Finding an efficient air conditioning solution for electric vehicle conversions is one of the greatest challenge facing individuals doing EV conversions today. Despite the fact that air conditioning is a necessary luxury in modern automobiles, few readily available solutions exist for electric vehicles.
Regular AC solutions are very inefficient, even for use in vehicles with internal combustion engines. The problem is more pronounced in electric vehicles because conventional AC solutions significantly reduce EVs driving range by drawing from the limited power storage that their batteries can hold. In such cases many electric vehicle owners opt to roll down the window and allow the rushing wind to do much of the cooling.
If having air conditioning is a must, then one of the following solutions can be considered for use in your electric car:
- Use a Peltier cooler - Peltier coolers use Peltier modules to super cool a contact surface across which air can be blown to cool the interior of the vehicle. The Peltier effect was named after Jean Peltier who observed that when a current was past between two dissimilar metals (type P and N), that one metal became very hot and the other very cold. Peltier modules are quite flexible, in that they can provide heating or cooling on any of the two surfaces by simply reversing the polarity of the current. The principle is use in some computer CPU cooling systems but can be adapted for use in automobiles. Some popular solution providers include CoolIT and Ferrotec that provide complete modular solutions that include temperature displays and controllers to ensure the efficient operation of the cooling systems. Peltier cooling systems may also be referred to as TECs or thermal electric coolers.
- Use a compressor with an integral motor - More recently some manufacturers have integrated motors into compact air conditioning units that are specifically designed for electric vehicles. Masterflux offers one such solution in their Sierra line of products (model 06-0982Y3). The Prius and some electric car conversions use similar solutions. These units utilizes a variable speed controller to maximize efficiency by ensuring that the unit operates in the sweet spot and is never running when a cooling load is not present. They are very compact and can be placed anywhere inside the vehicle.
- Use a regular AC compressor - Connecting the AC compressor directly to the drive motor ensures that the original AC system remains intact, with only an adapter needed to make the connection. Most applications, that use this method, will employ a dual shaft motor so the AC compressor can be integrated without complicating the connection of the drive motor to the rest of the drive train. However, the major drawback to using this method is that the air conditioning only works when the motor is running. In most electric vehicle setups, this means there will be no air conditioning when the car is not moving.
- Power the AC with an auxiliary motor - Another option that may be considered is to use a 12V auxiliary motor to run the compressor. This option allows for the use of the AC when the car is stationary but may add weight and complexity.
- Use an icebox cooler - A less sophisticated option is to use a 12V icebox cooler. This method provides cooling by blowing air over blocks of ice stored in a cooler. Of course this works so long as the ice stays frozen but it adds bulk to the interior of the car, not the mention the hassle of replacing the melted ice.