monitoring energy efficiency in w.a.g.e.s/utilities …...monitoring energy efficiency in...
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Monitoring Energy Efficiency in W.A.G.E.S/Utilities for reducing cost Dipl.-Hyd. Oliver Seifert, Endress + Hauser Flowtec AG, CH-4153 Reinach BL 1. Introduction Our customers in all industries are coming more and more under pressure to measure the
cost of their utilities:
- Water
- Air
- Gas (e.g. Natural Gas, other gases or fuels)
- Electricity and
- Steam
It is interesting to confirm that this trend is independent of the industry. We can see it in small
breweries and in big chemical parks.
These utilities are the life-blood of the industry: they are crucial in order to manufacture.
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Raw Materials
Labour
Wat
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Air
Gas
Elec
tric
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Stea
m
Products
Emis
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s/Ef
fluen
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Wat
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Air
Gas
Elec
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Stea
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Fig. 1: The Production Process in Industry. The utilities/W.A.G.E.S. play a vital role in order
to convert raw materials into products during the manufacturing process.
One important driver for this pressure is the ever increasing cost of energy. The cost of
natural gas for industrial applications has more than tripled within the last ten years and the
price for electricity in Europe has risen by 30% within the previous 4 years.
Another driver are certifications according to EMAS and the ISO 14000 series that force
customers to measure the energy streams using calibrated technology.
The utilities have frequently been neglected in the past, however, they are coming more and
more into focus. The cost drivers for all industries are:
- Capital Cost
- Labour Cost
- Raw Material Cost and
- Energy Cost.
Of these, Energy Costs are the only point can readily be influenced.
Many companies still only measure natural gas and electricity only at the custody transfer
point. Using these few measurements, however, important parameters like specific energy
consumptions are determined that give important indications such as how much energy does
it take to make a tonne of product? These measurements are typically only taken on a
monthly or sometimes even on a yearly basis. Investing a relatively small amount of money
in comparative terms it is possible to set up energy monitoring systems that measure the
consumption of each respective utility close to the point of use every 15 or 30 minuntes.
These measurements can then be used to build meaningful relations between energy
consumption and the factors driving it that enable the customer to
- Gain transparency over their energy consumption
- Identify and justify energy reduction projects (Where is most energy consumed?
Which changes are possible?)
- Detect poor performance earlier (are the boiler’s heating surfaces fouling?)
- Provide support for decision making (Should the contract with the provider of
electricity be changed?)
- Report performance automically (Which Energy Accountability Centre/shift etc. is
performing best? Did exceptions occur?)
- Audit historical operations
- Provide evidence of success (Did promises made by a manufacturer of energy
efficient equipment come true? Calculation of Return on Investment ROI)
- Provide support for energy budgeting and management accounting
- Provide the energy data to other systems (e.g. exisiting SCADA)
- Reduce their energy consumption
2. What is Energy Management?
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DataCollection
Energy Analyses
Energy Reporting
Optimize
Controlling ofEnergy Data
Transparency of Consumption
Customer
Fig. 2: The Energy Management Cycle. It consists of data collection, data analyses,
communication of the results (reporting) and „taking the action“ to reduce the energy
consumption based on the findings. The first three steps of „Energy Management“ are called
„Energy Monitoring“.
2.1 Data Collection
Energy Management can be seen as a cyclic operation. Data collection is the bases of all
energy monitoring, energy management and therefore energy savings.The energy
consumption is measured and converted to appropriate units. For most of the utilities, these
conversions require close scrutiny and understanding:
- the conversion from volumetric units (e.g. natural gas measured by turbines, steam
measured by DP devices or vortex meters) to corrected volume, mass or energy
often is done in a wrong way resulting in errors in the range of typically 10…30%
- many devices are mis-installed resulting in similar error ranges and
- if the basis is wrong, the analysis will be wrong and all action taken will be at best
misleading.
The simplest way of data collection remains, even today, paper and pencil and it is amazing
to see how many people in the industry still have to walk around the factory and find certain
meters on a monthly basis to take the readings. Modern recorders as stand-alone devices or
so-called „software recorders“ are able to record data in typically 15 or 30 minutes intervals.
