The benefits of energy-saving electronic monitoring and control systems for 'smart houses' are becoming better known, and sales of home energy management system (HEMS) products are expanding quickly in Japan and around the world. Simultaneously, operational protocols and standards are being set, enabling easy configuration optimization. Renesas is helping system engineers save time when developing better products for the smart home and HEMS markets.
Collecting energy usage data and controlling consumption intelligently
Growth in the worldwide 'smart house' market is accelerating rapidly, driven in large part by rising environmental awareness and growing government support. This huge sales opportunity encourages system engineers to combine and apply information technology and embedded electronics in new ways to better manage energy usage within households.
A home energy management system (HEMS) reduces energy consumption and thus it is the core feature of a smart house. Electronics interconnects all of the energy consuming and producing devices (see Figure 1).
A HEMS installation lets residents see and act on updated status information and makes them aware of consumption trends they wouldn't otherwise notice. Armed with these data, they can implement socially responsible conservation measures that decrease their utility bills. And by submitting consumption information to service providers for analysis, they can learn how to obtain maximum benefits.
Standardizing interfaces gives installers more choices for HEMS optimizations
The lack of standard operational protocols and electrical interfaces has previously impeded the growth the growth of smart house and HEMS markets. Incompatibilities between system elements limit energy-saving capabilities. Thus, implementing standards that allow seamless interconnections between devices from diverse manufacturers currently is a strong industry imperative.
Technologists in Japan took an important step in this regard in 2012. The Ministry of Trade, Economy, and Industry, together with the JSCA (Japan Smart Community Alliance), designated the ECHONET Consortium's ECHONET Lite protocol as the country's recommended standard for HEMS equipment. This middleware fits between the communications layer and the application layer of a home energy management system (see Figure 2).
Ensuring the compatibility of ECHONET Lite system components
Products compliant with the ECHONET Lite protocol-—regardless of the manufacturer—are guaranteed to work in HEMS installations and can be installed without new wiring. They enable extremely versatile smart energy management systems at prices driven lower by competition.
Other countries have developed different standards for interconnecting HEMS products. U.S. equipment makers, for instance, have agreed to use the ZigBee Smart Energy Profile (SEP) 2.0. Companies in the European Union, by contrast, have standardized on the KNX protocol.
Networked products that work across the widest span of markets have the greatest sales potential. Renesas anticipates that versatile ECHONET Lite middleware will eventually coordinate or merge with other national and regional interface standards.
Supplying simple, reliable solutions to HEMS equipment designers
Standardized communication components open up vast HEMS markets. Renesas provides advanced solutions that accelerate the development of products that interconnect seamlessly. Our advanced semiconductors, modules and support products let system engineers focus on features that add value and gain market advantages.
A typical system for controlling room lighting and temperature (see Figure 3) shows some of the components Renesas provides for energy management applications, including those that use three popular communication methods: ZigBee RF4CE wireless, Wi-SUN wireless, and PLC (power-line communication).
Renesas' networking solutions let HEMS installers select the best communication protocols for each remotely located system element. Our transmitter/receiver (modem) modules are thoroughly tested and approved, offering regulatory compliance that simplifies product development.
Highlighting the differences between communication alternatives
ZigBee, Wi-SUN and PLC protocols have different characteristics and advantages:
- ZigBee RF4CE wireless is ideal for remotely located components that control switches and make adjustments. This short-distance, low-speed communication protocol offers excellent operational responsiveness and low cost. It uses the 2.4-GHz band available throughout the world for this type of application.
- Wi-SUN wireless is ideal for networked sensors and transducers. It uses sub-GHz bands (in Japan, 920 MHz), lower frequencies that reduce blockages caused by obstacles. Also, it achieves better communication stability than protocols in the 2.4-GHz band.
- PLC is ideal for controlling air conditioners, major appliances and lighting systems. It uses existing power lines and outlets, establishing reliable communication that isn't blocked by walls, ceilings or floors and doesn't require new wiring.
Delivering reliable plug-and-play communication modules
Figure 4 shows the digital communication modules Renesas sells. Each has been type-designated by MIC in Japan and is certified to be compliant with the statutory technical standards (Radio Act), thus eliminating concerns about compliance issues. We also offer sample software that engineers can use to rapidly evaluate these modules.
Keeping abreast of revisions and extensions to communication protocols
Communication protocols are subject to extensions and revisions that can cause design issues for engineers creating HEMS products. To ensure that our modules deliver the latest approved characteristics and capabilities, Renesas participates in alliances that manage these standards (see Figure 5)
Standardization efforts at the many companies and organizations in our robust support ecosystem bolster our work. We collaborate with numerous technology partners to create innovative HEMS design solutions.
Offering multiple design choices for dedicated HEMS controllers
Renesas manufactures multiple types of microcomputers for HEMS central controllers. Our chips readily handle the requisite monitoring, evaluating and energy-consumption optimization tasks.
Our 16-bit RL78/L1C MCU, for example, is an excellent choice for central control units (see Figure 6). Besides interfacing with communications modules, it can implement LCD panels, audio outputs, touch-key operation, sensor control, and USB communication and charging. Its support includes the RL78/L1C HMI solutions kit, a valuable system development tool.
As figure 6 shows, this solutions kit implements touch-key input and audio output for user-friendly control panels without external IC support. A general-purpose I/O port handles the touch-key input, and a digitally amplified PWM circuit implements the audio output. The MCU's UART ports interface to all types of serial communication links.
For HEMS installations that require central controllers with greater capabilities, we recommend the MPUs in the RZ/A1 series. These new chips achieve up to 1000 DMIPS throughput and have up to 10MB of on-chip RAM. They support full WXGA touch-screen displays for exceptional HMI (human-machine interface) performance and integrate many other on-chip peripheral functions.
The remotely located sensors, switches and actuators to which a HEMS central controller connects can use lower-performance MCUs. We generally recommend RL78 chips for such applications.
Maintaining product excellence and strong support to encourage market growth
This EDGE story highlights important Renesas solutions for smart home and HEMS applications. These products help system engineers sidestep the technical hurdles involved in implementing new standards, thereby accelerating innovation and progress. Our entire ecosystem is geared to help manufacturers rapidly enter and successfully thrive in exciting new markets.
Renesas welcomes your questions and comments. Please click on the "Contact Us" link on our website and let us know what you think.