RENBuild hybrid system

From left: Combined heat and hot water PCM storage, PCM cold storage, a view into the partly filled PCM cold storage and a macro-encapsulated PCM element.

Hybrid system supplies buildings with heat, cold, electricity and fresh air

The Center for Applied Energy Research’s RENBuild project has moved out of the lab and into buildings for practical testing.

The project, launched in 2020 with funding from the German Federal Ministry of Economics and Climate Protection, is developing an “integrated and compact system to ensure high efficiency and living comfort in buildings.”

The key features of the system are:

• Hybrid solar collectors (PVT) that can provide electrical energy, heat or cold
• High-performance PCM heat and cold storage units
• A flexible heat pump system
• An intelligent building automation system that regulates energy flow

At the beginning of the project, components of the system were tested at CAE labs in Wurzburg, Germany. A realistic prototype of the RENBuild system was then built and tested at the center before the system was installed in a residential building in nearby Estenfeld. The system will also be installed in an office building in November. Both buildings will undergo extensive monitoring of their energy use and comfort levels through the end of next year.

“The comfort level is monitored by sensors for indoor air temperature and relative humidity,” said project manager Felix Klinker. “We also get feedback from the users, but at the moment there are no plans for more detailed user surveys. We measure the heat/cold and electricity demand of the whole system as well as the PV (and battery) data.”

The hybrid solar collectors supply a reversible brine-to-water heat pump with environmental heat or cold and renewable electricity. CAE says a major advantage of the collectors compared to air heat exchangers is their silent operation and the possibility of using existing roof or facade surfaces. These features make the system suitable for densely built urban areas and for retrofitting.

Axiotherm GmbH’s hybrid heat storage units optimize the use of regenerative energy and help bridge the difference between energy supply and demand. In addition to water, the system contains PCM elements to utilize the phase change between solid and liquid for energy storage at temperatures optimized for use in the different storage areas: 52 °C for hot water, 32 °C for heat and 13 °C for cold storage. CAE says the storage capacity is about 2.5 times higher than a comparable water storage system.

The heat and cold storages can be charged either passively via the solar collectors or with the support of the heat pump.

“Synergies can always be exploited if the heat and cold generated during heat pump operation can be used or stored at the same time, e.g. if the heat pump produces hot water while simultaneously charging the cold storage tank as source,” according to a CAE project summary. “The tailored building automation system operates the heat pump primarily during times of high PV electricity generation by intelligent use of the PCM storage units as well as by including the weather forecast.

“The result is a high utilization of the self-generated PV electricity and thus a significantly lower power consumption from the grid compared to conventional systems.”

Croda PCMs used in research on adaptive envelopes

Mar Alonso Martínez, an engineering professor at the University of Oviedo, Spain, is leading a three-year research project whose aim is to develop a new methodology to incorporate phase change materials into adaptive envelopes.

Mar ALONSO“Our initial studies reveal that total mass, air inside the capsule and temperature variation rate influence the thermal response of macroencapsulated PCMs,” she said in an e-mail interview. “Tests evidence that phase change properties must be obtained analysing the whole macrocapsule instead of PCMs alone. Tests and numerical models were combined to assess the incorporation of macroencapsulated PCMs in adaptive envelopes, where the PCM will be chosen depending on the climate.”

The team is conducting several studies using CrodaTherm PCMs, among others.

“One of them is analyzing the macroencapsulated PCM performance,” Alonso Martinez said. “We manufactured a customised macrocapsule to introduce Croda PCMs. We are testing the macrocapsules for different thicknesses, different temperature variation rates, and so on. Those experiments provide us valuable information to numerically model these advanced materials and then, design and study several type of envelopes. We’re also looking for a correlation between traditional test (DSC, THM) and the experimental performance of the macrocapsule.

“Another study we’re doing is the incorporation of Croda PCM to lightweight concretes (LWC) to improve their thermal properties. LWC have good thermal properties because of their porosity. The use of PCMs inside that materials makes them active materials changing their response with temperature. There are some researchers who are incorporating PCMs in concrete mixes (during the mix or after curing process) but, there are no studies about the incorporation of PCMs in LWCs.”

The project reference tag is PID2021-128056OA-I00. More information on the research team is available at linkedin.com/company/giconsime-uniovi/.


• Thermal energy storage startup MGA Thermal says it is “committed to moving forward” after an overheating incident at its 5MWh demonstration plant in New South Wales, Australia. Firefighters were called to the plant Oct. 6 after temperatures in the pilot unit rocketed from their normal 700°C to 1200°C. Fire and Rescue New South Wales said temperatures were stabilized within about 12 hours. “Our primary focus has been to ensure that the demonstration unit and everyone in the vicinity remains safe,” the company said. “No one was injured and no further property damage occurred.”

