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European Research Infrastructure supportingSmart Grid Systems Technology Development,

Validation and Roll Out

Technical Report TA User Project

Eval-loggers

Grant Agreement No: 654113Funding Instrument: Research and Innovation Actions (RIA) – Integrating Activity (IA)

Funded under: INFRAIA-1-2014/2015: Integrating and opening existing nationaland regional research infrastructures of European interest

Starting date of project: 01.11.2015Project Duration: 54 monthContractual delivery date: 31/10/15Actual delivery date: 31/10/15Name of lead beneficiaryfor this deliverable: Luiz Fernando Lavado Villa – LAAS-CNRS

Deliverable Type: Report(R)Security Class: Public (PU)Revision / Status: draft

Project co-funded by the European Commission within the H2020 Programme (2014-2020)

ERIGrid GA No: 654113 February 7, 2018

Document Information

Document Version: 1Revision/Status: draftAll Authors/Partners Luiz Fernando Lavado Villa/LAAS-CNRS

Gilles Longuet/TripaliumMatthew Little/Re-InnovationNasos Avasilakis/ICCS-NTUA

Document History

Revision Content/Changes Resp. Partner DateRevisionNumber 1 Final version with all figure and text Luiz Villa 22.11.17

RevisionNumber 2

Approved version with modificationsand license Luiz Villa 06.11.18

RevisionNumber

Short description of the documentchanges Partner Short name DD.MM.YY

Document Approval

Final Approval Name Resp. Partner DateReview Task Level Given Name + Name Partner Short name DD.MM.YYReview WP Level Given Name + Name Partner Short name DD.MM.YYReview Steering Com.Level Given Name + Name Partner Short name DD.MM.YY

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TA User Project: Eval-loggers Revision/Status: draft 2of 31


ContentsExecutive Summary 4

1 General Information fo the User Project 51.1 Host Insfrastructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.2 User Group Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.3 The schedule for the two weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2 Research Motivation 82.1 The objectives of the project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.2 Scope of the project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3 State-of-the-art 93.1 The dataloggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4 Experimental work 114.1 Test plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114.2 Standards, Procedures and Methodology . . . . . . . . . . . . . . . . . . . . . . . . 114.3 Test setups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.3.1 Setup I - Perfect DC source . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.3.2 Experiment II - Perfect AC source . . . . . . . . . . . . . . . . . . . . . . . 124.3.3 Experiment III - Perfect AC source with diode bridge . . . . . . . . . . . . 134.3.4 Experiment IV - Laboratory Controlled Generator . . . . . . . . . . . . . . 144.3.5 Setup V - Rafina Test site . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

5 Results and Conclusions 165.1 Experimental results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5.1.1 Setup I - DC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165.1.2 Setup II - AC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175.1.3 Setup III - AC/DC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185.1.4 Setup IV - AC/DC Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195.1.5 Setup V - Rafina Test site . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225.1.6 Summary of experimental results . . . . . . . . . . . . . . . . . . . . . . . . 24

5.2 Low-Cost Callibration of the datalogger . . . . . . . . . . . . . . . . . . . . . . . . 245.3 Exchange Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

6 Open Issues and Suggestions for Improvement 276.1 Loggers improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276.2 Wind Empowerment Measurement Activities . . . . . . . . . . . . . . . . . . . . . 276.3 Final conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

7 Dissemination Planning 28

8 References 29

9 Annexes 30



Executive SummarySmall wind turbines based on the Piggott design have been deployed across the world as a powerfultool in the promotion of rural electrification. Locally manufactured and maintained, these windturbines promote technology transfer and provide a method for sustainable energy production.To sustain this initiative, the Measurement Working Group of the Wind Empowerment networkhas worked throughout the past 2 years to bring together local actors throughout the world tocollaborate in the creation of low-cost locally manufactured data loggers.

The Wind Empowerment Measurement WG is composed of several members interested in cre-ating affordable ways of gathering and treating data for several purposes, from power curve studiesto remote monitoring. After 2 years of work, several low-cost data logger designs have been de-veloped for studying small wind turbine based installations. The proposed Transnational Accessproject seeks to build upon the previous work of the Wind Empowerment Measurement WG andbring its main specialists together to test, validate and analyze the data logger designs currentlyavailable. To achieve this, a series of experiments are proposed in the facilities for RenewableEnergy Systems and data logging at ICCS-NTUA.

The proposed tests have simultaneously tackled the measuring capabilities of the different dataloggers and the most appropriate data treatment methods for handling the results. In a first series ofexperiments, data loggers were tested for their measuring precision and accuracy for electric power,voltage and current in single-phase, three-phase and direct current systems. The results showedthe need of a robust and low-cost calibration method, which was developed during the project.Further measurements were done on real-life conditions, providing evidence of the precision androbustness of the calibration method.

Exchange sessions provided several opportunities to exchange in terms of hardware, firmwareand software. General consensus emerged on the need to create modular code and hardware on acombined specification process. Furture work on these aspects is expected before the end of 2018.

The precision of the measurements and the possible improvements are detailed in the conclusionsections of this document.



1 General Information fo the User ProjectThis user project is dedicated to the evalutation of different dataloggers technology and dataprocessing techniques for field testing o small locally manufactured wind turbines. The designsevaluated in the project are based on those currently available within the Wind EmpowermentNetwork.

