Sally Adee reports on a novel design for an energy generating station that runs on ocean swells. Oceanlinx, an Australian company, is developing a platform that is mostly submerged but has no moving parts below the waterline.
Jad Mouawad and Kate Galbraith review U.S. residential electricity consumption. While standards for white goods like clothes washers have reduced usage substantially, the consumer electronics industry has resisted calls for producing more efficient gear.
The biggest offender is the flat-screen television. As liquid crystal displays and plasma technologies replace the old cathode ray tubes, and as screen sizes increase, the new televisions need more power than older models do. And with all those gorgeous new televisions in their living rooms, Americans are spending more time than ever watching TV, averaging five hours a day.
As a result, televisions and set-top boxes accounted for 6% of electricity use in the residential sector in 2005, six times that for computers. A 42-inch plasma device consumes 275 watts.
Make no mistake: other, less sexy equipment still eats a lot of watts. Air conditioning (18%), lighting (16%), and refrigeration (9%) are the biggest wedges of the consumption pie.
I read about a program to convert marine waste—fishing nets and other gear—into energy. The claim is made that 1 ton of waste can power a household for 5 months. That number sounds high, but not completely unrealistic. Does it add up?
Well, a Department of Energy survey measures the typical American household’s consumption of electricity in 1993 at 9,965 kilowatt-hours per year, of which about half goes into heating and cooling, water heaters, and refrigerators, and the other half into other appliances. So 9,965/12 = 830 kWh per month.
Myself, I am somewhat more profligate, and I bought 16,290 kWh from Dominion Virginia Power for my all-electric home in 2008. Ah, but we read that mixed-fuel homes use less electricity than all-electric homes (as you would certainly expect); the average all-electric home burned 15,639 kWh/year in 1993.
At any rate, let’s use the 830 kWh/month figure, just to pick a number.
Now, how much energy can be extracted from something by burning it? Household waste has an energy density of 8 to 11 megajoules per kilogram. Bituminous coal, for comparison, comes in at 24 MJ/kg, wood at 6 to 17 MJ/kg, and gasoline at 46.4 MJ/kg. Plastics score in the coal-gasoline range. Let’s use 15 MJ/kg. Now for some conversions (with lots of roundoff):
1 ton of waste = 907 kilograms of waste
907 kg · 15 MJ/kg = 13,605 megajoules of energy
1 kWh = 3.6 · 106 joules, so
13,605 MJ · 1 kWh / 3.6 MJ = 3,780 kilowatt-hours per ton of waste
And our typical household will go through 830 kWh/month · 5 months = 4,150 kWh. So we’re in the ballpark, assuming the combustion of the waste is fairly efficient.
Makes me remember the can in the back yard of my grandparents’ house where we would burn the trash. How many watt-hours did we let escape?
Via Birding Community E-Bulletin, Narasimharao Kondamudi et al. report the processing of used coffee grounds (10 to 20% oil by weight) into biodiesel, as explicated by ScienceDaily. The authors estimate that 340 million gallons of biofuel could be produced annually; the grounds after oil extraction remain suitable materials for garden fertilizer, feedstock for ethanol, and as fuel pellets.
Via ArtsJournal, Steven McElroy reports from the launch of Broadway Goes Green, an effort sponsored by the New York mayor’s office and the Natural Resources Defense Council to reduce waste (paper, electricity, etc.) in the professional theater and promote a sustainable stage. Turns out that the effort is already underway.
The mayor’s office approached the Broadway League in March about working with theater owners to study the efficiency of their buildings and to find ways to decrease the load on the overburdened electrical grid of Midtown. “They were very surprised to learn that all of our theater owners were already in the middle of doing things on their own,” Charlotte St. Martin, executive director of the Broadway League, said of the city representatives.
Even though wind power is a green energy source that we’re right to feel enthusiastic about, it does have a cost that can be minimized. Different settings – shapes of ridgelines, prevailing wind patterns, migratory routes – mean that each new wind farm will present different hazards to birds. But with a little forethought and brain power, we can reduce the costs birds pay to satisfy our own energy demands.
A recent paper by Erin F. Baerwald et al. as summarized in Science Daily, suggests the cause of many bat fatalities near wind turbines: rather than direct collisions with turbine blades, bats die from barotrauma, internal injuries caused by sudden changes in air pressure. Unfortunately, the researchers don’t have ready suggestions to mitigate the pressure changes and hence reduce the kills.
