The energy footprint of automotive electronic sensors
Introduction
Information and Communication Technology (ICT) development has spurred a growth in a sector-wide connected economy, with the creation of a tremendous value through the technology-enabled links between people, machines, and organizations. There are more than 31 billion global connected devices in 2018, of which 928 million devices are in automotive and transportation, with an anticipated growth of 21.4% Compound Annual Growth Rate (CAGR) during the 2013–2030 period [1]. It is projected that ICT can enable a 20% reduction of global CO2e emissions by 2030, holding emissions at 2015 levels through improved efficiencies, lower use of resources, and behavior changes [2]. Sensors/actuators are the key ICT electronic components for the initial stage of data collection and data exchange to the internet through other major electronic components of an Internet-of-Things (IoT) electronic device such as input/output module and controller in a connected economy [3]. Worldwide trends toward a more connected economy (such as connected or automated vehicles) are projected to increase energy consumption from the manufacturing and operation of connected IoT devices. Conversely, the growing availability of established and new services on single platforms or devices in addition to the availability of more efficient electronic devices may dampen this increasing energy consumption trend. A 2016 Swedish study on the energy and carbon footprint for the ICT sector (defined as all but ICT electronic devices used in the entertainment & media sector) indicates both footprints had peaked around 2010 and then started to decrease, despite growing number of usage (data traffic) [4].
A sensor is an electronic device that converts a physical or chemical stimulus into an electrical signal. That electrical signal is processed by an integrated circuit or microprocessor, transforming it into usable information for another system, such as an electronic control unit (ECU) and from there, an actuator, which can act and perform a function (e.g., turn on an alarm or open a window). The total global sensor market was $102 billion USD in 2015, and is expected to almost double in 6 years [4]. By end-use, consumer electronics is the top market, followed by the automotive industry. The automotive sensor market represents about one-quarter of the global sensor market [4] [5]. Within this, engine and drivetrain sensors dominates the market but safety and security related sensors have the highest growth [6]. Bosch and Denso were the main actors in the 2013 market with more than 25% market share [6]. Growth in 2015 was led by the IoT, though industry automation will be the top driver by 2022 [7].
Based on market projections, the global automotive sensors market is expected to register a CAGR close to 8% during the forecast period, 2018 to 2023, with total unit sales reaching 11.7 billion by 2023 [8]. The increasing demand for safety and security in the automobiles is the main factor that is playing a vital role for the growth of this market. The two big current trends for vehicles are electrification and automation; there is rapid integration of high value sensing modules like radio detection and ranging (RADAR), imaging, and light detection and ranging (LiDAR) in automotive systems. The adoption of electric vehicles will greatly change the amount and the sensor types, with increased emphasis on position, speed, temperature and pressure within the car, in the long term. Increasing demands for more vehicle infotainment (entertainment and informative features such as video players and GPS) and safety features (e.g., backup cameras and sensors) have also resulted in an increase in vehicle electronics (both sensors and ECUs). These new components account for about 30%–35% of the total cost of a vehicle, and are expected to reach 50% by 2030 [9,10]. The manufacturing of the microcontrollers (ECUs) for these new electronics will increase the total energy of vehicle manufacturing; however, electronics are more than just the microcontrollers. Electronics wiring has added 45–65 pounds to vehicles [11], which likely have significant manufacturing and use phase energy contribution. Overall, the number of sensors in vehicles is increasing each year, with more in higher class vehicles (a premium vehicle has more sensors than an economy class vehicle) [12]. Fig. 1 shows the increase in both sensors and ECUs in vehicles over time and over vehicle class: Economy (E); Premium or Luxury (P); and Standard (S). This paper focuses on automotive sensors, but the analysis also includes the energy impact of the ECUs and wiring required for a full sensor system.
Section snippets
Automotive sensors
Automobiles utilize many sensors for a variety of applications, though one sensor can serve multiple electronic systems. They are often used for monitoring various systems, such as the engine or tires, so the system's computer can adjust parameters (e.g., the fuel-to-air ratio) or inform the driver of problems. Pressure and temperature sensors are the most common within a vehicle and have the most diversity. For example, there are four tire pressure sensors in a vehicle, to diagnose tire
Ultrasonic backup/reversing systems – A representative automotive sensor
The ultrasonic backup/reversing system allows the driver to hear or visualize how near an object is to the rear of their vehicle. It works using high frequency sound waves for echolocation, allowing them to respond to fully transparent objects, such as glass, and respond to objects in the dark. Fig. 3 illustrates, step-by-step, how an ultrasonic backup/reversing system works. The system should respond with high accuracy when the objects are closer to the vehicle (0–2.5 m) [21], and not respond
Energy footprint of automotive sensor
As discussed, the potential increase in automotive sensor incorporation, specifically in ADAS systems, establishes the need to understand the energy impacts of the inclusion of these sensors, especially with respect to the manufacture and use of these systems. While not a complete life cycle assessment of ADAS sensors, this work discusses how the energetic impact of these sensors could be considered in future life cycle analyses.
The manufacturing and use energy footprint of automotive sensors
Manufacturing
The materials and manufacturing of the ultrasonic backup/reversing system includes the wiring (i.e., four 4.5″ sensor wires, a 12′ power wire, a 66′ trigger wire, and a 14″ display wire) and connectors, four ultrasonic sensors with four rubber grommets, the main module and the display module [21] as shown in Table 2. The embodied energy in this table accounts for the energy put in the final products, from the energy required to extract the raw materials to the energy purchased to manufacture
Use phase
For this analysis, the use phase was separated in three phases: electricity consumption, mass-induced gasoline consumption, and sensor replacement caused by vehicle use rear-end crashes. Electricity is provided to the sensor system using gasoline via the alternator and the battery. The mass-induced gasoline consumption is the additional fuel needed to compensate for the fuel efficiency reduction caused by additional mass of the system. Finally, the purpose of the system is to avoid rear-end
Energy use summary
The total manufacturing and use lifetime energy contribution is 991 MJ per vehicle lifetime of a sensor system consisting of four sensors (Fig. 6). The largest contributors to energy use are the mass-induced gasoline consumption (417 MJ), the total wiring (189 MJ) and the two ECUs (115 MJ each). Gasoline for electricity use (1.0 MJ), lifetime sensor replacement (13.7 MJ) and avoiding the replacement of a rear bumper (1.0 MJ) were significantly lower energy impacts.
Future energy use implications
As shown in Fig. 2, types of proximity sensors per vehicle are expected to increase from four to nine by 2040, with the number of sensors increasing from 17 in 2015 to 32 [20]. Assuming “# of Types of Proximity Sensor” is analogous to the number of sensor systems, and that the ultrasonic backup sensor system is a representative ADAS system, just the manufacturing and use energy of ADAS systems contribute 4.0 GJ to the lifetime energy use of a 2015 vehicle (four systems of 991 MJ each). This
Conclusion
The ultrasonic backup/reversing system is a proximity sensing technology that enables the driver to be more aware of objects and people behind the vehicle. Back-over crashes kill approximately 228 people per year and injure over 17,000. Unfortunately, ultrasonic sensors are not likely to prevent more than 3 fatalities and approximately 200 injuries over the vehicle lifetime [37]. The sensors are both unlikely to “see” people behind the vehicle and even if they do alert the driver to an
Declaration of Competing Interest
None.
Acknowledgments
We gratefully acknowledge the analysis contribution discussed here made by Pablo Cassorla, while working as an intern at Oak Ridge National Laboratory. This research was sponsored by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office.
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