Even if humanity could get 100% of its energy from solar, it would still face a problem — the sun only shines during the day. A huge problem scientific minds are eager to solve in terms of the green electricity solution puzzle is how to store that power to transport it and use it where and when it is necessary.

Solving this problem requires a coordinated effort between lab research and real-life innovations in the field. Large commercial construction sites are often the perfect testing ground. Here are five innovative energy storage solutions and the role they play in sustainable building projects.

Mechanical Energy Storage

Mechanical energy storage solutions often serve expedient purposes on building project sites. For example, construction workers already harness compressed air to power pneumatic tools such as jackhammers, drills, grinders and sanders.

Mechanical energy storage comes in four main types:

• Compressed air storage, the energy for which can come from wind farms.
• Gravity storage, from the potential electricity in elevated concrete or water. When crews need power, they lower the weight or release water to transform the potential energy into current through an electrical generator.
• Flywheel energy storage turns surplus electrical energy into turning wheels encased in a frictionless vacuum. It uses a magnetic field and is one of the cleanest energy storage solutions currently available.
• Pumped heat electrical storage operates similarly to your refrigerator. It uses a heat pump, which transports heat from “hot storage” to “cold storage,” generating mechanical energy along the way. This excess power then runs a generator.

Depending on the project, architects can also build these solutions into the final design. For example, combined heat and power generation such as a pumped heat electrical storage system works well for facilities that have consistent loads, such as hospitals, hotels, universities and correctional facilities.

Electrochemical Battery Storage

Of course, when many people think of storing green energy, their mind turns to batteries. They’re the magic that makes today’s electric cars run and are portable, making them perfect for carrying from site to site.

Job sites often rely on generators for the first couple of months to power everything from their lights to smaller tools. While many models run on diesel or biodiesel, solar generators can also do the job while creating zero emissions and next-to-no noise. For example, installing temporary solar panels could power the on-site office trailer, and extra batteries could supply the necessary energy for charging devices and tools.

Currently, the batteries for storing solar electricity require minerals like lithium and cobalt, the mining of which can harm the environment. However, innovations are underway to offer alternatives. Here’s what’s in development.

1. Flow Battery Storage

Flow batteries can store hundreds of megawatts of energy — enough to power thousands of homes. This technology has obvious applicability to the grid but could someday fuel job sites as well.

In a flow battery system, two substances undergo electrochemical reactions to transfer electrons to one another. These remain in two separate tanks that hold electrolytes, one positive, the other negative. Charging oxidizes one side or causes it to release electrons while the other gains them — during discharging, the order reverses. A pump circulates between two electrodes separated by a thin membrane to keep them from mixing by chance and dispelling epowernergy.

The only problem is the electrolytes lose charge over time. Using vanadium eliminates this degradation and makes such a battery nearly infinite, but this element exists only in remote global regions where it is hard to extract. Scientists are currently experimenting with alternative materials to increase the charging life span while minimizing environmental impacts.

2. Hemp Batteries

The University of Wisconsin-Milwaukee has been hard at work in a partnership with CEO of the Wisconsin Battery Co. (WinBat) Jeff Greene to develop hemp batteries. These hold the promise to replace lithium while eliminating the environmental problems caused by cobalt and nickel in current models.

WinBat recently broke ground on a new hemp battery facility in a plant abandoned by Energizer in its plans to move offshore to Singapore. It plans to launch its first hemp EV battery prototype in a 1982 Delorean converted to an electric model — in a nod to “Back to the Future” movie fans.

Hemp grows quickly and is now legal, thanks to the 2018 Farm Bill. It’s a highly renewable resource, is an incredible carbon sink and its successful use in EV batteries could increase demand sufficiently to make it a more affordable building material. That’s a double bonus for the planet, as houses built from the stuff also absorb atmospheric carbon.

Thermal Energy Storage

Nature offers another potential energy storage solution for sustainable building projects with thermal designs. Liquefying rock or sand and water mixtures allows the storage of heat energy, which crews can use for the following:

• Liquid-to-air transition energy storage: This process gathers excess energy from the grid, liquifies it and later turns it back into an expanding gas to power turbines and create electricity as necessary.
• Thermal sand batteries: These “batteries” consist of sand heated to 500 degrees Celsius. In their native Finland, these devices heat homes amid the depths of frigid winters. Currently, you need a lot of sand — and a huge container — to provide adequate storage. However, the Latvian company Batsand recently decided to create models designed for underground storage, similar to a septic tank. Crews could install such units in conjunction with solar panels and wind turbines on new builds and create a long-lasting heat source for new construction.

Hydrogen Electrolysis

Although it isn’t an energy storage solution per se, hydrogen electrolysis deserves a spot on this list of emerging green energy technologies. It may someday create clean power for daily use while helping crews drive to and around the worksite.

Hydrogen is the most abundant element in the universe and can generate nearly emissions-free electricity. However, most of it is trapped in compounds with other molecules — such as oxygen, to make water. Hydrogen electrolysis refers to breaking apart water molecules to create electricity. A recent novel technique developed by Northwestern University researchers uses iridium oxide — a by-product of platinum mining — to make this form of green energy production feasible.

It’s an idea that has captured big money interests. For example, the Toyota Corporation has recently joined forces with the Chiyoda Corporation and FuelCell Energy on two projects to create a large-scale electrolysis system and the world’s first tri-gen production system. The latter will produce three products — renewable electricity, renewable hydrogen and usable water.

Toyota also leads the way in hydrogen fuel cell vehicle development. In May of 2024, the brand demoed the first such big rig. Hydrogen fuel cells run longer than EV batteries and refill faster, and it hopes to make the rigs delivering materials to sites greener.

Innovative Energy Storage Solutions

Generating green energy is only half the battle. The other is storing it. Learning how to do so in the most expedient way requires the kind of testing only large-scale construction projects provide. Implementing such technology into sustainable building projects can lead to a cleaner, more carbon-free future.