Processing, December 2020

DECEMBER 2020 www processingmagazine com 29 The resulting solution would use commercial off theshelf COTS elements to the greatest extent possible However significant electrical mechanical design and software configuration would be necessary to achieve a cohesive design An integrated solution A solar battery design was the natural solution for creating a self powered system capable of being connected to backup generator or shore power when available Solar panels are available in ratings from 25 to 400 watts and can be combined to increase output Industrial electronics commonly operate at 24 Vdc so charging and battery systems are arranged to produce that voltage Lithium ion batteries are often used to power consumer electronics and electric vehicles However for off grid service the team determined that lithium iron phosphate LFP batteries provided a better combination of features performance and long term stability One 10 kilowatt hour LFP battery delivers about 400 amp hours of 24 Vdc power with the capability of being 100 discharged Traditional 12 Vdc lead acid technology which can only withstand a 50 discharge would require 16 or so 100 amp hour batteries to achieve similar output LFP batteries carry a 10 year expected lifetime resulting in lower lifecycle costs than lead acid batteries which must be replaced more frequently Reduced space requirements and wiring costs further improve the value proposition Figure 2 A Schneider MPPT 60 150 charge control ler enables the solar panels to optimally recharge the batteries while a separate IOTA DLS27 40 battery charger can perform this task when a generator is connected The charge controller is an intelligent device which communicates to the automation platform using Modbus TCP For most cases it is preferable that all off grid loads be DC so they can run directly from the batteries AC power can be generated by an inverter if needed although this introduces some additional costs and inefficiencies For the automation platform numerous programmable logic controllers PLCs and human machine interfaces HMIs operate at 24 Vdc Similarly many industrial duty Ethernet networking devices and edge gateways operate at this voltage making it possible to network all the intelligent devices together and establish communications with cloud based systems Figure 3 Cloud connectivity may be established with local wired or Wi Fi networking or by cellular capability via LTE or GSM So long as the edge located system can be networked to the internet data can be communicated to the cloud The team selected the industry standard MQTT communications protocol for publishing data up to a cloud based broker and for subscribing data back down to the PLC The edge gateway can act as the MQTT interface and now many PLCs have natively incorporated MQTT At the local site Modbus TCP and EtherNet IP enable connectivity to any smart devices Creating a secure cloud based software platform tying together all the automation elements was the most complex portion of the development This software resides on Amazon Web Services AWS servers with the MQTT broker and is fully supported by Quantum It provides a way to configure the data gathering analytics and visualization so a complete IIoT solution can easily be created and maintained Another characteristic of off grid installations is the typically harsh environmental conditions of heat sun exposure and dust Air conditioning requires too much power and is thus not an option for solar powered designs so all components must be rated to withstand the elements Sometimes installations can be fixedlocation either on a concrete pad or a pole However the ability for more portable designs may be desirable for the application or at least easier to install While addressing these details Quantum has created a portfolio of solutions that can work together or individually as needed QSolarBattery integrates solar panels with energy storage batteries QRTU provides the monitoring automation visualization and wireless connectivity hardware platform There are currently 36 configurations with options for using many major PLC and edge gateway vendors QCS IIoT is a cloud based solution which gathers data from any number of sources using the industry standard MQTT protocol logs it in the cloud enables analysis and delivers visualization to any web browser With these solutions in hand the team has found many opportunities to apply its off grid expertise Landfill water treatment application Landfill sites collect stormwater runoff into large basins for treatment before release downstream Small fractional horsepower variable speed pumps are modulated by PID loops based on flowmeter inputs to precisely dose coagulant and flocculent chemicals into the stormwater streams that collect into the basins One end user wanted a packaged skid to accomplish this The skid would generally remain in position for long periods of time but had to be easily relocated For this situation the solar battery solution was ideal Two LFP batteries were recharged by 1125 watts of solar power to provide up to three days of autonomous power for chemical pumping sufficient for the system to run for up to three days of minimal solar power which might happen during a long rainstorm A control panel included an AutomationDirect Productivity1000 stackable PLC for performing equipment and PID control with a C more HMI for local operator visualization The HMI was used for local setup but more important was cloud connectivity which enabled remote data logging dashboards and supervisory operation of multiple skids Because typical trailer based skids may need the solar modules to be stowed during high winds the team pursued a custom skid design to hold all the solar panels batteries associated control panels and pumps with a rain protected area for a backup generator The solar panels are at a high tilt to efficiently capture the winter sun and the skid is designed to accept a deck of cinder block ballast weights The welded steel skid has a powder coated finish and can be rigged into location using a construction forklift or backhoe The control software included added features to perform makeup dosing to accommodate flows below the nominal minimum Additional programming looks ahead to determine the battery state ofcharge SOC and if this becomes too low after several cloudy days the system can proactively indicate the need for a portable generator All site conditions and system activity are logged to the cloud via a secure MQTT connection Figure 2 Top Quantum addressed the off grid power needs with solar panels a charge controller and lithium iron phosphate batteries Figure 3 Bottom All automation and communication components must be rated to withstand the typically harsh outdoor conditions for off grid installations Figure 4 Middle The Quantum Automation QBumpBox solution provides an economical and easily installed way for landfill gas recovery operators to support hundreds of processing well sites