As demand for electric vehicles (EV) continues to rise, innovators are continually developing new technologies that have the potential to increase range and efficiency, as well as improved flexibility, including preheating vehicle components and other applications of thermal energy systems.
Thermal Energy Storage (TES) solutions are growing across many sectors and applications, including optimizing smart buildings (factories, offices, public buildings, university campuses, homes, and hospitals) by reducing the cost of energy and related carbon emissions.
Future mobility concepts include thermal energy storage technologies including sensible, solid media, metallic latent, and thermochemical, which, depending on the vehicle application, drives competitive value. The integration of thermal energy storage systems can repurpose waste heat then store and discharge thermal energy in times of demand.
The most successful approaches are based on Phase Change Materials (PCMs) that have high energy and power densities and yet are non-toxic, environmentally friendly, and safe.
Without the high-grade waste heat available from the engine of a conventional automobile, EVs require energy stored in the vehicle to heat the cabin for a quality interior climate experience. Low-grade heat rejected by the electric powertrain, traction battery, or any heat pump system normally wasted to the environment can be collected, stored, and used later; otherwise, this cabin heating energy is provided by the high voltage traction battery.
In very cold climates, the power required to heat the EV cabin can be as much as the power required for propulsion of the vehicle, impacting the driving range, which limits consumer acceptance of EVs and results in increased battery costs to achieve a minimum range while ensuring the comfort of the driver and passengers.
To minimize the range penalty associated with EV traditional cabin heating, climate control systems that leverage TES are increasingly being adopted for use in EVs and plug-in hybrid electric vehicles (PHEVs).
The system uses the stored latent heat of an advanced phase change material (PCM) to provide cabin heating. The PCM is melted while the EV is connected to the electric grid for charging of the electric battery, and the stored energy is subsequently transferred to the cabin during driving.
To minimize thermal losses when the EV is parked for extended periods, the PCM is encased in a high-performance insulation system and can warm a cold car up within minutes and keep the cabin at a pleasant temperature for most average commute times.
TES battery power used to generate cabin heating leads to a dramatic decrease in the driving range of EVs. Some studies have shown that the range of a BEV with an electric cabin heater can be reduced by 20-40%, depending on the drive cycle.
TES solutions are becoming essential, and innovative companies are developing reliable, cost-competitive, and more energy-efficient occupant heating systems that can help reduce traction battery load and increase the driving range while controlling the internal environment.
TES solutions also benefit our global environment, as they reduce carbon emissions, and in some cases, are far less toxic than lithium batteries while being far less expensive.
PCM is used to describe materials that use phase changes (for example, automated melting) to absorb or release a relatively large amount of latent heat at a roughly constant temperature. When the temperature becomes warmer than the freezing point, PCMs liquefy and absorb and store heat. When the temperature decreases, the material will solidify.
At the Frontier Conference on Industrial Innovation last month, we caught up with Andrew Bissell, founder, and CEO of Sunamp, a TES battery provider based in Scotland, which develops, manufactures, and sells compact, efficient advanced thermal storage technology to learn more about this emerging field.
“Our Heat and Cold Batteries help reduce emissions and improve air quality and address vehicle thermal management challenges such as engine and cabin warm up, catalytic converter temperature fluctuation, and battery thermal conditioning and HVAC systems,” Bissell said. “Thermal energy stored and re-used to keep engine components operating at peak efficiency means less emissions and cleaner air.”
Their automotive applications include engine & cabin warm-up, which reduces start-of-day engine idling with a fast warm up of engines and cabins, reducing emissions and saving time, with a simple integration into existing HVAC cooling circuits which store and release heat where it is needed, improving driver and passenger comfort.
“Vehicles waste heat, but they also need heat,” Bissell explained. “For TES solutions to work, they must be modular and scalable, with high output, and adaptable for different installations. “Fast engine warm up is especially popular in colder climates, while EV cabin heating and dehumidification using small heat batteries is beneficial in all climates.”
The company provides TES systems for public transportation as well, implementing Fast Cabin Warm Up for electric and hybrid buses. The form factors for each fit the size and scale of the vehicles, with an attractive and ruggedized enclosure.
“We have developed our own Phase Change Materials, which are non-toxic, stable, proven, and cost-effective,” Bissell said. “Even after over 30,000 cycles, we have seen no degradation.”
Based on data the company collects, the batteries increased mileage and reduced charging time while lowering CO2 by 10-100%, depending on the electricity source.
“Other benefits include reduction of noise pollution from traditional fossil-fueled truck and trailer refrigeration systems. Integrating low-temperature PCM TES reduces input energy but, more importantly, can maintain chilled storage area operational temperatures over typical duty cycles from the stored cold. Given how quiet the operation of the battery is, this allows night deliveries in cities where more governments are mandating the lowering of decibels,” Bissell said.
“The use of TES in plug-in electric hybrids is also welcomed by public transportation authorities as it eliminates the need for Idling for up to an hour to warm up a bus before leaving the depot, which increases local emissions and reduces fuel economy.
Recent 1D simulation work proved that we could capture waste heat from the exhaust gas stream of a P2 hybrid and use that heat to warm up the engine and extend the electric-only range in the engine-off mode in cold conditions. Using WTLC and a Paris real-world duty cycle, we achieved fuel consumption reduction up to 12.9% in WLTC and 29.5% in Paris cycle. Electric range extension was 18% in WLTC and 50=9% in Paris cycle. Future EURO 7 emission regulation has set the time to optimal 78ºc at 200 sec; we achieved 202-sec WLTC.”
Sunamp Phase Change Materials (PCMs) have been patented in the UK and China, with patents pending in other countries.
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