Off Grid System Design - AEE Solar
Off Grid System DesignBrad BassettSr. Application EngineerJan 19, 2018San Diego, CA
What is an “Off-Grid” system? No access to the utility electrical grid, or limited or no use of the utility grid Batteries used to provide for loads when it’s dark or cloudy–Often referred to as Battery-Based systems Modules and racking are usually the same as used in grid-tie systems Most other components are specialized
Types of Off-Grid systems PV–––directLoads are run directly from the solar sourceNo energy storage (batteries)Loads typically motors (pumps, fans, etc.) that run directly from the solar array DC-Only– All loads run on DC from a battery– Batteries charged by PV, engine generator, wind, hydro etc. AC-only– All loads run on AC power from an inverter or AC generator AC/DC– Both AC and DC loads are powered by the system Hybrid– Derives energy from more than one sourcei.e. PV and a generator, PV and wind and/or hydro– Most common type of Off-Grid system used for homes
PV Direct Systems Load is run directly from solar array, without energy storage(batteries). Generally used only with motors, like pumps and fans, which can rundirectly from a DC energy source. Well pumps are the most commonload Loads can only run when energy is available from the productionsource since there is no energy storage Very simple systems– minimal equipment needed, such as solar array,direct drive controller, and the load Loads run at variable speed depending on energy available fromsource: PV-direct systems do not work at night Current limited: only the amount of current that is directly producedby the energy source is present. Often means that overcurrent devicesare not needed as long as the conductors are sized to handle fullcurrent
DC-Only Systems Load size & voltage drives design–– DC load current and run timedetermines system sizeNo AC loads or inverterPV used to charge the battery bank––Constant power from intermittentsourceSometimes with generator backup Common applications include lighting,communications, telemetry, signageand data logging Example: Weather station––––PV array and mounting structure12 VDC BatteryPWM Charge controllerWeather sensors and datalogger/transmitter
AC–Only systems AC from an inverter powers all of theelectrical loads–Any type of AC load can be powered–Inverter output limits total load draw–Appliances and wiring are standardand easy to findInverter draws from battery bank–PV array charges batteries as in DConly system–PV Arrays and other charging sourcesare connected to charge controller(s)rather than inverter–Most inverters can enable batterycharging from an AC generator
AC/DC systems Both AC and DC loads arepowered by the off-grid powersystem––DC loads powered directly frombattery outputAC loads powered by inverter orgenerator Requires separate AC & DCelectrical circuits Most common in Boats and RV’s––Note that mobile inverters havespecial grounding requirementsMobile inverters fall under adifferent UL listing
Hybrid systems Energy is produced by morethan one source, for instancePV and wind, or PV and hydro,or PV and a generator.
How does Off-Grid system design differfrom Grid-Tie system design?Grid-TieOff-Grid(Net-Metered) Energy production and PV arraysize based on annual consumption Energy production based on daily orweekly consumption Some energy used directly as it’sproduced, and some energy issent to the grid (stored as credit) Some energy used directly as it’sproduced, and some energy isstored in batteries PV array sized based on energyproduction during the darkest timeof year Inverter size based on peak ACload, not on array size More complex – many If the system fails, the lights go out Inverter size matches array size Simple – few long lastingcomponents If the system fails, the lights stayoncomponents
Off-Grid System Components PV array, engine generator, wind turbine, micro-hydro turbine, etc PV array combiner box (rapid shutdown system) Charge controller(s) Battery bank Battery-based inverter(s) DC switchgear and over-current protection AC switchgear and over-current protection Battery monitor and other system controllers
Off-Grid System Diagram
Off-Grid System SizingThe purpose of the off-grid power system is to providepower to run loadsSystem design begins with an analysis of the loads that need to be powered