Nature reporters Quirin Schiermeier et al. summarize the prospects for electricity produced with minimal carbon emissions by the leading candidates in alternative energy: hydro, fission, biomass, wind, geothermal, solar, and tidal and wave. In the authors’ estimation, the likely most productive sources, ones which could be built up in the coming decades to a terawatt of generating capacity each, are hydropower, nuclear fission (if the political climate changes), and wind. They are less sanguine about solar power:
In the middle to long run, the size of the resource and the potential for further technological development make it hard not to see solar power as the most promising carbon-free technology. But without significantly enhanced storage options it cannot solve the problem in its entirety.
For comparison purposes, on the consumption side, 18,000 TW-hours of electricity (about 40% of total energy use) were generated in 2005, which works out to an average constant comsumption of 2 TW. Actual worldwide generating capacity is higher, because no plant works flat out 24/7/365.
Alan Blinder proposes an economic stimulus measure that’s good for the environment as well: subsidized repurchases of aging, inefficient cars and trucks, targeted to the low-income households that need the money the most.
…a fourth possible goal. By pulling millions of old cars off the road, Cash for Clunkers would stimulate the demand for new cars as people trade up. It need hardly be pointed out that our ailing auto industry, like our ailing economy, could use a shot in the arm right now. Scrapping two million or more clunkers a year should help.
Amy Cortese spotlights Blaine Brownell’s transmaterial.net, a blog (and associated books) of green building materials and other technological innovations in construction. She singles out plans by Serious Materials to introduce EcoRock, a carbon-neutral gypsum board replacement.
A typical gypsum drywall plant consumes one trillion to two trillion B.T.U.’s of natural gas a year, according to [Kevin] Surace [of Serious Materials].
Later this year, his company—backed by $65 million in venture capital funding—plans to offer a zero-carbon drywall called EcoRock. It looks and performs like traditional drywall and will be priced comparably, but it uses no heat in its creation. Instead, the mix of ingredients, which Mr. Surace would not disclose but said were mainly materials diverted from landfills, are heated through a chemical reaction. “This is brand-new materials science,” he said.
Gasoline prices in the United States continue to be a bargain compared to the rest of the industrialized world, as a short article by Bill Marsh (accompanied by a chart) points out, part of the Times‘s collection of stories this Sunday about consumer energy costs. Back when we were kids, and gas was less than half a buck per gallon, it was explained to us that prices in Europe were much higher (and efficient cars more popular) because of higher taxes. Prices have risen a lot since then, but I was mildly shocked to learn that U.S. taxes haven’t kept pace. Of the current national average pump price of $4.00 a gallon, only 49 cents (12.3%) is taxes. By comparison, Canadians pay $5.09 per gallon and $1.26 (24.8%) in taxes; in France, the comparable price is $8.78, of which more than half, $5.06, is taxes.
Willie D. Jones reports on research (preliminary, apparently not yet published) by the Virginia Water Resources Research Center that compares various energy sources and means of power generation in their efficiency of water consumption. That certain high-tech darlings of alternative energy, like ethanol, are relative water hogs is less surprising than the wide spread of computed values, spanning four orders of magnitude. While natural gas requires only 38 liters of water per 1000 kilowatt-hours generated, biodiesel was measured at 180.9 to 969 kiloliters of water per 1000 kW-h. On the generation side, the range is from 260 l/kW-h for hydroelectricity to 31000 to 74900 l/kW-h.
Wu-Chun Feng and Kirk W. Cameron of Virginia Tech have initiated a new system of league tables for supercomputers based on energy efficiency, The Green500 List. They introduce the rankings in an article in the December, 2007 issue of Computer. The article abstract:
The performance-at-any-cost design mentality ignores supercomputers’ excessive power consumption and need for heat dissipation and will ultimately limit their performance. Without fundamental change in the design of supercomputing systems, the performance advances common over the past two decades won’t continue.
As the methodology is still new, and requires some apples-to-oranges comparisons, it’s not surprising that the listings are dominated by one vendor’s architecture. IBM’s Blue Gene takes the top 26 spots in the table, with energy consumption of 204 to 357 megaFLOPS per watt. Slot #500 comes in 2 orders of magnitude lower, at 3.65 megaFLOPS per watt.
J Luc Pitard hops in the backseat of one of GM’s hydrogen fuel cell demonstrator vehicles. Robert Seigel takes the wheel of the specially-fitted Chevy Equinox.
Phil Patton previews new designs for hybrid and electric cars. Toyota is showing a spiffy 2-door concept car called the X that features a lot of glass.