Dubbed EVAL-LOGGERS, this project has the main objective of bringing together small windturbine practitionners with the experience in data logging to provide an open-source solution whichwill be made available through open-source licenses.

1.1 Host InsfrastructureThe infrastructure of the Electrical Energy Systems (EES) laboratory of ICCS-NTUA can providean ideal environment for the development of the proposed research. The experimental test benchesthat will be used at the different stages of the evaluation are listed below:

1. A laboratory setup at the Electrical Energy Systems laboratory of ICCS-NTUA, where athree phase grid-connected autotransformer and a variable three phase load will provide thenecessary range for current, voltage and power measurements. This setup ensures that theenvironmental interference and the respective noise possibly present at the measurementsis considerably minimized. DC power measurements will be performed using the LinearAmplifier by Spitzenberger & Spies (PAS500) that provide the necessary range for currentand voltage for power measurements. Furthermore, a test environment with low currentand voltage, allows for a thorough evaluation of the data loggers’ accuracy at low levels ofhardware implementation e.g. current, voltage, frequency values.

2. A real-life sized testbed was used to evaluate the performance of AFPM wind turbines’generators, will be exploited to assess the data loggers’ accuracy in three phase current,voltage and power measurements taking into consideration the particularities of the genera-tors’ design and operation, such as high current THD, wide range of operational frequency,non-symmetrical three phases etc. DC measurements will also be performed in order for theuncertainties in DC current and voltage for each of the data loggers to be assessed.

3. A real-life test site located at Rafina, Attiki, where a small wind turbine is installed and ismonitored through a high accuracy data logging system (National Instruments), will be usedto compare the performance of the prototypes with the already installed and operationalsystem and evaluate their operation in real life conditions. Environmental parameters suchas wind speed and wind direction will be also evaluated.

(a) NTUA-ICCS (b) Smart-Rue Research Team

Figure 1: The host institutions

1.2 User Group MembersDr. Luiz Fernando Lavado Villa is an Associate Professor at the University Paul Sabatierin Toulouse, France. Dr. Villa conducts his research on modular power electronics convertersfor flexible power systems architectures at the LAAS laboratory. His main interest is modularityand complexity In modular systems and their use in handling intermittent energy sources and



loads. Power electronics topologies and control algorithms are among his current research topicsof interest. To evaluate these solutions, data logging is of ultmost importance.

Dr. Matthew Little is an electronics engineer with a strong field background. Throughout2007 and 2008 Dr. Little was working to install small renewable energy projects (wind, micro-hydro and solar PV) in the Philippines for a Filipino NGO (Sibol Ng Agham At Teknolihiya).Previously he completed his PhD research into medium sized off-grid renewable energy systemsat the Centre for Renewable Energy Systems (CREST) in Loughborough University. Dr. Littleworks on a number of renewable energy related projects, most of which is documented here on hiswebsite.

Gilles Longuet has been working with locally manufactured small wind turbines for the past 6years, maily with the Piggott design. Mr. Longuet is mainly interested in improving the electronichardware of the data logger design. In October 2014, he attended the WEAthens conferencesas a representative of Tripalium to present his datalogger project. In April 2015, he organizedthe Windlogger developmentd camp in Toulouse, in France, in order to regroup those working ondataloggers in Wind Empowerment. In Tripalium, he has contributed to the developped of a low-cost hardware to monitor a wind turbine

LAAS/CNRS (fig.2(a))is a laboratory dedicated to the study of systems and their archi-tectures. From robots to critical software, LAAS studies different aspects of systems. Amongits resarch teams, LAAS has the Energy Management and System Integration team dedicated tostudying power electronics from the component up to the system-level application. Among itsthemes of research the team studies rural electrification and modular power electronics for thepenetration of renewable energy sources in isolated micro-grids.

Renewable Energy Innovation (fig.2(b))specialise in electrical and electronic systems forrenewable energy projects, mainly solar, wind and micro-hydro. We focus on renewable energybased stand- alone power supply systems (off-grid systems). This includes power and energymonitoring, battery charge control and wiring systems. Projects we have been involved with rangefrom small, portable solar-powered systems, through pedal powered devices up to large multi-kilowatt photovoltaic arrays.

Tripalium (fig.2(c))is an association whose objective is to promote small wind power throughthe construction of Piggot design small wind turbines in France. Its members contribute to theoverall improvement of the Piggott design mainly through their manual which is collectively builtand improved. Members also contribute to solve issues in off-grid electric system through theconstruction of open-source charge controllers. Other members are interested in maintenance andestimating the production of their installations, which has created the need for an open-sourcedata logger. This has driven the contribution of its members, most notably Gilles Longuet, to theWind Empowerment Measurement WG.

Wind Empowerment (fig.2(d))is an association for the development of locally manufac-tured small wind turbines for sustainable rural electrification. We represent dozens of memberorganisations, consisting of wind turbine manufacturers, non-governmental organisations, universi-ties, social enterprises, co-operatives, training centres, as well as over 1,000 individual participantsacross the world.

