Solar Energy Technologies Office

Multi-Year Program Plan

May 2021

SETO Multi-Year Program Plan

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Disclaimer

This work was prepared as an account of work sponsored by an agency of the United States

or imply its endorsement, recommendation, or favoring by the United States Government or any agency

thereof or its contractors or subcontractors. The views and opinions of authors expressed herein do not

necessarily state or reflect those of the United States Government or any agency thereof, its contractors

or subcontractors.

SETO Multi-Year Program Plan

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Authors

Main author:

Timothy J Silverman*, National Renewable Energy Laboratory (NREL)

Contributing author for Systems Integration:

Henry Huang, Pacific Northwest National Laboratory (PNNL)

Acknowledgments

Ketan Ahuja, Paul Basore, Matt Bauer, Brion Bob, Michelle Boyd, Shamara Collins, Andrew

Dawson, Megan Decesar, Zachary Eldredge, Kyle Fricker, Tassos Golnas, Susan Huang, Victor

Kane, Inna Kozinsky, Hariharan Krishnaswami, Susanna Murley, Garrett Nilsen, Emanuele

Pecora, Ammar Qusaibaty, Avi Shultz, Nicole Steele, Lenny Tinker, Elaine Ulrich, Chani Vines,

Allan Ward, Dawn Washelesky, Guohui Yuan, Leah Zibulsky

And support from everyone on the SETO team. Thank you.

* Timothy J Silverman was on assignment to SETO in 2020, when much of this document was written.

This work was authored in part by the National Renewable Energy Laboratory, operated by Alliance for

SETO Multi-Year Program Plan

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Letter from the Director

more than 30-fold to reach 3% today. Yet an even greater rate of change and

electricity grid by 2035. For solar technology, this likely means providing 30%–

50% of electricity, with as much as a terawatt of solar capacity by 2035.

Solar technology has advanced rapidly over the past decade — for example, solar panel efficiencies increased by

30%, trackers became cost-effective, and solar power electronics developed capabilities to provide a broad array

of grid services — and the costs of solar electricity have fallen by roughly 80%. These advances provide

confidence in our ability to rapidly innovate to meet the Nation’s climate goals. At the same time, it is critical that

we bring increased focus to reducing soft costs and ensuring equitable access to the environmental, economic, and

deployment, and enable solar technology to meet energy needs beyond electricity.

and draft these goals. This plan reflects the collective expertise of SETO’s talented teams, representing countless

hours of conversations and analysis. Most of the goals in this plan were presented at the 2020 SETO Peer Review,

where we received feedback from solar industry experts, business leaders, researchers, and other stakeholders

who will be instrumental in achieving these goals.

Just as the solar industry met and exceeded ambitious targets we set in the past, we know that the creativity and

ingenuity of the solar community will enable us to meet these goals and inspire us to be even more ambitious in

the years to come.

Thank you for taking the time to read our multi-year plan.

SETO Multi-Year Program Plan

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Table of Contents

Vision and Mission ................................................................................................................................................3

Vision .................................................................................................................................................................3

Shared Challenges .............................................................................................................................................3

Mission ..............................................................................................................................................................4

Federal Role of the Office ......................................................................................................................................4

Scope..................................................................................................................................................................4

Types of Projects ...............................................................................................................................................5

Maturity Level ...................................................................................................................................................5

Energy Justice and Equity..................................................................................................................................5

Technology and Market Overview .........................................................................................................................5

Plan ........................................................................................................................................................................... 11

Photovoltaics ........................................................................................................................................................11

Background ......................................................................................................................................................11

Goals ................................................................................................................................................................12

Approach ..........................................................................................................................................................12

Concentrating Solar-Thermal Power ....................................................................................................................16

Background ......................................................................................................................................................16

Goals ................................................................................................................................................................17

Approach ..........................................................................................................................................................17

Systems Integration ..............................................................................................................................................22

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Approach ..........................................................................................................................................................29

Manufacturing and Competitiveness ....................................................................................................................33

Background ......................................................................................................................................................33

Goals ................................................................................................................................................................34

Approach ..........................................................................................................................................................34

Analysis .................................................................................................................................................................... 35

Program Evaluation .................................................................................................................................................. 36

Statutory Authority ................................................................................................................................................... 37

References ................................................................................................................................................................ 39

SETO Multi-Year Program Plan

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Executive Summary

demonstration, and deployment assistance for solar energy. We advance national progress on climate action, clean

Our vision is for solar energy to play a fundamental role in reaching the Nation’s clean energy goals and resolving

the climate crisis. Our mission is to accelerate the advancement and deployment of solar technology. Everything

we do advances solar technology’s ability to provide low-cost and reliable electricity, rapid deployment, and

energy beyond electricity.

areas: photovoltaics (PV), concentrating solar-thermal power (CSP), systems integration (SI), soft cost reduction

(SC), and manufacturing and competitiveness (MC).

