Electric Aircraft Symposium Westin Hotel, Millbrae, California Automotive Hybrid Experience Applied to Electric Aircraft Design by Marc W. Wiseman, Ph.D., Divisional Product Group Director, Advanced Technology and James C. Paul, P.E., Senior Engineer and Business Development Manager Ricardo, Inc. NASA PAV Concept Shadow 200 UAV www.cafefoundation.org http://www.designation-systems.net/dusrm/app2/q-7.html Electric Aircraft Symposium Westin Hotel, Millbrae, California 23 May 2007

The auto industry has evaluated a wide range of hybrid schemes Automotive Hybrid Experience Applied to Electric Aircraft Design The auto industry has evaluated a wide range of hybrid schemes Electrical Machines Power Transmission Energy Storage Thesis www.evworld.com/press/sandia_lithium-ion.jpg  The automotive industry has made significant progress in the area of electric vehicle (EV) and hybrid-electric vehicle (HEV) drive systems. This experience can be leveraged to support development of electric and hybrid-electric PAVs and UAVs. Energy storage, on-board power generation, vehicle modeling and integration, electric machines, and controls/power electronics will be discussed. Possible integration of these technologies into future aircraft designs will be explored.  NASA PAV Concept Shadow 200 UAV  

Automotive Hybrid Experience Applied to Electric Aircraft Design Company Overview

Ricardo has been involved in hybrid vehicle development since 1999:. 1 Ricardo has been involved in hybrid vehicle development since 1999: 1. Proprietary programs for OEMs, component suppliers, government agencies, military. 2. Ricardo internal R&D programs Selected Projects GVWs have ranged from 3.5 to 25 tons. HyTrans i-MoGen Ford Escape HEV Efficient-C Micro Hybrid Mild Hybrid Full Hybrid Optimum Efficiency US Government Advanced Hybrid Vehicles Hybrid Refuse Truck Military/Off-road

Projects have spanned the full range of hybridization, from “micro” to “full” Mild Full Commercial

Ricardo’s hybrid experience includes over 120 dedicated development engineers & consultants Program management Capabilities Current technology analysis Market characteristic assessment Opportunities assessment Technical trend assessment Program planning business case development Program support & guidance Powertrain and Vehicle Production design and release Vehicle engineering & system simulation Engine and transmission design and development for hybrids Prototype and pre-production build Controls and Electronics System simulation Control strategy development Embedded software development Software tools Hardware-in-the-loop application Electric Machines, Power Electronics and Energy Storage Motor development Electronic hardware (including power electronics) development and validation Energy storage modelling, test and validation Ricardo is experienced in developing corporate strategies for hybrid vehicles

Ricardo has been actively engaged in advanced energy storage systems and integration into hybrids for over 6 years. Requirements definition and cost/benefit analyses for EVs, HEVs and PHEVs Mechanical design for vibration, shock and crash Pack design for cost, assembly and manufacture (DFx) Thermal design, analysis, development and validation Simulation and test, validation of battery system Control algorithm and software development for SOC/SOH Battery Management System (BMS) hardware design and validation Safety system integration, FMEA, and Hazard Analysis Supply chain management of subsystems Prototype manufacturing, validation and launch support Ricardo currently studying market potential for establishing a Center of Excellence for Energy Storage development in Michigan

Status of Automotive Hybrid Technology Toyota Prius Honda Civic Ford Escape Saturn Vue Nissan Altima Five OEMs have hybrid products on the market. Many offer more than 1 vehicle and most are working on at least their second generation of hybrid technology. Hybrids vehicles are low volume – key focus is on production quality of hybrid components to avoid warranty costs. Production targets include: Design for less than 100 ppm failures in vehicle (i.e zero failure). Design for 150k miles / 10 year life (equates to over 7500 hrs of operation time) Robust to significant vibration and shock forces. Robust to thermal temperature extremes. NiMH batteries are proving to have good cycle life and good calendar life. Lithium ion technology is being actively developed for next generation hybrid batteries. Good understanding is being gained of potential operating failure modes for hybrid systems and mitigation strategies.