(a) LAAS-CNRS laboratory (b) Re-Innovation



(c) Tripalium Network (d) Wind Empower-ment Network

Figure 2: The institutions participating in the project

1.3 The schedule for the two weeks

Monday Tuesday Thursday Friday Monday Tuesday Thursday Friday

07/03/17 07/04/17 07/05/17 07/06/17 07/07/17 07/10/17 07/11/17 07/12/17 07/13/17 07/14/17

AM

PM

PPM Exchange Exchange Exchange Exchange Exchange Exchange Exchange Exchange

legend

exchanges discussions

setups tests

Wednesday

Wednesday

Laboratory set-up

Projects presentatio

ns

Hardware calibration

DC source tests

Hardware calibration

AC source tests

Rectified AC source

setup

Wind Turbine source setup

Rafina site setup

Documentation

Laboratory set-up

Hardware installation

Software discussion

DC source tests

DC source tests – AC

source setup

AC source tests

Rectified AC source

tests

Wind turbine

simulator tests

Rafina site tests

Wrap-up session

Exchange on future actions

Exchange on future actions

Figure 3: Schedule of the first week



2 Research MotivationThis project is the next step on the effort to provide local small wind manufacturers with the toolsthey need to create, install and monitor their installations. The original approach of this researchis the coupling of different aspects of this development problem.

The Innovation sought in this project is to find the compromise between simplicity and accuracy.While impeding problems must be solved, certain issues might imply a trade-off between cost,complexity and accessibility. Seeking the simplest solution that still delivers the most accurateinformation while keeping the learning curve as gentle as possible is a challenge the team will beconfronted with throughout this project and afterwards.

The Wind Empowerment Maintenance Working Group will use the data logger to remotelymonitor the condition of the wind turbine and estimate its state of operation. This is speciallyuseful for preventive maintenance and remote monitoring of sites which are of difficult access. TheTechnology Working Group has an open-source modular power electronics research theme whichseeks to provide the membership of Wind Empowerment with open-source designs for the powerconverters used in the electric installations. A data logger capable of monitoring AC and DC powersuch as the one that will be studied in this project will allow the creation of locally manufacturedelectric systems which can be monitored during operation. Furthermore, visibility on the electrisystem will help the study of failures, short-circuits or the estimation of system expansion. All ofthese actions will only be possible with the access of low-cost solution for data acquisition.

2.1 The objectives of the projectTable 1 summarizes the objectives of the project.

Table 1: Objectives of the project

Objective Description PriorityHardware

improvementCross-compare different hardware solutions and provide

framework for future development High

Firmwareimprovement

Analyse firmware architecture and code to provide bestpractices and future improvements High

Softwareimprovement

Compare different human to machin interfaces and discusson the best solutions for off-grid systems High

Calibrationprocedures

Discuss on the calibration procedures for off-gridconditions High

Measurementvalidation Validate the full operation of the dataloggers Medium

2.2 Scope of the projectDuring the tests, the group will not only work to evaluate their designs, but also to render thefinal design of the data logger as accessible as possible to anyone interested in using it. This is amultidisciplinary effort comprising the evaluation of the harware, the improvement of the softwareand the corrections in an open-access manual. Actions such as data analysis will not only imply themathematical treatment but also hardware improvement and final user experience simplification.Thus, while contributing to certain specialized bodies of knowledge, the project will also keep anoverall multi-disciplinary approach to its contributions in the issues of creating, testing, validatingand delivering a hardware, firmware, software and algorithm open-source suite.

The final version of the data logger will be used in other projects, such as the deploymentsof dozens of data loggers throughout South America. One of the main issues of deploying dataloggers is to have a clear understanding of their characteristics in order to validate the first sets ofdata while still on the field. From the tests conducted in this work, the working group expects theemergence of a body of knowledge capable of helping others to estimate if their own copies of thedata logger are operating well.



3 State-of-the-artMore than a billion people still lack clean and safe electricity in rural regions throughout theworld [1]. Electrification in developing countries has mostly targeted urban areas, leaving ruralpopulations aside [2]. This lead to national and international initiatives, projects and programs topromote, install or operate small-scale energy systems, powered by renewable energy systems [3].

The scientific community was also an important participant in this rural electrification effort[3, 4]. Contributions range from methods for modeling local renewable energy resources [5], de-ployment of local micro-grids [6] to the development of energy management strategies [4].

To local stakeholders, the deployment of technology and its transfer are conditioned to theaccess of the proper tools to build, maintain and monitor renewable energy systems [6]. Designssuch as the Piggott wind turbine [7] allow transfer of technology with easily accessible tools andcomprehensive maintenance. In terms of monitoring, the scientific community can profit from thedata to evaluate the models used in the sizing and control of the energy systems [8].

The intermittent and unpredictable operating conditions of the wind turbines exert stress overits moving parts, such as bearings and blades, counting for an increased interest in the scientificcommunity for remote monitoring of wind turbines [9]. Initiatives in creating reliable monitoringtools seek to decrease O&M costs and downtime of the wind turbines. In a more general way,monitoring requires technology, specialized people, condition indicators and quality measurementsto estimate the operating conditions of a system [9].

