Evaporative cooling plus drying with desiccants equals cool air for less cost.
Keeping air cool in homes and offices this summer will be expensive–about 5 percent of the energy used in the United States each year goes to running air conditioners. But researchers at the U.S. National Renewable Energy Laboratory (NREL) in Golden, CO, have come up with a new air-conditioner design that they say will dramatically increase efficiency and eliminate gases that contribute to global warming.
“The technology we have today is nearly a hundred years old,” says Eric Kozubal, a senior engineer at NREL. Kozubal and colleagues have come up with an air conditioner that combines evaporative cooling with a water-absorbing material to provide cool, dry air while using up to 90 percent less energy. The desiccant-enhanced evaporative, or DEVap, air conditioner is meant to addresses the old complaint, “It’s not the heat; it’s the humidity,” more efficiently.
Evaporative cooling–blowing air across a wet surface to promote evaporation–has long been used in so-called swamp coolers. A method called indirect evaporative cooling improves on this design, dividing air into two streams, which separated by a polymer membrane. Water is passed through one airstream, making it cooler and wetter; the cool air cools the membrane, which in turn cools the air on the other side without adding water.
But air can only hold so much water vapor, so in humid climates the effect is limited. On a 32 ºC day in Houston, Kozubal says, evaporative cooling may only bring the temperature down to about 27 ºC. Ideally, to provide a comfortable building, an air conditioner should cool air to 13 or 16 ºC.
NREL overcomes the humidity problem by adding another step, the use of a material known as a desiccant that absorbs moisture. NREL uses a liquid desiccant, a syrupy solution of lithium chloride or calcium chloride, about 44 percent salt by volume. In this setup, another membrane separates the desiccant from air traveling through a channel. The polymer membrane has pores about 1 micrometer to 3 micrometers in diameter, big enough that water vapor passes through easily while the salty liquid stays put. The membrane is also coated with a Teflon-like substance to repel liquid water. The desiccant pulls moisture from the airstream, leaving dry, warm air. Then it’s back to indirect evaporative cooling: in a second channel, water evaporates to cool a secondary airstream, which in turn cools the first airstream, and out comes cool, dry air.
“I think it’s very promising,” says Anthony Jacobi, codirector of the Air Conditioning and Refrigeration Center at the University of Illinois at Urbana-Champaign. “I don’t believe the idea of integrating these technologies is very new. Doing it successfully may be.”
What’s new, Kozubal says, is a design that manages to merge evaporative cooling and desiccant drying into a cost-effective system. “It makes this type of air conditioning viable for commercial and residential processes for cooling,” he says.
The industry is working on a variety of methods to improve the efficiency of air conditioning, Jacobi says, from the use of heat exchangers to improvements in the compression systems of traditional machines. “It’s an area of great importance to the nation, because about a third of our nation’s energy use is in buildings.”
The U.S. uses about 100 quadrillion British Thermal Units each year, according to the U.S. Energy Information Administration. Up to 40 percent of that is used in buildings, with about 5 percent going to air conditioning. Kozubal says his system could cut that in half in less-humid areas and by up to 90 percent where humidity is high. “When you talk about a technology that can save 2 to 3 percent of the nation’s entire energy supply, that’s quite a lot,” he says.
It’s no secret that buildings can be energy hogs, and putting them on a power diet is quicker and cheaper than reducing green house gas emissions via solar panels. One of the latest investments in this space is coming from none other than Uncle Sam, and the Department of Energy announced today that it is putting more than $76 million into 58 building efficiency projects.
With money from the American Recovery and Reinvestment Act, the DOE wants new technologies and job training programs for building equipment operators, energy auditors and the like. The DOE estimates that 114 million households and more than 74 million square feet of commercial space account for 40 percent of the energy use and 39 percent of the carbon dioxide produced in this country.
If the energy bill dies in 2010 — as it almost certainly will — climate change reform enters an indefinite purgatory, and the United States’ broken energy policy rolls along, fuming all the way. When I expressed sadness at the prospect of the American Power Act’s death, commentators noted that we can’t expect to reduce global emissions without getting big countries like China on board. They’re right. It made me wonder whether China might be “on board” with green tech and carbon pricing already. To know more, I spoke with Julian Wong, an expert in Chinese energy policy at the Center for American Progress.
My readers are always asking how climate change legislation in the U.S. could impact China’s energy policy. In broad strokes, how is China moving on green energy already?
