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1
Introduction
Increasing renewable energy development, both in the United States
and abroad, has rekindled interest in the potential for marine and hydro-
kinetic (MHK) resources to contribute to electricity generation. In par-
ticular, state-based renewable portfolio standards and federal production
and investment tax credits have led to increased exploration of MHK
technologies. This interest is reflected in the number of requests for per-
mits for wave, current, tidal, and river-flow generators that have been
filed recently with the Federal Energy Regulatory Commission (FERC);
as of December 2012, FERC had issued 4 licenses and 84 preliminary
permits while an additional 42 projects are in the pre-filing stage for a
license.1 Though permit activity is not a reliable predictor of the future
development of MHK resources because developers apply for permits
before completing project plans and financing, it does indicate increased
interest in MHK resource development. However, most of these permits
are for developments along the Mississippi River, and the actual deploy-
ment of all MHK resources is extremely small. The first U.S. commercial
grid-connected project, a tidal project in Maine with a capacity less than
1 megawatt (MW), is currently delivering a fraction of that power to the
grid and is due to be fully installed in 2013.
In response to the rising interest in MHK energy, the Energy Policy
Act of 2005 (Public Law 109-58) directed the Department of Energy (DOE)
1 Available at http://www.ferc.gov/industries/hydropower/gen-info/licensing/ ydrokinetics.
h
asp. Accessed January 3, 2013.
13
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14 DOE’S MARINE AND HYDROKINETIC RESOURCE ASSESSMENTS
to estimate the size of the MHK resource base. In order to assess the
overall potential for U.S. MHK resources and technologies, DOE funded
detailed resource assessments for estimating what it terms the “maxi-
mum practicably extractable energy” or “maximum practical, extractable
energy” for each resource (see Appendix A for the funding announce-
ments), as well as projects for generating the technological data necessary
to estimate the expected performance of several MHK device designs cur-
rently under consideration (DOE, 2008 and 2009). The objective of DOE’s
MHK resource assessment work was to help prioritize its overall portfolio
of future research, increase understanding of MHK’s potential for generat-
ing electricity, and steer the developers of MHK devices and/or projects
to locations of greatest promise.2 Earlier estimates (EPRI, 2005 and 2007)
of the potential MHK resource are based on limited, possibly inaccurate
data and assumptions related to the total resource and the fraction that
might prove extractable.
DOE contracted with five assessment groups to conduct separate
estimates of the extractable energy from five categories of MHK resources:
waves, tidal currents, ocean currents, marine temperature gradients (also
known as ocean thermal energy conversion [OTEC]), and free-flowing
water in rivers and streams (DOE, 2010). The resource assessment groups
are listed in Table 1-1. Each group was tasked with estimating the average
power density of the resource base, as well as basic technology charac-
teristics for potential devices and spatial and/or temporal variability of
the resource. DOE requests for proposals did not offer a unified frame-
work for the efforts, nor was there a requirement that the contractors
coordinate their methodologies. As a result, each assessment group used
distinct methodologies and assumptions, although there is some com-
monality between assessments being overseen by the same groups. The
DOE contracts did specify that each assessment would have a validation
component; those groups are also listed in Table 1-1.
DOE asked the National Research Council (NRC) to convene a com-
mittee of experts to evaluate the detailed assessments produced by each
group, review the estimates of extractable energy, typically represented
as average terawatt-hours per year (TWh/yr),3 and technology specifi-
2 H.Battey, U.S. Department of Energy, “DOE Water Power Program,” Presentation to the
committee on February 8, 2011.
3 Note that TWh/yr is a unit of power and may be used to represent the average power
generation over the time period indicated (1 gigawatt [GW] = 8.8 TWh/yr, 1 TWh/yr = 0.114
GW). However, a unit such as TWh/yr (or, as shown in an electricity bill, kilowatt-hours
[kWh] per month) is a standard unit for the electricity sector. Energy units such as kWh or
TWh measure the commodity that is generated by power plants and sold to consumers. For
example, the Energy Information Agency’s (EIA’s) Annual Energy Review 2011 includes a
table of total electricity generation that is given in billions of kWh/yr (EIA, 2012, Table 8.2a).
