Cache Wind and solar power have become so cheap to install and, at times, so abundant that utilities don’t know what to do with it all. Sometimes, they’ll even pay the owners of other power plants not to generate electricity.
The Quest for Affordable Energy Storage Solutions
In response, scientists and engineers have been racing to find inexpensive ways to store that power for later. They ultimately hope to store renewable energy so that it’s available 24/7 and at a price that’ll put coal and natural gas out of business.
Cache Energy: A New Approach to Energy Storage
Cache Energy is the latest startup to attempt the feat, taking a slightly different tack than most. Rather than storing power as heat using sand or specially made bricks, Cache stores it in chemical bonds inside pellets of lime derived from limestone. Founder and CEO Arpit Dwivedi calls the approach “coal without consequences.”
The Concept Behind Cache Technology
“It’s a low-cost solid that can produce heat and use some of the similar infrastructure built around fossil fuel,” he told TechCrunch.
Dwivedi said that the pellets can be stored in piles or silos, moved around using conveyor belts, and transported via rail cars. “As long as you physically contain it — it could literally be a tarp — that is enough to hold its charge almost forever.”
Cache Stealth Mode and Technological Development
Cache has been operating stealthily until now. Dwivedi started the company in 2021, shortly before finishing his PhD at the University of Illinois, and he gave TechCrunch an exclusive look at Cache’s technology, which seeks to replace fossil fuel’s role in providing heat to homes and industries.
The Role of Calcium Hydroxide in Cache’s Process
The startup begins with calcium hydroxide, a widely available material from paper making and sewage treatment to pickling and nixtamalization. This process turns cornmeal into masa for tortillas. Calcium hydroxide is a powdery substance, which isn’t ideal for Cache’s process. If the granule size is too small, it’s liable to blow away, so the company figured out how to bind the powder so it holds up over time.
Optimizing Pellet Size for Efficient Energy Storage and Release
But the pellets can’t be too large, either, or they’ll stymie the next step: the reaction that stores and releases energy. “We iterated a lot on the size,” Dwivedi said.
How Cache’s Pellets Store and Release Energy
To discharge, Cache feeds the pellets through the same gravity-fed reactor, suffusing them with moisture to reverse the reaction and produce heat. Dwivedi said the overall efficiency of the system is around 95%.
Potential Applications and Future Developments
Cache’s pellets can produce heat at up to 550 degrees C, covering the bulk of industrial processes and commercial and residential buildings’ heat and hot water needs. Dwivedi said one shipping container of Cache’s pellets would be enough to get a couple of office buildings through the winter. The company is working on a new version that will generate heat at up to 900 degrees C, widening the range of industries it can sell to.
Cost-Effective Energy Storage with Cache Pellets
Cache’s goal is to keep the costs of its equipment and materials as low as possible. It’s using as many off-the-shelf parts as possible, and even at its current hourly production rate of about 500 kilowatt-hours, the pellets only cost about 20 to 40 cents per kilowatt-hour.
Competing with Fossil Fuels: The Role of Electricity Prices
Whether Cache can be competitive with fossil fuels depends heavily on how much electricity costs. Where wind and solar are plentiful, the pellets could be charged cheaply. Like any arbitrage opportunity, buying as low as possible is key.
Envisioning Cache Pellets in Real-World Use
If Cache’s pellets can withstand real-world use, it’s possible to envision them being charged in regions where solar and wind are plentiful, like Texas or Arizona, and shipped around the country to help run industrial facilities or heat office buildings. “Even a basement of a house, if needed, can host and store it,” Dwivedi said. Imagine a Cache truck delivering pellets before the start of every winter, just like heating oil trucks still do in the Northeast. It could go a long way toward decarbonizing heat, one of fossil fuel’s last bastions.