Monitoring systems are composed of elements such as: monitored parameters, sensors, con-troller, data transfer mechanism, program development software and monitoring method [10]. Pa-rameters vary according to the renewable energy system, as irradiance for PV and wind speed forwind turbines. Sensing physical variables imply choosing the appropriate sensors and account fortheir imprecision [10]. The choice of the controller must match with the operating conditions of itssensors. The choice of the data transfer mechanism will have important implications on the energyconsumption of the data logger.

The operation of data loggers is met with several challenges [10]. Harsh environments, reliability,efficiency degradation, resource constraints, system calibration, economic viability, and others. Itis thus paramount for a system to be tested for these constraints before deployment in the field.It is also important that the technical documentation of the data logger provide insight on itslimitations and best practices for its deployment. All of these require tests both in laboratory andon the field under known conditions [11].

This project provided the conditions to evaluate two different data logger designs, their mea-surement precision under different operating conditions and their possible improvements prior tofield deployment.

3.1 The dataloggersTwo dataloggers were studied during this project, the Windlogger and Re-Innovation UK’s data-logger.

The Windlogger is a datalogger developped by Tripalium to study both wind resources andwind turbine production. It was designed to be a modular addition to an already existing off-gridinstallation. Its specifications are shown in table 2. Figure 4(a) shows an image of the Windlogger.

Table 2: Specifications of the dataloggers

Variable Windlogger RE-Innovation LoggerAvailable? Range Available? Range

DC Current YES (x4) 100 A YES(x1) 25 ADC Voltage YES (x1) 100 V YES(x1) 100 VAC Current YES (x4) 100 A NO -AC Voltage YES (x1) 400 V NO -Wind Speed YES (x2) 50 m

s NO -Wind Direction YES (x1) 15 to 350° NO -

Temperature YES (x1) 0 to 100℃ YES(x1) 0 to 100℃



(a) Tripalium’s Windlogger (b) Re-Innovation UK’s Datalogger

Figure 4: The two dataloggers models studied during the two weeks



4 Experimental workThis transnational access project focused on the characterization of dataloggers in real-life fieldconditions. A series of experiments took place to test the dataloggers on various conditions. Thissection describes the test plan, the producedures, the setups and the data management of theproject.

4.1 Test planThe tests were planned to go from more simple to more complex measurements. A summary ofthe test setups is provided in table 3.

Table 3: General Summary of all the experimental setups

Experimental Exp. ExperimentSetup # Description

1 DC voltage calibration and testSetup I - DC 2 DC voltage and current steps measurements

3 DC voltage and current steps measurementsSetup II -

AC 4 AC voltage and current calibration and test

Setup III -AC/DC 5 AC/DC voltage and current measurements with little noise

Setup IV - 6 AC and DC tests with real noise and system conditionsAC/DCMotor 7 AC and DC tests with real noise and system conditions

Setup V -Rafina Test

site8 Real-life conditions test for characterizing the installation

4.2 Standards, Procedures and MethodologyDuring the first week, laboratory setups I and II for DC and AC measurement with controlledvoltage souces were conducted. During the second week, simultaneous AC/DC measurements wereconducted in laboratory conditions through setup III.

A three phase grid-connected autotransformer and a variable three phase load will providethe necessary range for current, voltage and power measurements. This setup ensures that theenvironmental interference and the respective noise possibly present at the measurements is con-siderably minimized. DC power measurements will be performed using the Linear Amplifier bySpitzenberger & Spies (PAS500) that provide the necessary range for current and voltage for powermeasurements. Furthermore, a test environment with low current and voltage, allows for a thor-ough evaluation of the data loggers’ accuracy at low levels of hardware implementation e.g. current,voltage, frequency values.

A laboratory motor was installed to simulate a Piggott wind turbine, leading to simultaneousAC/DC measurements in real noice conditions in setup IV.

A real-life sized testbed was used to evaluate the performance of AFPM wind turbines’ genera-tors, will be exploited to assess the data loggers’ accuracy in three phase current, voltage and powermeasurements taking into consideration the particularities of the generators’ design and operation,such as high current THD, wide range of operational frequency, non-symmetrical three phases etc.DC measurements were also performed in order for the uncertainties in DC current and voltagefor each of the data loggers to be assessed.

Finally, a full day of measurements and characterizations was performed at the Rafina smallwind turbine site in setup V. This real-life test site, located at Rafina - Attiki, is equipped witha small wind turbine and a high accuracy data logging system (National Instruments). The datafrom this logger was used to compare the performance of the Windlogger and Re-Innovation’s



datalogger and evaluate their operation in real life conditions. Environmental parameters such aswind speed were be also evaluated.

4.3 Test setupsThe test setups are detailes in this subsection.

4.3.1 Setup I - Perfect DC source

This setup consists of a programmable DC source connected in series with a resistance as illustratedin figure 5. Figure 5(a) shows the electrical connexions of the Yokogawa, the Tripalium Windloggerand the RE-Innovation logger. Both the Yokogawa and the Windlogger have non-intrusive hall-effect sensors, while the Re-Innovation logger has a shunt-based solution.

+VDC

-

YokogawaTripalium

loggerRe-Innov.

logger

i MEA

S

i MEA

S

+VMEAS-

+VDC

-

+VRLOAD

-

iDC

+VMEAS- +VMEAS-+ViMEAS-

(a) Setup I connections (b) Photo of setup I

Figure 5: Setup I - Perfect DC source

DC voltage and DC current were measured according to the details given in table 4. Therewere a total of three experiments. Experiment 1 focused on voltage measurement and calibration.Experiments 2 and 3 focused on current measurement and precision at low values, such as 0.5A.

