Study Finds Coordinated Off-peak Charging Can Support Large Scale Plug-in Use Without Additional Generation Capacity; TCO and GHG Abatement Costs for BEVs Projected to Remain High
18 October 2010
Examining the potential impact of large-plug-in vehicle use in the context of the Netherlands, a study by Oscar van Vliet at the International Institute of Applied Systems Analysis and colleagues at Utrecht University concluded that, if off-charging is successfully introduced, electric driving need not require additional generation capacity, even in the event of a 100% switch to electric vehicles.
The study, in press in the Journal of Power Sources, examines the efficiency and costs of current and future EVs, as well as their impact on electricity demand and infrastructure for generation and distribution, and thereby on GHG emissions.
We therefore examine the feasibility of electric driving taking into account not only drivetrain choices, but also driving patterns, changes in the electricity mix, charging patterns, and energy losses in relevant parts of the WTW chain. There are three main aspects to this analysis:
- Determine the effect of EV charging patterns on household and total electricity demand.
- Derive GHG emissions and costs of charging of EVs in the 2015 Dutch context and beyond.
- Compare GHG emissions and costs of PHEV and BPEV with those of regular cars.—van Vliet et al.
The team used a compact 5-seater—e.g., Volkswagen Golf, Ford Focus, Renault Megane, Toyota Corolla and Opel Astra—in their analysis, and compared EV configurations to a regular gasoline car, diesel car, parallel hybrid car and series HEV (SHEV).
|“As lifestyles, working hours and household technology are fairly similar across industrialised nations and households, demand patterns without EV charging should be fairly consistent, except for higher use of air conditioners in the daytime in warmer climates. We therefore expect our findings on the impact of charging patterns on demand to be applicable to industrialised countries. ”|
|—van Vliet et al.|
All reference car configurations except the diesel use gasoline engines, because the purchase cost of gasoline engines is some €1500 lower than of diesel engines. The team assumed that gasoline engine-generators in SHEVs and PHEVs have the same efficiency relative to diesel generators as gasoline engines relative to diesel engines in regular cars. They also assumed a shift from current central motor (CM) drivetrains to wheel motor (WM) drivetrains from 2015 onwards because higher efficiency of wheel motor drivetrains allows for smaller and cheaper engines and battery packs.
They assumed an oil price of US$80/bbl, close to the short-term projections in the World Energy Outlook 2009.
They used an EV drivetrain with a single 74 kW central motor (CM) that consumes 103±20 Wh/km from 2010 and one with two 29kW wheel motors (WM) that consumes 89±19 Wh/km from 2015. In hybrid car configurations, these are powered by a gasoline-fuelled engine-generator that produces 53 kWe for a CM drivetrain and 46 kWe for a WM drivetrain with an efficiency of 31%. Building on the SHEV drivetrains, they assumed PHEVs with an electric range of 50 km (31 miles) and BPEVs with a range of 250 km (15 miles).
They used Li-ion batteries with a cost of €960/kWh in 2010, and assumed this reduces to €800 /kWh around 2015, and to €400/kWh in the more distant future. The Li-ion batteries have a specific energy of 86 Wh/kg, assumed to increase to 110 Wh/kg around 2015 and to 150 Wh/kg in the more distant future. They used a depth of discharge of 70%.
Among their findings:
Uncoordinated charging would increase national peak load by 7% at a 30% penetration rate of EVs and the household peak load by 54%, which may exceed the capacity of existing electricity distribution infrastructure. At 30% penetration of EVs, off-peak charging would result in a 20% higher, more stable base load and no additional peak load at the national level and up to 7% higher peak load at the household level.
GHG emissions from electric driving depend most on the fuel type (coal or natural gas) used in the generation of electricity for charging, and range between 0 g/km (using renewables) and 155 g/km (using electricity from an old coal-based plant). Based on the generation capacity projected for the Netherlands in 2015, electricity for EV charging would largely be generated using natural gas, emitting 35-77 gCO22 eq/km.
The total cost of ownership (TCO) of current EVs are uncompetitive with regular cars and series hybrid cars by more than €800/year. TCO of future wheel motor PHEV may become competitive when batteries cost €400/kWh, even without tax incentives, as long as one battery pack can last for the lifespan of the vehicle. However, TCO of future battery-powered cars is at least 25% higher than of series hybrid or regular cars. This cost gap remains unless cost of batteries drops to €150/kWh in the future. Variations in driving cost from charging patterns have negligible influence on TCO.
GHG abatement costs using plug-in hybrid cars are currently 400 to 1400 €/tonne CO may come down to -100 to 300 €/tonne. Abatement cost using battery powered cars are currently above 1900 €/tonne and are not projected to drop below 300-800 €/tonne.
We find that EV can be integrated into the Dutch grid with few additional investments apart from coordinated chargers. Using PHEV, this need not increase the cost of driving significantly and could reduce emissions from driving by more than 70% compared to diesel and petrol cars and by more than 55% compared to other hybrids that use petrol. We therefore recommend further development of electric drivetrains and batteries for use in SHEV and PHEV.
With respect to the possible future deployment of EV, we recommend further research into combining CHP with EV charging, effects of EV charging on local electricity distribution grids, cost developments of batteries and chargers, and the effect of driving patterns and different vehicle classes on EV fuel consumption. We also recommend integrating WTW analysis with analysis of energy and GHG emissions from EV manufacturing, as well as impacts of EV on non-GHG emissions, and investigating the possible role of EV in conjunction with other car alternatives, low or zero carbon fuels and green electricity in reducing GHG emissions.—van Vliet et al.
O. van Vliet, A.S. Brouwer, T. Kuramochi, M. van den Broek, A. Faaij (2010) Energy use; cost and CO2 emissions of electric cars, Journal of Power Sources, doi: 10.1016/j.jpowsour.2010.09.119
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