Solar power
The biggest knocks against solar and wind power are that they can’t be done on a massive, city-powering scale, and that the energy they make can’t be stored for a cloudy day, the middle of the night or a late-afternoon demand surge.
But turn table salt into hot lava and the problem is solved. Scientists have learned that heated, liquid salt is “basically a thermal coffee carafe for the sun,” said NREL’s Mark Mehos, an expert in concentrating solar power.
Massive fields of mirrors — NREL helps develop the most reflective surfaces — concentrate the sun on pipes or towers filled with molten salt. The salt heats to 734 degrees and transfers the heat to pipes filled with water. The water turns to steam strong enough to drive utility-size electrical turbines for power generation.
The key is that molten salt can store up to seven hours of sunshine-generated energy for up to a week at a time. The American Southwest and northern New Mexico are some of the best places in the world to locate such power plants, and NREL works on the technology for heat storage and the coatings that make solar panels more efficient. The cost of the power is still higher than everyday electricity, but competitive at “peak load” times of the day.
“Ironically, you’re using solar heat to create air conditioning,” Mehos said. “Oil at $90 a barrel does a lot of interesting things” to technology.
Plug-in hybrids
New cars sold in the U.S. have been stuck at the same gas mileage since 1993 — about 20 miles to the gallon. The popular alternative, hybrid cars, add mileage by combining a gas engine and batt-eries that recharge from the spin of the wheels.
Plug-in hybrids are the next wave, with General Motors and Toyota now competing to see who will get one on the public market before 2010. True to their name, plug-in hybrids have a gas tank but are also plugged in overnight at home, charging a much more powerful lithium-ion battery pack. (The batteries are charged, of course, with electricity generated primarily by coal-burning power plants. But that centralized pollution is more easily attacked, and coal can be replaced by solar, wind or hydrogen utilities.)
The plug-in format allows the cars to run on batteries more and gasoline less, stretching the mileage in an SUV, for example, from 17 to 25 per gallon. That’s a nearly 50 percent improvement, and with so many more SUVs on the road, would produce huge raw fuel savings.
NREL is working with General Motors and other Detroit companies to bring the cost down — current estimates for plug-in technology adds $20,000 to $40,000 to a $20,000 base price. Key programs at NREL pack more battery storage in smaller spaces, and rewrite the controlling software for the car computers to switch more intelligently between gas and battery.
Biofuel/switchgrass
It’s a simple as this: Passenger cars account for 40 percent of U.S. oil consumption, and a large share of global warming emissions. Ethanol made from corn kernels can replace much of that, but it takes a lot of energy to produce this alternative energy, and the pollution savings are not great.
Refiners can also make ethanol from everything-but-the- kernel, using enzyme and other chemical reactions to produce fuel from corn cobs, corn stalks, fast-growing switchgrass and waste wood chips. Very little energy goes in, and very few emissions come out. The U.S. now needs NREL to greatly improve how this “cellulosic” ethanol is made in order to fulfill steep federal mandates for alternative fuels.
“Right now, the cost of cellulosic ethanol is twice the cost of grain ethanol. The goal is to make it cost-competitive with grain ethanol by 2012,” said Jim McMillan, the principal chemist at NREL’s biorefining lab. McMillan spends his days watching over fermenting tanks and carts of chopped cornstalks, looking for enzymes that can chew them up faster.
McMillan’s job gets easier as the cost of corn rises — expanding ethanol producers are taking so much feed corn out of the food chain to make fuel, the grain’s price has more than doubled in two years.
The advantage in corn stalks or wood chips is once ethanol refiners have cooked the key chemicals out, they can use the remaining waste to fuel the refinery’s boilers instead of burning natural gas.
Home energy
Roof panels painted dull brown. Water heaters wrapped in better insulation. The materials aren’t exactly sexy, but they work, and NREL helps put home energy- saving products directly on the store shelves.
Buildings consume 40 percent of the energy used in the U.S. Wal-Mart’s store on Tower Road tries out new designs from NREL, including “the most efficient solar heater in the world,” a simple black roof panel that pre-warms air sent into the ventilation system.
NREL has helped design and test new solar hot-water heaters, now for sale, and its research has helped slash prices from $5,000 to $1,000. Precisely ground skylight lenses distribute natural daylight more efficiently. A new air conditioner — that NREL can’t talk about until patents come through — removes the “latent” heat, or humidity, from the air of cities like New Orleans, rather than just attacking the “sensible” heat. These efficient “desiccant” machines may be on sale in 5 to 10 years.
And a massive infusion of federal lab-building money for NREL — $107 million last year alone — will construct green buildings that use little or no outside energy. “In any building, it’s no one thing. There’s no silver bullet solution,” said Ron Judkoff, director of NREL’s buildings center.
Hydrogen
If ethanol and solar dominate the next decade in alternative energy, hydrogen owns the future, according to NREL principal hydrogen scientist John Turner. “It’s the tie between energy and transportation,” Turner argues. “It both produces energy and runs transportation. This toy has everything in it. Let’s see the nuclear guys do that.”
In its simplest form, hydrogen energy is created when a renewable source like solar or wind power produces an an electrical current that separates hydrogen from water. Hydrogen can then be stored in tanks — at a utility, or alongside a home, or inside a car — and used in fuel cells to run anything demanding power.
“The technology is ready to go — end of story,” Turner gloats. But hydrogen requires an expensive overhaul in the energy system which is now based on other forms of energy.
“It’s a destructive technology.” Harnessing it means new power plants, new pipelines and delivery systems, modified cars, renovated or newly built homes.
