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Summary
Renewable resources⎯the sun, wind, water, and biomass⎯were the first to be
tapped to provide heat, light, and usable power. But throughout the 20th century and
today, dramatically increasing use of energy for industrial, residential, transportation, and
other purposes has been fueled largely by the energy stored in fossil fuels and, more
recently, supplied by nuclear power. Linked to the exploitation and development of high-
energy-density resources such as coal and oil at the scales required for powering the
modern U.S. energy system are potentially significant environmental and other impacts.
Concern about greenhouse gases released by the combustion of these fuels, for example,
and awareness of eventual limits on the supply of fossil fuel resources have strengthened
interest in expanding the use of renewable energy resources. Escalations in energy
prices, increasing worldwide demand for energy, and the need to ensure U.S. energy
security have also combined to put energy in the headlines, increasing policymakers’
interest in domestically produced renewable energy.
As part of the America’s Energy Future (AEF) project initiated by the National
Academy of Sciences and the National Academy of Engineering (Appendix A), the
National Research Council convened the Panel on Electricity from Renewable Resources
(Appendix B) to examine the technical potential for development and deployment of
renewable electricity technologies. The full statement of task is provided in Box P-1 in
the preface.
As a result of its study, the panel found that technologies for generation of
electricity from renewable resources represent a significant opportunity⎯with attendant
challenges⎯to provide low carbon dioxide (CO2)-emitting electricity generation from
resources available domestically and to generate new economic opportunities for the
United States. Sufficient domestic renewable resources exist to allow renewable
electricity to play a significant role in future electricity generation and thus help confront
issues related to climate change, energy security, and the escalation of energy costs.
Generation of electricity from renewable resources has increased substantially
over the past 20 years. As shown in Chapter 1, some sources have sustained a 20 percent
or higher compound annual growth rate in capacity expansion and electricity generation
over the past decade. However, non-hydroelectric renewable resources still provide only
a small percentage of total U.S. electricity generation (about 2.5 percent of all electricity
generated), even with these large recent growth rates. The most recent U.S. Energy
Information Agency projections, which are presented in Chapter 1, indicate that under
“business as usual” scenario, the share of electricity generated from non-hydroelectric
renewable resources in 2030 would be only 8 percent of the total U.S. electricity
generated.
The panel concluded that sustained actions involving the coordination of policy,
technology, and capital investment will be essential to achieving a greatly increased
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market penetration of renewable electricity. All three of these factors are important
because improvements in the economics of renewable electricity generation, large
increases in the scale and rate of deployment, and the establishment of consistent long-
term policies are all required in order for renewables to make a material contribution (i.e.,
at a level directly relevant to the future electricity system) to the nation’s energy supply.
Although continued technological advances are critical, the degree of penetration by
renewable electricity will also be determined by actions that collectively center on
sustainably improving the economic competiveness of electricity generated from
renewable versus other resources and on policy initiatives that have a positive impact on
competitive balance and the ease of deployment of renewable electricity.
CHALLENGES AND OPPORTUNITIES AHEAD FOR
THE USE OF RENEWABLE ELECTRCITY
Immense challenges are presented by the need to reduce the vulnerabilities
associated with climate change, energy supply interruptions, and volatile fossil fuel
markets. Reducing electric-sector CO2 emissions by significant levels will require major
changes in how we use and produce electricity. Cutting energy imports and substantially
reducing our dependence on fossil fuels also will involve major changes. Reliance on a
greater amount of renewable energy, particularly renewable electricity, can help address
these challenges. Renewable energy is an attractive option because renewable resources
available in the United States, taken collectively, can supply significantly greater
amounts of electricity than the total current or projected domestic demand. These
renewable resources are largely untapped today.
