When I decided to write about smart meters, I thought it would be fairly straightforward…explain what they are, why they are being introduced, what are the costs and benefits etc. What I have discovered is that the world is split into three groups…people like myself who hadn’t given the subject much thought and were therefore neutral, and then two opposing groups with massively polarised views, with “Smart Meters will Save the Planet” on one side battling against the “Smart Meters are a Stalinist Evil that Must be Stopped” on the other (with various colourful claims such as smart meters can cause your blood to curdle while setting fire to your home).
What I struggled to find was actual data.
The first known electricity meter was patented by Samuel Gardiner in 1872, and throughout the late 19th century various designs were proposed in order to measure and bill for the growing commercial use of electricity. The most common type of meter in use today is the electromechanical induction meter, which works by counting the revolutions of a non-magnetic metal disc which rotates at a speed which is proportional to the amount of power passing through the meter.
Radio activated meters have historically been common in the UK, in order to facilitate cheaper overnight tariffs eg Economy 7 which provided off-peak rates between midnight and 7am. The meters were activated by a radio signal carried within the longwave carrier of BBC Radio 4 (198 KHz) and it was common for households to charge storage heaters and heat water by immersion during the cheaper night-time period. These schemes fell in popularity as gas became cheaper and storage heaters were found to be complicated to use and inefficient.
The next generation
Among the major drawbacks of traditional electricity meters is that they only measure total consumption, and that they must be physically inspected in order to determine the exact amount of electricity used. This means that unless dual-tariff meters (such as were required for schemes such as Economy 7) were installed, it was not possible for utilities to use tariffs as a means of modulating consumer demand. It also meant that bills were often based on estimated readings, which has contributed to wide-spread consumer confusion around billing.
This has led to the development of smart meters which provide near-real time consumption data and can be combined with power monitoring systems to inform consumers not just about their overall consumption at different times of day, but also help them to understand how this consumption is broken down across their different appliances. The ultimate objectives are to improve consumer awareness of their consumption, and to support demand reduction strategies through adaptive pricing where tariffs vary depending on demand or the time of day.
The technical challenge
Smart meters carry out two primary functions: measuring consumption and communicating the data back to the energy suppliers, and communicating consumption data to consumers via an in-home display (“IHD”). The meters are therefore carrying out long-range data exchanges with utilities and short-range communications with IHDs.
Ideally in-home smart devices should use wireless transmitters that consume very little power, but with signal strength that can pass through walls and floors and even outside the property (meters are often located outside, or in cellars) without interfering with other networks.
Standard WiFi consumes a lot of power, so while it works well for high volume data streaming, it is not suitable for Internet of Things (“IoT”) devices, including smart meters. As a result, other technologies have evolved that use less power, and often also work in mesh configurations, to reduce point-to-point distances. There are four major protocols that work within the IEEE 802.15.4 standard for low-power, low-speed networks: Bluetooth LE, ZigBee, Z-Wave and Thread, however, they operate at different frequencies, and are largely incompatible with each other. Even devices developed on the same protocol are not always able to communicate, as different manufacturers adopt different implementations.
DECC has selected ZigBee as the wireless technology by which smart meters in the UK will communicate with in-home displays, because its mesh technology allows it to work over long distances and through thick walls which often separate meters from living areas. However, due to concerns that consumers may disconnect some of the mesh devices, a bespoke ZigBee specification has been developed for the UK which should have even longer range to reduce the need for nodes in the mesh.