Charging Up Electric Car Batteries in Environmentally-Friendly Way

ScienceDaily — Electromobility makes sense only if car batteries are charged using electricity from renewable energy sources. But the supply of green electricity is not always adequate. An intelligent charging station can help, by adapting the recharging times to suit energy supply and network capacity.

Germany aims to have one million electric vehicles -- powered by energy from renewable sources -on the road by 2020. And, within ten years, the German environment ministry expects "green electricity" to make up 30 percent of all power consumed. Arithmetically speaking, it would be possible to achieve CO2-neutral electromobility. But, in reality, it is a difficult goal to attain. As more and more solar and wind energy is incorporated in the power grid, the proportion of electricity that cannot be controlled by simply pressing a button is on the increase. In addition, there is a growing risk that the rising number of electric vehicles will trigger extreme surges in demand during rush hour.

"What we need is a smart grid that carries information in addition to power," says Dominik Noeren of the Fraunhofer Institute for Solar Energy Systems ISE. The structure of the grid has to change from a push system based on energy demand to a pull system based on production output. In Noeren's opinion, "electric cars are best equipped to meet this challenge." Introduced in large numbers, they have the capacity to store a lot of energy. On average, a car is parked for at least 20 hours out of 24. That is more than enough time to recharge them when the wind picks up or the demand for electricity is low.

Developed by Fraunhofer researchers, the "smart" charging station is a device that enables electric vehicles to recharge when the system load is low and the share of energy from renewable resources is high. In this way, load peaks can be avoided and the contribution of solar and wind power fully exploited. "For us, it is important that end consumers are completely free to decide when they want to recharge. We do not want them to suffer any disadvantages from the controlled recharging of their vehicles' batteries," Noeren emphasizes. That's why he favors electricity rates that adapt to the prevailing situation in the power grid -- ones that are more expensive in periods of peak demand and particularly cheap when there is a surfeit of renewable energy.

The person using the "smart" charging station could then choose between recharging immediately or opting for a cheaper, possibly longer, recharging time. If they go for the second option, all they need to do is enter the time when their vehicle has to be ready to drive again. The charging station takes care of everything else, calculating the costs and controlling the recharging process. Via the display the user can track the progress of recharging and also see the costs incurred and the amount of energy used.

The experts will be presenting their charging device at the Hannover Messe from April 19 through 23.

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Source:http://www.sciencedaily.com/releases/2010/04/100421111353.htm

 

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

ScienceDaily — 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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Source:http://www.sciencedaily.com/releases/2010/06/100622081359.htm