networked energy measurement and control in a natural gas grid

©Svenskt Gastekniskt Center – Augusti 2006

Networked energy measurementand control in a natural gas grid

Rapport SGC A43

Jerker DelsingLuleå Tekniska Universitet, EISLAB

Rapport SGC A43 •1102-7371 • ISRN SGC-R-A43-SE

SGC:s FÖRORD FUD-projekt inom Svenskt Gastekniskt Center AB avrapporteras normalt i rapporter som är fritt tillgängliga för envar intresserad. SGC svarar för utgivningen av rapporterna medan uppdragstagarna för re-spektive projekt eller rapportförfattarna svarar för rapporternas innehåll. Den som utnyttjar eventuella beskrivningar, resultat eller dylikt i rapporterna gör detta helt på eget ansvar. Delar av rapport får återges med angivande av käl-lan. En förteckning över hittills utgivna SGC-rapporter finns på SGC:s hemsida www.sgc.se. Svenskt Gastekniskt Center AB (SGC) är ett samarbetsorgan för företag verksamma inom energigasområdet. Dess främsta uppgift är att samordna och effektivisera intressenternas insatser inom områdena forskning, utveck-ling och demonstration (FUD). SGC har följande delägare: Svenska Gasföreningen, E.ON Gas Sverige AB, E.ON Sverige AB, Göteborg Energi AB, Lunds Energi AB och Öresundskraft AB. Följande parter har gjort det möjligt att genomföra detta utvecklingsprojekt: E.ON Gas Sverige AB E.ON Sverige AB Öresundskraft AB Lunds Energi AB Göteborg Energi AB SVENSKT GASTEKNISKT CENTER AB Jörgen Held Cover picture by R. Johansson from Ref. 6.

Excecutive summary

The application of sensor network technology to gas metering and control in a gas dis-tribution grid is discussed. Introduced by a brief overview of sensor network and sensorfusion ideas two different scenarios for applying networked sensors to gas metering andcontrol are discussed. Possibilities for improved gas metering accuracy and improvedcustomer communication are discussed. Such improvements will possibly result in newcustomer services that can be offered by the gas supplier and better energy efficiency.

Based on this it is proposed a demonstration project. Here sensor networking appliedto gas metering, the resulting services and related ideas will be tested and demonstratedat 10 customers. In addition investigations on customer realtions and future system costand quality will be made. A very rough project cost estimate is 4.75 MSEK.

To further investigate the possibilities of sensor networks in the gas distribution busi-ness also a research project is proposed. The research project will investigate new technol-ogy for estimating data on energy usage and system performance and system daignoses.Furhter architectures for suitable for networked sensors fusion in gas metering will beinvestigated. Project results will possibly provide more cost efficient system maintenanceand improved system energy efficiency. A research project over 3.5 year is cost estimatedto 5.82 MSEK.

1 Background

A currently very hot theme for global re-search is sensor networks. Here sensors aregiven the capability of communication us-ing either wired or wireless technology incombination with very capable protocolslike the Internet suite of protocol namedTCP/IP see for example [1]. In the contextof sensor networks sensor self-diagnostics[2, 3] and system diagnostics [4, 5] can beachieved. In both cases sensor fusion tech-nology is the basis for improved measure-ment accuracy and system performance.

At the same time we see a large changein the energy industry where regulation re-quests individual measurement of electric-ity, gas, heat etc. This has triggered anumber of work on sensor communicationthat already is commercialized. Most of thistechnology is making use of proprietary pro-tocols and communication schemes. Thusmaking interoperability and exchangeabil-ity both hard and expensive.

This forms the incentives for this studyon networked sensing and control in a nat-ural gas grid. This work will sketch twoscenarios with networked sensor in a nat-ural gas grid. One scenario will considernetworking of the sensors involved in form-ing the energy measurement on which thebilling is based. The other scenario will dis-cuss the possibility of networking both thegas energy measurement and the gas usagecontrol system at the customer. Both sce-narios will be applicable to different type ofcustomers like:

• Industry customer

• Heat customer

• Co-generation customer

• Single family household

Based on the two scenarios I do pro-pose a demonstration project and a researchproject regarding:

• Demonstration of networked gas en-ergy measurement a natural gas grid

• Improved measurement and control ina natural gas grid based on sensor fu-sion networks

2 Sensor fusion networks

in energy distribution

In this report the sensor network approachused is based on the Embedded InternetSystem (EIS) architecture [1] where everysensors and actuators in a system can be in-dividually connected to a network using theInternet protocols. This implies that everysensor/actuator will have both computationand memory resources in combination withthe capability of communicating on the In-ternet. The communication capability canbe wired or wireless.