User Information That You WillNeed to Collect Daily consumption (Watt-hours)–––How much energy will the application consume each day? Is it seasonal?For each load, multiply the power draw by the hours it is used per dayFor appliances, divide the Energy Star annual consumption kWh by 365http://www.energystar.gov/index.cfm?c products.pr find es products Peak load (Watts) and characteristics (VDC/VAC/Hz)––– Days of Autonomy (Energy storage)–– Sum of all loads that may be run simultaneouslySeparate AC and DC LoadsVoltage and frequency the loads requireHow many days in a row will the loads need to run with little or no sunDon’t neglect to account for snowSun-Hours per day during the darkest month (kWh/day)––This is the available solar resourceUse Winter Solstice time frame rather than annual average if loads will be runduring winter
Load AnalysisLoads Worksheet –request formFrom the AEE Solar Off Grid quote
Load AnalysisLoads Worksheet –Use kWhper yearfigure forWatt-hourcalculationRefrigerators and Freezers
Load AnalysisLoads Worksheet –Invertertare loss isa DC loadInverter tare loss
Load AnalysisLoads Worksheet –Total ACloads thatwill bepowered bythe inverter.This willdeterminethe invertersize.Total AC loads for inverter
Don’t Forget “Phantom” Loads123.5W x 24 hrs 2964 Wh/day
Load AnalysisLoads Worksheet –Total ACenergy kWhneeded to besupplied bythe system.Each columnfor a season.This is whatthe solar andbattery aresized to meet.Total AC loads for inverter
Load AnalysisLoads Worksheet –Daily energyconsumption 7397 Wh inwinter8511 Wh insummer8776 Wh inautumnPeak load -7153 W from theinverter8256 W from thebatteryExample
Site Analysis What is the solar energy potential at the site?–Insolation in kWh/m2/day (aka: Peak sun-hours) for each month–PV arrays for Off-Grid systems are based on the month with the largest load to solarresource ratio–Generally this will be peak during the darkest month of the year, not the yearlyaverage–Sometimes the greatest load will be in the summer for A/C–Shade or orientation issues–Mounting space Are there any other possible energy sources other than PV? –Wind or Hydro turbines can produce power when sunlight is not available and can addgreatly to the energy production reliability of off-grid systems–Recently it may be less expensive to simply add more solarHow many cloudy days in a row should the design be based on?–Most Off-Grid systems require some sort of back-up power, usually a generator, forextended cloudy weather or when snow covers the array.–How large a battery is affordable and how much generator run time is acceptable?
PV Array SizingNREL Red BookOut of print but charts are available online http://rredc.nrel.gov/solar/pubs/redbook/
PV Array SizingAEE Solar Catalog Maps In Reference Section inthe back of the Catalog These maps show thePeak Sun-Hours for thedarkest month of theyear NOT the yearly average They are useful forsizing off-grid systems,not grid-tie systems
PV Array SizingPV Wattshttp://pvwatts.nrel.gov/Use the Solar Radiationdata – Use the energyproduction figures onlywith correct de-ratesTilt and Azimuth can beadjustedYearly Average – 4.66December average – 3.22
Off-Grid PV Array Sizing Worksheetspages 9-11 (2018 edition) The Off-Grid SizingWorksheets in the AEECatalog is one method ofdoing system sizing. Using a spreadsheet thatyou put together will makethe task easier and faster‒ If you build your ownspreadsheet you will understandhow to use it There are third party sizingprograms available‒ Some of these have complexfinancial models also
PV Array SizingDe-rate factors Module power tolerance– Module temperature de-rate– This will vary through the year, but is usually in the 10% range. Less in thewinter and more in hot areasArray soiling– Though most modules are now -0/ 3% tolerance, some are still up to -5%Solar modules will gather dust, soot, moss, leaves, pollen, etc. Extremelyvariable, but even when the large stuff is cleaned off there may still becommonly an average of 5% reduction in power.Battery round trip efficiency–For a lead acid type of battery round trip efficiency is commonly 80% at best. Forlithium batteries it can be over 92%.–The limiting of solar production when the battery has a full charge should also beconsidered, but when the battery is full generally the loads have been satisfied,so there is little need to characterize it.
