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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.




Research roundup: Enhanced bulk-organic PCMs; cementitious composites; business clothing incorporating PCMs; more

Ben Welter - Wednesday, February 21, 2018

New formulation and characterization of enhanced bulk-organic phase change materials [Energy and Buildings]

Numerical analysis of the freeze-thaw performance of cementitious composites that contain phase change material (PCM) [Materials & Design]

Thermal Properties of Lauric Acid Filled in Carbon Nanotubes as Shape-stabilized Phase Change Materials [Physical Chemistry Chemical Physics]

Thermo-physiological comfort of business clothing incorporating phase change materials in a cold environment [International Journal of Clothing Science and Technology]

Phase change material thermal energy storage for a large scale ammonia chiller/heat pump system [International Institute of Refrigeration]

Case Study of Load Shifting Using Thermal Energy Ice Storage in Public Facilities [Journal of Facility Management]

Microencapsulated phase change materials with composite titania-polyurea (TiO2-PUA) shell [Applied Energy]

Numerical study on the effects of fins and nanoparticles in a shell and tube phase change thermal energy storage unit [Applied Energy]

Research roundup: Acrylic PCM microcapsules; paraffin-water nanoemulsion; two-tank molten salt TES; more

Ben Welter - Wednesday, February 14, 2018

Non-linear system identification of a latent heat thermal energy storage system [Applied Thermal Engineering]

Tailoring of bifunctional microencapsulated phase change materials with CdS/SiO2 double-layered shell for solar photocatalysis and solar thermal energy storage [Applied Thermal Engineering]

Preparation of acrylic PCM microcapsules with dual responsivity to temperature and magnetic field changes [European Polymer Journal]

Paraffin wax–water nanoemulsion: A superior thermal energy storage medium providing higher rate of thermal energy storage per unit heat exchanger volume than water and paraffin wax [Energy Conversion and Management]

Preparation and characterization of stearic acid/polyurethane composites as dual phase change material for thermal energy storage [Journal of Thermal Analysis and Calorimetry]

Efficiency analyses of high temperature thermal energy storage systems of rocks only and rock-PCM capsule combination [Solar Energy]

Thermal performance analysis of PCM wallboards for building application based on numerical simulation [Solar Energy]

Thermal energy storage in district heating: Centralised storage vs. storage in thermal inertia of buildings [Energy Conversion and Management]

Two-tank molten salts thermal energy storage system for solar power plants at pilot plant scale: lessons learnt and recommendations for its design, start-up and operation [Renewable Energy]

Patent application: PCM compositions and methods of making the same

Ben Welter - Thursday, February 08, 2018

U.S. patent application 20180037788 (applicant Phase Change Energy Solutions, Asheboro, N.C.):

"In one aspect, compositions are described herein. In some embodiments, a composition comprises a phase change material, a hydrophobic sorption material, and a viscosity modifier. In some embodiments, a composition comprises a foam and a latent heat storage material dispersed in the foam, the latent heat storage material comprising a phase change material and a hydrophobic sorption material."

Research roundup: Heat transfer model based on energy asymmetry; smart concretes; traction transient cooling; more

Ben Welter - Wednesday, February 07, 2018

A new heat transfer model of phase change material based on energy asymmetry [Applied Energy]

Multifunctional smart concretes with novel phase change materials: Mechanical and thermo-energy investigation [Applied Energy]

The melting of salt hydrate phase change material in an irregular metal foam for the application of traction transient cooling [Thermal Science and Engineering Progress]

Solar Energy Latent Thermal Storage by Phase Change Materials (PCMs) in a Honeycomb System [Thermal Science and Engineering Progress]

Fabrication and characterization of diethylene glycol hexadecyl ether-grafted graphene oxide as a form-stable phase change material [Thermochimica Acta]

One-dimensional model of a stratified thermal storage tank with supercritical coiled heat exchanger [Applied Thermal Engineering]

