Energy Harvesting via Ballonet Altitude Control; Sustainable Implications for Electric Vehicles

Have you ever wondered why blimps are so rare? For capstone I worked under Mr. Lagor on “Ballonet Energy Harvesting” to explore ways to improve the energy efficiency of existing airship systems that control and change their altitude through the use of a ballonet system by creating an energy capture system. For my STS paper I focused on electric vehicles (EVs) and if they are more environmentally sustainable than traditional cars. I chose EVs instead of airships because airships are uncommon and not used in everyday life. Since I wanted to remain on the task of sustainable transportation I felt that EVs would be the most appropriate application.
Recently, the viability of airships for long-distance transportation of goods has been considered. Trucks dominate domestic shipping as they offer a balance between speed and cost. Internationally, the only viable alternative to planes is cargo ships. Airships have potential as they are faster than ships and emit less than airplanes. However, they are energy intensive, so reducing their net energy would make them more viable. To solve this, we experimented with mounted propellers and ways to improve energy efficiency of existing airship systems.
It was determined early on that attaching propellers to rotate as the airship changed altitude was unfeasible at our scale as they weigh too much. Hence, the design changed to more of a tethered airship. Unfortunately, the transportation application no longer applied as the airship remained in place. However, the team succeeded in creating a working model that used ballonets to change altitude. To achieve this, a stand was made with pulleys, fishing line and a PMDC motor as a generator. The best models were made with a foil outer balloon, a latex internal ballonet, pneumatic tubing, and valves to control flow. The motor generated electricity from the up-down motion of the fishing line to which the blimp was attached. All components worked separately, but struggled when assembled: the blimp was unable to overcome friction to spin the motor, the blimp was too heavy and needed counterweights, and the lab’s height limit meant the small vertical movements yielded little energy. The team concluded that airships are inadvisable alternatives since weight limits would force propellers to be made of materials so light that they would be flimsy. The tethered application was more energy efficient and with time could see reproducible results.
The goal of my paper was to determine if materials needed for EV batteries require mining more harmful to the environment than the benefit of the vehicle’s lack of emissions. In 2016, the transportation sector overtook the electric power industry as the primary source of greenhouse gas (GHG) emissions in the United States, with 59% emissions from passenger light-duty vehicles (Bleviss, 2021). In researching EV sustainability, I looked for studies with full life cycle assessments–which include manufacturing–since large amounts of emissions are produced during mining. Furthermore, I considered the type of energy used by the battery electric vehicles (BEVs) because if it produced lots of GHGs–like fossil fuels–then the vehicle is not emissionless during the driving portion of its life (Ma et al., 2012). Lastly, I focused on the acquisition of raw materials–metals, rare earth elements and lithium.
At this time, research suggests that the energy sector is not built to withstand the strain caused by BEVs and plug-in hybrid EVs (PHEVs) without increasing GHG emissions. Therefore, hybrid EVs are more sustainable than BEVs, PHEVs, and internal combustion vehicles (ICVs) as they do not use the grid and have less tailpipe emissions. In the future, if governments steadily ramp up clean energy and EV infrastructure in a material conscious manner, it is not unreasonable for BEVs to see less full life emissions than ICVs. The next step must be the prioritization of environmentally efficient raw material extraction and added mining safeguards so future infrastructure can have a net positive effect on emissions.

School of Engineering and Applied Science

Bachelor of Science in Mechanical Engineering

Technical Advisor: Frank Lagor, Michael Momot

STS Advisor: Pedro A. P. Francisco

Technical Team Members: Clarisse Forro, Troy S. Meink, Ashlin Schultz, Robert Stambaugh, Will Stevens, Richard Yau, Yining Xu