B08_SOL_DOI-IARPA-BAA_SOLSTICE_Rev1-08122024-Section1_C.pdf

UNCLASSIFIED

SECTION 1: FUNDING OPPORTUNITY DESCRIPTION

IARPA often selects its research efforts through the Broad Agency Announcement (BAA) process. The use of a BAA solicitation allows a wide range of innovative ideas and concepts. The BAA will appear under Contract Opportunities on https://sam.gov and a link will be placed on the IARPA website at https://iarpa.gov. The following information is for those wishing to respond to this Program BAA.

This BAA is issued in accordance with the Federal Acquisition Regulation (FAR) section 6.102(d)(2), which provides for the competitive selection of basic and applied research and that part of development not related to the development of a specific system or hardware procurement. Proposals submitted in response to this BAA that are selected for award are to be in full compliance with Provisions of Public Law 98-369, “The Competition in Contracting Act” of 1984 and subsequent amendments. IARPA is seeking innovative solutions for highly efficient and resilient solar-powered systems to support Intelligence Community (IC) applications in space (Track 1) and terrestrial surface (Track 2) environments.

1.A. Program Background

The Intelligence Community routinely relies upon a variety of stand-alone electronic assets deployed for remote applications. The power systems onboard these devices are essential to ensure mission success.

However, remote devices are often subjected to challenging environmental conditions in space and on the earth (land or water) that degrade or limit power system performance. Power density, weight, and volume are all significant factors that affect the range of possible onboard devices that can be supported by the power system. Some desired higher-power payloads may simply be impractical to implement or must be duty-cycled due to power system limitations. The focus of the SOLSTICE program is to enhance power system-level efficiency and resiliency in the challenging environments in which they are placed to yield significantly more energy for the same size, weight, and area of the power system.

Solar photovoltaic (PV) energy conversion technologies have a long heritage of supporting many remote platforms in all the aforementioned environments. PV cells and modules of different efficiency levels can be tailored for a variety of settings and in a variety of form factors. These are largely commoditized products used across the IC, DoD, and commercial applications alike. Despite the plethora of available options, power and energy needs onboard remote platforms continue to grow. Simply adding additional solar modules to address these needs adds more bulk to the system that complicates transportation, deployment, and/or unobtrusive operation in the target environment. High efficiency (multijunction) solar cell systems, currently used almost exclusively for space, are available from a small number of suppliers and can achieve high conversion efficiencies (~30-33%) at the cell level. However, once typical operating conditions (i.e.

varying irradiance, temperature), power conversion, and system level losses are accounted for, the realized time-weighted efficiency is substantially reduced, limiting available power and energy. Other potential high-power technologies, such as fuel cells and radioisotope thermoelectric generators (RTGs), may be useful in some scenarios, but lack some of solar PV’s key advantages, namely, high modularity, low weight, low noise, safety, and predictable failure modes. The IC needs power systems with a) high energy harvesting yield (EHY) over a mission lifetime, b) high power density per unit of collection area, c) resilience against environmental stressors and human-made physical threats, and d) ease of transportability and deployment.

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1.B. Program Overview

The SOLSTICE program aims to deliver revolutionary advances in ultra-efficient and resilient energy conversion systems (power systems) for application in space (Track 1) or terrestrial surface environments (Track 2). Power systems must use solar energy as an input alone, or, in tandem with other sources available in the surrounding environment. System level performance outcome amid the myriad of changing environmental conditions will be the focus of SOLSTICE. It is expected that significant innovations will be required across a wide range of system components and/or the overarching system design architecture to achieve program technical performance metrics. Approaches that achieve the aforementioned goals and also maximize domestic manufacture and minimize the vulnerabilities in component supply chains are highly encouraged. SOLSTICE requirements suggest the need for cross-collaboration and co-design among Research and Development (R&D) teams to access best of breed talent across the wide range of technical disciplines involved and is therefore highly encouraged. Detailed information about specific goals, objectives, metrics, and milestones can be found in the subsequent sections of this BAA.

SOLSTICE will be structured into three phases. Phase 1 (“Proof of Concept (POC) Development”) will last 18 months during which teams will demonstrate proofs of concept for novel high-risk components and/or integrations of their proposed system design. Performance of these POC demonstrations will be incorporated into system-level models (effectively a “digital twin” of a prototype power system) developed by the Performer and transferred to the SOLSTICE Testing and Evaluation (T&E) partner for evaluation and input into a range of orbital or terrestrial performance models that will be used across SOLSTICE.

Phase I deliverables will include test articles of the novel components and/or integrations as well as conceptual system designs and modeling/calculations extrapolating performance across the set of conditions possible in the target environment(s). Phase 2 (“Prototype Demonstration”) will last 18 months during which teams will assemble a first-generation technology demonstration prototype power system (PPS) combining components proposed by Performers and approved by IARPA in the end of Phase I design plans. Phase 2 will include several PPS test articles (defined in Section 1.E) along with design and modeling work delivered to the SOLSTICE T&E partners for evaluation. Phase 3 (“Scalability and Durability Assessment”) will last 12 months. Phase 3 Performers will iterate their PPS design based on Phase 2 lessons learned and demonstrate a higher-power-output PPS that may take advantage of a larger collection area.