Using silicagel industrial wastes to synthesize polyethylene glycol/silica-hydroxyl form-stable phase change materials for thermal energy storage applications [Solar Energy Materials and Solar Cells]

Steam-PCM heat exchanger design and materials optimization by using Cr-Mo alloys [Solar Energy Materials and Solar Cells]

Sodium acetate trihydrate-chitin nanowhisker nanocomposites with enhanced phase change performance for thermal energy storage [Solar Energy Materials and Solar Cells]

Preparation and thermal properties of fatty acid/diatomite form-stable composite phase change material for thermal energy storage [Solar Energy Materials and Solar Cells]

Patent application: Cellulose capsules

Ben Welter - Tuesday, February 06, 2018

U.S. patent application 20180019036 (applicant Technion Research & Development Foundation Ltd., Haifa, Israel):

"A method for making an oil-in-water dispersion or water-in-oil dispersion is disclosed. The method comprises the step of mixing a hydrophilic medium, a hydrophobic composition and non-derivatized cellulose solution in an ionic liquid. ... The novel, highly stable nano/micro-scale slurries, based on cellulose encapsulated PCMs, have a relatively low viscosity at high concentrations, which increases their pumping efficiency and permits to increase the slurry concentration up to 45 wt. %, that allows to enlarge the efficiency of thermal energy transfer systems."

PCM briefing: Israeli startup introduces IceBrick; Ulster University launches energy storage research project

Ben Welter - Monday, February 05, 2018

Nostromo Energy of Israel has introduced the IceBrick, an energy storage system designed to store and discharge an amount of energy equivalent to 25 kWh of electricity consumed by cooling systems at peak demand hours. The 2,000-pound IceBrick contains plain water and a proprietary nucleate.

• A new report from Environment New York, an advocacy organization, says rising renewable energy production means that energy storage is ready for prime time. Thermal storage, utility-scale batteries and pumped-storage hydro are among the technologies discussed in the report, "Making Sense of Energy Storage: How Storage Technologies Can Support a Renewable Energy Future."

Ulster University of Northern Ireland has announced 6.7-million-euro cross-border research project to develop energy storage ideas for consumers. The European Union-funded project will explore energy storage methods such as thermochemical material storage and heat pump design. 

• The European Parliament has voted in favor of a proposal that would remove palm oil-based biodiesel from the European Union's list of renewable fuels by 2021. Indonesia and Malaysia, two of the world’s largest palm oil producers, have been increasingly critical of EU’s plans to phase out palm oil biodiesel, with both countries threatening retaliation in trade and taking the matter to the World Trade Organization.

• A CALMAC thermal energy storage system has helped Kings County Courthouse in Hanford, Calif., achieve LEED Silver Certification and reduce annual energy costs by more than $100,000. 

AkzoNobel is accepting submissions for its 2018 Imagine Chemistry initiative. The company's specialty chemicals unit is seeking to partner with startups and academics to bring innovative ideas to market.

• New in 2018: Membership in the American Oil Chemists' Society now includes free online access to three AOCS publications: the Journal of the American Oil Chemists' Society; the Journal of Surfactants and Detergents; and Lipids.

Pluss Advanced Technologies of India, maker of the MiraCradle neonate cooler, has signed a collaboration agreement with Dräger, a German-based medical and safety technology company, to spread use of the PCM-enabled device in Asia and Africa.

• Netherland's Eindhoven University of Technology has openings for three Ph.D. positions involved in the study of crystal hydrate heat storage.  

• A Spanish university that has developed new biobased phase change materials with enhanced thermal properties is looking for industrial partners interested in a technical cooperation or a license agreement. 

