An unscientific survey of the social networking literature on Sandy reveals an illuminating tweet (you read that correctly) from Jonathan Foley, director of the Institute on the Environment at the University of Minnesota. On Oct. 29, Foley thumbed thusly: “Would this kind of storm happen without climate change? Yes. Fueled by many factors. Is storm stronger because of climate change? Yes.” Eric Pooley, senior vice president of the Environmental Defense Fund (and former deputy editor of Bloomberg Businessweek), offers a baseball analogy: “We can’t say that steroids caused any one home run by Barry Bonds, but steroids sure helped him hit more and hit them farther. Now we have weather on steroids.”
Constructing green charging stations is a step in the right direction, but this is a hard problem. I think one of the problems is that we don’t appreciate the scale of the problem of refueling infrastructure. Part of this is because there’s been a century of build-out for support of internal combustion engines, and this is an attempt to hit a critical mass in a much shorter time.
The Tesla supercharger stations have a transfer capacity of 100 kW and shoot for a 30 minute turnaround, which is supposed to provide 3 hours of driving. That’s 180 MJ of energy (50 kWh). How does it compare to gasoline? Gas contains around 132 MJ per gallon, and the EPA allows gasoline pumps to transfer no more than 10 gallons per minute, which gives us a transfer rate of 22 MegaWatts, though actual pumping speeds, and thus rates, are likely somewhat smaller. Still, 10-15 MW is a lot of power, and that’s what you’re transferring when you fill your tank.
One thing that electric cars have going for them is that they are significantly more efficient than gasoline — there’s an inherently higher efficiency and technology like regenerative braking, plus the ability to just turn off rather than idling. Overall, electric cars are around 5x as efficient as gasoline-powered vehicles. Good thing, too, because otherwise we’d have close to a 1:1 charge:travel time, and nobody is going to put up with that.
So we can fill up a tank of gas in just a couple of minutes, and it takes more than an order of magnitude longer for electric, for a more limited range. Let’s look at this from another perspective: waiting for a space to clear at a gas station is annoying even when it’s a few minutes, so waiting for a fill-up that takes 30 is probably a nonstarter. Which means that you are going to need proportionally more fill-up bays at each station, relative to the number of cars on the road. Right now that capacity is not a problem, with so few cars, but it’s an obstacle to wider adoption.
If you have a station capable of charging up multiple cars, you need to be able to deliver the power. For every 10 cars at once that means a MegaWatt of electricity. Perhaps that remains constant — if you can cut the charging time in half you deliver twice the power but don’t need as many charging stations, and you won’t be operating at peak capacity, so that doesn’t mean you need 1 MW coming in — you can store electricity when you have lower demand. But you have to generate all that electricity from solar, though you at least have the advantage of staying DC to charge up a car — no inverter losses as you’d have for a home system running your 60Hz loads. But how many cars are you going to handle? 100 a day? That’s 5000 kWh, and solar might generate 5-10 kWh/m^2 each day, (or even less) depending on location and time of year. That’s a 1000 m^2 solar array for the smaller value, and you probably need more in case the weather is bad for more than a day lest you tell your customers “We’re out of sun” very often. If you’re out, they are stranded, so I imagine there will be emergency generators (running on biodiesel, presumably). The array size may not be a problem for stations away from cities. You have the space, and don’t need to have a grid connection, so you are freer to put these where you want. In more occupied space, you’d tap into the grid if you needed to, though that’s not “green” and defeats (much of) the purpose of having an electric car. But being stranded is not going to be an option.
By now we’re pretty used to being the product, as many of us participate in online activities like Facebook or Twitter, and/or photo-sharing sites, where we provide the content. (On some of those sites, what we post actually becomes the property of the host. Read carefully!) Here’s another example of being the product:
Each tile has a capacity of 6 watts, but in order to use the tile’s full capacity, there needs to be a constant flow of about 50 steps / minute.
The reality is that the tiles are seeing about 5 steps / minute, and on a good day, the kinetic sidewalk will generate about 75 watt-hours of electricity. This is equivalent to powering an old 60-watt incandescent lightbulb for about 1 hour and 15 minutes.
Let’s start with the obvious: one could take the view that this is stealing. Someone is taking work you (the actual physics definition of work, at that) and using it without paying you. It’s also being advertised as being green and self-sustainable. It also needs to be cost-effective. Is it?
Let’s run the numbers. The pad flexes ~5mm when you step on it, so that’s about 5 Joules of work for a mass of 100 kg, so that’s roughly in agreement with the 50 steps/min giving 6 Watts, assuming high efficiency. 75 W-h is 270 kJ of energy. At an electricity rate of $0.12 per kWh, this represents a penny of electricity.
The device has to be less than 100% efficient and your body’s conversion of food into the energy being harvested certainly isn’t (I’ll assume around 25%), so at 4.18 kJ per Calorie, the people providing this energy collectively burned about 270 Calories, which came from the food they ate. The cost of that food can vary widely, but it’s going to be on order of a dollar, making this system’s cost efficiency about 1%. (This won’t change at higher power production, either) And here’s where (and why) the claims of “green energy” fall apart. Touting human power as green is dubious, because you don’t know where the food came from, but odds are it’s not all that “green”, and to tout this as a replacement — at 1% efficiency — means that the people providing the energy need to have 1/100 of the carbon footprint of the raw electricity. Transporting the food, preparing it, etc. has to be greener than the energy it replaces by a factor of 100, and there’s no way it is. This is a misdirection, moving the carbon footprint issue out of immediate sight, asking us to pay no attention to the carbon footprint behind the curtain. Human power is not green — the only time it works is if you are harnessing energy that would otherwise be wasted, similar to regenerative braking on electric cars.