These PPS Test Articles will also undergo preliminary durability and resilience testing to assess reliability in the target environments. By the end of Phase 3, the program aims to demonstrate ultra efficient and resilient PPSs with proven initial designs that show viability for transition and continued development with IC partners.

1.C. Technical Approach Power systems proposed to the SOLSTICE program will need to exhibit the following primary and secondary objectives (see Section 1.F for specific metrics):

Primary Objectives:

• High time-weighted system level energy conversion efficiency (ηsys), resulting in high mission lifetime energy harvesting yield (kWh);

• High system aperture (collection) area power density (Wmp/m2);

• High stowed system volumetric power density (kWmp/m3) for launch and/or transport;

• A reasonably high peak power output (Wmp);

• High system specific power density (Wmp/kg);

• Minimal power output decay over time resulting from environmental conditions and single damage events including physical impact and/or momentary high flux (~100-500 suns) irradiation incidents

• Capacity to supply power across a range of irradiance and load profiles relevant to each Track

Secondary Objectives:

• Reasonable expectation to scale to scale to 10W, 100W, 1kW, 10kW, 100kW power output

• Capable of future integration with appropriate deployment mechanisms for end use cases requiring deployment from an initial reduced-volume state

• Low risk, low cost, domestic manufacturability

• Effective repurposing of thermal waste energy (i.e. temperature regulation, conversion)

In space environments, five-year minimum lifetimes are assumed (stretch target of ten-years) with deployment achieved from an existing launch vehicle. In terrestrial environments, three-year lifetimes are assumed (stretch target of 10-years) with deployment occurring autonomously onto land or water.

To achieve the goals and metrics of the SOLSTICE program (detailed in Section 1.F of this BAA), Offerors will develop systems of co-optimized components that leverage recent and emerging technologies in, for example, solar cells and hybrid power-generation approaches, optics, thermal management, power electronics, and other enabling components to yield power system solutions with unprecedented performance. Concepts could include new 1-sun PV devices, (micro)concentrated solar PV, hybridization of PV with alternative energy conversion or storage devices (e.g. thermoelectric, thermoradiative), innovative power electronics (e.g. photonic transformers, highly discretized power optimization), tunable/adaptive optical materials (thermochromics, electrochromics, metalens optics), new thermal management/storage strategies (e.g. phase change materials, heat pipes, thermal valves), and other solutions that optimize the conversion of sunlight and other energy capturable from the local environment into electricity. Offerors may propose any combination of innovative approaches and/or components to realistically achieve the metrics of the program. Novel approaches towards the design and modeling of materials, components, and/or systems (e.g. potentially leveraging machine-learning, artificial intelligence algorithms) are encouraged. Multidisciplinary teams are expected to achieve the ultimate systems-level optimization sought in the SOLSTICE program. While component development is a key part of earlier phases of the Program, exclusive focus on component technology in the absence of a system level approach toward meeting the SOLSTICE program targets is out of scope. SOLSTICE specifically seeks approaches that leverage co-design of components as part of a holistic system design that maximizes energy harvesting yield and resilience over the course of a mission. Innovations may involve, but are not limited to, the following areas:

Solar Cells and Hybrid Power-generation Structures

Solutions may leverage novel photovoltaic and other photoresponsive materials, cell architectures, and other supporting components to maximize the energy conversion and collection density and/or energy harvesting yield over time from the light aperture area and other portions of the device. Solar cells could be designed for 1-sun or part of a concentrated solar system. Innovations in multijunction and tandem solar cell photoactive materials, device structures, form factors/size, contacts, substrates, coatings, and encapsulation may contribute to increased overall efficiency, durability, and/or manufacturability. New materials or approaches to capture and convert unutilized or poorly converted portions of the solar spectrum to contribute more towards the overall cell, module, or system efficiency could also help deliver the performance required to meet the SOLSTICE program metrics. Devices with improved low-light and/or variable spectrum performance could enhance a system’s energy harvesting yield over a mission. The above approaches could be synergistic with some Thermal Management and Power Electronics solutions (see subsections below) to realize higher power or energy densities. Other approaches that leverage conditions of the local environment to convert or store additional energy may boost the mission lifetime energy harvesting yield. New fabrication methods for components and structures may produce higher performance, greater yield, and/or lower costs than existing methods.

