Phase Change Matters

• Wired takes a close look at Arktek, "the Ebola vaccine's high-tech thermos." The World Health Organization is using the PCM-equipped container to transport the temperature-sensitive vaccine to wherever it's needed, whatever the conditions. The container is designed keep payloads colder than -65 C for five days.

• With an eye toward increased profits, CEO Edward Breen says DowDuPont is moving away from large-scale R&D projects in favor of less risky initiatives of $30 million or less.

• Viking Cold Solutions has posted an opening for a business development manager for the Northeastern United States.

• ASHRAE has published a new standard describing a methodology to apply building energy modeling throughout the design process. ASHRAE Standard 209-2018 defines minimum requirements for providing energy design assistance using building energy simulation and analysis.

• Pelican BioThermal is opening its first Canadian drop point for the Credo on Demand rental program. The new drop point, at ATS Healthcare headquarters in Toronto, offers customers an additional location to return temperature-control pallet and bulk shippers. 

Using a phase change composite material, researchers at the University of Illinois at Chicago have developed a novel thermal energy storage system that has the potential to downsize conventional air-conditioner compressors by 50 percent and double compressor efficiency during off- and mid-peak hours.

The research is described in a paper titled “Design and optimization of a hybrid air conditioning system with thermal energy storage using phase change composite,” recently accepted for publication in Energy Conversion and Management. One of the authors, Said Al-Hallaj, a research professor of chemical engineering at UI-Chicago and CEO of AllCell Technologies LLC, answered a few questions by e-mail.

Q: Who led the research team, and how long did the project take?

A: “It is an ongoing project since 2015 at the University of Illinois at Chicago, where I work as a Research Professor of Chemical Engineering, and part of the PhD thesis for my graduate student Ahmed Aljehani.”

Q: Who funded the project? 

A: “Ahmed has a scholarship from his government in Saudi Arabia and we get technical support from our industry partners NETenergy and AllCell Technologies LLC.”

Q: Who supplied the PCM?

A: “I believe it is n-tetradecane (C14H30) PCM that we bought from a distributor and not sure about actual source.”

Q: What is its peak melting point? 

A: “4-6 degrees Celsius.”

Q: What is its thermal storage capacity?

A: “180 kJ/kg (78% PCM, 22% graphite).”

Q: Describe the benchtop PCC/TES system size, components and functionality.

A: “The actual 4 kWh PCC-TES structure is made of 28 slabs of PCC [right]. The whole PCC-TES structure is thermally insulated with building insulation materials. Each slab represents a graphite structure that has been soaked into n-tetradecane for at least 24 h until impregnated with n-tetradecane. The slabs are numbered from top to bottom; top being number 1. The second component is the copper tubes or the copper coils, which pass back and forth in between the 28 slabs. The copper tubes enter the PCC-TES structure from the top and exits from the bottom of the structure.”

Q: Is the concept intended mainly for commercial AC systems, or could it be adapted for residential use?

A: “It should work for both, but commercial AC applications are more economically beneficial due to rate structure and peak demand requirements.”

Q: What are the next steps in developing this concept?

A: “NETenergy, our technology commercialization partner, is partnering with National Renewable Energy Laboratory and a major OEM to build and test a full-scale prototype at NREL facilities in the next year or so.”

https://www.sciencedirect.com/science/article/pii/S019689041830517X

The morning alarm sounds. You wake up, hop in the shower, turn on the tap and … wait. The water might be ice cold for 10 seconds or more, as hot water makes its way from the heater. A Portuguese startup has developed a line of PCM-based products designed to eliminate the wait – and the waste.

Heaboo’s Hoterway shower fixture incorporates a thermal battery that heats the water instantaneously until hot water arrives from the heater. The PCM then recharges as heated water passes through the battery. A thermal mixing faucet automatically keeps the incoming water at a constant temperature.

Heaboo, which delivered its first units to Kickstarter backers last year, also offers standalone thermal batteries designed to supply hot water to sinks, tubs and other fixtures.

Rui Teixeira, Heaboo founder and general director, talked about the products in an e-mail interview:

Q: What kind of PCM is used in the products?

A: “We are currently using a paraffin with additives in our products. We are also trying to use more conventional paraffin to reduce the cost of the PCM. The one that we are using has a heat storage capacity of 230 Joules per gram.”

Q: What is the PCM's peak melting point?

