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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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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 He contacted me via LinkedIn and offered to share the unpublished details of his work.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 http://www.iifiir.org/ClientBookline/toolkit/p_requests/formulaire.asp?GRILLE=IIFRRECHFRIDOC&PORTAL_ID=portal_model_instance__fridoc_search.xml. 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.

PCM briefing: Free webinar on industry disruption; how ice-making bacteria works

Ben Welter - Friday, May 13, 2016

Marija Jović, project manager and lead scientist at PreScouter Inc., will lead a webinar titled "How Phase Change Materials Are Disrupting Your Industry." The free event, set for 1-2 p.m. CDT on June 9, is aimed at leaders in a range of industries, from textiles and apparel to medicine and robotics. Illinois-based PreScouter provides corporate leaders with data and insights on which to base product development decisions.

Pharmaceutical Commerce's annual Cold Chain Sourcebook projects 52 percent growth in global cold chain market between 2014 and 2020.

Ben Singleton, business development manager at Pelican BioThermal, will be among the speakers at next week's Cold Chain & Product Handling: Temperature Controlled Logistics conference in Amsterdam. 

• Since the late 1980s, a company called Snowmax has supplied ski resorts with a bacteria-derived additive that makes snow production possible at higher temperatures. Researchers at the Max Planck Institute for Polymer Research in Mainz, Germany, now say they've figured out how the ice-making bacteria works.  

Roccor to develop flexible PCM panels for miniature satellites

Ben Welter - Friday, April 29, 2016

A proposal by Roccor LLC of Louisville, Colo., to develop lightweight, flexible thermal energy management panels for CubeSats and other small satellites is one of 399 projects selected by NASA this week to support future missions into deep space. The thermal panels incorporate paraffin phase change material inside a metal case with an internal metal woven mesh to protect the electronics aboard miniaturized satellites.

Roccor's proposal describes the potential applications:

"The primary NASA target application for the proposed space-rated PCM panel technology is future NASA CubeSat and SmallSat spacecraft for which thermal control of on-board electronics is a major bottleneck in the system design. In particular, the proposed technology will enable efficient thermal control by maintaining a constant temperature heat sink or heat source for a range of electronic components in rapidly changing thermal environments. The PCM panel is being designed as a lightweight and flexible component, yet having high thermal capacity, requiring less mass and volume than currently used carbon-fiber and aluminum honeycomb composite panels."

Two other Roccor proposals were approved for Phase I development. Each will receive six-month contracts valued at up to $125,000. Watch the video below to learn more about the CubeSats being developed at NASA's Jet Propulsion Lab in California.

PCM briefing: ASHRAE offers building restoration guidelines; TNT lands customers for new va-Q-tec shipper

Ben Welter - Monday, April 18, 2016

ASHRAE has proposed guidelines that balance the need for energy conservation and authenticity in the restoration of historic buildings. The guidelines address planning and operation, mechanical systems, building envelopes and lighting.

• Express delivery company TNT has signed up two global customers for its new cold chain packaging and shipping solution, va-Q-tec Ltd.'s Medpak VI°C, which officially launches this month. One is a clinical trial company; the other is a biotech company.

• In partnership with 3D Systems and the U.S. Department of Energy, the University of Maryland has used the latest 3D printing technology to manufacture a heat exchanger which is said to be 20 percent more efficient than current technology.

• The 2017 Zayed Future Energy Prize competition, which recognizes "significant contributions in the global response to the future of energy," is now open for entries. Winners are eligible to win up to $1.5 million. This year's winners included BYD Company Ltd. of China, the world's largest rechargeable battery supplier; and Kopernik, an Indonesia nonprofit that distributes solar lights, solar home systems, water filters and clean cookstoves in developing countries.  

PCM briefing: New TES tank at California college; Grid Edge Award for Steffes Corp.

