“Energy efficiency is one of the most important design considerations when developing building automation products. Some of the new wireless smart sensors can work for more than five years on a single coin cell battery, and some even last 10 years or more. In this white paper, I will discuss various advances in energy efficiency in building automation.
Energy efficiency is one of the most important design considerations when developing building automation products. Some of the new wireless smart sensors can work for more than five years on a single coin cell battery, and some even last 10 years or more. In this white paper, I will discuss various advances in energy efficiency in building automation. Let’s start by taking a look at how nanowatt-class integrated circuits (ICs) can enhance functionality and reduce power consumption, and how recent advancements have enabled low power consumption and long operating life. The average current consumption of a nanowatt device can be measured in nanoamps (nA) (one billionth of an amp). A standard CR2032 coin cell battery used in long-range wireless smart building sensors can provide approximately 2,100nA over 10 years.
For nanowatt-class modules introduced to the mass market in the past two years, the current required is less than half that of the previous generation. Because designers need to design with less space for batteries and power supplies, they are able to build smaller products. In addition, the convenience and safety of retrofitting existing residential, commercial and industrial areas with sensors and smart devices has also increased. Because these devices can operate for years on commercial-grade batteries, there is no need to use wires or to program routine maintenance for battery replacement. With the rapid spread of IoT-related applications in building automation, attention has been paid to the huge potential of using embedded sensors to improve safety and efficiency: these sensors can not only detect individual component failures in very large systems, but also monitor through mmWave radar. Human health and comfort.
Energy Efficiency in Building Automation: Considerations, Importance and Future Trends
When it comes to energy efficiency, design engineers need to consider many factors. They must balance performance between functionality, battery life expectancy, and the average current draw of each device on the board, as well as create an accurate steady-state consumption model for the design. In order to reduce power consumption as much as possible, many engineers implement some functions very cleverly in the design, which improves the overall efficiency.
It is not only battery-powered devices that need to be considered for energy efficiency; almost all line-powered systems do. For example, in the heating, ventilation and air conditioning (HVAC) industry, the US Department of Energy (DOE) has instituted stricter regulations to minimize efficiency ratings (called “seasonal energy efficiency ratios”). These regulations in turn have led to the rapid replacement of permanently split capacitor motors by electronically commutated motors, which are now standard on most manufacturers’ next-generation HVAC equipment. Figure 1 compares the two motors described above. DOE believes that while consumers bear the initial cost of the more expensive motors described above, electronically commutated motors actually deliver significant energy efficiency improvements, so the technology pays off quickly – saving more than $9 billion in American households by 2030 electricity costs. For high-efficiency electronically commutated motor designs, it is recommended to first refer to the TI Electronically Commutated Motor Reference Design for HVAC Fans with Low-Cost BOM. The following sections detail the current battery-powered applications in building automation – building safety, ultra-low-power product design, and energy efficiency. There are many examples of this trend. As shown in Figure 2 on the following page, the security and video surveillance market is expected to grow by around 5% from 2013 to 2023 (Source – Omdia, “Industrial semiconductor Market Tracker”, 2020*). This growth will inevitably drive stakeholders to continuously optimize the efficiency of security and video surveillance equipment.
In larger spaces and older buildings, replacing intermittent line power with battery-powered sensors can be significantly more cost-effective. Battery life has been extended for energy efficiency, so remote sensors in a building or residence can deliver real-time environmental data and sensor conditions for longer than ever before without using line power. Energy-Efficient Devices Can Solve Engineering Challenges In building security applications, Hall-effect sensors can detect changes in magnetic fields using low-cost magnets placed on doors and windows. As with the DRV5055 angle evaluation module, two DRV5055 sensors can be used in combination to achieve 2D position detection.With this advanced induction method, as well as the calibration method used and the number of calibration points, it is possible to
Figure 4 on the next page shows another low-power, energy-efficient application that uses a 320nA TLV8802 op amp as the signal chain for a passive infrared sensor. The TLV8802 is ideal for cost-sensitive systems using battery-operated devices. PIR applications require an amplified and filtered signal at the output of the PIR sensor so that the amplitude of the signal entering the subsequent stages of the signal chain is large enough to provide useful information. When a PIR sensor detects the movement of a distant object, the typical signal level at its output is in the microvolt range, so amplification is required. Filtering is required to limit the noise bandwidth of the system before the noise reaches the input of the window comparator. The filtering function also sets the minimum and maximum speed limits for the system to detect movement.
