Energy Storage Toolkit
Energy storage technologies absorb energy from an external
source to be discharged at a later time. The Energy Storage Toolkit
offers curated resources and guidance on integrating commercially
available energy storage technologies into the power system.
Welcome to the Energy Storage Toolkit. On these pages, you will find resources that
have been expertly curated and annotated to assist you in navigating key topics
related to deploying and integrating energy storage into electric power systems.
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Background and Context
What is the Energy Storage toolkit?
Storage Location
Grid Integration
Reading List and Case Studies
Background and Context
Energy storage technologies are capable of absorbing energy from an external
source and discharging this energy at a later time. The emergence of lower cost
storage technologies—in particular, electrochemical storage technologies—has
created new opportunities for shifting energy supply and demand in the power
system. As developing countries continue to deploy increasing levels of renewable
energy, energy storage can facilitate the integration of these renewable energy
resources through the provision of various types of grid services. Furthermore,
energy storage can provide additional services to support grid reliability and enhance
resilience.
What is the Energy Storage Toolkit?
The Energy Storage Toolkit focuses primarily on those commercially available
technologies that are currently most likely to be deployed in developing countries—
predominantly pumped-storage hydropower and electrochemical batteries (typically
lithium-ion). Thermal energy storage and other energy storage technologies that are
used in more unique power sector applications are not featured because they are not
commonly used in developing countries. The Energy Storage Toolkit includes
information on key topics, including:
Technology basics
Grid services and value stacking
Markets and regulation
Grid codes, interconnection, and safety
Modeling and planning
Procurement, financing, and business models.
Storage Types and Location
Energy storage systems can be broadly categorized based on (1) where they are
interconnected (e.g., as front-of-the-meter, behind-the-meter, or off-grid systems);
and (2) the medium for energy storage (e.g., electrochemical, thermal, mechanical,
etc.). The type of technology selected and the point of interconnection greatly affect
whether energy storage is a viable option. Different energy storage technologies can
have dramatically different operating characteristics (such as the speed at which
they can charge or discharge, and the power or energy density), which in turn
influences the services that energy storage can best provide. Where storage
systems are interconnected influences various aspects such as appropriate
technology selection, system sizing, and relevant energy and reliability services
offered. There are four main categories for energy storage based on where they
interconnect to the power system:
Behind-the-meter (BTM) — these are small systems located directly at the
customer premises, connected on the customer side of the meter. Often, these
systems are used to provide backup power or power-quality-related services to
the system owner. However, as communication, telemetry, and inverter
equipment improve, these systems are increasingly being used to provide
distribution-level services in a more coordinated fashion to utilities. In some
advanced markets, BTM systems are also being aggregated to provide
transmission-level services.
Front-of-the-meter (FTM) — these systems are much larger than BTM systems
and supply services to the distribution or transmission system, such as ancillary
services, load shifting and/or voltage support. They are directly connected to the
distribution system rather than located behind a given customer’s meter.
Utility-scale — these systems, which are the largest, are connected at the
transmission level to provide services such as system frequency regulation, load
following and/or other ancillary services.
Off-grid systems — these systems are isolated from, and operate independently
of, the centralized grid, although they may provide many of the same critical
services as storage interconnected to the centralized grid such as load shifting
and voltage support, among others.
Grid Integration
Power system flexibility is necessary to safely and reliably integrate high levels of
variable renewable energy. Although energy storage technologies can increase
power system flexibility, storage is not required to integrate variable renewable
energy, and there are no universally applicable methods for determining how much
storage is necessary. Instead, a power system’s specific characteristics—including
its generation mix, demand profiles, and interconnections with other power systems,
among other factors—influence whether and to what extent storage technologies are
necessary and appropriate, or whether other sources of flexibility should be
considered instead.
Interested in partnering through Greening the Grid to receive technical assistance
on energy storage? Please contact us to learn more and explore opportunities for
collaboration.
Reading List and Case Studies
Energy Storage Requirements for Achieving 50% Solar Photovoltaic Energy
Penetration in California
National Renewable Energy Laboratory, 2016
This report estimates the storage required for high PV penetration on the grid (up to
50% annual solar PV penetration in California with total annual renewable
penetration over 66%), and quantifies the complex relationships among storage, PV
penetration, grid flexibility, and PV costs due to increased curtailment. The authors
find that storage needs depend strongly upon the amount of other flexibility
resources deployed and the penetration of solar PV on the system. Lower levels of
power system flexibility require relatively higher levels of energy storage to achieve
the same level of PV penetration while ensuring that PV remains cost-competitive
with conventional combined-cycle gas generators. Without energy storage to shift
energy supply and demand, and assuming constant levels of power system
flexibility, increasing levels of PV penetration lead to additional PV curtailment,
reducing the overall value of the next PV system to the grid (measured in the study
as the net marginal levelized cost of electricity). Thus, energy storage can play an
important role in preserving the value of solar PV to the power system, especially at
higher penetrations of solar PV.
The Value of Energy Storage in Decarbonizing the Electricity Sector
Argonne National Laboratory and Massachusetts Institute of Technology, May 2016
This paper examines the value of energy storage in grid decarbonization efforts by
using forecasts of hourly electricity demand in Texas in 2035. The authors determine
the optimal mix of thermal and renewable resources given various operational limits
and assuming different scenarios of installed energy storage capacity and
CO2 emission limits. Results suggest that the value of short duration (2-hour) energy
storage is only economical at today's costs under strict emission limits, while longer
duration (10-hour) energy storage could provide value at costs similar to pumped
storage hydropower. Longer duration energy storage systems were also better able
to maintain their value as the penetration of energy storage in the grid increased,
whereas short duration energy storage saw declining marginal value under higher
penetration scenarios.
Battery Storage in New Zealand
Transpower New Zealand Limited, September 2017
This study by New Zealand’s grid owner and system operator explores the value of
battery energy storage to electricity consumers and the New Zealand electricity
system. Findings specific to New Zealand’s electricity market suggest that:
The greatest value is in behind-the-meter applications
Existing market tools limit consumer participation in the various energy markets
The potential value of each service provided by storage varies widely based on
physical location
Dynamic retail tariff design such as time-of-use pricing could improve the
economic value of batteries
Behind-the-meter batteries and grid-scale batteries are expected to be
economically viable by 2020 and 2022, respectively.
Flexibility in 21st Century Power Systems
National Renewable Energy Laboratory and others, 2014
This paper discusses the role that flexibility plays in power systems, as this provides
the ability of a power system to respond to changes in demand and supply. Flexibility
is especially prized in twenty-first century power systems, with higher levels of grid-
connected variable renewable energy (primarily wind and solar). Energy storage,
while more expensive than interventions in markets and system operating practices,
is among the flexibility options considered.
The Storage Energy Toolkit is supported by the United States Agency for
International Development (USAID)
