September 1, 2007
More from Less
Can society get through the 21st Century with its standard of living and the environment reasonably intact? The answer to that question depends greatly on energy – how it is produced and how it is used. Convergence asked experts at UC Santa Barbara for their view of the future, with a focus on the role of new technologies that can help us use energy more efficiently.
Will LED’s Light the Way?
The future looks bright to advocates of solid state lighting, a technology in which semiconductors called light-emitting diodes (LEDs) take the place of incandescent or fluorescent bulbs. LEDs are already common in cell phone displays, flat-panel TVs, traffic lights and control panels on consumer appliances. They are quickly taking over the flashlight market. Not so many years from now, they could be illuminating just about everything, from homes and offices to streets and stadiums.
That’s the scenario mapped out by engineers at UCSB’s Solid State Lighting and Energy Center (SSLEC), one of the world’s key sites for LED research. Led by UCSB Materials professors Shuji Nakamura (inventor of white, blue and green LEDs as well as the blue laser) and Steven DenBaars, SSLEC develops new LED technologies and works with companies to commercialize them. “A lot of excitement has occurred because the white LEDs we have developed are more efficient than fluorescent lighting and 10 times more efficient than incandescent,” says DenBaars. “I think within five years we could definitely be the dominant technology.”
The incandescent bulb, little changed in its basic design since Thomas Edison devised the first commercially practical electric light nearly 130 years ago, does seem to be on its way out. It turns only 1% to 4% of its electricity into light (much of the rest goes into heat), while fluorescents achieve efficiencies of up to 25% and LEDs can top 50%. It’s being pushed aside by the rising cost of electricity and promotion (by utilities and governments) of an affordable alternative, the compact fluorescent lamp (CFL). The real question now is what will take its place for the long term. LEDs are more energy efficient than CFLs – about three times more, DenBaars says – but they are also much more expensive. LED bulbs are now about 10 times as expensive as compact fluorescents with comparable light output.
At its current price of around $50, an LED that puts out the equivalent of a 60 watt incandescent would take about five years to return its cost in energy savings. “We need to get that [recovery period] down to something on the order of one year,” says DenBaars. But he says this shouldn’t be all that difficult for LEDs, if they behave as other semiconductors do. Like the fabrication of computer chips, the making of LEDs requires a big up-front investment in manufacturing technology. But once the expensive infrastructure is in place, LEDs can be produced in huge volume for little added cost. DenBaars says a new semiconductor typically falls 50% a year in price. If the same happens for LEDs (and assuming that CFLs don’t fall almost as fast), they could well hit their competitive price point early in the next decade.
DenBaars, Nakamura and their colleagues at SSLEC are also trying to boost the LED revolution by making the devices more efficient, not just cheaper. Their near-term target is an LED that can turn at least 60% of its electricity into light; their ultimate goal is to raise the efficiency level to 80% or more. One thing holding them back from that goal is the relatively weak performance of green LEDs. White LED light is made up of combined hues from different semiconductors, and DenBaars says researchers so far have not been able to make a semiconductor that puts out green light as efficiently as red and blue LEDs can. “If we could develop a really efficient green LED, that would raise the efficiency of white LEDs,” DenBaars says. “Then you could start talking about LEDs that are four to five times more efficient than fluorescent.” According to the SSLEC, about 22% of America’s total electrical output goes into lighting, so the potential of these advanced LEDs is clear. A nationwide switch to these lights could have a huge impact on energy use and carbon output. If the people at SSLEC are right, it’s not far around the corner.
Post-doctoral student Hisashi Masui, Professor Steen Denbaars, Professor Shuji Nakamura, and graduate student researcher Natalie Fellows
Toward Leaner Computing
The role of computers in the overall energy picture is complex. As direct users of power, they are minor players. By one U.S. Department of Energy estimate, about 3% of the electricity used in buildings goes into computing. That’s far below the consumption for lighting, appliances, electronics, refrigeration or space heating and cooling. On the other hand, computers are crucial to energy efficiency and conservation. To cite just a few uses, they boost the fuel economy of cars and aircraft, manage power grids and, through the Internet, enable people to work together without the need for energy-burning travel. Researchers say computers could do even more energy-saving tasks if they could be made smaller, more rugged and more powerful. Tiny embedded computers in automobile engine blocks, for instance, could control fuel use more precisely than the devices now used with fuel injection and exhaust systems.