SETO Multi-Year Program Plan

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SETO Multi-Year Program Plan

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Office Overview

Technologies Office (SETO) is part of the Office of

We advance national progress on climate action,

This is SETO’s Multi-Year Program Plan for fiscal

years 2021 through 2025. The Multi-Year Program

Plan explains the purpose and the priorities of the

jobs and economic growth. We are committed to

SETO Multi-Year Program Plan

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Report Title

11

Plan

than electricity from conventional generation. Cost

succeed. Accordingly, until recently, reducing the

electricity, rapid deployment, and energy beyond

electricity. We use a more comprehensive set of

targets than cost alone to track progress on these

priorities.

prioritize reliability, rapid deployment, and energy

beyond electricity. Several of these goals deal with

the integration of solar technology with adjacent

domains, such as the power system, energy storage,

land use, structures, the economy, and the

environment. We still maintain cost reduction goals

so that solar energy can be affordable across the

CSP, systems integration, soft cost reduction, and

manufacturing and competitiveness. Our work in

each budget area is relevant to different but

overlapping sets of stakeholders. Below, the goals

are organized according to the budget area with

primary responsibility for the goal, but in practice,

some of the goals are pursued across multiple parts

of the program.

transformers, to form a PV power plant or system.

Virtually all PV electricity produced in the nation is

made in PV systems that are connected to the

electricity grid. Utility-scale power plants, roughly 5

megawatts (MW) and larger, provide about 60% of

the nation’s PV capacity [EIA EPM 2021]. The

remaining capacity is split between commercial

systems, up to hundreds of kilowatts (kW), and

Adding a new PV-only power plant to the grid is

often straightforward and economical. But in parts of

Crystalline silicon (c-Si) PV made up 94% of the

global PV market in 2019. Of this, about two-thirds

was monocrystalline silicon and one-third was

multicrystalline. The remaining 6% of the market

was served by cadmium telluride (CdTe, 5%) and

copper indium gallium diselenide (CIGS, 1%)

[SPV 2020]. In the United States, 74% of the utility-

scale PV installed through 2019 was c-Si

technology, and the remaining 26% was CdTe

[EIA‑860 2020]. Commercial and residential PV are

SETO Multi-Year Program Plan

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reduction in the PV module price of 85%, from

$2.51/watt (W) in 2010 to $0.38/W in 2020, and a

reduction in the LCOE of 80% over the same time

period [Feldman 2021].

Planned improvements continue: Cells and modules

may keep getting larger, c-Si cells may move from

heterojunction designs, and the extra energy

produced by bifacial PV systems, which can collect

sunlight from both sides of the PV module, may

be reliable. But most PV systems are less than three

SETO addresses PV challenges in cost reduction,

performance improvement, and life cycle impacts.

explained in detail below.

Reaching our goals depends on cooperation among

academic and National Laboratory researchers, the

PV industry, and the energy financing and

investment communities. Our awardees make new

technology and new practices available to the

industry, which is responsible for adopting,

financing, and implementing them to reduce the cost

of solar electricity.

Lowering the Cost of Energy from PV

energy to continue increasing its support of U.S.

energy system affordability, PV cost reductions must

continue. Today the unsubsidized LCOE of utility-

scale PV systems without battery storage is

competitive with the LCOE of conventional power

plants [Lazard 2020]. But a PV-only system cannot

SETO Multi-Year Program Plan

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<$0.03/kWh in utility-scale PV systems

resource near the national average.

is not a measure of electricity value, reducing LCOE

to less than $0.03 per kilowatt-hour (kWh) would

make the electricity cost from new PV generation

costs, like fuel and maintenance [Lazard 2020]. In

cases where PV generation coincides with load

demand, this makes new PV power plants directly

competitive with existing conventional power plants.

flexibility or new transmission, to be competitive

with new conventional power plants.

