Well-to-tank

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Well-to-Tank (also Well2Tank or WTT, analogously: "from the borehole to the tank", or Well-to-Station: "from the borehole to the fuel pump") is a view of the effort involved in providing the drive energy for vehicles from primary energy generation until it is ready for the vehicle. The transfer point for economic and energetic considerations is generally the last (mostly calibrated) measuring device in front of the vehicle.

General

Well-to-Tank describes the functional chain that arises up to the provision of energy on the vehicle and does not affect the vehicle's efficiency . Objectively transferred, WTT considers the energy path "from primary energy to final energy at the fuel pump / charging station / socket" without including the motor vehicle. The influences to be taken into account are not absolute, as they not only depend on the type of drive energy and the manufacturing process, but also on the selected consideration, the availability of raw materials, the price development and other factors. This results in differences in the supply chains depending on the global location and also on the type and time of consideration. The following approaches are common:

  • Efficiency
  • Cost per unit of energy
  • Pollutant emissions per unit of energy

The well-to-tank chain of effects cannot be influenced by the vehicle manufacturer and is therefore not included in the manufacturers' consumption or pollutant information. The sum of well-to-tank and tank-to-wheel results in the overall functional chain of the vehicle in well-to-wheel operation . A simulation with computer programs, e.g. B. Optiresource, can represent the relationships and show optimization possibilities.

The consideration of the entire life cycle of a product is even more comprehensive. For motor vehicles, this includes not only the well-to-wheel vehicle operation, but also maintenance, upkeep as well as manufacture and disposal. Such considerations are made as a comprehensive cost analysis or as a life cycle assessment .

Well-to-tank for fossil fuels

In motor vehicles with internal combustion engines , fossil fuels based on fossil energies , mainly from crude oil and natural gas, are currently (2014) standard. Well-to-Tank summarizes the production costs that arise for the primary energy supply, the transport of the primary energy carriers, the refining, processing and, for example, compression of drive gases, as well as the transport of the fuels to the filling stations. Since it is a pure consideration of expenditure, energetic losses and ecological effects, which arise, for example, from the flaring of associated gases in crude oil production, are largely neglected in WTT as well as in the harvest factor . In addition to the subsidy expenditure, only the expenditure for the construction and operation of the flaring systems is accounted for.

In Germany, the well-to-tank efficiency is usually assumed for gasoline with approx. 82%, diesel with approx. 90% and natural gas with approx. 86%. A 2008 study from Switzerland on behalf of the city of Zurich gave 1.29 for gasoline , 1.22 for diesel and 1.17 for natural gas as primary energy factors , i.e. for gasoline 77.5%, diesel 82%, natural gas 85% Manufacturing. In 2011, the German Energy Agency put the energy share of the refineries in the well-to-wheel consumption of motor vehicles (p. 33) at 8.7% - excluding subsidies, distribution and transport. The underlying database dates from before 2008.

However, these values ​​are not absolute, since, for example, the effort and costs of extraction increase with increasing scarcity (development of more inefficient, more complicated deposits) and thus the efficiency deteriorates or the primary energy requirement for the provision of fuels continues to rise. The production volume of the various fuels in the refineries has also been optimized in terms of efficiency. In Germany in 2010 there were around 30 million tons of diesel and 21 million tons of gasoline. A doubling of the diesel share compared to the gasoline share would lead to an approximately 6% higher energy requirement in the refineries.

The increasing extraction of heavy oil from oil sands is associated with three to four times higher energy consumption / greenhouse gas emissions than with conventionally extracted oil. Since the conveying techniques and manufacturing processes for fossil fuels have been optimized over many years, significant efficiency improvements in the manufacturing process can no longer be expected. The production costs, which are increasingly dominated by energy consumption, are today around 4 to 6 times as much for unconventional oil production as compared to conventional oil production. “The high energy consumption is already driving up the costs of production: estimates by the management consultancy Cambridge Energy Research Associates have shown that the costs of extracting oil sands are already around 85 dollars per barrel . To extract a barrel of oil in Saudi Arabia costs around 20 dollars. ”The efficiency of the supply of fossil fuels will continue to deteriorate in the future.

