Electric vehicles (EVs) are becoming less of a novelty—though a Chevrolet Volt or Nissan Leaf might still get the once-over in a local supermarket parking lot. So far, early adopters are gung-ho on their plug-in purchases, with the Volt topping Consumer Reports’ annual customer satisfaction index the last two years. But what will it take for these cars to make a dent in total U.S. auto sales? And could new EV technologies help address broader electric-utility grid issues? The following are four technology hurdles EVs may have to clear to make it onto U.S. roadways in significant numbers.
Build a better battery
Classic hybrid EVs (think the Toyota Prius) use nickel metal hydride batteries, but plug-in vehicles, including both electric/gasoline plug-in hybrid models (PHEVs)—such as the Volt—and pure-play battery electric vehicles (BEVs)—such as the Leaf—use lithium-ion (Li-ion) batteries. Today’s Li-ion batteries are heavy and expensive and are a big reason that EVs cost so much more than standard automobiles with internal-combustion engines. They have also raised fire concerns in some installations (it was smoke from Li-ion batteries that grounded Boeing’s 787 aircraft for several months earlier this year). For these reasons—and because energy storage, in general, is expected to be an enormous growth market over the next two decades—researchers are pursuing a range of technologies to improve the performance of Li-ion products and introduce entirely new chemistries.
Graphene is getting a lot of press these days as both a possible performance-booster for Li-ion batteries and as an energy-storage resource. It can be visualized as a lattice of carbon only a single atom deep; scientists consider it a two-dimensional material. Researchers have only recently begun developing means for manufacturing the material, which is, essentially, the same graphite at an atomic scale that is used in a No. 2 pencil.
Ever since Andre Geim and Konstantin Novoselov’s article documenting graphene’s successful production appeared in 2004 (winning them the 2010 Nobel Prize for physics), researchers have been excitedly exploring its energy-storage possibilities. Rice University researchers have found that applying a graphene layer to the anode of a small button-style Li-ion battery helped the device retain more than double the capacity of standard models. And University of California, Los Angeles, investigators have developed a new way to make microscale graphene-based supercapacitors (devices that charge and discharge much faster than batteries, with much greater energy density than standard capacitors), using the same DVD laser-based labeling technology found in everyday laptop and desktop computers.
Of course, Chengdu Liang, a lead researcher at the U.S. Department of Energy’s Oak Ridge National Laboratory (ORNL), pointed out that the road leading from basic research to product commercialization can be long and winding. Liang is heading a team that has developed a new class of inexpensive sulfur-based materials for use as a cathode in a battery that also incorporates an ORNL-created low-flammability, solid electrolyte material. The end product boasts approximately four times the energy density of conventional Li-ion batteries, according to Liang, and it doesn’t self-discharge—a problem with those traditional products.
With high energy density, greater safety and a low cost, ORNL’s lithium-sulfur battery seems to be a slam-dunk option for EV manufacturers. But, Liang pointed out, as with the equally promising graphene technology, moving from discovery to product design takes time.
“We solved the scientific problems for lithium-sulfur batteries,” he said. “Now it is [up to] the engineers to take over and develop the technology and devices.”
For electric utilities, broader EV adoption offers both challenges and opportunities. For example, EVs could pose challenges to local distribution transformers if multiple households in the same neighborhood chose to begin charging their vehicles at the same time. However, during peak-demand periods, EVs could become important electricity resources for supply-stressed utilities. Addressing both issues requires greater connectivity, both throughout the smart grid and at the individual inverter.
This is just the issue Ideal Power Converters (IPC), a startup based in Spicewood, Texas, has begun to address, with its multiport, commercial-sized inverters that are lighter and less expensive to install than today’s conventional models. The company uses advanced software to manage an energy-conversion process it calls “packet switching.” The design eliminates the bulk capacitors, power switches, filtering elements and isolation transformers that weigh down traditional offerings. Instead, an internal energy-storage element isolates the current, enabling its safe conversion, while also allowing a wall-mountable design that weighs in at a svelte 125 pounds.
“It is inherently isolated. We don’t need a reactive filter,” said CEO Paul Bundschuh. IPC’s hardware is generic enough to work in a range of applications, including EV charging equipment and photovoltaic (PV) panel connections. The onboard programming provides the instructions required to meet the needs of multiple applications. “We have a topology that’s inherently software-based.”
