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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, foam insulation combine to reduce heat transfer through walls

Ben Welter - Monday, December 12, 2016

Researchers at the Fraunhofer Institute for Chemical Technology in Germany say they have successfully integrated phase change material in foam insulation for use in walls.

What's new about the technology?

"Instead of a few micrograms, several grams of the phase change materials have been integrated. Therefore the thickness of the wall is not changing by increasing the thermal mass," says Sandra Pappert, a scientist at Fraunhofer.

Details of the research will be presented at the BAU trade fair in Munich, Jan. 16-21, 2017. Researchers will use two climatic chambers to demonstrate the extent to which the foam sheets can help manage temperature fluctuations in buildings.

Patent application: HVAC system for electric vehicle with driving range extension

Ben Welter - Thursday, September 01, 2016

U.S. patent application 20160250906 (applicant Mahle International GmbH, Stuttgart, Germany):

"A heat pump cooling and heating system for an electric vehicle includes a range extending PCM heat exchanger, with a single acting phase change material with a melt temperature between the two comfort temperatures associated with cooling and heating, respectively. In a charging mode, as the vehicle batteries are charged, the same exterior current source runs the compressor, charging the PCM exchanger with heat or 'cold.' During an initial range extending mode, the PCM exchanger/reservoir serves as the heat source or heat sink. The PCM material does not directly heat or cool the air, as is conventional, allowing a single reservoir material to be used in both heating and cooling modes."

PCM briefing: EU research focuses on energy retrofits; Axiom Exergy raises $2.5 million

Ben Welter - Tuesday, August 02, 2016

• A European Union research project focused on retrofitting old buildings to meet EU efficiency standards is taking a close look at PCMs built into walls. “By using a phase change material which freezes at 18°C and melts at 25°C,” says Dr. Jürgen Frick, project coordinator, “we can regulate the temperature fluctuations of a room. If the temperature falls to 18°C, the PCM freezes and heats the room. When it rises to 25°, the PCM melts, energy is absorbed, and the room is cooled.”

Rally by Diamond Mattress• The latest entry in the bed-in-a-box mattress competition features open-cell foam infused with copper gel and phase change material to regulate temperature. Diamond Mattress of Rancho Dominguez, Calif., says the company's new Rally line will be sold online and in retail stores.

Eric Buchanan of the West Central Research and Outreach Center in Morris, Minn., has posted an update on his net-zero dairy project. The system's key components so far include solar thermal panels, a heat pump, three heat exchangers and a 2,000-gallon water tank. Fifty-four kilowatts of solar PV and two 10-kW wind turbines are now being added to the system.

Axiom Exergy has raised $2.5 million from investors to help bring its refrigeration battery to supermarkets and cold storage facilities across the United States. The system uses a salt-based phase change material to reduce peak power usage by up to 40 percent and provide backup cooling during power outages.

• The University of Birmingham's Birmingham Centre for Energy Storage is setting up a joint lab on energy storage research with Global Energy Interconnection Research Institute Europe, an organization founded by China's state-run utility. The lab will focus on thermal and cryogenic energy storage systems and their application in energy networks.

• New from Accuray Research: "Global Advanced Phase Change Material (PCM) Market Analysis & Trends - Industry Forecast to 2025"

• A research team at Camosun College in Victoria, British Columbia, has selected PureTemp phase change material for use in a study of greenhouse thermal storage systems. "One of the engineering students is focusing on designing racks for the PCM bottles that will be specifically engineered to slow release and speed recharge of the bottles," writes Becky Mason, an instructor at Camosun who helped organize the research project. "This is intended to optimize use of PCM in off-grid greenhouses where electric fans are not used to circulate air around the PCM."

Research roundup: Refrigerated display cabinet; MA/HDPE composites with nano-additives; incinerator ash; more

Ben Welter - Sunday, July 31, 2016

The novel use of phase change materials in an open type refrigerated display cabinet: A theoretical investigation [Applied Energy]

Reducing cell-to-cell spacing for large-format lithium ion battery modules with aluminum or PCM heat sinks under failure conditions [Applied Energy]

Synthesis and thermal properties of the MA/HDPE composites with nano-additives as form-stable PCM with improved thermal conductivity [Applied Energy]

An experimental study of thermal management system using copper mesh-enhanced composite phase change materials for power battery pack [Energy]

Novel Multiphase Change Materials for Energy Storage Application in Buildings [14th International Energy Conversion Engineering Conference, Propulsion and Energy Forum]

MSWI bottom ash for thermal energy storage: An innovative and sustainable approach for its reutilization [Renewable Energy]

Response surface method optimization of V-shaped fin assisted latent heat thermal energy storage system during discharging process [Alexandria Engineering Journal]

Entropy Solutions develops shape-stabilized versions of 2 PureTemp PCMs

Ben Welter - Wednesday, July 13, 2016

Entropy Solutions has developed shape-stabilized versions of two of its PureTemp biobased phase change materials. These "gelled" PCMs maintain their shape even as the PCM cycles between solid and liquid form, absorbing, storing and releasing thermal energy as needed in temperature-control applications. Potential uses include building materials, underfloor electric heating systems and shipping containers.