Sunamp Ltd. has received a £6 million convertible loan note investment from the Scottish National Investment Bank. The company says it will use the funds to increase UK sales, scale up production and accelerate its international expansion.

• The Tyndall National Institute of Ireland welcomed Luisa Cabeza as a distinguished visiting fellow over the summer. As part of her visit, the University of Lleida professor investigated how the use of thermal storage in buildings and industry can reduce the carbon footprint of these sectors.

Embrace infant warmerEmbrace Global is racing to get its PCM-equipped infant incubators into Gaza. The PCM-equipped incubators don’t require a stable supply of electricity. The San Francisco nonprofit is looking to partner with humanitarian relief organizations that can get into the war-wracked region quickly.

Brenmiller Energy‘s thermal energy storage technology has been named one of TIME’s Best Inventions of 2023. The Israeli company’s bGen Zero charges by capturing low-cost electricity from renewables or the grid and stores it in crushed rocks. It then discharges steam, hot water or hot air on demand.

Advanced Cooling Technologies Inc. of Lancaster, Pennsylvania, has been awarded $5.5 million in new contracts from the U.S. Department of Energy. The contracts include projects involving pulsating heat pipes and very high-temperature thermal storage.

B Medical Systems of Luxembourg is the newest member of the RAL Quality Association PCM. The 35-year-old company manufactures and distributes medical refrigeration devices.


• The National Renewable Energy Laboratory, Golden, Colorado, has an opening for a postdoctoral researcher – electron microscopy of thermal energy storage systems.

• The Oak Ridge National Laboratory in Oak Ridge, Tennessee, has an opening for a postdoctoral research associate – thermal degradation.

• The Italian National Research Council‘s Institute for Advanced Energy Technologies (ITAE) is seeking to fill two research fellow positions related to the conversion, use and accumulation of thermal energy. The application deadline is Nov. 24.

Sunamp Ltd., Edinburgh, Scotland, is seeking to hire a senior new product introduction engineer. The engineer will lead the production implementation of new products and extensions to existing product ranges.


Heat storage material

U.S. patent application 20230313013 (applicant Honda Motor Co. Ltd., Tokyo, Japan):

Honda patent drawing“An object of the present invention is to inhibit the phase separation of a salt hydrate used as a main component of a heat storage material. The inventors have made the present invention based on findings that when added to a heat storage material including a salt hydrate and a supercooling inhibitor, graphene oxide can inhibit the phase separation of the salt hydrate. The present invention is directed to a heat storage material including: a salt hydrate as a main component; a supercooling inhibitor that promotes solidification of the salt hydrate; and graphene oxide. The technical features help to inhibit the phase separation of salt hydrates.”

Phase change flame-retardant fiber material for thermal management of lithium-ion battery

U.S. patent application 20230340702 (applicant Nanjing Tech University, Nanjing, China):

“The present disclosure discloses a phase-change flame-retardant fiber material for thermal management of a lithium ion battery in a closed space and a preparation method. The phase-change flame-retardant fiber material is prepared in a coaxial electrostatic spinning manner and includes a composite phase-change fiber material PASA-TPU at a core part and a flame-retardant fiber material TB-PAN wrapping a surface of the core part. The composite phase-change fiber material is well wrapped with the flame-retardant fiber material, and the lithium ion battery wrapping the whole phase-change flame-retardant fiber material in the closed space is subjected to charge-discharge cycle; the result shows that the surface temperature of the battery can be effectively reduced by about 20° C. by the material.”

Heat storage heat pump heater

Mahle patent drawingU.S. patent application 20230302875 (applicant MAHLE International GmbH, Stuttgart, Germany):

“A heat storage heat pump heater (HSHPH) incorporated into a heating, ventilation, and air conditioning (HVAC) system that provides heat to maintain the temperature in a compartment (e.g., a cabin of an electric vehicle) during both a heating cycle and defrosting cycle. This HSHPH contains a heat exchanger having an inlet and an outlet located in one or more manifolds and a core that includes one or more refrigerant tubes through which a refrigerant flows and a plurality of fins that extend between the tubes, the one or more refrigerant tubes being in fluid communication with the inlet and the outlet; and a phase change material (PCM) configured to store heat transferred from the refrigerant during a heating cycle and to transfer heat to the refrigerant during a defrosting cycle. The PCM changes phase at a temperature that is greater than or equal to 24° C.”

