Improvements in electric-vehicle (EV) technology and fast-charging systems are driving down concern about “range anxiety”—fear of running out of power on the road. This is true for both fully electric battery-powered vehicles and hybrid gasoline/electric types. Calming that fear is necessary, given auto manufacturers’ commitment to electric powertrains to lower their fleet fuel-consumption averages.
Ford, for example, says electric vehicles (and autonomous operation) are its top priorities. Nissan engineers have boosted the range (and lowered the price) of the next iteration of the electric Leaf from less than 100 miles to around 150 miles. And General Motors recently announced that it will bring out two new EVs in the next 18 months—likely a sport model and a small SUV. These vehicles will be based on its Chevy Bolt compact battery electric with a listed range of 238 miles. GM plans to introduce roughly 20 electric and hydrogen-fuel-cell-powered models by 2023. Many of them will feature a next-generation electric architecture beyond that of the Bolt.
Such expansion in EV offerings and range will require growth in charging capabilities. It also will demand the expansion of the charging station infrastructure along with the numbers of charging points. The US Department of Energy National Renewable Energy Laboratory attempted to estimate how much charging capacity will be needed. In its just released National Plug-In Electric Vehicle (PEV) Infrastructure Analysis, the agency observes that charging-station numbers, capacity, and location hinge on many variables in a range of scenarios.
As noted by the study, one consideration is initial-market vehicle needs and the ramp-up to satisfy growing demands. Early PEV use sees most charging done overnight at home. As adoption and vehicle range increase, drivers will want to extend their utility. A few hundred strategically placed fast-charge stations in Interstate corridors could advance long-distance driving (Fig. 1).
A Wide Band of Numbers
The DoE analysis goes on to project local urban and rural charging requirements even greater than those needed for long-distance travel: a minimum of 8,000 fast-charging stations. Here is where all of this estimation gets tricky. With 15 million PEVs on the road, the number of “plugs,” not stations, needed is estimated to range from 100,000 to 1.2 million! Such a capacity disparity comes from projections of different vehicle fleet mixes (i.e., longer-range vs. shorter-range vehicle numbers) and whether those vehicles are plug-in hybrids or battery electric. Add to the mix consumer preferences for charging away from home or not, and the results diverge even more.
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Clearly, the numbers of charging sites needed will vary, depending on what plays out in terms of PEV adoption scenarios. It pays to take a look at the specific charging technology currently available and what is on the horizon, introducing further variables into the equation. Three types of charging-standard stations are now in use, along with the proprietary Tesla charging system that serves only its vehicles. (Teslas can use an adapter to charge at standard stations.)
The three standards are (Fig. 2):
- Level 1: This is charging via a US standard 110-V AC outlet, converting that to DC. It provides on the order of 1.0 to 1.5 kW, allowing most PEVs and lower-range electrics to fully charge overnight.
- Level 2: Here, charging is at 240 V AC to DC (7 – 9 kW), similar to a dryer or heavy-duty appliance outlet. Charge time is down to single-digit hours. These charging stations are the ones usually seen on the streets as well. In residences, they are installed by a licensed electrician. Many states offer rebates for their installation similar to financial incentives for plug-in vehicles, further fostering the technology’s adoption.
- Level 3: These are DC fast-charging stations for commercial locations putting out 50 kW. They can charge an EV significantly in, say, a half hour. However, there is no standard charging plug, with two types available in the U.S.
In addition, the Tesla supercharger noted previously outputs 120 kW for a 300-mile-range boost in about 75 minutes.
The Road Ahead
Various private enterprises are aiming to boost charging capability while filling the gaps in charging-station availability. One is Electrify America, a Volkswagen subsidiary created as part of the company’s settlement of its diesel-emissions cheating scandal (and an adjunct to its growing offering of electric vehicles). The enterprise has budgeted $2 billion over the coming decade for “workplace, community, and highway” charging infrastructure and education.
Electrify America will spend $800 million alone in California, one of the largest EV markets. Elsewhere in the US, over the next two years, the company plans on establishing about 240 charging stations (each including non-proprietary-connector Level 2 and four to ten fast DC chargers) along high-traffic inter-city routes. Concurrently, more than 300 similar community charging stations will be built at workplace, retail, multifamily residences, and parking facilities in the following cities: Boston, Chicago, Denver, Houston, Miami, New York, Philadelphia, Portland, Oregon, Seattle, and Washington, D.C.
On the horizon is 350-kW fast-charging technology. But issues with this technology may require more robust electrical cabling in vehicles to handle the higher power.
What about Wireless Charging?
An obvious question may be: why not eliminate the need for wired conductive charging and go wireless? While wireless power transfer (WPT) is available, high cost and the lack of a charging standard for vehicle and infrastructure compatibility are constraining its adoption.
Demystifying EV charging systems
However, the SAE has a draft WPT standard, J2954, in field test and plans to have it finalized “by 2018.” Technical considerations in the standard include: frequency band, safety, interoperability, electromagnetic-compatibility (EMC) and interference limits, and coil definitions. Expect to see wireless-charging options on high-end vehicles by the end of the decade.
Currently available is the Plugless WPT system from Evatran (Figs. 3 and 4). Here, a 2.7-inch high pad containing a transmitter coil inductively charges a “plug-in” vehicle adapter installed in the car and parked over it. Plugless specifications are 3.3 to 7.2 kW at 208 to 240 V AC—roughly Level 2 charging. With a nominal air gap of 4 inches, the company claims charging efficiency with air-gap losses is only about 12% less than conductive Level 2 charging (and 7% less than Level 1), for overnight recharge of most vehicles.
The Plugless system is currently available for only four plug-in vehicles: Tesla S, BMW i3, Nissan Leaf, and Chevy Volt. It ranges in price from $3,500 down to $3,000. For comparison, a Level 2 home charger at Home Depot goes from $400 to $800, highlighting the current high cost of “lazy-man (or woman)” charging.
This Just In…
Further highlighting the pace of EV developments, and adding to the milieu of technology improvement choices, Toshiba announced a breakthrough in its Super Charge ion Battery (SCiB). Current versions of these storage units are used on Mitsubishi and Honda EVs. Rather than a lithium titanium oxide anode, the upgraded battery uses a titanium niobium oxide and arranges the crystals to more efficiently store lithium ions for double the energy density. In a test, the company claims that in six minutes, on a “rapid charger,” enough energy is stored for three times the range refresh than with a battery having current Li-ion technology. First applications are expected to be on the road in 2019.
In the next couple of years, wider charging station availability coupled with greater EV charging capability will reduce charging times. These changes, and a ramp-up in wireless charging, should go a long way toward alleviating range anxiety for EV drivers. That point will become more moot as longer-range EVs enter the market. Eventually, range anxiety will be a thing of the past.