There are, however, important disadvantages to the use of non-hydropower
renewables for electricity generation. The energy available from renewable resources is
less concentrated than that provided by fossil fuel or nuclear power, posing significant
challenges to the development of renewable resources for electricity generation on a large
scale. To gain the maximum advantage offered by renewable resources, generation
should occur at the site of the resource and accommodate the temporal fluctuations
characteristic of some non-hydropower renewable resources. At high penetrations of non-
hydropower renewable sources, electricity system operators must deal with spatial and
temporal constraints to integrating the generated electricity into the electric grid in ways
that ensure a reliable, controllable supply of electricity. Large penetrations also will result
in land use requirements that in turn can lead to instances of local opposition to the siting
of generation and transmission facilities.
In turn, the use of renewable electricity provides some significant advantages over
the use of fossil-based electricity. Many types of renewable electricity-generating
technologies can be developed and deployed in smaller increments, and constructed more
rapidly, than large-scale fossil- or nuclear-based generation systems, thus allowing faster
returns on capital investments. Generation of electricity from most renewable resources
also reduces vulnerability to increases in the cost of fuels and mitigates many
environmental impacts, such as those associated with atmospheric emissions of
greenhouse gases and emissions of regulated air pollutants. Further, distributed
renewable electricity generation located at or near the point of energy use, such as solar
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photovoltaic systems installed at residential, commercial, or industrial sites, can offer
operational and economic benefits while increasing the robustness of the electricity
system as a whole.
FINDINGS
Shown in bold text are the most critical elements of the panel’s findings based on
its consideration of the material presented in Chapters 2 through 7 of this report.
Time Frames for Renewable Technologies
To better assess the prospects for individual renewable electricity technologies,
the panel separated its consideration of these technologies and their characteristic costs,
performance, and impacts into three time periods: an initial period that considers present
technologies out to the year 2020; a second that considers current and potential renewable
electricity technologies over the 2020 to 2035 time period; and a third period that looks at
technologies beyond 2035.
For the time period from the present to 2020, there are no current
technological constraints for wind, solar photovoltaics and concentrating solar
power, conventional geothermal, and biopower technologies to accelerate
deployment. The primary current barriers are the cost-competitiveness of the
existing technologies relative to most other sources of electricity (with no costs
assigned to carbon emissions or other currently unpriced externalities), the lack of
sufficient transmission capacity to move electricity generated from renewable
resources to distant demand centers, and the lack of sustained policies. Expanded
research and development (R&D) is needed to realize continued improvements and
further cost reductions for these technologies. Along with favorable policies, such
improvements can greatly enhance renewable electricity’s competitiveness and its level
of deployment. Action now will set the stage for greater, more cost-effective, penetration
of renewable electricity in later time periods. It is reasonable to envision that,
collectively, non-hydropower renewable electricity could begin to provide a material
contribution (i.e., reaching a level of 10 percent level or more with trends toward
continued growth) to the nation’s electricity generation in the period up to 2020
with such accelerated deployment. Combined with hydropower, total renewable
electricity could approach a contribution of 20 percent of U.S. electricity by the year
2020.
In the period from 2020 to 2035, it is reasonable to envision that continued
and even further accelerated deployment could potentially result in non-
hydroelectric renewables providing, collectively, 20 percent or more of domestic
electricity generation by 2035. In the third time frame, beyond 2035, continued
development of renewable electricity technologies could potentially provide lower
costs and result in further increases in the percentage of renewable electricity
generated from renewable resources. However, achieving a predominant (i.e., >50
percent) level of renewable electricity penetration will require new scientific
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advances (e.g., in solar photovoltaics, other renewable electricity technologies, and
storage technologies) and dramatic changes in how we generate, transmit, and use
electricity. Scientific advances are anticipated to improve the cost, scalability, and
performance of all renewable energy generation technologies. Moreover, some
combination of intelligent, two-way electric grids; scalable and cost-effective methods
for large-scale and distributed storage (either direct electricity energy storage or
generation of chemical fuels); widespread implementation of rapidly dispatchable fossil-
based electricity technologies; and greatly improved technologies for cost-effective long-
distance electricity transmission will be required. Significant, sustained, and greatly
expanded R&D focused on these technologies is also necessary if this vision is to be
realized by 2035 and beyond.
