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 Final Design: Load Levelling with Data Center BatteriesSam Osheroff, Wolfgang Shi, Alex SimmonsCEE 315 Dr. SchaadSummaryIn order to implement load levelling with reused data center batteries for a solar power array, a comprehensive system is required to provide the infrastructure for control over intake and delivery of power. This design uses the Magnum brand of home solar energy products to intake energy from an outside source - here a solar array - store it in the batteries, and supply energy in response to some load from both the batteries and the input source. The load levelling aspect is incorporated in the controls on the intake and output of energy using Magnum’s in-house charge controller and system remote, along with various monitoring tools. An experiment is included for ascertaining the viability of battery use with the solar energy system components in a controlled setting before consumer implementation. With the requisite elements connected properly, this system is capable of mediating supply from an energy source with loading demand via reused data center batteries in a manner consistent with load levelling principles.General DiagramsBasic System FlowchartElement-Based System FlowchartDetailed System FlowchartCircuit Schematic: General Input to Output with Battery Bank, Inverter, Charge ControllerCircuit Schematic: Charge Controller specifics with Inverter, Battery BankCircuit Schematic: Inverter to Battery with Remote, Battery Monitor Element DiagramsPT-100 Charge ControllerMountDimensionsWiringMagnum MMP mounting plateMMP175-60SFeaturesDimensionsMMP wiring: <30V case, Terminal BlowupsMS2812 Inverter: DimensionsWiring schematic to Battery BankMagnum Energy ME-ARC Inverter Remote‘Accessory DiagramsME-BMK Battery MonitorDC breakerSmart Home Specific Element: Load DiversionChosen Controller: Magnum ACLD-40Pictorial Flow ChartCircuit Flow ChartCircuit Schematic: Inputs to MMP, ACLD-40, loadsCircuit Schematic: Terminal Block BlowupsParts ListItemCostWebsite LinkPT-100 Charge Controller925 HYPERLINK "; BP-MMP103.2 HYPERLINK "; HYPERLINK "; Inverter1925 HYPERLINK "; Energy ME-ARC Inverter Remote225 HYPERLINK "; Battery Monitor170 HYPERLINK "; Breaker?? HYPERLINK "; Energy ACLD-40 AC Load Diversion Controller630 HYPERLINK "; cost:4689.4JustificationAfter considering multiple brand options, the Magnum brand was chosen to provide all of the core elements for this system. In addition to having an entire system’s worth of components in house, the scale at which their components operate matched the closest with the intended scale of the project, using comparatively low voltage batteries to provide the type of power draw demanded by a home. Finally, the interconnected nature of their monitoring and control systems allows for load levelling to be directly applied through their onboard controller, rather than necessitating the implementation of some extraneous controls.The PT-100 Charge Controller was the only component of its kind in the Magnum inventory, so by necessity, it was chosen. The charge controller optimizes the amount of power transferred from the PV array to the batteries by regulating output current and battery voltage while operating at the maximum power point of the array.The BP-MMP was included to allow for the MMP enclosure assembly to be easily mounted.The MMP175-30s was chosen mainly for its specs, as its operating voltage of 12VDC and source current of <30A fit the requirements of the proposed application to solar panels in the smart home. In addition, the accessibility of the controls and the pre-wiring for straightforward implementation played a role in choosing this enclosure. The enclosure serves as a go-between for the major components of the inverter, batteries, charge controller, external power supply, and remote, with sensor inputs, disconnects and breakers.Choosing EnclosureThe MS 2812 was chosen as the inverter for its compatibility with other elements, appropriate input and output voltage, and high output power given the operating voltage: 2800 W at 12V DC. Also, a pure sine wave inverter was chosen over a modified sine wave inverter so as to maximize compatibility with the variety of newer technological devices in the Smart Home. The inverter converts between AC current, characteristic of the source power supplied to the system and load demanded of the system, and DC current, characteristic of battery input and output.The ME-ARC Inverter Remote was chosen for its wide compatibility with Magnum products, advanced level of control, and ability to communicate with other system components via accessory and built-in Magnum sensors. The remote controls the input to and output from the battery using a wide variety of settings that may be programmed in by the user.The ACLD-40 Load Diversion controller was included because of its