If these intervals are not sufficient, even a data collection every 100ms is possible but this is
more common in Process Control.
Most modern systems of data collection are even able to collect the data of up to 30 devices
using bus communication and pass the data on using „Field Gates“.
Manual reading of electricitymeters
Semi-automatic collection usingUSB stick
Automatic data collection usingFieldGate FXA520 HART
Fig. 3: Types of Data Collection ranging from manual, semi-automatic e.g. using a recorder
to automatic data collection using FieldGates
2.2 Data Analysis
If the Data collection is the basis of it all, data analysis is the heart as it helps to convert the
pure measurements of energy signals into meaningful data.
A first basic analysis consists in looking at the 15-min or 30-min data profiles:
- What is the base-load of the application? Why is energy still consumed without
production? How can this base-load be reduced?
- What is the typical maximum load during productive hours? How can the maximum
load be reduced? (This is important e.g. for electricity contracts)
- What is the typical load distribution? How can a more uniform load-distribution be
obtained? For this purpose, different policies of load-management are available (e.g.
peak-clipping)
A more powerful analysis consists in putting energy consumptions in relation to a driving
factor. Examples are:
- how much heating energy is consumed compared to how cold the weather is (so-
called degree days)
- how much energy is consumed to make a tonne of product
- how much electricity is consumed in order to light a building compared to the hours of
day-light.
Once we have associated an energy consumptions with a relevant drivers, they are
generally called „Specific Energy Consumptions“ SEC.
Controlling such a factor now enables the user to control a individual process should it be found to drift over time, i.e. the process is becoming more inefficient. Possible causes of such a drift could be:
- the amount of leakage in a compressed air grid is growing due to lack of effective
maintenance
- the specific energy consumption for making steam is rising due to ineffective
maintenance of steam traps (steam traps fail open in case of a failure)
- the specific energy consumption for heating a building rises due to fouling of the
surfaces of heat-exchangers
Generally, comparing the energy consumption with a driver will reveal a linear relationship. In
certain applications this linear relationship also shows an intercept that does not equal zero.
If no actions are taken, the trend will be as follows:
- the intercept grows (examples: increasing leakage in a compressed air application or
failing steam traps)
- the slope of the linear relationship grows (loss of efficiency e.g. because of fouling
heat-exchangers)
Customers, however, should strive to
- reduce the intercept and
- reduce the slope of the linear relationship.
The linear relationship can be used as a target for the future. If, for example in the past it
took 4 GJ of energy to make a tonne of steam then we can expect this same value for the
future unless we take actions to improve efficiency.
We can now compare the real energy consumption to the expected one and record the
differences. If this difference exceeds a predetermined value, a warning will could generated.
Fig. 4: The Control Graph for controlling deviations from a pre-set target. If the control limits
are exceeded, an alarm can be generated.
We can also take these differences and total them up over time in the so-called CUSUM
(cumulated sums) chart.
Fig. 5: The CUSUM chart. It acts as a totalizer and can reveal savings achieved.
This chart acts like a bank-account; if the process becomes less efficient, the CUSUM trend
will diverge from the zero line as in Fig.5 where the process has become more efficient. In
our example an economizer was installed improving a steam boiler’s efficiency. Compared to
the systems former performance an investment into the economizer saved the company
1100 MWh of energy over 15 weeks. Therefore, the CUSUM gives a direct indication of the
Return on Investment for Energy Savings Measures.
Performing the Analyses will enable customers to ask and answer at least the following
questions:
- Where is the energy in general going? How many emissions are created?
- Which energy accountability centers are consuming most energy? Which areas are
working the most efficient and why?
- Why are certain shifts more efficient than other?
- Which machines/boilers/motors etc. are most efficient? Can you switch from the
current main boiler to a more efficient boiler?
- Why was the specific energy consumption stable for months but started drifting
recently? (e.g. fouling of boilers)
- Is energy consumed during non-productive hours? Can this amount be reduced in the
future?
