Scope
It specifies terminology, principles and concepts for energy efficiency and energy management. It establishes a common understanding of energy efficiency and management and measurement methodology and its usage as a framework for other ITU-T standards or SDO documents.
Summary
L.1315 defines Energy efficiency as “The percentage of total energy input to a machine or equipment that is consumed in useful work and is not wasted as useless heat”. For ICT it is important to consider not only energy consumption and energy efficiency (h) but also the Energy Efficiency Rating (EER). EER as a device metric shows how much of the input energy is used to perform a functional unit of the IT equipment (e.g., bps/J).
The energy efficiency metric is defined for 3 different levels: (1) Network/solution level (2) equipment/system level, and (3) component level. Levels (1) and (2) are considered and used for testing and evaluation of EE and EER, (3) only as suggestions, e.g. to improve the energy efficiency of equipment.
Useful work concept for ICT EER: The concept “useful work” defines the expected results to be delivered by a device/the respective functional unit. For wired technologies, the following concept can be utilised:
- Utilisation: port and system as a % of a theoretical maximum
- Throughput: port (rate of traffic (b/s) including min. needed line overhead) and system (sum of port throughputs)
- Line rate: Indicates the actual speed with which the bits are sent onto the wire (or via wireless connection)
Additional for wireless technologies:
- Coverage area: geographical area in which mobile radio stations provide service
- Path length: radio link length, e.g. distance between two radio stations of the radio link
Also important for a network: Number of users, service per user, total network egress traffic (and energy used).
Functioning status and utilisation are important factors for EE(R). For equipment for which it is possible to define typical utilisation percentages for the different modes (i.e., idle, low power, and maximum), the example formula below, with weights for different modes, can indicate EE(R). Tidle = throughput in idle mode in which power is Pidle (and similar for Tlowpower, Plowpower, Tmaximum, and Pmaximum).
The general measurement conditions are specified including Temperature, Humidity, Barometric pressure, Voltage DC/AC, characteristics of power measurement equipment requirements (e.g., digitising sample rate of min. 40 kHz, min. bandwidth of 80 kHz, ability to log and store data, accuracy ± 1%).
Additional info: EE is independent of energy sources. Thus, using renewable energy does not influence EE (but still has an environmental impact!). Also, EE or EER are not equal to energy management, which does not directly affect EE. Thus, the energy management concept defined by ETSI does not cover the efficiency of the equipment but how energy is used, managed and delivered, as well as how waste energy is reused. However, because of that, energy management helps to manage the effect that equipment, networks and services have on the environment.
Relevance for EXIGENCE
Relevant for requirements and scenarios, energy metrics, energy measurements and data collection.