Shape-stabilized PureTemp 4The gelled PureTemp 4, right, has a latent heat of 159.4 joules per gram, a melt point of 4.81º Celsius and a freeze point of 1.07º Celsius. The gelled PureTemp 20 has a latent heat of 149.3 J/g, a melt point of 21.39º C and a freeze point of 16.85º C. The addition of polymers accounts for the observed reductions in latent heat compared to the ungelled versions.

The gelled forms ensure even distribution of PCMs contained in thin films. The PCM does not leak from the polymer matrix after thermal cycling. Other properties of these lab-scale versions include:

• Moldable
• Narrow melting range
• Soft when the PCM is in the liquid state
• Stiff/hard when the PCM is in the solid state
• Minimized leakage if enclosing film is punctured

Entropy Solutions is exploring scale-up and commercialization options for the new material.

2016 Presidential Green Chemistry Challenge Award winners named

Ben Welter - Thursday, June 23, 2016

Verdezyne of Carlsbad, Calif., which developed a greener way to make high-performance nylon, is among this year's Presidential Green Chemistry Challenge Award winners. Verdezyne's process uses a plant-based feedstock and does not employ high temperatures or concentrated nitric acid. The nylon is used in hairbrushes, toothbrushes, adhesives, coatings, fragrances and other products. It has qualified for the USDA Certified Biobased label.

The U.S. Environmental Protection Agency award recognizes innovative technologies "that turn climate risk and other environmental problems into business opportunities, spurring innovation and economic development." The awards were present last week at the annual Green Chemistry & Engineering Conference in Portland, Ore. This year's other winners:

• Professor Paul Chirik of Princeton University discovered a new class of catalysts to produce silicones without the use of platinum.

Newlight Technologies of Costa Mesa, Calif., developed a plastic made from methane-based greenhouse gas. 

• Texas-based CB&I and Albemarle Corp. of Baton Rouge, La., developed and commercialized a safer technology to produce alkylate, a clean gasoline component.

Dow AgroSciences of Indianapolis developed and commercialized Instinct, an additive that reduces the leaching of fertilizer nitrate into ground and surface waters. 

Dr. William R. Sutterlin, Entropy Solutions' chief science officer, was a member of a University of Missouri team that won the academic award in 2006 for developing an inexpensive method to convert waste glycerin, a byproduct of biodiesel fuel production, into propylene glycol.

PCM briefing: U.S. companies flock to renewables; molten salts could transform mining process

Ben Welter - Wednesday, June 22, 2016

• Seventy-two percent of U.S.-based companies surveyed by PwC said they are actively pursuing renewable energy procurement, mainly wind and solar. 

• The University of South Australia has teamed up with Centrex Metals Limited to conduct research on higher-temperature molten salt. Centrex hopes to use the technology, which heats molten salt to 850º Celsius and higher, to convert potassium feldspar ore to potassium chloride fertilizer, using less water and energy than current processes.

• The American Chemistry Council says Toxic Substances Control Act, signed into law Wednesday by President Obama, will have "a meaningful impact on the economy and the marketplace." Up next: The Environmental Protection Agency begins work on implementing new rules

• In a guest blog post for Energy Storage News, Sunamp's business development manager writes about demonstrating the company's PCM/PV "heat battery" in Shenzhen, China, last month. Maurizio Zaglio says SunampPV is a great fit for the Chinese market, thanks to government incentives that have led to widespread use of PV panels. 

Erythritol tested in prototype of EV cabin-heating system

Ben Welter - Tuesday, June 14, 2016

A recent post on MAHLE's development of a heat exchanger designed to increase the driving range of electric vehicles in cold weather drew the attention of Luc Traonvouez, a French design engineer and owner of Insula France. In 2013, he worked with RBL Plastiques on a similar project. He contacted me via LinkedIn and offered to share the unpublished details of his work.

Insula France EV heater prototypeTraonvouez’s demonstration unit uses erythritol, a phase change material with a melting point of 118° Celsius and a latent heat value of 340 joules per gram. As with the MAHLE system, the PCM is melted while the vehicle battery is charged, using electricity from the grid. The stored heat is released as the PCM solidifies during driving.