Figure 4. Several performance and cost improvements

may contribute to reaching the utility-scale PV LCOE

target. LCOE is shown in 2018 real U.S. cents per kWh.

the cost of PV electricity by increasing the energy a

PV system produces over its service life and by

reducing the costs to build and operate a PV system.

translate these results into real-world LCOE

reductions. Our work delivers advances that will

reach the PV industry in three or more years,

covering topics that are outside the focus and reach

of industrial R&D alone. Our awardees include the

National Laboratories, universities, and the private

sector.

One of the most effective ways to increase energy

production and decrease LCOE is by improving the

efficiency of solar cells and modules. Higher

SETO Multi-Year Program Plan

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technologies—c-Si and CdTe—are mature enough

to directly deliver very-low-cost electricity in 2025,

but the 2025 goal is just the first step toward our

long-term vision. We support continued

improvements to these mainstream products because

they can build on the full-scale industry that is

already in place. But we also explore emerging

technologies serving as models that advance long-

term scientific understanding of PV, such as III-V

materials, made of Group III and V elements in the

and CdTe PV absorbers, the gap between actual

efficiency and theoretical maximum efficiency is

A cell or module with a given indoor-measured

efficiency might deliver different amounts of annual

energy depending on cell design, module design,

system configuration, and system operation. We

support continued increases in energy yield through

innovations in each of these areas.

Our awardees integrate their findings into the

international standards that affect virtually all grid-

connected PV globally.

cost in a utility-scale PV system is spent on

components other than modules and inverters. These

connectors, wiring, combiners, racks, and trackers.

We pursue hardware cost reductions such as new

materials, designs, and manufacturing techniques

(O&M) for PV power plants includes monitoring

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Building on the success of PV cost benchmarks, a

disseminate expert analysis to build awareness and

acceptance of priorities for reducing impacts. Details

of the analysis will be publicly available so others

can assess candidate improvements. Because PV is

an energy generation technology, energy payback

time (EPBT) and energy return on energy invested

to society. The life cycle benchmark will include

metrics like EPBT and EROI alongside more

conventional LCA metrics. Producing a benchmark,

parallel to developing a life cycle benchmark, we

unintended pollution or human health effects, as

specifies a system boundary that includes

as technology changes.

SETO Multi-Year Program Plan

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concentrated sunlight directly, without an

intermediate heat transfer medium, to replace fossil

fuels in emissions-intensive industries.

energy are implemented, CSP plants can act as

CSP plants use a turbine to generate electricity. For

grid integration purposes, CSP turbines have the

same physical properties as the turbines in a

conventional power plant. Combined with their

dispatchability, this clears the way for CSP to

integrate easily with the power grid.

financial risk associated with emerging technology.

Some of this technology exists at various stages of

maturity but still must be integrated and

demonstrated in the field.

There is a path for dispatchable solar electricity and

process heat from a CSP plant to be cost-competitive

Lazard 2020]. Today the unsubsidized LCOE of a

CSP plant with 14 hours of thermal storage is

$0.10/kWh, according to detailed cost models.

We fund R&D and demonstration to support

advancements toward low-cost CSP electricity and

industrial process heat. Our R&D efforts include

materials and fabrication methods, equipment design

and component integration, methods of operation,

and analysis of application of CSP toward multiple

SETO Multi-Year Program Plan

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private-sector investments are necessary to bring

CSP electricity and SIPH technology to scale.

southwest with high direct solar resource. As shown

SETO Multi-Year Program Plan

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A major Gen3 CSP technology effort is already

underway. The Gen3 program has completed

technology development, component validation, and

system design projects for receiver, storage, and heat

exchanger technology using solid, liquid, and

supercritical fluid heat-transfer media. In early 2021,

promising heat transfer medium to achieve SETO

goals. Efforts are now focused on a megawatt-scale

demonstration of this technology before 2025.

These materials include heat-transfer and storage

media and the materials for system components. Our

costs. Supercritical CO

turbines can be applied in

solar, fossil, and nuclear plants and we collaborate

with DOE’s Offices of Fossil and Nuclear Energy to

advance sCO

technology. We also work to realize

efficient integration between sCO

turbines and a

receiver in a CSP system account for 45% of incoming

better materials, better hardware, and better

operational characteristics. Structural cost can be

reduced by replacing steel with lower-cost materials

or by using lighter-weight reflectors. Improved

SETO Multi-Year Program Plan

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As the industry shifts to higher receiver

uniformity at the receiver becomes increasingly

important. Improvements to these aspects of the

heliostat field performance deliver benefits to overall

system efficiency.

risks associated with investing in new CSP

technology by supporting integration and

demonstration. Switching to sCO

power cycles also

substantially reduces the minimum practical size of a

plant. Reduced risk and reduced minimum

increase the capital available to invest in CSP

efficiency power cycle is demonstrated

applies to any power cycle with a net

efficiency exceeding 50%. The sCO

Brayton cycle is currently the most

promising way to achieve this.

