2019年5月29日 星期三

Climate Fwd: The best way to boil water

Also this week, millennial attitudes about climate change.
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Wednesday, May 29, 2019

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Tyler Varsell
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By Tik Root
There are seemingly endless reasons to boil water. But how to most efficiently achieve the task has long been up for debate.
Tom Murphy, a physicist at the University of California San Diego put the various theories to the test in 2012. "I thought the microwave would be quite good," he said in a recent interview. He thought the same of electric kettles, but was more skeptical of the stovetop option, though he decided to test that, too.
Dr. Murphy focused on boiling water, but stovetops and appliances are used for heating up all sorts of things — and they can use significant household energy — so his experiment helps underscore how small changes might boost efficiency.
Taking readings from his electric meter, and rigging a laser to monitor his gas usage, he calculated how much of the energy actually went to heating the water, versus dissipating along the way. "You have all these loss channels," he said. Minimizing that loss means using fewer resources and likely emitting fewer climate-changing emissions.
As Dr. Murphy expected, the gas stovetop was not very efficient. With the largest burner on full-blast and no lid on the pot, he found that only about 15 percent of the natural gas being burned was converted to heat in the water. If you add a lid and use a small burner (which takes longer), you can potentially double that number but, he said, "the gas stove tops out at about 30 percent."
While Dr. Murphy did not test an electric stovetop, other estimates tend to rate their efficiency considerably higher than gas ones. But Dr. Murphy said that electric stoves are also conditional on a host of factors — from burner geometry to the cleanliness of any reflective plates.
The microwave was a bit better; it clocked in at about 43 percent efficiency. But the figure was still about half of what Dr. Murphy had hypothesized. The kettle came the closest to matching its pre-experiment hype.
Most kettles, Dr. Murphy said, locate the heating coil directly in the water and have at least somewhat insulated sides, which both reduce energy loss. This enabled his setup to hit 70 percent efficiency. But those findings come with a few major caveats.
Foremost is that efficiency largely depends on your energy source. By the time electricity from fossil-fuel-powered plants has reached your home, Dr. Murphy notes, it's already lost about 60 percent of its energy (some estimates have that number higher). That scenario, he said, could drastically hinder the performance electric stovetops and microwaves.
Kettles suffer from the same electricity issue — but also come with additional drawbacks that Dr. Murphy says can cause their efficiency to vary widely. The auto-stop function, for instance, often runs much longer than is necessary, which wastes energy. And people tend to overfill kettles. "Habitually, you're just heating a lot more water than you need to be," he said. "In practice, you're not likely getting any better than a microwave."
To get the most out of your kettle, Dr. Murphy says you should only boil as much water as you need and monitor the boiling point, so you can manually shut it off.
Dr. Murphy also looked into starting with hot water from your tap as a way to improve results (the myth that cold water boils faster has been thoroughly debunked). He found that it can probably help, because hot water systems are relatively efficient. But because a certain amount of the hot water will inevitably get left behind in your pipes, unused, the benefits of starting hot are greater when you're boiling large pots of water for, say, corn on the cob.
Dr. Murphy didn't test methods such as induction cooktops, which others have since found to be quite efficient. Technology is always changing (scientists in Oregon, for example, have developed new surfaces that could improve boiling efficiency) but he doesn't see any breakthroughs on the horizon that will make boiling water miraculously less energy intensive. The biggest thing individuals can do, he said, is be vigilant about our own habits.
"You just have to care about it," he said. "You have to pay attention."

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A group of young protesters, part of the global movement

A group of young protesters, part of the global movement "Fridays for Future" against climate change, in front of the White House this May. Eric Baradat/Agence France-Presse — Getty Images

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John Schwartz

John Schwartz

@jswatz
Younger Americans aren't happy with the Trump administration's handling of climate change, according to a new survey from researchers at the University of Chicago.
The report found that 82 percent of Americans 18 to 36 care "a great deal" or "some" about climate change; among Republicans in the survey, that figure was 73 percent. By comparison, a 2018 survey from the Yale Program on Climate Change Communication and George Mason University asked a similar question to a group representing the general population and found that 61 percent of Americans say they are "worried" about global warming.
The GenForward Project conducts regular polls of the generations known as Millennials and Generation Z. By focusing on age and building a relatively large survey population of 3,257 people, the researchers could measure differences in opinion by race, ethnicity and political affiliation, said Cathy J. Cohen, chair of the department of political science at the university and principal investigator for the project.
With so much concern about climate change from this younger group, it's not surprising that 70 percent of those surveyed said they disapprove of the way President Trump is handling the issue. Among Republicans, that figure is 44 percent; but when Mr. Trump is not mentioned and those same Republicans were asked whether the "federal government is doing enough to reduce the effects of global climate change," those saying it's not enough jumped to 56 percent. "When you take his name off of the policy," Dr. Cohen said, more of the young Republicans say "we're probably not actually doing enough."
These results are fairly consistent with other recent surveys of climate attitudes by the Pew Research Center and the Yale Program on Climate Change Communications, said Anthony Leiserowitz, the director of the Yale program; he said adult whites, too, "generally have lower climate beliefs and attitudes than minority respondents. Republicans generally have lower climate responses than Democrats," he noted.
Will climate change bring millennials to the polls?
When asked how important the issue is in choosing who they will vote for in 2020, only 18 percent said it was their most important issue, while 43 percent said it would influence their vote. Among racial groups, those most likely to say it would influence their vote were Asian-Americans (50 percent), then Hispanics (45); 41 percent of white and black respondents said it would. Of those saying it was the most important issue, 24 percent of Hispanics said it was, followed by 18 percent of Asian-Americans, 17 percent of blacks and 15 percent of whites.
Ultimately, Dr. Cohen said, "it's an important issue that they say will influence their vote, but it won't determine their vote."
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