The prototype weighs 15.7 kilograms, of which 22 percent is erythritol. The PCM is stored in a rectangular aluminum container with large fins inside and out. The interior fins drive the heat out of the PCM to the aluminum container; the exterior fins transfer the heat to air. The finned assembly is placed inside a thermally insulated envelope. The insulation provides enough resistance to maintain the heat for several hours. An electric fan moves air over the fins and pushes it into the vehicle’s cabin on demand.

Erythritol is relatively cheap and shows little supercooling, according to Traonvouez. But he notes two major problems with the material:

“1. The volume change between solid and liquid states is roughly 10%, and when cooling happens the PCM crystalizes around the fins, with a void between the fins and in some areas a void between the PCM and the fins; this means that after a peak of power when releasing heat from the storage, there is a fast drop. As the need for heating is much higher when starting the cold car than in stabilized mode, this drop is less a problem as it would be if we had needed a constant output.

“2. This PCM is subject to fast degradation when over heated in air; so the best is to cap heating at 140°C and confine the PCM in an airproof volume from which oxygen has been removed. When using a PCM with 10% volume size, we cannot fill the macroencapsulation completely with liquid PCM, but rather leave a significant empty volume and put it under some vacuum before sealing.”

This chart shows the heat output of the demonstration unit over a 54-minute period:

Traonvouez concludes: “The demonstration unit must be improved, one way being for example to use another way than fins in the PCM to improve its global thermal conductivity. However, the result is interesting and can be industrialized once tested extensively and over a high number of extreme cycles.”

PCM 2016 conference papers available for download

Ben Welter - Wednesday, May 25, 2016

The International Institute of Refrigeration has posted more than two dozen papers presented at the PCM 2016 conference in Karlsruhe, Germany, earlier this month. The downloads are available for 15 euros each. A few highlights:

Passive cooling potential of two different PCM cooling ceilings in the energy efficiency center, (H. Weinlader, F. Klinker, M. Yasin)

"In the Energy Efficiency Center – the new R&D building of the ZAE Bayern - two different PCM cooling ceiling types are installed and monitored in two office rooms. The ceilings are connected to a water circuit and can be used for heating or cooling. The PCM ceilings are prototypes which differ in the positioning of the PCM layer: ceiling type 1 with the PCM on top of and ceiling type 2 with the PCM below the water pipes. It was found, that cooling ceiling type 2 had a better thermal connection between PCM and room, nevertheless, the passive cooling power of the two different system designs was quite similar when measured as a function of the room globe temperature."

Experimental analysis on a novel air heat exchanger containing PCM in a cold room, (B. Copertaro, R. Fioretti, P. Principi)

"An air heat exchanger consisting of aluminium containers with finned surface filled with PCM (5 °C melting temperature) was located near the evaporator of a cold room. The aims are to reduce cooling energy consumption and improving the maintenance thermal conditions of stored products. For this purpose, an experimental campaign was carried out and a monitoring system was developed. The cold room thermal behaviour, with and without PCM, was studied under steady state operating conditions. As expected a reduced number of on/off compressor cycles (6 cycles instead 13 cycles) in the PCM added cold room was observed. Test results showed that by storing PCM in the air heat exchanger, up to 16% of energy saving can be achieved."

Standardization of PCM characterization via DSC, (S. Gschwander, T. Haussmann, G. Hagelstein)

"This work investigates the influence of particle size on crystallization behaviour of microencapsulated and emulsified n-octadecane using differential scanning calorimetry (DSC) and laser diffraction. Analyses of microcapsules show a stepwise decrease of nucleation temperature (from 26 °C to 14 °C) with decreasing particle size (from 300 μm to 3 μm). Further reduction of particle size in emulsions (< 0.2 μm) results in a slight decrease of nucleation temperature (<2 °K)."

Potential use of phase change materials in a display cabinet: development of a dynamic modeling approach, (H.M. Hoang, F. Raoult, D. Leducq)

"Different configurations (position of the PCM in the equipment) are simulated and discussed: after the evaporator and under shelf. At first, the modelling of a display cabinet in a transient state is developed based on a simplified heat transfer model using zonal approach. By combining it with a melting and freezing process of PCM units located inside the display cabinet, the effects of the PCM addition on air and food temperatures are simulated. Placing the PCM under shelves allows maintaining the product temperature during defrosting or electricity shortage."

A case study on the application of phase-change materials in buildings, (A. Hantsch)

"Energy storages employing the phase-change enthalpy of some material yield much larger energy densities than specific-heat-based systems. This case study is about the effect of phase-change materials on the heat and cooling load and annual energy demand for various scenarios. By means of a TRNSYS model it is possible to carry out energetic annual simulations. The results of this contribution allow giving advice for the design of new systems."

