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The award-winning Phase Change Matters blog tracks the latest news and research on phase change materials and thermal energy storage. E-mail tips and comments to Ben Welter, communications director at Entropy Solutions. Follow the blog on Twitter at @PureTemp. Subscribe to the weekly PCM newsletter. Or join the discussion on LinkedIn.




PCM briefing: New EU energy standard takes effect; new research on inorganic phase change material

Ben Welter - Monday, July 09, 2018

• The new version of the European Union's Energy Performance of Buildings Directive takes effect July 9. The directive is the EU's main legislative instrument designed to promote improved energy performance of buildings. Member states will have 20 months to transpose the new elements into national law.

• A proposal to use microencapsulated phase change material to help motor vehicles run smoothly in extreme cold has won the ClimateLaunchpad competition in Azerbaijan. A team of chemical engineering students from Baku Higher Oil School developed the concept. The team will represent Azerbaijan at the ClimateLaunchpad finals in Scotland Nov. 1-2, 2018.

• New from Research Reports: "2018 Global Inorganic PCMs Industry Report – History, Present and Future"

PCM briefing: Ecozen Solutions wins Ashden Award; Fraunhofer researchers among winners in Imagine Chemistry challenge

Ben Welter - Monday, June 11, 2018

Ecozen cold storage unit

Ecozen Solutions of India, which makes portable solar cold rooms for use on small farms, is one of six international winners in the 2018 Ashden Awards competition. The Ecofrost system's thermal storage unit can store power for more than 36 hours in case of cloudy or rainy weather. The organizations will be honored at a ceremony at the Royal Geographical Society in London on Thursday, June 14. 

Axel Kraft and Martin Peters of Fraunhofer UMSICHT are among the winners of the 2018 AkzoNobel Imagine Chemistry challenge. Kraft and Peters will receive support from LuxResearch to further develop a catalytic process for making alcohols from more sustainable raw materials. Overall, 10 startups and researchers were chosen as winners from a group of 20 finalists at a three-day event held at Chalmers University in Gothenburg, Sweden.

A call for papers has been issued for the 10th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings. Topics include ventilation strategies and measurement techniques; HVAC systems; smart technologies for zero-energy buildings; and design and energy modeling. Abstracts are due by Nov. 1. The conference will be held Sept. 5-7, 2019, in Bari, Italy.  

• Researchers at the Jülich Solar Tower test facility in Germany have reached a milestone in the development of a new receiver concept for solar tower power plants. During a test of the centrifugal receiver CentRec for the generation and storage of solar high temperature heat, an average particle temperature of 965 degrees Celsius has been measured at the receiver outlet. The bauxite particles used in the system are available at prices that enable cost-effective thermal storage. “The proof of the high operating temperature is an essential condition for the targeted commercialization of this new receiver concept,” said Dr. Reiner Buck, head of solar tower systems at the DLR Institute of Solar Research

• June 15 is the last day to get the early bird rate for this year's Advancements in Thermal Management Conference (Denver, Aug. 8-9). Topics include thermal materials, thermal imaging, thermal characterization, modeling, battery cooling and thermal simulation. Joe Kelly, senior materials scientist at Outlast Technologies, is among the speakers. His topic: "Enhancing Thermal Stability and Performance of Lithium-ion Batteries using Latent Heat Storage (LHS) Technology."

Phase change composite shows potential to double AC compressor efficiency

Ben Welter - Friday, June 01, 2018

Using a phase change composite material, researchers at the University of Illinois at Chicago have developed a novel thermal energy storage system that has the potential to downsize conventional air-conditioner compressors by 50 percent and double compressor efficiency during off- and mid-peak hours.

The research is described in a paper titled “Design and optimization of a hybrid air conditioning system with thermal energy storage using phase change composite,” recently accepted for publication in Energy Conversion and Management. One of the authors, Said Al-Hallaj, a research professor of chemical engineering at UI-Chicago and CEO of AllCell Technologies LLC, answered a few questions by e-mail.