Resource Base
Solar and wind renewable resources offer significantly larger total energy
and electricity potential than do other domestic renewable resources. Although solar
intensity varies across the nation, the land-based solar resource provides a yearly average
of more than 5 × 1022 J (13.9 million TWh) and thus exceeds, by several thousand-fold,
present annual U.S. electrical energy demand, which totals 1.4 × 1019 J (~4,000 TWh).
Hence, at even modest conversion efficiency, solar energy is capable, in principle, of
providing enormous amounts of electricity without stress to the resource base. The land-
based wind resource is capable of providing at least 10 percent to 20 percent, and in some
regions potentially higher percentages, of current electrical energy demand. Other (non-
hydroelectric) renewable resources can contribute significantly to the electrical energy
mix in some regions of the country.
Renewable resources are not distributed uniformly in the United States.
Resources such as solar, wind, geothermal, tidal, wave, and biomass vary widely in space
and time. Thus, the potential to derive a given percentage of electricity from
renewable resources will vary from location to location. Awareness of such factors
is important in developing effective policies at the state and federal level to promote
the use of renewable resources for generation of electricity.
Renewable Technologies
Over the first time frame through 2020, wind, solar photovoltaics and
concentrating solar power, conventional geothermal, and biomass technologies are
technically ready for accelerated deployment. During this period, these technologies
could potentially contribute a much greater share (up to ~10 percent of electricity
generation) of the U.S. electricity supply than they do today. Other technologies,
including enhanced geothermal systems that mine the heat stored in deep low-
permeability rock and hydrokinetic technologies that tap ocean tidal currents and wave
energy, require further development before they can be considered viable entrants into
the marketplace. The costs of already-developed renewable electricity technologies will
likely be driven down through incremental improvements in technology, “learning curve”
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technology maturation, and manufacturing economies of scale. Despite short-term
increases in cost over the past couple of years, in particular for wind turbines and solar
photovoltaics, there have been substantial long-term decreases in the costs of these
technologies, and recent cost increases due to manufacturing and materials shortages will
be reduced if sustained growth in renewable sources spurs increased investment in them.
In addition, support for basic and applied research is needed to drive continued
technological advances and cost reductions for all renewable electricity technologies.
In contrast to fossil-based or nuclear energy, renewable energy resources are more
widely distributed, and the technologies that convert these resources to useful energy
must be located at the source of the energy. Further, extensive use of intermittent
renewable resources such as wind and solar power to generate electricity must
accommodate temporal variation in the availability of these resources. This variability
requires special attention to system integration and transmission issues as the use of
renewable electricity expands. Such considerations will become especially important at
greater penetrations of renewable electricity in the domestic electricity generation mix. A
contemporaneous, unified intelligent electronic control and communications system
overlaid on the entire electricity delivery infrastructure would enhance the viability
and continued expansion of renewable electricity in the period from 2020 to 2035.
Such improvements in the intelligence of the transmission and distribution grid could
enhance the whole electricity system’s reliability and help facilitate integration of
renewable electricity into that system, while reducing the need for backup power to
support the enhanced utilization of renewable electricity.
In the third time period, 2035 and beyond, further expansion of renewable
electricity is possible as advanced technologies are developed, and as existing
technologies achieve lower costs and higher performance with the maturing of the
technology and an increasing scale of deployment. Achieving a predominant (i.e., >50
percent) penetration of intermittent renewable resources such as wind and solar into the
electricity marketplace, however, will require technologies that are largely unavailable or
not yet developed today, such as large-scale and distributed cost-effective energy storage
and new methods for cost-effective, long-distance electricity transmission. Finally, there
might be further consideration of an integrated hydrogen and electricity transmission
system such as the “SuperGrid” first championed by Chauncey Starr, though this concept
is still considered high-risk.