A general illustration of such sensor net-work is given in figure 1. Here data can beexchanged between sensors/actuators thusenabling one sensor to improve its function-ality due to additional information obtainedfrom a nearby sensor. Further sensor fusioncan be made to calculate new data basedon data from a number of involved sensorsand actuators.

Applying the ideas of sensor networks tonatural gas distribution and customer sub-stations is illustrated in figure 2. Here dif-ferent sensors like flow and temperature as

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Sensor fuisonSystem optimization

Figure 1: Principal sketch of a sensor net-work using EIS architecture capable of do-ing sensor fusion.

well as the control devices controling thegas burner can be networked.

The necessary electronics enabling sen-sor networking is not commercial today.Based on university research devices provid-ing the necessary electronics for the sensornetworking capabilites has been developed.Platforms like MULLE [6] provides sen-sor interface, computation and memory re-sources in combination with wireless Blue-tooth communication. Devices like MULLEautomatically builds Internet networks be-tween devices. In figure 3 we see an exampleof a temperature sensor with the necessaryEIS electronics for putting the temperaturesensor wirelessly onto Internet.

Based on the EIS architecture all sensorand actuator including the flow computerand the control system at a customer can benetworked. This will allow for new and us-

Gas meter&

GatewayBurnerTemp

sensorPressuresensor ToTi

Controler

Tvv

Gasanalyser Gas supply

Internet

Figure 2: Principle sketch of sensors andcontrol devices connected in a sensor net-work architecture and its connection to In-ternet.

Figure 3: Standard gas temperature sensorwith EIS electronics

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age of sensor and actuator data. Most pos-sibilities due to this are presently unknown.But taking inspiration from work in the dis-trict heating domain we can speculate inthat removing the wall between the meter-ing system and the control system will openup for a number of interesting improvement.This opens for flow of data from the gas me-ter to the control system opening new pos-sibilities for control and data estimation. Italso opens for data from the control systemto support improvement in the gas measure-ment [4, 5, 7].

In a first development for a gas systemthe following devices and their data can benetworked:

• Flow meter, Q

• Gas temperature

• Gas pressure

• Indoor temperature Ti

• Hot water temperature, Tvv

• Out door temperature, To

• Flow computer

• Control unit

• Heating control system

By local fusioning the data and capa-bilites of these devices new services can bedevised. With reference to work in the dis-trict heating domain it is rather easy toforsee system improvements like [4, 5, 7]:

• Improved gas metering accuracy

• Potentially cheaper installation

• Improved customer behavior feedbackinformation

• Structures for cheap and effortlesschanges of gas distributor

• Simpler and cheaper maintenance

In such an distributed sensing and actu-ating system other issues that have to beaddressed are data security and customerintegrity. Basically each sensor can have anumber of resources for ensuring securityand integrity. Examples are authentication(login), data encryption and action logging.The level of security and integrity should beselected based on the value of the data.

3 Scenarios for net-

worked sensing and

control

We will here sketch two different scenariosfor applying networked sensors in a gas cus-tomer set-up. The first scenario is provid-ing the gas measurement with network ca-pabilites i.e. the flow meter, temperaturesensor and pressure sensor. Further at leastone gas-analyzer in the gas grid will be net-worked. The second scenario is developinga gas installation where both the gas meter-ing and the gas usage control is networkedwith all present sensors and actuators con-nected to the same communication network.

3.1 Scenario I - Networkedgas measurement

In this first scenario the following deviceswill be networked, see figure 4:

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Gas meter BurnerTempsensor

Pressuresensor


Figure 4: Principle sketch of sensors de-vices based on a sensor network architec-ture. This enables simple integration ofinformation from the necessary gas energymetering sensors.

• Gas flow meter

• Temperature sensor

• Pressure sensor

• Gas analyzer

Providing that also some data measuredcentrally like gas composition and heatvalue are made available to the network wecan find a situation like in figure 4. Here thegas meter will act as flow computer and becapable of continously gather data from thetemp and pressure sensors as well as fromthe gas analyzer. Thus being able of cal-culating a more correct amount of energytransfered to the customer.

The case of making gas analysis dataavailable opens for a discussion on whatgas composition is actually present at acustomer. Previously the gas quality wasrather stable based on one single supply.With the inclusion of more local sources like

waste gas and bio gas the gas quality reach-ing a customer can be more problematic todetermine. This will in the future call formore gas analyzers in the network and po-tentially also for cheaper and faster gas ana-lyzers. But making gas analyzers connectedto the same network as the sensors at a cus-tomer will clearly improve the measurementquality at the customer.