The energy consumption for fuel production in the refineries will also increase further (up to 50% of the costs), since ever higher demands are made on the fuels for environmental reasons (e.g. low sulfur content).

Well-to-tank for biofuels

For the production of biofuels , which are usually intended to partially or completely replace fossil fuels for vehicles with internal combustion engines, the expenditure for cultivation, harvesting, processing and distribution must be considered. While decentrally generated and consumed biofuels such as vegetable oil and bioethanol have short active chains, the active chain with hydrogenated vegetable oil , biodiesel or BtL fuel is longer, the effort is greater and therefore the WTT efficiency is sometimes significantly lower.

Well-to-tank in power generation for electric propulsion

In the case of electric cars , Well-to-Tank denotes the manufacturing effort involved in generating and providing electrical energy until it is transferred to the motor vehicle at the charging station / socket . The analysis therefore includes the losses from electricity generation from fossil sources ( coal , natural gas and oil) and from renewable sources (hydropower, wind energy, solar energy, biomass, geothermal energy) as well as the losses from electricity transformation and transport ( electricity grid losses ).

The generation of electricity from nuclear energy is difficult to consider from the perspective of efficiency, since the efficiency was arbitrarily set at 33%. The efficiency of the generation and provision of electrical energy has so far steadily improved thanks to improved technologies, the use of renewable energies and decentralized power generation such as, for example, systems with combined heat and power .

The CED value, which holistically describes the primary energy expenditure of an economic good, is “101.4” for a diesel car, “121” for an electric vehicle (2007 electricity mix) and 100% renewable energy for an electric vehicle Stream "83".

Efficiency of the provision of electrical energy and primary energy factors

The efficiency of electricity transformation and transport to the end user (transmission and distribution networks) is around 94% in Germany. The 6% transmission losses are billed additionally for each type of electricity generation. Lower losses result from increasing decentralized energy generation , since multiple transformations and long transmission paths are no longer necessary. Low-loss high - voltage direct current transmission was developed for long-distance transmission of electrical energy . In a 2006 US study by the University of Berkeley on electrical mobility, it says on page 8: "6.6% electricity transmission loss (national average)" for the Chinese power grid. Germany has shorter lines and a modern infrastructure.

New, efficient lignite power plants work with 43%, hard coal power plants with up to 47%. In Germany, the overall efficiency of all coal-fired power plants is assumed to be 38%. The total efficiency for pure coal electricity with transport losses would be 35.7%, the primary energy factor for the electricity supply is then 2.8.

Efficient working gas and steam cycle power plants with an electric efficiency of more than 60%. On average, 55% are assumed, including the distribution would then result in 51.7%, primary energy factor 1.93.

Since no primary energy has to be used when using wind, water and sun, the result would be efficiencies of up to 94%. When generating electricity from renewable energies, such as water power, wind or photovoltaics, only the electrical energy generated flows into the primary energy consumption and the efficiency analysis. When generating electricity from biomass, the cost of generating and providing electricity should be included. An efficiency of around 90% (primary energy factor 1.18) is therefore assumed. When considering the costs of Well2Tank, the necessary systems / generation costs for all types of electricity generation must always be included.

Electricity generation in nuclear power plants must be given special attention. Their arbitrarily set efficiency of 33% should include the expenditure for raw material extraction, processing, power generation and disposal of radioactive waste. At the socket, the transmission losses would result in an efficiency of 31% and a (fictitious) primary energy factor of 3.22. Depending on the point of view, however, the chain of effects of nuclear power is highly controversial.

