The Role of Net Metering in the Evolving Electricity System (2023) / Chapter Skim
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6 Net Metering and Distributed Energy Technologies
6 Net Metering and Distributed Energy Technologies
Pages 131-148
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From page 131... ...
Briefly, this chapter provides an overview of the effect on the grid of BTM DG and related technologies influenced by net metering and supported by grid technologies to integrate, manage, or control them. It presents a discussion of: • Grid modernization and the integration of renewables • Power-physics-based constraints emerging from integrating BTM DG onto the grid • Emerging advances in power electronics, storage, communications, and control technologies • Cybersecurity and resilience considerations emerging from BTM DG and net metering • Chapter summary and findings GRID MODERNIZATION AND THE INTEGRATION OF RENEWABLES Grid modernization1 is introducing innovative technologies and services to the electricity grid at an unprecedented rate.
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From page 132... ...
The following sections expand on the technology implications of increasing amounts of BTM DG for the larger electricity system, the ongoing technological advances that enable the integration of BTM DG/DER into the electricity grid, and new technologies that are needed to ensure that the integration of BTM DG and DER leads to a reliable and resilient grid. TECHNOLOGY INTERSECTION 1: POWER PHYSICS-BASED CONSTRAINTS BTM DG capacity is expected to increase significantly at the grid edge4 in the coming years, influenced by net metering compensation and other policies.
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From page 133... ...
While customers with BTM DG have the technological capability to provide valuable energy and flexibility services to the distribution grid, this DG needs to be integrated into the grid, not just interconnected to it.6 Successful BTM DG integration at high penetration rates and in ways that enable these resources to provide grid services will depend on addressing the operations challenges of the local distribution grid. In the absence of appropriate communications, control and other technologies, and a regulatory framework that supports investment in them, DG has the potential to disrupt distribution grid operation through reverse power flows, voltage violations, harmonics, phase unbalance power quality concerns, the mal/mis-operation of protection devices, as well as presenting grid bottlenecks and congestion.7 Avoiding these problematic outcomes is essential (see Box 6-1 for one example of how DG systems may support system security)
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From page 134... ...
If sufficient storage capacity is not available to address any imbalance, the challenge will be to develop and adopt alternative technologies that address these imbalances and/or pursue program and rate designs that can do so. For example, Hawaiian Electric's Smart Export Program requires distributed solar systems to be paired with battery storage and only provides compensation for electricity exported during the hours of 4:00 pm to 9:00 am.8 8 For more information see https://www.hawaiianelectric.com/products-and-services/ customer-renewable-programs/rooftop-solar/smart-export.
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From page 135... ...
In addition, advances are being reported in multiple kinds of storage capability, including thermal, chemical, and mechanical energy.11 Encouraged by these technological advances, the improving economics of storage, and flexible loads that can provide grid support at an equal or lower cost than peaking power plants, utilities in many states are already starting to procure significant amounts of storage to address variability and balance real-time supply and demand.12 The second technological challenge is managing imbalances across the three phases (or wires) 13 of alternating current used to deliver power to customer locations.
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From page 136... ...
Often there can be a large variation and therefore grid operators have to exercise control through these devices to ensure a reliable grid operation. See Horowitz, S.H., A.G.
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From page 137... ...
variable generation and load patterns on both sides of the meter; (2) unpredictable customer behavior related to individuals' habits and personal satisfaction affecting consumption and net BTM DG production (e.g., when these customers run water-heater and air conditioning devices, and operate kitchen appliances, and charge their electric vehicles [see Box 6-3 for a further discussion of these uncertainties]
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From page 138... ...
Over the past several decades, the design of the distribution grid has been dominated by a top-down approach -- one in which the utility plans to respond to whatever happens due to customers' withdrawals of electricity from the grid -- in terms of the primary and secondary feeders and their interconnections, and the location and type of voltage control devices including transformers, load-tap changers, and capacitor-banks. Through appropriate design and management of these voltage control devices, utilities have operated the power grid and ensured its reliability and power quality.
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From page 139... ...
To this end, time series forecasting models have gained prominence.19 Grid operators have leveraged forecasting models for estimating BTM load, generation, and market prices, and for estimating time-horizons for predicting BTM load and generation for quantifying risks and reducing uncertainties to lead to better planning operational strategies. TECHNOLOGY INTERSECTION 2: EMERGING ADVANCES IN POWER ELECTRONICS, STORAGE, COMMUNICATIONS, AND CONTROLS The seamless integration of significant amounts of DG and flexible loads and exports necessitates advances in technologies at multiple levels to ensure reliable grid operation.
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From page 140... ...
Increased usage during the night due to increased EV charging can place additional load on transformers by not permitting the transformer oils to cool, thereby directly affecting grid reliability. Excess availability of solar PV generation in midday could negatively affect grid operations, as net load (i.e., total load minus solar PV generation)
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From page 141... ...
While such technological advances support the availability of resources for ensuring power balance, and therefore grid reliability, utilities and grid operators may only be able to leverage them if there exists a strong communications backbone and a SCADA system24 to enable the coordination needed between these critical assets and control rooms located at appropriate locations in the distribution grid. The increasing growth of DER, accompanied by growth in advanced metering infrastructure (AMI)
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From page 142... ...
Internet of Things (IoT) -enabled devices have provided a new platform for grid operators to facilitate flexible consumption.
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From page 143... ...
Significantly more studies need to be carried out to understand issues related to tariff, interconnection, and ownership considerations related to who manages or who has technical control over 28 Demand response programs offer models that may be applied to BTM distributed generation through NEM compensation design. A typical illustration of this project demonstrated peak load reduction and energy cost saving through the coordination of multiple water pumps, diesel generators, and heating loads of several residential houses.
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From page 144... ...
While cyber-secure BTM DG systems could offer a significant potential to sustain power grid services under extreme operating conditions, particularly those with highly reliable and resilient power supplies, they too are also subject to cyber incidents. Moreover, cyber vulnerabilities in 32 In its September 2020 "Order 2222," The Federal Energy Regulatory Commission (FERC)
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From page 145... ...
As more and more devices are connected to the grid, they pose correspondingly increasing cyber risks that need to be addressed by local grid operators. Failure to address such considerations will weaken the reliability of the grid, potentially offsetting to some degree the other grid and customer-specific resilience benefits of deployment of DG.
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From page 146... ...
If DG is configured so that it can provide resilience, not only to the consumer but also to the distribution grid, the corresponding net metering compensation should reflect this value. Various DG technologies can be utilized to provide resilience, the most common of which is backup generation.
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From page 147... ...
To simultaneously address the accompanying challenges of variable demand, grid reliability, and cyber-physical security, investment in technology on the distribution system is essential to, among other things, provide visibility to grid operators so that they can assure the stable operation of the system while also unlocking the potential of DG and DER to provide grid services and value to the system.40 Without investment in such grid technologies, not only might the potential for BTM DG to provide grid services be stymied, but also deeper deployment might have negative consequences on grid reliability. Policymakers and regulators need to understand the importance of such grid investments in conjunction with increasing deployment of DG as they consider the framework for allowing utilities to recover these costs.
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From page 148... ...
RECOMMENDATIONS Recommendation 6-1: There need to be direct investments in the distribution system to integrate increasing amounts of BTM DG such as rooftop solar, as well as other DER, including smart buildings management systems, electric vehicles, and charging infrastructure, to ensure the continued safe and reliable operation of the grid and provision of grid services. Investments will also be required to improve grid visibility to suitably site and operate BTM DG, as well as provide efficient price signals, such that the DG can provide system benefits, particularly local and grid resilience when normal service is disrupted.
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