Table 4: Setup I experimental details

Experimental Exp. Variables measuredSetup # Variable Description

1 DC Voltage 5V to 30V to 5V with 2-minute-long5V steps

Setup I - DC 2 DC Voltage andCurrent

0A to 12A with 2-minute-long 0.5Asteps

3 DC Voltage andCurrent

0A to 8A with 2-minute-long 0.5Asteps

4.3.2 Experiment II - Perfect AC source

This setup consists of a variable autotransformer connected in series with a resistance as illustratedin figure 6. Figure 5(a) shows the electrical connexions of the Yokogawa and the Tripalium Wind-logger. The Re-Innovation logger is not equipped with AC voltage or current measurements andwas not included in this Experiment.



+VAC

-

YokogawaTripalium

logger

i MEA

S

i MEA

S

+VMEAS-

+VRLOAD

-

iAC

+VMEAS-

(a) Setup II connections (b) Photo of setup II

Figure 6: Setup II - Perfect AC source

AC voltage and AC current were measured according to the details given in table 5. Thissetup was composed of a single experiment (#4) focused on AC voltage calibration and powercalculation.

Table 5: Setup II experimental details


Setup II -AC 4 AC Voltage and

Current2A to 9.5A with 1-minute-long 0.5A

steps

4.3.3 Experiment III - Perfect AC source with diode bridge

In this setup, a diode bridge is connected between the variable autotransformer and the resistanceas illustrated in figure 7. This AC/DC systems is free of the real-life noise created by the windturbine, allowing the clear study of the measurements in a controlled environment. Figure 7 alsoshows the electrical connexions of the Yokogawa, the Tripalium Windlogger and the Re-Innovationlogger.

+VAC

-

YokogawaTripalium

loggerRe-Innov.

logger

iDC

MEA

S

iDC

MEA

S

+VDCMEAS-

+VRLOAD

-

iDC

+VDCMEAS- +VDCMEAS-iAC

MEA

S

iAC

MEA

S

+VACMEAS-

iACMEAS

+VACMEAS-

iAC

+ViMEAS-

Figure 7: Electrical connections of Experiment III

AC voltage, AC current, DC voltage and DC current were measured according to the detailsgiven in table 6. This setup was composed of a single experiment (#5) where power was variedfrom 10W to 200W.



Table 6: Setup III experimental details


Setup III -AC/DC 5 AC/DC Voltage

and Current 10W to 200W

4.3.4 Experiment IV - Laboratory Controlled Generator

In this setup, a laboratory controlled motor was connected to the shaft of a locally manufactureddisk machine, simulating a wind turbine. The motor was controlled to provide the speed necessaryfor a specific voltage step being measured. The generator was connected to a battery rack, servingas a load, as illustrated in figure 8. This AC/DC systems has real-life noise created by the windturbine voltage rectification, allowing the clear study of the degradation of measurement precision.

YokogawaTripalium

loggerRe-Innov.

logger

iDC

MEA

S

iDC

MEA

S

+VDCMEAS-

+VRLOAD

-

iDC


MEA

S

iAC

MEA

S

+VACMEAS-

iACMEAS

+VACMEAS-

iAC

ω

+ViMEAS-

(a) Setup IV connections (b) Photo of setup IV

Figure 8: Setup IV - Laboratory Controlled Generator

AC voltage, AC current, DC voltage and DC current were measured according to the detailsgiven in table 6. This setup was composed of a two experiment (#6 and #7) where current wasvaried from 0A to 10A with steps of 2 minutes.

Table 7: Setup IV experimental details


Setup IV - 6 AC/DC Voltageand Current 0A to 10A with 2-minute-long 1A steps

AC/DCMotor 7 AC/DC Voltage

and Current 0A to 10A with 2-minute-long 1A steps

4.3.5 Setup V - Rafina Test site

In this setup, the dataloggers were installed at the Rafina test site. The site is equipped with twosmall wind turbines, of which one is constantly monitored by a National Instruments datalogger.The energy produced is stored at a battery bank, as shown in figure ?? The National Instrumentsdatalogger, the Tripalium Windlogger and the RE-Innovation datalogger are connected to theinstallation as shown in figure 9.



N.I. logger

Tripaliumlogger

Re-Innov.logger

iDC

MEA

S

iDC

MEA

S

+VDCMEAS-

+VRLOAD

-

iDC


MEA

S

iAC

MEA

S

+VACMEAS-

iACMEAS

+VACMEAS-

iAC

Windvane

Anemometer

Wind Turbine

+ViMEAS-

WindDirectionMEAS

WindSpeedMEAS

Figure 9: Setup V - Rafina test site

(a) View of the wind turbine (b) The installation

Figure 10: Setup V - Rafina test site photos

AC voltage, AC current, DC voltage, DC current and wind speed were measured according tothe details given in table 8. The measurement lasted 4 hours and provided evidence to comparethe results of the dataloggers on real-life conditions.