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INTRODUCTION 15
TABLE 1-1 MHK Resource Assessment and Validation Groups
Contracted by DOE
Resource
Assessment Assessment Group Validation Group
Tides Georgia Tech Research Corporation Oak Ridge National
Laboratory
Waves Electric Power Research Institute, National Renewable
Virginia Tech Energy Laboratory
Ocean currents Georgia Tech Research Corporation Oak Ridge National
Laboratory
Marine temperature Lockheed Martin, National Renewable
gradients/OTEC Florida Atlantic University, Energy Laboratory
University of Hawaii
Rivers and streams Electric Power Research Institute, National Renewable
University of Alaska Energy Laboratory
cations, and compare the results across resource types. The committee
members had expertise in oceanography, ocean engineering, hydraulics,
civil engineering, electric power engineering and electric utilities, energy
economics, and environmental and resource policy; their biographies can
be found in Appendix C. The complete statement of task (SOT) can be
found in Box 1-1. As requested in the SOT, the committee completed an
interim report with initial commentary and review of the draft wave and
tidal resource assessments. That report, Assessment of Marine and Hydro
kinetic Energy Technology: Interim Letter Report (NRC, 2011), was released
on July 12, 2011, and is reproduced in Appendix B. In it, the commit-
tee concluded that the wave and tidal assessments would be useful for
determining the theoretical and technical resources, but it had concerns
about the usefulness of producing a single-number estimate for the entire
United States. It also noted a lack of consistency and coordination across
the assessments. Each of these points will be discussed in full in this report.
A CONCEPTUAL FRAMEWORK FOR
MHK RESOURCE ASSESSMENT
The nation’s MHK community currently lacks a well-defined, con-
sistent resource terminology. The committee observed that each of the
assessment groups employed different terminology to describe similar
results. This was likely due to imprecise language in the DOE fund-
ing opportunity announcements (DOE, 2008 and 2009), which called for
an assessment of the “maximum practicably extractable energy” or the
“maximum practical, extractable energy” without defining the terms. In
addition, the NRC statement of task used language (“extractable energy,”
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16 DOE’S MARINE AND HYDROKINETIC RESOURCE ASSESSMENTS
BOX 1-1
Statement of Task
This committee will evaluate detailed assessments produced by the U.S.
Depart ent of Energy (DOE) of the extractable energy from U.S. marine and
m
hydrokinetic (MHK) resources (waves, tidal currents, ocean currents, marine tem-
perature gradients, and free-flowing water in rivers and streams); review extract-
able energy estimates and technology specifications; and accurately compare
the results across resource types. There are five assessments that will need to
be evaluated by the committee addressing: (1) wave energy resources; (2) tidal
energy resources; (3) hydrokinetic energy in streams and rivers; (4) marine hermal
t
energy; and (5) ocean current energy. In addressing its statement of task, the
committee will:
(1) nteract with the principal investigators of each individual assessment devel
I
oped by DOE to understand and question their approach and perhaps
suggest additional information or methodological approaches to facilitate
consistent comparison across the assessments;
(2) eview and assess MHK technology-related data, critically analyzing meth-
R
odologies, technical robustness, reliability, and assumptions related to the
performance of the various technologies under consideration;
(3) eview and assess each of the resource assessments, critically analyz-
R
ing methodologies, technical robustness, and assumptions related to the
resources that might be practicably available for energy conversion and
potential limitations on these resources;
(4) ased on its review and critique of the assessments, provide a defensible
B
comparison of the potential extractable energy from each of the resource
types;
(5) ake recommendations, as appropriate, for improving the assessments,
M
improving the consistency among the assessments, or for improving the
methodologies for making the assessments;
(6) rite an interim report reviewing the methodologies and assumptions, and
W
provide any recommendations associated with the first two assessments
being undertaken by DOE (wave and tidal energy); and
(7) rite a final report reviewing all five of the assessments.
W
“potential extractable energy”) different from what DOE used for its fund-
ing opportunity statement.
In order to develop its approach to the SOT and to review individual
resource assessments within a single context, the committee created a con-
ceptual framework (Figure 1-1) of the overall MHK resource assessment.
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INTRODUCTION 17
FIGURE 1-1 Conceptual framework developed by the committee for MHK re-
source assessments. The asterisk in the third column denotes that the resource
assessment groups did not attempt to evaluate the practical resource.
