Nick Marcheschi describes the design and development of a microgrid to support the Net Zero and renewable goals at a US zoo and botanical garden.
A zoo and botanical garden in the US is designing a master plan for infrastructure investment focused on the electrical utility system throughout the campus for future investments and developments.
Recently, ENTRUST Solutions Group supported the zoo in its goal to attain a Net Zero initiative by 2025 by initiating a microgrid to maximize the benefits of renewable investments such as new medium voltage (MV) switchgear, extra solar capacity, and battery energy storage system (BESS) integration.
ENTRUST provides comprehensive and dependable inspection, engineering, environmental services, consulting, codes compliance, integrity and process safety management services to utilities, pipeline companies, and industrial customers.
ENTRUST’s project management philosophy for the type of master plan designed for the zoo is to thoroughly determine the technical approach and how it flows into the schedule upfront. It is critical to understand the client, their historical data and what they want to achieve.
In ENTRUST’s experience, allowing its master plan team lead to gather this data first before beginning to model creation/updates and economic analysis is key. Once the data is collected, it is summarized by ENTRUST’s field engineers and recommendations are provided to the distribution planner.
These recommendations of action on existing infrastructure along with the other details outlined in the technical approach are then integrated into the power system study model.
MV switchgear replacement and/or modernization allows the zoo to monitor and control each utility feeder and generation asset. Cost savings will be realized through reduced electrical outages and electrical equipment failure. Less reliance on the electrical utility system will provide the zoo with increased flexibility in sourcing power supply.
Parking lot solar canopy expansion allows for the zoo to experience 100% renewable generation for a large majority of each day. This will enable the zoo to overproduce during peak loading periods and in time sell back to a utility provider. Overproduction will also serve as a source to charge the battery energy storage system.
A BESS/microgrid controller integration will provide black start capability for solar generation assets, emergency power in the event of a utility outage at night and future regional transmission organization (RTO) frequency response market opportunity.
The installation of new switchgear will allow grid isolation in the event of an outage, black start associated with the battery energy storage system in order to protect critical loads within the zoo and/or allow the zoo to generate power directly from the solar arrays onsite if they are available, and the grid is not.
Currently, when facing a utility outage, the zoo does not have the ability to isolate and generate power from its onsite solar array. While rare, this emergent issue may cause disruption to the safety of the animals, employees, and customers on site at the zoo.
Certain items will allow for better control, protection and monitoring of all feeders and generation sources at the zoo including the existing solar array, proposed solar array, proposed BESS and electric power feed. These include:
This will be used to provide instantaneous and timed overcurrent protection for each feeder. Protection schemes such as this may reduce failures of electrical components throughout the zoo and allow for more insights on where and how to address issues that are identified.
The relaying will also allow for performance metrics for each feeder to be measured, such as amperage loading and power quality performance issues.
This can be used to retrieve any data collected from each of the SEL 751 relays and combine it into one source of information to establish the data collection for all seven feeders. It can track metering, voltage-current and power factor. This will then provide real-time data for each feeder and provide insight into plans for capacitor bank installations to rectify any underperforming feeders and their transformers. This designates all combined data into a singular control platform and will provide easy access of data for the SCADA once implemented.
The expansion of solar onsite will allow the zoo to be independent of the utility during most daytime operations. This will provide significant cost savings on utility bills. ENTRUST performed load analysis studies to determine which of the zoo’s seven 12.47kV feeder lines could take on this new solar capacity.
With the existing 1.5 MW solar array above one of the zoo’s parking lots, 235 A of power tracing back to the new switchgear was deemed to be available. With the implementation of the new switchgear and SCADA systems, the photovoltaics (PV) generated at the switchgear itself will be isolated and re-distributed on a per-feeder basis. Information will be generated at the solar panel and will be sent back via a fiber network and collected at the RTAC for all usage and PV generation. Once all the solar PV is distributed, BESS supply, diesel generators, etc. will recommence operations.
During peak hours, the solar arrays will overproduce compared to the load demand at the zoo. The benefit of that overproduction means future utility agreements will allow the zoo to sell excess power generation back to the grid for a credit as the industry moves towards cost savings and Net Zero goals.
Furthermore, excess production will allow the battery energy storage system onsite to be charged and available for black start during off-peak hours and utility interconnection requirement curtailment at the beginning of each day as the solar array starts to come online.
ENTRUST is responsible for the localized engineering support and management, and interconnection design for a new BESS at the zoo, based on ENTRUST’s power system model. The battery energy storage system provided is being designed as a ‘distributed’ system so future expansion of the BESS can be implemented at other locations within the zoo as costs of these systems continue to reduce and the value of additional kW/kWh increases.
Future consideration could be given to entering the zoo into the RTO’s frequency response market, although this option is not currently being actively evaluated. The market is, however, evolving for this to be a potentially large benefit for the zoo in the future, such as the peak load shedding program already being participated in through the RTO.
The zoo had one operational goal in mind for the BESS, and that was resiliency. Resiliency is a growing need in the microgrid system because it ensures that companies and businesses will not be without power in times of critical need. This need is applicable to any organizations including not limited to schools, hospitals, municipalities, and private companies.
In this case, the zoo wanted the BESS to be designed to allocate a minimum of eight hours of reserve battery capacity to power critical loads during periods of solar non-generation. This scenario includes an operational procedure to be followed that prolongs the battery life as long as possible. This would ensure that there are no blackout windows during critical operations that could potentially adversely impact resources and animal health.
This procedure includes de-energizing non-critical feeders via the switchgear RTAC and operating the BESS as the primary back-up source and its on-campus combustion generators as a secondary source. By focusing only on the critical loads, and the zoo’s interval data and history, ENTRUST was able to determine the most cost-efficient and effective size/discharge rate for the BESS.
The overall proposed BESS was to include the following components:
The microgrid controller will allow an automated energy management system to be implemented at the zoo to maximize the use of the existing solar array, the proposed solar array and the proposed battery energy storage system. Once the BESS is online, the microgrid controller will then communicate with the SEL 751 relays seen on each feeder at the switchgear. Via a 12-strand fiber connection, it will directly communicate the emergency operation scenario described above and only energize the critical loads to best utilize the existing charge observed on the systems.
ENTRUST is demonstrating many special qualities in creating an electrical master plan as requested by the zoo. These include distribution system planning and modeling for utility, protection and control systems evaluations and co-ordination studies, voltage stability studies including modeling of motors and HVAC loads, active power (MW) loss optimization and reactive power (MVAr) compensation studies and event analysis of system disturbances and outages to support root cause analysis. Electrical distribution inspection and design includes inspection and designing master plans based on cable and equipment inspection and condition assessments, engineering plans for previous upgrades recently completed, review of existing fiber optic systems, and review of existing duct bank systems and ability to be utilized for future modernization and reliability opportunities.
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