Well-to-wheel

from Wikipedia, the free encyclopedia

Well-to-Wheel (also: Well to Wheel , Well2Wheel or WTW , literally: "from the borehole to the wheel") is an observation or analysis method in the field of motor vehicles . The entire chain of effects for locomotion is examined, from the generation and provision of drive energy to conversion into kinetic energy .

General

Different fuel paths require different amounts of energy to travel 100 km. From left to right: coal to electricity to electric car. Renewable energy (e.g. wind or photovoltaics) to battery-powered electric cars. Renewable energy to hydrogen to hydrogen car. Crude oil to diesel to cars with classic combustion engines.

In the well-to-wheel analysis, the sub-areas well-to-tank (energy supply) and tank-to-wheel (vehicle efficiency) are combined. Vehicle manufacturers can only ever constructively influence the tank-to-wheel sub-area . Only this is therefore included in the manufacturer's information on the vehicle (fuel / energy consumption or exhaust gas information or CO 2 emissions). With simulation programs, relationships can be illustrated and optimization options shown.

Well-to-wheel examinations can be carried out from different perspectives:

The well-to-wheel consideration also plays a major role in the ecological assessment . However, Well-to-Wheel only records the actual operation of the vehicle, neither maintenance nor upkeep, nor the manufacturing and disposal costs. In contrast, studies of the life cycle assessment analyze the entire life cycle including production and recycling.

Well-to-wheel in vehicles with internal combustion engines

In vehicles with internal combustion engines , the greatest losses occur in the vehicle itself; the fuel is generated and supplied mainly from fossil primary energies and with a high degree of efficiency. Therefore, the differences between the manufacturer's information tank-to-wheel and well-to-wheel are relatively small. However, the well-to-tank efficiency of approx. 90% for diesel fuel, approx. 82% for gasoline and approx. 86% for natural gas is not negligible when compared with alternative drive technologies.

The BMW Hydrogen 7 , whose modified combustion engine runs on hydrogen , can be considered a special case . In addition to being almost completely free of local emissions (tank-to-wheel only produces water vapor and small amounts of nitrogen oxides), the well-to-wheel approach, similar to the fuel cell vehicle, also includes the effort involved in hydrogen generation and provision. The hydrogen production currently uses (2015) almost exclusively fossil primary energy sources. Their processing and the necessary liquefaction lead to a low well-to-wheel efficiency or high consumption of fossil primary energies with correspondingly high CO 2 emissions.

Well-to-wheel for vehicles with electric drive

The electric car has a very high tank-to-wheel efficiency and no local CO 2 emissions. This is expressed in the very low manufacturer information on tank-to-wheel consumption (15–20 kWh / 100 km) and the information on CO 2 emissions (0 g CO 2 / km). The losses arise mainly during the generation and supply of electricity, i.e. well-to-tank . For this reason, the well-to-tank chain is often included and, in contrast to conventional vehicles with a combustion engine (manufacturer information only includes tank-to-wheel), the data on the electric car are well-to-wheel . For objective comparisons, the same chain of effects of the different motor vehicles should therefore always be considered. In 2014, an electric car charged with the German electricity mix (29% renewable energies ) drove around 20 percent less CO 2 emissions than vehicles with fossil fuels. In 2019 (45% share of renewable energies) this share will decrease further. If an electric car is powered entirely by renewable energies , the well-to-wheel CO 2 emissions drop to almost zero.

Well-to-wheel for vehicles with hybrid drive

When hybrid drive , there is a combination of different types of drives . This makes it difficult to make a generally valid statement, since the proportions of the drive types vary depending on the concept and, above all, the individual driving profile and thus the efficiency and the well-to-wheel pollutant emissions can fluctuate greatly. The information on the standard consumption provides a clue, however, which relates to a driving profile that can vary greatly in practice.

The current consumption figures for electric hybrid vehicles - ECE standard R 101 are openly criticized because they neither take into account the required (previously charged) amount of electrical energy, nor show the electric range of the vehicles. Greenwashing is carried out in favor of the automotive industry and the customer is deliberately deceived about the real energy consumption / fuel costs. This has not changed until 2019, in practice hybrid cars consume four times as much fuel as determined in the test cycles and more - and thus emit up to four times as much CO 2 and other substances as specified.