This allowed the committee and those who read its reports to visualize the
processes used to develop the assessment results requested by DOE. This
framework establishes three terms—the theoretical resource, technical
resource, and practical resource—to clarify the overall resource assess-
ment process as described by each assessment group and to allow for a
comparison of different methods, terminology, and processes among the
five assessment groups. Each of the three terms is defined in the follow
ing sections.
The committee recognizes that communities involved with other
energy types, such as wind and fossil fuels, use different terms to describe
their resource bases (such as “resources” or “proven reserves”). The com-
mittee’s framework is consistent with terminology for MHK resources
as used in the European marine energy community, including European
Marine Energy Centre (EMEC)4 terminology incorporated in International
Electrotechnical Commission (IEC) technical specification 62600-1 (IEC,
2011). In addition, the committee created Table 1-2, which contains the
definitions and units used in this report.
S-11
4 Available at http://www.emec.org.uk/standards.asp.
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TABLE 1-2 Terminology and Definitions Used by the Assessment Groups
18
Term to Be Quantified Definition Unit Note
General
Energy Capacity to do work joules (J)
Power Energy per time watts (W) = J/s
Flux Rate of flow of a property per unit area
Resource Average annual power TWh/yr Representing a potential energy
(1 TWh/yr = 114 MW) resource base for the electricity
sector in TWh.
Tides, ocean currents, and riverine/in-stream
2
Current power Power of horizontal currents flowing through a W/m Horizontal kinetic energy
density vertical plane of unit area. flux (power density). Applies
1 to a single device. Excludes
P = ρv3 consideration of back effects.
2
Waves
Wave power density Power of waves per unit crest length based on W/m Horizontal energy flux. Applies
∞
(Mei, 1989) to a single device. Vector
0
P = ρ g ∫ S ( f ,θ )c g df
quantity (has both direction and
magnitude).
Wave power density Power of waves per unit circle based on W/m Horizontal energy flux. Applies
∞ 2π
(EPRI, 2011) S ( f ,θ )c g dθ df to a single device. Scalar quantity
0 0
P = ρg∫ ∫ (has no directional information).
Ocean thermal
3
Ocean thermal Net extractable power per unit flow of W/(m /s) Net power from pumping
3
power density upwelled cold water 1 m /s of cold water without
2
(Nihous, 2007a) P ρCP × TGE × ( ∆T ) (1 − PL ) consideration of back effects on
= the ocean.
QCW 8 ( 273 + TS )
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NOTE: Variables are as follows:
ρ, water density;
v, tidal/ocean/river current speed (scalar);
g, gravitational acceleration;
S, wave spectrum (sea-surface height variance, per frequency and direction);
cg, wave group velocity;
f, wave frequency;
θ, wave direction;
CP, heat capacity of seawater (J/(K kg));
TGE, OTEC turbo-generator efficiency (~0.8-0.9);
ΔT, temperature difference between warm and cold water for OTEC plant (°C);
PL, pipe loss/fractional energy loss to cold water pumping (~0.2-0.3); and
TS, warm water intake temperature for OTEC (°C)
19
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20 DOE’S MARINE AND HYDROKINETIC RESOURCE ASSESSMENTS
Theoretical Resource
The theoretical resource, shown in the left column of the concep-
tual framework in Figure 1-1, is defined as the average annual energy
available from each MHK resource. Determining the theoretical resource
requires a series of inputs (including methods, models, assumptions, and
observational data) for each source of MHK energy (waves, tides, ocean
currents, marine temperature gradients, and rivers and streams) in order
to determine the physical upper limit on the total amount of available
energy. For waves, the theoretical resource is effectively the power density
of waves approaching the shore (see Table 1-2). For in-stream power from
rivers, the theoretical resource is the power that is lost to friction as water
flows from higher to lower ground.
For some of the theoretical resource assessments, it is also important
to consider far-field back effects. These refer to the modification of an
energy resource owing to the presence of an extraction device or devices.
In particular, for tidal currents, ocean currents, and marine thermal gra-
dients, the theoretical resource cannot be estimated without taking into
account the far-field back effect. Here, the back effect refers to the reduced
potential of the resource due to feedbacks from the presence of a device
or device array. For tidal and other ocean currents, placement of a turbine
will create drag, reducing the current velocity and therefore the potential
power available for each turbine. As turbines are added to an array, at
some point the extra power generated by an additional turbine will be
less than the decrease in power due to the reduced current available for
all the other turbines. This maximum available power is equivalent to the
theoretical resource when far-field back effects are considered. Similarly,
the operation of a series of OTEC plants can affect the ocean’s thermal
structure, decreasing the potential power of each plant. Depending on the
community, back effects are also known as feedbacks or blockage effects.