Is it cost-effective? I couldn’t find a credible price anywhere, save for a promised target of $50 per tile once production ramps up. Installation is probably the largest cost, along with some infrastructure of wiring, batteries and an inverter. At the target traffic load giving an output of 6 Watts, even if the traffic were present all day long, that’s 1 kWh per week per tile. At $0.12 per kWh saved, that’s just barely $6 a year in electricity savings. The tiles were installed at a tube station at the Olympics and generated just 20 kWh from 12 tiles. The olympics ran 16 days (the story says two weeks); it’s ballpark agreement either way. 20 kWh is $2.40 of electricity.
Unless I’m missing something, there’s no way this is cost-effective. You can pay for it out of your advertising budget, raising awareness of, well, something, since it’s not green, which means it’s just a gimmick.
It takes far less energy to recycle an aluminum can than to make one from scratch – recycling 40 Aluminum cans is the equivalent of saving a gallon of gasoline. One problem is that not all of the can is Aluminum.
[R]ecycling the cans turns out to be harder than it looks, because the basic soft drink or beer can is actually made of two kinds of aluminum. The bottom and sides are made from an aluminum sheet that is strong enough to be stamped into a round shape without tearing. For the top, which must be stiff enough to help the can retain its shape and withstand the bending force when it is opened, can makers blend aluminum with magnesium.
Wow, four records! Keep your eye on this kid — he’s going places.
According to NOAA’s National Climatic Data Center, the spring of 2012 “was the culmination of the warmest March, third warmest April, and second warmest May. This marks the first time that all three months during the spring season ranked among the 10 warmest, since records began in 1895.”
All air trapped during this procedure is then directed through an electric cooling compressor situated behind the propellers. This contraption extracts humidity from the air, creating moisture which is condensed and collected.
One turbine can produce up to 1,000 liters of water every day, depending on the level of humidity, temperature and wind speeds, says Janin
Still pricey, however.
[Thoreau’s] journals offer an unparalleled phenological record — that is, a log of the timing of events, like a first flower or leaf growth. Looking back through Thoreau’s logs, as well as those of later botanists, Primack and Miller-Rushing found the first flowering date for 43 of the most common species has moved up by an average of 10 days.
[R]egardless, the analysis has been done; lead remediation is still a screamingly good deal. Lead remains one of the most common and harmful pollutants in the country; it’s often present in old paint and settles into soil, particularly in urban areas. One comprehensive study concluded that “each dollar invested in lead paint hazard control results in a return of $17–$221.” And that study focused on current, laborious methods of lead remediation. As it happens, scientists have developed a new, cheaper method — mixing fish bones into soil (!) — to absorb lead and render it nontoxic. Pretty cool stuff. Imagine what more research and funding could do.
Instead, federal funding for lead-poisoning prevention programs has been brutally slashed
I’m hoping the anti-spending reflex can be excised from our politics and replaced by the recognition that investment is a good idea. When the return on the spending exceeds the spending, it is a wise thing to do.
The elimination of lead from gasoline is a paradigmatic triumph of American environmentalism. A danger to health was discovered by scientists. Public-health advocates and greens pushed and pushed for decades, often futilely, to get the government to take action. When EPA finally cranked up efforts to do something about it, the agency was viciously attacked. Industry shills said it was an agenda to control Americans’ lives, driven by scientists who wanted research money and a cabal of extreme environmentalists. They said there were no viable alternatives to lead and the regulations would raise gas prices and destroy the economy. They paid their own scientists to produce counter-evidence. They flooded politicians with money.
Gosh, sound familiar? The EPA prevailed, but these tactics no doubt delayed the result and increased the damage done.
Generating capacity is, however, only one side of the story. Storage systems are rated not only by their power, or how fast they can crank out energy (measured in gigawatts), but also by the total amount of energy they store (measured in gigawatt-hours). A facility with an energy capacity of one-gigawatt that can only supply electricity for 10 minutes would not be very helpful; in an ideal world it could do so for, say, 100 hours, thus storing 100 gigawatt-hours. Building up new pumped hydro-facilities similar to existing ones would probably help in all but the most disastrously long of wind lulls. For those worst-case scenarios, we might still have to brace for rolling blackouts.
Of course, this simple calculation also assumes current consumption levels. How would we power all those electric cars that we’re supposed to be driving in the future?
Using some back-of-the-envelope-style calculations, Dr Smith, with help from physicist and Cambridge University colleague Dave Ansell, drew up a balance sheet of what’s coming in, and what’s going out. All figures are estimated.
One questionable part of the analysis:
“Nasa has calculated that the Earth is gaining about 160 tonnes a year because the temperature of the Earth is going up. If we are adding energy to the system, the mass must go up,” says Dr Smith.
[T]he Earth’s core is like a giant nuclear reactor that is gradually losing energy over time, and that loss in energy translates into a loss of mass.
But this is a tiny amount – he estimates no more than 16 tonnes a year.
The energy from decay should be included with the global warming — in order to count this as lost mass, the energy has to radiate away from the earth, or else the mass doesn’t change. Which means it’s all part of the global warming energy balance. But since it’s in the round-off error, whether they broke this out as a separate line item or not has little effect on the overall answer.