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Turning Off the Air Conditioning Helps Save Fuel, Swiss Study Finds

2010-07-05T09:28:00.000-07:00

ScienceDaily (June 28, 2010) — Automobile air conditioning systems do not run "free of charge." In fact in the hot parts of the world they can account for up to thirty per cent of fuel consumption. Even in Switzerland, with its temperate climate, the use of air conditioning systems is responsible for about five per cent of total fuel usage, rising to around ten per cent in urban traffic, as shown by a new study undertaken by Empa on behalf of the Swiss Federal Office for the Environment (FOEN). Furthermore, two thirds of the additional fuel usage could be saved if air conditioning systems were simply turned off when the air temperature falls below 18 degrees Celsius.

Car air conditioning systems require energy to compress the cooling agent, and the greater the degree of cooling required the more energy (i.e. fuel) they use. Little known, however, is the fact that these systems also used fuel when the outside air temperature is cooler than in the vehicle. For this reason the Federal Office for the Environment (FOEN) gave Empa the task of investigating in detail the fuel consumption of six modern cars -- both diesel and petrol models -- with their air conditioning systems switched on and off under varying ambient temperatures and humidities.

The study, the results of which have just been published in the scientific journal "Environmental Science and Technology," shows that the fuel consumption of the test vehicles with air conditioning systems in operation increases with rising ambient air temperature and humidity, reaching a value of some 18 per cent on a typical Swiss summer day with an air temperature of 27 degrees and relative humidity of 60 per cent. In addition, the researchers noted that the air conditioning systems in cars with automatic transmissions (which today are the most widely sold models) only turn themselves off when the external temperature drops below 5 degrees, when the cooling system could ice-up. This occurs because air conditioning systems not only cool the air before blowing it into the vehicle interior but also dry it, so as to avoid causing condensation on the front windscreen when it rains, among other reasons. This is of course perfectly sensible and important for safe driving, but only when the air humidity is high, and not all the time -- as is currently the case.

Using the standard climate model defined by the Swiss Society of Engineers and Architects (SIA, Bern^*) and allowing for the measured increase in consumption (plus the use of the vehicle during the day), the average annual extra consumption of a petrol-engined car works out to 5.4 per cent. Differentiating between urban, suburban and motorway driving gives additional fuel usage values of 10, 2.8 and 1.3 per cent respectively.

It is known from physiological studies that the average driver feels comfortably warm when the air temperature around the head is 23 degrees. This means that if the outside temperature is below 18°C the car's air conditioning system could be turned off without any loss of comfort. For the petrol-engined vehicles investigated this would represent a saving of some two-thirds of the additional fuel usage, which is after all 3.6 per cent of the total consumption. When the outside temperature is higher, it is advisable to keep the air conditioning switched on since otherwise the heat may affect the driver's concentration and reduce safety.

With the diesel fuelled vehicles tested, the additional consumption due to the use of air conditioning, particularly for urban driving, is somewhat lower (2.7 per cent in total). The individual values for urban, suburban and motorway driving in this case are 4.5, 2.3 and 1.2 per cent respectively. The potential saving possible through switching off the air conditioning unit when the outside temperature falls below 18 degrees remains, however, two thirds of the additional consumption for the diesel vehicles tested.

If the entire Swiss automobile fleet is evaluated -- that is, including vehicles without air conditioning systems as well as older models with inefficient compressor units -- then a figure of 3.1 per cent of additional consumption is arrived at, assuming all air conditioning units are in use over the whole year. This drops to 1 per cent if air conditioning units are switched off when the ambient air temperature falls below 18 degrees. This simple measure could therefore result in a reduction in total fuel consumption of some two per cent across the whole country.

^*The SIA standard climate model contains hourly weather data such as temperature and relative humidity over a compete year and is used by architects to calculate insulation and heating requirements for buildings.

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Using Carbon Nanotubes in Lithium Batteries Can Dramatically Improve Energy Capacity

2010-07-05T09:15:00.000-07:00

ScienceDaily (June 21, 2010) — Batteries might gain a boost in power capacity as a result of a new finding from researchers at MIT. They found that using carbon nanotubes for one of the battery's electrodes produced a significant increase -- up to tenfold -- in the amount of power it could deliver from a given weight of material, compared to a conventional lithium-ion battery. Such electrodes might find applications in small portable devices, and with further research might also lead to improved batteries for larger, more power-hungry applications.

To produce the powerful new electrode material, the team used a layer-by-layer fabrication method, in which a base material is alternately dipped in solutions containing carbon nanotubes that have been treated with simple organic compounds that give them either a positive or negative net charge. When these layers are alternated on a surface, they bond tightly together because of the complementary charges, making a stable and durable film.

The findings, by a team led by Associate Professor of Mechanical Engineering and Materials Science and Engineering Yang Shao-Horn, in collaboration with Bayer Chair Professor of Chemical Engineering Paula Hammond, are reported in a paper published June 20 in the journal Nature Nanotechnology. The lead authors are chemical engineering student Seung Woo Lee PhD '10 and postdoctoral researcher Naoaki Yabuuchi.

Batteries, such as the lithium-ion batteries widely used in portable electronics, are made up of three basic components: two electrodes (called the anode, or negative electrode, and the cathode, or positive electrode) separated by an electrolyte, an electrically conductive material through which charged particles, or ions, can move easily. When these batteries are in use, positively charged lithium ions travel across the electrolyte to the cathode, producing an electric current; when they are recharged, an external current causes these ions to move the opposite way, so they become embedded in the spaces in the porous material of the anode.