Optics

The efficient capture and direction of light is essential to ensure high collection efficiency, as is the protection of sensitive materials and systems that carry out the photoconversion. Concentrating optics are a known way to improve power density while offering additional protection for the underlying solar cells. Thus far, concentrating optics designs have proven difficult to implement practically due in part to the optical efficiency limitations, sun-pointing angle of acceptance restrictions, thermal management, cost, and deployment challenges that are imposed. However, new approaches to deliver a modest amount of concentrated light to solar absorbers (potentially including micro-concentrators, adaptive optics, spectrum-splitting optics, non-mechanical sun tracking) with low-profile designs that can achieve good sun tracking and be deployable may present options that can achieve the SOLSTICE targets. Robust coatings and protective layers that can maintain high optical efficiency of light collection over time while protecting against environmental stressors (e.g. proton or electron radiation in space, moisture and soiling/abrasion on the earth surface) could support the lifetime energy harvesting yield of power systems in SOLSTICE.

Thermal Management Approaches to properly manage, use, store, and/or reject heat may be important to optimize long-term stability and improve overall performance amid changing environmental conditions. Novel components introduced in other parts of a SOLSTICE system may cause greater localized heating (e.g.

concentrators) which may be able to reduce power needs elsewhere on a spacecraft or terrestrial platform. Approaches that can convert waste heat into useful work or energy could add to the overall annual energy harvesting yield and power density of the power system and/or reduce the heat rejection temperature of waste heat. These approaches could also reduce the impact of “dark cycles” of the power system when sunlight is not available which can place greater demands on the energy storage system.

Macro or micro-scale thermoelectric devices, thermoradiative cells, and thermal energy storage components may offer some opportunities. Coatings, substrates, and other materials that can adapt to changing thermal conditions (e.g. thermochromics) or other stimuli could aid with temporal control of heat flow towards more optimal performance of components and the system as a whole.

Power Electronics Solutions may leverage a number of potential strategies to convert energy into electricity useable by the remote platform, including but not limited to, traditional centrally organized or highly distributed (i.e.

on-wafer cell/subcell-level) power electronic topologies. New approaches and components could improve long-term Energy Harvested Yield by limiting or slowing failure due to environmental and human-created stressors and/or single-event failure modes in the power electronics. By limiting the scope or rate of damage or degradation to key power-conversion components, higher overall lifetime energy harvesting yields at the system level could be realized, even if some portions of the power-conversion system are beyond recovery. These solutions may also result in efficiency improvements in aggregate in circumstances when light absorption is non-optimal (e.g. partial array shading, obstructions, damage, soiling, changing incidence angle) or when other inhomogeneities of the energy collection components are present (e.g. variable temperature, single-cell failures). Approaches to better manage the flow of energy (electrical, thermal, or otherwise), transiently store energy, or otherwise support an energy management system could yield overall efficiency improvements.

Novel Deployment and Survivability Approaches New approaches toward packing/deploying solar arrays, optics, and other portions of the power system may result in greater stowed volumetric power densities that can achieve the SOLSTICE targets.

Methods to stow and protect the aperture area during threatening periods from environmental and/or human-made physical threats could help maximize the lifetime energy yield of the power system.

Autonomous or remotely triggered restorative procedures that repair or regenerate damaged or degraded components could prolong the useful life and mitigate risk. Materials that “self-heal” or otherwise offer greater resilience to the stressors of their environment could also offer promise.

The above-stated components and approaches are examples of the types of innovations sought in this BAA, but potential Offerors should not feel limited to these categories. Any component level or system level innovations or approaches that will aid in reaching the SOLSTICE program targets will be considered.

While solutions proposed to SOLSTICE may include many of the aforementioned innovative components to achieve higher lifetime energy harvesting yield and power density, consideration must be made towards the deployment challenges that may be imposed by novel approaches in the target environment. When appropriately scaled and integrated with necessary autonomous deployment components (not within the scope of this program), power systems destined for space must be able to pack within a launch vehicle, survive launch conditions, and be reliably deployed once in space. Similarly, remote systems intended to be deployed on land or water must start in a reduced-volume packed state and successfully deploy once they reach their target location.

Energy storage is an integral part of a remote power system and SOLSTICE will largely leverage established and high TRL energy storage component technology (e.g. electrochemical cells, supercapacitors, thermal energy storage). Battery cells, packs, and/or other energy storage technologies proposed to be incorporated into a SOLSTICE power system need not be COTS components, but must be sourced from a fabricator/supplier that can provide a specification sheet with accurate, reproducible performance metrics (+/- 10%) that include form factor description, capacity, cycle life, discharge, charge and temperature range performance specifications. The development of novel energy storage chemistries/materials and sub-cell components (i.e. anode, cathode, separator, electrolyte) without standardized performance is out of scope.

However, novel approaches to, for example, support, orient, structure, allocate, manage, and/or control largely demonstrated energy storage components in the context of an overarching SOLSTICE power system design will be considered.

1.D. Program Description and Structure 1.D.1 Program Goals

The SOLSTICE program will pursue two research tracks that target power system development for application in an earth-orbital environment, such as satellite systems (Track 1), and land or water-based application, such as land surface or buoy-mounted devices (Track 2). The power system solutions to be developed could be used for a wide variety of applications in each target environment; no particular form factor is specified nor are any particular devices to be powered envisaged. Several experimental load/behavior profiles are provided (see Figure 1 in the Test & Evaluation section) to help inform system design. The load profiles are designed to provide measurable comparative data to the program that could map to potential use cases or serve as a basis to compare performer systems against performance targets.