In response to the original DOE request, the assessment groups
produced two key outputs from their characterization of the theoretical
resources: (1) overall regional or national numbers for the U.S. theoreti-
cal resource, expressed as an average annual energy resource (typically
in TWh/yr), and (2) a geographic information system (GIS) database that
represents the spatial variation in average annual power density with
units appropriate for each source (e.g., W/m for waves or W/m2 for
tides). The committee equates the theoretical resource with the “potential
extractable energy” mentioned in the SOT.
Technical Resource
The technical resource (center column in Figure 1-1) is defined as the
portion of the theoretical resource that can be captured using a specified
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INTRODUCTION 21
technology. For each resource, there are technological constraints that
determine how much of the theoretical resource can actually be extracted.
The committee conceptualizes these constraints as physical and techno-
logical extraction filters. These include physical near-field (local) back
effects from turbine interactions in a river channel or wave system as
well as technological characteristics associated with one or more energy-
extraction devices: characteristics such as device efficiency, device spac-
ing requirements, drag on supporting structures, and cut-in and cut-out
parameters (the minimum or maximum speeds at which devices can oper-
ate). Some of these filters are resource-specific; others are applicable across
all MHK resources. During presentations from DOE and the assessment
groups and ensuing discussion with the committee, it became clear that
each group offers a different interpretation of what types of constraints
would need to be included among its extraction filters. However, it is
clear to the committee that estimating the technical resource from the
theoretical resource requires filters that represent the general physical
and technological constraints associated with energy-extraction devices.
In-water or field tests would assist in the quantification of realistic extrac-
tion filters and/or device-specific conversion efficiencies, because the data
obtained could be used to calibrate numerical models. Outputs related to
the technical resource include an estimate of the energy resource and a
GIS that sets forth spatial and temporal variation in the resource associ-
ated with various technologies. In the committee’s view, the assessment
groups determined that reporting the technical resource (rather than the
practical resource) represented the completion of their projects. The com-
mittee equates the technical resource with the review of “extractable
energy” charged in the SOT.
Practical Resource
The committee also recognizes that, beyond the extraction filters,
there are additional filters influencing when and where devices can be
placed. The practical resource (right-hand column in Figure 1-1) is defined
as that portion of the technical resource available after consideration of
all other constraints. In the conceptual framework, these constraints are
represented as social, economic, regulatory, and environmental filters. For
example, some of the filters attempt to capture the logistical and economic
considerations associated with building the MHK devices and connecting
them to the electricity system, which could include costs of extraction and
electricity delivery. Environmental constraints related to quantifying the
practical resource include issues such as protecting threatened species
or ecologically sensitive areas. Other use issues include sea–space con-
flicts raised by, for instance, shipping channels, navigation, and military
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22 DOE’S MARINE AND HYDROKINETIC RESOURCE ASSESSMENTS
considerations and multiple- or competing-use issues such as fisheries
or recreation. Such filters are, by nature, specific to the local sites where
decisions related to MHK projects will be made. The practical filters can
greatly influence the timing of the permitting process and can lead to
unpredictable consequences, which in turn can affect a project’s economic
viability. Box 1-2 presents two scenarios to help elucidate the differences
between the theoretical, technical, and practical resource.
BOX 1-2
The Theoretical, Technical, and Practical Resource
MHK resource assessments are going to be of interest to a variety of par-
ties, including electric utilities, project developers, and public officials. However,
the orders-of-magnitude differences between theoretical, technical, and practical
resources need to be stressed, especially because some resource assessments
have been publicized in terms of a national or regional single-number estimate.
To provide a better understanding of the difference among these resources, two
scenarios are provided below.
• Scenario 1. A local official examines one of the MHK GIS databases and
notes that there is a 100 MW theoretical resource nearby. After taking into
account the efficiency of the extraction device, such as a turbine (30%),
coverage of the resource by the device(s) (20%), and the efficiency of
connecting the extracted energy to the electricity grid (90%), the technical
resource amounts to only 5.4 MW. The local official notes that 50 percent
of the remaining power would interfere with existing fisheries and navigation
routes in the area, leaving a practical resource of 2.7 MW.
