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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.

Two Entropy advisors, Dr. Mohammed Farid and Lucas B. Hyman, are pleased to take your questions about PCMs and thermal energy storage. Send your questions to bwelter@puretemp.com. We'll select the best and post the answers here each week.

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Research roundup: PCM compatibility with metals, plastic; desiccant packet for cooling vest; paraffin viscosity; more

Ben Welter - Thursday, March 23, 2017

Investigation of the corrosive properties of phase change materials in contact with metals and plastic [Renewable Energy]

Preparation and thermal properties of SAT-CMC-DSP/EG composite as phase change material [Applied Thermal Engineering]

A numerical study on the usage of phase change material (PCM) to prolong compressor off period in a beverage cooler [Energy Conversion and Management]

Abilities and limitations of thermal mass activation for thermal comfort, peak shifting and shaving: A review [Building and Environment]

Corrosion effect of phase change materials in solar thermal energy storage application [Renewable and Sustainable Energy Reviews]

A review for phase change materials (PCMs) in solar absorption refrigeration systems [Renewable and Sustainable Energy Reviews]

Sodium nitrate – Diatomite composite materials for thermal energy storage [Solar Energy]

Innovative PCM-desiccant packet to provide dry microclimate and improve performance of cooling vest in hot environment [Energy Conversion and Management]

Heat transfer study of phase change materials with graphene nano particle for thermal energy storage [Solar Energy]

Energy performance evaluation of heat-storage gypsum board with hybrid SSPCM composite [Journal of Industrial and Engineering Chemistry]

Empirical equation to estimate viscosity of paraffin [Journal of Energy Storage]

Yearly energy performance of a photovoltaic-phase change material (PV-PCM) system in hot climate [Solar Energy]

Research roundup: Microcapsule-based composites; porous cellulose acetate films; underfloor heating; more

Ben Welter - Tuesday, March 07, 2017

Experimental study on effective thermal conductivity of microcapsules based phase change composites [International Journal of Heat and Mass Transfer]

Multi-objective RSM Optimization of Fin Assisted Latent Heat Thermal Energy Storage System Based on Solidification Process of Phase Change Material in Presence of Copper Nanoparticles [Applied Thermal Engineering]

Buildings cooling: An experimental study of phase change materials storage for low-energy buildings [2017 International Conference on Communication, Control, Computing and Electronics Engineering ]

Aluminum Mesh and Phase-Change Characteristics of n-Octadecane for Thermal Energy Storage [Journal of Thermophysics and Heat Transfer]

Analytical analysis of latent heat thermal energy storage model for solar thermal power plants [14th International Bhurban Conference on Applied Sciences and Technology]

Analysis of graphene-encapsulated polymer microcapsules with superior thermal and storage stability behavior [Polymer Degradation and Stability]

Experimental and numerical investigations on the thermal performance of building plane containing CaCl2·6H2O/expanded graphite composite phase change material [Applied Energy]

Fabrication and characterization of porous cellulose acetate films by breath figure incorporated with capric acid as form-stable phase change materials for storing/retrieving thermal energy [Fibers and Polymers]

In-situ preparation of a shape stable phase change material [Renewable Energy]

Proposal of a PCM Underfloor Heating System Using a Web Construction Method [pdf] [International Journal of Polymer Science]

Research roundup: Novel PCM plaster; chitosan-derived carbon aerogel; carboxylic esters; Trnsys simulation; more

Ben Welter - Thursday, March 02, 2017

Thermal effects of a novel phase change material (PCM) plaster under different insulation and heating scenarios [Energy and Buildings]

Form-stable phase change material embedded with chitosan-derived carbon aerogel [Materials Letters]

Investigation of Unbranched, Saturated, Carboxylic Esters as Phase Change Materials [Renewable Energy]

A simulation study of a solar collector using phase change materials for air heating application needs [AIP Conference Proceedings]

Intensification of monostearin (phase change material) synthesis in infrared radiated rotating reactor: Optimization and heterogeneous kinetics [Energy Conversion and Management]

Preparation research of novel composite phase change materials based on sodium acetate trihydrate [Applied Thermal Engineering]

The quasi-enthalpy based lattice Boltzmann model for solid-liquid phase change [Applied Thermal Engineering]

Synthesis and thermal properties of novel solid-solid phase change materials with comb-polyurethane block copolymer structure for thermal energy storage [Thermochimica Acta]