necessity for moderating the load delivered to the batteries in the application context of the smart home. Though there are a number of options for ensuring that batteries do not become overcharged in a solar energy system, the Load Diversion controller provides the optimal solution by diverting excess energy not being stored in the batteries to serve household uses such as heating water or providing energy to the AC while tailoring the input energy directly to the specific needs of the battery bank. No energy is lost in the conversion from AC to DC when regulating battery voltage, as the ACLD-40 dissipates energy on the AC side rather than the DC side. In addition, the ACLD-40 bolsters the solar energy system with the ability of the inverter to function in the event of a utility power outage without significantly dropping in efficiency.The rest of the components were chosen for their specific value as accessories. The circuit breaker is an add-on to the MMP for extra safety in the ability to break the battery circuit if overloaded, and the battery monitor enhances the ability of the remote to regulate battery input and output based on battery performance over time.TablesPower provided by inverterAllowed PV Input Based on Battery Bank VoltageEnergy Production and Usage of the Duke Smart HomeVoltageEnergy RateSolar Panel Energy Production12 V8.3 kWh/ daySmart Home Energy Use120 V88.2 kWh/dayMMP175-30s Wire SizingMS2812 Inverter DC Wire/Overcurrent Device for Rated UseMS2812 Inverter DC Wire Size for Increased Distance Inverter 2812 AC Input/Output Wiring ConfigurationsInverter 2812 AC Grounding Electrode Conductor SizingBattery Bank SetupThe batteries that the battery bank will be consisted of are used valve-regulated lead acid batteries (VRLA) from Duke’s Data Center. These specific batteries are EnerSys’ 12HX400 VRLA batteries which have a nominal voltage of 12 V. Tests have been performed on these batteries to determine their capacity to hold charge, as well as how quickly they can discharge stored energy. Results of these tests have shown that the used VRLA batteries are functionally quite similar to healthy batteries, suggesting they can be used in capacities after their life in the Duke Data Center. These used batteries are the batteries that will be implemented in the proposed design.To ensure that the battery bank outputs the 12 V of electricity to the inverter when necessary, the batteries will be connected in parallel. This design choice is preferred in the case that any battery fails. If one line of the parallel circuit fails, the other batteries will still be able to provide the necessary voltage. Any design choice that does not account for possible failures of batteries was rejected in order to reduce the probability of failure. The parallel circuit structure was decided upon due to its ability to resist failure. If the batteries were connected in series, then not only would they be outputting electricity at a voltage that the inverter is not designed for, but they would also be more likely to cause a system failure. If a single element of a series circuit fails, then the whole system fails.It is important to arrange for a suitable installation of the battery. In large systems a separate battery room can be recommended. In smaller systems part of an existing room may have to be used. When the batteries are placed on a floor, materials, which are not affected by acid leakage, shall be used and the batteries shall be placed in a way to permit easy management and service. It is also important to be able to clean the floor space with water.For small systems battery boxes are available that take care of possible acid and water spillageand also gives protection from direct electrical contact with the battery terminals when theinstallation is finished.Load Levelling To achieve the goal of load leveling at the Smart Home, the Magnum Energy ME-ARC Inverter Remote was chosen as the monitor and moderator of the circuit. The natural reason behind this choice is that it is compatible with all the Magnum energy equipments that have been chosen previously by the group. More importantly, the remote includes LED indicators for inverter/charger status and allows programming of the inverter and charger. Settings on this remote can regulate the various elements of the circuit and allow for the load leveling of the Duke Smart Home. Attached below is a figure of three different electric load modes the Magnum Energy ME-ARC Inverter Remote can achieve for the sake of load leveling. The three modes shown here are designed to suit the different electricity usage condition of the Smart Home. Shown in figure 3-6 is the inverter mode, it is used when the electricity load of the Smart Home is relatively low. In this mode, AC current from either the solar panel or the power grid is completely shut down and the VRLA batteries