The first load profile in Figure 1 (Load 1) will serve as a focal point for testing and Offerors should consider how their system could continue to drive towards higher power levels for longer periods of time in balance with other technical metrics. While Performer PPS system performance is expected to be measured against each of these load profiles, Offerors are not required to illustrate that their system will serve every load profile. These profiles are provided as potential examples only and may change for the actual T&E events. Additionally, a pathway towards scaling the proposed power systems from the Test Article demonstrations required at the Phase 2 and 3 test events to successively higher orders of magnitude generating capacity (i.e. 100 W, 1 kW, 10 kW, 100 kW) should be plausible and described by Offerors along with changes in scaling laws and other system design assumptions to include the identification and characterization of risks. Offerors may propose optional work to supplement their main proposal work that addresses design issues in scaling to the aforementioned power output levels which may be funded at the discretion of the SOLSTICE PM. Offerors may propose to a single track or to both tracks separately with two separate proposals. Should Offerors who propose to both tracks be selected for an award in both tracks, those Performers shall be required to submit test articles in the numbers specified in Section 1.E “Testing & Evaluation” to support separate testing and evaluation (T&E) for each track.

Specific goals of the two tracks are as follows:

Track 1: Space-based Energy Conversion Systems

1. Primary and secondary objectives detailed above, for systems located in a space environment under AM0 incident sunlight1;

2. A substantially higher lifetime energy harvesting yield (kWh), power density, and degradation resistance over a simulated 5-year mission (stretch target of 10-years) compared to a SOA system;

3. Reasonable expectation to survive autonomous launch/deployment from a reduced-volume (stowed) state;

4. Comparable cost to SOA 1-sun multijunction space PV systems.

Track 2: Terrestrial surface-based Energy Conversion Systems

1. Primary and secondary objectives detailed above, for systems located in a variety of terrestrial locations under AM1.5 incident sunlight2;

2. A substantially higher lifetime energy harvesting yield (kWh), power density (W/m2), and degradation resistance over a simulated 3-year mission (stretch target of 10-years) compared to a SOA system;

3. Reasonable expectation to survive autonomous deployment from a reduced-volume (stowed) state;

4. Comparable cost to notional 1-sun multijunction terrestrial PV systems.

Both Track 1 and Track 2 system solutions must demonstrate performance under simulated environmental conditions, as well as achievement of other metrics specified in Section 1.F Program Metrics.

1 AM0 = Air Mass 0 average spectral irradiance typically experienced in an earth-orbital environment with 1366 W/m2 total incident power 2 AM1.5 = Air Mass 1.5 standard spectral irradiance typical at the earth surface with 1000 W/m2 total incident power

1.D.2 Program Structure

The SOLSTICE program will proceed in three phases as follows:

Phase 1 (18 months) Proof of Concept Development (POC)

The objective of Phase 1 “Proof of Concept Development” (POC) is to demonstrate new materials, devices, and other component technologies or key integrations for power systems that, with further development and integration into a prototype power system, could allow the system to meet the Track 1 or Track 2 performance metrics shown in Section 1.F of this BAA. For Phase 1, demonstration deliverables must be “self-contained”, meaning they must allow IARPA to perform independent testing and evaluation (T&E) to measure performance, under solar-simulated light or other specified conditions, towards the Program Metrics set for Phase 1. Offerors are free to propose any number of innovative component developments that can realistically achieve the program metrics. Several innovative components may also be combined into a single demonstration unit that can be delivered as a Test Article for T&E. An innovative component is generally considered to be one that has not been previously designed or reduced to practice.

In addition to delivering proof of concept solutions for T&E, Performers must deliver preliminary design documents and modeling to demonstrate that the novel components, when integrated into the proposed power system design (intended for development later in the Program), can be expected to meet all Phase 1 metrics. The mathematical models must describe how the new components will contribute to achieving the Program Metrics in Phase 1 as part of the power system planned for Phase 2, detailing key assumptions and extrapolations, and considering effects not replicable with the Test Articles submitted to the T&E partners.

(e.g. thermal management, lower losses due to higher system voltages, scaling effects, etc.)

At the conclusion of Phase 1, Performers must also make a compelling argument, supported by extrapolations from experimental data and modeling, that their power system design (with any substantiated revisions) can reasonably be expected to meet or exceed Phase 3 metrics with further development by the end of the program.

Phase 2 (18 months) Prototype Demonstration

In Phase 2, Performers will improve upon materials, devices, and designs developed in Phase 1 to fabricate a fully integrated prototype power system (PPS). Performers will assemble their PPSs within a standardized set of Power System Testbed (PST) guidelines described in Section 1.E and finalized in the T&E Procedures Manual. The principal Deliverables for Phase 2 will be 1) several hardware PPSs, 2) modeling/simulations of system behavior, and 3) design documents from each Performer for T&E. PPSs will undergo substantial performance characterization under a range of operating conditions anticipated in target environment(s).