Q: Who led the research team, and how long did the project take?

A: “It is an ongoing project since 2015 at the University of Illinois at Chicago, where I work as a Research Professor of Chemical Engineering, and part of the PhD thesis for my graduate student Ahmed Aljehani.”

Q: Who funded the project? 

A: “Ahmed has a scholarship from his government in Saudi Arabia and we get technical support from our industry partners NETenergy and AllCell Technologies LLC.”

Q: Who supplied the PCM?

A: “I believe it is n-tetradecane (C14H30) PCM that we bought from a distributor and not sure about actual source.”

28 slabs of phase change composite materialQ: What is its peak melting point? 

A: “4-6 degrees Celsius.”

Q: What is its thermal storage capacity?

A: “180 kJ/kg (78% PCM, 22% graphite).”

Q: Describe the benchtop PCC/TES system size, components and functionality.

A: “The actual 4 kWh PCC-TES structure is made of 28 slabs of PCC [right]. The whole PCC-TES structure is thermally insulated with building insulation materials. Each slab represents a graphite structure that has been soaked into n-tetradecane for at least 24 h until impregnated with n-tetradecane. The slabs are numbered from top to bottom; top being number 1. The second component is the copper tubes or the copper coils, which pass back and forth in between the 28 slabs. The copper tubes enter the PCC-TES structure from the top and exits from the bottom of the structure.”

Q: Is the concept intended mainly for commercial AC systems, or could it be adapted for residential use?

A: “It should work for both, but commercial AC applications are more economically beneficial due to rate structure and peak demand requirements.”

Q: What are the next steps in developing this concept?

A: “NETenergy, our technology commercialization partner, is partnering with National Renewable Energy Laboratory and a major OEM to build and test a full-scale prototype at NREL facilities in the next year or so.”

Contributions sought for new database on thermal storage materials

Ben Welter - Monday, April 16, 2018

A new database for thermal energy storage materials is being developed within the framework of the International Energy Agency’s Energy Conservation through Energy Storage group, Annex 29 and SHC Task 42.

The database is designed to provide characteristic data for phase change, sorption and thermochemical materials. The website,, also offers a wiki with definitions related to thermal energy storage. Both areas are open for contributions.

The phase transition data provided for PCMs must be measured according to a DSC-measurement standard. To ensure the quality of the submitted data, contributors must provide a reference measurement using a PCM provided by Fraunhofer ISE.

Stefan Gschwander, head of Group Heat and Cold Storage at Fraunhofer ISE in Freiburg, Germany, said all submitted data will undergo a review process. “If the data is in line with our requirements it can be published in the public area,” he said.

So far, 15 PCMs are listed in the public area. A restricted area of the database is limited to  independently measured materials.

“The data stored is high-quality data which can be used for research, for example
simulation or to design a system,” Gschwander said. “So for our database, the manufacturers normally do not provide data but sample material that is measured from the institutions that are able to measure according the definitions. So far we have measured PCM from Rubitherm, Sasol and BASF. …

“So far we have about 20 different materials in the restricted area and, as we have used it for the development of the measurement standard, many of the materials have been measured several times by different laboratories so that we have a lot more measurements stored in the database.”

Fraunhofer ISE offers independent characterization of PCM, with fees depending on the material and the DSC required to do the measurement.

The ECES is a technology collaboration group that supports the development of electrical energy storage, thermal energy storage, distributed energy storage and borehole thermal energy storage. For more information on the material database project and characterization services, contact Gschwander at

Swedish university developing PCM/TES design tool for buildings

Ben Welter - Monday, April 09, 2018

Researchers at Chalmers University of Technology in Sweden are developing a design tool for PCM-based thermal energy storage for heating and cooling of buildings.

