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KNX solutions to improve energy efficiency in smart buildings

Technology Cover
Post Date: 2023-09-07, STMicroelectronics

With the increasingly serious problem of energy shortage, how to effectively use energy, improve energy utilization in a more intelligent way, and save energy will be one of the key elements in the application of smart buildings. KNX is an open standard for commercial and residential building automation, and this article will introduce you to the development of KNX standards and applications, as well as related solutions that support KNX technology.


Mature open standards for automation in commercial and residential buildings

KNX is an open standard for commercial and residential building automation. KNX equipment can be used to manage lighting, blinds and curtains, heating, ventilation and air conditioning (HVAC), security systems, energy management, audio and video, white goods, displays, remote control, etc., which will enhance the integrity and convenience of smart building applications and improve energy efficiency.

The KNX standard has been around for decades and is a mature technology. KNX evolved from three earlier standards, including the European Home System Protocol (EHS), BatiBUS, and the European Installation Bus (EIB or Instabus). It can use twisted pair (tree, line, or star topology), power lines, radio frequency (RF), or IP links. On this network, devices form distributed applications and interact as closely as possible through an interworking model with standardized data point types and objects, modeling logical device channels, a protocol that has been used to improve energy efficiency in homes and buildings.

One of the broad applications of KNX is room automation, where a central control component can not only perform operational functions such as lighting and shading, but can also be combined with available valves installed on heating or cooling components to achieve individual room control, for example, the KNX system can shut down the HVAC by sending a notification when a window is opened to avoid wasting energy.

KNX also allows the connection of various energy meters, and people can find excessive energy consumption sources by closely monitoring the data, and control the energy early to avoid waste. In fact, some KNX products even allow for sub-meter metering at the circuit level to get a more accurate picture of energy consumption.

At the same time, product manufacturers that support the KNX standard offer battery storage devices, whose usage status can be monitored by KNX, as well as manufacturers that use KNX to control the connection between the home and the charging station, so KNX solutions will be a key element for manufacturers of solar inverters, energy storage, and battery management systems (BMS).

The KNX market is growing quite fast and the main application categories include control and connectivity, lighting, energy management, home entertainment, smart appliances, security and other fields. According to statistics, it is expected that by the end of 2025, China's smart home market will be close to 37 billion US dollars, and the global KNX product market will be around 50 billion US dollars by 2030, with a compound annual growth rate (CAGR) of about 15.9%.


A wide range of KNX products increase energy efficiency

Knx-related products on the market are already quite diverse, such as energy meters (electricity, gas, water or heat meters, etc.) that support KNX can make you aware of your energy consumption to understand how to reduce energy costs and improve the energy efficiency of machines and electrical assets, so that you can run smarter buildings in a more energy efficient and economical way. These KNX devices provide long-term data records for further processing of energy data, which can be read out using a KNX-IP Router and a standard web browser to gain insight into the status of energy consumption data and enable remote diagnostics.

On the other hand, the KNX gateway for solar panel inverters provides a simple solution to transfer all relevant data from the inverter to KNX. It allows integrators to utilize fully integrated solar panel inverters for energy management, and data can be used to optimize energy consumption, monitor, trend, or trigger specific actions in the KNX system.

In addition, KNX can also be applied to battery storage units, by storing the energy generated by the photovoltaic system into the battery storage unit, it can meet about 75% of the annual energy demand with self-generated clean energy, and because this energy is generated on the roof of the house, rather than from external energy suppliers, it can manage energy consumption more independently. A more complete grasp of energy utilization.

At present, electric vehicles have become the development trend of the automobile market. KNX equipment can manage the charging pile in the home, and can also grasp the energy consumption of electric vehicles more accurately when electric vehicles are charged in the charging station outside.

KNX has designed various functional blocks based on the EN50491-12-2 standard to exchange data between the customer energy manager in the building and the energy consumer/producer in order to better understand the state of energy consumption and further processing to avoid energy waste. The use of KNX has a considerable impact on energy consumption, and due to the scale of commercial and public buildings, the return on investment for large buildings is of course faster than for residential buildings. However, the higher the cost of energy, the greater the return on investment when it comes to home applications.

In contrast to conventional smart building system installation, each function needs to be implemented through one or more cables, each device is only used for one function, and if the function needs to be changed, the physical installation must be changed. Compared with the KNX installation, all information needs only one cable (bus) to be transmitted, the function depends on the programming method, and can change the function without changing the installation, a single device can be used multiple, in a network can have more than 65,000 devices with address allocation, with more application advantages.


