Public Service of Colorado seeks approval for solar/battery and battery projects

Public Service Co. of Colorado applied Oct. 29 at the Colorado Public Utilities Commission for approval of two projects, one involving a small solar/battery combination and one employing just batteries, that are intended to in part test the microgrid concept.

These would be the third and fourth Innovative Clean Technology (ICT) projects for this Xcel Energy (NYSE: XEL) subsidiary. In 2009, Public Service sought approval of the first such project, a concentrating solar power thermal project at the company’s coal-fired Cameo generating facility. In 2012, the company obtained final commission approval for a second ICT project known as the Community Energy Storage Project – a photovoltaic solar-to-battery project that was installed at the Solar Technology Acceleration Center (SolarTAC) in Aurora, Colorado. The purpose of the CES Project was to demonstrate how energy storage could assist the company in managing the impact of the variability of high penetrations of distributed solar PV energy on distribution system feeders. 

Like the Cameo and CES Project previously approved by the commission, the third and fourth ICT projects that are the subject of this Oct. 29 application are also intended to further the development, commercialization, and deployment of new power generation and other advanced technologies that are environmentally superior to technologies currently in use. Specifically, they are expected to expand the company’s understanding of the potential benefits of energy storage beyond what it learned through the CES Project.

Rather than simply simulating an environment with high PV penetration, the Stapleton project will be deployed on distribution feeders where the company is experiencing high penetrations of distributed solar generation. In the case of the Panasonic project, the company will be analyzing the benefits of battery storage technology at a location where there is a large commercial installation of distributed solar generation and additionally has functionality as a microgrid.

The Panasonic project consists of three primary components:

  • a 1.3 MW (ac) solar installation;
  • a 1 MW – 2 MWh battery storage system; and
  • the power controls and balance of system.

The solar installation will be owned by Public Service and situated on the parking garage located near the Panasonic building and will be integrated with a high concentration of variable distributed generation within the demonstration area. The storage system will feature a lithium-ion chemical battery that has been sized to enable it to provide the capabilities described above for the benefit of both the company’s distribution system and the host site. A custom power control system designed to manage the battery’s state of charge in a manner which optimizes economic potential will be deployed. Finally, the battery storage system will be set up to enable it to be operated and tested as a microgrid to provide backup power to Panasonic Enterprise Solutions Co. (PESCO) in the event of a grid outage. All assets will be owned and operated by Public Service, with maintenance services being provided by PESCO.

The Stapleton project is expected to consist of utility-sited batteries of varying sizes installed at six different locations along a feeder that already has a significant amount of reverse power flow along with six customer-sited batteries. Battery locations for the utility-sited batteries were identified on either end of the circuit’s half loop and sized to match the entire loop’s reverse power flow. Public Service expects to deploy six utility-sited battery storage systems: two 25 kW – 100 kWh units, two 50 kW – 200 kWh units, and two 75 kW – 300 kWh units.

In these locations the batteries can provide benefit by charging the batteries during excess generation hours and discharging the batteries during peak load hours. The operation of the batteries in this manner will minimize the impacts of solar on the feeder, reduce the peak demand on the feeder, and reduce our marginal cost of energy by storing power at a lower cost of energy and discharging it at a higher cost. For the customer-sited batteries, the company looks to gain some experience with the performance, interaction with on-site solar, and load shifting capabilities of customer-sited energy storage systems.

Public Service estimates that the Panasonic project will cost approximately $10.3 million, plus or minus 10%, of which the company is expected to incur $6.7 million with the remainder of the support being provided by Denver International Airport (DIA) and PESCO. The Stapleton project is expected to cost Public Service approximately $4 million, plus or minus 30%. These costs could potentially be reduced by applying the revenues received through the sale of some carbon credits acquired through the company’s carbon offset pilot program.

For purposes of the Panasonic project the company has partnered with DIA and PESCO, who together are expected to provide approximately $3.6 million in support for the projects and will participate in the battery system testing with Public Service. The company is also soliciting participation by the Electric Power Research Institute (EPRI) and DOE’s National Renewable Energy Laboratory (NREL) in the operational analysis of the Stapleton project and expects to seek the participation of third-party solar providers, acquired through a request for proposals (RFP), in installing the customer-sited batteries that are part of the Stapleton Project.

Company wants to test new ways to distribute and store energy

Chad S. Nickell, the Manager of Distribution System Planning & Strategy of Xcel Energy Services, said in Oct. 29 supporting testimony that the company believes that the proposed demonstrations are advisable at this time for several reasons.

  • First, distributed energy resources (DERs) are becoming more prevalent onutility systems across this country in the form of rooftop solar, community solar and storage solutions. Public Service is currently facing significant solar penetration on some of its feeders and it is in the best interest of customers and the company to understand how and if further penetration can be handled.
  • Second, the proposed demonstrations coincide with efforts to begin the transformation and modernization of the utility’s distribution system. Like most utilities in North America, Xcel Energy’s distribution system was designed primarily for a one-way flow of electricity, from distribution substations out to the customer. Distribution feeders are primarily “radial” in nature, relying primarily on local control schemes and manual operation to operate the distribution system. As the penetration of distributed solar generation increases, two-way power flows will become more commonplace and a more flexible and resilient distribution system will be needed, he said. As part of the modernization of the distribution system, Xcel Energy envisions batteries will play a role in enabling a more resilient and sustainable distribution system that allows customers to choose various DERs.
  • Additionally, the utility industry, driven by interest from stakeholders, customers, and policy makers, is interested in the potential for battery systems to facilitate the integration of renewable energy, enhance reliability of the distribution system, and assist in providing voltage management and peak demand reduction.

“Accordingly, by this Application, we are proposing two energy storage projects to be deployed on feeders serving commercial and residential customers, respectively. Both projects will be located in areas where a high penetration of PV energy generation will be present,” Nickell wrote. “These demonstrations will help us assess the potential for utility-sited and customer-sited energy storage systems to provide multiple benefits to the system and will play a key role for understanding the challenges of integrating batteries onto the distribution system. In addition to understanding storage devises installed on the distribution system, we need to understand how customer-sited batteries with solar behave and influence system operations. The Stapleton project will include the acquisition and installation of customer-sited batteries on customers with rooftop solar.”

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.