|
|
|
|
|
|
|
|
Contents
1. Introduction: Is Standby a Technical Issue?
2. Typology of Products
2.1 The "on/off" product
2.2 The "standby" product
2.3 The "networked" product
2.4 Trends and
identification of technical problems
3. Overview of technical solutions
3.1 The "on/off" product
3.2 The "standby"
product
3.3 The
"networked" product
3.4 Summary of technical
solutions
4. Conclusions and recommendations |
|
|
|
|
|
|
Standby power consumption is an issue: a
significant protion of household energy use can be attributed to standby and
this portion needs to be reduced. But is standby power consumption also a technical issue, implying that technical
solutions are needed to reduce it?
Several reasons can be indicated why
technical issues are important regarding reducing standby consumption. Firstly,
standby is a function in most cases, so advising users to switch off an
appliances decreases functionality. E.g. when a European TV is switched off,
the remote control function is not available. Furthermore, it is not always
possible to switch appliances off and disconnecting appliances by pulling the
plug is in most cases not a practical solution.
Secondly, even in the situation where the
user did switch off an appliance (and thus choose for 0 functionality), several
appliances do not have 0 Watt power consumption. In other cases technical
solutions are a requirement for behavioural options.
Of course behavioural and psychological
aspects also influence standby power consumption. Sometimes standby modes are
disabled because users do not accept long wake up / recovery times. This
category of problems has a relation with technical aspects, because technical
developments can reduce wake up time. Also, giving proper information on the
warming up time ? a technical solution ? increases user acceptance of waiting
time.
Other psychological factors play a role:
some users do not like a black screen on their desk. It indicates that they did
not touch their computer for e.g. 15 minutes or more.
So, technical solutions will not solve all
problems related to unnecessary standby consumption. But in most cases
technical solutions either are the solution or provide a necessary requirement
for behavioural options.
This
paper is structured as follows. Chapter 2 introduces a simple typology for
products, which is then used in chapter 3 to give an overview of technical
solutions. Eventually, chapter 4 indicates some conclusions and recommendations
for further activities in the field of standby consumption |
|
| [top] |
|
|
|
|
In order to give an overview of technical
solutions, a simple typology of products is given:
* the "on/off" product
* the "standby" product
* the "networked" product
This is the most simple situation: the
product is either on or off, with off meaning that the product is performing no
function (except for being there and heating the room if energy is dissipated).
In case of an external power supply (or
transformer) it means that the transformer is in a no-load state (product is
not connected) or the rest of the product is switched off (performs no
function). In practice we encounter the "on/off " product as wall
warts (small external power supplies for e.g. personal audio equipment) or
external power supplies for printers, laptops or halogene lights. If these
products have an on/off switch, they mostly still consume power in their off
state, except in the case where the switch is on the primary side of the power
supply. However, in many cases this would be an extremely impractical place.
This type denotes the classical standby
situation, where the product is performing some function(s):, e.g.:
* enabling (remote) control, waiting for
a user command
* clock or other indicator
* internal timer
These functions can be found in a variety
of products: TVs, microwaves, fax machines and copiers to name a few. Sometimes
these products have an on/off switch. However, off doesn't always mean 0 W
power consumption.
This is an extension of the standby
product, meaning that the product not only can be switched into standby by the
user, but also by external sources, e.g. other products or a service provider.
Furthermore, the product itself can communicate with external sources, e.g. a
washing mashing calling a repair service.
This type of product is typically connected
to a network, either by (a) cable or wireless. Furthermore, the network
protocol used is an important technical issue.
From the discussion in the IEA task forces
it was noticed that no 100 % consensus existed regarding the question 'What is
standby?'. Especially functions like a clock or other indicators or products
like garage door openers or smoke detectors raised a heated debate. However,
the network trend will make this discussion obsolete. In the future a product
can either be characterized as an "on/off" product having no network
connection, or as a "networked" product.
