Studies Show How to Modify HVAC Systems for Improved EV Range

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【Summary】Current EV climate control systems use valuable battery power and reduce range. Recently, at the Society of Automotive Engineers (SAE) WCX conference, two studies presented innovative ways to address the problem.

Mia Bevacqua    May 27, 2018 8:10 AM PT
Studies Show How to Modify HVAC Systems for Improved EV Range

Most electric vehicles (EVs) use valuable battery power to operate climate control systems. The result is an impact on performance that causes range to drop by 50-60%. Two methods for addressing this issue were recently presented at the Society of Automotive Engineers (SAE) WCX conference. One involves increasing thermal storage and the other reducing load imposed by heating systems.  

Typically, EVs use either an electric PTC (Positive Temperature Coefficient) heater and/or a heater pump to warm the cabin. A PTC heater uses a resistive element to heat water or coolant. This design uses a lot of battery power to keep things temperate. Some vehicles take a different approach by using (or adding) a reverse air-conditioning style heat pump for warmth. 

Hanson Systems unveiled its take on EV cabin heating at the WCX conference. Working together with Kia and the Department of energy, the company has added a thermal storage system to the heating system of a 2015 Kia Soul EV.

From the factory, the Soul EV is already well-endowed with advanced heating equipment. Not only does it have a traditional PTC heater, but also a heat pump. The OEM pump already recovers some of the heat-related range loss. Unfortunately, it also adds complexity and increases refrigerant use.

To improve performance, Hanson added two coolant circuits and heat exchangers to the Soul's OEM heating system.  When the vehicle is plugged in, the heater is turned on and the system stores heat. During vehicle operation, the heater is turned off. In this state, the system harvests waste heat from the motor/electronics cooling circuit. 

The National Renewable Energy Laboratory (NREL) presented a different take on EV heating: thermal load reduction. Researchers hope the approach will increase EV drive range by around 20%. 

Early test subjects for the study were a pair of Hyundai Sonata PHEVs. One was left unmodified, and the other was fitted with an innovative thermal reduction package. The modified car contains an array of components designed to reduce climate control load. The lineup includes an electrically-heated windshield, solar reflective glass and solar reflective paint, heated surfaces around the driver, door glass demisters and climate-controlled seats. 

During testing in Fairbanks, the heated windshield cleared ice in just 6 min while using 0.1 kWh of electricity. By comparison, the unmodified Sonata took 19 minutes and 2.6 kWh. In addition, occupant comfort was reached in 15 minutes with the NREL system, whereas the OEM layout took 29 minutes. 

The vehicles were also tested at the Hyundai America Technical Center proving grounds in Mohave, CA. At this location, the modified Sonata's range increased 11.4% and A/C energy usage was cut by 23.7%. 

Sources: SAE and Identifix

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