Idaho National Laboratory has released the voluminous findings from its analysis of five large-scale PEV and charging infrastructure projects funded by the American Recovery and Reinvestment Act. Collectively, these projects represent the largest-ever deployment, data collection and analysis, and reporting of PEV and charging infrastructure petroleum reduction benefits. The results will be used to support and refine activities of the US Department of Energy’s EV Everywhere Grand Challenge.
The key finding of INL’s assessment of the results was that public charging infrastructure is not needed everywhere to enable PEV adoption. Instead, the results suggest that charging infrastructure should be focused at homes, workplaces and public “hot spots” that serve multiple venues.
The five projects and technologies researched were:
- ChargePoint America: charging infrastructure
- Chevrolet Volts: extended range electric vehicles (EREVs)
- Chrysler Ram Pickup: plug-in hybrid electric vehicles (PHEVs)
- The EV Project: charging infrastructure, Nissan Leafs, Chevrolet Volts and Car2Go Smart EVs
- SCAQMD/EPRI/Via Motors: PHEV vans and pickups
Combined, ChargePoint America and The EV Project alone formed the largest PEV infrastructure demonstration in the world. Between 1 Jan. 2011, and 31 Dec. 2013, this combined project installed nearly 17,000 alternating current (AC) Level 2 charging stations for residential and commercial use and more than 100 dual-port direct current (DC) fast chargers in 22 regions across the United States.
More than 8,000 privately owned Nissan Leafs and Chevrolet Volts and more than 300 Smart ForTwo Electric Drive vehicles in Car2Go car-sharing fleets were enrolled in the project.
A commonly cited barrier to PEV adoption is the lack of public places for PEV drivers to plug in their vehicles. To reduce this barrier, DOE set out to answer a set of critical questions: How many and what kind of charging stations are needed? Where and how often do PEV drivers charge? How many electric vehicle miles are traveled and what level of petroleum reduction can be achieved?
Beginning in 2009, several resulting projects—Charge Point America project, Chrysler Ram PEV Demonstration, General Motors Volt Demonstration, South Coast Air Quality Management District/Via Motors PHEV Demonstration, and The EV Project—installed roughly 17,000 charging stations and deployed approximately 8,700 PEVs across the US. The DOE Office of Energy Efficiency and Renewable Energy provided half the funding for the five projects, and INL researchers collected and analyzed the resulting data.
Data collected from all five projects captured nearly 130 million miles of driving and 6 million charging events, providing the most comprehensive view of PEV and charging usage to date.
INL found that PEV private owners performed an average of more than 85% of charging at home. About half the project participants charged at home almost exclusively. Of those who charged away from home, the vast majority favored three or fewer away-from-home charging locations, and one or more of these locations was at work for some drivers.
This is not to say that public charging stations are not necessary or desirable. Many DC fast chargers (all of which were accessible to the public) experienced heavy use to support both in-town and inter-city driving. Also, a relatively small number of public AC Level 2 public charging sites saw consistently high use. This begs the question: what is it about the small number of highly used charging sites that led to their popularity?
There was some correlation between public charging location characteristics and utilization. Public Level 2 charging stations installed in locations where vehicles were typically parked for longer periods of time often were, in fact, among those most often used. These locations included shopping malls, airports and commuter lots, and downtown parking lots or garages with easy access to a variety of venues.
The study also found that drivers adjust their charging habits based on conditions such as fees and rules for use. When privately owned Volts are charged frequently, they achieved better than 120 mpg in normal consumer use patterns. Also, workplace charging was found to enable significant electric range extension. Project participants with access to charging at work were observed to drive 25% more on electricity alone than the overall group of vehicles in the project.
The project also illuminated other aspects of PEV use.
- Public and workplace charging infra-structure enabled drivers to increase their electric driving range.
- Drivers of the Chevrolet Volt, an extended-range electric vehicle, tended to charge more frequently and to more fully deplete their vehicle’s battery than drivers of the Nissan LEAF BEV. This allowed the overall group of Volts studied to average only 6% fewer electric vehicle (EV) mode miles traveled as the LEAFs in the project, despite the LEAF’s much larger battery pack.
INL suggested two reasons for this: first, Volt drivers tend to deplete their batteries fully, while LEAF drivers favored recharging with significant charge resident in their batteries. Second, Volt drivers plugged in more oftern than LEAF drivers.
- There are opportunities to use pricing structures and other policies to manage demand for PEV charging, both in terms of charging station through-put at charging hot spots and electricity demand on the electric grid.