For all categories the technical problem to
be solved is to optimize standby power consumption. However, this implies
different things for different categories. The "on/off" product should have
(close to) 0 Watt power consumption in the off mode. All consumption can be
regarded as waste, since the product is ? by definition ? not performing any
function.
The "standby" product should
minimize standby power consumption, whereas the "networked" product
should minimize (or optimize) total energy consumption. The latter is often
implemented by introducing a standby mode and thus increasing standby energy
consumption.
The next
chapter will deal with an overview of technical solutions for the product
typology. |
|
|
|
|
|
|
|
|
|
|
Regarding the typology of products
presented in the foregoing section, an overview of technical solutions will be
presented in this section.
For this type of products the focus should
be on the (external) power supply. Although no load power consumption of
external power supplies is decreasing, still relative large differences between
power supplies exist. E.g. external supplies for mobile phones: 1.9 W versus
0.7 W.
Technical solutions exist to reduce the
no-load power consumption to around 0.1 Watt or less; at least for small power
supplies. Note that an efficient power supply is also worth looking for in the
other categories.
An
alternative would be to have a hard (meaning 0 W) on/off switch on the primary
side of the power supply. In the UK an equivalent solution exists with the
on/off switch in the wall socket. However, both from a "practical"
user point of view and for cost reasons, a hard on/off switch is not a
practical solution for external power supplies. If 0 Watt is desired, it is
best to pull the plug out of the socket. |
|
| [top] |
|
|
|
|
Also in this category products with
external power supplies can be found. Furthermore, several products have an
on/off switch.
1.
A simple solution would be to equip the
product with an on/off switch resulting in 0 Watt power consumption. However,
this means by definition that the standby functionality is lost in the off
mode. Not all consumers are willing to use this mode, e.g. for TVs it is known
that in Europe about 50 % of the users never switch off their TV. In the US,
TVs do not even have a hard switch, so they have no off mode.
An alternative would be to power the
standby mode with solar cells or a battery. However these solutions have other
disadvantages, such as no solar power available in the dark, relative high
costs, enviromental aspects (waste) of batteries.
2.
The second solution is to decrease the
standby consumption itself. In general the following options exist:
* decrease the number of components that
are powered
* increase the efficiency of the components that are needed
for the standby function(s)
* add special "standby" components, e.g. a separate small
standby power supply
The first option can be implemented in a static way, i.e. during the design of
the product it is decided which components will be powered in the standby mode,
but it can also be used in a variable
way. A good example of the variable implementation is given by some VCRs. With
these products the user can choose at the first time use for serveral components,
e.g. the clock, whether they will be powered in standby. Of course, in this way
not only the standby power consumption but also the standby functionality is
influenced.
3.
Another
issue is how it is decided when the product enters the standby mode. This is
related to the concept of power management. In a simple situation a user
command is necessary to put the product into standby. In a more complex
situation the product itself can decide when it switches into standby, e.g.
based on inactivity.
|
|
|
|
|
|
|
Power management can be defined as a function of an appliance that ensures
- without user interference'- that the appliance is always in the state with the lowest power consumption
related to the required functionality.
Technically speaking this means that if the
appliance is not or only partly used, as much as possible parts are powered
down, and only those parts are powered that are needed to detect the
(increased) use of the appliance. This requires the following activities from the
product:
* monitoring activity levels of parts of
the equipment (devices)
* decision rules to enter a certain
state
* execute state transitions and monitor
the result
Power management is a concept that is
broader than standby, because also in the on-mode products can benefit from
power management.
In a non-networking environment, the power
management principle can be implemented straightforward, e.g. at a personal
computer using mouse and keyboard to detect activity of the user. However, in
the networking environment the
implementation of power management is more complex.
The
period of inactivity influences the standby consumption by a large extent. The
question is how to minimize the sum of standby power consumption and
consumption in other modes.
|
|
|
|
|
|
|
This is inevitable the most complex type of
product regarding standby power consumption. One of the key features of
networked products it that they are able to respond to requests via the
network. This implies that these products must be able to "listen" to
the network for relevant commands. Another implication is that the product can
not switch into standby without notification, because other products might need
its services. This also means that commands from the user are less imperative.