Synthesis of epoxy-loaded poly(melamine-formaldehyde) microcapsules: effect of pH regulation method and emulsifier selection [Colloids and Surfaces A: Physicochemical and Engineering Aspects]

Dual-encapsulation of octadecanol in thermal/electric conductor for enhanced thermoconductivity and efficient energy storage [Materials Chemistry Frontiers]

A Trnsys simulation of a solar-driven ejector air conditioning system with an integrated PCM cold storage [AIP Conference Proceedings]

PCM briefing: Encapsulation market projected to hit $17.9 billion; report casts shadow on solar-plus-storage

Ben Welter - Monday, February 27, 2017

• The global microencapsulation market is expected to reach $17.94 billion by 2025, according to a new report from Grand View Research. Microtek Laboratories, Encapsys, BASF and Aveka Inc. are among the companies profiled in the report, "Microencapsulation Market Estimates & Trend Analysis By Application (Pharmaceutical, Household Product, Agrochemical, Food Additive, Phase Change Material), By Region (North America, Europe, Asia Pacific, RoW), And Segment Forecasts, 2014 - 2025"

• A Rochester Institute of Technology study casts a shadow on the economics of residential solar-plus-storage. The conclusion: A customer must face high electricity bills and unfavorable net metering or feed-in policies for "grid defection" to work. 

• New from Transparency Market Research: "Reusable Ice Packs Market - Global Industry Analysis, Size, Share, Growth, Trends and Forecast 2016-2024"

• New from QYResearch: "China Bio-Based Phase Change Materials Market Research Report 2017"

A one-day workshop on energy storage for building, solar and wind sectors will be held March 4 at Anna University in Chennai, India. Topics include integration of PCMs for passive cooling in buildings, energy-efficient cool thermal energy storage systems and thermal energy storage technologies for solar applications. 

The National Law Review has posted a detailed update on implementation of the newly revised Toxic Substances Control Act. A key takeaway: Resource and budgetary constraints under the Trump administration could have an impact on the Environmental Protection Agency’s ability to implement the new provisions.

• The latest issue of Chemical & Engineering News features a piece on “natural catalysts” derived from wild plants, mud and earthworms. 

Samit Jain, director at Pluss Advanced Technologies, talks about his company’s pharma logistics products in an interview with India's Financial Express.

Thanks to PCM insert, luxury chocolates melt in your mouth, not in the box

Ben Welter - Monday, February 20, 2017

In hot climates, chocolates bought at retail shops can end up melting on the way home. Pluss Advanced Technologies of India has introduced a packaging insert to keep the sweets in solid form during transit.

Pluss PCM insertDeveloped for ITC’s Fabelle line of premium chocolates, the insert features inorganic phase change material contained in a non-woven film. Vishnu Sasidharan, vice president of new product initiatives at Pluss, says the PCM was customized to keep the chocolate between 3º and 9º Celsius. The insert, designed for one-time use, measures about 170mm x 70mm. The goal is to maintain product quality and texture for one to two hours.

“The product was launched about five months back,” Sasidharan says. “It was available only in one hotel chain within ITC group of hotels. The boutique has gained much traction only in the last few months with ITC expanding it to not only within their group but in all the 5 star/7 star hotels across India.”

Pluss is working with other chocolate/confectionary companies to offer similar solutions for premium temperature-sensitive products.

A look inside an undergraduate team's solar thermal storage project

Ben Welter - Friday, February 17, 2017

The Solar Owl team

From left: Brandon Koyanagi, Will Wilson, Gerardo Rojo and Michelle Zdanowski

For their senior undergraduate project, four engineering students at Southern Illinois University Edwardsville developed a heat storage system designed to collect thermal energy from the sun and release it at night.

The Solar Owl combines water-based sensible heat storage in an insulated tank and latent heat storage through use of a hydrated salt phase change material. The PCM is contained in a continuous, multiple-coil vessel within the tank.

SIUE TES tankThe team – Brandon Koyanagi, Will Wilson, Gerardo Rojo and Michelle Zdanowski – designed, analyzed, built and tested a scale prototype of the apparatus.

“At full size,” Wilson says, “the tank would be capable of heating an average American home through the evening and night, fourteen hours, using heat accumulated from solar thermal collectors during a typical St. Louis-area winter day. The Solar Owl reduces the size of the heat storage tank by 40 percent when compared to a sensible-only storage solution.”