For the data exchange between the in-volved devices I will suggest a reactivescheme. This means that the gas flow meterusing a service discovery scheme finds thelocal temperature sensor and pressure sen-sor and the gas analyzer with most appro-priate location for the particular gas meter.From this service discovery the gas meterasks the sensors to provide data to the gasmeter according to a system model sayingthat when temperature data has changedmore than X degrees, send that new valueto the gas flow meter. The same goes forthe pressure sensor and the gas analyzer.The the gas flow meter continously can cal-culate the transfered gas energy accordingto the most appropriate. This can be doneat the sample rate of the flow meter.

Further more the gas meter will makesynchronization checks with all the involvedsensor/analyzers at certain time intervals,say one day to ensure that the sensors arealive.

The only difference for different type ofcustomers are which sensors that are lo-cally available or where data has to be “bor-rowed” from a sensor/analyzer located else-where.

This scheme of possibly borrowing datafrom elsewhere located sensors opens up forreducing the number of pressure and tem-perature sensors in the network. This since

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we probably can find installations that verylikely have the same pressure and tempera-ture situation. In a networked scenario oneinstallation can borrow the pressure andtemperature data from an installation con-sidered having the same operating condi-tion.

Having networked sensors with its own“intelligence” also enable the use of self di-agnostics at each sensor. Meaning that iffor example a temperature sensor can findthat it is providing unreliable data this canbe notified to the gas meter and of coursethe maintenance organization. The gas me-ter can then try to find another temperaturesensor within the service discovery lookupscheme available for the gas meter.

This enables for a new approach to main-tenance where a broken temperature sensorfirst can be identified secondly can be ex-changed in a planed manner provided thatthe gas meter can find another source forthe temperature data.

3.1.1 Customer relations

All data from the sensors are in a networkedparadigm available to anybody having au-thority to access data. This opens up forgiving data to customers enabling customerfeedback. A total wide open unprocesseddata feedback to the customer is probablyunwise. The feedback should probably beprocessed in a way providing potentially anindividual feedback to the customer. Thusopening up a possibility for making new ser-vices with an economic value to the cus-tomer. This provides a foundation for newbusiness relationships with the customer.

Examples of possible feedback are:

• Energy usage pattern

• Possibility to correlate energy cost tocustomer behavior

• Predictions of energy cost based pro-duction scenarios.

A customer will in the future be ableto change gas supplier. This calls for newmethods providing easy transition of “ovn-ership” of gas metering data. There areseveral possible technology approaches forthis. One approach is having an authentica-tion routine enabling a new “owner” of datato login to the gas metering webserver andaquire the ownership and thus change pass-words etc. of the gas metering webserver.Another approach is making use of SIMcard technology from the telcom business.Here a number of such “ovnership” trans-actions have been solved in a way which isaccepted by the telecom market. This ap-proach is interesting provided that a GPRScommunication technology is used. Thusalso the billing can be made over the phonebill. In this case telecom operators hsa tobe involved in the process.

3.2 Scenario II - Networkedgas measurement and con-trol

In this second scenario both the gas me-tering devices as well as all devices neces-sary for the control of energy usage will benetworked. For a heating application in alarger building the following devices will benetworked see figure 5:

• Gas flow meter

• Temperature senator

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Pressuresensor ToTi

Controler

Tvv


The important difference

Figure 5: Principle sketch of sensors andcontrol devices based on a sensor networkarchitecture. This enables simple integra-tion of information from the the heat me-tering and the control system.

• Pressure sensor

• Gas analyzer

• Burner control

• Indoor temperature

• Hot water temperature

• Out door temperature

It is obvious that for other applicationsother sensors and actuator devices will beof interest to network.

In addition to the functionality for sce-nario I we can see more possibilities whenmore data is made available. For examplecan data from the customer side i.e. pro-cess demand data, heat demand data etcinfluences the controling of the gas burner.The control signal to the burner can be uti-lized by the gas meter to change for examplethe sampling rate (at least for ultrasonic gas

meters) and thus provide more accurate gasmetering [4].

Other opportunities are improved heatutilization based on accurate knowledge ofthe gas heat value. In such a situation theburner control is asking for the start of en-ergy usage at a certain level. By knowingthe heat value of the gas the burner con-trol can adjust the burner operation to meetthe demand with a faster response than notknowing the current gas heat value.

Looking at work done in district heating,see for example [5], it is also expected thata better understanding of the system andits parts will enable system and part diag-nostics using the gas metering data possi-bly in combination with data from the con-trol system. The fact that alla data will be“available” to different parts of the largersystem will enable new possibilities for sys-tem maintenance.