The project is being conducted by the Division of Building Technology within the university's Architecture and Civil Engineering Department. Sweden's Environmental Protection Agency and Energy Agency and the university are jointly funding the effort.

To better understand the needs of potential users of the tool, the research team is inviting professionals in the building sector – such as real estate owners, energy consultants, PCM producers and specifying engineers – to participate in a survey, whether or not they have PCM experience. The survey can be completed in 10 to 15 minutes. Personal data will be kept confidential. Participants who wish to receive the findings of the survey are asked to provide their email address at the end of the questionnaire.

For more information on the project, contact Dr. Nikolaos Stathopoulos, nikstat[at]

Hybrid sensible-latent heat storage concept achieves high energy densities

Ben Welter - Tuesday, October 31, 2017

Christoph Zauner of AITChistoph Zauner, a research scientist at the Austrian Institute of Technology, has been investigating the use of phase change material for a variety of applications since 2010. His most recent papers include “Experimental characterization and simulation of a hybrid sensible-latent heat storage,” published earlier this year in Applied Energy. He discussed his work in an email interview. 

Q: How did you first become interested in phase change material?

A: I worked for quite some time in the field of solar thermal energy and was especially focusing on industrial application with non-standard solar collector, so-called medium temperature collectors. This more efficient class of collectors (concentrating and non-concentrating) can produce temperature up to 250° C heating pressurized water, oil and generate steam. In order to achieve high solar fractions (i.e. cover much more than 10% of the total required process energy by solar energy), one needs to store energy. Standard storages (steam, oil, water) have limitations and latent storage certain advantages. Thus, we started developing such storages. In the meantime, we want to use it for a much broader range of applications (not only solar thermal).

Q: Describe the hybrid sensible-latent heat storage concept you have been working on.

Inverted shell and tube heat exchanger

A: In our new concept, we place the PCM inside the tubes of a modified shell-and-tube heat exchanger [shown above]. This is in contrast to the well-known approach of placing it outside. On the shell side we use a heat transfer fluid (in our first prototype we used oil) which at the same time serves as a sensible storage medium. Thus, we achieve a hybrid sensible-latent heat storage, which offers several opportunities:

• Heat transfer fluid (in our case oil) and PCM fractions can be varied over a wide range, i.e. a hybrid sensible-latent heat storage is realized. Advantages of both domains can be exploited, such as high energy density of the PCM and high power density of sensible storages

• Fewer weld seams as for the standard concept (PCM outside many small tubes) leads to storage cost reduction

• Larger heat transfer area between tubes and PCM enables higher storage power

• Our tubes serve as a macroencapsulation of the PCM, which serves as protection and increases storage lifetime.

Q: Is HDPE in use as a PCM in any commercialized application?

A: HDPE is a so-called commodity plastics. It is the kind of polymer used most out of all polymers. As such it is produced in a multi-million-ton scale each year. Also a versatile recycling industry is in place, which allows for further cost reduction potential (we know which types are suitable and which ones are not). Usually HDPE is used to contain PCMs only. There are no commercial applications yet, where HDPE is used as PCM. Currently we are investigating various possible applications.

Q: How do you anticipate the viscosity of the PCM affecting the thermal modeling? At what point does this significantly contribute to the internal convection in the tube?

A: Convection plays a minor role for our HDPE grade. This may be somewhat different for other grades and was analyzed in our lab. Our models can be adapted to incorporate convection, too. If necessary, we also have 3d-CFD models available.

AIT test tank
A 40 kWh, 100 kW peak power hybrid latent-sensible storage system was successfully tested at AIT labs at temperatures up to 200 °C.
Q: Beyond manufacturing costs, what are the benefits of the inverted shell-and-tube in comparison to other geometries such as a packed bed?

A: Apart from the advantages mentioned above, there is one particular key advantage over packed beds: packing density. Our storage can achieve up to 90% PCM volume density, whereas the theoretical limit for ideally packed spheres is 74%. In a packed bed, however, one does not have “ideal packing,” but the situation of “random packing,” where PCM volume fractions of 64% are achieved.

