Surging demand for solar photovoltaic (PV) systems is being met with innovative initiatives to harness the trend.
Austin Energy is in the final proving stages of a project supported by the U.S. Department of Energy (DOE) to improve the generation, delivery, and consumption of energy through scalable, cost-effective solar technology integration and storage. Its success may establish a path to accelerate grid modernization nationwide.
The rapid influx of residential, commercial, and industrial PV is forcing the industry to confront the complexities of integrating rooftop solar systems and other distributed energy resources (DERs) to the electric grid.
PV penetration on Austin Energy’s distribution network was increasing and the utility wanted to get ahead of it before grid problems arose. The DOE’s Sustainable and Holistic Integration of Energy Storage and Solar PV (SHINES) program presented a timely solution funding opportunity.
Based on earlier work together, Austin Energy chose Doosan GridTech to help conceptualize the Austin SHINES DER integration and energy storage strategy and present it to the DOE. The proposal was a success. Austin SHINES was one of six SHINES projects awarded a grant as part of the DOE’s Grid Modernization Initiative.
In addition to the $4.3 million from the DOE, the project received $1 million from the Texas Commission on Environmental Quality (TCEQ) and more than $5 million in matching funds from Austin Energy.
With funding secured, additional partners were brought onboard. Austin Energy, Doosan GridTech, Pecan Street, Stem, ConnectDER, and others helped to assemble the Austin SHINES solution and are currently demonstrating it in a field study. While the preliminary findings are promising, the industry as a whole has hurdles to overcome.
The Austin SHINES project aims to demonstrate the technical feasibility and economic value of DER asset integration and control to deliver a clean, affordable, safe, and reliable supply of energy to its customers. Overcoming solar power’s most enduring challenge – the intermittent, variable nature of sunlight – meant incorporating energy storage and intelligent controls to maximize the penetration and reliability of distributed PV.
The Austin SHINES resources collectively include:
- Two utility-scale energy storage systems (ESS)
- Multiple customer-sited ESSs at residential and commercial properties
- Smart inverters
- Real-time data feeds
- A distributed energy resource management system (DERMS)
- A vehicle-to-grid component
Through integration, optimization, and modeling, the project team has come to understand the steps required to prepare a grid for surging solar generation as well as the economics of relentless grid reconfiguration.
They are also learning how changes to the way Austin Energy’s systems operate can increase reliability while reducing energy costs. Strategies being explored include demand charge reduction, congestion management, voltage support, real-time price dispatch, day-ahead energy arbitrage, utility peak load reduction, and value stacking of the various strategies.
Furthermore, because Austin SHINES is designed for adaptability to any region and market structure, it supports the broader SHINES goal of strengthening the resiliency, reliability, safety, and security of the nation’s electric grid.
Austin Energy, the third largest municipal energy utility in the U.S., is already meeting about 40 percent of its customer energy needs with renewable resources. It actively experiments with and explores new ways to maximize the use of renewables and meet its ambitious goals:
- Offset at least 55 percent of customer load with renewable resources.
- Integrate 10 MW battery storage and 20 MW thermal energy storage.
- Deploy 750 MW utility-scale solar and 200 MW local solar, including 100 MW customer-sited PV.
- Offset 65 percent of customer load with renewable resources.
- Integrate 30 MW thermal energy storage.
- Record 1000 MW of savings from energy efficiency and demand response.
- Achieve net-zero community-wide greenhouse gases.
The above goals are also subject to meeting Austin Energy’s affordability goals: keeping rate increases to less than 2 percent a year and utility rates in the lower 50th percentile in the state.
The Austin SHINES program comprises more than 5 MW of utility-owned ESS, solar PV, and distributed residential and commercial storage, configured as follows:
energy storage plus PV:
- 2.6-MW community solar farm
- Two ESSs, one each at the Kingsbery and Mueller locations, each approximately 1.5-MW/3-MWh Li-ion
energy storage plus PV:
- Aggregated storage installations at three sites; one with 18-kW/36-kWh Li-ion battery storage and two with 72-kW/144-kWh Li-ion battery storage
- Each commercial participant has rooftop solar
energy storage plus PV:
- Aggregated storage installations at six homes (10 kWh each)
- One electric vehicle connected in vehicle-to-grid fashion (28 kWh available for grid dispatch)
- An additional 12 homes with utility-controlled solar PV (through smart inverters)
- Six homes with autonomous settings on their solar PV smart inverters.
Seeking to optimize the value of DERs holistically, Austin Energy chose Doosan GridTech’s Distributed Energy Resource Optimizer (DG-DERO) and the Doosan GridTech Intelligent Controller (DG-IC) as the project’s primary software control platform.
DG-DERO is a DERMS platform that enables automatic dispatch and scheduling of the DER fleet from a central interface. It allows for economic value optimization of the fleet based on inputs such as grid data, market data, and forecasts. It also interfaces with the site-level controller or aggregator for each installation.
DG-IC units intelligently manage the distributed resources and provide data back to facilitate decisions in central operations. They support real-time monitoring and control for utilities to maintain cost-effective power quality and safe, reliable operations.