Further energy usage predictions can bemore accurate providing new tools and pos-sibilities for spot market business. Wherean accurate prediction of gas usage can pro-vide valuable information for purchase ofenergy on a spot gas market.

Obviously if more to customer and sup-plier relevant data can be extracted fromthe already present sensors and presentedin a feasible way more efficient use of en-ergy can be made.

I expect more possibilities to be found inthe future. Here research possibly will pro-vide new ways of extracting new informa-tion as indicated above The way to investi-gate such possibilities is a research project.I do sketch such a research project below.

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4 Project proposals

I here propose two different projects. Thefirst is for demonstrating gas measurementbased on scenario I above. The secondproject proposal covers research on systemunderstanding based on availability of sen-sor data from both gas metering and thecustomer process accoring to senario II..

4.1 Development and demon-stration of networked gasmetering system

4.1.1 Objectives

The project objectives are:

• Demonstrate networked gas meteringfor at least 10 customers

• Develop networked gas metering onavailable and proven sensor technology

• Investigate ways of changing gas sup-plier and billing practise

• Develop gas provider and customer in-formation tools.

• Analyze a test period run of at least 12months operation

4.1.2 Project description - Net-worked

Currently to my knowledge no commercialgas metering technology is available capa-ble of the two scenarios described above.For the purpose of demonstration technol-ogy like Webmaster from Abelko InnovationAB (http://www.abelko.se/) can be used.Webmaster has a built in web server and

sufficient sensor inputs. Webmaster canconnect to the Internet using either Ether-net or GPRS communication. Webmasteris programmable thus an application canbe developed doing both the data genera-tion as well as provide data communicationusing the built in web server.


Pressuresensor

Webmaster


Pressuresensor

Webmaster


Pressuresensor

Webmaster


Webmaster


Pressuresensor

Webmaster

Internet

Figure 6: Demonstration system based onone Webmaster at each customer and oneat the gas analyzer site.

Webmaster can be applied as indicatedin figure 6. Here one Webmaster is used ateach customer participating in the demon-stration plus one at a feasible gas analyzer.The customer Webmasters does read datafrom the gas meter, temperature sensor andpressure sensor. Based on that data plusdata from the gas analyzer the gas con-sumption is calculated. Gas analyzer datais updated at each customer Webmaster ina reactive way. Thus the Webmaster willact as a flow computer. An application forWebmaster has to be developed to accom-plish these tasks.

Data presentation for both the gas sup-plier and the gas customer has to be devel-oped. An important task of the project is

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to define a number of interesting data ser-vice scenarios for both gas suppliers and gascustomers.

Based on such a development at least10 selected customer installations will beequipped with Webmasters. The num-bers of installations is mostly an economicalquestion. This demonstration will then runfor at least 12 months during which the dif-ferent data services will be tested and eval-uated. More demonstration installation canbe added to the extra cost of hardware andlabor

I do see four major project phases withthe following major project tasks:

1. Demonstrator development

(a) General system and services de-sign

(b) Development of applications inWebmaster for data reading, gasenergy computing and data ser-vices

(c) Develop data services suitable forgas suppliers and different gascustomers

2. Technology investigations

(a) Investigate different technologysolutions for changes of gas sup-plier

(b) Investigate system requirementsand cost based on future technol-ogy like MULLE microwebservers

(c) Investigate and develop qualityassurance routines for sensor net-worked systems

3. Demonstration

(a) Selection of customers

(b) Installation and start-up

(c) Demonstration run for 12 monthswith 10 customers

4. Evaluation and documentation

(a) Evaluation system benefits to gasprovider and gas customer

(b) Documentation and reporting

It is expected that the development phaseis 6 months, the demonstration phase is 14months and evaluation and documentationphase is another 3 months

In table 1 a very indicative budget is pro-vided. The budget is based on 2 man yearin development, 1 man year in technologyinvestigations, 0.5 man year in demonstra-tion and 0.75 man year for evaluation anddocumentation. In addition to this 500.000is needed for equipment provided that ex-isting sensor equipments like flow meters,temperature sensors, pressure sensors andgas analyzers can be used.

Adding more demonstration installationswill add 400.000 per 10 more installationsplus additional 10

Task SEKDemonstrator development 2.000.000Technology investigations 1.000.000Demonstration 1.000.000Evaluation and report 750.000Total cost 4.750.000

Table 1: Very indicative project budget

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4.2 Networked gas meteringand control system

This project is targeting research on tech-nology for more efficient energy usage in aenergy gas customer - supplier relationship.