Patent application: Thermal energy storage apparatus with PCM

Ben Welter - Friday, January 19, 2018

Neothermal patent drawingU.S. patent application 20180017337 (applicant NeoThermal Energy Storage Inc., Timberlea, Canada):

"A thermal energy storage apparatus is disclosed. The apparatus includes a base and fluid flow plates which cooperate with the base to define a cavity; a phase change material contained within the cavity; an extendable extension spring [40] at least partially contained within the phase change material [14]; and end plates which cooperate with the fluid flow plates to define fluid flow channels. Inlet and outlet ports allow for the ingress and egress of a heat exchange fluid into the fluid flow channels. In operation, the extension of the extendable extension spring induces solidification of at least a portion of the phase change material from a supercooled liquid state to a solid state, releasing thermal energy, allowing for the transfer of thermal energy across the fluid flow plates from the phase change material to the heat exchange fluid."

Fluorination process enhances barrier properties of HDPE

Ben Welter - Friday, January 12, 2018

HDPE panelsHigh-density polyethylene (HDPE) is a popular choice for containment of paraffin- and plant-oil-based phase change material. But under some conditions, PCM-filled HDPE containers are vulnerable to leaching.

Inhance Technologies of Houston has developed a process called ColdShield™ to enhance HDPE's barrier properties. In an email interview, Prakash Iyer, senior vice president of business development and technology at Inhance, answered questions about the process.

Q: How does ColdShield work?

A: HDPE is not stable when exposed to organic solvents such as paraffins and plant oils. Many PCM formulations are organic in nature and will readily permeate through HDPE, causing contamination of the surroundings and irreversible damage to the contents being transported. Inhance, through the use of its proprietary barrier treatment process, developed ColdShield technology to specifically prevent permeation of paraffin and plant oil based phase change materials.

"ColdShield provides a double barrier layer by protecting the inside and outside wall of the PCM container. The technology converts the surface of ordinary HDPE into a high-performance barrier material which repels paraffins and plant oils. The surface of HDPE is converted into a ‘PTFE’ like material with excellent barrier properties. By keeping the PCM formulation in the bottle from permeating, Inhance’s ColdShield prevents temperature drifts of the packaging due to selective absorption of the PCM formulation into the bottle walls. In addition, due to its superior barrier protection, ColdShield allows reuse of the PCM containers for many years with minimal to no reconditioning."

Q: Inhance tested five PureTemp formulations in ColdShield-enhanced HDPE containers. Describe the results.

A: "Inhance tested PureTemp 4N, PureTemp 8N, PureTemp 18X, PureTemp 20X and PureTemp 23N to study how these PCM formulations permeated through HDPE containers. Testing for permeation was done at 50° over 28 days, which would roughly equate to a two-year shelf life. All PureTemp PCM formulations, except for PT20X, showed varying amounts of permeation (ranging from 0.25-3% weight loss) through HDPE. The same PCM formulations when tested in ColdShield-treated HDPE containers exhibited less than 0.1% permeation weight loss. In addition to PureTemp formulations, Inhance also tested hexadecane and tetradecane, which are commonly used in PCM formulations. The permeation rates of hexadecane and tetradecane without barrier protection is 3-5%, while ColdShield reduces this to 0.1%. The chart below reflects the data."

Q: How do you test ColdShield-treated containers for leaching?

A: "One of the simplest tests to evaluate for leaching is to do a weight-loss test on HDPE containers filled with these PCM formulations. Testing can be done at different temperatures for varying amounts of time. 49CFR.173 Appendix B, describes the commonly used test procedure to evaluate for permeation of liquids in plastic packaging, and is generally done at 18°C for 180 days, or 50°C for 28 days, or 60°C for 14 days. Per the U.S. Department of Transportation, the maximum permissible permeation rate for the above testing conditions should not be greater than 2% for nonpoisonous liquids."

Q: Describe the shape and dimensions of the containers tested with PureTemp, including wall thickness. 

A: "The testing was done with 16-ounce round containers with a nominal wall thickness of 1mm. To give one perspective, the 16-ounce round container will be the best-case scenario for permeation since the surface area to volume of liquid is minimized, resulting in lower permeation numbers. In the case of HDPE PCM containers, they are generally flat and rectangular, increasing the surface area to volume ratio, which would result in worse permeation numbers."

Q: Is the ColdShield process patented?

