Last week, I had the pleasure of attending a meeting of the Power & Energy Society of the IEEE Boston Section. The topic was plug-in hybrid electric vehicles (PHEVs) and the speaker was Alan Millner, of MIT Lincoln Laboratory, whose areas of interest include energy and hybrid vehicles.
He noted these hybrids potential to reduce fossil fuel use and emissions, along with introducing more renewable resources for transportation—but likewise touched on the cost of their lithium-ion batteries, which are currently "too expensive," exacting a large price penalty (with a similarly long "payback" period) that will deter many from buying a PHEV.
However, in presenting study results, Millner showed PHEV operation can be enhanced in three ways to improve their economics. First, the incorporation of GPS information into the car’s energy management algorithm would allow predictive control through prior knowledge of the route and energy required—so that fuel consumption is optimized and reduced.
Second, the use of the vehicle battery while parked (vehicle to grid, or V2G) can provide additional revenue to the owner to offset the expense of the battery. A specific version of V2G, called vehicle to building (V2B), offsets the short peaks in commercial-scale facility electrical demand (such as where the driver recharges his vehicle at work during the day) to reduce his/her employer's electricity charges. Revenue provided the driver from V2B can pay for most of the battery cost (say $100/month) over the vehicle life. And reducing facility demand, if widespread, also lowers need to build new power generation capacity.
Third, battery-cycle life must be maximized to avoid high replacement costs. Millner presented a model of battery wear out for lithium-ion batteries, and how lifetime can be extended with good practices (cooling/heating and charge level control).
The enhanced PHEV is then seen to have improved economics, helping bootstrap the technology into wider acceptance and economies of scale.
For the Lab Note that was the basis of Millner's presentation, click here. The note also includes a discussion of non-plug-in (Prius) and "conventional" plug-in (Chevy Volt) hybrid battery-use algorithms.
Alan Millner was a principal in a pioneering photovoltaic systems firm. He has developed switch mode power electronics for medical MRI and ultrasound systems, propulsion motors for marine applications, and power electronics for industrial applications up to 30 kW. He has authored 11 patents.