Using control systems to optimize microgrids with CHP - Thermo Systems
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Using control systems to optimize microgrids with CHP Proper system integration is key in today’s increasingly complex projects. Serge Zinger, Account Executive, Thermo Systems LLC; and Jason Wittkamp, PE, Director, Thermo Systems LLC Photo Serge Zinger. The microgrid/CHP system at the TWA Hotel. icrogrids are a focal point of dis- Whether a district energy system is tem (PMS). All of these will be used to M cussion in the district energy industry, and this trend does not appear to be going in any other direction but up. As the demand for microgrids has increased, so has their considering a traditional microgrid, one coupled with CHP, or a hybrid microgrid, a major area of focus should be the supervi- sory control and data acquisition (SCADA) automation, balance-of-plant (BOP) con- integrate the OEM equipment and enable the microgrid to function as one coordi- nated system. This SCADA plant control system should be robust, reliable and responsive to make sure the entire complexity. End users want to gain effi- trol system and power management sys- microgrid system works as designed. ciencies from new technologies and hybrid systems to optimize their micro- grids. With the increasing complexity, it is critical to incorporate robust, adapt- able controls to ensure the successful commissioning, operation and mainte- nance of these systems. Whether the project driver is a post-natural-disaster recovery, the aftermath of wildfires or an energy reliability/resiliency goal, microgrid solutions are being discussed and deployed. Microgrids are sophisticated systems that can generate electrical energy in parallel with or independent of the local electrical utility (main grid). Microgrids typically consist of a prime mover (com- bustion turbine or reciprocating engine) that can produce power/electrical energy, and they are often utilized with combined heat and power technology to produce steam or hot water. There are also hybrid microgrid systems – consisting of addi- tional original equipment manufacturer Photo Serge Zinger. (OEM) components – which are gaining popularity. A microgrid/CHP system operator monitors hot water production at a SCADA workstation. © 2020 International District Energy Association. ALL RIGHTS RESERVED. District Energy | Spring/Summer 2020 9
To illustrate the successful deploy- The PMS is typically responsible for mize the system’s efficiency and return ment of microgrid systems, it is useful to breaker control/interlocks, load man- on investment. A BOP control system explore three different customer types in agement (automatic load shed and/or can be installed within these facilities to the New York, N.Y., metro area: Hudson restore) and coordination of generating coordinate and control the plant’s OEM/ Yards, a real estate megaproject; the TWA resources. The PMS controllers require BOP equipment and ensure the waste Hotel at John F. Kennedy International fast response times to handle unex- heat is utilized effectively. The BOP will Airport; and New York University. While pected events and to ensure the cogen- also provide control of all the miscella- the considerations and needs driving each eration facility is kept on line through neous systems within the plant, which of their decisions to implement a micro- upsets. In addition, the PMS provides is required to keep the electrical gen- grid may have varied, one critical com- remote monitoring/control and long-term eration equipment operational. These mon factor for all was the selection of historical trending using an overlaying systems typically include natural gas, an industrial-grade SCADA solution with SCADA system. The sequence-of-events lube oil, gas detection, feedwater, cool- a programmable automation controller- reporting for analyzing alarms and deter- ing water, plant HVAC, etc. Similar to the based plant control system. mining trip root cause is also commonly PMS, a SCADA is overlaid on top of the included. Utility companies require BOP to provide remote control/monitor- MAXIMIZING POTENTIAL access into the PMS to monitor critical ing, long-term historical trending, and Regardless of who the microgrid user microgrid information and to be able to alarm management. is, or what the drivers are, the key to a trip generating resources offline should See figures 1 and 2 for examples successful project is the proper integra- the need arise. of SCADA human-machine interface tion of OEM components and the intelli- Many microgrids include cogenera- screens depicting, respectively, the CHP gent dispatch of energy, both electric and tion or CHP equipment as the source of system process equipment and the PMS thermal. on-site power generation. These cogen- used for management and/or coordina- Microgrids with multiple generating eration units typically utilize natural gas- tion of electrical systems. resources, energy storage, varying loads burning engines or combustion turbines. Effective coordination between the and a connection to the utility company Cogeneration facilities require use of the PMS and BOP systems is essential for require a power management system. engine’s or turbine’s waste heat to maxi- fully maximizing the cogeneration and FIGURE 1. Screenshot of combined heat and power system overview. Source: Thermo Systems LLC. 10 District Energy | Spring/Summer 2020 © 2020 International District Energy Association. ALL RIGHTS RESERVED.