A: "ColdShield technology has been developed by Inhance using proprietary process technologies. The technology itself is based on post-mold fluorination of HDPE containers, but Inhance has worked to understand the market needs and worked closely with its customers to come up with the optimum barrier required to eliminate permeation of PCM formulations."

Q: Are ColdShield-enhanced HDPE containers now being produced commercially for any PCM manufacturers?

A: "ColdShield-enhanced HDPE containers are being commercially used by some of the largest manufacturers of PCM formulations as well as OEMs involved in the cold chain logistics chain."
Q: On a percentage basis, how much does the ColdShield process add to the cost of an HDPE container?

A: "The cost of ColdShield is minimal compared to the value that it brings to the OEMs. The permeation of PCM into the package can result in costly recalls and contamination issues. Cold chain is used to often transport vaccines, biologics and organs across the globe and the loss/contamination of these contents can run into the millions. ColdShield provides the best barrier solution for HDPE rigid gel packs, thereby maintaining the PCM composition, while providing safe storage during transportation."

Q: Has research on ColdShield performance been published?

A: "ColdShield brochures are available on For further information contact Inhance is glad to partner with companies to educate them on the advantages of ColdShield and works closely with its customers to provide the optimum solution. Inhance also has test capabilities to carry our permeation testing as well as other fitness testing of different PCM formulations."

Q: Has the effect on heat transfer or other PCM performance characteristics been tested? How about the effect of, say, thousands of freeze/melt cycles on barrier properties?

A: "Inhance’s ColdShield technology has been tested and approved by OEMs and molders through stringent testing, including, but not limited to, permeation, freeze/melt cycles as well as mechanical testing. Since ColdShield is not a coating – ColdShield chemically transforms the surfaces of containers into a material that is resistant to solvents – there is no cracking or peeling of the barrier layer. In addition, since ColdShield does not change the bulk properties of the rigid gel pack, there is no change in the heat transfer profile. In addition, ColdShield provides a double layer of protection since the inside and the outside of the container is protected equally."

Q: Who are your competitors in this field, and how are your processes different?

A: "There are three or four options when it comes to how PCMs are packaged today. These include non-barrier HDPE containers, metal or barrier plastics such as nylon. In many cases, Inhance's ColdShield is the most economical and the best performing barrier solution in the market. As the market moves more towards better temperature control ranges, more paraffins and plant-oil based PCM formulations, ColdShield is the preferred barrier solution in the industry."

Q: What is the potential market size for ColdShield?

A: "Inhance currently treats millions of rigid PCM containers using its ColdShield technology. The market for these containers that need barrier protection from PCM formulations is growing significantly, due to some of the above stated reasons. The addressable market for Inhance’s ColdShield continues to grow with greater adoption of PCM formulations."

Inhance Technologies video image

A company video illustrates some of Inhance Technologies' capabilities.  

Patent application: Capsules having surfactant tethered outer shells

Ben Welter - Thursday, January 11, 2018

U.S. patent application 20180009996 (applicant Microtek Laboratories Inc., Dayton, Ohio):

"Microcapsules are disclosed that have a core composition encapsulated within a polymer wall, and an inorganic shell connected to an exterior surface of the polymer wall by a surfactant. The inorganic shell has a cation attracted to the surfactant and an anion or anion equivalent chemically bonded to the cation to form the shell or has the metal portion of a metal-containing compound attracted to the surfactant to form the shell. The shell may comprise a Ca, Mg, or Ag metal compound. The shell may be a graphene oxide-metal compound."

Patent application: Encapsulated PCM and thermal battery

Ben Welter - Thursday, January 11, 2018

U.S. patent application 20180010862 (Valeo Systemes Thermiques, Le Mesnil Saint-Denis, France):

Valeo patent drawing"The present invention relates to an encapsulated phase-change material comprising a phase-change material (3) contained within a tube (5), said tube being made of plastic and that it has a sealing weld (9) at least at one of its ends. ... The presence of sealing welds allows good sealing and also reduces the risk of leakage of phase-change material notably when the latter is in the liquid phase."