Ethernet-enabled energy optimisation is rolling out
As energy-aware devices begin to roll into the marketplace, manufacturers are poised to reduce energy costs
by 20-30% using intelligent, Ethernet-based networking as an enabling technology.
With open interface
standards such as PROFIenergy, Sercos Energy and the CIP Energy Object definitely on users' radar, energy
optimisation is set to become a major system architecture topic. Al Presher talks to Carl Henning of North
American PI, and Bosch Rexroth's Scott Hibbard
THE STAGE IS SET for Ethernet-based energy
management to become routine policy for endusers
and machinery builders implementing
automation projects. The first objectives of the
new energy measurement protocols will be to
place systems into standby mode during
production pauses to reduce energy usage.
Even though the base technology has been
ready for a year or so, moving to application
deployment has taken time to develop. But
now with the first wave of open interface,
energy-aware devices coming to market, the
uptake will increase as companies explore how
to integrate energy priorities into real-time
automation machinery control loops.
Open interface standards
'Before the release of Sercos Energy, we had
already been putting energy functions in our
products, but now we are converting over to
the open interface standard for our drives,
CNCs, and motion controls,' said Scott Hibbard, Vice President of Technology, Factory
Automation for Bosch Rexroth.
'The standardised version for controllers will
be in prototype units early in 2013 for
customers to try out on their machines,' said
Hibbard. 'The new controls will use the Sercos
Energy information in conjunction with
function blocks in the PLC programs as part of
Rexroth's 4EE Energy Efficiency program for
The idea is for an IEC-61131 Energy Efficiency
function block to pull in data from Sercos
Energy-capable devices, and present that information
to the programmer who in turn, can
create functions to monitor energy usage and/or
tune down devices. By performing calculations
on the overall equipment switching cycle, the
programmer can determine under what circumstances
energy functions should place a piece
of equipment into power-down mode.
While these capabilities are not out in the
field, the development process is far advanced. Hibbard says it has been a complex process to
pull all of the variables into a control structure
that allows engineers and programmers to work
efficiently on specific applications. With a large
amount of data available, the question has
become one of using it all in an effective,
coherent solution. Achieving this has required
the cooperation of end-users.
'The problem is that you can provide a lot of
data but, if it isn't easy to program the system,
people won't do it,' said Hibbard. 'The goal is
to find clear methods of presenting the information
to the programmer, but now we have a
function block that does the job.'
Implementing energy monitoring in an application
is relatively simple because it takes an
aggregate of the energy consumed by all of the
devices, and measurements set against time slots
recorded from the Sercos clock. A graph that
shows a CNC block number, for example, and
system energy consumption at a specific time
may be easily constructed from this. The graph
will show if the system is running, in cycle or
out of cycle. Using this technique provides a
method to collect detailed energy usage information
on parts of the process and individual parts
of the line. Users are also able to analyse the
data for resource management purposes.
Managing energy during pauses
'Saving 20-30% of energy just by entering
standby mode during production pauses shows
potential savings of hundreds of thousands of
dollars in larger automotive plants,' says Carl
Henning, deputy director for PI North America.
'In some parts of the world, companies are also
penalised for their carbon footprint. So implementing
PROFIenergy, in addition to saving
money, also becomes a huge deal if carbon
credits are a factor for manufacturers.' Some
companies, notably Wal-Mart, are also
demanding that their suppliers reduce their
PI International has conducted an extensive,
highly instrumented study of different
automotive plants, examining what happens
during a production pause. The conclusion from
that study is that up to 30% savings are
achievable and, from the automotive industry
standpoint, it looks like a promising opportunity
to reduce costs.
'What we are now concentrating on is where
PROFIenergy is applicable,' said Henning. 'We
recently did a study in the logistics market on
applications that typically include a series of
conveyors, cranes and systems to determine
potential energy savings by placing devices
into standby mode when they are not needed.'
Henning reported that the automotive
companies, who have been the primary impetus
behind this development, are only just starting
to complete the first installations with the new
model changeovers - there is, as yet, limited
feedback in real customer data.
The upgrade process has primarily been a
software change in two parts. Where operators
use existing I/O, a firmware update adds the
PROFIenergy capability. In the case of a
controller, vendors typically introduce a
PROFIenergy function block which is used to
take advantage of the additional features. With
new installations, since PROFIenergy is being
integrated into the newer I/O and controller
products, the updates are not required and
device updates are easily done on the job.
As for energy measurement techniques, more
customers are starting to implement these
functions, and third-party software packages
using PROFIenergy are being designed specifically
for energy management. 'From an
engineering point of view, the PROFIenergy application
profile provides a series of commands
including the ability to START PAUSE and END
PAUSE,' said Henning. 'The key for systems
engineers is to determine what devices and
systems can be placed into standby mode, how
long a device should stay there and how it relates
to the other machines in the production line.'
