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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.

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PCM system inefficiencies blamed on design flaws, operator errors

Ben Welter - Monday, March 25, 2019

A PCM-based thermal energy storage system installed in an 11-story building at an Australian university used just 15 percent of its heat storage capacity to shift peak cooling load, according to researchers who monitored system performance for 25 months.

Morshed AlamA team led by Morshed Alam of Swinburne University of Technology in Hawthorn found that the PCM reduced chiller cooling load by 12 to 37 percent in winter but remained inactive in summer, partly because the ambient temperature was not cold enough to charge the PCM tank. The tank was designed to reduce the daytime cooling load on the chiller by 33 percent.

The results of the study are reported in "Energy saving performance assessment and lessons learned from the operation of an active phase change materials system in a multi-storey building in Melbourne," published in Applied Energy earlier this year.

"The factors that contributed to the underperformance of active PCM system," the researchers concluded, "include mismatch between designed and actual operation of the PCM system, inefficient operation logic of the system, poor material quality, and limited knowledge of maintenance staffs during the operation stage."

FlatICE PCM panels in TES tankThe TES system, installed in the 11th floor of Swinburne's Advanced Manufacturing and Design Centre, completed in 2015, was designed to minimize the daytime cooling load on the chiller and increase the building energy efficiency. The system includes a 5x4x2-meter tank filled with 5,120 FlatIce PCM panels made by PCM Products Ltd. Each HDPE panel is 500x250x45 mm and is filled with a salt hydrate PCM with the melting temperature of 13–15 °C. Water is used as the heat transfer fluid.

The researchers reported two problems with the PCM: a "very high degree of supercooling" that slowed the solidification process and a measured latent heat capacity (53 joules per gram) that was much lower than the manufacturer's specification (160 J/g).

Alam, a senior research fellow at Swinburne's Centre for Sustainable Infrastructure, Department of Civil and Construction, answered a few questions about the research in an email interview.

Q: This the first comprehensive report I've seen that analyzes the actual performance of a PCM/TES system in a commercial building. Do you know of others? For example, has the TES system at Melbourne CH2 undergone this kind of analysis?

A: "I am aware of the PCM system installed in CH2 building in Melbourne. But no such study was carried out to understand the performance of the system. The system went out of order within 5-6 years."

Q: Any theory on why the PCM's thermal storage capacity of 53 J/g, as measured using differential scanning calorimetry, did not match the manufacturer's specified capacity of 160 J/g?

A: "The DSC test is widely used by the researchers around the world to test PCM capacity. But it may not be an appropriate approach to test PCM thermal energy storage capacity. That is why we are now in the process of conducting an experimental study where 6 degree Celsius chilled water will be supplied in a small PCM tank. We will measure the flow rate, melting and solidification temperature and time required to completely solidify and melt the PCM. Based on the result we will optimize the system."

Q: Have the researchers' recommendations been put into practice?

A: "We are now working with our facilities department to put the recommendations in practice. We need to finish the optimization and cost-benefit analysis study. Then we can define the ideal operating condition of PCM in this building. We will be able integrate those maybe before next summer in Australia."

I shared results of the paper with Zafer Ure of PCM Products Ltd. and asked him to comment on the authors' observations on supercooling and specified-vs-measured latent heat capacity.

Zafer Ure"We have been supplying the same PCM for the last 20 years and many of the installations are 10~15 MWh levels," Ure wrote. "You cannot use the DSC machine to work out the latent heat for sulphate-based hydrated salts, it only picks up one of the chemicals in the mixture and gives you the data for that chemical. This is a well-known handicap for the DSC application for sulphate-based PCM testing. Moreover, DSC sample is less than gram quantities and this is a mixture of multiple salts, nucleating agent, stabilizers and thickening agent so if you do not pick up the correct mixture, which is very difficult unless you pick it up from the reactor vessel while you are making the PCM (i.e. while the agitators and mixers working at the correct temperature (some salts crystallize at room temperatures), you may not be able to pick up true sample.

"They took the sample out of one of the containers and no idea where and how they took the sample. If you do not have the true sample, especially lack of nucleating agent in the very small gram quantity sample, you can get it very wrong data as this is the case for their DSC. We would not ship any PCM unless QA release the goods and our records show the product supplied was within the standard capacity level. The actual latent heat can only be established using air test and actual freeze and melt profiles.

"If they managed to charge and discharge the tank fully they would have measured the tank performance which would have shown the true TES capacity. Sounds like their chilled water design and control did not allow that and therefore there is no way of evaluating the TES tank performance."

