Posted by Max Dunn Tue, 22 Jan 2008 22:57:16 GMT | 1 comment
Nowadays, if you are looking to install a hot tub, your only option is likely to be a hot tub that heats with electricity. The salesman will tell you that they are very well insulated (which they are) and that it will only cost about $30 per month of electricity to heat it (which is possible but optimistic.) Let’s look at the math and physics behind this.
Posted by Max Dunn Wed, 09 Jan 2008 19:43:05 GMT | no comments
It turns out that lithium is not very abundant or easy to mine, and that the price is going up. In this paper, the author even argues that there is not enough lithium available in the world to convert all cars over to plug-in hybrid (PHEV) if we expect to use lithium batteries in them:
The Trouble with Lithium – Implications of Future PHEV Production for Lithium Demand
Posted by Max Dunn Wed, 09 Jan 2008 18:39:28 GMT | no comments
An revolutionary new technology is being developed by Stanford researcher Yi Cui that could could generate 10 times more energy from lithium-ion batteries. The trick is that instead of using carbon anodes, they use silicon nanowires because silicon can hold large amounts of lithium atoms. The nanowire technology allows these small wires to swell to four times their normal size without breaking. [1]
When Cui’s paper was originally submitted six months ago, they had only achieved 30 charge-discharge cycles. Since that time however, Cui’s team has pushed the battery through 1000 cycles. [2]
Ultimately, these batteries should be cheap to build. However, they are probably 5 years away from being commercialized. [3]
In reality though, the “10 times more energy” figure is just the theoretical charge capacity increase in the silicon anode, so a real production battery won’t see that much improvement. But even if it improves the overall energy density of a lithium ion battery by 2 or 3 times, that would still be very significant.
[1] Nanowire battery can hold 10 times the charge of existing lithium-ion battery
[2] New Nanowire Battery Life Reaches From iPods to Electric Cars
[3] GM-Volt.com: Interview with Dr. Cui, Inventor of Silicon Nanowire Lithium-ion Battery Breakthrough
Posted by Max Dunn Wed, 09 Jan 2008 04:10:37 GMT | no comments
In my son’s 7th grade social studies class today, he was given an article that discussed how the warming of the Antarctic was melting ice sheets and reducing the population of some penguin colonies. However, while the breakup of the Larsen B ice shelf was unexpectedly rapid, the Antarctic as a whole has actually had stable or decreasing temperatures and the overall ice pack has probably been growing. Even the IPCC recognizes this by stating:
“Antarctic sea ice extent continues to show interannual variability and localised changes but no statistically significant average trends, consistent with the lack of warming refl ected in atmospheric temperatures averaged across the region.” [1]
Another source confirms that:
“it is also clear from satellite data that surface temperatures decreased during the years 1982 through 2002” and “the Antarctic ice sheet had gained enough mass between 1992 and 2003 to slow sea level rise at a rate of about 1 cm/century” [2]
And one source states:
“over the past four decades, and during the time of the greatest build-up of greenhouse gases, Antarctica has been cooling!” [3]
These observations in no way disprove global warming in general. However, they do clearly show is that climate change is very complex science and that you can’t draw simple or universal conclusions based on it.
[1] IPCC AR4 Summary for Policymakers (Page 9)
Posted by Max Dunn Tue, 08 Jan 2008 15:07:29 GMT | no comments
Here is a very long and detailed analysis of food-based biofuel production and how it could cause problems with the food supply:
The scary point about this article is that it illustrates how profitable it is to make biofuel when oil prices are high and how this could lead to devastating consequences if we have a bidding war between the gas tanks of the roughly one billion middle class people on the planet, and the dinner tables of the poor.
Posted by Max Dunn Thu, 03 Jan 2008 17:26:38 GMT | 1 comment
Nanosolar announced that is is starting to ship its thin-film solar panels that cost less than $1 per watt! Could these panels save the world?
Maybe, but Nanosolar is being very tight about information, citing patent concerns:
“Technical Data Sheet? We presently share product data sheets only under Non-Disclosure Agreement with qualified volume customers. This is so we can extend the period of protection for certain proprietary features we have developed.”
