This document is the first in a series of three papers aiming at raising awareness on long duration energy storage (i.e. more than around 6 hours of storage). The first paper outlines that long-term studies show a strong potential for long duration energy storage, the second will show that frequency regulation should not be considered as the only market for energy storage because there is a strong signal for long duration energy storage, while the last paper will compare long duration energy storage technologies.

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THE CASE FOR LONG-DURATION ENERGY STORAGE:
A 3-CHAPTER STORY BY CLEAN HORIZON AND HIGHVIEW POWER STORAGE
Chapter 1: Long term studies show a strong potential for long duration energy storage
September 2014
This document is the first in a series of three papers aiming at raising awareness on long
duration energy storage (i.e. more than around 6 hours of storage). The first paper outlines
that long-term studies show a strong potential for long duration energy storage, the second
will show that frequency regulation should not be considered as the only market for energy
storage because there is a strong signal for long duration energy storage, while the last
paper will compare long duration energy storage technologies.
Introduction
The media spotlight is currently set on
short-term electricity storage, with much
discussion of frequency regulation as the
major revenue source. FERC order 755
has given birth to numerous storage
projects with flywheels and ‘less-than-an-hour’
batteries taking advantage of better
revenues offered to fast assets providing
frequency regulation, especially in the PJM
area of the US.
However, renowned long term studies
assessing the need for storage for the
decades to come, be it at a national or
global level, agree on future projections of
a significant requirement for energy
storage as well as power storage, meaning
6 hours or more worth of discharging
power.
Discussion
As figure 1 below shows, the market for
this type of storage is worth billions of
dollars in every country studied, from
$12bns in France in 2030 to $766bns
worldwide in 20501.
1 $247,000/MWh was taken as an assumption for
investment costs. It is an average of long duration
storage technologies CAPEX : Pumped Hydro,
Compressed Air and Liquid Air Energy Storage. A
duration of around 10 hours was also assumed for all
technologies.
Investors and regulators dedicated to
energy storage and focusing only on intra-hour
technologies are at risk of missing a
significant opportunity in the longer
duration end of the storage market. Even
France, which is not considered as having
the most significant storage potential, will
have a market worth billions of dollars.
Figure 1 – Evaluation of Future Market
Sizes for Daily Storage in Literature
Indeed, the International Energy Agency,
in its Technology Roadmap: energy
storage, evaluates the additional
requirement to be 310 GW by 2050. IEA
reports are a strong basis for all high-level
policies in the member countries.
This 310 GW figure is computed over
Europe, the US, India and China in order

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to accommodate for the renewable
growth and to limit global warming by 2°C
by 2100 (2DS scenario). The 310 GW
concerns four technologies: PHES, CAES,
flow batteries and batteries. Given the
comparative sizes of these systems, the
larger part of the capacity can be inferred
to be related to long-duration storage
(PHES, CAES, flow batteries).
German research organization Fraunhofer
undertook a study to assess the feasibility
of a 100% renewable electricity mix by
20502. The results showed such a mix
would be possible with a large amount of
storage: 56 GWh of battery, mostly in
residential systems, 60 GWh of PHES, and
69 GWel / 68 TWh of Power to Gas.
In France, a study3 was financed by the
French Agency for the environment and
energy management (ADEME) and the
ATEE, an association of companies
involved in the electricity market and
storage (e.g. EDF, DGF, Total). ADEME is
authoritative in all issues related to
energy and environment in France, and
this study is a reference when speaking
about French storage.
This study estimates a need for 50 GWh
more of weekly storage by 2030. Although
the study identifies pumped hydro as the
only suitable technology, other large
storage technologies are not excluded
provided a significant drop in investment
costs occurs. Long duration storage will
serve multiple purposes including:
arbitrage, capacity market (a guaranty of
generation capacity), and longer duration
ancillary services.
2 100 Percent Renewables for Electricity and Heat –
The Role of Storage in a Future German Energy System,
2013.
3 Étude sur le potential du stockage d’énergies, Artelys,
ENEA Consulting, G2Elab, 2013.
In the US, a report from Sandia National
Laboratories4 estimated the potential for
storage applications of 6 hours or more to
be 50 GW in 2020 (Electric Energy Time
Shift and Demand charge management).
This 2010 study is renowned through the
storage sector, all the more so because it
paved the way for the DOE/EPRI 2013
Electricity Storage Handbook in
Collaboration with NRECA.
In 2050, NREL foresees5 at minimum a
100 GW storage requirement to sustain an
80% renewable scenario, mostly under
the form of Compressed Air Energy
Storage (a longer duration technology).
Conclusion
The potential markets opportunities
identified by the various studies are
computed using different methods, with
different objectives and to show different
results at different dates, so they cannot
be easily compared. However, they come
from various players of the energy sector -
consultancy, research laboratories, and
renowned international agencies - and all
point to the similar result that in order to
achieve a successful energy transition
towards more renewable energies, long-term
storage technologies will play an
important role in the overall plant mix.
________
Clean Horizon is a European consultancy
specialized in energy storage, and
dedicated to helping its clients monetize
energy storage.
Highview Power Storage is a designer
and developer of large-scale energy
storage solutions for utility and
distributed power systems.
4 Energy Storage for the Electricity Grid: Benefits and
Market Potential Assessment Guide, A Study for the
DOE Energy Storage Systems Program, Jim Eyer Garth
Corey, Feb 2010
5 Renewable Electricity Futures Study, vol 2 of 4,
Renewable Electricity Generation and Storage
Technologies, NREL, 2012