Miniature KNX twisted-pair transceiver with regulator

STKNX, introduced by ST, is a transceiver for KNX TP (Twisted Pair) communication. The device is in a small package with few external components, making the KNX node design very compact. The device has a simple microcontroller interface that easily replaces the physical layer implemented based on discrete components.

The STKNX device features two integrated regulators for external applications, including an optional 3.3V /5 V-20 mA linear regulator and an adjustable 1 V to 12 V-150 mA high efficiency DC/DC buck type switching converter. The device integrates a KNX bus power extractor that supports bus currents up to 30 mA to power external devices and meet the power needs of STKNX transceivers, while limiting the bus current conversion rate according to KNX specifications. STKNX ensures safe coupling to the bus and provides bus monitoring warnings when the bus power is too time-consuming.

The STKNX device comes in an ultra-thin, small pin length 4x4mm VQFNPN24 package, is KNX-certified, supports KNX TP1-256 standard, can easily connect to microcontrollers (such as STM32), is an ultra-small system solution, has two integrated regulators, is available for external use, no crystal vibration required, and can be used as a solution. Operating temperature range is -40℃ to +85℃.

The STKNX device, combined with the STM32 microcontroller, can be paired with the KNX protocol stack software support of partners TAPKO or Shufan KAIStack, and the STKNX device is jointly developed in close cooperation with ST and TAPKO, and is certified by KNX to provide a complete solution for KNX twisted pair applications.


KNX Solutions

In terms of KNX wireless connectivity applications, ST also launched the KNX-RF multi-solution, which includes two chips, S2-LP and BlueNRG-2, which can be a dual radio solution supporting both KNX-RF and BLE, combined with the KNX-RF protocol stack software support from partner TAPKO. Can support the needs of more convenient wireless KNX applications.

ST's S2-LP is a high-performance, ultra-low-power RF transceiver for RF wireless applications in bands below 1 GHz. It is designed to operate in the license-free ISM and SRD bands of 433, 512, 868, and 920 MHz, but can also be programmed to operate in additional frequencies such as the 413-479 MHz, 452-527 MHz, 826 MHz-958 MHz, and 904-1055 MHz bands.

S2-LP supports different modulation schemes, including 2(G)FSK, 4(G)FSK, OOK, and ASK, with programmable over air data rates ranging from 0.1 to 500 kbps. S2-LP can be used in systems with channel intervals as low as 1 kHz and supports narrowband operation. The RF link budget for S2-LP long-distance communication is higher than 140 dB and meets regulatory requirements applicable to global regions, including Europe, Japan, China and the United States.

ST also introduced the BlueNRG-2 Bluetooth Low Power wireless single chip to pair with the S2-LP, BlueNRG-2 is an SoC single chip with ultra-low power Bluetooth BLE, compliant with the Bluetooth standard specification. The BluenrG-2 extends the capabilities of ST's existing BlueNRG family of Bluetooth network processors with a built-in Cortex M0 core to run customer application code.

The BlueNRG-2 also contains 256KB of programming flash memory, 24K static RAM with hold function (divided into two blocks of 12KB each), and standard peripheral communication interfaces such as SPI, UART, and I2C. In addition, BlueNRG-2 is equipped with multi-function timer, watchdog, real-time clock and DMA controller and many other modules.

The ADC module inside the BlueNRG-2 can connect to external analog sensors and read internal battery voltage sensor measurements, and a built-in digital filter can be used to process external PDM data streams. The BlueNRG-2 has the same excellent RF performance, and the built-in efficient DC-DC converter has the same ultra-low power characteristics, while improving power consumption in sleep mode, which can further extend battery life in practical applications.

ST, in close collaboration with TAPKO, paired S2-LP and BlueNRG-2 with KAIStack KNX protocol stack software, a KNX-certified dual radio solution that meets the needs of applications for low power consumption and cost optimization.

ST has launched a number of certified chipsets for KNX applications, including the aforementioned STKNX and STM32 twisted pair chipsets, as well as S2-LP and BlueNRG-2's KNX RF combined with BLE chipsets, and can also be paired with S2-LP and STM32 to become KNX RF supporting chipsets. And can be paired with TAPKO, Nanjing Sufan, Mike Equation protocol stack software to meet the wired and wireless KNX application needs.


KNX has an excellent track record in energy efficiency, and technological expansion in recent years has also allowed it to expand into using KNX technology for enhanced energy management purposes. KNX Energy Management is a proactive approach that aims to provide optimized energy use according to the needs of users at any given time, enabling people to create a more environmentally friendly environment, and KNX will play an important role in smart building energy applications. The ST wired and wireless KNX solutions introduced in this paper will be able to meet the diverse needs of KNX applications, accelerate the development of customers' KNX products, and seize the vast business opportunities of smart building energy applications.

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