Economics
A principal barrier to the widespread adoption of renewable electricity
technologies is that electricity from renewables (except for electricity from large-
scale hydropower) is more costly to produce than electricity from fossil fuels without
an internalization of the costs of carbon emissions and other potential societal
impacts. Policy incentives, such as renewable portfolio standards, the production
tax credit, feed-in tariffs, and greenhouse gas controls, thus have been required, and
for the foreseeable future will continue to be required, to drive further increases in
the use of renewable sources of electricity.
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Unlike some conventional energy resources, renewable electricity is considered
manufactured energy, meaning that the largest proportion of costs, external energy, and
materials inputs, as well as environmental impacts, occur during manufacturing and
deployment, rather than during operation. In general, the use of renewable resources for
electricity generation involves trading the risks of future cost increases for fossil fuels
and uncertainties over future costs of carbon controls for present fixed capital costs that
typically are higher for use of renewable resources than for use of fossil fuels. Except for
biopower, no fuel costs are associated with renewable electricity sources. Further, in
contrast to coal and nuclear electricity plants, in which larger facilities tend to exhibit
lower average costs of generation than smaller plants, for renewable electricity the
opportunities for achieving economies of scale are generally greater at the equipment
manufacturing stage than at the generating site itself.
The future evolution of costs for generation of electricity from renewable
resources will depend on continued technological progress and breakthroughs. It
will also depend on the potential for policies to create greater penetration and to
accelerate the scale of production⎯largely an issue of long-term policy stability and
policy clarity. Markets will generally exploit the lowest-cost resource options first, and
thus the costs of renewables may not decline in a smooth trajectory over time. For
example, in the case of wind power, the lowest-cost resources are generally available at
the most accessible sites in the highest wind class areas. Development of these prime
resources will thus entail significant resource cost shifts as markets adjust to exploit next-
tier resources. At present, onshore wind is an economically favored option relative to
other (non-hydroelectric) renewable resources, and hence wind power is expected to
continue to grow rapidly if recent policy initiatives continue into the future.
Although some forecasts show that biopower will play an important role in
meeting future renewable portfolio standards targets, the degree of competition with and
recent mandates for use of liquid biofuels for providing transportation fuel and, of course,
the use of biomass for food, agricultural feed, and other uses will impact the prospects for
greater use of biomass in the electricity market. The future of distributed renewable
electricity generation from sources such as residential photovoltaics will depend on how
its costs compare to the retail price of power delivered to end users, on whether prices
fully reflect variations in cost over the course of the day, and on whether the external
costs of fossil-based electricity generation are increasingly incorporated into its price.
Formulation of robust predictions about whether the price of electricity will
meet or exceed the price required for renewable sources to be profitable and what
their resulting level of market penetration will be remain a difficult proposition.
Comparisons between past forecasts of renewable electricity penetration and actual
data show that, while renewable technologies generally have met forecasts of cost
reductions, they have fallen short of deployment projections. Further, the profitability
and penetration of electricity generated from renewable resources may be sensitive to
investments in energy efficiency, especially if efficiency improvements are sufficient to
meet growth in the demand for electricity or lower the market-clearing price of
electricity. If the financial operating environment for fossil fuel and other in-place
sources of electricity remains unchanged, then the competitiveness of renewable
electricity may be affected more than that of other electricity sources. However, at this
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time, the deployment of renewable electricity is being driven by tax policies, in particular
by the renewable production tax credit, and by renewable portfolio standards.
Environmental Impacts
Renewable electricity technologies have inherently low life-cycle CO2
emissions as compared to fossil-fuel-based electricity production, with most
emissions occurring during manufacturing and deployment. Renewable electricity
generation also involves inherently low or zero direct emissions of other regulated
atmospheric pollutants, such as sulfur dioxide, nitrogen oxides, and mercury.
