1、AMANDA project has received funding from the European Unions Horizon 2020 research and innovation programme under Grant Agreement No.825464.Powering LPWAN Nodes with Solar Cells in Low Light ConditionsAuthors:M.Meli,S.Favre(ZHAW,Switzerland)Embedded World China 2023,ShanghaiAuthors:Prof.Dr.Marcel Me

2、li,Sebastien Favre Presented by:Marcel Meli Correspondence to:memazhaw.ch nExamples of similar works from our groupnMotivation and issues nWhat is needednExamplesnConclusionsnSupport acknowledgementsPart of the work related to own research projects at ZHAW-InESPart of the work related to Amanda H202

3、0 projectAgenda2June 2023Marcel Meli,Sebastien FavreEmbedded World China 2023nR&D:Use of solar cells as harvesters for IoT applicationsSome of these works have been presented at various conferencesExamples of similar works from our group3Harvesting energy using solar cellsoutdoors,indoors,low light

4、environment,with various solar cell technologies,.Appropriate power management and processing strategiesVarious wireless systems for communication(short range,long range,.)Mouse powered with harvested energy:Source ZHAW-InES LEDs as energy harvesters Source ZHAW-InES Sensor node powered with small s

5、olar cell Source ZHAW-InES AMANDA card.Smart card format.Powered with solar cell EC Horizon 2020 project.Grant agreement 825464June 2023Marcel Meli,Sebastien FavreEmbedded World China 2023nUse of solar cells for IoT devicesSolar cells are a well-known method of harvesting energy-Popular:Many people

6、use solar-powered calculators-Efficient enough for many cases outdoor-Cost:depends on many factors,including the type of cells There are also situations where solar cells are not appropriate-Not sufficiently robust in all environmentsDust,birds,vibrations,rain,snow,.etc-Light is required to get some

7、thing out.So it is rather difficult at night.A storage is needed,which adds complexity and can impact lifetimeWith storage:it is important to have times when one can harvest sufficiently to save some energy.The saved energy can be used when there is not enough lightIf there is not enough light/energ

8、y,there is also nothing to storeMotivation and issues4June 2023Marcel Meli,Sebastien FavreEmbedded World China 2023Motivation and issues(typical levels indoor)5Some typical outdoor/indoor light levels https:/ Condition(indoor recommendations)Illumination Public areas with dark surroundings20 50(lx)S

9、imple orientation for short visits50-100Areas with traffic and corridors-stairways,escalators and travelators-lifts-storage spaces100Working areas where visual tasks are only occasionally performed100-150Warehouses,homes,theatres,archives,loading bays150Coffee break room,technical facilities,ball-mi

10、ll areas,pulp plants,waiting rooms,200Easy office work250Class rooms300Normal office work,PC work,study library,groceries,show rooms,laboratories,check-out areas,kitchens,auditoriums500Supermarkets,mechanical workshops,office landscapes750Normal drawing work,detailed mechanical workshops,operation t

11、heaters1000There is little(or n)chance to store much energy if the place is poorly litThere are many places that are poorly litIoT nodes in places that are permanently poorly lit require harvesting in low light conditions.In such cases,the power output is low.June 2023Marcel Meli,Sebastien FavreEmbe

12、dded World China 2023nIllumination(measured in ZHAW offices)might look like belowHarvest and store for the“bad days”.There is not always enough energyMotivation and issues6Harvest,use and storeUse as long as storage not emptyUse as long as storage not emptyHarvest,use and storeOffice is occupied.Lig

13、ht switched on and later off.When ON,there is about 400 lx of extra artificial lightOffice is NOT occupied.No extra artificial lightThere is less to harvest in order to cover periods of“darkness”June 2023Marcel Meli,Sebastien FavreEmbedded World China 2023nIllustration using a LPWAN node example.Her

14、e LoRaNode in an office.Harvesting when there is enough light.The harvested energy can be used at night.But there is not enough.The case is even clearer at week-ends,when the office is not lit at all.Motivation and issues7June 2023Marcel Meli,Sebastien FavreEmbedded World China 2023nLoad sideUnderst

15、and the needs of the loadOptimise the energy requirements of the loadnEnergy source sideUnderstand the limitations of the energy sourceChoose appropriate solar cells that harvest in low light conditions Optimise the energy harvesting from the source-Balance of energy available and energy consumedNot

16、 enough energy,the work will not be done-Optimise start-upDo you have enough energy for a cold start?What is needed?Low power design is key8June 2023Marcel Meli,Sebastien FavreEmbedded World China 2023nAn idea of the energy requiredObviously depends on use cases.But just to give an ideaBLE frames te

17、ns of mJ for ADV frames-Small solar cells should doLoRaWAN about 5 mJ for SF7LoRaWAN about 200 mJ for SF12,14dBm-Larger solar cellsWhat is needed?Low power design is key9June 2023Marcel Meli,Sebastien FavreEmbedded World China 2023nSC:8 cm2,22uw/cm2 200lux(Lightricity)20 lux 2.2*8=17.6 uW10 mins,80%

18、efficiency harvest 8.5 mJ nPM:EM8502(EM Microelectronic)2 storage elements.External DC/DC addednOther elementsApollo2(Ambiqmicro).LoRa:SX1276(Semtech)Sensor:BME680(Bosh Sensortech)FRAM to save status and allow low-power recovery-Switch off embedded system to improve harvesting-Power on,measure,commu