Fuel cell vehicles

A fuel cell vehicle like the Honda FCX is a vehicle with an electric drive , in which a fuel cell is installed as a range extender to increase the range . Although the vehicles are locally emission-free (tank-to-wheel) and have a high degree of efficiency, large amounts of energy are required to generate and supply hydrogen ( well-to-tank ) (liquefaction for transport and storage, compression of up to 700 bar in the Pressure tank) and fossil primary energies are used. Therefore, the fuel cell vehicle is currently (2015) when considering the well-to-wheel chain, just like the electric car (unless it is charged with renewable energies ), and has a significantly poorer energy efficiency compared to this.

For the process chain regenerative electricity electrolysis - low-pressure hydrogen storage (200 bar) - (central) reconversion with fuel cells, an efficiency of 30% is assumed without the use of thermal energy. This chain of effects is currently (2012) not yet profitable. In addition, the losses for liquefaction and storage (outgassing) at the filling station (if not supplied by pipeline ) as well as the expenditure for maximum compression (700 bar) for mobile use in pressure tanks and the intermediate storage of electrical energy in traction batteries are not taken into account.

So while the manufacturers praise their vehicles ( tank-to-wheel ) as “by far the most environmentally friendly car in the world”, a well-to-wheel view has already described it as “one of the most climate-hostile cars of all”. Due to the nature of the system, their well-to-wheel efficiency is always lower than that of pure electric cars .

Hybrid with internal combustion engine

An attempt is made here to use the high efficiency of the electric drive, but to compensate for the disadvantages of the limited range by combining it with a combustion engine. Various concepts are currently being developed in parallel:

  • Serial hybrid : One or more electric motor (s) drive the vehicle, no mechanical connection between the combustion engine and the vehicle drive, this recharges the accumulator via a generator
  • Power-split hybrid : Above concept, possibility of direct coupling of the drive power of the combustion engine, mostly in its most favorable working range ( e.g. Chevrolet Volt , Toyota Prius )
  • Parallel hybrid : both drive systems can move the vehicle, or in a weaker version without exclusively electric driving operation as:
  • Mild hybrid : The combustion engine drives the vehicle, the electric motor only has a supporting effect and often also implements a recuperation brake or starting aid to increase efficiency.

See also

Web links

Individual evidence

  1. ↑ European Commission, May 2006, March 2007: Well-to-Wheels Analyzes of future automotive fuels and powertrains in the european context ( Memento of March 4, 2011 in the Internet Archive ) (PDF file; 1.0 MB), inserted on January 26, 2012.
  2. ↑ European Commission, July 2011: Well-to-Wheels Analyzes of future automotive fuels and powertrains in the european context. (PDF file; 728 kB), inserted on April 18, 2012.
  3. ↑ Zeit online, July 2010: No electric car is completely clean. Inserted on January 26, 2012.
  4. ↑ AM Foley, B. Smyth, B. Gallachoir, 2011: A Well-to-Wheel Analysis of electric Vehicles and greenhouse Gas savings. (PDF file; 73 kB), inserted on April 18, 2012.
  5. ↑ Hydrogen Center Austria, October 2009: Efficiency and CO 2 emissions of various energy chains. (PDF file; 173 kB), inserted on January 26, 2012.
  6. ↑ Software tool for well-to-wheel comparisons: Optiresource. Information and online simulation program added on January 26, 2012.
  7. ^ Paul Scherer Institute PSI, April 7, 2010: Life cycle assessment of electromobility. (PDF file; 353 kB), inserted on February 27, 2012.
  8. ↑ a b AMS, January 2009: Energiebrisanz.  ( Page no longer available , search in web archives ) PDF file, inserted on January 26, 2012.@1@ 2Template: Dead Link / www.etha-plus.ch
  9. ↑ JRC, UBA, September 2013: Green gas emissions from various fuels and types of drive. Accessed September 22, 2014.
  10. ^ Zeit online, November 4th 2010: Consumption values ​​of hybrid cars are misleading. Accessed May 6, 2013.
  11. ↑ WDR, November 7th, 2019: Hybrid cars, the great climate lie. Accessed December 3rd, 2019.
  12. ↑ H2-Works: hydrogen storage. Accessed August 14, 2012.
  13. ^ Zeit online, May 17, 1996: The tamed oxyhydrogen. Accessed June 25, 2013.
  14. ↑ heise.de, July 7, 2014: One of the most climate-hostile cars ever. Accessed September 29, 2014.
  15. ^ Federal Environment Agency Austria, Vienna 2014: Life cycle assessment of alternative drives. PDF, accessed September 29, 2014.