Another way to optimize a design for energy efficiency is to use a combination of nanowatt timers and load switches to power down more power-hungry devices and even microcontrollers (MCUs) and put them into a deeper sleep state. Figure 5 is a schematic of a simple low-power wireless environmental sensor suitable for residential and commercial environments. In Figure 5, the TPL5111 is used as a periodic wake-up or enable signal for the TPS22860, which powers the HDC2080 when the TPS22860 is enabled. This circuit also has a DONE pin that connects to the SimpleLink™ MCU’s general-purpose input/output pins to power down the HDC2080 after processing is complete. When the nanowatt timer turns off the load switch, it cuts off the power from the HDC2080, which greatly reduces power consumption. A wide time range can be set for the TPL5111, which can save more power when the polling frequency is set to a high latency value. Energy Harvesting for Building Automation Many of the current ultra-low power innovations are based on coin cell battery designs that have been around for decades, but these components consume electrical energy converted from light (photovoltaic), mobile or radio frequency energy. Energy harvesting can provide additional power to the device, thereby greatly improving energy efficiency. When combined with ultra-low-power devices and energy-efficient designs, the useful life of remote building sensors can be extended by years. Supercapacitors, when used in conjunction with or in place of coin cells in low-power devices, can store harvested energy for use by the device. Unlike disposable batteries, supercapacitors charge quickly.
Energy Harvesting Applications: Door Handles
Extra energy is easily collected by turning the door handle for use by the smart lock. When used in conjunction with a motor, the motor shaft can be integrated with a reduction gear to convert the slow rotation of the door handle into a higher-speed rotation of the motor, allowing the motor to generate electricity, which is then rectified and conditioned for storage within a supercapacitor. Figure 6 shows a possible setup to test this energy harvesting method by using a grip dynamometer and coupler on the door handle.
Figure 7 shows the complete power path for converting the rotational motion of the door handle into stored energy. This power path has two load switches to reduce battery load when the energy on the supercapacitor is high enough to power the system or provide energy for battery charging. The DRV8847 dual H-bridge motor driver can harvest energy from the generator. Figure 8 shows the output power of this power architecture.
There are many other TI products and designs that address the industrial needs of energy harvesting, such as the Wireless Switching Power Supply Energy Harvesting Reference Design, which utilizes a zero-frequency energy harvesting switch to generate energy at the push of a button. Another good example is the Energy Harvesting Ambient Light and Environmental Sensor Node Reference Design for Sub-1GHz Networks, which uses two integrated solar cells to provide additional power to the system by harvesting photovoltaic energy. Figure 9 shows the output of this energy harvesting door handle along with the active rectification of the motor output.
An example of an energy efficient design
A central component of smart home design is the smart lock, which wirelessly receives commands from authorized users, monitors hallways, and operates door locks without human intervention. But if battery life and maintenance often interfere with the normal operation of the smart lock, the smart lock will not be recognized by the mainstream standard lock/key mechanism. Energy-efficient design and energy harvesting help extend the life of Electronic smart locks by years. Consider an advanced smart lock that ensures the deadbolt is in the door frame and the door is fully closed. When a user unlocks the latch turnstile from the inside, a small amount of energy is generated, which can be harvested and used to verify the latch position when the door is locked remotely. Obviously, this is only one of the proposed methods, there can be many others. Figure 10 on the next page shows a block diagram of this particular approach.
There is a simple insert on the side of the door frame that can be installed on the back of the bolt plate. Inside these contacts there is a special resistance value that provides a voltage drop across the contacts. An op amp can be used to compare this voltage, or an ultra-low power analog-to-digital converter can be used to measure the output voltage to further improve accuracy or prevent tampering. After the MCU verifies the output value, it cuts power to the load through the load switch to minimize power consumption (≤2nA in shutdown mode). Due to the passive nature of the peripherals, this design is highly efficient and can provide additional intrusion and tamper-proof security features for smart locks at very low additional cost. Figure 11 outlines the latch position sensing application in more detail.
For a new technology to replace a mature but low-tech incumbent technology, it usually needs to have clear advantages and not impose any serious burden. The implementation of ultra-low power consumption not only improves convenience, but also provides advanced technology that requires little maintenance to successfully solve these challenges. With years of reliable data insights and computing power you can rely on, ultra-low-power technologies are redefining expectations for where, how, and how long smart devices can be deployed. The ripple effect of these innovations will continue long after the first-generation batteries are finally obsolete.