Performance will be compared to reference PPSs assembled by the T&E team using best-available components. Experimentally derived performance parameters will be fed into standardized models assembled by the T&E team to calculate time-weighted system energy efficiency (ηsys) and energy harvesting yield (EHY). In addition to the PPS hardware, Performers must deliver updated component-level and system models/simulations that will be compared with T&E modeling/simulation. Performers must also develop a strategy and deliver supporting documentation on how their power system will scale beyond the Phase 2 PPS system size to include larger aperture area. Performers must provide a clear description of how the power system will mature to meet the required metrics for Phase 3 of the program and higher-scaled system sizes. PPSs have no specific voltage, current, or mass requirement, provided the integrated components fit within the volume of the PST form factor and meet the interface requirements as defined by the T&E teams.

Phase 3 (12 months) Scalability and Durability Assessment In Phase 3, Performers will refine and scale their power systems to meet Phase 3 metrics. While Phases 1 and 2 do not specify a target output voltage to facilitate innovation, Phase 3 PPSs are anticipated to meet a specific voltage requirement that will be determined during the earlier phases of the program, to facilitate near-term end use. Performers will continue to leverage the standardized PST form factor used in Phase 2 and update their PPS design with improved components and/or approaches to achieve the end of Phase 3 metrics. These PPSs will be sent to the T&E team for performance and durability evaluation. Durability tests will include testing against potential failure modes and conditions that could be expected in the target environment(s).

1.D.3 Team Expertise

Collaborative efforts and teaming among Offerors are highly encouraged. It is anticipated that teams will be multidisciplinary, leveraging expertise, capabilities, and innovations under development from a range of entities. IARPA anticipates that Offeror teams may include, but are not limited to, expertise in the following technical areas. Expertise in all these disciplines is not a selection criterion.

• Materials science/engineering or chemistry

• Electrical engineering

• Optics/Optical engineering

• Mechanical engineering

• Thermal science/engineering

• Radiation physics

• Condensed matter physics

• Theoretical chemistry/physics and modeling

• Systems engineering

• Engineering co-design/development

• Multi-physics modeling/simulation

• Digital twin development

• Machine-learning (ML)/artificial intelligence (AI) aided design

• Corrosion

1.D.4 Out-of-Scope Research Areas

The following areas of research are out of scope for the SOLSTICE program:

• Component development that cannot be independently tested and evaluated (i.e. by a third party outside the Performer team) to assess contribution toward the program metrics.

• Development of novel chemistries for electrochemical or thermal energy storage

• Development of cell-level improvements (e.g. cathode, anode, separator, electrolyte) for electrochemical storage devices

• Solutions that employ radioactive materials as part of components or would integrate radioactive materials as part of a system-level design.

• Development of components that adjust the orientation of the entire power system at the time of deployment or over time for Track 2 (terrestrial) applications. (e.g. macroscopic tracking devices)

• Approaches that propose, or are likely to result in, only incremental improvements over the current state-of-the-art.

• Approaches with significant limitations on operating conditions, operational parameters, or deployment needs.

• Approaches that are incompatible with remote, unattended operation.

• Approaches that cannot be packaged for safety.

• Development of component technology that is not integral to the operation of the power system required for the Offeror’s approach, unless it supports the greater SOLSTICE program, as approved at the discretion of the SOLSTICE PM.

• Solutions that cannot be made sufficiently robust for deployment and use in the target application environments for each respective track.

• Research that does not have strong theoretical and experimental foundations or plausible scientific support for the Offeror’s claims.

1.D.5 Government-Furnished Capabilities (GFC)

Due to the limited availability of high-efficiency multijunction solar photovoltaic cells (particularly those that are spectrally matched to the terrestrial AM1.5 spectrum), the Government will allow Offerors to propose the use of MOCVD and/or HVPE growth capabilities possessed by the NREL T&E partner to grow solar cell device structures previously published by NREL researchers and grown using NREL facilities/equipment. The samples can be grown on a limited number of small substrates that, when fabricated, could provide 1cm2 area devices for demonstration purposes, or component testing and eventual integration into power systems. Offerors can process the device structures into fabricated solar cells within their own teams, or can utilize standard processing capabilities available at NREL including a quick-turnaround process, literature-defined process sequence, or a specific standard processing sequence. New solar cell designs or previously reported designs not previously prepared at NREL will need to be fabricated within an Offeror’s team and cannot be fabricated using this GFC. Offerors proposing to Track 1 or 2 of the program may propose to use this GFC. Offerors are not required to use this GFC as part of their proposed projects. The costs of the cell growths and/or processing, which depend on device design complexity, must be included as part of the Offeror project budget in their Volume II - Cost Proposal submission, if requested.

