Team Tennessee's EcoCAR2 vehicle is a Series-Parallel Plug-In Hybrid Electric Vehicle (PHEV). The front drive consists of a 2.4L General Motors LE9 engine mated to a 6T40 transmission. The engine is also coupled to a UQM SR218H generator. The engine will be fueled with E85, a fuel mixture comprised of 85% ethanol and 15% gasoline. The rear drive features a Remy HVH250-115A motor mated to a BorgWarner eGearDrive. The energy storage system incorporates seven 15s2p modules from A123 Systems, providing a nominal 340 volts with 40 Ah capacity. The vehicle will have a 55 kilometer charge-depleting range, after which the vehicle may be operated as either a series or parallel hybrid. The series-parallel architecture allows for a blended energy consumption strategy which maximizes power efficiency with two modes.
Series Mode Series mode allows the engine to operate at its highest efficiency point, and the electric vehicle operation can be utilized to carefully bring the engine online in order to optimize catalyst warming and reduce harmful start-up emissions.
The Controls Team recently fixed some issues with the controller for transmission shifting. They adjusted the wiring within the onboard charger to improve the signal transmission quality. The energy storage system and rear electric motor is currently being connected to a dynamometer to complete operational testing. Testing will be completed within the next week so that the group can continue on to disassembling the bench test and begin the integration of all subcomponents back into the vehicle.
Parallel Mode In parallel mode, the engine is tied directly to the front wheels, and the electric traction drive powers the rear wheels. At times of peak power demand, the vehicle will use both series and parallel modes in combination.
Fuel Team Tennessee's vehicle will be fueled by both electricity and E85 (a blend of 85% ethanol and 15% gasoline). The design will implement a battery which can be plugged in for recharging and will be used in accordance with E85 to maximize efficiency. Ethanol is a domestically produced, renewable fuel which has reduced lifecycle greenhouse gas emissions when compared to gasoline. Ethanol is currently primarily produced from corn, but major research has advanced the development of cellulosic ethanol. Cellulosic ethanol production is more advantageous as it offers more substantial amounts of ethanol in production to satisfy the U.S. market because cellulosic ethanol is produced from plant waste products or grasses which can be grown on marginable land. Ethanol also reduces greenhouse gas (GHGs) emissions by almost 52% and advancements with cellulosic ethanol have shown reduction of GHGs by as much as 86 %. This extensive reduction comes from a balance between the carbon dioxide released when ethanol is burned and the amount of carbon dioxide taken in by the plants grown to produce the various feedstocks.
The mechanical updates for Year 3 are composed of two parts: resolving the shortcomings of rushed Year 2 build, and refining the Malibu to near showroom quality for competition. The focus of the first half of the year is to revise the rear subframe and five-bar designs, accept the new orientation of the rear traction motor, and to update the PTU sprocket sizing to improve the chain tension, which caused the team trouble in Year 2. Next, the team will focus on light weighting, improving drive-ability and packaging optimization.
Vehicle Modeling Team Tennessee's vehicle design showed approximately a 45% improvement in fuel economy when compared against industry leading hybrid vehicles. This improvement in fuel economy along with the utilization of E85 for fuel leads to nearly a 53% decrease in greenhouse gas emissions. Team Tennessee's design showed improvements in fuel economy and GHG emissions, while also improving the 0-60 mph time, as well as decreasing the 50-70 mph time by 50%, over the conventional gasoline vehicle. This design demonstrates that with the right combination of technology and innovation, there does not need to be any compromise between environmentally friendly vehicle architecture and exceptional performance.
Team Tennessee is removing the compromise between having a vehicle that can perform and a vehicle that gets great fuel economy. The series-parallel plug-in hybrid vehicle design allows the best of both worlds.
Team Tennessee's combination of vehicle architecture and fuel choices creates a vehicle that is projected to be 45% more fuel efficient and produces 53% less GHG emissions than industry leading hybrid vehicles. This was determined through simulated drive cycle testing during Year 1 of the EcoCAR 2 competition.
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