Operational functions

Fundamentally, an ICE appliance, such as a television, consumes a certain amount of electricity to provide its operational functions (i.e. vision and sound). The intensity of this electricity consumption is a central factor in determining the overall energy consumption from the appliance. Subsequently the type and power characteristics of an appliance will influence household electricity consumption. Due to the range of features that ICE appliances now offer, devises will frequently possess a variety of power requirements (Fung, Aulenback, Ferguson, and Ugursal, 2003). For instance, in the UK, televisions commonly operate with the use of a remote control, which can be used to turn the device

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on and off, without using the on/off switch located on the appliance or disconnecting it from the mains power supply. When a television is turned off by the remote control it often continues to draw electricity from the mains supply, in readiness to be turned on again remotely. A device in this operational state is commonly referred to as being on “standby”.

Many ICE appliances can also consume standby power when the remote feature is disengaged (by using the power switch on the device) and the device is simply plugged into the mains supply. This energy use commonly occurs as a result of product design, which allows components (such as transformers and switch mode power supply units) to maintain a current from the mains. Although standby power may be relatively small, its importance should not be underestimated. Standby power often operates 24 hours a day, each day of the year, and thus can exceed active power use for some devices on an annual basis. Therefore, the collective standby power from a nation‟s appliances can account for a significant amount of energy consumption. In 2007 the International Energy Agency estimated this to be between 5% and 10% of total electricity use in most homes (IEA, 2007a).

Although standby power is a term used throughout energy literature, its meaning varies considerably. The European and British Standard definition of the standby power mode is expressed through BS EN 62301:2005 as the:

…lowest power consumption mode which cannot be switched off (influenced) by the user and that may persist for an indefinite time when an appliance is connected to the main electricity supply and used in accordance with the manufacturer‟s instructions.

(BSI, 2005 p6)

This is consistent with US Department of Energy (DOE) and the International

Electrotechnical Commission (IEC) definitions. In essence, standby power is “the lowest power when connected to the mains electricity supply” (Harrington et al., 2007 p1286).

Other definitions of standby power have included a broader range of power modes. The IEA states that:

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Standby power is the electricity consumed by appliances while switched off or not performing their primary functions.

(IEA, 2007b p1)

The term “not performing their primary functions” includes additional power modes, such as when a television is turned off by the remote control or when a compact disk (CD) player has finished playing a CD, and the display is still functioning. For these two examples, there could be a lower power level when the television or CD player is simply plugged into the mains, which by the BS EN definition is the true standby power mode.

Differences in operational features between appliances types, and similar appliances produced by different manufacturers (e.g. some appliances can only be activated with a remote control), also make it difficult to define standby power, because standby power is irrespective of functionality (Payne and Meier, 2004).

Payne and Meier (2004) argue that due to appliances lowest power consumption occurring in different operational modes, that:

…"standby" is a power level, not an operational mode. While it is sometimes more convenient to talk about a product's "standby mode", that really refers to the mode at which the device consumes its standby level, since there is no mode consistent across all devices that is the standby mode.

(Payne and Meier, 2004 p11-143)

Payne and Meier describe a number of “low power modes”, which are in between the unplugged and active power modes, and categorise them as sleep and “off” modes.

Figure 2-1 below illustrates these power modes and power levels for a typical ICE appliance. It is apparent that although the energy consumption from the “sleep” mode does not contribute to any actual use of the appliance, neither can it be categorised as standby power due to the lower “off” power mode.

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Figure 2-1 Depiction of appliance power modes (Payne and Meier, 2004 p11-143)

The existence of low power modes, not covered by the BSI, IEC and DEO definitions of standby power, has led to a more complex definition within the recent Eco-design of Energy-using Products (EuP) Directive. The Directive states that:

„standby mode(s)‟ means a condition where the equipment is connected to the mains power source, depends on energy input from the mains power source to work as intended and provides only the following functions, which may persist for an indefinite time:

- reactivation function, or reactivation function and only an indication of enabled reactivation function, and/or

- information or status display;

(European Commission, 2008 p46-47)

Despite the emergence of a more inclusive definition, the complexity of standby power is still a problem for any party involved in appliance power measurement, because it is difficult to make an accurate comparison of different products that are continually

developing more complex power requirements. For example, Jones and Harrison (2009)

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describe work to create a new power measurement method for STBs (the next edition of the IEC 62087 standard). The authors highlight that eleven measurements are required to cover all the potential operational modes of a STB (Jones and Harrison, 2009).

Televisions with internal digital signal receivers have also become more challenging to measure due to the development of more complex functions. Four standby power modes can be defined for televisions: (i) Off standby (appliance is connected to a power source, provides neither sound nor vision, cannot be switched into another mode with the remote control, an external or internal signal; (ii) Passive standby (appliance is connected to a power source, provides neither sound nor vision, but can be switched into another mode with the remote control or an internal signal); (iii) Active standby low (as with passive standby, and can additionally be switched into another with an external signal); (iv) Active standby high (as with active standby low, and is exchanging/receiving data with/from an external source) (Jones and Harrison, 2009).