The team earned an A on the project and will continue to develop the system in graduate studies. Aside from securing a patent on the design elements and a trademark on the name, the team has no immediate plans to commercialize the system.

Here’s a Q&A with Wilson, who was selected as Outstanding Senior in the university’s Mechanical Engineering Department this year.

Q: Why did the team choose sodium acetate trihydrate as the phase change material? 

A: SAT fit our needs in four important ways. (1) SAT's latent heat of fusion is high enough to keep tank size adequately small. (2) SAT, and the necessary additives, are readily availability at low to mid cost. (3) SAT exhibits low toxicity and is environmentally friendly. (4) The melting point of 58 C lends itself well to our application. This melting point is low enough to be completely melted by heat collected from a standard flat-plate solar thermal collector, while also providing a good temperature delta for most hydronic loop appliances.

Q: What is the source of the SAT you're using? 

A: We utilized SIUE chemistry lab space to synthesize a custom solution of lab-grade hydrated sodium acetate crystals with a small amount of additional water to slightly lower the temperature needed for complete melting. Carboxymethyl cellulose (CMC) was added to mitigate phase separation and potassium sulfate to minimize supercooling.

Q: SAT typically exhibits supercooling. Is that a problem in your application? 

A: As the system is not intended to be a long-term heat store, supercooling was not desirable for our design. To reduce supercooling, we added potassium sulfate to the solution as a nucleating agent.

Q. Unmodified SAT's latent heat of fusion is typically 264–289 joules per gram, with a melt point of 58 C. Does your SAT fit those specs? 

A: Our SAT did fit within that range per gram of SAT in solution. Of course, the latent heat of fusion for the solution overall, including the extra water and additives, was somewhat lower.

Q: What triggers the release of the heat?

A: Heat is released as the tank temperature falls below the melting point (plus a correction for minimal supercooling, approximately 5 degrees Celsius).

Q: What heat transfer fluid is used between the solar collectors and the tank?

A: I should note that, since the storage tank was the focus of our project, our prototype simulated solar collectors using an electrically heated water bath with submerged heat transfer coil. The transfer fluid from the “collector” to the tank, and between the tank and the testing radiators, is a solution of propylene glycol. This was chosen for (1) its low environmental toxicity and (2) its sensible heat capacity, which is high enough to help maintain tank temperature, but low enough to facilitate an appropriate heat transfer rate.

Q: What are the key design elements of the container, and what material is it made of?

A: The PCM container is a set of interconnected concentric helical coils constructed from standard PEX tubing. A set of likewise interconnected helical heat transfer coils is interspersed between the PEX coils, allowing proximity of the heat source to melt the PCM during the day, with enough space between coils to allow free convective heat transfer to the surrounding water in the tank. This configuration has the following advantages:

• It holds a relatively large amount of PCM with large surface area for heat transfer to the water in the tank.

• The tubing diameter is small enough to allow for an adequate heat rejection rate from the PCM (given SAT’s low heat conductivity).

• The thermal conductivity of PEX is higher than many plastics, such that it does not present a bottleneck to the release of PCM heat. 

As far as our research informs us, our design also stands out in that the PCM solution may be readily drained and filled for system maintenance. According to the data we could locate, an SAT solution experiencing daily phase cycling has a predicted useful life of around 10 years. Allowing easy access to flush the PCM container and refill is therefore critical for long-term maintenance and also for the case where the SAT formulation fails early, becomes contaminated, or requires testing or monitoring.

For more on the project, see:

http://www.theintelligencer.com/news/article/Students-design-heat-storage-system-10865688.php

Research roundup: New way to measure specific heat capacity; PCM underfloor heating; metal foams; more

Ben Welter - Tuesday, February 14, 2017

New proposed methodology for specific heat capacity determination of materials for thermal energy storage (TES) by DSC [Journal of Energy Storage]

Thermal diffusivity measurement of erythritol and numerical analysis of heat storage performance on a fin-type heat exchanger [Applied Thermal Engineering]

Benefits of PCM underfloor heating with PCM wallboards for space heating in winter [Applied Energy]

Non-steady experimental investigation on an integrated thermal management system for power battery with phase change materials [Energy Conversion and Management]

Experimental investigation on heat transfer characteristics during melting of a phase change material with dispersed TiO2 nanoparticles in a rectangular enclosure [International Journal of Heat and Mass Transfer]

