5/21/2023 0 Comments Battery plus![]() The design of DC-coupled systems is complex and integrated, largely because the battery racks are distributed throughout the PV field, leading to a greater number of smaller battery racks and, therefore, higher structural balance of system (BOS), electrical BOS, labor, and O&M costs than colocated systems.Cost implications for DC-coupled systems are complex: such systems require only one shared inverter (which presents a cost savings), but they require additional DC-to-DC converters and could require more sophisticated control systems to co-optimize the utilization of both the PV and battery components (which presents a cost increase).DC coupling enables operational synergies such as (1) increased round-trip efficiency when the battery charges from the coupled PV and (2) the ability to capture energy that would otherwise be clipped by the inverter or lost due to low-voltage conditions (e.g., during sunrise/sunset and hours with significant cloud cover).Within the context of this uncertainty, we choose a DC-coupled configuration for the default utility-scale PV-plus-battery technology because of characteristics that make the coupled system distinct from multiple separate systems, including that: Moreover, the highest-value architecture will likely evolve over time based on future changes in the grid mix, the performance characteristics of key hybrid components (e.g., bidirectional inverters and DC-to-DC converters), and federal incentives (Schleifer et al., 2022). Interconnection queue data for most market regions do not include detailed information about inverter characteristics for proposed projects (Bolinger et al., 2021). The dominant architecture for proposed and future utility-scale PV-plus-battery systems is highly uncertain (Ramasamy et al., 2021) (Schleifer et al., 2022). After accounting for state-of-charge and roundtrip efficiency constraints, the oversized battery component allows for 55-MW DC of usable stored power (or 220 MWh of usable stored energy). The assumed relative sizing of the PV, battery, and inverter components is consistent with existing (but limited) data for online and proposed utility-scale PV-plus-battery systems-whose inverter characteristics (shared versus separate) are not well known.Ĭomponents of a DC-coupled PV-plus-battery system Therefore, the PV component has a DC-to-AC ratio (or inverter loading ratio ) of 1.3, which is slightly larger than that assumed for utility-scale PV (1.28) in the 2022 ATB. The PV-plus-battery technology is represented as having a 130-MW DC PV array, a 71.5-MW DC battery (with 4-hour duration), and a shared 100-MW AC inverter. The utility-scale PV-plus-battery technology represents a DC-coupled system (defined in the figure below), in which one-axis tracking PV and 4-hour lithium-ion battery (LIB) storage share a single bidirectional inverter. For details, see the scenario descriptions for utility-scale PV and the scenario descriptions for utility-scale battery storage. Technology innovation scenarios for PV-plus-battery are a combination of utility-scale PV and utility-scale battery technology innovation scenarios (e.g., the Conservative Scenario for PV-plus-battery technology uses the Conservative Scenarios of both utility-scale PV and utility-scale battery technologies). See the Resource Categorization section of the utility-scale PV page for a description of these 10 resource categories. The PV-plus-battery technology uses the same 10 resource categories as the utility-scale PV technology. Future year cost projections are derived from bottom-up benchmarking of utility-scale PV-plus-battery CAPEX and bottom-up engineering analysis of O&M costs, and future capacity factor estimates encompass a range of technology innovation scenarios for utility-scale PV and utility-scale battery storage. Capacity factor is estimated for 10 resource classes for the United States-which are binned by mean global horizontal irradiance (GHI)-and it is based on assumptions regarding battery operation. Base Year cost estimates rely on modeled capital expenditures (CAPEX) and on operation and maintenance (O&M) costs benchmarked with industry and historical data. Details are provided for a single configuration, and supplemental information is provided for a range of related configurations in order to reflect the uncertainty about the dominant architecture for coupled PV and battery systems (now and in the future). 2022 ATB data for utility-scale PV-plus-battery are shown above.
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