![]() The infrared wave band quickly contacts objects in its path and warms them. When turned on, a radiant heater emits invisible infrared waves a relatively short distance in a narrow band. Radiant heating employs one of the three forms of heat transfer. The Toyota testing showed use of the radiant heater resulted in a 5.3% reduction in fuel consumption, and much improved driver comfort within two minutes of cabin entry. This effort may indicate the Prime, which also has seat and steering wheel heaters, is being used as a testbed for solving the EV cabin heat-vs.-range conundrum. In a presentation at the 2022 SAE WCX, Toyota detailed its test installation of an electric radiant heater in a Prius Prime, describing the system as a method for providing supplementary cabin heat quickly and with greater efficiency than other methods. This technology enables heat pump operation down to -10☌ (14☏). The Toyota Prius Prime PHEV’s A/C refrigeration system incorporates a liquid-gas separator and injection of refrigerant gas, a development adapted from static-mount commercial heat pumps. To date, most efforts to improve EV heating performance have focused on electric seat heaters, some electric steering wheel heaters and for the most part, heat pumps built into the HVAC refrigeration system.īut the heat pump performance is limited by the fact that refrigerant flow slows with low winter temperatures, so heat pumps must switch to less-efficient resistance or PTC (positive temperature coefficient) heaters when ambient temperatures drop below 0☌ (32☏). (Toyota)Īlthough air conditioning use in hot summer weather typically causes a modest loss of EV range, it’s the 30-40% drop of range in cold winter weather when the cabin heater is deployed that continues to challenge EVs’ ability to fully replace ICE-powered vehicles. ![]() ![]() (Toyota) Comfort levels at 10 minutes of operation. (Toyota) Comfort levels at five minutes of operation. Toyota engineering refers to the radiant heater as “radiative heater” in this and its other comfort level graphs. Comfort levels at two minutes after entry and vehicle operation. Now comes the hard part: Deliver those same ratings in real-world weather, in the kind of thermal extremes that challenge the performance of lithium-ion battery packs. Vehicle OEMs have been steadily increasing the range of their electric vehicles (EV) and plug-in hybrids (PHEV), but the ranges they claim publicly are in ideal thermal conditions. ![]() Paul Weissler Toyota’s first serial production EV, the 2023 BZ4X, uses the new radiant heat system co-developed with Denso. ![]()
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