We found a certain way, which we do not disclose, how to actually fill up the whole tubes even for the crystallized (shrinked) PCM. Usually, PCM macroencapsulations are filled up to 100% only in the molten state, which further reduces the final volume PCM fraction of the whole storage (i.e. kWh/m3).

So summing up: We achieve much higher energy densities. 

Q: How was the DSC data implemented into the thermal modeling?

A: Actual measurement data can be easily implemented in our Dymola model. We use different approaches for the two models described in the paper (Stefan-model, cp(T)-model).

However, it is important to emphasize that one has to perform the DSC measurement “in the correct way.” This means one has to use the correct DSC parameter sets. By comparing the data obtained from different DSC settings to experimental storage data, we found out that very often DSC measurements are done in the wrong way. Wrong DSC settings lead to incorrect material values (especially melting temperature, sub-cooling and phase change enthalpy). However, we know now how to do it correctly and implemented the corresponding curves in the models.
Q: Would a sharper phase change peak be advantageous to the proposed application? How would this also affect the Stefan model?
A: We already designed storages for different applications (various combinations of low/high power, low/high capacity, different temperature levels). Sometimes it is very important to actually have a PCM with a sharp peak and sometimes even large subcooling doesn’t matter. It depends on the application.

Of course, one has to be careful by applying the various models (not only the Stefan model) and not to spoil the underlying assumptions. We learned a lot in that direction by comparing experimental storage data to simulations and know now very well where the limits are.
Q: What are the next steps in your investigation of this storage concept for district heating networks and industrial processes? How close is it to possible commercialization?

A: It is important to emphasize that AIT is not a university, but more like a real company which has to do “real business” and earn “real money.” We do business in various ways and offer different business models.

This ranges from material characterization or simulations directly done (and paid) by customers. We also offer storage engineering using our models and experimental know-how to storage manufacturers. We also demonstrate storages at real demo sites (currently we have projects in polymer extrusion and aluminum die casting) and evaluate their potential in various companies (e.g. we are currently investing a specific process in steel industry using a PCM-steam-storage concept).

We can provide various services or even serve as a “one-stop-shop” for energy optimization of industrial processes using storages. This starts from analyzing the process in detail (incl. monitoring), designing the storage (including integration), organization of storage manufacturing, integration at the plant and commissioning. Also this includes financing aspects (contracting, subsidies, R&D projects etc.).

The storages are permanently optimized but can be bought right away as we are only using industrially available PCMs (we also tested [PureTemp PCMs] and might use them, of course) and heat exchanger/storage manufacturing techniques.

Q: What other projects are you working on that might be of interest to the PCM community?

A: We also work on “overheating solutions” using PCM. Some articles have been published in that direction already, including “High temperature phase change materials for the overheating protection of facade integrated solar thermal collectors.” Also, we employ PCMs in car batteries and developed concepts there. We simulated and tested various prototypes of real batteries.

A related topic is development of new insulations, especially aerogel-based. This is very much needed for storages and also for energy efficiency in industries (“stop wasting energy first, then re-use it!”). 

[For more examples, see]

We are very much looking for partners for new PCMs. We do not produce them on our own. However, we do some development with partners on organic PCMs.

PCM briefing: Three molten salt projects projects move forward in U.S., Germany

Ben Welter - Tuesday, September 19, 2017

Terrafore salt encapsulation• The U.S. Department of Energy has released funding to the Argonne National Laboratory for a scaled-up round of independent testing of Terrafore Technologiesencapsulated thermal energy storage in phase change salts. The materials, shown at right, are designed to operate in temperatures to greater than 800° C in a single tank that acts as both storage and heat exchanger.