• Scenario 2. A developer is interested in building a 100 MW MHK plant.
This would be considered the desired practical resource. In this case, 20
percent of the site is unavailable because it is in a Marine Protected Area.
After taking into account device efficiency, site coverage, line efficiency, and
the practical constraints posed by the use conflict, the site of interest would
have to be endowed with a theoretical resource of 2,300 MW.
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INTRODUCTION 23
In its funding opportunity announcements (DOE, 2008 and 2009),
DOE requested that the assessment groups determine the “maximum
practicably extractable energy,” which the committee originally inter-
preted as equivalent to the practical resource called for in the conceptual
framework. After discussion with both DOE and the assessment groups,
the committee concluded that the groups had interpreted “maximum
practicably extractable energy” to mean the technical resource and that
DOE did not expect the assessment effort to incorporate site-specific infor-
mation needed to quantify the practical resource.
While a determination of the practical resource is beyond the scope of
the tasks assigned by DOE, the committee sees the constraints represented
by the socioeconomic and environmental filters as being among the most
important considerations influencing future MHK investments. Box 1-3,
which discusses these types of constraints on the development of solar
energy, is presented as an example of what might be needed to assess the
MHK practical resource. These filters are also central to evaluating the
potential maximum contribution of MHK to U.S. electricity generation.
The socioeconomic and environmental filters that need to be considered
in an assessment of the MHK resource are described further in Chapter 7.
BOX 1-3
Determining the Difference Between the Theoretical and
Practical Resource: Solar Energy as a Case Study
Assessing the potential for a particular renewable technology to address U.S.
energy needs based on the theoretical resource alone would be inappropriate. As
an example, solar power plants (which were first constructed nearly 30 years ago)
currently provide less than 0.1 percent of the electricity consumed in the United
States despite having a theoretical resource base that is orders of magnitude
larger than current U.S. electricity consumption (EIA, 2012). While national-scale
resource assessments may be useful for identifying geographic regions of inter-
est for a particular MHK extraction technology, the practical resource will depend
on a host of technical and environmental factors and may be significantly lower
than what the assessments indicate is regionally or locally available. A survey of
a
nnual total energy outputs from several existing solar plants indicates that the
ratio of plant outputs to the locally available theoretical resource ranges from as
little as 2 percent for photovoltaics to as much as 12 percent for concentrated solar
( ational Renewable Energy Laboratory [NREL], available at http://www.nrel.gov/
N
gis/solar.html; EIA, available at http://www.eia.gov/electricity/data/eia923/index.
html). It is not possible to predict the practical MHK resource from national resource
assessments until the constraints posed by both the technical extraction filters and
the practical socioeconomic and environmental filters are better quantified for each
of the specific resources.
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24 DOE’S MARINE AND HYDROKINETIC RESOURCE ASSESSMENTS
It is also important to note the difference between utility-scale and
small scale developments, as these terms are mentioned throughout the
report. Utility-scale MHK developments would produce from tens to
h
undreds of megawatts and would require significant infrastructure and
fully-proven MHK devices rather than prototypes. Utility-scale MHK
deployment has the greatest potential for substantial environmental
impacts as well as conflicts with other ocean and freshwater uses. In
comparison, smaller-scale developments would typically produce less
than 10 MW and potentially have fewer conflicts and adverse impacts.
Small MHK developments could be deployed in locations with high
local resource availability and low electricity demands (such as remote
villages or small islands) or in locations that lack interconnection to a
utility-scale electricity system. Additionally, a project developer would
need to prove the feasibility of a smaller-scale pilot application before a
utility would invest in building a utility-scale system. The regional- to
global-scale approach used by the resource assessment groups was a top-
down evaluation that is most useful in understanding the utility-scale
potential for MHK.