Biopower is an exception because it produces NOx emissions at levels similar to those
associated with fossil fuel power plants. Renewable electricity technologies (except
biopower, high-temperature concentrated solar power, and some geothermal
technologies) also consume significantly less water and have much smaller impacts
on water quality than do nuclear, natural gas-, and coal-fired electricity generation
technologies.
Because of the diffuse nature of renewable resources, the systems needed to
capture energy and generate electricity (i.e., wind turbines and solar panels and
concentrating systems) must be installed over large collection areas. Land is also
required for the transmission lines needed to connect this generated power to the
electricity system. But because of low levels of direct atmospheric emissions and water
use, land use impacts tend to remain localized and do not spread beyond the land areas
directly used for deployment, especially at low levels of renewable electricity
penetration. Moreover, some land that is affected by renewable technologies can also be
used for other purposes, such as the use of land between wind turbines for agriculture.
However, at a high level of renewable technologies deployment, land use and
other local impacts would become quite important. Land use impacts have caused, and
will in the future cause, instances of local opposition to the siting of renewable
electricity-generating facilities and associated transmissions lines. State and local
government entities typically have primary jurisdiction over the local deployment of
electricity generation, transmission, and distribution facilities. Significant increases in the
deployment of renewable electricity facilities will thus entail concomitant increases in the
highly specific, administratively complex, environmental impact and siting review
processes. While this situation is not unique to renewable electricity, nevertheless, a
significant acceleration of its deployment will require some level of coordination and
standardization of siting and impact assessment processes.
Deployment
Policy, technology, and capital are all critical for the deployment of
renewable electricity. In addition to enhanced technological capabilities, adequate
manufacturing capacity, predictable policy conditions, acceptable financial risks,
and access to capital are all needed to greatly accelerate the deployment of
renewable electricity. Improvements in the relative position of renewable electricity
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will require consistent and long-term commitments from policy makers and the public.
Investments and market-facing research that focuses on market needs as opposed to
technology needs are also required to enable business growth and market transformations.
Successful technology deployment in emerging energy sectors such as renewable
electricity depends on sustained government policies, both at the project and program
level, and continued progress requires stable and orderly government participation.
Uncertainty created when policies cycle on and off, as has been the case with the federal
production tax credit, can hamper the development of new projects and reduce the
number of market participants. Significant increases in renewable electricity generation
will also be contingent on concomitant improvements in several areas, including the size
and training of the workforce; the capabilities of the transmission and distribution grids;
and the framework and regulations under which the systems are operated. As with other
energy resources, the material deployment of renewable electricity will necessitate large
and ongoing infusions of capital. However, renewable energy requires a greater
allocation of capital than the conventional fossil-based energy technologies to
manufacturing and infrastructure requirements.
Integration of the intermittent characteristics of wind and solar power into
the electricity system is critical for large-scale deployment of renewable electricity.
Advanced storage technologies will play an important role in supporting the
widespread deployment of intermittent renewable electric power above
approximately 20 percent of electricity generation, although electricity storage is not
necessary below 20 percent. Storage tied to renewable resources has three distinct
purposes: (1) to increase the flexibility of the resources in providing power when the Sun
is not shining or the wind is not blowing, (2) to allow the use of energy on peak when its
value is greatest, and (3) to facilitate increased use of the transmission line(s) that connect
the resource to the grid. The last is particularly relevant if the resource is located far from
the load centers or if the system output does not match peak load times well, as is often
the case with wind power. However, wind power’s development is occurring long
before widespread storage will be economical. Although storage is not required for
continued expansion of wind power, the inability to maximize the use of transmission
corridors built to move wind resources to load centers represents an inefficient
deployment of resources. Several parties are currently exploring the co-location of
natural-gas-fired generation and other types of electricity generation with wind power
generation to bridge this gap between storage technology and asset utilization. The co-
siting of conventional dispatchable generation sources (such as natural-gas-fired
combustion turbines or combined cycle plants) with renewable resources could serve as
an interim mechanism to increase the value of renewable electric power until advanced
storage technologies are technically feasible and economically attractive. The location of
such natural gas fired generation could be at, or near the wind resource, or at an
appropriate site within the control area. Another possibility is the co-siting of two (or
more) renewable resources, such as wind and solar resources, which might on average
interact synergistically with respect to their temporal patterns of power generation and
needs for transmission capacity.