Research roundup: Micro/nano PCM for solar thermal applications; photovoltaic cooling; beeswax emulsions; more

Ben Welter - Thursday, March 21, 2019

From Renewable Energy:

Review on micro/nano phase change materials for solar thermal applications

From Jordan Journal of Mechanical and Industrial Engineering :

Photovoltaic Cooling Using Phase Change Material

From Advanced Materials Interfaces:

Phase Change Materials: Superhydrophobic Coatings from Beeswax‐in‐Water Emulsions with Latent Heat Storage Capability

From Energy Storage:

Experimental Observations on the Interface Front of Phase Change Material inside Cylindrical Cavity

From Applied Energy:

Effect of different dimensional carbon materials on the properties and application of phase change materials: A review

Research roundup: Poly (methyl methacrylate) shell; calcium carbonate shell; macroscopic composite cement mortars; more

Ben Welter - Tuesday, March 19, 2019

From Energy Procedia:

Development of microencapsulated phase change material with poly (methyl methacrylate) shell for thermal energy storage
Supercooling study of erythritol/EG composite phase change materials
Thermal performance of pouch Lithium-ion battery module cooled by phase change materials
Active cooling based battery thermal management using composite phase change materials
Investigation on Thermal Performance of an Integrated Phase Change Material Blind System for Double Skin Facade Buildings
Experimental study on preparation of a novel foamed cement with paraffin/ expanded graphite composite phase change thermal energy storage material

From Colloids and Surfaces A: Physicochemical and Engineering Aspects:

Synthesis and performance evaluation of paraffin microcapsules with calcium carbonate shell modulated by different anionic surfactants for thermal energy storage

From Journal of Materials Chemistry A:

A novel shape-stabilization strategy for phase change thermal energy storage

From Journal of Molecular Liquids:

Melting of phase change materials in a trapezoidal cavity: Orientation and nanoparticles effects

From Energy and Buildings:

Development of new nano-enhanced phase change materials (NEPCM) to improve energy efficiency in buildings: lab-scale characterization

From Applied Sciences:

Efficient Characterization of Macroscopic Composite Cement Mortars with Various Contents of Phase Change Material

From Solar Energy:

Modelling and performance analysis of a new concept of integral collector storage (ICS) with phase change material

Research roundup: Personal cooling system; optimization of active wall system; cement mortar; asphalt pavement; more

Ben Welter - Friday, March 15, 2019

From International Journal of Refrigeration:

Experimental study of enhanced PCM exchangers applied in a thermal energy storage system for personal cooling

JMR illustration of microencapsulated n-octadecane with silk From Journal of Materials Research:

Fabrication and characterization of microencapsulated n-octadecane with silk fibroin–silver nanoparticles shell for thermal regulation

From IOP Conference Series: Earth and Environmental Sciences:

Simple Thermal Energy Storage Tank for Improving the Energy Efficiency of an Existing Air-conditioning System
An optimization study into thermally activated wall system with latent heat thermal energy storage
Simulation of operation performance of a solar assisted ground heat pump system with phase change thermal storage for heating in a rural building in Xi'an
Experimental Study on the Demand Shifting Effects of PCM Integrated Air-Conditioning Duct

From International Journal of Energy Research:

Efficiency optimisation of the thermal energy storage unit in the form of the ceiling panel for summer conditions

From Materials Research Express:

Experimental study on thermal conductivity of composite phase change material of fatty acid and paraffin

From Energies:

Design Optimization of a Hybrid Steam-PCM Thermal Energy Storage for Industrial Applications

From Construction and Building Materials:

Analysis of thermoregulation indices on microencapsulated phase change materials for asphalt pavement

From Applied Thermal Engineering:

Experimental and numerical characterization of an impure phase change material using a thermal lattice Boltzmann method

From Energy Conversion and Management:

Experimental and numerical study of a vertical earth-to-air heat exchanger system integrated with annular phase change material

From Materials:

Thermal and Structural Characterization of Geopolymer-Coated Polyurethane Foam—Phase Change Material Capsules/Geopolymer Concrete Composites

From Applied Sciences:

Microstructure and Mechanical Properties of Cement Mortar Containing Phase Change Materials

PCM briefing: 2-day training school in Barcelona; Alexium to launch foam bedding, 'top of bed' products

Ben Welter - Friday, March 15, 2019

A training school on thermal energy storage material selection, optimization and characterization will be offered May 20-21 at the University of Barcelona. The university's Center for Design and Optimization of Processes and Materials is hosting the event. The fee is 230 euros. Lecturers include Camila Barreneche, Ana Inés Fernández, Mercè Segarra and Pablo Gamallo of the University of Barcelona; Luisa Cabeza and Alvaro de Gracia of the University of Lleida, Spain; and Yulong Ding of the University of Birmingham, United Kingdom.

