Batteries are the big conundrum preventing the future from being dominated by renewable energy. Stuffing enough batteries into buildings isn’t feasible anytime in the future, but a number of scientists have been working to answer the question “what if you could turn the building itself into a battery?” Rechargeable concrete batteries aren’t science fiction. If this experimental technology could be applied to our buildings it has the potential to change the world’s most used material into the key to sustainable energy.
Batteries aren’t all that complicated. Kids in science class have been turning potatoes into batteries for decades. For a basic Edison battery, all you need is an anode layer and a cathode layer to pass energy between. A good battery is all about having conductive material. Concrete reinforced with metal bars makes for a pretty decent conductor. For any foundation to be turned into a batter you need an iron-coated reinforcing mesh surrounded by conductive mortar to act as the anode layer, while a nickel-coated reinforcing mesh surrounded by conductive mortar to act as the cathode layer. Connect the two layers with a cement-based electrolyte separator and boom, you have a concrete battery.
Concrete batteries aren’t good batteries though. Concrete’s energy per unit volume is minuscule compared to the material used in traditional batteries. Lithium-ion batteries have an energy density between 250 and 350 watt-hours per liter. Concrete’s energy density is just 0.8-watt-hours per liter. Lithium-ion batteries are small, powerful battery cells used in cutting-edge electronic devices. But, concrete is all around us. What a concrete battery lacks in efficiency, it makes up for in scale.
Scale is the biggest problem for battery production of all types. The calculus of batteries boils down to efficiency. The less efficient a battery is, the more you need. Lithium-ion batteries may be hyper-effective, but the environmental cost of lithium mining is not sustainable at the scale required for lithium batteries to be a solution for most energy usage and storage nor as a business model. The growth in renewable energy has created a mineral crisis. Traditional batteries rely on lithium, nickel, cobalt, graphite, and manganese on top of the massive amounts of copper and aluminum needed to build out new energy infrastructure to support the batteries.
“The data shows a looming mismatch between the world’s strengthened climate ambitions and the availability of critical minerals that are essential to realizing those ambitions,” Fatih Birol, executive director of the IEA, said in a statement. “The challenges are not insurmountable, but governments must give clear signals about how they plan to turn their climate pledges into action.”
Just a few countries control the vast majority of critical mineral deposits. South America’s Lithium Triangle, between Argentina, Bolivia, and Chile, controls roughly 75 percent of the world’s known lithium deposits. The Democratic Republic of Congo controls 70 percent of cobalt mining. China refines roughly 90 percent of the world’s rare earth minerals needed for advanced renewable technology. Even if new deposits were discovered today, mines take on average 16 years to start production, so those monopolies won’t change any time soon. All of this is to say there are major political, economic, diplomatic, and environmental concerns around managing the supply of minerals needed for the scale of battery production to shift the globe to renewable energy. Relying on concrete, iron, and nickel, some of the world’s most widely used materials, doesn’t sound so bad.
Concrete batteries are a promising technology but are not yet a viable solution. “We’re getting milliamps out of [cement-based batteries]—we’re not getting amps,” Aimee Byrne, a structural engineer at Technological University Dublin involved in the research told Scientific American. “We’re getting hours as opposed to days of charge.” She adds, however, that “cement-based batteries are completely in their infancy compared with other battery designs.
The first batteries ever created weren’t much better. Just as then, concrete batteries are a promising start that needs more refinement before serious application. The latest iteration of concrete batteries is itself an improvement on a concept pioneered years ago. This round of concrete batteries can store ten times the energy, showing progress is already being made. In addition to energy storage issues, battery life will need to be improved. Concrete structures are built to last decades, so the battery must match that. Creating concrete strong enough to last and conductive enough to be useful is proving to be a ‘major challenge from a technical point of view.’ Also, concrete itself comes with a myriad of environmental complications that we’ve covered before. Current cement production methods are not a path towards sustainability until a better, less carbon-intensive form of concrete becomes widespread.
Solutions to climate change must be as big as the scale of the problem. Building out batteries and renewable energy production to the scale required has always been the biggest problem. Every potential solution faces serious problems scaling, whether that be from efficiency, lack of resources, or cost. Concrete is the only resource used at the scale needed for change. Buildings as batteries offer enormous potential for energy storage. Batteries that double as structural components are an idea too good not to pursue. They may be a moon shot, but it’s a shot worth taking.