Model-Based Design of a Pseudo-Cogenerative Heating System for e-Boat Battery Cold Start

Abstract

Full-electric boats are an expression of recent advancements in the area of vessel electrification. The installed batteries can suffer from poor cold-start performance, especially in the frigid season and at higher latitudes, leading to driving power limitations immediately after startup. At state, the leading solution is to adopt a dedicated heater placed on the common cooling/heating circuit; this implies poor volume, weight, and cost figures, given the very limited duty cycle of such a part. The Heater-in-Converter (HiC) technology allows removing this specialized component, exploiting the power electronics converters already available on board: HiC modulates their efficiency to produce valuable heat (pseudo-cogeneration). In this work, we use the model-based approach to design this system, which requires heating power minimization to fulfill power electronics limitations, while guaranteeing the user-expected startup time to full power. A multistage model is used to get the yearly vessel temperature distribution from latitude information and some additional data. Then, a lumped parameter for the cooling/heating circuit is used to determine the minimum required power as a function of the properties of the thermal interface material used for the battery coupling. The design is validated on a 1:5 test bench (battery power and energy), which demonstrates how the technology can be to scaled up to also fit different boats and battery sizes.