Enlarge (credit: Jorg Greuel)

Heat pumps are the most energy-efficient way of controlling indoor temperature. By moving heat between locations, they avoid the inefficiencies of generating heat in the first place. But that doesn't mean they can't be made more efficient.

Most current heat pumps rely on materials that exhibit large changes in temperature in response to changing pressures, but the energy required to pressurize them gets lost when they're cycled back to a low-pressure state, absorbing heat from their surroundings. That has gotten people interested in electrocaloric devices, where changes in temperature are driven by storing charges in a material. Since it essentially acts as a big capacitor, much of the electrical energy involved can be pulled back out as the system cycles.

But capacitors aren't especially mobile, so electrocaloric systems tended to use fluids to move heat into and out of the capacitor as it cycles. Now, however, researchers have developed an electrocaloric system that moves itself between hot and cold environments, radically simplifying the system and eliminating some of the energy required for it to operate. They even demonstrate it effectively cooling a computer chip.

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On Thursday, the US Department of Energy released its preliminary estimate for the nation's carbon emissions in the previous year. Any drop in emissions puts us on a path that would avoid some of the catastrophic warming scenarios that were still on the table at the turn of the century. But if we're to have a chance of meeting the Paris Agreement goal of keeping the planet from warming beyond 2° C, we'll need to see emissions drop dramatically in the near future.

So, how is the US doing? Emissions continue to trend downward, but there's no sign the drop has accelerated. And most of the drop has come from a single sector: changes in the power grid.

Off the grid, on the road

US carbon emissions have been trending downward since roughly 2007, when they peaked at about six gigatonnes. In recent years, the pandemic produced a dramatic drop in emissions in 2020, lowering them to under five gigatonnes for the first time since before 1990, when the EIA's data started. Carbon dioxide release went up a bit afterward, with 2023 marking the first post-pandemic decline, with emissions again clearly below five gigatonnes.

Enlarge (credit: boonchai wedmakawand)

California's electric grid, with its massive solar production and booming battery installations, is already on the cutting edge of the US's energy transition. And it's likely to stay there, as the state will require that all passenger vehicles be electric by 2035. Obviously, that will require a grid that's able to send a lot more electrons down its wiring and a likely shift in the time of day that demand peaks.

Is the grid ready? And if not, how much will it cost to get it there? Two researchers at the University of California, Davis—Yanning Li and Alan Jenn—have determined that nearly two-thirds of its feeder lines don't have the capacity that will likely be needed for car charging. Updating to handle the rising demand might set its utilities back as much as 40 percent of the existing grid's capital cost.

The lithium state

Li and Jenn aren't the first to look at how well existing grids can handle growing electric vehicle sales; other research has found various ways that different grids fall short. However, they have access to uniquely detailed data relevant to California's ability to distribute electricity (they do not concern themselves with generation). They have information on every substation, feeder line, and transformer that delivers electrons to customers of the state's three largest utilities, which collectively cover nearly 90 percent of the state's population. In total, they know the capacity that can be delivered through over 1,600 substations and 5,000 feeders.

Enlarge (credit: Frame Studio)

Almost from the start, arguments about mitigating climate change have included an element of cost-benefit analysis: Would it cost more to move the world off fossil fuels than it would to simply try to adapt to a changing world? A strong consensus has built that the answer to the question is a clear no, capped off by a Nobel in Economics given to one of the people whose work was key to building that consensus.

While most academics may have considered the argument put to rest, it has enjoyed an extended life in the political sphere. Large unknowns remain about both the costs and benefits, which depend in part on the remaining uncertainties in climate science and in part on the assumptions baked into economic models.

In Wednesday's edition of Nature, a small team of researchers analyzed how local economies have responded to the last 40 years of warming and projected those effects forward to 2050. They find that we're already committed to warming that will see the growth of the global economy undercut by 20 percent. That places the cost of even a limited period of climate change at roughly six times the estimated price of putting the world on a path to limit the warming to 2° C.

Enlarge / An oil refinery in Louisiana. Facilities such as this have led to a proliferation of petrochemical plants in the area. (credit: Art Wager)

On Tuesday, the US Environmental Protection Agency announced new rules that are intended to cut emissions of two chemicals that have been linked to elevated incidence of cancer: ethylene oxide and chloroprene. While production and use of these chemicals takes place in a variety of locations, they're particularly associated with an area of petrochemical production in Louisiana that has become known as "Cancer Alley."

The new regulations would require chemical manufacturers to monitor the emissions at their facilities and take steps to repair any problems that result in elevated emissions. Despite extensive evidence linking these chemicals to elevated risk of cancer, industry groups are signaling their opposition to these regulations, and the EPA has seen two previous attempts at regulation set aside by courts.

Dangerous stuff

The two chemicals at issue are primarily used as intermediates in the manufacture of common products. Chloroprene, for example, is used for the production of neoprene, a synthetic rubber-like substance that's probably familiar from products like insulated sleeves and wetsuits. It's a four-carbon chain with two double-bonds that allow for polymerization and an attached chlorine that alters its chemical properties.

Enlarge / Mining operations start right at the edge of Bulqizë, Albania. (credit: Wikimedia Commons)

“The search for geologic hydrogen today is where the search for oil was back in the 19th century—we’re just starting to understand how this works,” said Frédéric-Victor Donzé, a geologist at Université Grenoble Alpes. Donzé is part of a team of geoscientists studying a site at Bulqizë in Albania where miners at one of the world’s largest chromite mines may have accidentally drilled into a hydrogen reservoir.

The question Donzé and his team want to tackle is whether hydrogen has a parallel geological system with huge subsurface reservoirs that could be extracted the way we extract oil. “Bulqizë is a reference case. For the first time, we have real data. We have a proof,” Donzé said.

Greenish energy source

Water is the only byproduct of burning hydrogen, which makes it a potential go-to green energy source. The problem is that the vast majority of the 96 million tons of hydrogen we make each year comes from processing methane, and that does release greenhouse gases. Lots of them. “There are green ways to produce hydrogen, but the cost of processing methane is lower. This is why we are looking for alternatives,” Donzé said.