Claytex has taken a historic approach to working with a major UK-based OEM to address some complex system architecture and controller design issues around EV thermal management.
Optimising the thermal management of an EV is a complex multi-physics problem. Particularly in cold climates during a cold start, occupants of EVs do not enjoy the cabin warmth that is generated by the heat loss from internal combustion engines. In EVs the main energy source for heating the cabin and the battery is the electrical energy stored in the battery itself, and using this energy for tasks other than vehicle propulsion reduces the vehicle’s range. When some of the heat lost from other powertrain components is efficiently redirected to the areas that require warming up (such as the cabin), vehicle range is increased.
Heat pumps are widely used for the transfer of thermal energy around a vehicle’s subsystems, and they have fairly low electrical power consumption levels compared to the amount of energy moved. Furthermore, the heat pump can effectively ‘chill’ components that are less sensitive to very low operating temperatures, such as the electric motors, so that the thermal energy extracted can be used to warm up the cabin and batteries. Once the vehicle systems reach their working temperatures, surplus heat loss from the various vehicle systems would usually be dissipated to the surrounding environment. If this energy is stored within thermal batteries, including phase-change material batteries for reuse on cold starts, further increases in vehicle range are yielded.
Maximising the recirculation of cabin air helps avoid the loss of heated or cooled air to the atmosphere and therefore reduces the need to re-heat or cool the fresh air entering the cabin. Recirculation thus creates a large benefit in terms of minimising the power consumption of the HVAC (heating, ventilation and air conditioning) system, though it has drawbacks in terms of maintaining good and safe cabin air quality (including CO2) and moisture levels. Another solution is advanced cabin glazing technologies, which can significantly influence HVAC power consumption.
The optimal thermal management solution requires that thermal energy is moved between the vehicle systems whilst keeping in consideration their temperature-dependent operating efficiencies (for example, chilling a component too much could increase lubrication losses).
By building the system models and integrating them with one another, the physical interactions between them can be explored, as can the effect of any additional mass on the vehicle’s range and performance.
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