While IPC is marketing a two-port solution useful for connecting, say, PV panels or commercial EV charging equipment to the utility grid, the three-port hybrid equipment Bundschuh expects will hit the market by early 2014 is even more interesting. These devices, developed with the help of a Department of Energy Small Business Innovative Research grant, incorporate three bidirectional ports—one grid-connected alternating current port and two independent direct current ports, which could be connected in any combination of EV charging equipment, PV panel systems or energy-storage devices. The system allows power to flow in any mix between the ports with 96.5 percent efficiency, as weighted by the California Energy Commission.
Taking the place of multiple pieces of conventional conversion equipment, the IPC hybrid converter could make such highly touted opportunities as supplying EV-stored electricity to the grid much easier and less expensive, at least in applications where it makes sense.
“For fleets, this is a very attractive option,” Bundschuh said, noting the U.S. Department of Defense as one interested potential customer. Fleet owners may only use their vehicles a few hours a day, each, making them highly underused assets. “If you can take those fleet vehicles and use them as grid storage, that’s a pretty compelling opportunity.”
Look on the sunny side
The capability to tie PV panels and EV charging equipment together could become more important, especially as both EV and PV manufacturers are quickly developing new partnerships in residential and commercial settings. In some cases, these are strictly marketing arrangements intended to capitalize on broad environmental concerns that many EV and PV purchasers share. More interesting, though, some companies are beginning to pair the technologies, enabling true emission-free EV refueling.
Smart-energy research and consulting firm Navigant recently released a report detailing the cross-marketing opportunities available when the sun hits the road. With their larger advertising budgets, the report states, automakers could boost their environmental credentials by promoting their association with green PV technology. And providing consumers with financing or other PV incentives at the time of EV purchase could mean better designed and less expensive grid connections from the electrical contractors installing the equipment.
Honda already has inked an agreement with national installer and leasing firm SolarCity in which the two companies established a $65 million investment fund to back solar installations by Honda customers. SolarCity pioneered a residential solar-sales model in which homeowners face no upfront costs. The company essentially leases space on homeowners’ roofs, paying them back with lower electricity rates. SolarCity retains ownership of the equipment, along with applicable tax benefits. Honda seems to be becoming an investor in this plan with this new partnership, and it is adding more polish to its image by providing favorable financing for a limited number of its dealers to install PV panels on their facilities’ rooftops.
Honda and SolarCity may be trying to draw an indirect line for EV owners who are concerned about the resources used to generate the electricity for powering their vehicles. In areas where coal is the primary generating fuel, for example, EV operation won’t be as carbon-neutral as owners of plug-in autos might like. Adding rooftop PV panels could help offset some of the coal-based energy those cars consume.
Startup EV manufacturer Tesla—whose founder and CEO Elon Musk is also SolarCity’s chairman—is making this connection more explicit in a number of PV-topped supercharger stations it is building across the United States to serve the growing number of its own automobiles. But, again, the panels will offset the electricity used in each fill-up, not supply it directly.
The challenge for true, off-grid PV charging is obvious: what do you do when the sun isn’t shining? Energy storage would need to be a part of any solution, which takes us back to the need for building better batteries.
A new generation of EVs equipped with connection ports capable of accepting higher voltage DC charging equipment is beginning to hit showroom floors, and faster commercial chargers now are being deployed across the United States. However, drivers will have to keep in mind just what connectors will work with their vehicles, if they want to take advantage of the technology that could get them to an 80 percent full charge in less than 30 minutes.
Most U.S. and European automakers will be incorporating designs based on the Society of Automotive Engineers’ “Combo” charger, while Nissan, Toyota and Mitsubishi support a Japanese standard known by its abbreviation, CHAdeMO. And then there’s Tesla, with charging ports that are unique to its products.
“For the near term, there are going to be two standards out there,” said John Gartner, Navigant Research’s smart transportation research director.
While the number of manufacturers backing the U.S.- developed Combo charger might argue for that technology’s eventual predominance, Nissan has gained an early lead with its CHAdeMO alternative, he said.
“It’s highly possible that Nissan will change its strategy for the North American market,” he said. “But that’s going to take time, especially since all the DC chargers [now] in place have been CHAdeMO.”