Table 8: Setup V experimental details


Setup V -Test site 8

AC/DC Voltageand Current, wind

speed

4-hour-long datalogging every 10seconds



5 Results and ConclusionsThis project has provided information on testing procedures, precision results and datalogger de-velopment techniques. These results are described in the subsections below.

5.1 Experimental resultsThe experimental results are presented below according to its corresponding setup.

5.1.1 Setup I - DC

This initial setup had the purpose of characterizing the precision of both dataloggers.The voltage test results, shown in figure 11(a), give a clear matching between both dataloggers

and the NTUA equipment used as a reference. The error, shown in figure 11(b), is globally lessthan 2%.

Current measurements are also shown in figures 11(c) and 11(e). The measurement error ishigher, specially for low currents. In these tests, an average of less than 5% is visible for allmeasurements taking place in steady-state conditions. Transitions were more difficult to measure,with an average error of around 5%.

0 20 40 60 80 100 120

5

10

15

20

25

30

35

points

Vol

tage

(V

)

RE-InnovTripaliumNTUA

(a) Experiment 1 - Voltage results

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Figure 11: Setup I - Experiment 1, 2 and 3 results

5.1.2 Setup II - AC

This setup focused on AC voltage and current measurement and involved only Tripalium’s Wind-logger.

The voltage test results, shown in figure 12(a), show that the Tripalium logger oscillates aroundthe average value measured by the reference. This tendency is clearly visibe for higher voltagesin the error graph, shown in figure 12(b). While the error oscillates around 1% to 2% in steadystate conditions for low voltages, it is clearly oscillating between 3% to 4% for voltages higher than200V.

Current measurements in figures 12(c) also show a dispertion of measurements around thereference. The error is globally higher in AC than DC, but lower for low currents. The averageerror is around 5%.

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5.1.3 Setup III - AC/DC

This setup regroups DC and AC measurements under controlled conditions, due to technical issuesonly the Tripalium logger was tested.

The DC voltage test results, shown in figure 13(a), show that the Tripalium logger has acalibration error. This represents a clear 2.5% error accross measurements as shown in figure13(b).

DC Current measurements are also affected by this calibration issue, as shown in figure 13(c).The current error is globally much higher for currents below 4A, ranging between 20% to 5%. Forhigher currents, the error falls steadily to below 5%, as shown in figure 13(d).

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Figure 13: Setup III - Experiment 5 DC measurement results

The AC voltage test results, shown in figure 14(a), show a clear oscillation issue with themeasurement calibration procedure for AC as well. The error is shown to be spread between 2%to 4%, for all steady-state measurements, as shown in figure 14(b).

AC Current measurements are clearly offset by a certain amount, as shown in figure 14(c). Thecurrent error is globally much higher for currents below 1A, ranging between 60% to 20%. Forhigher currents, the error stabilizes around 20%, as shown in figure 13(d).

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Figure 14: Setup III - Experiment 5 AC measurement results

These measurements have contributed to several discussions on calibration methods capable ofgiving good results with off-the-shelf measuring equipment. The details of the calibration methodare given below in section 5.2.

5.1.4 Setup IV - AC/DC Motor

This setup tests the AC/DC measurements under more realistic noise conditions. The technicalissues of RE-Innovation’s logger were solved and both loggers participated in the measurements.

The DC voltage test results, shown in figure 15(a), show that the Tripalium logger persistedwith 2% offset error. Re-Innovation’s logger is shown to have an oscillation error, which was linkedto its measuring algorithm. However, its mean error is roughly of 1%, as shown in 15(b).

DC Current measurements involved only Tripalium’s logger, since Re-Innovation current mea-surement was still facing tecnical issues. The results in figure 15(c) show a steady offset acrossthe test current range. The error reduces exponentially from 20% for lower currents to around 4%above 6A, as shown in figure 15(d).



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The AC voltage test results, shown in figure 16(a), show the same oscillation issue with the mea-surement. The error is shown to be spread between 0% to 6%, for all steady-state measurements,as shown in figure 16(b).

AC Current measurements are clearly more precise than in setup III, as shown in figure 16(c).The current error is globally is still much higher for currents below 4A, but ranges only between10% to 4%. For higher currents, the error stabilizes around 3%, as shown in figure 16(d).

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Figure 16: Setup IV - Experiment 6 AC measurement resultsExperiment 7 was conducted to confirm the data from experiment 6. The DC voltage results

in figure 17(a) show the same tendency as in the experiment 6. Figure 17(b) confirms the averageerror for the Tripalium logger around 2% and the error for RE-Innovation’s logger around 1%.

The DC current results in figure 17(c) show a slight improvement from experiment 6. Figure17(d) confirms the exponential error decay for the Tripalium logger from 10% for lower currentsdown to 2% for currents above 5A.

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Figure 17: Setup IV - Experiment 7 DC measurement resultsThe AC voltage results in figure 18(a) show the same tendency as in the experiment 6. Figure

18(b) confirms the error for the Tripalium logger between 0% and 6%.



The current results in figure 18(c) show a slight improvement from experiment 6. Figure 18(d)confirms the exponential error decay, but shows a lower error, ranging in average between 5% forlower currents down to 3% above 6A.