It’s across the board. In China they have for several years already realized that their direction is not sustainable. They have undertaken some of the most ambitious programs in energy efficiency and renewable energy deployment in the world. They’ve created medium and long term plans and set national numerical targets, such as producing 100 to 150 Gigawatts of wind energy by 2020. There is a national goal of reducing energy consumption per unit of GDP over the 2005 to 2010 term by 20 percent. In the run-up to Copenhagen they promised to achieve a 40 percent reduction in carbon intensity….
How would the United States passing something like the American Power Act encourage other countries to act?
If America shows its seriousness with a national strategy to develop green tech and cut emissions and put a price on carbon, that will remove a lot of the excuses for countries who’ve been inactive. We can’t reestablish leadership in the international climate talks without legally binding domestic policies. Until we do that, we’re in a really awkward position where we’re getting developing countries to act while we’re historically the largest emitter of gases. It’s hypocritical. But the moment that we act, it removes the excuses and I think it will have a positive impact.
When President Obama called this week for a “national mission” to expand the use of clean energy and increase American energy independence, Chinese officials might have nodded knowingly. The government here is already far along in drafting energy legislation with similar goals for China, according to Chinese officials and executives.
Like the energy future that Mr. Obama briefly described in his Oval Office address on Tuesday, the Chinese proposal calls for more reliance on renewable energy and greater emphasis on energy conservation, two drafters of the legislation said. But because this is China, there are big differences, too. In contrast to the Obama vision, the plan here preserves a central role for coal “” the dirtiest fossil fuel in terms of emissions of greenhouse gases, but a resource that China has in abundance.
A well-worn management mantra observes, “If you can’t measure it, you can’t manage it.” A United Nations research effort known as The Economics of Ecosystems and Biodiversity, or TEEB, suggests that this maxim can also be applied to the earth’s ecosystems “” habitats like forests, oceans and tropical mangroves.
For example, each year, roughly 30 million acres of forest worldwide are cut down, a combined area that is roughly the size of Greece, according to Pavan Sukhdev, the group’s study leader and a former senior banker at Deutsche Bank. While the forest products that the cutting yields provide some short-term gain, in the long term we lose “services” provided by the forest like carbon dioxide storage, clean air, protection from floods and soil erosion, food and natural medicines.
The problem, Mr. Sukhdev asserts, is that we have failed to put a price on those services and analyze the markets for them. If people first measure their economic value, his group argues, policies can be adopted that allow for better management of those ecosystem services, like creating markets where the use and the supply of the services can be traded.
The Environmental Protection Agency says it will wait until this fall to decide whether U.S. car engines can handle higher concentrations of ethanol in gasoline. The agency had been expected to decide by this month whether to increase the maximum blend from 10 to 15 percent.
The EPA said Thursday that initial tests “look good” and should be completed by the end of September. A decision will come after the Energy Department completes the testing of the higher blend on vehicles built after 2007. The ethanol industry has maintained that there is sufficient evidence to show that a 15 percent ethanol blend in motor fuel will not harm the performance of car engines. But the refining industry, small engine manufacturers and some environmental groups have argued against an increase.
Solar company Solyndra has canceled its plan to raise money through an initial public offering on the stock market, opting to raise money from existing investors instead. The Fremont, Calif.-based company on Friday filed a “registration withdrawal” request with the Securities and Exchange Commission, saying that it has changed course due to “adverse market conditions.”
On Thursday, Solyndra said that it has raised $175 million from existing venture capital and private equity investors. “Given the ongoing uncertainties in the public capital markets, we elected to pursue alternative funding from our existing investor base. This funding allows us to address strong customer demand by maintaining our aggressive growth plans,” Solyndra CEO Chris Gronet said in a statement.
Honda may have come up with the first fun hybrid car. The Insight, Prius, Camry, and Fusion are all very practical hybrids, and Lexus makes a few comfortable cruisers. But the 2011 Honda CR-Z made us want to drive fast. We wanted to find the windiest road around and torture it through the corners.
Honda obliged during our preview drive, prescribing a twisty route north of San Francisco we’ve previously used to test the BMW M3, Porsche 911, and Audi R8. Those cars had it all over the CR-Z for power and speed, but the plucky little CR-Z showed its stuff in the turns. Honda also set out an autocross course so we could really thrash the CR-Z, a test that we haven’t previously seen a hybrid put through.
The CR-Z certainly has its quirks. In other markets it is produced with 2+2 seating, but Honda removed the rear seats for the U.S., launching it as a two-seater. We assume Honda thinks Americans are too fat to use the tiny rear seats. We’re not going to argue the point.