This situation creates difficulties for a researcher interested in monitoring appliances, because the differentiation between power modes becomes difficult when using field monitoring equipment that cannot measure power consumption to the same resolution as laboratory equipment. Further uncertainty relates to whether continuously operating low power devices, such as network and telecommunications equipment, should be included in standby power consumption investigations (Harrington et al., 2007). Network appliances, such as STBs, routers, modems and telephones, have the primary function of linking households to external network systems, such as television services and the Internet.

Many network appliances often remain continuously in an active power mode, even when a television or computer was not being used. By definition, an appliance being used in this way is always in the active power mode. However, electricity consumption from network appliances, when a television or computer is not also active, can be considered as a form of standby power consumption, because rather than delivering their primary functions the devices are effectively in a state of “ready” or maintaining network integrity (i.e. is providing a similar function to the active standby mode).

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As a result, some important appliance studies have included active network appliances in their evaluations of standby consumption. For example, many of the STBs included in the exemplar study by EES (2006) were in the “on mode”. The research found that around 60% of owners “left their set top box in active standby mode for 24 hours of the day” (EES, 2006 p31) and that these appliances were of particular importance to standby

consumption due to their relatively high continuous power loads. Similarly, in the

REMODECE project, electricity consumption from STBs and routers, that were active but not being used, was also categorised as a form of active standby consumption (Grinden and Feilberg, 2008; De Almeida et al., 2008). This complex situation is reflected in research by McAllister and Farrell who argue that “the standby condition varies by

appliance and thus lacks specificity” (McAllister and Farrell, 2007 p1178). In their research they avoided using the term standby power wherever possible in order to retain clarity.

Despite issues of clarity this thesis has chosen to refer to the term standby power, because of its widespread use throughout existing literature and in policy circles. This study also classifies electricity consumption from active network appliances, when the associated televisions or computers are not active, as active standby consumption.

Despite concerns over the exact definition, this approach allows a more representative assessment of the electricity consumption from network appliances to be gained, because it separates electricity consumption that is not providing an appliance‟s primary function or providing a “useful” purpose. Thus, this thesis uses the term “standby consumption” to represent electricity consumption, from a range of low power loads that did not provide appliances‟ primary functions.

For this research standby power is subdivided into active, passive and off standby modes, to reflect the terms used in IEC standards and previous research studies, such as the EES standby study (EES, 2006). This approach was also used by the International Standby Power Data Project (2008), which aims to collate appliance standby power consumption data from a number of countries (ISPDP, 2008). Table 2-1 below provides definitions of these power modes.

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Table 2-1 International Standby Power Data Project (2008).

Power mode Description

Active The power used when the appliance is performing its primary function (e.g.

when a television is on and providing images and/or sound).

Active standby

The power used when the appliance is on, but not performing its main function (e.g. when a DVD recorder is on but not recording or playing).

Passive standby

The power used when the appliance is not performing its main function, but is in a state waiting to be switched on or is performing a secondary function (e.g.

when a television has been switched off by the remote control).

Off standby Off standby mode is when an appliance, that has an off switch, is connected to a power source, but is not waiting or performing any function. It can only be activated when the power switch on the appliance is activated (e.g. when a computer monitor is switched off, but still plugged into the mains power supply).

Although this approach neglects other standby modes, such as active standby high and active standby low, it is believed that a significantly detailed assessment of standby power can be gained from this approach. In addition, these definitions allow a degree of

harmonisation to power mode definitions for computing appliances outlined through the US Environmental Protection Agency‟s long established Energy Star energy labelling initiative for ICT equipment (the success of which has resulted in its adoption across the EU). The Energy Star definitions are presented in Table 2-2.

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Table 2-2 Computer power mode definitions (Energy Star, 2009) Power mode:

Energy Star

Power mode:

Thesis

Energy Star description

Active state Active The state in which the computer is carrying out useful work in response to a) prior or concurrent user input or b) prior or concurrent instruction over the network. This state includes active processing, seeking data from storage, memory, or cache, including idle state time while awaiting further user input and before entering low power modes.

Idle State Active standby The state in which the operating system and other software have completed loading, a user profile has been created, the machine is not asleep, and activity is limited to those basic applications that the system starts by default.

Sleep mode Passive standby A low power state which the computer is capable of entering automatically after a period of inactivity or by manual selection. A computer with sleep capability can quickly “wake” in response to network connections or user interface devices with a latency of ≤ 5 seconds from initiation of wake event to system becoming fully usable including rendering of display.

Off mode Off standby The power consumption level in the lowest power mode which cannot be switched off (influenced) by the user and that may persist for an indefinite time when the appliance is connected to the main electricity supply and used in accordance with the manufacturer‟s instructions.

A final important aspect of standby power electricity consumption is whether one considers electricity consumption from all of the standby power modes to be wasted energy.

Electricity consumption from the off standby mode can be regarded as wasted energy, because it does not provide a function. However, in many situations passive standby and active standby power does provide a function. For example, passive standby power enables the remote control reactivation function for televisions and active standby power allows software updates, from service providers, to be transferred regularly to STBs. The value of standby power can therefore be subjective, but for those involved in the

environmental agenda there is a general consensus that most standby functions are not essential and do not warrant the amount of electricity that they consume. As a result, standby consumption has become the focus of both technical and social energy research

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and has led to a variety of policy initiatives to reduce household consumption through improved product design and behaviour change.