Experimentation for the evaluation of aluminum foams for improving heat transfer in PCM thermal storages, (R. Lazzarin, S. Mancin, M. Noro)

"This work investigates the use of Aluminum foams as heat transfer medium to improve the overall heat transfer of paraffin waxes that can be possible PCMs to be implemented in hybrid sensible-latent water TESs. The design of a new experimental testing rig is here presented together with some preliminary simulation results obtained during the phase change process of paraffin waxes with melting temperatures around 45 °C, with and without metal foams, in a water thermal storage unit." 

Latent heat storage with polyethylene enhanced with aluminum stripes, (T. Ozcan, E. Gukelberger, M. Kauffeld)

"Using a built prototype latent heat storage integrated into a solar air conditioning system at the Institute of Refrigeration, Air Conditioning, and Environmental Engineering’s test facility loading and discharging tests were conducted to investigate the use of PCM materials in a heat exchanger of a solar system to support steam production in cloudy periods. The latent heat storage concept is designed for the temperature range to 130 °C."

Comparison of a single stage and a multistage latent heat storage for domestic hot water delivery, (J. Diriken, J. van Bael, F. Leemans)

"In this paper we assess the potential to use multiple PCM in combination with a compact heat exchanger for direct domestic hot water delivery purposes for e.g. district heating substations. The results of the measurements on a compact thermal energy storage device based on multiple phase change materials with different melting temperatures are compared to a geometrical identical system with a single PCM with one melting temperature." 

For a full list of papers, go to Type Karlsruhe in the first search box, check "Conference papers" and type 2016 in the box next to "Year."

PCM-based system heats electric vehicle without draining battery

Ben Welter - Tuesday, May 17, 2016

MAHLE PCM HX diagramCold climates pose a challenge for electric vehicles: With no engine to serve as a heat source, EVs rely on batteries alone to warm the cabin and defrost the windshield. Running the heater quickly drains batteries and can reduce driving range by as much as 60 percent. That can make a routine commute a frosty and mitten-biting affair in places like International Falls, Minn., where temperatures dip well below freezing on a typical January morning.

Using phase change material developed by Entropy Solutions, engineers at MAHLE, one of the world’s largest automotive suppliers, found a solution. They have developed a prototype of a thermal energy storage system that is expected to extend the range of EVs by 20 to 40 percent in cold conditions.

PCMs are substances that absorb and release thermal energy during the process of melting and freezing. The MAHLE system uses a PCM’s stored latent heat to provide cabin heating. The PCM is melted while the vehicle battery is charged from the electrical grid. The stored heat is transferred to the cabin as the PCM solidifies during driving. The system provides enough thermal energy to heat the cabin for about 46 minutes, the typical daily commute time for American drivers.

At the heart of the electrical PCM-assisted thermal heating system (ePATHS) is a high-efficiency PCM heat exchanger. Because heat transfer is a critical factor in system performance, MAHLE engineers chose a two-pass flow exchanger with a number of rectangular tube rows sandwiched between stacks of finned PCM chambers. An electric pump runs a water-glycol mixture through the PCM heat exchanger, absorbing heat from the PCM and flowing to a heater under the dashboard.

The design is similar to that of a standard automobile radiator, but with a fully enclosed PCM containment shell. The heat transfer fluid flows through channels in direct contact with the PCM chambers. The exchanger is enclosed in a high-performance vacuum insulation panel to minimize heat loss.

Entropy Solutions of Plymouth, Minn., developed two novel bio-based phase change materials to match the needs of the new system. The PCM chosen, DPT83, has a melting point of 83° C (181° F) and a latent heat value of 348 joules per gram. DPT83’s relatively high latent heat capacity, well above the 200 J/g of older PCMs, helps minimize system size and weight. The 33-kilogram, 31-liter prototype includes 19 kg of phase change material.

Entropy researchers were able to synthesize the DPT83 beginning with natural vegetable-based feedstocks. They found that the PCM is compatible with aluminum and are conducting additional compatibility studies.

“Most organic based PCMs have latent heats of around 150 to 210 joules per gram,” said Dr. William R. Sutterlin, Entropy’s chief science officer. “Water has a latent heat of around 330 joules per gram. I had always wondered if we could make an organic PCM that could beat water. We did it.”

The $3.5 million, three-year collaborative research project, with 50 percent funding from the U.S. Department of Energy, is detailed in two technical papers published in April by SAE International, “Design and Testing of a Thermal Storage System for Electric Vehicle Cabin Heating” and “Thermal Storage System for Electric Vehicle Cabin Heating - Component and System Analysis.”

"The PCM-based thermal storage system provides a commercially viable technology to mitigate range anxiety of electric vehicles in the marketplace. We are working closely with vehicle OEMs to commercialize the technology in the near future," said Tim Craig, MAHLE's U.S. Advanced HVAC System manager.