Finally, it is important to note that the deployment needs and impacts from
renewable electricity deployment are not evenly distributed regionally. Development of
solar and wind power resources has been growing at an average annual rate of 20 percent
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and higher over the past decade. Overall electricity demand is forecasted to continue to
grow at just under 1 percent annually until 2030, with the southeastern and southwestern
regions of the United States expected to see most of this growth. Although some of this
growth may correspond to areas where renewable resources are available, some of it will
not, indicating the possible need for increases in electricity transmission capacity.
Scale of Deployment
An understanding of the scale of deployment necessary for renewable
resources to make a material contribution to U.S. electricity generation is critical to
assessing the potential for renewable electricity generation. Large increases over
current levels of manufacturing, employment, investment, and installation will be
required for non-hydropower renewable resources to move from single-digit- to
double-digit-percentage contributions to U.S. electricity generation. The Department
of Energy’s study of 20 percent wind penetration discussed in Chapter 7 demonstrates the
challenges and potential opportunities⎯100,000 wind turbines would have to be
installed; $100 billion dollars’ worth of additional capital investments and transmission
upgrades would be required; 140,000 jobs would have to be filled; and more than 800
million metric tons of CO2 emissions would be eliminated. In the panel’s opinion,
increasing manufacturing and installation capacity, employment, and financing to
meet this goal by 2030 is doable, but the magnitude of the challenge is clear from the
scale of such an effort.
Integration of Renewable Electricity
The cost of new transmission and upgrades to the distribution system will be
important factors when integrating increasing amounts of renewable electricity. The
nation’s electricity grid needs major improvements regardless of whether renewable
electricity generation is increased. Such improvements would increase the reliability of
the electricity transmission system and would reduce the losses incurred with all
electricity sources. However, because a substantial fraction of new renewable electricity
generation capacity would come from intermittent and/or distant sources, increases in
transmission capacity and other grid improvements are critical for significant penetration
of renewable electricity sources. According to the Department of Energy’s study
postulating 20 percent wind penetration, transmission could be the greatest obstacle to
reaching the 20 percent wind generation level. Transmission improvements can bring
new resources into the electricity system, provide geographical diversity in the
generation base, and allow improved access to regional wholesale electricity
markets. These benefits can also generally contribute positively to the reliability,
stability, and security of the grid. Improvements in the system’s distribution of
electricity are needed to maximize the benefits of two-way electricity flow and to
implement time-of-day pricing. Such improvements would more efficiently
integrate distributed renewable electricity sources, such as solar photovoltaics sited
at residential and commercial units. A significant increase in renewable sources of
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power in the electricity system would also require fast-responding backup
generation and/or storage capacity, such as that provided by natural gas
combustion turbines, hydropower, or storage technologies. Higher levels of
penetration of intermittent renewables (above about 20 percent) would require batteries,
compressed air energy storage, or other methods of storing energy such as conversion of
excess generated electricity to chemical fuels. Improved meteorological forecasting could
also facilitate increased integration of solar and wind power. Hence, though
improvements in the grid and related technologies are necessary and valuable for other
objectives, significant integration of renewable electricity will not occur without
increases in transmission capacity as well as other grid management improvements.