Ricardo’s Current Aerospace Activities Focus on Unmanned Aerial Vehicles Aviation Week & Space Technology April 2, 2007 Wide range of applications, 1hp to 1000hp “Backpack” engine for suit cooling/local power “Powerpack” handheld genset engine Several UAV engine concepts, including High Altitude UAV heavy fuel engine demonstrator Helicopter powerplant concept for extended range

Ricardo’s Current Aerospace Activities UAVs span a wide size range, including sizes appropriate for PAVs Military applications are a primary driver for the UAV industry. Current goals are: Increased Endurance Reduced Noise Operate on Available Fuels Increased Payload Capacity Reduced Maintenance Improved Durability

Approach to Electric/Hybrid Aircraft Design Full-Throttle Power Available MSC.EASY5 Perform mission requirement/energy requirements trade-off studies using: Classical analysis (spreadsheets) Computer simulation  MSC.EASY5 Ricardo Powertrain Library Ricardo Engine Library Ricardo Fuel Cell Library Ricardo Electric Drive Library  Available libraries allow simulation of a wide range of power system designs to facilitate selection and sizing of components.

Approach to Electric/Hybrid Aircraft Design Backside of power curve: if speed is decreased, power must be added to hold altitude Design Propulsion System Based on Minimum Energy Mission Approach (takeoff, dash, cruise) Power Required Curve  Best Endurance Speed = Speed at Minimum Power (maximum time in air) Best Range Speed = Speed at Which the Ratio HP/V is a Minimum (the speed giving the greatest ratio of velocity to horsepower required). Assumes the thrust specific fuel consumption (lb/THP-hr) is essentially constant over the low HP range.   Speeds for Best Range and Endurance for Propeller-Driven Aircraft From: Dommasch Airplane Aerodynamics, Fourth Edition, Page 302

Approach to Electric/Hybrid Aircraft Design TOOLS Matlab Simulink, EASY5 Ricardo Powertrain Library for Simulink V-SIM (IPT) Ricardo Engine Simulation Libraries CAPABILITIES Duty Cycle Simulation (fuel consumption and emissions) Performance Simulation (Climb, Dash, Top Speed) Co-simulation with WAVE, FLOWMASTER, etc. Drive Cycle Simulation of a Light commercial Truck Motor-generator mechanical power Engine torque Set point versus actual speed Average fuel economy Battery state of charge Battery power Vehicle Control System Development

One challenge for Electric aircraft is the weight of the energy storage system. For the following example, Lithium-Ion Batteries were Selected as Being Representative of the Best Currently-Available Technologies for Energy and Power Density Example Operating Characteristics for UAV Target Weight 300 lbs [136 kg] Typical cruise power 6 HP [4.5 kW] Typical take off power 24 HP [18 kW] Estimated take off energy 3 kWh Estimated cruise energy 4.5kWh per hour of flight time. Estimated Automotive Li-ion Battery Characteristics Li –ion energy density 80 – 120 Wh / kg Li-ion max power density 1300 – 1600 W / kg Li-ion cont power density 800 – 1000 W / kg Current estimated battery life 5000 flights

Battery weight remains a challenge which limits flight time Calculations based on a 300 lb UAV The battery pack alone would be 300 lbs for a 3 hr flight time !! UAV weight !!! Example A holistic approach is needed to improve flight time by finding ways to reduce takeoff and cruise power, take weight out of all components.

AeroVironment Helios Aircraft with Solar Panels on Wings How can performance be improved if energy storage remains a limiting factor? Reduce drag, CD Reduce weight, W Improve efficiency, CL/CD Change mission profile (e.g. HP vs time history, improved take-off profiles) On-board power generation (e.g. solar cells) Improved energy storage systems  Traditional aircraft design approaches have included trade-offs between efficiency and performance with focus on performance. Electric aircraft will include similar trade-off studies, but the focus will be on minimizing energy use.  http://www.pvresources.com/en/helios.php AeroVironment Helios Aircraft with Solar Panels on Wings

To meet goal of 8hr+ flight time, efficiency improvements and alternative power sources are needed. Solar cells alone are not optimum solution Effort is required to reduce cruise power

Conclusions Automotive engineering practice is providing high quality, robust and long life electric motors, electronics and battery systems. Hybrid road vehicle technology is developing at a rapid pace with particular progress being made in the areas of 1) equipment costs (including manufacturing methods and economies of scale), 2) operational failure modes are well understood and mitigation strategies can be deployed, and 3) weight optimization methods. Current battery technology presents a challenge for achieving weight targets. Detailed analysis and a holistic approach to UAV/PAV design is required to meet mission requirements. Modeling tools are available to assist in configuration assessment and component sizing. Note possible technology development opportunity: DARPA-sponsored Vulture Program (5 year-aloft, 1000 lb solar/battery/fuel-cell powered aircraft).