• The Department of Energy has invited Terrestrial Energy USA to submit the second part of its application for a federal loan guarantee to support the licensing and construction of its Integrated Molten Salt Reactor

DLR has fired up the TESIS thermal storage facility in Cologne, Germany. One hundred tons of molten salt is alternately heated and cooled from 250 to 560 degrees Celsius in the test facility, which is designed to allow industrial-scale testing of temporary storage methods for renewable energy and waste heat. 

• Va-Q-tec AG is reporting a strong increase in its service business in the first half of 2017, up 54 percent to 8.8 million euros. The company, based in Würzburg, Germany, develops, manufactures and sells vacuum insulation panels and phase change materials. 

• New from Zion Market Research: "Global thermal storage market is expected to reach USD 5.7 billion in 2022, growing at a CAGR of 10.7% between 2017 and 2022"

Advanced combat clothing featuring "four-way stretch phase-change material" was on display last week at the annual Defense and Security Equipment International show in London. Royal College of Art researchers and designers collaborated with the Ministry of Defense on the prototypes, which are designed to be easy to run in and comfortable to wear.  

Extremely high-temperature TES prototype under development in Europe

Ben Welter - Thursday, August 03, 2017

At seven locations around Europe, a consortium of universities, R&D centers and an Italian company is investigating materials and devices for thermal energy storage at temperatures of up to 2000º C, well beyond the maximum operating temperatures of systems in use today.

The AMADEUS project, funded by the European Union’s Horizon 2020 program, aims to build a prototype of a system that stores electricity in the form of extremely dense heat, using a solid state device known as a hybrid thermionic-photovoltaic converter. The project’s success hinges on the development of novel silicon and boron alloys with melting temperatures well above 1000º C and energy densities of more than 1 kilowatt hour per liter.

Alejandro DatasAlejandro Datas, a research scientist at the Technical University of Madrid’s Institute of Solar Energy, is the project’s scientific coordinator. He responded to questions about the project by email.

Q: What is your role as scientific coordinator?

A: My role is to coordinate the project activities and make them converge at the end in a single prototype, which will demonstrate the feasibility of this new concept. I’m also involved in the development of the infrared-sensitive PV cell (or thermophotovoltaic cell) that will be used to convert radiant heat into electricity in these systems.

Q: Work on the project began about seven months ago and is scheduled to continue through 2019. What important milestones have you reached so far, and what are the next important milestones?

A: During the first six months of the project, we have characterized some Si-B alloys with different compositions to determine their most important thermophysical parameters, such as latent heat and thermal conductivity. By means of solubility and wettability experiments, we have also studied the interaction of these alloys with some nitride- and carbide- refractories that are intended to be used for the container walls. Also, we have fabricated an experimental setup that will enable the characterization of the energy converters at very high temperatures. The next expected milestones will be the fabrication of the first generation of hybrid thermionic-photovoltaic converters, as well as the determination of the optimal Si-B alloy composition based on an exhaustive analysis of their thermophysical properties and their reactivity with the container walls.

Q: Can you describe, briefly, the PCM you are developing, and what is meant by "the silicon-boron system"?

A: The Si-B system refers to an alloy containing silicon and boron elements in some specific proportions. Silicon and boron have two of the highest latent heats among all the elements in the periodic table. But they show some important drawbacks: in the case of silicon, it expands upon solidification (like water) which leads to very severe constraints for the vessel design; in the case of boron, it has a high cost. The Si-B system is expected to exploit the best of both elements. For instance, the eutectic composition of this alloy (having only 5% of boron) is expected to notably improve the properties of pure silicon PCM at a reasonable cost increment. In brief, Si-B alloys have potential to meet the main requirements for being considered an ideal PCM: low cost, high latent heat and high thermal conductivity. Surprisingly, very little attention has been paid to this system so far, and to our knowledge, AMADEUS is the very first project to investigate these materials in detail for energy storage applications.

Q: What are some of the PCM containment materials and structures under consideration?