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Figure 18: Setup IV - Experiment 7 AC measurement results

5.1.5 Setup V - Rafina Test site

This setup tests the dataloggers at a real-life installation. Due to technical issues, the wind directionan the DC current and voltage could not be measured with the reference NTUA logger. The datafor the DC measurements will be cross-compared with the two loggers.

The DC voltage test results, shown in figure 19(a), show that the Tripalium logger and theRe-Innovation logger are both solidly tracking the same value. The same tendency is clearly visiblefor the DC current in figure 19(b).



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Figure 19: Setup V - Experiment 8 DC measurement results

The AC voltage test results, shown in figure 20(a), show the Tripalium with a slight voltageoffset. This offset is visible in an average error of 7%, as shown in figure 20(b).

The AC current test results give clear indications of the current behaviour of the wind turbine.When comparing figure 20(c) with figure 19(b), it is clear that the DC current and the AC RMScurrent behaviours are very similar. This together with the fact that the current error is at most5% as shown in figure 20(d), give a clear indication that the dataloggers are providing solid powerdata on the wind plant.

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The wind speed test results, shown in figure 21(a), provide further evidence of the accuracyof the Windlogger. Variations in wind speed have exactly the same behaviour as in the current,providing another element to confirm the datalogger measurements. The measurement error isbelow 1%, as shown in figure 21(b).

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5.1.6 Summary of experimental results

A general summary of the experimental results is given in table 9. The ranges of precision for thedataloggers is given for each setup, experiment and variable.

Table 9: Summary of the conclusions for each setup

Experimental Exp. Average Error (%)Setup # VDC iDC VAC iAC wspeed

1 2% - - - -Setup I - DC 2 - 5% - - -

3 - 5% - - -Setup II - AC 4 - - 3% to 4% 5%

Setup III - AC/DC 5 2.5% 5% to 20% 2% to 4% 20% -

Setup IV - 6 1% to 2% 4% to 20% 0% to 6% 3% to10% -

AC/DC Motor 7 1% to 2% 2% to 10% 0% to 6% 3% to 5% -Setup V - Rafina Test site 8 - - 7% 0% to 6% 1%

5.2 Low-Cost Callibration of the dataloggerCallibration is an important issue in datalogging. Issues with measurement dispersion and preci-sion were addressed during the first setups, leading to the development of a low-cost calibrationprocedure. This calibration is done using an off-the-shelf multimeter and yields similar results tousing the reference equipment of NTUA in the calibration process.

Figure 22 shows the different steps in the calibration procedure.



+Vsource

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(a) Calibration setup (b) Step 1: set the factor under test to one

(c) Step 1: set up the source to a given test voltage (d) Step 2: measure the voltageprior to the ADC

(e) Step 3: Write down the raw reading (to the leftof the highlighted number)

(f) Step 4: Write down the input voltages (left col-umn) and the readings (central columns)



(g) Step 5: Calculate the factor for each pair ofinput/reading and calculate the overall average

(h) Step 6: Set the factor under test (in this case,the voltage)

(i) Step 7: Confirm the parameter has beenchanged

(j) Step 7: Close-up of the parameter and the cal-culation table

(k) Step 8: Set up an input voltage (20.7V in thiscase)

(l) Step 9: Confirm the datalogger measurement(20.694V in this example)

Figure 22: Calibration procedure for the Tripalium Wind logger

5.3 Exchange ConclusionsThe most important conclusion from the exchanges was the need to standardize the hardware ANDthe development tools currently used within Wind Empowerment. The presentation on Eclipse hassparked a particular interest from all the participants and should lead to a future webinar on theissue. Hardware standardization should focus on what type of housing to use (DIP or SMD) inorder to ease the local assembly of the equipment by local practitionners.



6 Open Issues and Suggestions for ImprovementDuring the project, several discussions regarding future improvements were conducted. Their mainconclusions are summarized in this section.

6.1 Loggers improvementsImprovements for both dataloggers are summarized in table 10.

Table 10: Tripalium’s Windlogger improvements list

Improvement Windlogger RE-Innovation LoggerMeasurement

precisionUse external 12-bits ADCs for

better precision No improvements needed

Measurementstability No improvements needed Improve measurement algorithm

Energyconsumption Implement a low-power state Improve battery management

Real-time clock Integrate a real-time clock tothe datalogger No improvement needed

Control algorithm Improve the classes for an easierdescription of new sensors Re-structure the code on C++

Newer versions Consolidate changes on a newKiCad version No improvement needed

6.2 Wind Empowerment Measurement ActivitiesThe next steps in Wind Empowerment’s measuring activities will focus on deploying several copiesof the final version of the datalogger in field conditions. The deployment and data treatment ofthe datalogger will be of particular interest in future activities.

6.3 Final conclusionsThis experience was of great use for the measurement working group of Wind Empowerment inparticular and for the participants in general. The initiative of cross-comparing current dataloggerversions, issues and future needs has led to further talks and to future developments which arecurrently underway.



7 Dissemination PlanningThe totality of the data and the results will be shared as open-access material through the WindEmpowerment website. The data logger and any related documentation such as schematics, rout-ing, bill of materials, software and construction manual will be shared freely through an open-source license.

During the Maintenance WG project for massive deployment of the data logger in South Amer-ica, the data of this project will be used to help local actors to estimate if their data loggers areoperating correctly. The algorithms and data treatment methods developed during this projectwill be made available through a comprehensive documentation of the software needed to treat thedata from the data logger.