1.E. Testing and Evaluation (T&E) All deliverables will be subjected to independent, objective T&E arranged by the Government that will verify progress toward achieving program objectives at defined points during the program. Achievement of program metrics at these defined points may be a condition for continued participation in the SOLSTICE program. T&E protocols will be continually evaluated and updated as necessary throughout the program to fulfill program goals. Performers are expected to develop and conduct their own T&E program for their components and power systems continually throughout the program to measure progress toward achieving program metrics. Proposals shall describe how the Offeror plans to conduct their own T&E in preparation for the independent Government T&E of deliverables described below. Offerors are encouraged to conduct their own internal T&E with as realistic conditions as possible for the target environment (i.e. space or terrestrial surface). The descriptions below are the starting point for T&E protocol development, with more detailed protocols to be presented at program kickoff within Version 1 of the T&E Procedures Manual.

Revisions to the T&E Procedures Manual are expected at each of the subsequent program phase boundaries, but may be made at any time as necessary. Performers will be expected to maintain close communication with the Government T&E teams to plan for and respond to requests to facilitate the T&E effort. At the T&E partners’ sole discretion, Test Article analysis may cease if personnel or equipment are jeopardized by continued testing, which may result in a Performer failing to demonstrate program metrics.

The schedule of deliverables and T&E events can be found in the Program Milestone, Deliverables and Testing Schedule in Table 6 in Section 1.G.3. of this BAA. There will be two rounds of T&E in each of Phases 1 and 2 of SOLSTICE. Phase 3 will have one round of T&E as described in the schedule. Performers may expect up to three months of time after test articles are delivered before independent Government results are available. Performers will be responsible for transportation of deliverables to designated T&E sites in compliance with all applicable laws and regulations. In each T&E round, the performance of the delivered designs, models, and hardware will be tested and assessed against the performance metrics listed in Table 4 (Track 1) and Table 5 (Track 2) in Section 1.F. of this BAA. If there are testing considerations specific to an Offeror’s solution that may be incompatible with the notional testing protocols described herein, these must be described in the Offeror’s proposal along with suggestions for modifications. The Program Manager will release a subset of the T&E data to the Performer teams; some test articles may be returned to Performers, but for planning purposes there should be no expectation of return of the test articles following delivery to the T&E teams.

Details of project deliverables are provided in Section 1.G, but the key evaluation foci across the program will remain on 1) design documentation, 2) modeling (component and power system), and 3) hardware test and demonstrations:

Design documentation

The T&E team will review power system design documentation provided by Performers at the designated timepoints to evaluate the likelihood of the Performer’s design to reach the SOLSTICE performance metrics (see Section 1.F). Design documents should include, at a minimum, detailed drawings and schematics of power systems planned at each phase, clearly showing electrical wiring routing, grounding schema, component identities and locations within devices. Design documentation should include descriptions, tables, and figures that detail the range of designed operating parameters of the components and system as a whole and measures to ensure safe operation.

Modeling

Performer modeling work is expected to mature and increase in model fidelity, precision, and sophistication as the SOLSTICE program progresses, with feedback loops from the experimental data providing validation or spurring model adjustment. (see Table 1) Performers are expected to couple (among other variables) optical, electrical, thermal, and mechanical impacts into their component and system-level models to understand the impacts of their design choices. The T&E partners will be evaluating models generated by Performer teams for reasonableness and provide suggestions when possible, for improvement and better integration with their own modeling work. Software/modeling deliverables must adhere to the submission guidelines provided by the T&E Procedures Manual to allow for evaluation by the T&E Partners and clear statement of the assumptions and calculations used to determine reported performance. The T&E teams will provide information on needs to interface Performer models with their own modeling at program kickoff.

Phase

Components performance models PPS performance models

Scaled systems performance models Scaled system cost model

TABLE 1: Qualitative characterization of model fidelity expectations by the end of each SOLSTICE program phase. (fully-filled circle signifies highest possible level of fidelity)

Hardware demonstrations

Hardware deliverables (components in Phase 1 and power systems in Phases 2 and 3) will be tested as received and must contain suitable electrical and mechanical interface points as described in the T&E Procedures Manual.

Components in Phase 1 must be “self-contained”, meaning they can be connected to standard laboratory monitoring equipment to measure performance without significant de-integration, setup, or assembly by the T&E team. Performers must provide instructions for setup and required testing conditions of components submitted for T&E so that the T&E team can measure the performance attributes intended for submitted components. Performers should provide the T&E team with ranges of expected values for the observable measurements associated with each component.

Power systems must deliver power immediately upon excitation. Performers must provide the maximum power point (Wmp) to the T&E team for each test article provided in the form of a current-voltage sweep plot at 298 K (hereafter referred to as an I-V sweep) clearly showing Wmp, open circuit voltage (VOC), and short circuit current (ISC). Safe operating ranges for current and voltage must be specified to the T&E team. If at any point during test article assessment the T&E team (at their sole discretion) deems further testing of a test article to be unsafe for the test equipment or T&E personnel, the testing of that test article will cease immediately and the data/results for that test article will be interpreted as captured up to that point and no further.