More U.S. patent applications:

Thermal management system (BAE System plc., London) | Aircraft electrical machine with improved heat transfer by means of a phase change material (Safran Helicopter Engines, Bordes, France) | A biodegradable heat-absorbing composition (Solublue Ltd., London) | Article of apparel (Under Armour Inc., Baltimore, Maryland) | Phase change material for thermal therapy and delivery of active ingredients (Alps South LLC, St. Petersburg, Florida | Mini freezer-equipped drone for transporting biological materials (Ganapathi Pamula, Cary, N.C.) | Thermal energy storage device (Lehigh University, Bethlehem, Pennsylvania) | Shipping system for temperature-sensitive materials (Cold Chain Technologies LLC, Franklin, Massachusetts)


From Journal of Energy Storage:

Cellulose foams as scalable templates for phase change materials
Optimization of DSC measurements for organic phase change materials

From Construction and Building Materials:

Thermal, structural, and chemical characteristics evaluation of wood/phase change material composites for applying as a finishing material in floor radiant heating systems
Effectiveness of the different eutectic phase-change materials in cooling asphalt pavement

From Future Energy:

Study on Fast Charging Using Phase Change Materials for Electric Vehicle Applications

From Heat Transfer Research:

Melting Process Simulation of Phase Change Material Layer Used in The Building Envelope

From 3D Printing for Lighting:

Phase change materials for thermal management of lighting systems

From European Materials Research Society:

Thermal information processing using phase change materials

From Physica Scripta:

A state-of-the-art review on advancements in phase change material encapsulation techniques for electronics cooling

From Journal of Thermal Analysis and Calorimetry:

Recent innovations and developments concerning the beeswax as phase change material for thermal energy storage: a review
A passive solar application using thermal energy storage in phase change materials for frost damage protection of citrus trees

From AIP Conference Proceedings:

Microencapsulation of phase change materials in a building roof

From Renewable and Sustainable Energy Reviews:

Efficient energy generation and thermal storage in a photovoltaic thermal system partially covered by solar cells and integrated with organic phase change materials
Decarbonising building heating and cooling: Designing a novel, inter-seasonal latent heat storage system

From International Conference Modern Building Materials, Structures and Techniques:

Development of Thermal Storage Building Exterior Using Phase Change Materials

From Biosensors:

Assessing Phase Change Materials as Effective Long-Term Biosensors in Limb Prosthetics

From Energy Reports:

Experimental investigation of the solar latent heat thermal energy storage system integrated with salt hydrate phase-change materials

From European Polymer Journal:

Highly thermal conductive Boron Nitride/Polyrotaxane encapsulated PEG-based phase change materials

From 3rd International Conference on Electrical, Computer, Communications and Mechatronics Engineering:

Analysis of Solidification and Melting of a Phase Change Material: Experimental and Simulation Study

From Thermal Science and Engineering Progress:

Phase change material-enhanced shoe sole for foot thermal regulation to prevent hyperthermia
Developing Wallpaper/Dodecyl alcohol composite phase change materials as new kind of wall covering elements for building interior thermoregulation
Dynamic modeling and experimental validation of household refrigerators/freezers equipped with phase change materials towards improved energy efficiency


Connect with PCM experts and industry leaders on LinkedIn

LinkedIn logoMore than 1,800 people have joined a LinkedIn group devoted to the discussion of phase change material and thermal energy storage. You are invited to join the Phase Change Matters group and connect with PCM and TES experts from around the world.

This month we welcome Scott Jamieson, health care account manager at Croda International Plc., Johannesburg, South Africa; Christoph Thomas of HeatVentors, Budapest, Hungary; Chin How Lee, engineer at Cooling Boy Engineering, Kuala Lumpur, Malaysia; Ajit Basargi, applications manager at Alkegen, Pune, India; Raphael Haase, country sales manager at Croda, Viersen, Germany; and Yann Bastoen, doctoral student in civil engineering at Artois University, Arras, France.

As part of his Ph.D. work, Yann is compiling a database of PCMs used for thermal energy storage in building applications. He has already collected thermo-physical, kinetic and chemical properties of PCMs made by major manufacturers. He is also seeking information on the economic and environmental aspects of each PCM, such as abundance of source material, carbon footprint and recyclability.

If you have such data, or know of potential sources, please contact Yann at yann.bastoen@junia.com


Does your company, agency or university have a job opening, new research, new product or other news you’d like to share? I would love to hear from you. Please contact newsletter editor Ben Welter at benedict.welter@gmail.com.


RAL Quality MarkThis newsletter is made possible through the generous support of the RAL Quality Association PCM and the members listed below. To learn more about the association, including membership benefits, please contact Stefan Thomann, executive director, at pcm@kellencompany.com.

Axiotherm GmbH | B Medical Systems | Croda International Plc. | ISU Chemical Co. Ltd. | RuhrTech | Microtek Laboratories | PCM Technology | PLUSS Advanced Technologies | PureTemp LLC | Rubitherm Technologies GmbH | Sasol Germany GmbH | S.Lab Asia Inc. | Sunamp Ltd. | va-Q-tec AG