Any insights from the analysis of the test data which can help detect flaws and improve thehardware of the data logger will be used in publications on hardware diagnosis. In terms of software,any new algorithms will be presented to the corresponding scientific and technical communitiesthrough publications.



8 References[1] IEA. World Energy Outlook 2012. Paris CEDEX: OECD Publishing 2012

[2] Stefano Mandelli, Jacopo Barbieri, Riccardo Mereu, Emanuela Colombo, Off-grid systemsfor rural electrification in developing countries: Definitions, classification and a comprehensiveliterature review, Renewable and Sustainable Energy Reviews, Volume 58, May 2016, Pages 1621-1646

[3] R.K. Akikur, R. Saidur, H.W. Ping, K.R. Ullah, Comparative study of stand-alone andhybrid solar energy systems suitable for off-grid rural electrification: A review, Renewable andSustainable Energy Reviews, Volume 27, November 2013, Pages 738-752, ISSN 1364-0321,

[4] Lanre Olatomiwa, Saad Mekhilef, M.S. Ismail, M. Moghavvemi, Energy management strate-gies in hybrid renewable energy systems: A review, Renewable and Sustainable Energy Reviews,Volume 62, September 2016, Pages 821-835, ISSN 1364-0321

[5] Prabodh Bajpai, Vaishalee Dash, Hybrid renewable energy systems for power generation instand-alone applications: A review, Renewable and Sustainable Energy Reviews, Volume 16, Issue5, June 2012, Pages 2926-2939

[6] K. Latoufis, A. Gravas, G. Messinis, N. Korres, N. Hatziargyriou, “Locally manufacturedopen source hardware small wind turbines for sustainable rural electrification”, 3rd World Summitfor Small Wind, 15-16 March 2012, Husum, Germany

[7] H.Piggott, A Wind Turbine Recipe Book-The Axial Flux Windmill Plans, 2009[8] Diana Neves, Carlos A. Silva, Stephen Connors, Design and implementation of hybrid renew-

able energy systems on micro-communities: A review on case studies, Renewable and SustainableEnergy Reviews, Volume 31, March 2014, Pages 935-946

[9] de Azevedo, Henrique Dias Machado, Alex Maurıcio Araujo, and Nadege Bouchonneau. ”Areview of wind turbine bearing condition monitoring: State of the art and challenges.” Renewableand Sustainable Energy Reviews 56 (2016): 368-379.

[10] Madeti, Siva Ramakrishna, and S. N. Singh. ”Monitoring system for photovoltaic plants:A review.” Renewable and Sustainable Energy Reviews 67 (2017): 1180-1207.

[11] J. Leary, H. Piggott, R. Howell, A. While,“Power Curve Measurements of Locally Manu-factured Small Wind Turbines”, 8th PhD Seminar on Wind Energy in Europe September 12 - 14,2012, ETH Zurich, Switzerland



9 Annexes



List of Figures1 The host institutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 The institutions participating in the project . . . . . . . . . . . . . . . . . . . . . . 73 Schedule of the first week . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 The two dataloggers models studied during the two weeks . . . . . . . . . . . . . . 105 Setup I - Perfect DC source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 Setup II - Perfect AC source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 Electrical connections of Experiment III . . . . . . . . . . . . . . . . . . . . . . . . 138 Setup IV - Laboratory Controlled Generator . . . . . . . . . . . . . . . . . . . . . . 149 Setup V - Rafina test site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1510 Setup V - Rafina test site photos . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1511 Setup I - Experiment 1, 2 and 3 results . . . . . . . . . . . . . . . . . . . . . . . . . 1712 Setup II - Experiment 4 results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1813 Setup III - Experiment 5 DC measurement results . . . . . . . . . . . . . . . . . . 1914 Setup III - Experiment 5 AC measurement results . . . . . . . . . . . . . . . . . . 1915 Setup IV - Experiment 6 DC measurement results . . . . . . . . . . . . . . . . . . 2016 Setup IV - Experiment 6 AC measurement results . . . . . . . . . . . . . . . . . . 2117 Setup IV - Experiment 7 DC measurement results . . . . . . . . . . . . . . . . . . 2118 Setup IV - Experiment 7 AC measurement results . . . . . . . . . . . . . . . . . . 2219 Setup V - Experiment 8 DC measurement results . . . . . . . . . . . . . . . . . . . 2320 Setup V - Experiment 8 AC measurement results . . . . . . . . . . . . . . . . . . . 2321 Setup V - Experiment 8 Wind speed results . . . . . . . . . . . . . . . . . . . . . . 2422 Calibration procedure for the Tripalium Wind logger . . . . . . . . . . . . . . . . . 26

List of Tables1 Objectives of the project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Specifications of the dataloggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 General Summary of all the experimental setups . . . . . . . . . . . . . . . . . . . 114 Setup I experimental details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 Setup II experimental details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 Setup III experimental details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Setup IV experimental details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 Setup V experimental details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 Summary of the conclusions for each setup . . . . . . . . . . . . . . . . . . . . . . . 2410 Tripalium’s Windlogger improvements list . . . . . . . . . . . . . . . . . . . . . . . 27


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