PV Array SizingLoads Worksheet –Daily energyconsumption – withinverter efficiencytaken into account forthe AC loads (87%)7397 Wh in winter8511 Wh in summer8776 Wh in autumnPeak load -7153 W from theinverter8256 W from thebatteryExample
PV Array SizingSample Calculations Power for a load of 7397 Wh/day is needed from the PV array, onaverage, in the winter months–Calculate the base array size using December insolation–Performance factor of 1.4 used, this is a very poorly defined number–Inverter efficiency was calculated in the load sheet (87% typical)–Traditional Performance factor, aka; array to load ratio, 1.2 when solar cost more The 4729 Watt base size is multiplied by de-rates for final array–Calculate the array using all of the de-rates
PV Array SizingResultsThe results can be calculated for the full year and graphed This graph is showing calculations for monthly totals
Battery SizingDesign Considerations The battery needs to store enough energy to power the loads duringperiods of low energy production – to average out weather conditions– Typically 2 to 3 days autonomy is used for most of the USA for residentialsystems, more for industrial systems without backup–––– Old school when PV was expensive this was often 5 to 7 days or moreWith only 2 or 3 days autonomy the use of a backup generator will be needed forextended cloudy periods, or when the array is covered with snowIn a system without generator backup this needs to be much longerHow much longer depends on what part of the country and if conservation canbe put into effect during cloudy periodsAs little as 1 day autonomy can be used but it will be hard on the batteryand will require substantial generator use–– This is called “days of autonomy”A battery must be chosen that can handle the maximum array currentThe battery will be cycled heavily so may have a shortened lifeA larger PV array can compensate for days of autonomy to some extent––––This is where the “Performance Factor” comes into playThe battery is likely to be a large part of the cost of the systemIt might be less expensive to substantially oversize the PV arrayThere are limited models to accurately figure how well this works or how tocalculate it
Battery SizingDepth of Discharge (DoD) Most batteries will last longest with a shallower daily DoD–––– Most lead acid batteries will have a shorter life if cycled daily more than 50%DoD, and will last longer with less DoD80% DoD is considered ok for occasional dischargesDays of autonomy can be calculated to 80% DoD or 50% DoDThe daily DoD can also be used as an alternative methodLithium batteries are intended to be cycled up to 90% daily––More often they last longest if cycled only 80% DoDFor off grid this heavy daily cycling would require extensive use of a backupgenerator
Battery SizingCapacity Battery capacity is measured in Amp-hours (Ah)– Capacity varies with rate of discharge–––– At a higher discharge rate a battery has less capacityAt a lower discharge rate a battery has higher capacityVery deep cycle batteries may be more effectedLithium batteries do not change muchResidential systems have extremely variable loads–– Lithium batteries are often measured in kWhGenerally the 20 hour rate is usedWhen a battery is sized for more than 3 days autonomythe 100 hour rate can be usedParallel strings of batteries–––Best practice is no more than 3 parallel strings for leadacidOne string is best. If retrorfit a 24V system 2 stringsallows conversion to 48V system laterLithium can be parallels in higher numbers depending onthe Battery Mgmt System
Battery SizingMaximum charge and discharge rates Maximum charging current––––– A battery with a higher rated maximum chargingcurrent will usually also handle a higher peak load– Batteries with lower internal resistance will have highercharge and load ratesThe battery needs to be able to supply the peak load–– Batteries can only absorb a charge at a certain rateThere is a large variation between battery typesLead Acid - low to highLithium - high to very highNickel Iron – very lowA discharge rate that is too high will cause the voltage todrop and the inverter to shut downThis maximum current is also time dependent, shorterlength draws can be higher current, longer draws must beat a lower rateGenerally for an off-grid system the battery is largeenough that the battery can handle both maximumcharge and discharge–For one day autonomy these may need to be considered
Battery SizingTemperature effects Temperature and capacity–– Low temperature limits––OutBack Power–– Capacity is reduced with lower temperatureMaximum charge and discharge rates are reducedat lower temperaturesLead Acid batteries can withstand -40 when fullychargedLead Acid batteries will freeze at the freezing pointof water when fully discharged, and must beoperated at higher state of charge at lowertemperaturesFlooded, AGM, or gel batteries makes littledifference, they do not survive freezingLithium batteries generally should not be chargedwhen below 32 F, but discharged at somewhatlower temperaturesHigh temperature limits––Lead Acid batteries lose ½ their life for every 13 Fhigher average operating temperatureLithium batteries are rated at up to 113 F, but havethe longest life if kept between 59 F and 77 F