Ben Welter - Monday, April 11, 2016

Chaffey College TES tankA 709,500-gallon thermal storage tank, right, is helping Chaffey College of Rancho Cucamonga, Calif., cut cooling costs. The centerpiece of the school's newly expanded central plant helps shift chiller operation from on-peak to off-peak hours, when electricity is less costly.

Steffes Corp., a North Dakota company that makes electric thermal storage systems, has earned a Greentech Media Grid Edge Award. The company's partnership with Hawaiian Electric, Sequentric and Battelle on a grid-interactive water heater system earned Steffes a place on the Grid Edge list. Other honorees this year include Duke Energy, BMW Group and Tesla

National Renewable Energy Laboratory researchers have demonstrated that carbon nanotubes have the potential to act as a thermoelectric power generator that captures and uses waste heat.

Suman Jha, a fourth-year mechanical engineering student at Dr MGR University in Chennai, India, is sold on the importance of phase change material in reducing energy consumption. His study of smart construction materials has found that PCMs can cut air-conditioning loads by 40 to 50 percent.

PCM briefing: Nevada CSP plant ready for commercial operation; Sonoco again makes list of most-admired companies

Ben Welter - Thursday, February 25, 2016

SolarReserve’s Crescent Dunes solar tower with molten salt thermal storage has successfully generated electricity at its full 110 MW capacity. Over the next 12 months, the concentrated solar project will gradually ramp up to full commercial operation under its 25-year power purchase agreement with NV Energy, supplying electricity to Las Vegas and other parts of Nevada. Related: SolarReserve has submitted a plan to build a 110MW solar tower and thermal storage plant in South Australia.

Ares 1 helmet • Ares A1, Steelbird's new line of helmets for India's growing motorcycle market, uses phase change material to manage thermal comfort.

Packaging giant Sonoco has again made Fortune magazine's list of most-admired companies. Apple tops this list. 

Peli BioThermal officially unveiled its new European Service Center today in Leighton Buzzard, England. The company's re-usable thermal protection packaging systems, including the new Credo Cargo, will be reconditioned at the center.

• A new report from Stratistics MRC projects that the global market for thermal interface materials, which stood at $570 million in 2015, will reach $1.2 billion by 2022. 

At the CERAWeek conference in Houston this week, Dow Chairman and CEO Andrew Liveris said chemical firms must “manage the short term with a maniacal focus on productivity,” while still focusing on long-term strategies. He said the soon-to-merge Dow Chemical and DuPont plastics giants had each grown too large and sprawling.

PCM briefing: The latest innovations in heat exchanger technology; the latest praise for Ember 'smart' mug

Ben Welter - Tuesday, February 02, 2016

Expanded metal baffle / EMbaffle B.V.

Beyond shell and tube: POWER magazine's Aaron Larson takes a look at the latest innovations in heat exchanger technology. Expanded metal baffle designs, such as the one shown above from EMbaffle B.V., promise better heat transfer and eliminate flow-induced vibration.

Esquire magazine selected the Ember temperature-adjustable mug, powered in part by phase change material, as one of the top five gadgets among the thousands displayed at last month's Consumer Electronics Show in Las Vegas. 

German researchers are developing a PCM-based thermal energy storage using salt hydrates and hybrid double-shell concrete tanks. The goal is to convert excess electricity from renewable sources and store it as heat for use in a single building or shared in a smart grid of neighborhood buildings.

NREL lays off 15 solar energy researchers, plans further cuts at Colorado lab

Ben Welter - Thursday, October 08, 2015

The National Renewable Energy Laboratory in Golden, Colo., laid off 15 solar energy researchers this week and announced plans to eliminate 50 to 60 other positions via buyouts. Reduced federal funding for the Department of Energy’s Solar Energy Technologies Office – from $289 million in 2012 to $233 million this year – forced NREL to shift the priorities of its solar research program, spokesman George Douglas told the Denver Post. Additional cuts will come in areas such as business systems, information technology and public affairs.

http://www.denverpost.com/business/ci_28934958/nrel-cutting-4-workforce-lays-off-solar-researchers