There’s no doubt that plug-in hybrids loom large on the minds of drivers today. One might assume this is a recent phenomenon given the constant media attention today. But really, this has been an ongoing area of interest for quite some time. In fact, some 17 years ago, Green Car Journal technical editor Bill Siuru penned a feature offering an overview of this interest. This article from our archives is worth sharing today since it not only indicates the reasons why plugging in is such a positive thing, but considering the interest at the time, it also illustrates the surprisingly long time it has taken to reach where we are today. Other revelations are included here, like the potential for vehicle batteries to be used for V2G (vehicle-to-grid) and V2H (vehicle-to-home) energy, and of course Volvo’s growing commitment to its electrified future. Here, we present this article from Green Car Journal’s fall 2007 issue.
Excerpted from Fall 2007 Issue: The tremendous interest in plug-in hybrid vehicles (PHEVs) is driven by many things, from a desire for greater fuel efficiency to decreasing emissions, achieving long-term reductions in fuel cost, and promoting energy diversity so we’re much less dependent on imported oil. Each of these is important to our future. Together, they make a compelling case for the PHEV that bears further exploration.
Plug-In Hybrids Offer EV Benefits
Plug-in hybrids could provide most of the environmental and fossil fuel-savings benefits long promised by battery electric vehicles (BEVs), but not yet delivered. Also called grid-connected hybrids, PHEVs overcome the biggest challenge of BEVs – insufficient range. With all-electric range of up to 60 miles, under most driving scenarios a PHEV can be a true zero-emission vehicle (ZEV), just like a BEV. In reality, however, plug-in hybrids offer much more since gasoline-electric hybrid power is ready to take over from all-electric drive once battery energy is depleted.
Initially, aftermarket suppliers like EnergyCS in California and Hymotion in Canada developed PHEV retrofit kits for popular hybrids like the Toyota Prius, Ford Escape Hybrid, and Mercury Mariner Hybrid. These have been quite expensive and aimed exclusively at fleets because of cost. Major automakers have now joined in. General Motors’ much-publicized Chevy Volt will be a PHEV with an all-electric range of 40 miles. According to GM, 75 percent of all commuters drive 40 miles or less to and from work. A plug-in Saturn Vue hybrid, in the works and possibly available in advance of the Volt, could double the fuel economy of any current SUV and provide some 10 miles of electric-only propulsion. Toyota, Nissan, Ford, and several other manufacturers have PHEVs in the works, as well.
Series PHEV Advantages
While most hybrid cars, SUVs, light trucks, and PHEVs unveiled to date are parallel hybrids, several have followed a different approach with a series hybrid configuration. One of the latest is the Volvo ReCharge Concept. The ReCharge series hybrid uses an internal combustion engine solely to drive a generator for producing electricity that powers the vehicle’s electric motors. Essentially, the ReCharge is a battery electric vehicle with an internal combustion engine for range extension. This drive configuration allows the 1.6-liter, four-cylinder Volvo Flexifuel engine to operate in its optimum rpm range for best fuel economy and minimum emissions. An added advantage when not directly connecting an internal combustion engine to the wheels is much more design flexibility.
In this instance, the ReCharge uses four individually controlled electric drive motors for all-wheel drive. Individual wheel motors also allow optimum weight distribution and maximizing both traction and mechanical efficiency. Since a transmission is no longer needed, mechanical gear friction is reduced substantially. The ReCharge can run on battery power alone for just over 60 miles and also operate its engine on biofuels like E85 ethanol, all the while retaining the sporty performance of the Volvo C30 sport coupe on which it is based. For a 93 mile (150 km) drive starting with a full charge via an ordinary electric outlet, it will use less than three-quarters of a gallon of fuel, which equates to almost 125 mpg. A driver would rarely need to fill up the tank if driven less than 60 miles daily.