Battery SizingSample Calculations Power for a load of 7397 Wh/day is needed from the battery bank Calculate the base capacity with days of autonomy, DoD, andtemperature de-rateInverter efficiency was calculated in the load sheet (87% typical) The 30821 Watt-hour size is converted to Amp-hours (Ah) Divide the Ah capacity by the battery nominal voltageGenerally for residential the 20 hour rate is used48 volts is used for this example and is most commonThe Watt-hour capacity is used to size a Lithium battery
Off-Grid Inverter Sizing Maximum AC load Identify any loads with high start-upor surge current draws‒ Identify and sum all loads that mayrun simultaneously‒ Sum up total Watts – this is theminimum inverter continuous powerrating required‒ Motors in pumps, compressors, andother appliances with large inductiveloads‒ Largest surge load determinesminimum inverter surge rating Identify any loads that may require240VAC‒ Most inverters used now havestandard 120/240 VAC split phaseoutput
Choosing System DC Voltage Selecting the best DC system voltage depends on a variety of factors:‒ Peak load - 12VDC is fine for peak loads up to about 1500W, 24VDC is fine for peakloads up to 3000W, 48VDC is best for peak loads over 3000W Size of PV array‒ A single MPPT 80A charge controller will handle up to 1000W of PV in a 12V system,but will handle up to 2000W in a 24V system, and up to 4000W in a 48V system Battery bank‒ Higher system voltage means more 2V cells in series so fewer parallel strings will beneeded to gain the same amount of energy storage Voltage of any DC loads‒ If there are DC loads, that may define what the system voltage should be, or DC-DCconverters can be used to supply power to those loads
Equipment – Modules and Racking Module Type: 36-cell, 60-cell or 72-cell‒ Cost, availability‒ Ease of installation how well they fit the installation space‒ Effect on equipment choices, 60-cell modules work best with some commoncharge controllers Racking‒ Roof mount – may not have the best tilt angle, but may have the bestexposure‒ Ground mount – Easier access, better tilt angle‒ Pole mount – Good access, tilt can be adjusted and can be made steep enoughto help shed snow in the winter
PV array combiner boxes Each parallel string of modules must have circuit protection‒ Most modules have a 15 A or 20 A max fuse rating‒ Under fault conditions, the array can be exposed to full current ofthe array breaker‒ 600V charge controllers generally have only one or two strings andwill not require circuit protection The fuses or breakers in these circuits must be rated for themaximum voltage‒ Breakers are available in 150 V or 300 V ratings, fuses up to 600 V All array circuits going to each charge controller musthave a separate and isolated feeder to that chargecontroller Some combiner boxes have the capacity for two separatecircuits‒ Multiple combiners may be more convenient for wire management Some combiner boxes will also have rapid shutdown and arcfault protection
Rapid Shutdown Required in 2014 National Electric Code for all PV systems‒ Section 690.12 says “PV circuits installed on or in buildings shall include a rapidshutdown function ”‒ 690.12(1) states that “Requirements for controlled conductors shall only apply to PVsystem conductors of more than 5 ft in length inside a building, or more than 10 ft from aPV array.”‒ 690.12(2) states that “Controlled conductors shall be limited to not more than 30V and240 VA within 10 seconds of rapid shutdown initiation.” Modified in 2017 NEC:‒ 690.12(B)(1) changes the definition of “array boundary” to 1 ft from the array.‒ Requires that “Controlled conductors located outside the boundary or more than 1 m (3ft) from the point of entry inside a building shall be limited to not more than 30V within30 seconds of rapid shutdown initiation.”‒ 690.12(B)(2) Starting Jan 2019 conductors within the array boundary will be limited to80V essentially mandating module level shutdown‒ By 2019 entirely new rapid shutdown equipment may take over the marketException: Ground mounted PV system circuits that enter buildings, of which the solepurpose is to house PV system equipment, shall not be required to comply with 690.12.
Rapid Shutdown Components OutBack ICS system‒ Includes Arc Fault protection in thecombiner box‒ Remote operated breaker todisconnect the charge control endof the circuit MidNite Solar’s Birdhouse, disconnecting combiners, andremote-trip breakers
Arc-Fault and Ground FaultProtection The 2017 NEC, 690.11, requires that“Photovoltaic systems operating at 80V orgreater shall be protected by a listed DC arcfault circuit interrupter”‒ The 2017 NEC does provide for an exception forcertain types of ground mounted array and solarpower shed. The OutBack ICS Plus system is currently theonly equipment listed to UL 1699B for arc-faultdetection and interruption for battery systems‒ Some charge controllers have built-in arc-faultprotection but are not currently listed to theapplicable UL Standard. The 2017 NEC, 690.41, requires that “DC PVarrays shall be provided with DC ground-faultprotection ”‒ DC ground-fault protection can be in the chargecontrol or a separate DC-GFDI breaker or device‒ The 2017 NEC does provide for an exception forcertain types of ground mounted arrays and solarpower shed.