become the only source of electricity for the Smart Home. Under such scenario, 12-volt DC electricity from the batteries goes through the inverter and turns AC to support the power usage of the Smart Home. An important notice about this mode is that it should be activated only when the batteries are charged and their output surpasses the need of the Smart Home. Shown in figure 3-7 is the standby mode, it is used when the electricity load of the Smart Home is at an intermediate stage. In this mode, AC current from either the solar panel or the grid charges the VRLA batteries through the inverter while powers up the Smart Home. In this case, the batteries do not generate any outputs to the Smart Home and the AC current is the only source of electricity for the Smart Home. Significantly in this case, the power provided by the AC current should surpass the need of the Smart Home even when it is charging the batteries at the same time. Shown in figure 3-8 is the load support mode, it is used when the electricity load of the Smart Home is relatively high. In this mode, AC current from either the solar panel or the power grid and the VRLA batteries power the Smart Home at the same time. For this scenario, 12-volt DC electricity from the batteries goes through the inverter and turns AC to support the input from the AC current in providing electricity for the Smart Home. This mode is activated when the Smart Home is at its peak load demand and the 12-volt batteries are well charged. In order for the Magnum Energy ME-ARC Inverter Remote to switch the circuit between those three modes and achieve load levelling, proper setups are necessary. Out of the four modes of ACIn control methods, Time Connect and SOC Connect should be chosen. Using Time Connect the AC current can be set to connect at particular periods of a day, when the average electricity load of the Smart Home is at intermediate or high demand based on historical data. Enabling SOC Connect makes sure that the AC current from the solar panel will support the batteries when they are at low state of charge and cannot power the Smart Home alone. Out of the three charge control modes, Start Afloat should be selected as the default mode for this circuit. This selection restarts the Float charge cycle from any stage in the charge cycle as long as the charger is active and best suits the condition of the Smart Home where solar energy is idealized the only AC current provider. Attached below is a current/voltage plot of the circuit when Start Afloat is chosen as the charge control mode. Since this circuit does not involve a backup generator, Gen Control will be set to default in this case. For the PT charge controller settings, the battery type will be set to default. Absorb and afloat Volts will be set to default as well since the VRLA batteries used for this task is 12-volt batteries. Properly setting up the Magnum Energy ME-ARC Inverter Remote enables load levelling for the Smart Home. It drains the energy stored in the VRLA batteries when load demand is relatively low or relatively high (as a supplement for AC current in this case). It also controls the charging of the batteries when their state of charge is low and the AC current alone can support the need of the Smart Home.Experiment designPurpose:To determine if old data center VRLA batteries can be used for load levelling with PV array power, a simulated home solar energy system setup, and an experimentally controlled variable load.Materials:PV array (supplied in laboratory)Old data center VRLA batteries (supplied in laboratory)PT-100 Charge Controller (to be purchased)MMP175-30s mounting enclosure for breaker wiring (to be purchased)***MS2812 Inverter (to be purchased)ME-ARC Inverter Remote (to be purchased)#2 Phillips screwdriver PliersWire strippers Drill and drill bits Pencil or marker Multimeter#2 -3 Slotted screwdriverTorque wrench Hammer LevelExtra copper wire rated for 187 F20 x 100W, 110 V lightbulbsOTHER MATERIALS FOR THE EXPERIMENT***It is possible to replace the MMP175-30s mounting enclosure with the following critical elements and still, in theory, perform the experiment fully. However, this version of the experiment poses more risk to the system components, as the system in this configuration lacks a DC disconnect to regulate the connection between the battery and the inverted, and the breakers used may not have the same specs as those used proprietarily by Magnum.4 busbars (Battery+, PV+, negative, ground)1 shunt4 breakers2 terminal blocksSetup procedures:Choose one of the following sub-options for the experimental setup, based on accepted risk to batteries/system components and available resourcesOption I: (With MMP Enclosure): Assemble the solar power system side of the experimental setup as dictated in the diagrams B-E, following the instructions given in the Owner’s Manuals for the four Magnum