- When do peak loads occur and how can they be avoided?
- Is currently the most economic tariff purchased or are there cheaper alternatives?
- Where is the biggest potential for investing into more environmental friendly
technologies?
- Are changes in performance observable? Are boilers fouling?
- Do exceptions from predefined target values occur?
2.3 Communication/Reporting
Recipients of Energy reports can be separated into different hierarchies: from operations
personnel to top management and in different areas of a company
(production/operation/engineering, controlling, energy and eco management).
Management
ControllingOperation/Maintenance/Engineering
Environmental andEcological Manager
Fig. 7: Typical recipients of Energy reporting
The reports must provide information to enable the user to act. Operational staff needs to
know when a problem has occurred as quickly as possible and know what they should do
about it. Senior management, on the other hand, need summary information to know that
procedures and systems are working well. In order to design reports, it is important to
understand who needs what and why.
Reports to senior managment might include
- a summary of last year’s costs, broken down into EACs (energy accountable centers)
- a summary of the current year’s performance on a monthly basis
o against budget
o against the previous year
o against targets
- a note of the savings (or losses) achieved to date and how they were achieved
- a note of additional savings opportunities and what actions are ongoing to address
them
A new report to management should be issued each month and be available in time for
board meetings.
Operations management will be responsible for operating processes and plant efficiency.
They will need to know on a shift, daily, weekly or monthly basis (depending on the nature of
the process and the level of energy use) what energy has been used and how this compares
with various targets. The information will be used to
- measure and manage the effectiveness of operations personnel and process plant
and systems
- identify problem areas quickly
- provide a basis for performance reporting (to executives)
Operations personnel need to know when a problem has occurred and what needs to be
done to rectify it. This information needs to be provided in a timely manner, which might
mean within a few minutes of the event for a major energy-using process, or within a day or a
week.
Engineers associated with operations will need reports similar to those for operations
personnel. Engineers may typically be involved with problems where there is more time to
act (compared with process operators), for example, cleaning heat exchangers, solving a
control problem or removing air from a refrigeration condenser.
Engineers who are not directly in operations but who provide support will need more detailed
historical information. Typically, these individuals will be involved in analysing historical
performance, developing targets and modelling. They will require access to the plant data
historian and will use analysis tools, ranging from commonly available spreadsheet software
to advanced data mining and similar software.
Engineers that are involved in projects will need supporting data, for example, levels of
energy use, process operating conditions, etc. They will also need access to the raw data in
the historian and access to analysis tools.
The accounts department may be interested in actual energy usages and costs to compare
with budgets. They will need information that is broken down by department so that costs can
be allocated to related activities. Accurate costing of operations and the cost of producing
goods can improve decisions regarding product pricing, for example, and the allocation of
resources.
Energy and environmental managers will need summary data that identifies the performance
achieved and trends, much like executives and operations managers require. Like engineers,
they may require more detailed information for specific analysis.
The environmental department may want energy consumption expressed as equivalent CO2
emissions, and the energy reports may need to be integrated into environmental reports that
are more general. Summary information may be required for annual energy and
environmental reporting and may be needed more frequently by regulatory bodies.
The energy manager may be involved in energy purchasing as well as efficiency. He may
need information about the profile of energy use (using a half-hourly graph, for example),
peak usage, night-time usage, etc. The energy manager will also need access to the raw
data in order to allow evaluation of purchasing options and checking of bills.
We can see from this broad variety of requirements that modern Energy Management
Information Systems have to be very flexible in creating effective reports.
2.4 Taking Action
Results of implementing Energy Monitoring Informations Systems in the UK indicate that,
when properly implemeted, such a system can save 5 to 15 percent of annual energy costs.
As an initial approximation, 8 percent appears to be a reasonable estimate. [1]
Implementing an Energy Management Information System and taking the action based on
the outcome of this tool alone will result typically in 8 percent savings. Most experience
regarding this tooling can be found in the UK based on the local “Carbon Trust”.
Further savings can be achieved by spending capital cost e.g. for more efficient burners and
boilers, economizers etc.