Alexium International Group Ltd. was among the companies making presentations this week at the Gabelli & Company Specialty Chemicals Conference in New York City. Alexium, based in Greer, S.C., and Perth, Australia, makes flame-retardant and PCM-enhanced fabric treatments. Among its "cornerstone" initiatives is a plan to launch a new product line in early 2019, Alexicool FM, the application of the company's Alexicool technology to foam mattress and "top of bed" products.  

• Thermal materials specialist va-Q-tec reports that its annual revenue grew by 8 percent in 2018. The company, based in Würzburg, Germany, said sales from its products business, including vacuum insulation panels and phase change materials, increased by 12 percent to 20.1 million euros, up from 18 million euros in 2017. However, its earnings fell by 58 percent, to 3 million euros. It blamed earnings decrease on investment costs and a rise in sales from its lower-margin products business.

• Australian researchers are challenging the belief that 22° C (72° F) is the optimum temperature to maintain worker productivity. A team from Griffith University’s School of Engineering and Built Environment and Cities Research Institute performed an extensive review of research literature on the relation of moderate thermal environment to cognitive performance. "From the research point of view," the lead researcher, Fan Zhang, said in an interview with the Cooling Post, "there is no empirical evidence that this temperature [22ºC] should be maintained. In effect, it is inconsistent with the already-established comfort benchmarks such as ASHRAE 55-2017, which recommends a summer time thermal comfort zone of 23-26ºC. I would say 23-26 is a safe summer temperature set point range for western developed countries."

Research roundup: Radiant floor heating system; mitigation of supercooling; hot water stratification; more

Ben Welter - Friday, March 08, 2019

From Energies:

Analysis of Thermal Performance and Energy Saving Potential by PCM Radiant Floor Heating System based on Wet Construction Method and Hot Water

From Applied Energy:

Supercooling of phase-change materials and the techniques used to mitigate the phenomenon

From Polymer Chemistry:

Encapsulating an organic phase change material within emulsion-templated poly(urethane urea)s

From AIP Advances:

Thermal expansion effects on the one-dimensional liquid-solid phase transition in high temperature phase change materials

From Journal of Materials Chemistry A:

A thermal energy storage composite with sensing function and its thermal conductivity and thermal effusivity enhancement

From Materials Science and Engineering:

Experimental Measurements of Hot Water Stratification in a Heat Storage Tank

From Thermochimica Acta:

Modification of physical and thermal characteristics of stearic acid as a phase change materials using TiO2-nanoparticles

From Energy and Buildings:

Thermal and Structural Performance of Geopolymer Concrete Containing Phase Change Material Encapsulated in Expanded Clay
An experimental study on applying organic PCMs to gypsum-cement board for improving thermal performance of buildings in different climates

From International Journal of Biological Macromolecules:

Sodium alginate/feather keratin-g-allyloxy polyethylene glycol composite phase change fiber

From Construction and Building Materials:

Thermal properties of lightweight concrete incorporating high contents of phase change materials

From Progress in Organic Coatings:

Fabrication and characterization of microencapsulated n-heptadecane with graphene/starch composite shell for thermal energy storage

From Sustainable Energy and Fuels:

A thermal energy storage prototype using sodium magnesium hydride

From Thermal Science and Engineering Progress:

Experimental investigation of the thermal performance of a helical coil latent heat thermal energy storage for solar energy applications

From International Journal of Sports Physiology and Performance:

Exploring the Efficacy of a Safe Cryotherapy Alternative: Physiological Temperature Changes from Cold Water Immersion vs Prolonged Phase Change Material Cooling

From Applied Sciences:

A Form Stable Composite Phase Change Material for Thermal Energy Storage Applications over 700° C

PCM briefing: Energy Storage Europe includes sessions on thermal storage; C-Therm offers webinar on thermal performance of textiles

Ben Welter - Monday, March 04, 2019

• The Energy Storage Europe conference and trade fair, set for March 12-14 in Dusseldorf, Germany, includes a number of sessions on thermal energy storage: "Heat Storage - an essential contribution to energy transition," Oliver Baudson, TSK Flagsol Engineering GmbH; "Advanced Thermal Energy Storage Concepts," Dr. Robert Pitz-Paal, DLR Institute of Solar Research; "High Temperature Storage," Doron Brenmiller, Brenmiller Energy; "Material and Component Development for Thermal Energy Storage," Christoph Rathgeber, ZAE Bayern; and "Thermal Energy Storage for Cost-Effective Energy Management & CO2 Mitigation," Dr. Dan Bauer, German Aerospace Center - DLR e.V.

