Water emissions from fuel cell-powered construction equipment : Quantifying liquid water and water vapor emissions for sustainable construction equipment

Abstract: The construction sector is responsible for 20% of Greenhouse Gas (GHG) emissions, of whichdiesel-powered construction equipment are large contributors. Currently there are many ongoing Fuel Cell (FC) powered construction equipment projects as it is seen as an attractiveoption to power the futures zero-emission heavy-duty machines. Although an attractivealternative, hydrogen FC has drawbacks such as releasing liquid water and water vapor viathe exhaust as a byproduct which in their working environment can cause a suite of issues. Agap in the literature on the water exhausted is present and therefore this degree project seeksto investigate the amount, and ratio, of liquid water and water vapor released from threetypical construction equipment drive cycles which would allow further investigation onappropriate management. The method used for this degree project was to modify a pre-mademodel in Simulink built with Simscape blocks. The model was modified to represent a FCsystem used in a test-rig by implementing experimental and measured data for design andoperating parameters. Different pressures, temperatures, and cathode inlet RelativeHumidity (RH) were investigated to find their effect on the performance and water in theexhaust. A sensitivity analysis of different unknown parameters was also conducted tounderstand their influence on the results. For the reference case, the results showed that foran articulated hauler, the water in the exhaust was 26% liquid which translates to 8.6 kg for a1-hour drive cycle. The crawler excavator and wheel loader, both had 30-minute drive cyclesand had 1.1 kg liquid water with a liquid water ratio of 7% and 0.7 kg liquid water with aliquid water ratio of 5% in the exhaust respectively. For a full 8-hour workday with twoparallel FCs connected, the articulated hauler liquid water amount is 137.6 kg, the crawlerexcavator 35.2 kg, and the wheel loader 22.4 kg. Overall, it was found the liquid water ratiocould be changed to a large extent with different operating parameters, where thetemperature had the greatest influence. The system and stack efficiencies did not changeconsiderably with different operating parameters, meaning that the total water in the exhaustremained similar for the different respective drive cycles.