Practical approach in the real electricity mix

In practice (with the exception of self-generated electricity), electricity consists of a changing electricity mix from different producers. The efficiency of the entire power generation is improved by increasing the efficiency of the existing power plants , increased use of renewable energy , more efficient power plant technology such as combined cycle power plants , combined heat and power plants , improved power plant management or even more efficient transmission technologies such as high-voltage direct current transmission . It worsens, for example, if the share of less efficient electricity producers in the total amount of electricity increases. The efficiency of total electricity generation also fluctuates seasonally: In Germany it is higher in summer than in winter: The share of fossil power plants (in the lower summer electricity demand) is significantly lower in summer (shutdowns, partial load operation, maintenance shutdowns) because the total electricity demand is lower. At the same time, water and photovoltaics generate larger amounts of electricity in summer than in winter.

A study from Switzerland published in December 2008 shows a national primary energy factor, which includes the losses for distribution, of 2.97 and for the entire UCTE of 3.53.

In 2009, the primary energy factor for electricity generation in Germany was 2.6.

Based on the data for the 2010 electricity mix, the following approach can be chosen for total electricity generation:

  • Coal: 43% total with 38% efficiency
  • Nuclear energy: 22% share with 33% efficiency
  • Natural gas: 14% share with 55% efficiency
  • Water, wind and sun: 11.4% share with 100% efficiency
  • Biomass and other (waste incineration, mine gases, etc.): 10.6% with 90% efficiency

The efficiency of all power generators in the mix can therefore be set at 52.57%. Taking into account the 6% transport losses, this would result in an efficiency of 49.4% at the socket for the general electricity mix in Germany in 2010. This means that for one kWh of usable electrical energy at the consumer, slightly more than double the amount of energy (primary energy factor: 2.02) has to be used at the start of electricity generation in Germany. A value of 494gCO 2 / kWh was determined for the considerations on fossil primary energy consumption .

Remarks:

  1. ↑ a b The efficiency of nuclear power plants is fictitiously set at 33% according to official calculation methods (IEA, EUROSTAT: efficiency approach), since the nuclear fuel (e.g. uranium) cannot easily be assigned a type of calorific value (as with fossil energies) , d. H. physically / chemically there is no clearly defined primary energy. In relation to the total fission energy of U235, the efficiency of a nuclear power plant is almost 10%. With this approach, however, the expense of reprocessing the fuel rods and the necessary disposal must also be taken into account.
  2. ↑ In various publications, the degree of conversion (water approx. 90%, wind approx. 50%, photovoltaics approx. 15%) is included in the efficiency analysis for renewable energies . This is wrong insofar as no primary energy is consumed in this process and the output energies are available free of charge or there is no generation and provisioning effort for the output energies. (See also source: Foreword to the energy balances for the FRG )
  3. ↑ The shutdown of many nuclear power plants in Germany since 2011 has not yet been included in this figure. This significantly improves the efficiency of overall electricity generation in Germany.

Well-to-tank in hydrogen production

In the case of hydrogen generation , the complex energetic upstream chain up to provision at the filling station must also be considered. In addition to production, the necessary compression (up to 700 bar for mobile use, max. 88%) or liquefaction (below 21.15 Kelvin or −253 ° C, max. 80% ) must be taken into account for the provision of hydrogen as a fuel  . ) and the transport (approx. 99%). For mobile applications today (2014), storage in pressure tanks is used exclusively, while for stationary storage of larger quantities mostly liquid tanks are used, which have losses due to outgassing without continuous consumption due to the inevitable warming. These energetic losses must be included in the efficiency analysis.

Standard (> 90% of all hydrogen) is currently the production from fossil primary energies, mainly the steam reforming from natural gas with an efficiency of approx. 75%. As with natural gas vehicles, the cost of gas production and distribution can be assumed to be approx. 86%. Together with the necessary compression and transport, this results in an overall efficiency of a maximum of 56.2%. When storing liquid hydrogen , the values ​​are significantly lower due to the expense for liquefaction and gassing losses.

The often cited electrolysis from water is more efficient with a maximum efficiency of 80%, but due to the previously necessary electricity generation as an electricity mix with 48.8% and the losses during compression and transport, the overall process (maximum 34%) is currently (2012) inefficient as a fuel generation mode. Hydrolysis could gain importance if only surplus electricity from renewable energies is used to generate it. The efficiency of hydrolysis with regenerative electricity and compression to 700 bar was specified for the Toyota FCHV- adv at 65%. The overall efficiency deteriorates if the electrical energy first has to be supplied via the power grid .