Controller typePWM or MPPT Charge controller type: PWM‒ Pulse Width Modulated (PWM) charge controllers,inexpensive, compact‒ Array must match battery voltage, 12V nominal modules 36-cell, 24V nominal modules 72-cell, multiples in seriesare used for 48V systems‒ Does not track the maximum power of the array, does notchange the array voltage which is the same as the batteryvoltage Charge controller type: MPPT‒ Maximum Power Point Tracking (MPPT) charge controllersuse any modules, but 60 cell modules work better than 36cell or 72 cell modules for 150 V controllers‒ MPPT maximize energy production up to 30% in winter‒ Operates array at maximum power point voltage. Arrayvoltages up to 150, 200, 250, 300, or 600 VDC‒ Converts the higher array voltage to battery voltage
MPPT Controller string sizingwith 60-cell Modules String operating voltage must be between battery charging voltageand the controller upper limit Power will drop off dramatically if the peak power point of the arrayfalls below the battery charging voltage 150VDC limited charge controls‒ A 48 VDC battery charges at 56 VDC or more‒ Two 60-cell modules x 27.5 VDC (at high temperature) 55 VDC, not countingvoltage drop or module degradation which will make it worse, so two 60-cellmodules in series will typically not do well to charge a 48 VDC battery.‒ Most 60 cell modules will exceed 150 VDC in strings of 4 at low temperatures‒ Some charge controls will take higher than rated voltage, but will usually not beoperating when over voltage Higher voltage charge taketaketakeupupupuptotototofour 60-cell modules in seriesfive 60-cell modules in seriessix 60-cell modules in series13 60-cell modules in series depending on power
MPPT controllersMaximum power Total power should generally not exceedwhat the charge controller can process‒ The solar array will rarely be able to put outmore than 87% of the nameplate rating‒ High altitude sites may have to downsize thearray per charge controller‒ Some charge controllers can have larger arraypower and will simply limit the output andleave the balance unprocessed‒ Some charge controllers are not tolerant ofhigher array power
Charge Controller BOSController Circuit Protection Disconnects and circuit protection are required between the PV array and thecharge controller, and between the charge controller and the battery A circuit breaker is normally used for up to 300 VDC PV input circuits tocontroller‒‒‒ This breaker must be sized for 156% (125% x 125%) of Isc of array (STC)Breaker not to exceed the maximum input amperage rating for the charge controllerWire between breaker and the combiner box must meet or exceed the current rating ofthe breaker usedA DC rated disconnect is used for 600 VDC rated circuits‒‒This is sized for 156% (125% x 125%) of Isc of array (STC)Often these have only two strings so the code exception can be used and no circuitprotection is neededThe charge controller breaker and disconnect serves as the battery breaker‒‒‒If it matches the charge controller output rating it must be rated for continuous dutyIf not rated for continuous duty at full amperage, size to 125% of max currentIf the charge controller will be operated near its limit, oversize the battery breaker toavoid nuisance tripping
Battery OptionsLead-Acid types Flooded Lead-Acid‒‒‒‒‒ Robust for Lead AcidHigh maintenanceIsolation, spill containment and ventilation requiredMust be regularly fully chargedCarbon enhanced better at partial state of chargeoperationVRLA Lead-Acid – AGM or Gel‒ Sealed - very low maintenance‒ Can have cycle life that matches flooded‒ Must be regularly fully charged VRLA Lead-Acid AGM Carbon enhanced‒ Nano-carbon is used in the negative plate‒ Substantially reduces the effect of sulfation‒ Good partial state of charge operation VRLA Lead-Acid Gel tubular plate‒‒‒‒DIN standard is OPzVSealed – very low maintenanceVery high cycle life, 2500 to 3000 cycles at 50% DoDMust be regularly fully charged
Battery OptionsLithium and Others Lithium Iron Phosphate (LiFePO)‒‒‒‒‒‒‒‒‒‒ Lithium-ION NMC‒‒‒‒ Resistant to thermal runaway or fireHigh energy density up to 35 Wh/lbHigh efficiency up to 92% round tripPartial state of charge operationLong life at high cycle depthOver 4200 cycles @ 90% DoDWorks with most 48 volt nominal invertersExpensive but long life tradeoffOperates between 32 F and 113 F, preferred between59 F and 77 FSome have Canbus or Xanbus communicationsMostly made for grid tie with energy managementMay not be approved for off grid useMore complex battery management system for safetyLess expensive than LiFePOOthers‒‒‒‒Other Lithium-IONNickel CadmiumNickel IronAquion
