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Volvo ReCharge Concept: Plug-in hybrid with battery-only range of 100 km - and Flexifuel engine for backup power
6 September 2007
Volvo Cars is introducing the Volvo ReCharge Concept, a plug-in hybrid with individual electric wheel motors and batteries that can be recharged via a regular electrical outlet for maximum environmental benefit. Recharging allows the car to be driven about 100 kilometres on battery power alone before the car's four-cylinder Flexifuel engine is needed to power the car and recharge the battery. Volvo ReCharge Concept makes its debut in a specially designed Volvo C30 at the Frankfurt Motor Show.
"A certain proportion of electrical vehicles will be necessary to meet the CO2 emission demands of the future. Since the Volvo ReCharge Concept combines an excellent battery range with a backup combustion engine, it is a very interesting concept," says Magnus Jonsson, Senior Vice President Research and Development at Volvo Cars. The ReCharge Concept has been developed at the Volvo Monitoring and Concept Center (VMCC), the Volvo Car Corporation's think-tank in Camarillo, California.
"This is a ground-breaking innovation for sustainable transportation. A person driving less than 100 kilometres a day will rarely need to visit a filling station. In the USA, this may apply to almost 80 percent of drivers," says Magnus Jonsson. Thanks to the excellent electrical range from a fuel consumption angle, the Volvo ReCharge Concept is exceptionally kind to the car owner's wallet.
When driving on electric power only, operating costs are expected to be about 80 percent lower than that of a comparable petrol-powered car. When driving beyond the 100 km battery range, fuel consumption may vary from 0 to 5.5 litres per 100 km depending on the distance driven using the engine.
"This plug-in hybrid car, when used as intended, should have about 66 percent lower emissions of carbon dioxide compared with the best hybrid cars available on the market today. Emissions may be even lower if most of the electricity in intended markets comes from CO2-friendly sources such as biogas, hydropower and nuclear power," says Magnus Jonsson.
An electric motor at each wheel
The Volvo ReCharge Concept combines a number of the latest technological innovations into a so-called "series hybrid" where there is no mechanical connection between the engine and the wheels.
- The battery pack integrated into the luggage compartment uses lithium-polymer battery technology. The batteries are intended to have a useful life beyond that of the car itself.
- Four electric motors, one at each wheel, provide independent traction power.
- Four-cylinder 1.6-litre Flexifuel engine drives an advanced generator that efficiently powers the wheel motors when the battery is depleted.
Electric car with a combustion engine as backup
In principle, the Volvo ReCharge Concept is a battery electric car with an efficient generator, an Auxiliary Power Unit (APU), that steps in when battery charge becomes insufficient for adequate driving performance. The APU is designed to distribute electrical power to the individual motors at each wheel. Since the combustion engine only powers the APU, it can operate in an optimal fashion, both for regulated emissions and CO2. The APU is sufficiently powerful to supply an entire villa with electricity. For example it could with minor modifications in principle give the car owner an electricity generator right at his front door in the event of a power failure.
The driver can choose the power source
The combustion engine starts up automatically when 70 percent of the battery power has been used up. However, the driver also has the option of controlling the four-cylinder Flexifuel engine manually via a button in the instrument panel. This allows the driver to start the engine earlier in order to maximize battery charge, for instance when out on the highway in order to save battery capacity for driving through the next town.
"There is a considerable difference between our plug-in hybrid and today's hybrids. Today's hybrids use the battery only for short periods to assist the combustion engine. Our solution is designed for most people to run on electric power all the time, while providing the extra security that comes with having a combustion engine as a secondary source of electrical power," says Ichiro Sugioka, project manager for the Volvo ReCharge Concept. He adds: "What is more, our C30 with plug-in hybrid technology retains its lively and sporty driving properties. Acceleration from 0-100 km/h takes 9 seconds and top speed is 160 km/h."
Specially developed electric motors
The central electrical components in the Volvo ReCharge Concept demonstrator - the generator for the APU and the wheel motors - were developed together with British electromagnetic specialists PML Flightlink. With an individual electric motor at each wheel, weight distribution as well as mechanical efficiency and traction are maximized. The friction in mechanical gears is eliminated. Since the car does not have the transmission found in ordinary cars, there is no need for a gear lever.
To help maximize the environmental benefits, the Volvo ReCharge Concept has high-efficiency tyres developed by Michelin. They are specially designed to accommodate the wheelmotors. Further more, the car has All Wheel Drive in the truest sense of the term. Power to each wheel is controlled individually. The energy that is generated during braking is transmitted to the battery pack. When the system is ultimately developed, traditional wheel brakes will be completely replaced by electrical brakes with minimal energy wasted through friction. To ensure reliable operation of the drivetrain and braking system, driver inputs are fed into a quadruple-redundant electronic control system.
Ecologically sound solution for commuters
The Volvo ReCharge Concept is best suited to car drivers who cover moderate distances every day. For example, a commuter who has less than 100 kilometres (62 miles) to drive between home and workplace can cover the entire round trip on electric power alone and the equivalent daily fuel economy will be zero litres per 100 km.
Even drivers who cover more than the battery-only range will benefit from the ReCharge Concept. For a 150 km (93 mile) drive starting with a full charge, the car will require less than 2.8 litres of fuel, giving the car an effective fuel economy of 1.9 l/100km (124 mpg).
"The only requirement is that the car owner has access to electrical outlets at convenient places, such as at home or at the workplace. A full recharge takes 3 hours. However, even a one-hour quick charge should provide enough charge to drive about 50 kilometres," says Magnus Jonsson.