• The deadline for submitting paper proposals for next fall's Advanced Building Skins conference in Bern, Switzerland, is March 10. The list of topics includes thermal performance of phase change materials.

• Thermal battery maker Sunamp Ltd.'s collaboration with the University of Edinburgh’s School of Chemistry won the "Powerful Partnership" award at the Scottish Knowledge Exchange Awards 2019 last month. The organizations began work on the development of new phase change materials in 2010. 

• Croda International Plc has been recognized for its commitment to "a deforestation-free supply chain." Croda earned an A- in that category in CDP's climate change report for 2018, up from a B the previous year. The specialty chemical company says it has a special focus on palm oil and is committed to supplying RSPO-certified palm oil derivatives. 

• Thermal instrumentation maker C-Therm Technologies Ltd. is hosting a free webinar this week, "Quantifying Thermal Performance of Textiles (Warm Feel / Cool Touch)." The webinar, aimed at "anyone working in the product performance testing of textiles and fabrics where temperature regulation is an important function," will be held at 1 p.m. EST Wednesday.

Research roundup: PCM wallboard; cement mortars; electric load shifting; red-mud geopolymer composite; more

Ben Welter - Wednesday, February 27, 2019

From Renewable Energy:

Phase Change Material Wallboard (PCMW) melting temperature optimisation for passive indoor temperature control

From Cement and Concrete Research:

Multiphysics analysis of effects of encapsulated phase change materials (PCMs) in cement mortars

From Journal of Molecular Liquids:

Preparation and characterization of sodium sulfate pentahydrate/sodium pyrophosphate composite phase change energy storage materials

From Energy and Buildings:

Performance of heat pump integrated phase change material thermal storage for electric load shifting in building demand side management
Indoor thermal comfort assessment using PCM based storage system integrated with ceiling fan ventilation: Experimental design and response surface approach

From International Journal of Photoenergy:

Experimental Study on the Performance of a Phase Change Slurry-Based Heat Pipe Solar Photovoltaic/Thermal Cogeneration System

From Solar Energy:

Effects of sodium nitrate concentration on thermophysical properties of solar salts and on the thermal energy storage cost
Red-mud geopolymer composite encapsulated phase change material for thermal comfort in built-sector [pdf]

From Energies:

A Novel Encapsulation Method for Phase Change Materials with a AgBr Shell as a Thermal Energy Storage Material

From Advanced Composites and Hybrid Materials:

Latent heat and thermal conductivity enhancements in polyethylene glycol/polyethylene glycol-grafted graphene oxide composites

From International Journal of Refrigeration:

Preparation and performance of form-stable TBAB hydrate/SiO2 composite PCM for cold energy storage

From Solar Energy Materials and Solar Cells:

Delignified wood/capric acid-palmitic acid mixture stable-form phase change material for thermal storage
Molten salt corrosion mechanisms of nitrate based thermal energy storage materials for concentrated solar power plants: A review

From Buildings:

Thermal Performance of Hollow-Core Slab Ventilation System with Macro-Encapsulated Phase-Change Materials in Supply Air Duct

From International Journal of Heat and Mass Transfer:

Heat transfer performance of the finned nano-enhanced phase change material system under the inclination influence

From Journal of the Electrochemical Society:

Effect of High Temperature Circumstance on Lithium-Ion Battery and the Application of Phase Change Material

From Energy:

High-temperature PCM-based thermal energy storage for industrial furnaces installed in energy-intensive industries

PCM mats helped lift Virginia Tech to first place in Solar Decathlon

Ben Welter - Monday, February 18, 2019

FutureHAUS, front elevation

The Virginia Tech team that won first place in the 2018 Solar Decathlon Middle East credits a good share of its success to the deft use of phase change material donated by Insolcorp LLC of New London, N.C.

FutureHAUS, the lone U.S. entry, topped 13 other finalists and more than 60 total entrants in the competition organized by the U.S. Department of Energy and the United Arab Emirates’ Dubai Electricity & Water Authority. Australia's University of Wollongong finished second. The finals took place in November in the desert heat of Dubai.

Insolcorp donated 400 square feet of two types of Infinite R PCM mats. Both are salt hydrates, one with a melt point of 21 degrees Celsius, the other a melt point of 22 degrees C. The phase change material acts as a thermal battery, absorbing and releasing thermal energy as it solidifies and melts.