Battery Bank WiringSeries and Parallel Series connection:‒ Voltage is additive -rated Ah capacity remains same Positive of Battery 1 is connected to negative of Battery 2 andso on Example: Two 12V, 220Ah batteries in series will yield a24V / 220Ah battery bank Parallel connection:‒ Capacity is additive - DC voltage remains same The positives are connected to each other, same for negatives Output leads must be from first and last battery for electricalbalance Manufacturers typically limit maximum number of parallelstrings to three Example: Two 12V, 220Ah batteries in parallel will yield a12V / 440Ah battery bank
Types of Off-Grid Inverters Modified Square-Wave (Modified Sine-Wave)‒‒‒ Sine-Wave inverters‒‒‒ Designed for stationary installations, such as homes and businesses.Should be Listed to UL 1741Mobile inverters‒‒‒ The most commonly used in residential and commercial systems.Have very clean power output that will run almost any AC load.Typically have a total distortion of less than 5%Residential inverters‒‒ Inverters are inexpensive, but have a non-sinusoidal wave formVery efficient, but some loads cannot be run on themTypically have a total distortion of up to 30%Designed for RV and marine use.Have “ground switching” which allows for the system’s neutral/ground bond to either beinside the inverter, or outside in the “shore power” connection.Should be Listed to UL 458Inverters may or may not have built-in battery chargers for chargingbatteries from an AC source, such as a a generator.
Inverter SystemsPoints to Consider A central location is needed to connect wiring and install breakers‒ There needs to be a DC load center and an AC load center, or one load center forboth AC and DC.‒ These systems are for indoor mounting only A battery-based inverter can have a very large current draw‒Especially when battery voltage is lowerThe main DC breaker for these inverters are rated for 125A to 250A‒‒The inverter manufacturer or supplier will generally specify breaker sizesBreaker size is generally maximum power output in watts divided by battery voltagex 1.5, but sometimes largerWire size for battery and inverter circuits willcommonly be AWG 2/0 or AWG 4/0 cable‒‒‒Keep connection as short as possible to minimizevoltage dropUnder 10ft is bestIf over 5ft the 2014 code requires a disconnect andcircuit protection at the battery
Integration Hardware Over-current devices – breakers andfuses DC Ground-Fault Protection (GFP) Bus Bars Combiner boxes Grounding Generator Start Controls Amp-Hour Meters System Control and Monitoring
System Monitors & Controllers Automate battery management‒ Allows you to adjust the bulk, absorption, float and equalization chargetiming and voltage set-points Turn on/shut off generators according to time of day or batterystate of charge May allow for remote monitoring/control via Internet May track battery state-of-charge through amp-hour meteringEvery off-grid systemshould have an amp-hourmeter or battery monitorinstalled!
Pre-Assembled Power Systems Factory pre-wired power systems simplifydesign and installation‒ Several common sizes & configurations are available Most Power Systems include:‒ Inverter(s)‒ Controller and networking devices‒ Battery monitor‒ Integration hardware and BOS- Enclosures, Breakers, GFDI, Bypass, etc.‒ Charge controller(s)
System Example Using our previous example‒ Array size 7.4kW‒ Battery size 642Ah at 48V‒ Inverter size 7.2kW Module and racking choices‒ 300 watt 60-cell modules are what you can get at a good price andavailability‒ 7400 Watts / 300W modules 24.67 modules‒ Since 24 modules is a nice number for both racking and stringing, and theperformance factor is generous, I’d choose that number of modules‒ Array needs to be installed 250 feet away from the power system‒ System will be in a snow zone in Vermont so a steep tilt will be needed‒ A ground mount or pole mount will be needed‒ An easily adjustable-tilt pole mount will allow a vertical setting for snowstorms and can be adjusted to a lower tilt to optimize seasonally
System Example Using our previous example - Array size 7.4kW - Charge controller choiceBattery size 642Ah at 48V -Inverter size 7.2kW‒ Array is 250 feet from the power system‒ Trade off between cost of high voltage charge control andcost of wire‒ A 7.4kW array 250ft away with one string of 12 modulesin series, operating at 320 volts to each 600V chargecontroller, will only need two circuits using #10 copperwire at 200‒ That array with two parallel strings of 6 modules in series,operating at 160 volts into each 300V charge controller,will need two circuits using #4 copper wire at 800‒ That array with four parallel strings of 3 modules inseries, operating at 80 volts to each 150V chargecontroller, will need two circuits using #2/0 copper wire at 2400‒ Which inverter is used may have an effect on the choiceof charge controller and vice versa.
