Product Abstract

Many factors -- including restructuring of the electric utility industry and an increased demand for electricity -- are driving the adoption of distributed energy technologies. This primer outlines the potential impacts that distributed generation and energy storage technologies (collectively called distributed energy resources) may have on utility distribution company planning. The primer focuses on distributed generation technologies with a capacity of 500 kW to 5 MW as well as energy storage systems with capacities up to 15 MW and ride-through times as high as several hours.

Background

On the distribution level, the traditional approach ("poles and wires" solutions) to meet growing electric demand involves the installation of additional equipment such as transformers, protection equipment, and feeders. Long time periods are frequently required to recover the cost of these expensive capital investments. Distributed energy resources (DER) may present the utility distribution company (UDC) with the opportunity to potentially defer, or in some cases eliminate, these costly capital investments. Ultimately, however, the competitive market may drive DER implementation more so than capital investment needs. EPRI sponsored this primer to help UDC planners evaluate the many DER-related issues, including DER applications, impacts of DER on the distribution system, and regulatory issues related to DER ownership.

Objective

To provide UDC planning personnel with the information necessary to make informed decisions about the use of emerging DER technologies as a substitute for, or a complement to, traditional distribution system operations.

Approach

The project team sought to provide UDC planners with a briefing on DER technologies and issues surrounding their implementation. They compiled this primer using in-house EPRI and Energy International resources. Sample distribution planning methodologies and other input from EPRI-member utilities also provided valuable information. Five case studies are included in which UDCs installed particular DER technologies as a means of transmission and distribution (T&D) support.

Results

DER technologies provide a number of important benefits to electricity suppliers and energy consumers. Electricity suppliers gain opportunities for improving efficiency in power generation and distribution, while customers obtain innovative solutions to their energy needs. These resources can be positioned close to the point of use or geographically dispersed throughout a utility's service territory. They can also be interconnected to the utility's distribution or sub-transmission system. In a relatively small number of installations, grid support applications have utilized DER.

The first step in increasing support for DER is for UDC planners and regulatory agencies to become educated on DER technologies and the hurdles that remain in the way of widespread implementation. UDC planning methods can then be modified to incorporate the complicated DER cost-benefit structure. Only then can DER be compared on an "apples-to-apples" basis with traditional poles and wires solutions for T&D grid support applications.

This primer covers the following topics: distribution planning, grid constraints and potential DER applications, issues related to DER implementation, DER technology overview, a description of traditional solutions versus DER solutions for grid support, and case studies for five DER technologies. Appendices to the primer provide a detailed analysis of five DER technologies that fall within the scope of this project -- internal combustion engines, combustion turbines, fuel cells, flow batteries, and superconducting magnetic energy storage.

EPRI Perspective

This report is intended to provide UDC planners with the basic information necessary to consider DER in the planning process. However, in order for UDC planners to successfully and cost-effectively implement these resources as a means of deferring or avoiding T&D upgrades, they must fully understand the unique DER characteristics. Tools need to be developed to help planners quantify the many primary and secondary benefits of DER and select technologies for specific applications. While this primer covers a wide spectrum of topics and is necessarily limited in the depth of its scope, other EPRI tools and products may provide UDC planners with a more detailed assessment of specific DER topics.