Recycling exhaust heat; photocatalysts for hydrogen production; and biofuels from bovine guts?
Recycling Exhaust Heat
Presently, a vehicle’s exhaust heat is just that: exhaust. But what if it could be used as an energy source? Presently, the concept is more pipe dream than reality because the thermoelectric materials that would need to be wrapped around exhaust pipes to reclaim that heat energy and transform it to electricity only operate at about 5% efficiency. However, researchers at the University of Michigan (umich.edu) have developed a thermoelectric material that makes it more feasible. They’ve mixed mechanically strong thermoelectric materials known as “skutterudites” with barium. This combination showed a decrease in thermal conductivity and a conversion efficiency increase to 20%.
Photocatalysts for Hydrogen Production
Not only are there challenges in creating mass-producible, affordable fuel cells for automotive applications, there is another factor that can limit the wide-spread use of hydrogen-powered cars: The availability of hydrogen.
For example, molecular hydrogen exists in low concentrations and must be extracted from natural gas or water, which are typically slow, energy-intensive processes. Researchers at the U.S. Department of Energy Lawrence Berkeley National Laboratory (lbl.gov) are onto a solution: They’ve developed a photocatalyst that accelerates light-driven chemical reactions to extract hydrogen from water using the sun’s energy.
To develop the catalyst, researchers rearranged the atomic surface structure of titanium dioxide nanocrystals to create the first disorder-engineered nanocrystal. Through simulated experiments over a 22-day testing period, the nanocrystal converted 24% of absorbed sunlight into hydrogen. This conversion rate is about 100 times greater than that of conventional semi-conductor photocatalysts. What’s more, after that test period, the catalyst proved to be durable, which is advantageous for hydrogen production.