Currently, the "solution" is often
to have these products on all the time. So introducing a standby mode with
lower power consumption can reduce total energy consumption to a large extent.
However, truly networked products need a fairly complex power management system
to respond properly to external and internal requests.
Clearly an on/off switch is not a feasible
option if external parties need access to the product 24 hours per day. This is
e.g. the case for some set top boxes or PCs that are managed remotely.
Especially in large organisations it is necessary to install new software or
make backups through the network, because it is impractical and too costly to
treat each PC "personally".
Because listening to the network can be
power hungry, e.g. when a satellite dish has to be powered, a timer controlled
time window can be a solution. In this case the product listens to the network
during a predefined time window for new data. This can be e.g. a software
update or Electronic Programme Guide data. If in a time window data is transferred
to the appliance also the time for the following time window is programmed.
Most VCRs can be timer programmed to record
a TV programme.
However, the timer controlled time window
is not in all cases acceptable. E.g. some service providers require for security
(and bandwith) reasons that a settop box can be accessed at random without
prior notice. Furthermore, for truly networked products a timer controlled
solution is not feasible because it is not known when other products might need
the products' service.
In this case a rigorous and robust power
management system is the only solution. At a minimal level the appliance is
able to receive external signals. To process requests (for a certain action) a
Energy Management Stack can be used. Each running process puts a message on the
stack indicating which parts of the product are needed. If a process is
finished, resources that are no longer needed are switched off.
It is obvious that the network protocol
influences to a large extent the power consumption in standby of networked
appliances.
Table 3.1
provides an overview of technical solutions presented in this paper,
categorized regarding the type of product and the type of solution: hardware
(power supply and other components) and software (power management).
Table 3.1 Overview of technical solutions
|
Product type
|
Power supply
|
Components
|
Power management
|
|
"on/off"
product
|
* (external)
power supply
with low
(<0.1 W) no
load
consumption
* on/off
switch (0 W) |
|
|
|
"standby"
product
|
* on/off
switch (0 W)
* separate
power supply
for standby |
* decrease
number of
components
to be
powered
*increase
efficiency |
* detect when
to enter the
standby mode
* timer
controlled
window |
|
"networked"
product
|
* separate
power supply
for standby |
* increase
efficiency |
* timer
controlled
window
* power
management
* Energy
Management
Stack |
|
|
|
|
|
|
|
The
overview suggests the following conclusions and recommendations regarding the
implementation of the IEA initiative on standby.
Stimulate very low
no-load power consumption levels
No-load and
off power consumption is waste. Especially for simple "on/off"
products this consumption should be reduced to very low (<< 1 W) levels.
External power supplies are a global product for which global level should be
introduced as soon as possible.
If OFF then OFF = OFF
The IEA
initiative could encourage that if a product can be switched off, OFF = OFF. If
a product has an on/off switch, switching the product OFF should mean two
things: the product is not performing any function and the power consumption is
0 W.
This does
not mean that each product should have an on/off switch. As we have shown some
developments require equipment to be always in standby when not in use.
Power management with very low power levels is necessary
Industry should continue the work on the
implementation of a good working power management system not only for PCs but
also for set top boxes and all other equipment that will be never switched off.
Further developments need to be directed towards lower standby power
consumption levels, especially when industry promotes concepts where the
product is always in standby when not on.
Experience from the negotiations regarding
the European Code of Conduct for set top boxes shows that close cooperation of
all parties is needed.
Special attention should be given to
network protocols. They should support and facilitate power management.
Energy labels should guarantee trouble-free power
management
Energy
labels, like Energy Star or the GEA-label, should be a guarantee for buyers
that the system supports the power management implementation with the lowest
power levels. This includes the system as delivered to the buyer, including
network cards and other devices. |
|
| [top] |
|