Processes for generating hydrogen from biomass can also achieve high levels of efficiency, but the provision of biomass must also be taken into account. Large-scale applications are not known in Germany. Biohydrogen is currently considered to be energetically and economically uneconomical.

Web links

  • Optiresource program for varying energy sources, fuels and drive concepts and comparing fuel consumption and CO₂ emissions

Individual evidence

  1. ^ Joint Research Center - Institute for Energy and Transport (IET), July 3, 2011: Well-to-Wheels Analyzes of future automotive fuels and powertrains in the european context (PDF; 1.6 MB), p. 11 "Pathways" , inserted April 18, 2011
  2. ↑ AM Foley, B. Smyth, B. Gallachoir, 2011: A Well-to-Wheel Analysis of electric Vehicles and greenhouse Gas savings (PDF; 75 kB), inserted April 18, 2012
  3. ↑ JRC, UBA, September 2013: Green gas emissions of various fuels and drive types , accessed September 22, 2014
  4. ↑ AMS, January 2009: Energiebrisanz  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , inserted January 26, 2012.@1@ 2Template: Dead Link / www.etha-plus.ch  
  5. ↑ Zeit online, July 2010: No electric car is completely clean , added January 26, 2012.
  6. ↑ Software tool for well-to-wheel comparisons: Optiresource , information and online simulation program, added January 26, 2012.
  7. ↑ Spiegel online, September 6, 2007: Profit thinking beats environmental protection , accessed January 8, 2017
  8. ^ Spiegel online, 22. September 2012: Natural gas - blown into the wind , accessed January 7, 2017
  9. ↑ a b Frischknecht / Tuchschmid for esu-services, December 18, 2008: Primary energy factors of energy systems (PDF; 796 kB), accessed August 4, 2012
  10. ↑ a b dena, September 2011: Demand and production of mineral oil in the future energy mix. , accessed December 22, 2014, link updated June 5, 2017
  11. ↑ Hamburger Abendblatt, December 14, 2011: Dirty energy from tar sand , accessed September 26, 2014
  12. ↑ Handelsblatt, January 10, 2011: [1] , accessed September 26, 2014
  13. ↑ Focus, September 25, 2009: New Myths about the End of Oil , accessed September 26, 2014
  14. ↑ Angelika Heinzel, University of Duisburg-Essen: Energy conversion techniques using the example of a refinery ( Memento from March 4, 2016 in the Internet Archive ), accessed December 22, 2014
  15. ↑ a b c d AG Energiebilanzen, November 2008: Foreword to the energy balances for the FRG ( Memento of April 9, 2014 in the Internet Archive ), inserted February 12, 2012
  16. ↑ Julian Affeldt, Matthias Hüttmann using a graphic from the Research Center for Energy Economics (Munich): Well-to-Tank: from borehole to tank . In: Sonnenenergie, official specialist organ of the German Society for Solar Energy e. V., magazine for renewable energies and energy efficiency . March 2018, ISSN  0172-3278 , p. 84, pages 24–27 ( sonnenenergie.de [PDF; accessed on August 13, 2018]).
  17. ↑ University of Berkeley, 2006: University of Berkeley Study of 2006 on Electric Mobility ( April 24, 2012 memento in the Internet Archive ), PPT, accessed August 6, 2012
  18. ↑ 60% "> BINE Information Service, September 20, 2011: The world's most efficient power plant opened , inserted February 23, 2012
  19. ↑ EnEV-2009, Annex 1, Section 2.1.1: Changes to the Energy Saving Ordinance , added February 24, 2012
  20. ↑ a b Ulf Bossel, Theory and Practice No. 1, 15th year, April 2006: Hydrogen does not solve energy problems , accessed September 26, 2014
  21. ↑ heise Autos, July 12, 2012: test drive in the Toyota FCHV-adv , inserted February 12, 2012