Supporting the Reliability of the Power System

stored energy to enhance reliability. Today, batteries

supply peaking capacity, energy time-shifting, and

operating reserves. As the grid integrates more

stored energy to be adjusted independently of the

equipment that uses the energy. Plants using TES

can add storage capacity as demand increases,

without upgrading the plant itself. Our work in

thermal energy storage takes full advantage of

technology developed in the Gen3 CSP program,

described above. Higher temperatures lead to higher

of new and existing materials, components, and

system designs. Reaching high temperatures requires

advanced storage media, component materials, heat

(TES) system configurations with positive NPV are

identified

technoeconomic analysis shows that specific

thermal energy storage systems attached to

technology that originated with CSP has a promising

application in ETES, where electrical energy is

returned. ETES plants use many of the same

components developed for Gen3 CSP and ETES can

be deployed alone or hybridized with CSP plants. As

more variable renewable energy is deployed on the

electricity may increase. We support the component

and system developments necessary to demonstrate

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and control of a power system with major solar

energy contributions will require improved

forecasting, data collection, and analysis

[Golnas 2019]. Solar forecasting needs higher spatial

resolution and wider temporal coverage, ranging

enables the power system to more effectively adapt

to changing conditions, meeting changes in demand

at optimal cost. Less forecast uncertainty and better

(LCOS), which includes the lifetime cost

improve flexibility from other elements in the power

system through integrated resource planning.

[NERC 2017b, Robles 2019]. While the power

system must continue minimizing outages resulting

from these threats, solar technology can help the

power system be more resilient when a disruption

does occur.

During hazards, the power system can be

reconfigured into independent segments that each

contain load and generation. With enough DER such

as PV systems, there are more opportunities for

reconfiguration to enhance grid resilience. The fast-

responding power electronics in solar generation and

back online. Close coordination between DER and

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Realizing fast, adaptive response to physical

disruptions or cyberattacks requires new modeling

and simulation, new analysis, new inverter

capabilities, and field demonstration in partnership

effects of all hazards on power system performance

arising from and affecting solar systems. These

response to cyberattacks and physical disruptions,

supporting new adaptive protection schemes, grid

reconfiguration, emergency load balancing,

islanding, and blackstart. An adaptive grid also

requires technology to identify faults, attacks, and

advanced signal processing and machine learning

techniques to detect, identify, and mitigate these

conditions.

[Matevosyan 2019]. These inverters must also be

cost-effective and support the functions needed to

To resist cyberattacks, inverters must be inherently

cybersecure, implement defense in depth, and

support the cyberdefense of the power system they

are connected to, following the National Institute of

Standards and Technology’s (NIST) cybersecurity

framework [NIST 2018]. Building a trustworthy,

cyber-resilient power system requires developing

innovative, dynamic cybersecurity survival

strategies for solar generation systems, especially

from within a piece of equipment connected

event, but these are rare and not repeatable.

An alternative way of demonstrating this

capability is by combining simulation of the

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and soft costs have changed. Approximately 35% of

utility-scale PV system costs and over 60% of

commercial and residential PV system costs are soft

costs [Feldman 2021].

shown in Figure 10. PII and installation labor

together account for more than a quarter of

residential soft costs. Financing cost, which does not

appear in Figure 10 because it is not part of upfront

solar system costs, is about 40% of the LCOE of a

residential PV system [Feldman 2021].

Figure 10. The cost breakdown of a residential PV

system (top) and a utility-scale PV system (bottom)

show the contributions of soft costs [Feldman 2020].

Hardware costs are shown in red and soft costs in

structural balance of system; PII is permitting,

Further reductions in the cost of PV electricity will

costs [O’Shaughnessy 2019].