A: One advantage of Si-B PCMs is their high thermal conductivity. Thus, they could be stored in relatively large containers without needing very advanced encapsulation arrangements. This minimizes the impact of the container in the final cost of the system. In order to achieve the minimum interaction between the container and the Si-B PCM, we are investigating several kinds of vessel liners based on nitrides (e.g. BN or Si3N4), carbides (e.g. SiC) and oxides (e.g. SiO2).

Q: How does AMADEUS differ from the molten silicon storage technology under development by 1414 Degrees in Australia?

A: Apparently, 1414 Degrees uses pure silicon PCM and “conventional” dynamic engines to transform latent heat into electricity. 1414 Degrees probably needs to reach the market soon, so that they must use reliable and mature technologies. In AMADEUS we are exploring new technologies with greater potential that still require further development. This is the case of Si-B alloys, which may enable higher energy densities and more efficient vessel designs. This is also the case of the thermionic and thermophotovoltaic converters, which will eventually enable more efficient, compact and simpler systems, not requiring working fluids or moving parts. We certainly hope that companies such as 1414 Degrees, and others that could start activities in the near future, could benefit from the results of AMADEUS project.

PCM briefing: Tessol featured in Forbes India; Terrafore Technologies selected for Argonne program

Ben Welter - Monday, June 05, 2017

Thermal Energy Service Solutions, maker of a PCM-based "plug-and-chill" refrigeration system for delivery trucks, is profiled in this month's issue of Forbes India. The system's heat exchanger is designed to keep the refrigerator on the truck within the optimal temperature range for a full day’s operation without drawing power from the engine. The heat exchanger can be fully charged in about six hours at any power outlet.

C-Therm Technologies will be among the exhibitors the Techtextil North America trade show in Chicago June 20-22. The company will demonstrate its non-destructive TCi Property Analyzer, which is designed to characterize the thermal performance (the “warm feel” or “cool touch”) of textiles, fabrics and apparels.

Terrafore Technologies of Minneapolis is one of seven small businesses recently selected to collaborate with researchers at Argonne National Laboratory as part of the Department of Energy's Small Business Vouchers program. Terrafore and Argonne will test the reliability of phase change salt capsules for a compact high-temperature thermal energy storage system for concentrated solar power.

SpecialChem is offering an online course titled "How to Search & Map U.S. Patents for Patentability." The 90-minute course, scheduled for June 28, is designed to for R&D people "looking to avoid patent infringement by enhancing their patent searching and mapping skills." The cost for three attendees on one connection is 300 euros.

PCM briefing: Pluss VP honored as 'Innovator under 35'; BASF partners with Hewlett Packard Enterprise on new supercomputer

Ben Welter - Tuesday, March 21, 2017

Ankit Jhanwar, VP for corporate planning and strategy at Pluss Advanced Technologies, was honored as one of 10 "Innovators under 35" at EmTech India 2017.

Sunamp Ltd., maker of PCM-based heat batteries, is one of eight finalists for an Ashden UK Award. Winners will be announced at a ceremony in London on June 15. The competition recognizes excellence in the field of green energy.

Hewlett Packard Enterprise will work with BASF to develop a supercomputer that will sharply reduce the time it takes to run simulations and modeling in chemical research. "The new supercomputer will promote the application and development of complex modeling and simulation approaches, opening up completely new avenues for our research at BASF,” said Dr. Martin Brudermueller, chief technology officer at BASF.

McKinsey & Co. analysts say a slowdown in the chemical industry's financial performance over the past five years reflects important changes in the industry’s fundamentals. One of their recommendations: "Incumbent specialty-chemical players must prepare for further encroachment of commoditization and erosion of their historical advantages when attackers from developing markets gain more experience and become increasingly technologically savvy."

California lawmakers have introduced legislation to encourage more clean energy resources to address peak load. The bills would require utilities to deploy clean energy during peak demand in order to meet the state's aggressive greenhouse gas and renewable energy goals.