Advances in Automotive Climate Control via Infrared Sensor Technology

    As oil resources become depleted, gasoline prices rise, and pressure for lower carbon emissions grows, the task of controlling a vehicle's power budget becomes more important to automotive design engineering teams. Climate control systems draw a considerable amount of current from a vehicle's battery, so their use will affect the vehicle's overall fuel economy. Recent research conducted in Europe examined the power consumption of various climate control systems and found that in some cases it can account for up to 15% of total fuel consumption.

    Typical auto industry approvals at the moment do not require tests that demonstrate how the working of climate control affects vehicle operation, nor are automakers obliged to reveal any figures about the feature's impact on overall fuel consumption. But all this is about to change, as industry bodies in major Western economies have begun implementing testing procedures that will take into account the increased energy consumption of climate control systems.

Car climate control systems

    The vehicle climate control mechanisms currently found in cars can be divided into the following types:

    1. Manual: The vehicle occupants set the temperature and the intensity of the airflow through the blower. This requires the occupants to make constant adjustments as the situation changes.

    2. Semi-automatic: The temperature inside the car can be maintained at the level set by the occupants, but the intensity of the air flow must still be adjusted manually.

    3. Fully automatic: Various sensors are installed in the car to always maintain the best cabin climate conditions for the comfort of the passengers. All of this is based on the temperature pre-defined by the passengers, and the system automatically adjusts the air flow, air volume and air temperature of the blower.

    Industry studies have found that when used correctly, fully automatic climate control systems consume significantly less fuel than less advanced manual systems. This means that if the automatic system is operated manually, the fuel economy improvement is not possible.

Figure 1: Effect of air conditioning on fuel consumption when the car is idling (%) (Source: ADAC).

    The above data shows that the vehicle climate control system consumes the highest proportion of fuel when the vehicle is driving in a congested urban environment. If the vehicle is moving slowly, the air conditioning consumes more electricity than any other power-consuming accessory (potentially up to 70% of total electricity consumption).

    Vehicles that use some form of fully automatic climate control have proven to be more fuel efficient than traditional manual or semi-automatic systems. The sensor function installed in many cars uses a simple thermistor to determine the air temperature inside the vehicle and thus regulate the interior climate of the vehicle. However, this strategy often produces inaccurate estimates of passenger comfort because the heat generated by solar radiation shining into the vehicle is not taken into account.

    Using infrared (IR) sensing mechanisms instead of passive semiconductor technologies in these systems can improve system fuel efficiency. IR sensing mechanisms can react faster than previous sensor technologies and can take into account the temperature effects of sunlight felt by occupants and make corresponding adjustments.

    In the future, multi-zone climate control mechanisms will become more common. These will be able to handle the uneven distribution of sunlight throughout the vehicle, making it possible for each occupant to achieve the optimal conditions for the setting. In luxury and mid-range vehicles, the implementation of this solution will require multi-element infrared sensor arrays to generate accurate temperature distribution within the cabin in real time. With these sensor arrays, changing heat loads can be more effectively handled, thereby improving cabin temperature stability and occupant comfort, while reducing energy consumption, keeping system bill of materials costs under control, and helping to speed up the implementation process.

Figure 2: The MLX90620 has a 16x4 pixel FIR array with built-in EEPROM to store calibration data and an I2C digital interface.

    Using a multi-element far infrared (FIR) thermopile (thermopile) sensor array, operating over a temperature range of -20°C to 300°C, a real-time thermal map of a given target area can be generated, eliminating the need to scan the area with a single point sensor or employ expensive microbolometer equipment. This array measures the infrared energy emitted from the driver/passenger to compensate for their perceived temperature level without being affected by solar heating conditions, which could otherwise give very erroneous results.

Issues Affecting Climate Control Efficiency in Electric Vehicles

    While climate control system efficiency must be considered in all new models, more efficient air conditioning is particularly important in the hybrid/electric vehicle sector. For example, electric vehicles have a greater difficulty in providing effective cabin temperature control than internal combustion engine vehicles. The reason is that electric vehicles cannot use waste heat from the engine cooling system to heat the cabin in winter. In addition, any battery drain in an electric vehicle will sensitively shorten its driving range, lead to more frequent charging cycles, and affect its performance.

    汽车制造商需要最大限度地提高燃油效率，这种压力在不断增大。他们的设计工程师必须面对困难的挑战，以减少车舱内能耗，同时仍然能够提供客户所期望的舒适程度。从汽车的燃油效率角度看，气候控制系统有着深刻的影响，汽车厂家需要立即采取行动以降低其燃油消耗。先进的红外技术部署可实现把下一代多温区车舱内热成像解决方案推向市场的承诺，能够保持司机/乘客的舒适性，同时显著降低能耗水平，提高燃油经济性。