4.2.1 Objectives

The project objectives are:

• Development of a simulation model en-abling investigation of gas usage sys-tem optimization

• Investigate networked gas meteringcontrol methodologies targeting im-proved measurement and control qual-ity and customer feedback possibilities

• Demonstrated gas metering and con-trol methodologies in lab environment

• Investigate secure Internet technologyfor sensor localisation, identificationservie provison

4.2.2 Project description - Net-worked gas metering and con-trol system

To enable a system investigation of a gassupply installation at a customer modelingis the most appropriate approach. For thepurpose a matlab model will be developedmodeling a gas usage installation compris-ing at least parts like gas burner, gas meter-ing, control devices, energy use like househeating, etc. according to scenario II above.

This simulation and modeling environ-ment will then used to investigate new ap-proaches to:

• Improved gas metering accuracy

• Sensor fusion approaches to gas us-age control targeting higher energy ef-ficency

• Sensor fusion approaches targeting rel-evant energy usage measures that whenused in a customer/supplier feedbackcan improve total energy efficiency.

The sensor fusion approach will make useof control information at the energy useside to improve the gas metering. Hereadvanced knowledge of process status bythe customer will provide more informationthat can be used for improving the gas me-tering accuracy. This information can alsobe used for improving the gas burner effi-ciency as well as energy distribution fromthe burner.

Based on findings using the simulationtool a physical demonstration of results willbe made under lab conditions. This will bemade using todays most advanced EIS tech-nology, the MULLE platform. Thus the ap-propriate sensors and actuators will be con-nected in a network providing the frame-work for using sensor fusion within the net-worked sensors/actuators.

The following main tasks is needed insuch a research project:

• Simulation model development

• Gas metering accuracy optimization

• Sensor fusion for improved gas usagecontrol

• Sensor fusion including cus-tomer/supplier feedback for improvedtotal energy efficiency

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• Networked sensor architecture provid-ing localisation, identification and ser-vice provision architecture.

• Demonstration of sensor fusion on anadvanced sensor network technology

• Result dissemination

Result dissemination will be made usingstandard scientific publication as well asdedicated seminars for national gas indus-try.

Designing the project as a researchproject with a PhD. student and one se-nior scientist as major resources we projecta total project time of 3.5 years. This willin addition to the project objectives enablethe student to obtain a PhD.

In table 2 a very indicative budget is pro-vided. The budget is based on 1.5 PhD stu-dent and one senior scientist at 35% over3.5 years. year in development and 0.5 manyear in demonstration and a quarter manyear for evaluation and documentation. Inaddition to this 250.000 is needed for equip-ment provided that existing sensor equip-ments like flow meters, temperature sen-sors, pressure sensors and gas analyzers canbe used.

Cost KSEKPhD student 3.5 year 3.900Senior scientist 25% 1.370Lab and equipment 300Travel and expenses 250Total cost 5.820

Table 2: Very indicative research projectbudget

References

[1] J. Delsing and P. Lindgren, Sen-sor communication technology towardsambient intelligence, a review, Mea-surement Science and Technology, In-stitute of Physics, 16, 2005, pp.37-46,http://stacks.iop.org/MST/16/37

[2] C. Carlander, Installation effects andself diagnostics for ultrasonic flow mea-surement, PhD Thesis, Lule Univer-sity of Technology, Sweden, ISSN 1402-1544 / ISRN LTU-DT–01/11–SE / NR2001:11, Mars 2001

[3] J. Berrebi, Self-Diagnostic Techniquesand Their Application to Error Re-duction for ultrasonic flow measure-ment, PhD Thesis Lule Universityof Technology, Sweden, ISSN 1402-1544 / ISRN LTU-DT–04/23–SE / NR2004:23, June 2004

[4] Y. Jomni, J. van Deventer and J. Dels-ing, Improving heat energy measure-ment in district heating substationsusing an adaptive algorithm, Proc.Flomeko-2004, pp. 554-558, 2004.

[5] K. Yliniemi, Fault detection is districtheating substations, licentiate thesis,Lule University of Technology, ISSN1402-1757 / ISRN LTU-LIC–05/60–SE/ NR 2005:60, Dec. 2005.

[6] J. Johansson, M. Vlker, J. Eliasson,. stmark, P. Lindgren, J. Delsing,MULLE: A Minimal Sensor Network-ing Device - Implementation and Man-ufacturing Challenges, Proc. IMAPSNordic 2004.

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[7] Y. Jomni, K. Yliniemi, J. van De-venter, J. Delsing, Improving heatenergy measurement using a Feed-Forward method for low power applica-tions; Proc District Heating and Cool-ing Symposium, 2004.

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networked energy measurement and control in a natural gas grid

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