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Synthetic Fuel From a Solar Collector

Solar energy powers greenhouse-gas-free synthetic fuel production in Sandia experiment

3 min read

7 January 2008—At first blush, you might lump claims about a machine that supposedly turns sunshine, air, and water into fuel in the same category as e-mails insisting that someone in Nigeria will pay you handsomely to help free up a large sum of money. But researchers at the U.S. Department of Energy’s Sandia National Laboratories, in Albuquerque, say they have created a device that can break water into hydrogen and oxygen using sunlight, or in a another reaction convert carbon dioxide, to carbon monoxide that combines with hydrogen to make hydrocarbons such as methanol, ethanol, and even gasoline or diesel fuel. The technology holds the promise of using the same resources as biomass-to-fuel schemes but with potentially greater efficiency, according to the researchers.

The machine, called the Counter Rotating Ring Receiver Reactor Recuperator, or CR5, is essentially a stack of rings or disks, each outfitted with a dozen fins around its circumference that are constructed of a reactive metal oxide (rust to you and me) in a matrix of material that can withstand high temperatures. As a ring rotates, the reactive material passes into a chamber irradiated by a solar collector where temperatures exceed 1500 °C. This is hot enough to trigger a reaction that liberates oxygen from the rust, changing the metal’s chemical structure at the same time. The ring rotates the metal oxide (at roughly 1 revolution per minute) 180 degrees to a reaction chamber where, at relatively cool temperatures (around 1000 °C), the scorched rust is exposed to superheated steam. The metal oxide and water react in a way that effectively strips the oxygen from the water and restores the rust to its original form, yielding free hydrogen in the process. Then the cycle begins again.

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This photograph shows a car with the words “We Drive Solar” on the door, connected to a charging station. A windmill can be seen in the background.

The Dutch city of Utrecht is embracing vehicle-to-grid technology, an example of which is shown here—an EV connected to a bidirectional charger. The historic Rijn en Zon windmill provides a fitting background for this scene.

We Drive Solar

Hundreds of charging stations for electric vehicles dot Utrecht’s urban landscape in the Netherlands like little electric mushrooms. Unlike those you may have grown accustomed to seeing, many of these stations don’t just charge electric cars—they can also send power from vehicle batteries to the local utility grid for use by homes and businesses.

Debates over the feasibility and value of such vehicle-to-grid technology go back decades. Those arguments are not yet settled. But big automakers like Volkswagen, Nissan, and Hyundai have moved to produce the kinds of cars that can use such bidirectional chargers—alongside similar vehicle-to-home technology, whereby your car can power your house, say, during a blackout, as promoted by Ford with its new F-150 Lightning. Given the rapid uptake of electric vehicles, many people are thinking hard about how to make the best use of all that rolling battery power.

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