JEC updates well-to-wheels study on automotive fuels and powertrains; electro-mobility, natural gas and biofuels
|WTW energy expended and GHG emissions for conventional fuels ICE and hybrid vehicles shows the potential for improvement of conventional fuels and ICE based vehicles. Source: EUR 26236 EN - 2014 Click to enlarge.|
Europe’s Joint Research Centre (JRC) and its partners in the JEC Consortium—JRC, EUCAR (the European Council for Automotive R&D) and CONCAWE (the oil companies European association for environment, health and safety in refining and distribution)—have published a new version of the Well-to-Wheels Analysis of Future Automotive Fuels and Powertrains in the European Context. (Earlier post.)
The updated version includes a longer-term outlook by expanding the time horizon from 2010 and beyond to 2020 and beyond. It adds an assessment of electrically chargeable vehicle configurations, such as plug-in hybrid, range extended, battery and fuel-cell electric vehicles. It also introduces an update of natural gas pathways, taking into account the addition of a European shale gas pathway. Furthermore, biofuel pathways, including an entirely new approach to NOx emissions from farming, were thoroughly revised.
The authors also changed the vehicle simulation tool from ADVISOR to AVL CRUISE.
The report aims to establish a consensual well-to-wheels (WTW) energy use and greenhouse gas (GHG) emissions assessment of a wide range of automotive fuels and powertrains relevant to Europe in 2020 and beyond. A specific objective is to have the outcome accepted as a reference by all relevant stakeholders, including industry, academia and government.
In 2003 JEC issued its first Well-to-Wheels study, a type of analysis which takes into account the entire energy lifecycle of fuels and powertrains and their possible combinations. It has been updated at regular intervals according to new data and conditions.
In the new report, the authors observe that while a shift to renewable/low fossil carbon routes may potentially offer significant reductions in GHG, it also generally requires more total energy; i.e., the specific pathway is critical.
They also note that large-scale production of synthetic fuels or hydrogen from coal or gas offers the potential for GHG emissions reduction—but only if CO2 can be captured and stored.
ICE-based vehicles and fuels. Broadly, the study found that ongoing developments in gasoline / diesel engine and vehicle technologies will continue to contribute to the reduction of energy use and GHG emissions.
Hybridization can provide further energy and GHG emission benefits. Accordingly, the efficiency gap between SI (spark ignition) and CI (compression ignition) vehicles is narrowing, especially for hybrid versions.
The hybridization option investigated brings an additional energy and GHG reduction of about 30% for gasoline and 20% for diesel hybrid vehicles. Further optimisation of hybrid configurations may bring additional savings in the future.
Methane. Today, the WTW GHG emissions for CNG lie between gasoline and diesel. Beyond 2020, greater engine efficiency gains are predicted for CNG vehicles—WTW GHG emissions will approach those of diesel. However, WTW energy use will remain higher than for gasoline.
The origin of the natural gas and the supply pathway are critical to the overall WTW energy and GHG balance. Biogas, particularly from waste materials, has a very low GHG impact, whether the biogas is used to fuel cars or produce electricity. Producing synthetic gas (SNG) from wind electricity (e.g., e-Gas) and captured CO2 (from CCS) results in low GHG emissions but needs energy. LPG provides a small WTW GHG emissions saving compared to gasoline and diesel.
Alternative Liquid Fuels. Numerous pathways can produce alternative liquid fuels that can be used in blends with conventional fuels and, in some cases, neat, in the existing infrastructure and vehicles.
The fossil energy and GHG savings of conventionally produced bio-fuels such as ethanol and bio-diesel are critically dependent on manufacturing processes and co-products. The lowest GHG emissions are obtained when co-products are used for energy production.
The GHG balance of biofuels is particularly uncertain because of nitrous oxide emissions from agriculture. Land use change may also have a significant impact on the WTW balance. In this study, the researchers modeled only biofuels produced from land already in arable use.
When upgrading a vegetable oil to produce road fuel, the trans-esterification and hydrotreating routes (for fatty acid methyl ester biodiesel and drop-in renewable fuels, respectively) are broadly equivalent in terms of GHG emissions.
Despite the fossil energy savings resulting from the above biofuels, these pathways are not energy-efficient. Taking into account the energy contained in the biomass resource, the total energy involved is two to three times higher than the energy involved in making conventional fuels. These pathways are therefore fundamentally inefficient in the way they use biomass, a limited resource.