19、nicate,switch ES offExample of a LPWAN node.Elements used(2020)10Figures taken from Lightricity web siteJune 2023Marcel Meli,Sebastien FavreEmbedded World China 2023nA node with a SC of 8 cm2Running LoRa in SF7BW125,+8dBmA frame is sent every 10 minutenLuxmeter to log illuminancenPower analyser to l

20、ogStorage voltagePM input voltage(Solar cell output)Solar cell currentMeasurements setup11LuxmeterVoltmeterPower AnalyserSolar nodeJune 2023Marcel Meli,Sebastien FavreEmbedded World China 2023nTransmission of frames during the nearly 6 hours of testResults12Important results:Cold start possibleat 30

21、 lux.Operations sustainedJune 2023Marcel Meli,Sebastien FavreEmbedded World China 2023Example of a recent LPWAN node(setups)13Light chamberPower Analysers2 Luxmeters2 solar cells2 NodesLoRaWAN nodes powered using solar cells of Lightricity are used to make measurements and transmit dataSetup to make

22、 measurements in the light chamber-Power analysers are used to record voltage,current power-Data is received by a LoRaWAN gateway for verifications-Luxmeters are used to verify light intensity levelJune 2023Marcel Meli,Sebastien FavreEmbedded World China 2023Results:SF7 at 15 lux(improved on 2020 ex

23、ample)14V1:SC voltageI1:SC currentP1:SC powerV2:Storage voltageV3:Load voltageNeeds 1hours 45 mins to cold start until first Tx/Rx.Then frames every 30 mins.30 mins is set as minimum interval.But the system could work faster.This can be seen as V2 is still rising,meaning more harvested than used.(5

24、mF supercap)Once started,the system will continue to run,if enough light.E:InESTeam_wirelessWireless_Congress_2021_Solar_Nodemeasurement_filesSF7_TDK_SF7_lightricity_15lx_24h_21-22 dec 2021Cold startPOR of PMMCU Tx/RxMCU Tx/RxMCU Tx/Rx30 mins between activitiesJune 2023Marcel Meli,Sebastien FavreEmb

25、edded World China 2023A difficult case SF12 at 30 lux(max range)15Needs 37 hours to cold start until first Tx/Rx.Then frames every 4 hours or less.Energy tests are done every 30 mins(pulse of 52 ms).Frame pulses are 3.2 secs.About 200 mJ between Markers 1 and 2.(100 mF supercap)Once started,the syst

26、em will continue to run,if enough light.E:InESTeam_wirelessWireless_Congress_2021_Solar_Nodemeasurement_filesSF12_lightricity_30lx_48h_28-29 dec 2021V1:Solar Cell voltageI1:SC currentP1:SC powerV2:Storage voltageV3:Load voltageCold startPOR of PMMCU Tx/RxMCU Tx/RxMCU power checks every 30 minsJune 2

27、023Marcel Meli,Sebastien FavreEmbedded World China 2023nThere is a need in some environments to power LPWAN nodes under low light conditions.Challenging because:Small amount of harvested energyRelatively high energy requirements of LPWAN nodesnCareful attention to design details can helpChoose solar

28、 cells that are efficient at low lightLow-power components for embedded systemProper power management to allow harvesting at low lightnThe present design can work at low light15 lux for LoRa SF7.After long start-up,operation is sustained 30 lux for LoRa SF12.After long start-up,operation is sustaine

29、d Conclusions16June 2023Marcel Meli,Sebastien FavreEmbedded World China 2023nR&D:Use of TEGs as harvesters for IoT applicationsMonitoring underground drinking water infrastructure-TEGs are used to harvest energy underground.No contact with water-Energy used to power wireless sensor nodes(LPWAN)-Year

30、s of operation.No batteries,no cablesExamples of similar works from our group17June 2023Marcel Meli,Sebastien FavreEmbedded World China 2023https:/ Enquiries to marcel Melimemazhaw.ch Question time18June 2023Marcel Meli,Sebastien FavreEmbedded World China 2023Motivation(typical values outdoor/indoor

31、)19ConditionIllumination Sunlight107527(lx)Full Daylight10752Overcast Day1075Very Dark Day107Twilight10.8Deep Twilight1.08Full Moon0.108Quarter Moon0.0108Starlight0.0011Overcast Night0.0001Some typical outdoor/indoor light levels.Taken from https:/ recommendations)Illumination Public areas with dark

32、 surroundings20 50(lx)Simple orientation for short visits50-100Areas with traffic and corridors-stairways,escalators and travelators-lifts-storage spaces100Working areas where visual tasks are only occasionally performed100-150Warehouses,homes,theaters,archives,loading bays150Coffee break room,techn

33、ical facilities,ball-mill areas,pulp plants,waiting rooms,200Easy office work250Class rooms300Normal office work,PC work,study library,groceries,show rooms,laboratories,check-out areas,kitchens,auditoriums500Supermarkets,mechanical workshops,office landscapes750Normal drawing work,detailed mechanical workshops,operation theaters1000June 2023Marcel Meli,Sebastien FavreEmbedded World China 2023