The Virginia Tech team deployed the mats in the plenum of its 900-square-foot solar-powered house. The PCM allowed the team to take advantage of a rule that limited the use of solar energy to 8kw at any one time, with one exception: Unlimited use of solar energy for air conditioning was allowed during daily inspection periods to assure visitor comfort. The PCM mats, solidified during those periods, helped keep the house comfortable at other times. That helped the FutureHAUS achieve the highest score in net energy use, a key metric in the competition.

Joseph Wheeler, AIA"Every team struggled with the 8kw limit," said Joseph Wheeler, right, lead faculty on FutureHAUS and co-director of Virginia Tech's Center for Design Research. "Typically, during peak energy, you would be generating lots and lots of power, which you could easily charge your batteries with, which you could easily run all your tasks, and you could feed the grid, and build up quite a bit of surplus so that you would remain energy positive throughout the two weeks of competition.

"But, since they limited inverter use at any one time to 8kw, it really put a limit to what our energy budget was. We saw phase change as batteries. A massive ton of batteries. ... It's more of a strategy for a competition than it is for a realized situation. But in a realized situation, we know the value of the PCM. Heat energy, cost of power being cheaper at night than during the day where you can charge your systems and load shift. Practically, PCMs make a lot of sense. And we wanted to have the PCMs in this house for practical reasons, not just for competition reasons. ...

"In simple terms, we eased the demand for the HVAC every afternoon. It was the hottest time of the day and it was also the time when we were getting less power from the solar panels because the sun was moving down. It was a critical time because we knew that once the sun went down, we had to survive on battery. And we had a limit. They limited every house to 15kw of battery."

FutureHAUS, kitchenThe FutureHAUS team finished in the top three in eight of the competition's 10 categories: first place in Architecture, House Functioning and Sustainable Transportation; second place in Sustainability and Innovation; and third place in Engineering/Construction, Energy Efficiency and Comfort Conditions.

The FutureHAUS entry was a two-year university-wide effort. More than 100 Virginia Tech students helped design and build the structure, with help from faculty members in architecture, urban studies, science, engineering and other departments.

The house consists of 18 modular  "cartridges" built inside a Virginia Tech research facility. It was first assembled on campus in Blacksburg, Va., last summer. After testing, it was disassembled, shipped to Dubai and then reassembled at the competition site in just two days. It has since been shipped back to Blacksburg, where it will undergo testing to measure its various energy-saving components.

"We now have a system in place where we can collect data and can truly test the performance," Wheeler said. "We know the PCM worked for us during the competition because we did have some temperature sensors in the ceiling. And so we were able to prove that we were reaching the pre-state when those PCMs were being charged. But we really want to collect a lot more data and look at it in real-world situations."

PCM briefing: PureTemp joins RSPO; Reda's new PCM fabric on display in Milan

Ben Welter - Monday, February 18, 2019

PureTemp LLC has joined the Roundtable for Sustainable Palm Oil as an associate member. The nonprofit organization, which has more than 4,000 members worldwide, promotes the growth and use of sustainable oil palm products. In November, RSPO adopted stricter standards for certified sustainable palm oil, including a total ban on deforestation by its members.

Reda Group's new Active Phase temperature-control fabric was on display at the Milan fabric trade show earlier this month. The material uses phase change material to keep body temperature constant when ambient temperature fluctuates. Reda says the material features enhanced breathability and softness and is "easy to clean, even in water."

University of Maryland fabric•  University of Maryland researchers have created a temperature-control fabric that does not rely on phase change material. The fabric changes its insulating properties in response to the environment. In warm and humid conditions, the fabric allows radiant heat to pass through. When conditions become cooler and drier, the fabric reduces the heat that escapes. Two types of synthetic materials in the fabric — one that absorbs water and another other that repels it — are coated with carbon nanotubes. The fibers warp and relax in response to changing humidity, opening and closing pores in the fabric. 

• In interviews with Advanced Textiles Source, four entrepreneurs were asked: What do you wish you had known early on when you were first dealing with intellectual property law and patent issues? “Get feedback on why you need a patent,” said Jeremy Wall, founder and CEO of smart-clothing startup Lumenus. “Where else could you spend $20,000?” Said Matt Kolmes, CEO of VOLT Smart Yarns: “Even if you are on a tight budget, file that Provisional application immediately before you show your idea to anyone, or talk about it with anyone."

• The Marie Sklodowska-Curie Action program is seeking applicants for a one- to two-year research fellowship at the Oslo Metropolitan University. The European Union-funded fellowship will focus on the energy-performance aspects of phase change material in buildings. "In this collaboration," OsloMet says, "we intend to gain our understanding and explore about the micro-structural aspect to relate the macro-scale behavior at continuum level." The application deadline is March 7.