Characterization of power systems (components in Phase 1 or PPSs in Phase 2 and 3) will generally be conducted under solar-simulated light and a range of environmental conditions (outlined below) with output monitored via attachment of the output terminals to an electronic load simulator to test the device under operation. When possible, current-voltage (I-V) sweeps will be taken from components or combinations of components for troubleshooting or providing inputs to modeling. Performers should incorporate access points within their system to enable T&E partners to probe electrical, thermal, or other properties at key points in their system (e.g. interfaces between components). Current, voltage, time, derived electrical parameters (using current, voltage, and/or time), and temperature will be recorded for each power system tested. Temperature will be measured by sensors attached to the test articles in positions chosen by the T&E team at their sole discretion (which could be influenced by performer recommendations with appropriate rationale). Test Articles submitted for Phase 1 testing will be assessed at room temperature and pressure under AM0 (Track 1) or AM1.5 (Track 2) solar simulated irradiance, as appropriate. By Phase 2 T&E events, Performers will be expected to have developed and integrated a system to appropriately manage thermal loads on PPSs to maintain consistent operation in the test environment. Performers must be prepared to discuss their safety plan for 1) material encapsulation, and 2) thermal management with the T&E team by the beginning of Phase 2 to assess risks associated with planned testing during the Phase 2 and 3 T&E events. At the T&E team’s sole discretion, experimentation with any given test article will cease if safe, controllable operation cannot be maintained.

No specific load requirements are defined in this program to allow Offerors greater freedom to innovate in their power systems. However, several load profiles (see Figure 1) are expected to be used as part of the T&E effort to better understand the performance strengths and weaknesses of each system. Offerors may reference these profiles in their proposals or suggest a different load profile that showcases the benefits of their approach. The first load profile in Figure 1 will serve as a focal point for testing and Offerors should consider how their system could continue to drive towards higher power levels for longer periods of time.

The following provides additional detail on anticipated T&E plans by SOLSTICE program phase:

For Phase 1 (Proof of Concept), each Performer shall deliver at least one (1) POC test article at the first T&E event and at least three (3) POC test articles at the second T&E event, consisting of the innovative components integrated as necessary with COTS components to demonstrate measurable performance sufficient to model and extrapolate to the system-level metrics outlined in Table 4 (space applications) or Table 5 (terrestrial applications) in Section 1.F. Offerors shall specify the form factor of their test articles for this Phase and the calculations they recommend to extrapolate performance to a power system output level. Offerors must provide test articles in the number required at each T&E event for each novel component technology they plan to implement as part of their system design. For example, if two novel components are being proposed, then a total of two test articles will be delivered at the first Phase 1 T&E event and a total of six test articles (three of each component) will be delivered at the second Phase 1 T&E event. Alternatively, if appropriate, Offerors may choose to integrate several innovative components into a single demonstration test article to provide in the number required at each T&E event. Unless an energy storage medium is essential to the innovation(s) being demonstrated, proof of concept test articles are not expected to have an integrated battery or charge controller.

For Phase 2 (Prototype Demonstration), each Performer shall deliver one (1) Prototype Power System (PPS) test article for the first T&E event and three (3) PPS test articles for the second T&E event. Each PPS will integrate novel component(s) and system-level approaches consistent with the proposed system utilizing the standardized Power System Testbed (PST) form-factor that meets the requirements specified by the T&E team. Specifics of the PST electrical and mechanical interface will be finalized by the SOLSTICE kickoff meeting, but the general PST form factor includes the following requirements: 1) ~10 cm x ~20 cm x ~10 cm body dimensions (i.e. similar to a 2U cubesat) with supporting frame at the interfaces of the body faces and open internal volume for integrating components, 2) rechargeable energy storage medium, 3) standard attachment points for hardware and electrical integration with T&E partner equipment. Aperture area (for energy collection or rejection) must be restricted to the body of the PPS at this Phase and not deploy beyond the volume of the PPS. Performer PPSs integrated into the standard PST architecture will be shipped to the T&E partners for evaluation at two timepoints during Phase 2 and must be transportable by common shipping carriers.

FIGURE 1: Seven Load Profiles to Characterize PPS Functionality & Performance

For Phase 3 (Scalability and Durability Assessment), each Performer shall deliver two (2) PPS test articles integrated into the PST design specifications set forth in the T&E Procedures manual for Phases 2 and 3.

Since Phase 3 PPSs could deploy beyond the body of the PST, Offerors must specify in their proposal the intended size of their prototype at this phase and how they plan to conduct internal testing. Any deployment beyond the body of the PPS must be contained within a volume of 4U attached outside the 2U of the PST body in any contiguous or non-contiguous arrangement (i.e. maximum total of 6U volume for body plus deployed volume; 20 cm x 10 cm x 10 cm body plus 4 units of 10 cm x 10 cm x 10 cm attached in any contiguous or non-contiguous arrangement outside the body). See Figure 2 for examples of two possible structures. PPSs will be shipped to the T&E partners for evaluation during Phase 3 and must be transportable by common shipping carriers. The Phase 3 volumetric limits intend to prove out systems that are of manageable and sufficient size to advance program objectives with particular consideration for ensuring ability to test and availability of evaluation equipment (i.e. TVAC) and are not intended to limit innovation. At the sole discretion of the SOLSTICE PM, performer requests for deployments that exceed the Phase 3 volume limits identified above may be entertained in order for performers to demonstrate innovative concepts necessitating deviation, but that are still aligned with the objectives of SOLSTICE.

