When we move towards renewable energy, we need one crucial thing: technologies that convert wind and sun into a chemical fuel convert the storage and vice versa. There are some commercial devices that do, but most are expensive and only make up half of the equation. Now researchers have created laboratory-scale gadgets that perform both tasks. If larger versions work, they would help make the world renewable – or at least more affordable.
The market for such technologies has grown along with renewable energies: in 2007, the sun and wind had only 0.8% of all power in the United States; In 2017, according to the US Energy Information Administration, this figure was 8%. However, the demand for electricity often does not correspond to the supply of sun and wind. In sunny California, for example, solar panels routinely generate more electricity than is needed in the middle of the day, but not at night after most of the workers and students have returned home.
Some utilities are beginning to install massive battery banks to store excess energy and balance the balance. However, batteries are expensive and only store so much energy that they can only secure the network for a few hours at the most. Another possibility is to store the energy by converting it into hydrogen fuel. Devices called electrolyzers use electricity, ideally solar and wind power, to split water into oxygen and hydrogen gas, a carbon-free fuel. A second set of devices called fuel cells can turn that hydrogen back into electricity to drive cars, trucks and buses or feed it into the grid.
However, commercial electrolyzers and fuel cells use different catalysts to accelerate the two reactions, meaning that a single device can not perform both tasks. To get around this, researchers have experimented with a newer fuel cell, the so-called proton-conducting fuel cell (PCFC), which can generate fuel or convert it back to electricity with just one catalyst set.
PCFCs consist of two electrodes separated by a membrane that transports protons across. At the first electrode, the air electrode, steam and electricity are fed into a ceramic catalyst, which splits the water molecules of the vapor into positively charged hydrogen ions (protons), electrons and oxygen molecules. The electrons travel through an external wire to the second electrode – the fuel electrode – where they meet the protons that crossed the membrane. There, a nickel-based catalyst sews it to hydrogen gas (H 2 ). In previous PCFCs, the nickel catalysts performed well, but the ceramic catalysts were inefficient and used less than 70% of the electricity to break down the water molecules. Much of the energy was lost as heat.
Two research teams have now made significant progress in improving this efficiency. Both focused on improvements to the air electrode because the nickel-based fuel electrode has done a good job. In January, researchers led by chemist Sossina Haile at Northwestern University in Evanston, Ill., Reported in Energy & Environmental Science that they came up with a six-element ceramic alloy fuel cell that used 76% of it its electricity to split up water molecules. In today's issue of Nature Energy Ryan O'Hayre, a chemist at Colorado's Colorado School of Mines, says his team has made an improvement. Its ceramic alloy electrode, which consists of five elements, uses 98% of the energy that is injected to split water.
When both teams execute their settings in reverse order, the fuel electrode H 2 splits molecules into protons and electrons. The electrons travel through an external wire to the air electrode and supply power to the devices. When they reach the electrode, they combine with oxygen from the air and protons that have been crossed across the membrane to produce water.
The latest work by the Oâ € ™ hayre group is "impressive," says Haile. "The electricity you use generates H 2 and does not heat up your system. They did a really good job. "Nevertheless, she warns that both her new device and the device from the O & #; Hayre lab are small laboratory demonstrations. For the technology to have a societal impact, researchers need to increase the size of a button-sized device, a process that normally reduces performance. If engineers can do that, the cost of storing renewable energy could fall dramatically and help utilities eliminate their dependence on fossil fuels.