An example PROFIenergy system consists of a controller, a conveyor belt and a robot. Based on the production
process, the conveyor belt may only be switched off two minutes after the robot, and must be ready to operate two
minutes before the robot. PROFIenergy is used to determine the time behaviour of the conveyor and robot with switch-on
and switch-off times set at one minute each. The device must be switched to energy saving mode at least two minutes
before it may be switched on again to establish the production pause.
The challenge is to coordinate the starting and
stopping of various functions effectively, and
details such as determining how long it takes
for a system to go from being off to being on
again. The process is not trivial but, like implementing
safety and security systems, it's one
more thing that the engineer has to account for.
This seems to be a user-driven Ethernet-based
technology, although automation suppliers are
definitely looking for products with PROFIenergy
compliance. They think that it will be a selling
point for their machines, but want a simple way
to achieve it.
'Adding PROFIenergy to a new application is
not a difficult task, and the implementation can
really become commonplace,' Henning said.
'Retrofitting an existing system requires changes
to the application code and also the logistics of
updating the I/O firmware in the field. For new
applications from a technical point of view, the
biggest task is developing strategies for pausing
devices and planning out how the systems
respond to different conditions. Implementing
the strategy is actually straightforward but the
planning phase is the most demanding because
of the need to understand the different aspects
of system operation.'
PROFIenergy specific use cases
From the beginning, the goal has been to
address four use cases. The first three all relate
to what happens during a production pause,
whether it is short, long or even an unplanned
pause. The impetus came from a study by
Mercedes Benz which suggested that, even
when they were not making cars, they were
using 60% of the energy required for production
during downtime. The company set itself a goal
of reducing energy consumption by 20%.
The fourth use case relates to data movement
over Profinet. It has to be given a standardised
form. With PROFIenergy, the goal is to take the
information related to energy measurement, and
to establish a fixed profile to enable its
predictable use - for instance in estimating peak
demand. With billing periods now measured in
15 minute periods, responsive demand shaving
saves money. That might include putting a
system into standby mode, or reducing power
consumption within the system.
While the Ethernet-based energy capabilities
are taking time to find their way into factories,
nearly all of the new products from Siemens, as
expected, now are PROFIenergy compliant.
Other vendors, even smaller ones, are also
introducing PROFIenergy-based products.
Energy analysis tools
Bosch Rexroth has an additional tool for use
with its CNC products, the ega Energy Analyzer,
which provides an energy monitor and creates
the ability to view energy usage down to submillisecond
increments. It can record a
complete cycle and builds a file that engineers
may use to view the aggregate energy usage
of individual devices.
Before standards such as Sercos Energy,
Hibbard said it was relatively easy for a vendor
to pull energy information from its own devices
but hard or impossible to gather information
from third-party devices. There have been
function blocks that can be dedicated to a
pump, for example, where a user can turn the
pump on and off, and put values into the
function blocks to record energy usage. The
pump draws a specific amount of energy to turn
the pump on, get up to speed, run constantly
and stop. That process, in the past, has been manual work for the programmer and the information
was not always accurate.
'The next step is for the device supplier to put
together a profile of energy usage or use sensors
to provide this information,' said Hibbard. 'If
the device on the network reports that it is
Sercos Energy compliant, it can provide information
on the energy required to start, run or
stop. With this information, an energy
management system becomes much easier to
incorporate into the application program.'
Higher level enegy control can make predictions,
perhaps plan a pause ahead of time while
the application is unclamping the part and
moving for example. It may make sense to idle a
specific device on the machine to save energy; the
goal is for energy data to become a real-time part
of the control loop, controlling use of individual
devices and optimising energy utilisation.
'Just by collecting energy data, it is possible
to optimise the duty cycle of a particular
process,' said Hibbard. 'For example, it reveals
when it isn't necessary to accelerate an axis at
a maximum rate if it can be ramped up more
slowly to save on energy during the acceleration
while still meeting production requirements.'
But it's also important within a cycle for the
control to make intelligent decisions on idling
back specific devices to reduce energy usage.
Those kind of decisions made in a closed loop
can begin to save a lot of energy with very
'Energy efficiency is something new for the
system engineer,' said Hibbard. 'There should
be a minimal amount of ramp-up and education
for an end-user or machine builder to start
using this technology. Once engineers begin
to do this as a matter of course, they will be
absolutely startled by the amount of energy
savings they can produce - and how much
energy has been wasted in the past.'
In the past, a physical PLC output may have
been used to turn a pump on. If that device is
network-capable and has an RJ45 Ethernet
connector on it instead of a terminal strip, it
can be plugged into the network. Traditionally,
however, it is often controlled as a discrete
on/off device. Now engineers need to see it as
an intelligent device that can bring back information,
and control it through a function block
rather than a discrete I/O. Implementing better
energy management is a learning curve, using
logic within the function block to configure
the system and optimise energy usage.
'The goal is to do as much of that process as
automatically as possible, so the programmer
has as little to do as possible,' said Hibbard.
'But it still takes programming effort to get
past the initial learning curve and make the
system work effectively.'
Al Presher is a freelance journalist and US industry