Their first 12 months of production is already sold out and is going to commercial installations, so maybe it isn’t efficient enough to put on a house. But there was one tidbit where Nanosolar’s CEO said they could produce about as much energy as the a silicon wafer.
It also received Popular Science’s Green Tech product of the Year award
Posted by Max Dunn Wed, 02 Jan 2008 00:11:07 GMT | 4 comments
A new solar power plant just opened up at Nellis Air Force Base in southern Nevada [1]. Currently it is the largest solar photovoltaic system in North America with a capability of 14 megawatts (mW) of peak power, and producing about 25 million kilowatt-hours (kWh) of electricity per year [2].
However, it cost $100 million to build, which is about $7,000 per kilowatt (kW). This is a lot more than a coal-powered plants which costs about $3,000 per kW to build [3]. But since the sun is free and coal-powered plants have to pay for the coal, shouldn’t this make up for the additional cost of solar systems?
It turns out, that it doesn’t. To see why, let’s look at the numbers.
Posted by Max Dunn Sun, 30 Dec 2007 17:43:32 GMT | no comments
When I talk about how clean electric vehicles are, people sometimes ask if they really do reduce greenhouse gases since burning coal to produce electricity creates a lot of CO2. My standard answer to this question is that even in the worst case, electric cars are twice as clean as gas powered cars. However, while reading an article in Forbes about vehicle-to-grid (V2G) systems. I realized that in general, electric cars are much cleaner than even this.
This article had an interesting chart that said electric cars produce about 1.1 tons of greenhouse gases a year while gas powered cars produce 6.3 tons – over 6 times more! Let’s see if we can verify these numbers.
The average car is driven 15,000 miles per year and electric vehicles normally get 4 miles per kWh, so it takes about 3,750 kWh of electricity a year to power an electric car. In California, the mix of electricity production produces about 0.6 lbs of greenhouse gases per kWh so this would produce 2,250 pounds, or 1.1 tons of greenhouse gases – right on the money with the Forbes chart.
A gas car, on the other hand, produces about 1 lb of CO2 for every mile driven (based on producing 20 lbs per gallon and getting 20 mpg). So 15,000 miles would produce 15,000 lbs of greenhouse gases, or about 7.5 tons – which is more than the Forbes estimate of 6.3 tons (maybe they are using a higher mpg).
So electric cars are even cleaner than I had thought, producing about one sixth as much greenhouse gases as a gas car.
Posted by Max Dunn Fri, 21 Dec 2007 19:07:56 GMT | no comments
When trying to discredit a scientist’s work, critics sometimes simply note: “They received funding from XYZZY corporation.” It is interesting that often nothing more is said, as if it is apparent that taking any money from a party with a vested interest will inevitably skew the results. This seems like a pretty harsh position, but there is some basis to this claim.
For instance, new research looked at drug studies and found that while the results of the study were not likely to be biased, the conclusion from those results were. In particular, they found that studies funded by a single drug company have a 55% rate of favorable results that is transformed into a 92% rate for favorable conclusions, representing a 37% gap. The gap shrinks to 21% (57% to 79%) when two or more drug companies provide support. Yet the gap vanishes entirely for studies done by non-profit institutions alone or even in conjunction with drug companies. These findings suggest a disconnect between the data that underlie the results and the interpretation or “spin” of these data that constitutes the conclusions.[1]
So it is apparent that receiving funding from a particular source that has a vested interest in the outcome will likely affect the conclusion of a study.
But are there other biases besides funding sources that can affect the results or conclusions of scientific work? What if a researcher isn’t taking any outside funding but has a passionate belief about what they are researching – will this affect their work as well?
Posted by Max Dunn Sat, 08 Dec 2007 17:52:03 GMT | no comments
The global temperature graph that appears in An Inconvenient Truth and also the one that the IPCC uses is usually referred to as the Mann or MBH98 graph.
However, this temperature reconstruction is controversial. One of its problems is that it doesn’t show the Medieval Warming Period or the Little Ice Age (LIA).
More recently, Loehle put together another temperature reconstruction that doesn’t use tree rings and this reconstruction does show the MWP and LIA.