In the new battery electrode, carbon nanotubes -- a form of pure carbon in which sheets of carbon atoms are rolled up into tiny tubes -- "self-assemble" into a tightly bound structure that is porous at the nanometer scale (billionths of a meter). In addition, the carbon nanotubes have many oxygen groups on their surfaces, which can store a large number of lithium ions; this enables carbon nanotubes for the first time to serve as the positive electrode in lithium batteries, instead of just the negative electrode.

This "electrostatic self-assembly" process is important, Hammond explains, because ordinarily carbon nanotubes on a surface tend to clump together in bundles, leaving fewer exposed surfaces to undergo reactions. By incorporating organic molecules on the nanotubes, they assemble in a way that "has a high degree of porosity while having a great number of nanotubes present," she says.

Lithium batteries with the new material demonstrate some of the advantages of both capacitors, which can produce very high power outputs in short bursts, and lithium batteries, which can provide lower power steadily for long periods, Lee says. The energy output for a given weight of this new electrode material was shown to be five times greater than for conventional capacitors, and the total power delivery rate was 10 times that of lithium-ion batteries, the team says. This performance can be attributed to good conduction of ions and electrons in the electrode, and efficient lithium storage on the surface of the nanotubes.

In addition to their high power output, the carbon nanotube electrodes showed very good stability over time. After 1,000 cycles of charging and discharging a test battery, there was no detectable change in the material's performance.

The electrodes the team produced had thicknesses up to a few microns, and the improvements in energy delivery only were seen at high-power output levels. In future work, the team aims to produce thicker electrodes and extend the improved performance to low-power outputs as well, they say. In its present form, the material might have applications for small, portable electronic devices, says Shao-Horn, but if the reported high power capability were demonstrated in a much thicker form -- with thicknesses of hundreds of microns rather than just a few -- it might eventually be suitable for other applications such as hybrid cars.

While the electrode material was produced by alternately dipping a substrate into two different solutions -- a relatively time-consuming process -- Hammond suggests that the process could be modified by instead spraying the alternate layers onto a moving ribbon of material, a technique now being developed in her lab. This could eventually open the possibility of a continuous manufacturing process that could be scaled up to high volumes for commercial production, and could also be used to produce thicker electrodes with a greater power capacity. "There isn't a real limit" on the potential thickness, Hammond says. "The only limit is the time it takes to make the layers," and the spraying technique can be up to 100 times faster than dipping, she says.

Lee says that while carbon nanotubes have been produced in limited quantities so far, a number of companies are currently gearing up for mass production of the material, which could help to make it a viable material for large-scale battery manufacturing.

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The Future of the "Gods" of Energy

2010-07-05T06:42:00.000-07:00

"...Prometheus was sorry for mankind and he went to Zeus and asked him if he might have some sacred fire for his poor creatures.

But Zeus said no, fire belonged to the gods alone.

Prometheus could not bear to see his people suffer and he decided to steal fire, though he knew that Zeus would punish him severely. No longer did men shiver in the cold of the night, and the beasts feared the light of fire and did not dare attack them...."

Every time I remember this myth of ancient antiquity I can't help but think that as mankind developed and society evolved we have been duped into giving away fire to the "gods". We renounced that which was rightfully ours, everyone's, and we placed it in the hands of "divine" few. Now, the superstitions of old have long ago lost existential significance and bear little more than a multitude of metaphors and morals, however, it is these insights which hold true even to this day.

Long ago Prometheus stole fire from the gods because he could not bare seeing the suffering of humanity. Our ancestors used fire to achieve incredible things and to lead the world into a better tomorrow. This is not a historical discussion, all I am saying is that in the millennia before us mankind survived and grew. We created the world of science fiction in which we live today, however instead of finding salvation in the technology which we developed, we only find restraint. Special interests and profit seeking enterprises, as amazing as they were in bringing society this far, are being revealed as an obstacle of exploitation and scarcity.

There will never be a world without hunger and disease, a world with abundant clean and free energy for all, a sustainable society worthy of our dreams of the 21st century until we take out the principle of scarcity from the developmental equation.

The fire of the gods is now converted to electricity which is priced for profits, not for availability. Humanity possesses the know-how to change this, but the "gods" of today will not allow a modern Prometheus to rise to the occasion and deliver us from the hopeless desperation which is imposed over us.

If you gave this post the benefit of a doubt and you've reached this far along, it is clear to you by now that this "us" which I am constantly using comes naturally to me. The nation states of the past century are slowly dying and those in power are willing to stake the survival of humanity in order to preserve these derelict ideas of division. We are one world, one spirit, not only in the nonsensical new age hippy phrases we see in rallies and concerts but in the substantial simplicity of our hope for a better future for us and those we love. No-one can convince me that there is a group of people somewhere in the word which do not want too see their children grow up and work for a better tomorrow. No matter how fanatical or crazy misguided individuals might seem the truth remains that they became like that from our collective failure to take matters into our own hands and share the knowledge which gives us the lives we live.

And that is the main point of this blog, sharing the knowledge. We do not need philosophical ramblings like the one in the paragraph above about ideological adequacy or conservative values, but rather practical solutions to practical problems shared between individuals of all areas of science, engineering you name it.

Going back to Prometheus I would like to make a final point, it took a son of a god to give humanity fire the first time around and he paid a terrible price for his benevolence. Be this a mere myth it is clear to me that one person can not make a difference in the world of today if she/he is acting alone. This is why I will make an attempt to share everything I find that can help a family or a community, an individual or a city, to establish their independence from the grid, to seek development without profit, to live of the land which is home. to help unite the world by dividing the power and also the responsibility. Let us become our own Gods.