How could electrical storage be revolutionized?

September 10, 2018

In a 2010 TED Talk, Bill Gates stated that all the batteries in the world could only store 10 minutes of the total electricity generated by power plants. In an age where wireless devices surrounded us, batteries are arguably the weakest technological piece of the puzzle.

A new iPhone can recognize your face and has exponentially more memory than the rockets that put early astronauts on the moon. However, the lithium-ion battery powering most things is fairly similar to what we had 20 years ago and still has a limited lifespan. What battery technology is around the corner, and could it help make renewable power the dominant source?

What kind of battery would we like to have? A Slate article explains the five qualities of an ideal battery: “It would put a lot of energy in a small space; it would be inexpensive; it would lose in transfer less than a fifth of the energy put into storage and taken back out; it would last decades; and it would release the energy quickly. The optimal energy storage technology also would be safe to transport and nontoxic to dispose of, as well as made of raw materials that can be obtained without causing major environmental damage.”

At the most basic level, rechargeable electrical batteries are composed of a positively charged side (cathode) and a negatively charged side (anode). The anode and cathode are separated by an electrolyte, the middleman that trades ions back and forth. When you create a circuit from the negative to positive terminals to discharge the battery, electrons flow from the positive terminal to the negative terminal. Simultaneously, ions flow through the electrolyte, inside the battery. The electrolyte also keeps us safe; if the anode and cathode directly touch, you are in trouble.

Small electronics require powerful, lightweight batteries. Cars, computers, phones and other things that travel with you wouldn’t be effective if they were heavy. Lithium-ion/graphite batteries have a good power-to-weight ratio, but they also have to be carefully protected to prevent shorting.

If you crush or stab a lithium or lithium-ion battery, you are going to feel heat, at a minimum. At a maximum, a crushed battery looks like a volcano. Imagine if the pieces of bread in a grilled cheese sandwich were the anode and cathode of a battery, which would make the cheese an electrolyte. If the pieces of bread ever squished enough to touch each other directly, the sandwich would explode. That is basically the high stakes game of high-output batteries.

Thermal Energy Storage

What about home or industrial-scale energy storage? In hydronics, we like to store thermal energy in water because it has a high specific heat capacity. Thermal energy stored in water is part of the reason humans don’t freeze to death every night. Compared to other planets in our solar system, not naming names, the Earth is relatively balmy because its atmosphere allows the sun’s energy to filter in and the oceans then soak it up. The ocean is the largest battery in the world.

The largest human-created battery in the world is in Virginia. It is a pumped hydroelectric dam. This battery consists of two open reservoirs of water, one of which is uphill from the other. When area power plants generate excess energy or demand is low, this facility uses the electricity to pump water from the lower reservoir to the upper. When demand for electricity is high, the water flows back down, through a normal electric turbine, producing electricity, technically converting water pressure back into electricity.

According to NOVA, “about 99 percent of all grid storage in the United States is pumped hydro. It would be a relatively inexpensive way to store excess energy from renewables for later use, except for one problem. You need the right geography for the site, with changes in elevation. And even then, creating new ones can raise environmental concerns.” Also, energy is wasted in these open lakes when water evaporates.

What about salt/water electrical batteries? If we could use salt water from the ocean to make a battery, we would have an abundant cathode. Plus, sodium is more resistant to catching fire than lithium. However, some sodium battery technologies use hard carbon as an anode, which pairs well with lithium but is harder to come by than graphite.

Salt/water might not be a small- or medium-scale option. Water takes up more space than a couple of thin layers of lithium-ion cells. (Many round batteries are simply rolled, layered sheets of anode/electrolyte/cathode sheets.)

Other Technologies

Another battery technology on the horizon doesn’t use water or chemical reactions, just a big metal wheel. Flywheel batteries are exceptionally well-balanced, round steel objects magnetically levitated in an enclosed tank. When there is excess grid energy, a mechanism quickly spins the wheel. When electrical energy is needed, the momentum of the wheel is used to spin a generator and send power back into the grid.

These relatively simple battery systems are looking to scale up to industrial-grade use. Temporal Power in Ontario, Canada, is currently building a megawatt of flywheel storage.

On the nonmetal front, an interesting battery concept uses solar energy to convert CO₂ into methane, with a catalyst. The process isn’t super-efficient but the sun comes up every day and methane stores well. This process would produce a gaseous fuel to be used by conventional natural gas infrastructure and power plants for cloudy days.

Another battery factor to consider relates to abundance. Development of a new battery made from material located in a few parts of the world may throw us into another oil scenario. Lithium generally is plentiful, found close to the surface of the earth. And sodium and water cover most of the earth. However, these substances may not provide enough output to change the battery landscape.

It is hard to tell which battery technology will surpass lithium-ion or if we will keep a focus on making that technology safer. Upgrades in batteries may keep our phones powered up longer but should do much more.

Abundant batteries that could efficiently store electricity from solar and other renewable energy technologies would fundamentally shift the way we live with power. In a world with new batteries, the average home may not need a connection to the traditional electrical grid at all.

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