FUTURE PROSPECTS FOR RENEWABLE ELECTRICITY
Currently, use of renewable resources for electricity generation generally incurs
higher direct costs than those currently seen for fossil-based electricity generation, whose
price does not now include the costs associated with carbon emissions and other unpriced
externalities. Some form of market intervention or combination of incentives is thus
required to enable renewable resources to contribute substantially to the national
electrical energy generation mix. Sustained, consistent, long-term policies that provide
for production tax credits, market incentives, streamlined permitting, and/or renewable
portfolio standards are essential to support significant growth of the market for renewable
electricity. With such policies and economic incentives in place, up to 20 percent of
additional domestic electricity generation could come from non-hydropower renewable
technologies within approximately the next 25 years.
In turn, significant technological and scientific barriers must be surmounted if
renewables are to provide upwards of 50 percent or more of domestic electricity
generation in a reliable, controllable system that also has a low carbon emissions
footprint. The barriers include those related to transmission as well as system integration
and flexibility, including storage and other enabling technologies. Specifically, large-
scale and distributed electrical energy storage, and/or large capacities for rapidly
controllable low-carbon-emission generation, would be required to reach such a goal.
Further, a systemwide intelligent, digitally controlled grid could reduce the need for
backup power and storage and further facilitate the penetration of renewable electricity
into the marketplace. Significant research and development is required now if such
technologies are to be available in time to facilitate deployment of renewable electricity
at a level of 50 percent or higher. Research is also needed to ensure that large-scale
deployment of renewable electricity will not lead inadvertently to undesirable
environmental consequences.
CRITICAL UNKNOWNS
The panel notes that many major unknowns will affect the future of electricity
from renewable resources. Several are highlighted below.
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Technologies⎯The prospects for reducing manufacturing costs and improving the
efficiencies of renewable electricity technologies, including the potential for solar
photovoltaics to bring the installed system cost down to less than $1 per watt with at least
10 percent module and system efficiency to enable widespread deployment without
subsidies;
Economics⎯The price of electricity in the future and how prices will be
structured (i.e., real-time pricing) and the explicit or implicit price of CO2 imposed by
any future climate policy;
Policy⎯The structure of renewable portfolio standards, tax policies (production
and/or investment tax credits), and other policy initiatives directed at renewable
electricity;
Biomass⎯The contribution of biomass to electricity production versus the use of
the biomass energy resource base devoted to liquid fuels;
Transmission⎯The mechanisms and responsibilities for increases in transmission
capacity and other upgrades for the electricity grid; and
Transportation⎯The degree to which renewable electricity can influence the
transportation sector and reduce dependence on imported oil and liquefied natural gas
through, in the near term, charging vehicle batteries and, in the long term, producing non-
petroleum-based fuels.
CONCLUSION
A future characterized by a large penetration of renewable electricity represents a
paradigm shift from the current electricity generation, transmission, and distribution
system. There are many reasons why renewable electricity represents such a shift,
including the spatial distribution and intermittency of some renewable resources, and
issues related to greatly increasing the scale of deployment. Wind and solar, renewable
energy resources with the potential for large near-term growth in deployment, are
intermittent resources that have some of their base located far from demand centers. The
transformations required to incorporate a significant penetration of additional renewables
include transformation in ancillary capabilities, especially the expansion of transmission
and back-up power resources, and deployment of technologies that improve grid
intelligence and provide greater system flexibility. Further, supplying renewable
resources on a scale that would make a major contribution to U.S. electricity generation
would require vast investment in and deployment of manufacturing and human resources,
as well as additional capital costs relative to those associated with current generating
technologies that have no controls on greenhouse gas emissions. The realization of such a
future would require a predictable policy environment and sufficient financial resources.
Nevertheless, the promise of renewable resources is that they offer significant
potential for low-carbon generation of electricity from domestic sources of energy that
are much less vulnerable to fuel cost increases than are other electricity sources. Overall
success depends on having technology, capital, and policy working together to enable
renewable electricity technologies to become a major contributor to America’s energy
future.
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