Austin Energy also selected Smart ConnectDER interconnection technology for the residential solar installations. The 18 residential PVs are either autonomous (fixed power factor settings) or under direct utility control. For residential and commercial storage, aggregator platforms are being used. All local control systems used at the grid edge communicate using open standards and are capable of managing DER assets in real time.
A key differentiator of the Austin SHINES project is how it measures the cost of energy. Rather than the customary levelized cost of electricity (LCOE), the Austin SHINES proposal suggests a system-wide LCOE (or SLCOE) metric to better evaluate and optimize the grid’s mix of resources.
LCOE represents the cost of individual asset’s energy generation over its lifetime, including the initial investment, operations, maintenance, cost of fuel, and cost of capital, divided by the amount of energy produced by the asset. It is expressed in $/MWh or cents/kWh and can be compared across assets.
SLCOE, on the other hand, recognizes that DER assets are paired or grouped to serve the load, and therefore deliver synergistic value. Use of SLCOE was approved by the DOE to assess Austin SHINES DER costs and performance holistically, including all assets working together within a defined distribution circuit or “boundary.”
Translating Learnings into Practice
Preliminary lessons from Austin SHINES demonstrate the potential, challenges, and realities of implementing holistic DER integration and storage. What follows is a sample of the lessons learned so far.
Ensure DERs provide value to the broader utility system, from the grid to the customer. A utility, customer, aggregator, or transmission system operator might try to get value out of the same DER asset differently. For example, the customer peak and Electric Reliability Council of Texas (ERCOT) peak may or may not happen at the same time, so tight coordination is required to manage the complexity and provide value where it is due.
The commercial aggregator uses algorithms to monitor load, forecast peaks, and discharge the battery to offset customer demand and reduce customer bills. It was discovered through testing that exchanging availability information between the aggregator and DERO was critical to stacking value for the customer and utility.
Configure utility-integrated ESSs with open standards, distributed controls, and coordinated applications. Interoperability improves communication, knowledge sharing, and productivity while reducing costs and avoiding vendor lock-in. For Austin SHINES, Austin Energy required open-standard communication to promote interoperability. Although DER communication and integration standards are considered open, the project revealed that some required some degree of customization to accommodate the needs at both end points.
The utility also recommends intelligent, distributed controls along with a holistic DERMS coordinating platform to balance DER dispatch and grid support and drive economic optimization.
Use SLCOE metrics to ensure DERs contribute to grid reliability and economics.
SLCOE supports DER asset optimization through modeling, simulations, and the current realities of field demonstration data. For instance, multiple DER assets can be measured and optimized at the circuit or system level, making it easier to understand how DERMS controls benefit the distribution utility. SLCOE also enables comparison of a current DER state to alternative future scenarios to understand the effects of increasing solar penetration and adding additional storage assets to the circuit.
Economic modeling helps utilities understand financial tipping points whereas reliability modeling helps utilities to determine at what point solar penetration will create operational problems. Austin Energy determined that the current penetration of renewable energy resources on Austin Energy’s distribution grid is 6%, and the tipping point for voltage issues will occur when penetration approaches 40%.
Don’t overlook communication. How the system communicates with residential PV assets may be expensive but beware of sacrificing reliability for lower costs. Also, determine whether the extra complexity of adding a communication signal to an asset is worthwhile, or if the asset can be controlled autonomously for similar value.
The choice of cellular communication for Austin SHINES residential PV assets was intentional, despite the team knowing it was not scalable. The project team explored a more scalable alternative, radio mesh, but did not get results early enough to implement it in the field.
Minimize DER downtime. Whenever storage assets go offline and out of DG-DERO’s control, Austin Energy risks losing project value. Outages due to software fine-tuning, a warranty claim, a heat wave, and a precautionary measure occurred during the Austin SHINES 2019 project demonstration period.
The precautionary incident followed a 2019 fire at another U.S. utility’s energy storage installation, which prompted a closer look at some fires abroad. Out of an abundance of caution, Kingsbery ESS operations were suspended and Mueller ESS development was delayed while waiting for the final incident reports. Austin Energy used that time to review its safety protocols and storage safety systems.
Regulators and policymakers have work to do. DER technology advancements are outpacing building codes, permitting process, rules, and regulations. For instance, it can take time for a fire department to decide how to permit new technologies being installed inside a building.
Another example is ERCOT’s utility peak load reduction rules. No asset over 1 MW is currently allowed to participate in its Four Coincident Peak (4CP) program and get credit for it, which rules out the project’s largest assets–Kingsbery and Mueller. Without a rule change, only the smaller Austin SHINES assets will be eligible for the savings.
More to Come
Though still in the demonstration phase, the initial Austin SHINES results indicate that DER integration should remain a critical strategic initiative for Austin Energy. Findings from this groundbreaking, industry-leading field study will help to mold the future of distributed energy and customer engagement at the grid edge. Upon the project’s completion in mid-2020, the final Austin SHINES report will be published.
About the author: Troy Nergaard is senior director of product management and analytics at Doosan GridTech and also serves as Austin SHINES controls lead.