Savings Strategies in Energy Management typically fall into the four following categories:
• Eliminate. Generally, one should question if certain processes or sections of a
plant are really required or if they could be replaced. A simple example:
eliminating dead legs of a plant.
• Combine. CHP is a well-known “combine” process: generation of heat and
electricity are combined. Another example is the use of off-heat created by air
compressors e.g. for pre-heating factory air. Oliver I am not sure about this, do
you mean hot air conditioning for offices?
• Change equipment, person, place, or sequence. Equipment changes can offer
substantial energy savings as the newer equipment may be more energy efficient.
Changing persons, place, or sequences can offer energy savings as the person
may be more skillful, the place more appropriate, and the sequence better in
terms of energy consumption. For example, bringing rework back to the person
with the skill and to the place with the correct equipment can save energy.
• Improve. Most energy management work today involves improvement in how
energy is used in the process because the capital expenditure required is often
minimized. Examples include reducing excess air for combustion to a minimum,
reducing temperatures to the minimum required. Improvement does sometimes
require large amounts of capital. For example, insulation improvements can be
expensive, but energy savings can be large, and there can be improved product
quality.
2.5 Energy Monitoring Solutions
Modern recorders already offer solutions for monitoring boilers or compressed air grids. They
are not only able to monitor flow or other parameters, they can also be used for calculating
and visualizing energy, emissions, specific energy consumption, efficiencies etc. Alarms can
be initiated in case violations of pre-defined values occur.
Nat gas[MJ/ h]
Steam[MJ/ h]
Condensate return
Feed waterTR10 (HART)
Flue gas
BlowdownAir
FuelFuel
FeedwaterFeedwaterSteamSteam
hmhmhmEfficiency
⋅⋅−⋅
=η:
Memograph M(Math)
2xRN221N
Fig. 6: Energy Monitoring solution of a boiler using a recorder. Energy, efficiency (fuel to
steam), emissions and specific energy consumption are calculated in the recorder.
For monitoring the energy consumption of a complete company and multi-site companies
Energy Monitoring Software solutions are the solution of choice. As an example, existing
mains meters and electricity meters provide their information through a pulsed output to the
system. For multivariable flowmeters a bus like the HART protocol is used to make use of the
wealth of information available from these devices. These data are then passed through
FieldGates to the company’s Ethernet and are collected every 15 to 30 minutes through a
data collection software. This software creates .csv files that then are made available to an
existing SCADA and to the Energy Monitoring Software. This software will then visualize the
data, analyze them and automatically create reports. Targets as explained above can be
defined, deviations from the targets identified and return on investment of energy savings
measures calculated. The software should be web-based to enable the customer accessing
his data globally from any computer. Additionally, web-based solutions are ideal for multi-site
companies.
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FXZ520Module
4x Pulse
GSM/ GPRS
ExistingVisualization/SCADA
Energy MonitoringSoftware
ExistingProduction data
Ethernet
Database
Data Access Scheduler
Client server
Software for ½ hourly datacollection
FieldgateFXA520RS485
HART-Multiplexer
RS485FieldgateFXA520
PLCField ControllerSFC173
EneryManagerRMx621
Memograph M
Fig. 7: Set-up of a typical full-blown Energy Monitoring Information System. Data are
collected from existing meters or electricity meters with pulsed output and multivariable
flowmeters using HART communication or from recorders and flow computers. This data
collection typically is done every 15 to 30 minutes. The data is visualized, analyzed and
reported by the Energy Monitoring Software.
These solutions enable the customer to
- gain transparency over their energy consumption and emissions
- identify potential areas of savings
- follow indicators like specific energy consumption
- save time through the automatic data collection, data analysis and creation of reports
- reduce energy consumption and therefore emissions typically by 5 to 15 % (according
to the British Carbon Trust and the Canadian CIPEC)
Literature [1] Office of Energy Efficiency of Natural Resources Canada: Energy management
information systems: achieving improved energy efficiency: a handbook for managers,
engineers and operational staff.