ETBE can provide an option to use ethanol in gasoline as an alternative to direct ethanol blending. Fossil energy and GHG gains are commensurate with the amount of ethanol used.
Processes for cellulosic ethanol production are begin developed, and offer both an attractive fossil energy and GHG footprint.
High quality diesel fuel can be produced from natural gas (GTL) and coal (CTL). GHG emissions from GTL diesel are slightly higher than those of conventional diesel, while those from CTL diesel are considerably higher.
New processes are being developed to produce synthetic diesel from biomass (BTL), offering lower overall GHG emissions, though still high energy use. Such advanced processes have the potential to save substantially more GHG emissions than current bio-fuel options.
Dimethyl ether. DME can be produced from natural gas or biomass with lower energy use and GHG emissions results than other GTL or BTL fuels. DME being the sole product, the yield of fuel is high. Use of DME as automotive fuel would require modified vehicles and infrastructure similar to LPG.
The black liquor route which is being developed offers higher wood conversion efficiency compared to direct gasification in those situations where it can be used and is particularly favorable in the case of DME.
Externally chargeable vehicles and fuels. There is a range of options for vehicles designed to use grid electricity ranging from battery vehicles (BEV) which use only electric power, to Range-Extended Electric Vehicles (REEV) and Plug-In Hybrids (PHEV) which in turn provide a greater proportion of their power from the ICE.
While electric propulsion on the vehicle is efficient, the overall energy use and GHG emissions depend critically on the source of the electricity used.
Where electricity is produced with lower GHG emissions, electrified vehicles give lower GHG emissions than conventional ICEs, with BEVs giving the lowest emissions.
Where electricity production produces high levels of GHG emissions, the PHEV20 configuration emits less GHG than the other xEVs. This is because it involves less electric driving than the BEV and REEV.
The differences in performance between PHEV and REEV technologies are primarily a function of the different assumed electric range (20 km vs. 80 km, or 12.4 miles vs. 50 miles) rather than a differentiator between the technologies themselves.
Fuel cell vehicles and hydrogen. Developments in fuel cell system, tank and vehicle technologies will allow fuel-cell vehicles to become more efficient in the 2020+ timeframe and increase their efficiency advantage over conventional vehicles.
Previous versions of this study showed that WTW GHG emissions savings can only be achieved if hydrogen is used in fuel cell vehicles (i.e., not for combustion). For hydrogen as a transportation fuel virtually all GHG emissions occur in the WTT (well-to-tank) portion—i.e. during production—making it particularly attractive for CO2 Capture & Storage.
Many potential hydrogen production routes exist; however, the benefits are critically dependent on the pathway selected.
Hydrogen from natural gas (NG) used in a fuel cell at the 2020+ horizon has the potential to produce half the GHG emissions of a gasoline vehicle.
Electrolysis using EU-mix electricity or electricity from NG results in GHG emissions two times higher than producing hydrogen directly from NG and gives no benefit compared with a gasoline vehicle.
Hydrogen from non-fossil sources (biomass, wind, nuclear) offers low overall GHG emissions.
Using hydrogen as a cryo-compressed fuel increases GHG emissions by about 10% compared to the compressed gaseous form with 70MPa.
Alternative uses of primary energy resources. At the 2020+ horizon, CNG as transportation fuel only provides small savings because its global GHG balance is close to that of the gasoline and diesel fuels it would replace.
With the improvements expected in fuel cell vehicle efficiency, production of hydrogen from NG by reforming and use in a FC vehicle has the potential to save as much GHG emission as substituting coal by NG in power generation.
Using farmed wood to produce hydrogen by reforming saves as much GHG emission per hectare of land as using the wood to produce electricity in place of coal and saves more GHG emissions per hectare than producing conventional or advanced biofuels.
When sourcing wind electricity for transport fuels, hydrogen production and use in FCEV is more efficient than the application of synthetic diesel or methane in ICE-based vehicles.
Using wind electricity to produce hydrogen and using it in FCEV saves slightly less GHG emissions than substituting NG CCGT electricity.
Using wind electricity as a substitute for coal electricity is the most efficient option for GHG savings.
JEC WELL-to-WHEELS Report Version 4.a (Report EUR 26236 EN - 2014)