Solutions are sought for designs of thermal energy networks (TENs) that provide a template for time-phased construction of a full-scale system. The design approach should consider the full-scale (approx. 15+ buildings) system architecture and major components while developing preliminary engineering designs for a fully functional small-scale (approx. 2-5 buildings) system. Based on the outcome of the designs, DoD may fund the construction of the small-scale system(s) as a follow-on demonstration project(s). Proposals should include scope and costs for the system design only. 

 Feasibility studies at three military installations, funded through a previous ESTCP solicitation, will be completed in 2025. These sites and the studies’ results are required to be used as the basis for the thermal energy network designs to be funded through this solicitation (see the Background section for more information about the feasibility studies). DoD will provide building information, hourly load data and any computer simulation models developed as part of the feasibility studies to the project teams to facilitate building selection and preliminary design work. 

TEN designs should include consideration of the following: 

• Preliminary cost estimates should be appropriately summarized at the major system level in order to help DoD most effectively utilize different financing structures available, and should include the cost of expected building-level retrofits for compatibility with ambient thermal loop integration.
• Impacts of building-level retrofits or new building construction on thermal loads.
• Network architecture options, to include a single, non-insulated pipe buried in the ground that operates near ambient temperature, serving building space heating, cooling, and domestic hot water loads. These systems are sometimes called Reservoir Networks (https://doi.org/10.1016/j.energy.2020.117418). Other ambient loop configurations may be considered.
• Options to utilize waste heat, such as from a data center, wastewater or other thermal sources that may be identified.
• Cost effective development of appropriate heat sources and sinks, which may include geothermal exchange (borehole array, groundwater, aquifer) or other heat sources and sinks capable of maintaining ambient loop temperatures.
• Description of control sequences of the TEN district loop, the borefield(s), and any central plant(s), and the energy transfer stations.
• System should be designed to allow grid-responsive operations to optimize off-peak versus on-peak energy usage.
• Cost and performance impacts of incremental expansion of the TEN over time.
• Requirements for backup power for the TEN and/or building-sited thermal systems to serve critical loads/buildings in the event of an electrical utility power outage.
• Cyber secure control system, sensors and meters for optimizing system performance and enabling third-party ownership and operations. 

The output at completion of this phase shall be a schematic design (10-15%) of the overall design effort for the small-scale system, depicting a clearly defined feasible system design, a defined concept for expansion to the full-scale system, an exploration of the most promising design alternatives, and a reasonable basis for the cost estimate. 

Proposal Instructions: The proposal instructions provided with this solicitation are written for typical demonstration projects that include the installation and testing of physical systems or components. For proposals submitted under this topic, please interpret the instructions with the following guidance. Items not listed below should be interpreted as read in the Proposal Instructions document and with the general guidance that the term “technology” applies to the design approach used for the thermal energy network designs.   

Section 2.1 Abstract: 

• Item 6, Technology Description: Describe the approach and tools used to develop the system design that meets the technical objectives described in the solicitation topic. Include examples of related work and how it applies to the DoD use-case. 

Section 2.2 Technical Section 

• Item 6-c, Technology Maturity: Provide examples (no more than 2) of experience designing and developing thermal energy networks with description of the design approach and system architecture. 

Item 6-d, Technical Approach:  Describe the process, data, and tools to be used to develop the thermal energy network design and how considerations of the full-scale system are incorporated into the process. Include a description of cost factors and how different ownership models may impact system design or buildout plans. Explain how considerations of system resilience will inform the TEN design and/or building-specific retrofits. Include a discussion of relevant site and/or general location characteristics that would influence choice of one site over another. 