System Example Using our previous example Inverter choice-Array size 7.4kW -Battery size642Ah at 48V -Inverter size 7.2kW‒ Iterations between inverter, charge controller, array‒ Using the same inverter and charge controller will allow forone monitor and control and potentially coordination betweenthem‒ In an off grid system coordination between charge control andinverter is less important than for a grid tied system‒ Looks like an OutBack 8kW Radian inverter is just right‒ If not all the loads need to run at the same time, maybe only6kW is needed, then the Schneider XW 6848 would be fine‒ If more power might be needed in the future, maybe twoSchneider XW 5548 inverters could be used‒ If a more economical system is desired maybe two MagnumMS4448PAE inverters could be used‒ Does one of these choices work
Off-Grid PV Array Sizing Worksheets pages 9-11 (2018 edition) The Off-Grid Sizing Worksheets in the AEE Catalog is one method of doing system sizing. Using a spreadsheet that you put together will make the task easier and faster ‒ If you build your own spreadsheet you wil
energy efficei ncy technologies 4. th. patent in development (dx) certifications & acronyms defined. cem certified energy manager (aee) crm carbon reduction manager (aee) cea certified energy auditor (aee) pem professional energy manager (unibes) nemi national energy management institute (smwia) cxa
pen or colored pencil. Then, grid the paper or illustration board you will draw onto. If you double your grid to a 1” grid for your final it will be 16” x 20”. Grid your final with pencil. You may use any size grid (the smaller the grid the more detail), but your final will be between 16” x 20” to 18” x 24. The grid should be 1 to 1.
Version 12.01.2018 v.LiNK Video-inserter VL3-MIB-4 . Read the manual prior to installation. Technical knowledge is necessary for installation. The . Audi Q7 (4M) MMI 7“ OFF OFF OFF OFF Porsche OFF OFF OFF OFF VW Touran OFF OFF OFF OFF Audi TT (8S) ON OFF .
Falk Steelflex Morse/Browning Grid-Flex Dodge Grid-Lign Kop-Flex Kop-Grid Falk Steelflex Morse/Browning Grid-Flex Dodge Grid-Lign Kop-Flex Kop-Grid 1020 1020T10 GF2020H 1020T10 1020H 1020T20 GF2020V 1020T20 1020V 1030 10
The vGPU types supported by GRID K1 and K2 are defined in the Table 1. Card No. of Physical GPUs Virtual GPU Types Intended Use Case Max Resolution No. of vGPUs per GPU No. of vGPUs per Card GRID K1 4 GRID K140Q Workstation 2560x1600 4 16 GRID K100 VDI 1920x1200 8 32 GRID K2 2 GRID K260Q Workstation 2560x1600 2 4
with grid increments of 202.5, 67.5, 22.5, 7.5 and 2.5 meters. Each grid has 90 horizontal grid points and 60 vertical grid points, except for the coarsest grid which has 70 vertical grid points. The Rayleigh friction layer is included at the uppermost 10 levels of the coarsest grid. The lateral boundaries are periodic. A schematic of the .
Therefore, DSM in smart grid is more extensive than the traditional power grid. 1) To achieve a good interaction between the grid and the user The main characteristics and the goal of building the smart grid is to realize the "intelligent interactive",DSM in Smart Grid is no longer a simple power management, the power grid enterprises
June 1982 concerning certain products used in animal nutrition(6), should be included as a category of feed additives and therefore transferred from the scope of that Directive to this Regulation. (13) Implementing rules concerning applications for authorisation of feed additives should take into account different documentation requirements for food-producing and other animals. (14) In order .
