Energy consumption awareness is a crucial step in going green as an individual consumer. Real-time energy usage data aggregated at the home-level by smart meters is useful, but drilling down to the energy consumption of each major home appliance is even better and more actionable. Standards such as ENERGY STAR® are undergoing revisions to include provisions for “connected” appliances. Appliances that meet the “connected” criteria can receive an extra allowance towards their energy use for ENERGY STAR qualification. Additionally, these appliances will be highlighted as “connected” on the ENERGY STAR qualified product list. One of the requirements for being “connected” includes the built-in capability of appliances to measure and report energy consumption. Low-cost components to perform energy measurement are key to enable widespread integration of this functionality in appliances.
The key components for energy measurement include voltage and current sensors, an analog front end (AFE) to interface with these sensors and a microcontroller to perform energy measurement calculations. The energy measurement results are then output to a LCD screen or sent over the serial bus to another device for wireless communication. Since energy measurement on these individual appliances are not used for billing purposes, the accuracy requirements are not as stringent as those of utility-grade meters. Additionally, the maximum currents to be measured are also smaller compared with utility meters. These factors enable choosing components that are not costly.
Energy metering ICs available today integrate many of the components described above to enable low-cost solutions with minimal part count. The MSP430AFE2xx energy metering IC from Texas Instruments Incorporated (TI) includes multiple 24-bit Σ∆ ADCs, programmable gain amplifiers, MCU, serial peripherals and TI’s MSP430™ Energy Library software suite to enable simple, low-cost implementations of energy measurement circuitry. Data can be sent to a LCD driver or a wireless device over a standard serial interface such as SPI or UART. Such software-programmable solutions provide flexibility to the system designer to tailor the solution to specific application needs. For example, implementing a non-standard communication protocol to send energy consumption data to a host processor. Low-power consumption of the MSP430AFE2xx microcontroller is important in being able to employ a low-cost capacitive supply to power the microcontroller. Once calibration is performed during development, the same calibration constants can be programmed into each MSP430AFE2xx unit during production to easily achieve 3% or better accuracy. This significantly lowers production costs.
What are your thoughts on appliance sub-metering and the MSP430AFE2xx for energy metering?
Read more about energy measurement for appliances in this ECN article.
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