A summary of exemplar Test Article delivery configurations by program phase and the associated tests can be found in Figure 3.

The tests listed in Sections 1.E.1 and 1.E.2 are expected to be used to determine Performer Test Article performance relative to the metrics listed in Table 4 (Track 1) or Table 5 (Track 2) in Section 1.F, but the T&E team may perform additional testing on components or systems to ascertain performance variation, potentially including, quantum efficiency (QE), photoluminescence, electroluminescence, infrared thermography, and other tests not listed below. Since Phase 1 physical deliverables consist of test articles with POC plus COTS components that may not fully represent the system-level performance expected, for the purposes of Phase 1 power system modeling, Performers must supply models that include equations and assumptions into which measured data from the component test articles shall be input to demonstrate that the system metrics for Phase 1 will be met. Assumptions and modeling methodology must be explained and will be assessed by the T&E team at specific points throughout the program to assess reasonableness.

FIGURE 2: Schematic of two of the possible Phase 3 PSS configurations. Dark blue indicates PPS body, light blue areas indicate available areas for deployable structures in Phase 3. Vertical dashed line indicates central axis of PPS.

FIGURE 3: Summary SOLSTICE Test Article descriptions and tests by phase. Design is a potential exemplar and meant for illustrative purposes only.

The tests and procedures outlined in the following sections are preliminary to allow Offerors to understand the anticipated scope of the testing; tests and procedures are subject to change.

1.E.1 TRACK 1 TESTING (Space Applications)

Government T&E of PPSs will be assessed through a combination of room temperature and simulated space environment (i.e. thermal-vacuum (TVAC) chamber) testing before and after stress testing as shown in Table 2.

TABLE 2: Track 1 (Space) Test & Evaluation Schedule and Anticipated Procedures

POC Test Articles Prototype Power Systems Phase 1 Phase 2 Phase 3 T&E Event #: 1 2 3 4 5 Performer POP Month Due: 7 14 24 31 43 Minimum Test Articles Delivered: 1 3 1 3 2 # TRACK 1 Testing Procedure 1 Thermal cycling N/A 10 cycles N/A 100 cycles 100 cycles 2 UV irradiation N/A 10 d N/A 30 d 30 d 3 Vacuum I-V Sweep & outgassing of volatile materials N/A N/A Test Test Test

4 Electron and proton irradiation N/A N/A N/A Test Test 5 Simulated damage events N/A N/A N/A Test Test 6 Mechanical stress N/A N/A N/A N/A Test*

* Performed after all other testing is completed to help inform the next stage of development

Notes on TRACK 1 Testing Procedures:

(1) Thermal cycling will be performed to emulate the temperature extremes expected for power systems in an earth orbit environment. Temperatures from 173 K to 373 K are anticipated to be used, but will be finalized in the T&E Procedures Manual. A light I-V sweep will be taken at intermediate time intervals (between the exposure start and the timepoint listed in the table) and compared to the initial measurement. Thermal cycling will cease if any of the intermediate timepoints reveals a change in the Pmp by more than 50% relative to initial measurement.

(2) Accelerated UV aging of samples will be carried out using UV wavelengths characteristic of the AM0 solar spectrum for the equivalent period of time specified in the table. A light I-V sweep will be taken at intermediate time intervals (between the exposure start and the timepoint listed in the table) and compared to the initial measurement. UV irradiation testing will cease if any of the intermediate timepoints reveals a change in the Pmp by more than 50% relative to initial measurement. Phase 1 test articles may contain protective measures for components not intended to be irradiated which will not count against the weight metric.

(3) Samples will be exposed to a thermal-vacuum chamber (~77 K and ~10-6 torr) over a range of temperatures to ascertain the degree of volatile condensable materials (VCMs) that are released.

(4) keV electron/proton irradiation testing with fluence levels consistent with a multi-year mission in LEO or GEO using protocols informed from AIAA S-111 (Qualification and Quality Requirements for Space Solar Cells)

(5) Aperture areas will be subjected to a combination of non-destructive and potentially damaging tests (performed last on test articles) designed to simulate single-event threats in a space environment, including debris/micrometeoroid impact damage, high flux irradiation at multiple angles of incidence, “hot spots,” and other potential physical threats. Sizes on the order of several square millimeters to centimeters for the simulated debris or high flux irradiation spot size should be assumed. Power density measurements will be conducted before and after the simulated threat tests.

(6) Preliminary assessment of mechanical stress risks associated with launch and deployment, particularly vibration.