microgrid potential. Every site will have a unique solution based on utility agree- ments, electrical generating resources, equipment capabilities and thermal load profiles. THREE SYSTEMS, UNIQUE SOLUTIONS The microgrid systems with cogen- eration operating at the three sites in New York – Hudson Yards, the TWA Hotel and New York University – were each established with different goals and driv- ers. These included having the ability to reliably keep the lights on and provide heating and cooling to campus buildings, use the microgrid as an infrastructure enhancement to attract tenants, reduce the site’s carbon footprint and be the property’s sole source of power. These customers are all achieving their goals with microgrids that exemplify the effec- tive use of control systems. Hudson Yards Courtesy Related Oxford. On Manhattan’s West Side, Hudson Yards is New York’s newest neighborhood, Restaurant view, the shops at Hudson Yards. FIGURE 2. Screenshot of power management system overview. Source: Thermo Systems LLC. © 2020 International District Energy Association. ALL RIGHTS RESERVED. District Energy | Spring/Summer 2020 11
considered the largest private real estate controller, the BOP collects information son Yards CHP plant. The thermal and development in the city since Rockefeller from the chilled- and hot water-consum- electric loads will likely never be equal. Center. Comprising 28 acres, it will ulti- ing residents and tenants on the prop- As a result, an advanced control scheme mately include more than 18 million sq ft erty. The BOP utilizes this information had to be developed to determine where of commercial and residential space, along to determine where to invest the waste the output of the engines will be set. with more than 100 shops, a collection of heat energy from the engine generator. This control scheme takes into account restaurants, a public school, 14 acres of The waste heat can be used to generate the electric rate structure with the util- public plazas and gardens, and more. The hot water, chilled water or both via the ity company, availability of other plant microgrid/CHP system serving Hudson use of an absorption-type chiller. assets and criticality of the load consum- Yards comprises four reciprocating Once the waste heat energy is prop- ers. Additionally, the control scheme pro- engines, four directly coupled absorption erly allocated, the BOP can determine vides the ability to limit some customers’ chillers and a free-cooling system. whether it has too much or too little consumption in extreme cases. Without Operation of the Hudson Yards micro- waste heat available. If there is excessive this control scheme and coordination, grid system is financially driven. Depend- waste heat, the plant will be required the engines cannot run at an optimal ing on conditions at the site, the system to reject the heat using cooling towers, output, and the Hudson Yards plant may be either thermally or electrically which is a waste of the electrical energy would not meet the needs of its cus- led. Regardless of which approach is created from the generators. On the tomers or could overproduce and nega- selected, the objective is to ensure that other hand, if there is insufficient waste tively affect their efficiency and payback the tenant/retail spaces receive the best heat, then other boiler and chiller assets period. payback. from the facility will need to be utilized. Once electrical demands are satis- Based on the current state, the BOP will TWA Hotel fied, the electrical output of the engines request that the generators increase or In another case, the TWA Hotel – may need to be increased in order to decrease output in an attempt to balance formerly the iconic Eero Saarinen-designed produce more waste energy to satisfy the waste heat with the thermal demand. TWA Flight Center – at Kennedy Airport the thermal demand (chilled or hot water) In a similar fashion, the PMS pro- in Queens was constructed without con- of the site. The decision of where to set grammable automation controller is nection to the electrical grid. This was the engine’s output is determined with monitoring the demand of the electric done to avoid the high utility prices and input from both the BOP and PMS sys- energy customers to determine the costs for upgrading the old interconnec- tems. Using a programmable automation appropriate electric output of the Hud- tion infrastructure that once provided Photo Shutterstock. The new TWA Hotel opened to guests in May 2019. 12 District Energy | Spring/Summer 2020 © 2020 International District Energy Association. ALL RIGHTS RESERVED.