• Item 9, Technology Stage: Not Applicable
• Item 10, Technology Transfer Plan: This section should include a discussion of the challenges of designing, implementing, and operating thermal energy networks on military installations and an explanation of how this project will help address these challenges.  Refer to the numbered items in this section for examples of specific activities that may be applicable to this project.
• Item 11, Disposition of Equipment: Not Applicable 

 For purposes of estimating costs, in addition to the Final Report, project deliverables may include the following design documentation, as appropriate: drawings and renderings of site diagrams, plans, layouts and preliminary building retrofit layouts; narrative, analysis and calculations including all assumptions, applicable codes and criteria, and comprehensive discussions on significant engineering aspects and design decisions; and a cost estimate of sufficient detail to provide understanding of major cost drivers of key system and sub-system components, the impacts of design decisions and trade-offs, and an assessment of overall cost risk and uncertainty. 

Successful project outcomes will provide an actionable preliminary design with accompanying costs and supporting analysis to inform a decision to move into detailed design for one or more TEN demonstration projects. While TENs are based upon proven existing technology and components, the combination of these technologies into a connected system with common shared thermal resources has not been implemented at a military installation and requires demonstration at a meaningful scale to evaluate system cost and performance and ensure the ability to meet DoD energy resilience requirements.

ESTCP’s Installation Energy and Water (EW) program area supports the demonstration and deployment of innovative technologies that enhance energy security, improve water efficiency, and strengthen mission resilience across DoD installations. This program prioritizes cost-effective, scalable, and cyber-secure solutions that reduce operational costs while ensuring the reliability of energy and water systems critical to national defense. 

Modern thermal energy networks (TENs), which leverage advances in several technologies to improve system-level efficiencies and reduce system life-cycle costs, may offer a unique opportunity for DoD to make cost-effective improvements to its building stock and leverage public-private partnerships to align stakeholder expertise and access financial incentives to provide reliable and affordable thermal energy service. 

Through the FY23 solicitation, ESTCP funded two project teams to conduct feasibility studies of TEN systems. The studies were conducted for Joint Base Andrews located in Maryland and for U.S. Army Garrison Ansbach and U.S. Army Garrison Wiesbaden in Germany.  

Joint Base Andrews: The feasibility study included 17 buildings co-located on a portion of the installation where future plans include building renovations and new construction. Building energy models (using eQuest, https://www.doe2.com/equest/) were developed and calibrated using electric meter data and gas usage for these buildings. Building-specific energy conservation measures (ECMs) were identified and applied to the energy models to generate a scenario for the design of the TEN that includes building retrofit measures. Design option optimization (using Sympheny, https://www.sympheny.com) was conducted to compare alternatives based on costs and energy demand/consumption. A physics-based model was then developed (using Modelica, https://simulationresearch.lbl.gov/modelica/) to evaluate the system performance. 

USAG Ansbach: The feasibility study focuses on four existing “commercial” buildings at the site (a post exchange, lodge, commissary, and medical/dental clinic), as well as one planned building likely to be built within the next several years (a school). Existing buildings are served by building-level HVAC systems, with gas-fired heating, and heating hot water supply temperatures in the range of 160-180°F. Building energy models were developed using OpenStudio and EnergyPlus, and, in the case of existing buildings, calibrated to meter data. A physics-based model in Modelica was developed using NREL’s URBANopt™ platform to evaluate the performance of a thermal microgrid incorporating ground heat exchangers. Options for waste heat recovery from commissary refrigeration were evaluated. 

USAG Wiesbaden: The feasibility study focuses on three existing buildings slated for heavy renovation, which is an opportunity to retrofit them with thermal network-compatible HVAC systems. Since the buildings are currently unoccupied, energy use data representative of likely future conditions was not available. Building energy models were developed using OpenStudio and EnergyPlus. A physics-based model in Modelica was developed using NREL’s URBANopt™ platform to evaluate the performance of a thermal network incorporating ground heat exchangers. A thermal response test, which would provide detailed information on soil conditions at the site to evaluate ground heat exchanger performance, is planned. The site has an existing high-temperature district heating hot water system supplied by oil-fired boilers. Opportunities for integration of an ambient loop with the existing high-temperature system could be considered.  

Keith Welch 

Program Manager for Installation Energy and Water  

Environmental Security Technology Certification Program (ESTCP)  

Phone: 202-657-8954 

E-Mail: keith.a.welch3.civ@mail.mil