Plug-In Hybrid Versatility
PHEVs offer us more than just emissions reduction and increased efficiencies. They also have the unique ability to supply large amounts of electrical power for uses other than just propulsion. This feature is being exploited in the plug-in hybrid Trouble Truck Project by a consortium consisting of the Electric Power Research Institute, Eaton, Ford Motor Co., and California’s South Coast Air Quality Management District. Trouble trucks, used by utility repair crews, are typically operated in residential neighborhoods. Since their internal combustion engines are left idling to power buckets, power tools, lights, and accessories, emissions and noise occur at job sites as a matter of course. Providing power through a PHEV’s battery and electrical system means continuous engine operation is no longer needed.
These PHEV trouble trucks use Eaton’s parallel pre-transmission hybrid system with either a Ford 6.8-liter V-10 gasoline engine or 6.0-liter V-8 diesel engine. Along with reducing consumption and emissions while traveling to and from worksites, the PHEV trouble trucks provide engine-off cab air conditioning and standby AC electrical generating capacity, including 5 kW of exportable power for at least six hours to power equipment. PHEV trouble trucks based on Ford’s F-550 truck chassis are used by Southern California Edison, Los Angeles Department of Water and Power, and Pacific Gas & Electric. This project will later expand to 50 Ford F-550-based trucks and E-450-based vans for utility and public fleets. Since the F-550 and E-440 chassis are widely used as shuttle buses, urban delivery trucks, cable service trucks, and even motorhomes, there’s every potential that volume production could reduce per-vehicle cost. In fact, PHEV technology could find a home in high-end motorhomes where, perhaps in conjunction with solar panels, it could replace noisy and polluting generators typically used to power on-board electrical components while parked.
Feeding the Grid with V2G
PHEVs can produce so much electricity that excess energy could be supplied to the electrical grid using vehicle-to-grid (V2G) technology. V2G allows two-way sharing of electricity between PHEVs, BEVs, and the electric power grid. With V2G, an electric or plug-in hybrid vehicle not only could be plugged in for battery recharging, but under certain conditions could also send electricity back from the batteries to the grid. For instance, vehicles could store electrical energy generated during off hours for use during peak power demands. This would eliminate the need for utilities to buy expensive overcapacity electricity on the spot market or fire up older, and high-polluting, fossil fuel ‘peaker’ generating plants. To encourage consumers to participate in a V2G program, utilities could pay motorists for the use of their PHEV or BEV, or owners could sell back energy to the utility when demand is highest.
In what’s called V2H – or emergency home backup – a PHEV could be used for emergency power. For instance, the PG&E demonstrator supplies 9 kW hours of electricity and the average home uses about 2.5 kW of electricity an hour, which means that hours worth of backup power is available if needed. Volvo says the ReCharge Concept’s efficient generator, essentially an Auxiliary Power Unit (APU), is powerful enough to supply an entire house with electricity. Thus, with minor modifications it could be used in case of a power failure.
Practical Limitations of the PHEV
Like the BEV, the practicability and affordability of the PHEV is governed by battery technology and cost. Its greater all-electric range capability requires larger, heavier, and much more expensive battery systems to store additional electric energy. Plug-in hybrid Dodge Sprinter vans have a 14 kW-hour nickel-metal-hydride or lithium-ion battery system that provides 20 miles of electric-only power. In contrast, the Prius uses a 1.5 kW-hour battery pack for normal gasoline-electric hybrid operation. Ordinary hybrids require batteries that supply short bursts of electrical boost with a nearly constant state-of-charge to ensure battery longevity. PHEV batteries must provide this high power burst while additionally handling full charge to deep discharges like a BEV. Another concern focuses on whether enough electric power will be available should PHEVs become extraordinarily popular. However, a study by the Department of Energy’s Pacific Northwest National Laboratory says the nation’s existing electric power grid could support up to 180 million PHEVs.
All this is unfolding, now. Technology marches on, costs diminish through efficiencies, and interest drives further development...all good things that should bring the plug-in hybrids we desire to our highways sooner than later.