Integrating Latent Heat Storage into Residential Heating Systems

This project experimentally and numerically investigated the performance of thermal energy storage (TES) tank with phase change material (PCM). The experimental analysis has been conducted on a test rig that is designed and built within this project at the Energy Technology Department at KTH. The test rig’s experimental capacity covers wide range of heating and cooling/refrigeration applications; it can run in the temperature range of - 10 to 90°C with a heating capacity of about 20kW and cooling capacity of about 10 kW. The test rig is fully equipped with highly accurate measurements that facilitate detailed analysis of the PCM-TES tank performance.

Funded by:

The studies have been financed by Swedish Energy Agency and the KTH-CSC Programme, which is based on the agreement between KTH and the China Scholarship Council (CSC)

Time period: 2015-2021

Project partners:

Svensk Energi & Kylanalys (EKA)

Danfoss Värmepumpar AB

Vesam AB

Background

Buildings are responsible for about 40% of total energy use in Sweden and Europe. The increasing rate of constructing new buildings and the rate of refurbishment of the large old building stock offer valuable opportunity to introduce highly efficient energy systems.

Thermal energy storage (TES) as one of key technology options for energy-efficient heating and cooling in buildings. Phase Change Material based Thermal Energy Storage (PCM-TES) could replace sensible heat storage solutions. Such an innovative concept utilizes the phase change of a substance to store and release energy at a narrow range of temperature change, resulting in 5-15 times larger storage density than with the commonly used sensible heat storage. This makes it possible to design a compact system that fits in the limited space available in buildings but with much greater storage capacity, thereby allowing for an increased use of renewable energy and waste heat.

Project content

The general aim of this project is to experimentally and theoretically investigate the integration of PCM into the built environment for space heating and domestic hot water production.

The comprehensive study in this project demonstrated a multi-level investigation on the techno-economic feasibility of using three off-the-shelf, macro-encapsulated technologies for residential heat load shifting, focusing on the application of storage integration with heat pump (HP)-based heating systems. The investigations are conducted on three levels (material, component, and system), mainly consisting of the following four aspects:

1) Selection of PCMs and measurements of their thermo-physical properties.

2) Development and characterization of three full-scale LHTES components.

3) Development and validation of numerical heat transfer models for predicting and optimizing the storage thermal performance.

4) Techno, economic, and environmental evaluation of load shifting operations with LHTES-HP integrated systems.

Publications

Journal papers:

Xu, T., Chiu, J. N.-W., Palm, B., & Sawalha, S. (2019). Experimental investigation on cylindrically macro-encapsulated latent heat storage for space heating applications. Energy Conversion and Management, 182, 166-177.
Xu, T., Gunasekara, S. N., Chiu, J. N.-W., Palm, B., & Sawalha, S. (2020). Thermal behavior of a sodium acetate trihydrate-based PCM: T-history and full-scale tests. Applied Energy, 261, 114432.
Xu, T., Humire, E. N., Chiu, J. N.-W., & Sawalha, S. (2020). Numerical thermal performance investigation of a latent heat storage prototype toward effective use in residential heating systems. Applied Energy, 278, 115631.
Xu, T., Humire, E. N., Chiu, J. N.-W., & Sawalha, S. Latent heat storage integration into heat pump-based heating systems for energy-efficient load shifting. Energy Conversion and Management, 236, 114042.
Xu, T., Humire, E. N., Trevisan, S., Ignatowicz, M., Sawalha, S., Chiu, J. N.-W. Experimental and numerical investigation of a latent heat thermal energy storage unit with ellipsoidal macroencapsulation. Energy, Available online 21 August 2021, 121828.

Conference papers:

VIII. Xu, T., Sawalha, S., Mazzotti, W., & Palm, B. (2016). Performance Evaluation of a Large Capacity Air-Water Heat Pump Using Propane as Refrigerant. In Proceedings of 12th IIR-Gustav Lorentzen Conference on Natural Refrigerants Edinburgh UK - GL2016, 21-24 August 2016.
IX. Xu, T., Navarro-Peris, E., Piscopiello, S., Sawalha, S., Corberán, J. M., & Palm, B. (2018). Large-Capacity Propane Heat Pumps for DHW Production in Residential Buildings. In Proceedings of 13^th IIR Gustav Lorentzen Conference on Natural Refrigerants: Valencia, Spain, 18-20 June 2018
X. Xu, T., Hao, Y., & Sawalha, S. (2019). Comparing integrating configurations of latent heat storage in heat pump heating systems. In Proceedings of the 25th IIR International Congress of Refrigeration: Montréal, Canada, August 24-30, 2019.
XI. Xu, T., Chiu, J., & Sawalha, S. (2019). Numerical Study of a Latent Heat Storage Unit with Cylindrically Encapsulated PCMs. In SUPHER’19 Conference, Sanova, Italy, 4-6 September 2019.