The challenge here is to make more efficient use of space as well as energy. Fred Chong, UCSB professor of computer science and head of the university’s computer engineering program, notes the shrinking of circuitry on computer chips is reaching its theoretical limits – at least until new technologies and architectures come along. “The reason we’re not using more energy [in computing] is not primarily because the world does not have more energy to give us,” Chong says. “It’s because heat limitations will not let us get more energy into that little chip.” One aspect of computing where energy efficiency could improve is in the internal power sources – the transformers that convert electricity from the grid into current for computing. “Because of other design constraints, computing devices are actually quite efficient,” Chong says. “What’s inefficient is the transformer. That’s what the computer industry is trying to force the [power source] manufacturers to fix.”
Chong sees new technologies on the way that “promise to revolutionize computing” by breaking the space constraints on chip design. One of these is the development of carbon nanotubes, which he calls “the wonder material of the new century,” with “very nice properties in terms of how small they are and how they conduct electricity.” But don’t expect most computers to use less power, he says. “You’re going to be designing chips that use about as much power, but we’re looking at putting more performance into that constraint.”
One new type of computing, still early in its experimental stage, can use less energy than the CMOS (complementary metal-oxide-semiconductor) technology in use today. This is quantum computing, which operates by switching the quantum states of particles rather than by moving electrons. “Quantum computing doesn’t fundamentally require energy dissipation,” says UCSB Physics Professor John Martinis. Classical CMOS computing uses energy and throws off heat, but quantum transitions conserve energy. If a particle goes from one state to another and back again, the net energy use is zero.
But the real payoff from quantum computing may come from its ability, at least in theory, to vastly expand processing power. Martinis, a superconductor specialist who has been working on quantum devices for several years, points out that the CMOS transistor has only two states, on and off – or 0 and 1. A quantum transistor has greater possibilities since in quantum theory a particle can be in two states at the same time. That allows parallel processing of many input states without requiring more hardware. Martinis suggests that quantum computing could even be used to build “less power-hungry classical computers” – similar to current models in their design, except at the level of the individual transistor. That goal, not to mention the prospect of wholly new computer design based on quantum theory, is still far off. Martinis and fellow researchers are still trying to build a quantum transistor integrated into a circuit capable of simple calculations. He says the state of quantum computing is where classical computing was in the early 1950s: “This is really long-term research, but it has important practical applications.”
If You Build It, Will They Buy?
It takes more than new technology to create an energy-efficient future. Even the best science will have no impact unless it finds its way into widely adopted products. Innovations such as LED lamps, hybrid (or hydrogen) cars and solar cells all could have great benefits to human well-being and to the environment, but not if they remain niche-market items, bought only by the greenest among us. At some point, they have to make a compelling “buy me now” case to ordinary consumers and most businesses.
This is where it’s essential to pay attention to economics – specifically environmental economics, the specialty of Charles D. Kolstad, a professor in UCSB’s Donald Bren School of Environmental Science & Management.
Some existing energy-efficient technology sits on the shelf because of cost and quality issues, Kolstad says. “The problem often isn’t that something is physically impossible. Usually it’s just too expensive” – and not quite good enough to make consumers want to switch. Kolstad cites the case of compact fluorescent lamps (CFLs), which he notes “have been around a long time” without being widely adopted by consumers. “Some people who are technologists say, ‘Why don’t people replace incandescents with these things?’ Well, they just haven’t worked as well. Sometimes the color is off. Sometimes they’re not very bright.” CFLs have improved and are starting to take off now, but they’re getting help from subsidies (courtesy of utility companies) and regulations pushing their use.
As for solid state lighting – LEDs – Kolstad sees these as “the light of the future, but the fit with consumer needs has to improve and the price has to follow.” Fuel-efficient cars such as hybrids, he says, will be a harder sell as long “you have low prices of gasoline” (and he considers $3 a gallon still relatively cheap). Kolstad thinks solar cells may make their case on cost alone, with quality and performance issues less significant. Rising electricity rates and the falling cost-per-watt of photovoltaics will drive demand. But for solar power to become “a big part of the solution,” it will have to overcome a fundamental feature of solar – it only works when the sun is shining.
So what works? Kolstad cites the recent history of batteries as a case in which demand aligned with technology to produce big gains in efficiency. Consumer demand for more compact cell phones with more features other than basic calling drove engineers to develop much lighter, smaller, higher-capacity battery technology. “We tend to forget what phones were like 15 years ago,” Kolstad says. “They were like bricks we were carrying around.” Demand for efficiency in cars is more difficult to produce. The most direct way is to impose a tax that sharply raises gas prices, but Kolstad notes that this is “a very hard thing to do in the U.S.” That leaves the regulatory option – tightening fuel economy rules – with help from a gas guzzler tax. It takes higher prices to make people conserve, Kolstad says, but fuel economy standards alone advance energy efficiency and “still do a lot of good.”