Combined Vehicle-to-Building (V2B) Strategy and Solar Power to Reduce the Campus Carbon Footprint

National Taiwan University has committed to a carbon-neutral campus, and getting there means rethinking how its buildings draw and store energy. This completed project (2022–2023) was the E3 Center's contribution to Designing Carbon Neutral Infrastructures for Sustainable NTU Campus — an interdisciplinary program led by Prof. Christina W. Tsai that paired six civil-engineering sub-projects across water, materials, buildings, mobility, energy storage, and hydropower. As Sub-Project 5, and with Prof. I-Yun Lisa Hsieh as a co-investigator of the integrated program, the E3 Center tackled the electricity and mobility piece: can a building lean on its parked electric vehicles and its rooftop solar to cut both grid dependence and carbon?

The answer is a Smart Energy Management System (SEMS) built around a vehicle-to-building (V2B) strategy. Vehicles sit idle most of the day; as they electrify, their batteries can double as flexible storage — charging on excess solar and discharging back to the building when demand peaks. The project developed an energy-dispatch algorithm at one-hour granularity that dynamically gauges how many EVs are actually available, then coordinates them with rooftop solar PV and a stationary energy-storage system. Crucially, the economic analysis went beyond electricity bills to capture hidden costs — above all the battery wear that V2B cycling imposes on EVs — for a more honest account of what the strategy really costs.

Demonstrated on an NTU campus building, the results were substantial. Against a grid-only baseline, the SEMS cut the building's grid power demand by about 65% and its carbon emissions by about 64%. Comparing scenarios — grid-only, PV-only, PV+V2B, and PV+V2B with added storage — the PV+V2B configuration emerged as the best-balanced choice, delivering roughly 6% ownership-cost savings and a 59% reduction in CO₂-equivalent emissions once investment cost, energy savings, and environmental benefit were weighed together.

These findings became the seed of a continuing line of E3 Center research: scaling the V2B strategy from one building toward whole-campus energy management, folding in AI to handle the uncertainty in electricity use, vehicle behavior, and solar generation, and extending the same nearly-zero-energy-building ideas into later projects on smart battery-swapping and building-scale sector coupling.