Residential PV system cost is over two times higher

in the U.S. than in Germany and over three times

soft costs [WM GSPSP 2021]. In those countries,

permitting and inspection are streamlined and

governed by national rules. U.S. regulations and

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Location-specific requirements and practices

contribute to soft costs. In the United States, there

utilities. Each of these may have different

permitting, inspection, and interconnection processes

and requirements [Burkhardt 2015]. In PV systems

that are combined with storage or other DER, soft

costs are higher than in solar-only systems

[Feldman 2021].

Deploying PV at large scale may bring increased

attention to the optimal use of land. A total of about

1 GW to 2 GW of PV capacity has been deployed

with grazing animals or pollinator habitat

bodies of water. These dual-use systems can yield

reduce water use [Barron‑Gafford 2019]. But dual-

use systems are not common, and the benefits are

In UPV systems, avoiding, minimizing, and

mitigating site impacts can increase costs. These

costs are poorly documented and understood, so are

particularly difficult to reduce [Hartmann 2019].

Lowering the Cost of Energy from PV

the analysis and planning that local jurisdictions

need to cut red tape and make it easier and more

affordable for their residents to go solar. We fund

the collection of data, development of tools, and

provision of technical assistance that can help

streamline permitting, inspection, and

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market information that can support more efficient

decision-making and associated cost reductions. This

information includes, for example, how solar

benchmark costs of different PV market segments,

and training materials for first responders.

to PV systems can enhance the energy resilience of

homes and critical community infrastructure, like

police stations, fire stations, and hospitals, in an

emergency. These combined PV+DER systems,

however, can have much higher soft costs than PV-

only systems. For example, adding battery storage to

[Feldman 2021].

We research siting, PII, and operation of PV+DER

systems and identify ways to reduce these costs with

improvements to technology or information. And we

[Ardani 2018]. Most rooftop PV systems are

implemented as separate roofing and PV products.

Integrating PV and roofing products can reduce

supply chain and installation labor costs. Integrating

the PV and construction industries further reduces

customer acquisition, overhead, and labor costs. And

PV permitting costs can be reduced when the

permitting process is integrated with the permitting

process for a roof replacement, construction of a

new house, or construction of an entire new

neighborhood. Residential LCOE for new

aspects of PV system ownership, financing, and

procurement are unique to commercial rooftops. We

work with commercial building owners to find

commercial PV. Our research on rate designs and

compensation mechanisms helps building owners

make informed decisions. We also study under what

conditions the colocation of energy storage and

electric vehicle charging with commercial PV

systems can provide benefits to the building owner

or tenants.

PV systems and $0.10/kWh for residential PV

systems

model shows that unsubsidized LCOE has

reached the target. This model describes

rooftop commercial and residential PV

systems in Kansas City, Missouri, a location

with solar resource near the national

average.

Our approach prioritizes workers hardest hit by

discrimination, economic exclusion, and exploitation

workers, and frontline communities most affected by

climate and environmental problems. We work to

opportunities, meaningful wages, and labor

SETO Multi-Year Program Plan

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meets the needs of the industry and of disadvantaged

communities and grows to employ at least 300,000

workers

deployment. This deployment is expected to produce

electronics waste is produced than PV waste, but this

may change as PV deployment accelerates

[EPA 2020b, SFS 2021]. In a sustainable energy

system, the materials in PV waste should be

recovered and used again. We support analysis to

energy projects manage the impacts they have on

also studying the ecological impacts of co-locating

PV with pollinator habitat, grazing, and crops.

demonstrated for reducing the environmental impact

of PV technology, prioritized based on a life cycle

impacts benchmark

then new technology has been demonstrated

that reduces environmental impact. This

goal is shared with the PV budget area.

Opening New Markets

deliver mutual benefits [Barron-Gafford 2019]. For

example, a single piece of land can produce revenue

from grazing under PV panels and from the

electricity produced by the panels. When the benefits

of adding PV exceed the costs, a project has positive

with another use, such as agriculture or building

surfaces

excludes conventional residential and

commercial PV, where PV modules are

installed on top of conventional roof

material.

SETO Multi-Year Program Plan

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economic and ecological benefits of pollinator

habitat, interactions with birds, and interactions with

native plants.

Ensuring That Solar Energy Benefits All

Energy consumers who do not have access to

solar energy available to homes and businesses

where rooftop solar is not a practical option. This

the U.S. [Feldman 2015]. It is possible for many

U.S. consumers to save money on electricity by

investing in a solar generation asset through a

solar array. We provide networking, collaboration,

energy consumer by 2025 and enable community

solar to provide meaningful benefits to energy

consumers, workers, employers, and communities.