Maximize Production and Revenues of Utility-Scale Solar with DC-Coupled Energy Storage
The addition of energy storage to an existing or new utility-scale PV installation allows system owners and operators the opportunity to capture additional revenues. Traditional storage plus solar applications have involved the coupling of independent storage and PV inverters at an AC bus or the use of multi-input hybrid inverters. An alternative approach – coupling energy storage to PV arrays with a DC-to-DC converter – can help maximize production and profits for existing and new utility-scale installations. DC-Coupled Utility-Scale Solar Plus Storage leads to higher round-trip efficiencies and lower cost of integration with existing PV arrays and at the same time, opens up new revenue streams not possible with traditional AC-coupled storage, including clipping recapture and low voltage harvesting, while being eligible for valuable tax incentives.
BENEFITS OF DC-COUPLED UTILITY-SCALE SOLAR PLUS STORAGE
- Lower Installation and Regulatory Costs than AC-Coupled
- Highest Efficiency
- Increased Project Revenues Through Clipping Recapture
- No Interconnection Study Needed
- Qualifies for Valuable Tax Credits
VALUE STREAMS OF DC-COUPLED UTILITY-SCALE SOLAR PLUS STORAGE
- Clipping Recapture — Maximize Value of PV Generated Energy
- Curtailment & Outage — Continuous Uptime
- Low Voltage Harvesting — Make Money on the Edges
- Capacity Firming — Turn Solar Energy into a Dispatchable Asset
- Energy Time Shifting — Utilize Generated PV Energy When Its Value is Highest
- Ramp Rate Control+ — Modulate Power for Continuous Grid Connection
DC-COUPLED SYSTEM DESIGN
Figure 1 Illustrates the basic design of a DC-coupled system. In this set-up the storage ties into the system behind the existing PV inverter and combines in parallel with existing PV strings at a recombiner. Depending on the size of the inverter and the use cases, designers can install multiple DC-DC converters in parallel on the DC PV bus.
REVERSE DC-COUPLED CONFIGURATION FOR MICROGRID APPLICATIONS
The standard DC-coupled PV+S configuration utilizes a grid-tied PV inverter with energy storage (BESS) coupled to the PV array through a DC/DC converter. This configuration is often the most economically advantageous approach for DC-coupled PV+S exporting power to the grid.
A second configuration— Reverse DC-Coupled PV+S — ties a grid-tied bi-directional energy storage inverter with energy storage directly to the DC bus. PV is coupled to the DC bus through a DC-DC converter. Reverse DC-coupled PV+S is often well suited for microgrid applications because of its inherent ability to efficiently provide safe and reliable power to an islanded microgrid.
PV inverters are typically unidirectional inverters with firmware intended to operate only in grid-tied conditions and as such cannot support a microgrid alone. The Reverse DC-coupled PV+S configuration allows you to operate in off-grid (microgrid) mode by virtue of the AC interface being a microgrid-capable storage inverter. With a Reverse DC-coupled hybrid PV+S system, you can benefit from the CAPEX, efficiency and revenue advantages of DC-coupling, while also enabling a microgrid application with battery backup power traditionally only possible with an AC-coupled configuration.
To learn more about the value of a DC-to-DC Converter for Solar Plus Storage applications, watch our prerecorded webinar or download our whitepaper by clicking the buttons below.
Or read the NREL 2017 report examining the economics of PV installations and energy storage by clicking here.
DYNAPOWER DC-TO-DC CONVERTERS
DC-Coupled Utility-Scale Solar Plus Storage
Dynapower’s DPS family of DC converters, available in 250kW and 500kW building blocks, allows for the coupling of utility-scale solar with energy storage on the DC-side of the bus. DC-Coupled Utility-Scale Solar Plus Storage lowers the cost of installing energy storage alongside utility-scale solar, while also allowing for the greater harvesting of PV energy to boost installation revenues. Designed to be easily scaled, any combination up to 8 units can be joined to create building blocks up to 4MW of DC-Coupled Utility-Scale Solar Plus Storage.