power to this 1960s-era TWA terminal building. With the aid of the microgrid, all the electrical and thermal energy at the TWA Hotel is generated on-site. The property’s microgrid includes three reciprocating engines and an elec- tric storage system consisting of two batteries. The electricity and waste heat generated by the engines is utilized to produce the hot and chilled water for the hotel and convention center. The electric storage system provides the means to allow the engines to baseload while the battery maintains frequency and voltage. The electric storage system also provides a safety net to keep the lights on through any unexpected interruptions of power to the plant. The coordination between this sys- tem’s BOP and PMS is intertwined on many levels. In this case, both systems were combined into a single program- mable automation controller, allowing for one central processor to monitor conditions and instantaneously make operating decisions. Without the grid for reliability and inertia, the plant’s control system must make decisions regarding turning on and off engines, charging or discharging the battery, and using either Photo littleny, iStock. gas-fired or electric chillers. Load shed- New York University in Manhattan’s Greenwich Village. ding of noncritical loads in the case of an emergency is also utilized to main- tain plant operations. Tight coordination operate at maximum capacity, and the COMBINING BOP, PMS between the PMS and BOP enables reli- duct burners of the heat recovery steam Effectively integrating the BOP and able, effective and efficient operation of generators modulate to match the steam PMS systems requires planning and con- this plant. demand of the steam turbine generators, sideration upfront. The most streamlined chiller and heat exchangers as needed. and cost-effective means is to combine New York University NYU utilizes energy from the utility com- these systems into a single program- In Manhattan’s Greenwich Village pany to make up the excess demands of mable automation controller, as seen in neighborhood, New York University (NYU) the campus buildings. The plant operates the TWA Hotel example. This is an indus- operates a microgrid with CHP equip- in this fashion 99 percent of the time. trially hardened solution with varying ment to provide heating, cooling and However, in 2012 when Superstorm levels of redundancy applied to ensure electricity to its classroom, office and Sandy hit, and the electrical grid of lower minimal disruptions to operations. This dorm buildings. The CHP system includes Manhattan went dark, the plant had to approach of a single programmable auto- two gas turbines coupled with heat change operations to an electrical island mation controller is not always practical, recovery steam generators. The gas tur- mode. With the safety net of the grid especially for larger, more distributed bines create electricity, and the heat gone, the control systems of the plant systems. In that case, ensuring that the recovery steam generators produce were relied on to manage campus elec- controllers of the BOP and PMS systems steam that feeds a steam turbine gen- trical demand, ensuring it did not exceed natively communicate with each other at erator, a steam-driven chiller and steam- the CHP system’s capacity and endanger high speeds is imperative. to-high-temperature-hot-water heat its operations. In the end, the plant was To ensure smooth integration, it is exchangers. able to remain on line during the extended advisable to have a single provider of Under normal circumstances, the grid outage, and NYU received praise for the two systems with expertise in both plant runs per design in a relatively its vision and planning for an event such microgrid and CHP applications. Devel- simple control scheme; the gas turbines as this. oping an upfront design specification © 2020 International District Energy Association. ALL RIGHTS RESERVED. District Energy | Spring/Summer 2020 13
for the control scheme makes sure that and BOP plant control system. Early in electrical engineering from Rensselaer the systems can be put through exten- engagement with an experienced con- Polytechnic Institute. He can be reached sive factory testing before they are trols integration provider – one that can at firstname.lastname@example.org. deployed on-site. Due to the critical recommend the proper technology to nature of the loads that microgrids and apply and has the expertise to deploy it CHP systems support, on-site testing – can aid in achieving a successful out- Jason Wittkamp, PE, is a would be disruptive or impossible. come for the project. director at Thermo Sys- Today’s microgrid/cogeneration sys- tems LLC, where he has tems are evolving into complex hybrid worked for over 13 years. systems. In addition to combustion tur- Serge Zinger currently He is an expert in the in- bines, reciprocating engines and battery holds the position of ac- strumentation and con- storage, these hybrid systems now count executive at Thermo trols industry; his efforts have concen- include photovoltaic arrays, fuel cells, Systems LLC, where he has trated on utility systems and the efficient flywheels, etc. – increasingly driven by worked for over 11 years. operation thereof. Wittkamp has exper- the desire for more sustainable systems. He has provided high-level tise on a multitude of large projects, in- These control systems, which make expertise on projects in the district energy cluding the New York University com- complex electric and thermal microgrids marketplace, including microgrids, com- bined heat and power plant, Hudson possible, also make it possible to inte- bined heat and power, landfill gas-to- Yards cogeneration plant and the TWA grate renewables and waste heat, thus energy, and chilled- and hot water distri- Hotel microgrid, to name a few. A licensed lowering carbon emissions. bution. His past work experience includes professional engineer, Wittkamp has a As these systems grow in size and the positions of general manager of engi- Bachelor of Science degree in mechanical complexity, so does their dependency neering at Panasonic Electric Works and engineering from Rutgers University. He on being integrated into a robust, reli- applications engineer at Deutsch Relays. can be contacted at jason.wittkamp@ able and appropriately matched SCADA Zinger has a Bachelor of Science degree thermosystems.com. 14 District Energy | Spring/Summer 2020 © 2020 International District Energy Association. ALL RIGHTS RESERVED.
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