Hybrid HVAC with Thermal Energy Storage Research and Demonstration

Lead Performer: Lawrence Berkeley National Laboratory – Berkeley, CA
Partners:
-- UC Davis - Davis, CA
-- UC Berkeley - Berkeley, CA
-- Emanant Systems LLC - Colrain, MA
DOE Total Funding: $3,050,000
FY21 DOE Funding: $900,000
Cost Share: $90,000
Project Term: October 1, 2018 – March 31, 2022
Funding Type: Lab Award

Project Objective

This project will demonstrate the potential of advanced hybrid HVAC systems that utilize packages of high-efficiency air-to-water heat pumps (AW-HP), phase-change-material (PCM) based thermal energy storage (TES), and climate appropriate indirect evaporative cooling (IEC) to shift and reduce peak heating and cooling loads. With increased variability in energy supply due to the growth of renewable resources and increased electricity demand as we electrify end-use technologies, the electrical grid will require additional flexibility, demand response, and other services. Hybrid HVAC systems have potential to address these concerns through use of load shifting with energy storage, taking advantage of time of use electricity tariffs to deliver significant energy cost savings to building occupants and owners.

Key objectives of this project:

• Undertake a comprehensive laboratory characterization of key components (PCM-TES, AW-HP, IEC), to generate performance maps and publicly available models of these technologies.
• Develop rapid prototyping simulation tools that enable evaluation of these hybrid HVAC systems in three different building applications (small-medium office, big box retail, and multifamily residential), in a range of climates and tariff environments. Performance metrics assessed include greenhouse gas emission mitigation, peak load reduction, and energy cost savings.
• Advance and assess control strategies, including model predictive control, that will optimize operation of these complex integrated systems. Controls will be developed using the rapid prototyping simulation tools and applied to a physical prototype under real world conditions. 
• Engineer, build, and test a prototype hybrid HVAC system, intended for a technology demonstration on a small to medium commercial building. This prototype system will be “shovel ready” for immediate deployment, contingent on follow-up deployment funding. 

Component and system performance data, in combination with experimentally validated models, will support the development of compliance pathways for these new advanced HVAC systems to meet future efficiency standards. This data can also be used by utility programs to incentivize demand reduction and response technologies.

Project Impact

The impact of this project is that virtual and physical demonstrations of hybrid HVAC systems with integrated PCM-TES can be leveraged for related projects that optimize demand flexibility strategies for deployment. The Modelica based component models developed as part of this work will be included in the publicly available Modelica Buildings Library, developed by LBNL. One of the key advantages of performing this work in Modelica is that the next generation of EnergyPlus uses this Modelica Buildings Library to model HVAC systems, simplifying any future integration of these models into EnergyPlus. The target performance of this system iteration is a 20% peak load reduction and 30% annual HVAC energy cost savings, compared to state-of-the-art all-electric systems. Simulation results indicate that closer to 50% peak load reduction is possible depending on climate and building type, with cost savings highly dependent on local tariffs.

Combining thermal storage with efficient heat pumps enables electrification where power limitations in electrical capacity would otherwise limit it. This combination of previously proven component technologies, applied as a packaged system with optimized controls, will increase grid reliability and flexibility by shifting peak loads to align renewable energy supply with electrified end-use demand.

Contacts

DOE Technology Manager: Charles Llenza
Lead Performer: Brett Singer, Lawrence Berkeley National Laboratory

Related Publications

Helmns, D., Blum, D.H., Dutton, S.M., and Carey, V.P., Development and Validation of a Latent Thermal Storage Model Using Modelica, Energies, 14(1), 2021, (doi:10.3390/en14010194).

Helmns, D., Blum, D., Casillas, A., Prakash, A., Woolley, J., Vernon, D., Mande, C., Woodcox, M., and Dutton, S., Towards a Techno-Economic Analysis of PCM-Integrated Hybrid HVAC Systems, paper HPB2021-3416, Proceedings of the Purdue 2021 High Performance Buildings Conference, HPB2021, May 24-28, 2021, Virtual.