End users must be tired of instrument manufacturers referring to Lord Kelvin’s famous quote and advising that unless you measure the flow of a utilityyou cannot manage it.
Obviouslyend users are fully aware of this but often find it difficult to justify buying more meters.
Unfortunatelyflowmeters don't save energy or moneythey merely provide measurement data. It is what is done with the data that is important.
For decadesEndress+Hauser has supplied utility meters on a wide range of duties including steamcompressed airnatural gascarbon dioxidenitrogen and water.
Howeverthe data provided by these meters is usually totalised and trended at best. Without data analysis tools it is difficult to determine the energy efficiency of a process.
Having the tools to justify capital project expenditure in order to implement energy saving measures is key.
In a modern energy management system there are three components: meters providing the datadata collection devicesand software analysing the data (Fig.1).
Utility meters
The first step is the selection of suitable utility meters. There are many pitfalls at this stageincluding volume meters inferring mass consumptionmeters installed incorrectly and meters oversized due to confusion over normalstandardfree air delivered or actual volume units.
The next two components are data collection and analysiswhich is more commonly termed monitoring and targeting (M&T). M&T is a powerful energy management technique which has been re-invented over the last few years for use in automatic half-hourly electricity metering. The analysis techniques within M&T have been around for many years.
Howeveradvances in web-enabled software solutionsremote data collection devices and increased energy prices are raising the profile of M&T.
Commitment
There are many reasons why companies should reduce energy consumptionbut obtaining commitment to do so remains difficult.
Although companies are being taxed on their energy consumption and the topic
of climate change and Africa topped the
G8 summit meeting agenda at Gleneagles recentlyit is still difficult to justify capital expenditure when there is little resource to identifyevaluate and implement energy efficiency opportunities.
Howeverthere has never been a better time to implement energy saving measures. Human nature dictates that the rising cost of electricity and gas is the driving force behind some companies finally looking at climate change issues.
Ormore realisticallyit is forcing companies to do something about rising energy costs to remain competitive.
The only way to do this of course is to reduce energy consumption. For many companiesidentifying energy intensive processes such as steam and compressed air is a good start.
Generating steam and hot water accounts
for 40percent of fossil fuels used in industry and compressing air accounts for 10percent of electricity.
Therefore improving energy efficiency in processes using these utilities is an obvious way of reducing a utility bill.
Improving the fuel to steam efficiency when generating steam saves on average seven per cent in fuelbut before replacement energy efficient boilers are purchased or economisers and oxygen trim controls added to existing older boilersa business case must be made for the likely return on any investment.
Installing gassteam and condensate return meters with an automatic data collection device is relatively inexpensive and will soon provide information on the fuel to steam efficiency. This value will indicate the potential for energy savings.
By conducting an input-output analysis for the fuel energy input to the boiler and steam generateda relationship can easily be obtained for the amount of energy it takes to produce a kilogramme of steam.
Specific energy consumption
Specific energy consumption (SEC) is a useful energy efficiency tool which allows comparisons or bench marking with similar processes in similar industry sectors.
Monthly energy consumption plotted over a year may indicate how much energy has been used and the associated costs of electricity and fuel each month. It does nothoweverindicate if performance was goodpoor or indifferent.
Correlating the energy consumption to a driver influencing it is much more meaningful. The influencing factor in energy consumption could be production such as litres of beer or metres of carpet. It could be degree days or a measure of the outside ambient temperatureor it could be another utility such as watersteam or compressed air.
Correlating electrical energy to compressed air demand or compressed air to production can provide a measure of how efficient a process is.
Whatever the utilitythe process is the same. The consumption of a particular utility will be driven by an influencing factor.
Many of the relationships derived from an input-output analysis approximate a straight line and can be considered linear.
By collecting data over a period of timerelationships can be derived for previous energy consumption.
Thereforea target for future consumption is readily available providing a comparison of performance to the standardised norm or target.