Numerical method and model for calculating thermal storage time for an annular tube with phase change material [Journal of Central South Florida]

Stratified Laboratory Thermal Energy Storage (LabTES) Tank Experiments: Sensible Only and Sensible Augmented with PCM-Filled Tubes [University of Cincinnati master's thesis]

Development and optimization of PCM-based technology for cooling applications for improvement of fuel efficiency in commercial vehicle [SAE World Congress Experience]

Establishment and experimental verification of TRNSYS model for PCM floor coupled with solar water heating system [Energy and Buildings]

Thermal Performance Enhancement of Phase Change Materials (PCMs) by Using Metal Foams [Al-Nahrain Journal for Engineering Sciences]

Research roundup: Encapsulation techniques for inorganic PCM; effects of flake graphite nanoparticles; more

Ben Welter - Monday, February 13, 2017

From Renewable and Sustainable Energy Reviews:

A review on encapsulation techniques for inorganic phase change materials and the influence on their thermophysical properties
Phase equilibrium in the design of phase change materials for thermal energy storage: State-of-the-art

From Applied Thermal Engineering:

Investigating the impact of Cp-T values determined by DSC on the PCM-CFD Model
Performance of a Finned, Latent-Heat Storage System for Solar Thermal Power Application

From Applied Energy:

Impact of periodic flow reversal of heat transfer fluid on the melting and solidification processes in a latent heat shell and tube storage system
The effects of flake graphite nanoparticles, phase change material, and film cooling on the solar still performance
A quick-fix design of phase change material by particle blending and spherical agglomeration

From Journal of the Taiwan Institute of Chemical Engineers:

Phase-change heat transfer in a cavity heated from below: The effect of utilizing single or hybrid nanoparticles as additives

From Energy:

Field evaluation of microencapsulated phase change material slurry in ground source heat pump systems

From Renewable Energy:

Numerical studies on thermal and electrical performance of a fully wetted absorber PVT collector with PCM as a storage medium
Glass encapsulated phase change materials for high temperature thermal energy storage

From SAE World Congress Experience:

Integration and Validation of Thermal Energy Storage System for Electric Vehicle Cabin Heating

From Engineering Technology International Conference 2016:

Preparation and characterization of form-stable paraffin/polycaprolactone composites as phase change materials for thermal energy storage

Sunamp joins RAL Quality Association PCM

Ben Welter - Monday, February 13, 2017

Sunamp Ltd. of Scotland has joined the RAL Quality Association PCM, a European-based organization established in 2004 to develop standards for the phase change material industry. 

"Sunamp is delighted to join RAL PCM, the world's leading quality association for phase change materials," said Sunamp CEO Andrew Bissell. "We have extremely stable and long-lived, high energy density PCM that we deliver in high-power heat batteries. We look forward to working with RAL PCM and the other members to further develop PCM and Heat Battery standards, and to have our products certified."

RAL PCM has two key objectives: Promote the use of high-quality PCMs and influence the political landscape in the European Union in favor of PCMs. Other RAL members are Croda, BASF, Rubitherm, EMCO, va-Q-tec, PCM Technology, Global Energy Systems Europe, Sasol, Pluss Advanced Technologies and Entropy Solutions.

Sunamp is thinking big with commercial-scale heat battery

Ben Welter - Monday, February 06, 2017

Sunamp Ltd. continues to seek financing to fund development of its commercial-scale heat battery, the SunampCube. The device is designed to store energy generated by wind, solar and other renewable sources, as well as harvest excess heat generated by waste-treatment facilities.

Sunamp CEO Andrew BissellThe Scottish company is in negotiations to use the technology to transport waste heat by barge from the Avonmouth waste processing facility to Bristol for use in the district heating system under construction there. The batteries would be stored in 16 shipping container units, each holding 2 MWh of heat.

"We have built and tested a number of cells that will be used to build the full-scale device," says CEO Andrew Bissell. "Each one is a single cell storing 45-50 kWh."

What type of phase change material is being used?

"It's a salt hydrate ... our own tweak on sodium acetate trihydrate with both a nucleator and a stability enhancer," Bissell says. "58C melt and freeze points - almost no subcooling or hysteresis. And very cycle stable. We have cycled a test heat battery over 26,000 times with no loss of capacity or degradation in any metric."

Bissell says the company is working on financing for the project's next phase.

http://www.sunamp.com/products/sunampcube/