Energy parts.Option II: Assemble the solar power system side of the experimental setup as dictated in diagrams B-E, REPLACING the critical elements highlighted in the diagrams with the independently purchased elements described above. Assemble the applied load side of the experimental setup as dictated in diagrams #X-Y.Connect the AC HOT OUT, AC NEUT OUT, and GROUND wires from the solar power system side to the applied load side to create the full experimental setup.Cost:Option I: With MMP EnclosureItemCostWebsite LinkPT-100 Charge Controller925 HYPERLINK "; HYPERLINK "; Inverter1925 HYPERLINK "; Energy ME-ARC Inverter Remote225 HYPERLINK "; cost:3786.20Option II: With independently bought productsItemCostWebsite LinkPT-100 Charge Controller925 HYPERLINK "; Inverter1925 HYPERLINK "; Energy ME-ARC Inverter Remote225 HYPERLINK "; x busbars90.6 x shunt28.29 x 30 A breakers42.36 x 175 A breaker87.00 x terminal blocks3.56 gauge wire x 10ft20.00 cost:3346.81Savings over using MMP:439.39Risk analysis:The components that stand the most risk from circuit overload conditions due to breakers or disconnects not functioning properly, as is a slightly higher possibility with option 2, are the battery (batteries) and lightbulbs, followed by the inverter and finally the charge controller. Though the batteries were procured from the data center at no cost, the market price for the same model is about $281.89, which was used in the cost benefit calculations.Failure Modes: Option IIFailure ModeElement(s) AffectedLikelihood (estimated, over the course of the experiment, that the failure mode damages the given component)+/- busbar connection interruptednoneVery Low (<5%)Ground busbar connection interruptedAllVery Low (<5%)BAT + Breaker failsCharge Controller, Battery Low (5%)PV + Breaker failsCharge ControllerVery low (<5%)Power draw from inverter overloads positive end of batteryBatterySomewhat low (10%)DC shunt failsBattery, InverterSomewhat Low (10%)Terminal blocks failnoneSomewhat Low (10%)AC Breakers failLightbulbsModerate (20%)Weighted cost with risk: Option 2ComponentEstimated likelihood of risk posed to componentCost of componentWeighted extra cost (Cost x Risk)Savings due to not using MMPWeighted aggregate (savings - weighted cost)# of replacements before savings are outweighed by gross costVRLA BatteryModerate (25%)-$281.29-$70.322LightbulbsModerate (20%)-$80-$166.75 x 20InverterSomewhat Low (10%)-1925-192.51Charge controllerLow (5%)-925-46.251TOTALS-325.07439.39114.32The weighted aggregate savings, an estimate of how much is expected to be saved while factoring in risk, is around ? of the value of savings before risk calculation. In addition, this value only represents about 3.2% of the mean cost of the two options (12.5% before subtracting the weighted aggregate cost). In addition, while the lightbulbs can be replaced multiple times in the event of a failure mode before putting a dent into the marginal savings from this option, the battery can only be replaced a maximum of one time before outweighing savings, while the other Magnum components are so expensive that even one replacement would far outweigh savings. As such, this risk analysis deems option I to be the better selection to prioritize risk minimization over marginally small savings.Experimental methods and analysis:In this experimental setup, the solar panel array is the only source of the power for the circuit. The solar panels are connected to a load control unit, which consists of a PT-100 charge controller, a MMP175-30s mounting enclosure for breaker wiring (or a stripped down version of the components included therein), a MS2812 Inverter and a ME-ARC Inverter Remote. The load control unit is used to arrange electric power flow in the system, which eventually serves the purpose of load leveling. Other than the solar panels, the load control unit is also connected to the VRLA batteries and the experimental load.To mimic the power load situation of Smart Home, 20 light bulbs (100W) of the same configuration are used as experimental load. During the experiment, those common 110V light bulbs are connected in parallel. Each circuit branch with a light bulb is also configured with a switch as shown in Figure F. To test the performance of the circuit under different load conditions, the group uses 5 light bulbs to indicate low load condition, 10 light bulbs to indicate normal load condition and 20 light bulbs to indicate high load condition. All the light bulbs are connected to AC power before the experiment to test if they function correctly.Therefore, the three load situation of the experiment will require the following powerPlow demand=5×100=500WPnormal demand=10×100=1000WPhigh demand=20×100=2000WSince the solar panel need to support high demand alone when the VRLA battery is being charged up, the solar panel configuration for this experiment should be