Enlarge / Some solar panels, along with a diagram of a perovskite's crystal structure. (credit: Subhakitnibhat Kewiko)

As the price of silicon panels has continued to come down, we've reached the point where they're a small and shrinking cost of building a solar farm. That means that it might be worth spending more to get a panel that converts more of the incoming sunlight to electricity, since it allows you to get more out of the price paid to get each panel installed. But silicon panels are already pushing up against physical limits on efficiency. Which means our best chance for a major boost in panel efficiency may be to combine silicon with an additional photovoltaic material.

Right now, most of the focus is on pairing silicon with a class of materials called perovskites. Perovskite crystals can be layered on top of silicon, creating a panel with two materials that absorb different areas of the spectrum—plus, perovskites can be made from relatively cheap raw materials. Unfortunately, it has been difficult to make perovskites that are both high-efficiency and last for the decades that the silicon portion will.

Lots of labs are attempting to change that, though. And two of them reported some progress this week, including a perovskite/silicon system that achieved 34 percent efficiency.

Enlarge / A hydro-fracking drilling pad for oil and gas operates October 26, 2017 in Robinson Township, Pennsylvania. (credit: Robert Nickelsberg/Getty Images)

In 2007, a geoscientist at Penn State named Terry Engelder calculated that Pennsylvania could be sitting on more than 50 trillion cubic feet of accessible natural gas deposits. Engelder later revised his calculation upward, to 489 trillion cubic feet, enough to meet US natural gas demand for 18 years. These massive numbers set off the fracking boom in Pennsylvania, leading to drilling across the state. Since the rush began, there have been 13,000 unconventional wells drilled in Pennsylvania.

Now, a new “astounding” calculation has caught the attention of the gas industry: A study from researchers at the National Energy Technology Laboratory shows the wastewater produced by Pennsylvania’s unconventional wells could contain enough lithium to meet 38 to 40 percent of current domestic consumption. Lithium is a critical mineral that’s an “essential component” of many clean energy technologies, including batteries for electric vehicles. 

The study used chemical and production compliance data from the Pennsylvania Department of Environmental Protection to estimate that approximately 1,160 metric tons of lithium per year could be extracted from this produced water, which is a combination of fluids used for fracking and water from natural formations underground that returns to the surface during the drilling process. The lithium in Pennsylvania’s produced water likely comes from ancient volcanoes that were erupting at the time the natural gas deposits were being formed. This volcanic ash contained lithium that eventually seeped into the water underground.

Enlarge (credit: Ashley Cooper)

When used to generate power or move vehicles, fossil fuels kill people. Particulates and ozone resulting from fossil fuel burning cause direct health impacts, while climate change will act indirectly. Regardless of the immediacy, premature deaths and illness prior to death are felt through lost productivity and the cost of treatments.

Typically, you see the financial impacts quantified when the EPA issues new regulations, as the health benefits of limiting pollution typically dwarf the costs of meeting new standards. But some researchers from Lawrence Berkeley National Lab have now done similar calculations—but focusing on the impact of renewable energy. Wind and solar, by displacing fossil fuel use, are acting as a form of pollution control and so should produce similar economic benefits.

Do they ever. The researchers find that, in the US, wind and solar have health and climate benefits of over $100 for every Megawatt-hour produced, for a total of a quarter-trillion dollars in just the last four years. This dwarfs the cost of the electricity they generate and the total of the subsidies they received.