The conference where researchers are solving the clean-energy puzzle

This article is from The Spark, MIT Technology Review's weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

I spent last week in Washington, DC, and when I wasn't fawning over the cherry blossoms, I was soaking up all the newest and wildest ideas in energy.

The Advanced Research Projects Agency for Energy (ARPA-E) funds high-risk, high-reward energy research projects, and each year the agency hosts a summit where funding recipients and other researchers and companies in energy can gather to talk about what's new in the field.

As I listened to presentations, met with researchers, and-especially-wandered around the showcase, I often had a vague feeling of whiplash. Standing at one booth trying to wrap my head around how we might measure carbon stored by plants, I would look over and see another group focused on making nuclear fusion a more practical way to power the world.

There are plenty of tried-and-true solutions that can begin to address climate change right now: wind and solar power are being deployed at massive scales, electric vehicles are coming to the mainstream, and new technologies are helping companies make even fossil-fuel production less polluting. But as we knock out the easy wins, we'll also need to get creative to tackle harder-to-solve sectors and reach net-zero emissions. Here are a few intriguing projects from the ARPA-E showcase that caught my eye.

Vaporized rocks

I heard you have rocks here!" I exclaimed as I approached the Quaise Energy station.

Quaise's booth featured a screen flashing through some fast facts and demonstration videos. And sure enough, laid out on the table were two slabs of rock. They looked a bit worse for wear, each sporting a hole about the size of a quarter in the middle, singed around the edges.

These rocks earned their scorch marks in service of a big goal: making geothermal power possible anywhere. Today, the high temperatures needed to generate electricity using heat from the Earth are only accessible close to the surface in certain places on the planet, like Iceland or the western US.

Geothermal power could in theory be deployed anywhere, if we could drill deep enough. Getting there won't be easy, though, and could require drilling 20 kilometers (12 miles) beneath the surface. That's deeper than any oil and gas drilling done today.

Rather than grinding through layers of granite with conventional drilling technology, Quaise plans to get through the more obstinate parts of the Earth's crust by using high-powered millimeter waves to vaporize rock. (It's sort of like lasers, but not quite.)

The holey samples at the company's booth were the results of those tests. One was basalt, the other a column of granite: two common types of rock the company will have to tackle to reach the prize heat hidden underground.

Quaise has been testing its drilling technology in labs, starting with shallow depths and slowly working toward deeper and deeper holes. The plan is to start outdoor field trials later this year in Texas.

Slabs of fungus

Usually fungus would probably be one of the last things you'd want in your walls, but some researchers think it could help insulate buildings in remote areas.

Around a quarter of all energy worldwide is used to either heat or cool homes and commercial buildings. Boosting insulation could help cut power demand and keep people comfortable as temperature swings get more dramatic with climate change. But insulation materials, which range from plastics like polystyrene and fiberglass to cotton and recycled paper, can be expensive. And in remote areas, costs can balloon with shipping distances.

Some researchers at the National Renewable Energy Laboratory are working to bring natural insulation materials to remote areas like Alaska. By mixing cellulose pulp from local trees with mycelium (the rootlike structures of fungus), they hope to perfect a locally made solution and avoid shipping polystyrene boards across the world.

The project is a newer one, having just received ARPA-E funding this year. The team members are working to develop a mobile process to make the insulation, and they are also trying to boost the material's insulative capacity and make sure it's fire resistant.

A hybrid-electric plane

Okay, they didn't have the actual plane in the exhibition hall, but even a model plane is enough to stop me in my tracks, especially when it's paired with test flight footage featuring the real thing.

Ampaire is a California-based startup, and earlier this year the company completed a test flight of its Eco Caravan, a plug-in hybrid plane. By adding just a small battery, the company says, it can cut fuel consumption by 50 to 70% compared with conventional planes.

I'm really interested in this approach, especially because it could solve a regulatory quirk that's one of the reasons electric flight is so challenging.

Batteries are much heavier than jet fuel is, and current battery technology means that small planes could carry a few passengers a few hundred miles. But their theoretical range gets eaten up by something called reserve requirements. Basically, according to regulators, a plane needs to have enough fuel on board for emergencies. If there's an issue, it needs to be able to circle for a while, or even make it to a nearby airport to land. Safety, et cetera. So while a 19-seat electric plane in theory might be able to fly 160 miles, factoring in reserve requirements means the usable range might actually be more like 30 miles-a long bike ride.

By carrying reserve requirements in jet fuel and having only enough battery power for the planned flight, a hybrid-electric plane would get a lot of bang for its buck. Ampaire hopes to get certification for its system next year.

Keeping up with climate

If your spring sniffles have started already, you can probably thank climate change. Warm winters are causing earlier pollen production and longer allergy seasons. (Bloomberg)

A 2021 study found that fewer than 30% of electric vehicles are purchased by women. Unreliable charging stations and high prices, barriers for EV adoption in general, could be contributing to the gender gap. (The 19th)

Here's why EVs are finally hitting the mainstream. (MIT Technology Review)

An invasive vine called kudzu blankets the southern US. Now, warming weather is clearing the way for the plant's journey north. (NJ Spotlight News)

New rules for batteries in electric bikes and scooters in New York City could help make the low-emission vehicles safer. (Canary Media)

Cryptocurrency might not be the center of attention anymore, but the industry is still a climate problem. Bitcoin mining alone could continue releasing about 62 megatons of carbon dioxide into the atmosphere each year. (The Atlantic)

Renewable electricity beat out coal in the US for the first time last year. Wind, solar, hydro, biomass, and geothermal together made up just over 20% of total generation. (Associated Press)

Sea otters, gray wolves, and other animals could be important allies in addressing climate change. A new study found healthy populations of certain species could be key to helping capture carbon in ecosystems. (Grist)

Efforts to use geothermal power for electricity in Japan have been slowed by the nation's surprisingly powerful" hot-spring owners. (New York Times)