THE “SINGLE NUMBER” ESTIMATE FOR
RESOURCE ASSESSMENTS
Although each of the five MHK resource assessments is evaluated
in detail in Chapters 2 through 6, here the committee draws attention
to an important point that applies to the assessments both individually
and for the project as a whole. The committee is concerned about the
appropriateness of aggregating the results of individual MHK resource
assessments to produce a national or regional single-number estimate
of the theoretical and/or technical resource for any one of these energy
sources. It finds that the theoretical resource assessments, especially when
examined at a regional or national scale, have limited utility for devel
opers and stakeholders and also have potential for misuse. As an exam-
ple, the numbers associated with the wave and tide assessments do not
accurately convey how the theoretical resources are concentrated along
the coast, nor do they explain how much power would be practically
available once devices are deployed. Although such estimates provide
a broad order-of-magnitude idea of potential energy resources, many
extraction filters are needed to determine the technical resource, and
at this time the assessment groups can rigorously evaluate only a few
of these filters. Most of the extraction filters require assumptions about
which particular MHK technologies will be used and what their techni-
cal specifications will be; moreover, the technologies are likely to vary by
resource and location—for instance, wave energy off the coast of Oregon
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INTRODUCTION 25
and ocean current energy in the Florida Straits. In addition, socioeconomic
and environmental filters will ultimately limit the practical resource to
only a fraction of the technical resource, so it is unlikely that the resource
assessments, which at best provide only a partial assessment of the techni-
cal resource, could serve as a defensible estimate of the available practical
resource. Although DOE may want overall numbers in order to compare
individual MHK resources with one another or with other renewable
resources, a single number is of limited value for understanding the
potential contribution of MHK resources to U.S. utility-scale electric-
ity generation. Instead, site-by-site analysis will be needed to estimate
the resource that might ultimately be available for electricity generation.
This number is likely to be much smaller than the numbers generated by
national resource assessments.
COORDINATION AND CONSISTENCY
Another issue that applies broadly to the entire DOE-funded assess-
ment efforts was the coordination among and consistency between
individual resource assessments. These efforts suffered from a lack of
coordination and consistency in terms of methodology, validation, and
deliverable products. Each of the assessment groups chose its own meth-
odologies, and while the committee understands that there was likely to
be variation simply because the resource types differ, greater coordination
at the outset could have discerned some commonalities that would have
allowed easier comparison of the assessments. In addition, each valida-
tion group chose its own method, which also led to inconsistent results.
In some cases, the method appeared to be less of a validation than a
spot-checking of results with varying degrees of thoroughness. The com-
mittee is also concerned about the scientific validity of some assessment
conclusions; these concerns are addressed in later chapters. The lack of
coordination and consistency also affected the GIS database products.
While some are already integrated into GIS Web applications hosted by
DOE’s National Renewable Energy Laboratory (MHK Atlas and River
Atlas5), others are currently hosted on platforms operated by individual
assessment groups. Given that one of DOE’s objectives is to compare
the various MHK resources with one another and with other renewable
energy resources, the lack of coordination and consistency between the
assessment groups was counterproductive.
5 Available at, respectively, http://maps.nrel.gov/mhk_atlas and http://maps.nrel.gov/
river_atlas.
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26 DOE’S MARINE AND HYDROKINETIC RESOURCE ASSESSMENTS
REPORT ORGANIZATION
The committee evaluated the five assessments contracted by DOE
(tides, waves, ocean currents, marine thermal gradients/OTEC, and rivers
and in-stream). Each of the assessments is presented in a separate chap-
ter, which introduces the basic resource, describes the project, comments
on assessment methodology and validation, and offers conclusions and
recommendations. The discussion of tides can be found in Chapter 2,
waves in Chapter 3, ocean currents in Chapter 4, OTEC in Chapter 5, and
riverine and in-stream flows in Chapter 6. A discussion of the practical
MHK resource and constraints posed by socioeconomic and environ-
mental filters is included in Chapter 7, and overarching conclusions and
recommendations are presented in Chapter 8.
Evaluations of the resource assessments are based on presentations
by the assessment groups and DOE to the committee at each of its six
meetings (meetings and presentations to the committee are detailed in
Appendix D). The committee also received written responses to its ques-
tions from each of the groups. Chapters 2 and 3 are based on informa-
tion initially discussed in the committee’s interim report (NRC, 2011).
These chapters have been updated to include information that had not
been available at the time of the interim report release. For this report,
the committee reviewed final assessment reports for the waves, tides,
and OTEC assessment groups and a July 2012 draft final report from the
iverine assessment group.6 No final report was available for review from
r
the ocean currents resource assessment group; its report is expected to be
complete by June 2013. Instead, the committee based its evaluation on
presentations from and discussions with the assessment group.
6 The final report was published in December 2012 and is available at http://www.epri.
com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000000001026880.
