustion vehicles from the road.

The Weekly Sunsong

This week is all about the heat, so let’s keep things warm with this Peter Gabriel classic: