System level heat pump model for investigations into thermal management of electric vehicles at low temperatures.

Abstract

One of the challenges concerning electric vehicles is their performance in cold climates. As the temperature drops below 10 • C battery capacity begins to reduce and heating demand starts to claim a larger proportion of total vehicle energy expenditure. Although efficient, electric vehicles waste heat through a few components, resulting in opportunity to harvest waste heat through a heat pump. With multiple options for harvesting heat and the option to heat the battery, a model and architecture has been developed to give flexibility in a wide range of thermal management scenarios. This paper explores the details of the model and presents two example cases of interest to demonstrate the model's applicability.

Optimisation of Control Input Allocation Maps for Electric Vehicle Heat Pump-based Cabin Heating Systems

“…Some safety features, such as limiting the compressor outlet pressure p 3 and the evaporator outlet pressure p 1 (see Figure 2), as well as the compressor pressure ratio p 3 /p 2 , cannot rely solely on the model accuracy, i.e., they need to be satisfied explicitly. For this purpose, the overall control strategy should be extended with secondary feedback controllers of measurable variables that need to be limited (see e.g., [31]). There may be additional practical extensions of the proposed, overall control strategy, such as switching the compressor off when the cabin air temperature tends to overshoot the target temperature, which may typically occur for the conditions of relatively high ambient temperature, i.e., low thermal loads.…”

Optimisation of Direct Battery Thermal Management for EVs Operating in Low-Temperature Climates

“…The models for the heat pump, battery, cabin, motor, and thermal storage will be explained in the remainder of this section. Full and further details of the model can be found in Reference [8,32]. Should the reader be further interested in the model, the libraries used are available from Claytex Ltd.…”

“…The heat pump is able to extract heat from multiple sources around the vehicle, as shown in Reference [8,32]. Parameters relating to the heat pump's operation can be found in Table 2.…”

“…When the material temperature drops to T melting + 1 the capacitance is increased from C p to C p + C l , then when the temperature falls beneath T melting the capacitance is restored to C p . This approach for modelling PCMs has been used in other similar research [8,32,43].…”

“…The first metric is energy consumption which incentivises the minimisation of HVAC usage. The second is depth of discharge (DOD) which correlates directly to remaining range and is separable from energy consumption due to the subtleties of the impacts of low temperature on battery performance [32]. For example, it is possible to spend extra energy on heating the battery at the start of the drive cycle, resulting in higher battery temperatures and a higher final SOC.…”