Taking the experience with cutting the standby power consumption of consumer electronics items such as TVs as an example of successful lobbying, the International Energy Agency (IEA) has now turned its focus to slashing the electricity demands of network-attached devices. The agency has published a report that calls on governments to mandate lower energy limits for networked devices and for manufacturers and service providers to change the way the devices are designed.
The authors of the IEA report “More Data, Less Energy” were concerned that an often overlooked issue “is the rapidly rising energy demand from literally billions of devices that remain ‘on’ but may be used for only a few minutes or hours each day. Currently, the estimate for global electricity wasted in this way by network-enabled devices is 400TWh per year…Addressing this energy waste, through technology and policy solutions already available, could lead to energy savings that correspond to the annual electricity generated by 133 mid-size coal-fired power plants (500MW each), each requiring 1.4 million tonnes of coal per year”.
The report claims up to 80 per cent of electricity consumption in devices is used just to maintain a network connection while they wait for something to happen. Although the energy usage of each device may be small, sheer numbers result in considerable consumption. But by implementing the best available techniques, consumption could be cut overall by 60 per cent.
The report argues: “No technical barriers exist to making network-enabled devices substantially more energy efficient. Rather, the challenge is that people all across the value chain – from network designers and device manufacturers to operations managers and individual consumers – are either unaware of the energy issues or have little incentive consumers – are either unaware of the energy issues or have little incentive to engage actively in resolving them.”
As mobile devices can maintain network connections for as little as 0.5mW, the report mainly focuses on wired systems. “Of greater cause for concern is the growing energy demand of billions of edge devices and user-premises network equipment, scattered in offices and homes around the world. While the individual energy consumption of each device may not seem high, cumulatively these devices currently constitute more than 40 per cent of ICT demand.”
A 2013 NRDC analysis of a network-attached gaming system showed that 80 per cent of its energy was consumed while in its low-power active mode. A similar analysis of set-top boxes and smart TVs indicated that they drew two-thirds of their energy demand when inactive.
Aggressive power management
The main recommendations are for not only devices to implement power management more aggressively but networks to be designed to allow a greater degree of freedom for devices to power down – instead of demanding they remain in a high-activity state simply to respond to keep-alive messages – and to scale energy demand according to actual workload.
“A priority [should] be placed on the establishment of industry-wide protocols for power management…Currently, networks understand only ‘present’ or ‘not present’; there is no concept of ‘sleep’. So, if a device is “asleep” and does not respond when the network sends a signal, it is thrown off the network with the possible impact that it will stop receiving the information required to perform its functions,” the report says.
If protocols cannot be changed, manufacturers should look at techniques such as low-power proxying to provide the illusion of ‘present’ for sleeping devices. The report also argues for the use of energy harvesting to “ensure small energy loads due to network connectivity do not cumulatively add up to a large growth in electricity demand”.