above or equal to 2kW level.Since the VRLA batteries will need to support the low demand alone to reach the load support purpose, the design team expects the battery to be able to output at least 500W of power at a given moment. In the first part of the experiment, the design group aims to determine the charge storage and release capability of the used VRLA batteries. For this purpose, the group charges up the battery with panel panel, then cuts off the AC power coming from the solar panel using the charge controller and connects the charged battery to a light bulb (through the inverter). If the light bulb lights up, that demonstrates the power storage and release ability of the VRLA batteries.To test the load leveling design of this circuit, the Magnum Energy ME-ARC Inverter Remote is chosen as the monitor and current moderator of the circuit. The natural reason behind this choice is that it is compatible with all the Magnum energy equipments that have been chosen previously by the group.Attached below is a figure of three different electric load modes the Magnum Energy ME-ARC Inverter Remote can achieve for the sake of load leveling.Shown in figure 3-6 is the inverter mode, it is used for the low load condition. In this mode, AC current from the solar panel is completely shut down and the VRLA batteries become the only source of electricity for the circuit. Under such scenario, 12-volt DC electricity from the batteries goes through the inverter and turns AC to turn on the light bulbs (load support).Shown in figure 3-7 is the standby mode, it is used when the electricity load of the circuit is at an intermediate stage(normal load). In this mode, AC current from the solar panel charges the VRLA batteries through the inverter while powers up the light bulbs. In this case, the batteries do not generate any outputs to the circuit and the AC current is the only source of power. Significantly in this case, the power provided by the AC current should surpass the load of the light bulbs even when it is charging the batteries at the same time.Shown in figure 3-8 is the load support mode, it is used when the electricity load is relatively high(high load). In this mode, AC current from the solar panel and the VRLA batteries power the Smart Home at the same time. For this scenario, 12-volt DC electricity from the batteries goes through the inverter and turns AC to support the input from the AC current in providing electricity. This mode is activated when the circuit is at its peak load demand and the 12-volt batteries are well charged. In order for the Magnum Energy ME-ARC Inverter Remote to switch the circuit between those three modes and achieve load levelling, proper setups are necessary. Out of the four modes of ACIn control methods, SOC Connect and Time Connect should be chosen. Enabling SOC Connect makes sure that the AC current from the solar panel will support the batteries when they are at low state of charge and cannot power the Smart Home alone. Time Connect allows the group to direct the power input and output of the circuit according to the experimental load.Out of the three charge control modes, Start Afloat should be selected as the default mode for this circuit. This selection restarts the Float charge cycle from any stage in the charge cycle as long as the charger is active and best suits the condition of the Smart Home where solar energy is idealized the only AC current provider. Attached below is a current/voltage plot of the circuit when Start Afloat is chosen as the charge control mode.Since this experimental circuit does not involve a backup generator, Gen Control will be set to default in this case. For the PT charge controller settings, the battery type will be set to default. Absorb and float Volts will be set to default as well since the VRLA batteries used for this task are 12-volt batteries. During the experiment, the design group needs to properly utilize the Magnum Energy ME-ARC Inverter Remote to enable load levelling test of the circuit. If the circuit functions normally under the design targets, the inverter remote will drain the energy stored in the VRLA batteries when load demand is relatively low or relatively high (as a supplement for AC current in this case). The circuit will also be able to control the charging of the batteries when their state of charge is low and AC current alone can support the load of the circuit.Supporting DiagramsFigure A: General wiring schematic, input sideFigure B: Wiring between PV Panels, Charge Controller, Inverter, and Load Figure C: PV Array to charge controller and battery bank (detail view) Figure D: Wiring from Battery Bank to Inverter Figure E: Remote control to inverter attachmentFigure F: Experimental Setup with PV, inverter, battery bank connected to light bulbs in parallel ................
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