From this comparison we can determine if performance is pooraverage or good.
Exception reports
If energy consumption rises above a predetermined levelalarms can be set so that exception reports are initiatedinforming personnel in a particular part of the plant. This process allows waste to be identified quickly and therefore eliminated. It could act as a form of condition monitoring providing information on deterioration in plant such as boiler controls or compressors and therefore enable predictive maintenance.
By having a target to measure consumption against energy efficiencyimprovements can be implemented and the cumulative sum of energy savings calculated each week.
Staff motivation
As well as providing a measure of the return on investment for the projectit provides motivation to all staff to continue the cycle of energy efficiency.
Energy savings can be made even without the need for capital equipment. Identifying waste through leaks is one of the easiest ways of saving energy in compressed air systems. It is not unusual to find leaks accounting for 30percent of the demand.
Monitoring and targeting compressed air using sub-meters in plant areas of high demand can easily identify waste.
Insertion meters can be installed under pressure using special hot-tap techniques and pipe clamps avoiding the need to switch off compressors and stop production.
Once leaks are identifiedtagged and fixedsavings can again be measured. M&T is a continuous process and so as improvements are implemented and energy efficiencies are improvednew targets can be set. At the same time new sources of waste will be detected such as wear to machinery or more leaks.
It has already been said that analysis of the data is only as good as the measurements made to obtain the data. In many instances repeatability will be more important than accuracy.
Howeverusing the wrong techniqueno matter how accuratecould lead to poor repeatability. For examplea vortex meter used on compressed air or steam without pressure and temperature compensation may vary by ±10percent when the demand is the same.
Reliable accurate data is important if used to collect carbon emission data for the European Union Emissions Trading Scheme (EUETS). This data must be verified by an external agency.
Thereforethe meter must be traceableaccurate and the energy management software collecting the data must also compute carbon correctly and in a secure way.
There are obviously extra benefits to having created a consistent approach to the data collection. Not only will the data be easier to verify by an external agencyadditional meters can be added from various manufacturers if the system architecture is open and not proprietary.
Having an open architecture means that the network does not have to exist just to support an energy management solution.
The same network could support further applications such as asset management.
Diagnostic information can be made available from the meters and in-situ verification tools can be used to extend any recalibration period without the need for removing meters from the pipe. This is particularly beneficial for a steam line where meter removal is often not an option.
Data collection
Data collection from Fieldgate devices can be stored in a history databaseexported to files such as flat files (*.csv)database files (*.mdb)OPC server and SQL. This allows integration with standard office software like Microsoft Excel or AccessSupervisory Control and Data Acquisition (SCADA)WonderwareiFIX IntellutionWinCC and others – plus Endress+Hauser SCADA packages such as PView.
Fieldgate Data Access software can gather data from many Fieldgates automaticallyand allows integration into web-enabled energy management (M&T) software packages.
Increased environmental regulations and EU directives mean that today’s safety health and environment (SHE) or energy managers have more responsibility than everbut less time to implement energy efficient measures.
Manual meter readings should be an activity of the past. Many affordable data collection devices exist. From simple paperless recorders and data managers to Fieldgates and low-cost SCADA which will collect data as often as required in a format that can be exported into Excel.
Once in Exceldata can be manipulated and analysed by energy managers who prefer their own macro-driven spreadsheetsto packaged software solutions.
Electronic reports
Howeverfor energy managers wanting a system to automatically collect data from all utilitiesprovide comprehensive energy analysis and create electronic reports customised and tailored to the organisationaffordable automatic M&T solutions exist.
Improving energy efficiency is often the quickest and easiest way of improving the bottom line and an average of 5–15percent savings can be made with very little or low cost measures when adopting an M&T system.
Wes Allen is Product Specialist with Endress+Hauser LtdFloats RoadManchesterM23 9NFEnglandtel 44 161 286 5000direct line 44 161 286 5032fax 44 161 998 1841
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