  In this paper, we present a novel approach to perform highly efficient
numerical simulations of the heating, ventilation, and air-conditioning (HVAC)
system of an electric city bus. The models for this simulation are based on the
assumption of a steady-state operation. We show two approaches to obtain the
minimum energy requirement for a certain thermal comfort criterion under
specific ambient conditions. Due to the computationally efficient approach
developed, we can evaluate the model on a large dataset of 7500 scenarios in
various ambient conditions to estimate the year-round performance of the system
subject to different comfort requirements. Compared to a heating strategy based
on positive temperature coefficient (PTC) elements, we can thus show that a
heat pump (HP) can reduce the annual mean power consumption by up to 60%.
Ceiling-mounted radiant heating elements complementing a PTC heating system can
reduce the annual mean power consumption by up to 10%, while they cannot
improve the energy efficiency when used in conjunction with a HP. Finally, a
broad sensitivity study reveals the fact that improving the HP's heating-mode
coefficient of performance (COP) manifests the largest leverage in terms of
mean annual power consumption. Moreover, the annual energy expenditure for
cooling are around eight times smaller than those for heating. The case study
considered thus reveals that the advantages of improving the COP of the cooling
mode are significantly lower.
