Researchers from the Department of Energy's Pacific Northwest National Laboratory will exhibit their work at the 2013 Energy Innovation Summit of high-impact energy research funded by DOE's Advanced Research Projects Agency-Energy, or ARPA-E. The summit runs Feb. 25-27 at the Gaylord Convention Center in National Harbor, Md. Below is an overview of PNNL research that will be highlighted there.
PNNL is developing a metal hydride powder that can store up to 10 times more heat per mass than the molten salts typically used in thermal energy storage systems, such as this one in Spain. Photo courtesy of Alejandro Flores.
Nighttime solar power with cheaper thermal energy storage
Solar power is a clean source of energy, but its use is limited to when the sun shines. One option that extends solar energy into the night involves capturing the sun's heat during the day and releasing it when it's dark. Called thermal energy storage, the practice has been limited because the molten salts typically used to store solar heat for power production require large, expensive equipment. PNNL materials scientist Ewa Rönnebro and her team have shown that a powder made of a proprietary metal hydride can store up to 10 times more heat per mass than molten salts and operate at higher temperatures. PNNL and project partners University of Utah and Heavystone Lab are developing a 3 kilowatt-hour thermal demonstration system that will collect heat for six hours and discharge it over another six hours. If successful, the project could make thermal energy storage systems smaller and more cost-competitive.
New fuel storage tanks lighten the load for compressed natural gas vehicles
With the nation's supply of natural gas increasingly abundant and inexpensive, the fuel is being considered as a cleaner way to power light-duty cars and trucks. But while more than 15 million natural gas vehicles operate throughout the world, only about 150,000 are running on America's roads. One challenge is that natural gas exists as a vapor, meaning it contains less energy per volume than the denser, liquid gasoline most of us pump into our cars. Natural gas must be compressed into a pressurized fuel tank to increase its energy density. PNNL engineer Kevin Simmons and his team are developing special, lightweight fuel tanks that make better use of the limited space available in vehicles. PNNL's fuel tank design uses a unique manufacturing method called superplastic forming. The method involves welding together metal sheets at specific points and blowing air in between the sheets to expand them, forming internal chambers like an air mattress. The expanded metal tank will conform to more of a vehicle's space than traditional cylinder tanks. It also helps the cars weigh less, which makes them more fuel-efficient. The PNNL tank is expected to cost $1,500 to make and pack 12 megajoules of energy per kilogram, about twice the energy density of today's metal compressed natural gas tanks. Lincoln Composites is a partner in the project.
Rare earth-free magnet makes electric motors cheaper with more abundant materials
From wind turbines to electric vehicle motors, magnets play an essential role in a variety of today's electronic devices. But there's a limited supply of the rare earth minerals that are traditionally used in these magnets. In particular, dysprosium is added to increase a magnet's operating temperature, which is high in motors. But dysprosium has been named a critical material with unstable availability. PNNL materials scientist Jun Cui and his team are developing a manganese-based nano-composite magnet that doesn't contain dysprosium or any other rare earth mineral. The new magnet can operate at 200 degrees Celsius. The team's immediate goal is to make a permanent magnet with 10 MGOe, or megagauss-oersteds, a measurement of magnetic energy. With additional funding, the team will work to develop a 20-MGOe magnet, which would be more useful for a broader set of commercial applications. Project partners include PNNL, the universities of Maryland and Texas at Arlington, Ames Laboratory, Electron Energy Corp. and United Technologies.
Membrane dehumidifier makes air conditioners up to 50 percent more efficient
Americans unnecessarily spend billions of dollars on power bills when humid air causes their air-conditioning systems to be inefficient. To cut electricity use for cooling in hot, humid climates by 50 percent, a team led by ADMA Products and including PNNL and Texas A&M University is developing a novel dehumidifier. The system uses a thin membrane developed by PNNL chemical engineer Wei Liu and his PNNL colleagues that acts as a molecular sieve and soaks up water from the air. The membrane consists of a thin, foil-like metal sheet that's coated with a layer of a water-attracting material called zeolite. Just one-fifth the width of human hair and made from common, inexpensive materials, the membrane removes moisture from air many times faster than dehydration membrane products currently on the market. PNNL is developing a small, lab-scale prototype of its system, and the project team has created a manufacturing method that can be used at larger scales. Visit Liu at the ADMA Products booth, or hear him pitch the technology to a panel of investors at ARPA-E's Future Energy Pitching Session, which runs 6:30-8:30 p.m. Monday, Feb. 25. Click here for more info on the pitching session.
New way to heat, cool electric vehicles reduces drain on driving range
The combustion engines in gasoline-powered cars generate a lot of heat, which is great for heating the passenger cabin in winter. But energy-efficient electric vehicles produce very little waste heat. Providing electricity for the same amount of heat used in gasoline cars would reduce electric vehicles' driving range by up to 40 percent. PNNL engineer Pete McGrail is leading a team that includes the University of South Florida to develop a material called an electrical metal organic framework, also called an EMOF, for electric vehicle heating and cooling systems. The material would work as a molecular heat pump that efficiently circulates heat or cold. By directly controlling the material's properties with electricity, their design is expected to use much less energy than traditional heat and cooling systems. A 5-pound, EMOF-based heat pump that is the size of a 2-liter bottle could theoretically handle the heating and cooling needs of an electric vehicle with far less impact on driving distance. While using a unique testing system that applies voltage to the material, the team observed for the first time an EMOF transitioning from an off, or insulating, state to an on, or semiconducting, state. The transition demonstrated the project's premise, coincided with a change in the material's crystal structure and was completely reversible. The team is now making other EMOFs with similar switching abilities and higher adsorption capacities that improve performance in an electric heat pump.