Supplemental Vehicle Power through Innovative Energy Harvesting

Principal Investigators
Mohammed F. Daqaq, John Wagner (Clemson U.)

Government
Mike Letherwood (TARDEC)

Student
Christopher Stabler (Clemson U.)

The power budgets in many military vehicles are increasing due to electric payloads (e.g., electric warfare technologies, sophisticated communication systems, online vehicle diagnostic devices, self-protection techniques, and improvised explosive devices defeat technologies). However, the in-vehicle power supply may not be designed to easily accommodate this demand and need for future growth. This research project will investigate the feasibility of utilizing energy harvesters as a supplementary power source which will increase the functionality and utility of ground vehicles. For example, the alternative power supply can be utilized to directly power in-vehicle electronics (with appropriate conditioning circuitry) or to charge different energy storage devices. It is interesting to note that this technology may also be applied to recharge portable communication equipment through motion such as walking or blowing wind.

The research project will investigate, conceptualize, model, and demonstrate two novel compact methodologies of electric power generation for ground vehicle operations using energy harvesting available from energy sources such as chassis vibrations, crankshaft rotations, and/or waste fluid flow from engine exhaust. The proposed techniques include piezoelectric vibration-based energy harvesting and magnetostrictive-based energy generation.

Figure 1: Schematic of a piezoelectric vibration-based energy harvester

Figure 2: Schematic of a Magnetostrictive generator

The first is Piezoelectric Vibration-based Energy Harvesting from Vehicle Suspension: Piezoelectric patches will be attached and/or embedded into the leaf spring of a vehicle suspension, Figure 1. When the spring is strained due to road vibrations, it strains the attached piezoelectric patch which produces an electric charge separation at the crystal lattice. The resultant electric potential across the piezoelectric patch can be transformed into useful power by designing the proper electrical circuitry. Under optimal operating conditions, piezoelectric materials can produce up to 0.2 Watts per sq-cm. In addition to acting as an additional power source, this approach provides a passive damping technique to reduce (or adapt) vehicle vibrations.

The second is Magnetostrictive-based Energy Generation: The properties of mangnetostrictive materials can be applied to generate electricity for in-vehicle power budgets. The proposed generator utilizes this smart material to directly transform mechanical strain into a magnetic field, Figure 2. In specific, when magnetostrictive materials are subjected to time- varying strain, they produce a time varying magnetic field which can be transformed into electrical energy as per Faraday’s law. In optimal operation, a 50 mm long magnetostrictive rod with a diameter of 12 mm can produce up to 100 Watts of power when strained by as much as 0.5 mm. This innovative concept may supplement traditional alternators/generators and reduce the cost and maintenance complexities of power generation. Another advantage is that the generator efficiency can be maximized at low rotational speeds. Therefore, a magnetostrictive generator can be retrofitted on the engine crankshaft to act as a substitute generator which boosts the power efficiency especially at low engine speeds. Further, the generator can be produced at extremely small sizes with very high efficiency and can operate at elevated temperatures. As such, a magnetostrictive generator can act as a turbine which can be installed in the air intake manifold or in the exhaust for additional energy recovery.