A: “It depends on the specifications of the markets we are addressing. The first product uses a PCM with the melting point 45ºC, but for example in France they would prefer to have a PCM with a melting point above 50ºC; as they supply hot water at the temperature around 60ºC. There is not a big deal because we just need 4-5ºC of temperature differential to ensure that the material melts during the shower period.”

Q: How much PCM is used in each Hoterway?

A: “We are optimizing it, but right now we should be talking about 5 kilograms.”

Q: Who is your PCM supplier?

A: “We currently have two European suppliers, but the main one is still Rubitherm from Germany.”

Q: What material is used to contain the PCM?

A: “We use a PVC extruded pipe with some particular design." 

Q: In addition to Kickstarter, where you raised about 26,000 euros, what are your funding sources for this project?

A: “We had to seed investors in the R&D phases. We have four products already in the market and the sales are growing but not as we would like. :)

“We are also looking for industrial partnerships in order to adapt the technology to other applications to diversify our source of income in this early stage and beside that we are looking for an additional investment mainly to optimize production process and increase the go-to-market strategy.”

Q: Heaboo announced a partnership with the Portuguese manufacturer OLI last year. Is the Hoterway manufactured entirely in Portugal?

A: “The partnership with OLI was mainly commercial for the Portuguese market. Currently we have a partnership with an important French manufacturer but I can't reveal the name yet because we are still finishing details about the project. We will adapt the technology to other products related to domestic hot water; the production is still 100% Portuguese but we include accessories that are not made in Portugal, the PCM itself and also the thermal insulation. We use silica vacuum panels to ensure a great insulation with low thickness.”

Q: Will OLI also serve as a distributor of the Hoterway?

A: “OLI is our distributor for Portuguese market but not in exclusivity; in France and Italy we are also developing a distribution network to bring the product there, hopefully during this year." 

Q: How many units have you delivered so far, and how many do you expect to sell in 2018?

A: "Right now we have about 60 units delivered and most of them are installed already; we would like to finish 2018 with 500 units sold." 

Q: What kind of feedback are you getting from consumers?

A: “The feedback is great. The product does exactly as we announced and the users just get rid of the problem they had before. You simply install the product and the waiting time is gone.

“We announce the capacity of the device to be 10 liters after 24 hours from last use, but normally the customer has less quantity of water stagnated in the pipes. That means that they actually still got instant hot water even if they don't use the shower for 48 hours and sometimes 72 hours. This is something highly valued by the customers because it seems that the device works better than we actually said to them.”

A new database for thermal energy storage materials is being developed within the framework of the International Energy Agency’s Energy Conservation through Energy Storage group, Annex 29 and SHC Task 42.

The database is designed to provide characteristic data for phase change, sorption and thermochemical materials. The website, www.thermalmaterials.org, also offers a wiki with definitions related to thermal energy storage. Both areas are open for contributions.

The phase transition data provided for PCMs must be measured according to a DSC-measurement standard. To ensure the quality of the submitted data, contributors must provide a reference measurement using a PCM provided by Fraunhofer ISE.

Stefan Gschwander, head of Group Heat and Cold Storage at Fraunhofer ISE in Freiburg, Germany, said all submitted data will undergo a review process. “If the data is in line with our requirements it can be published in the public area,” he said.

So far, 15 PCMs are listed in the public area. A restricted area of the database is limited to  independently measured materials.

“The data stored is high-quality data which can be used for research, for example
simulation or to design a system,” Gschwander said. “So for our database, the manufacturers normally do not provide data but sample material that is measured from the institutions that are able to measure according the definitions. So far we have measured PCM from Rubitherm, Sasol and BASF. …

“So far we have about 20 different materials in the restricted area and, as we have used it for the development of the measurement standard, many of the materials have been measured several times by different laboratories so that we have a lot more measurements stored in the database.”

Fraunhofer ISE offers independent characterization of PCM, with fees depending on the material and the DSC required to do the measurement.

The ECES is a technology collaboration group that supports the development of electrical energy storage, thermal energy storage, distributed energy storage and borehole thermal energy storage. For more information on the material database project and characterization services, contact Gschwander at stefan.gschwander@ise.fraunhofer.de.

• Synthesis and properties of phase change microcapsule with SiO2-TiO2 hybrid shell [Solar Energy]

• Experimental investigation of melting behaviour of phase change material in finned rectangular enclosures under different inclination angles [Experimental Thermal and Fluid Science]

• Phase change material based cooling of photovoltaic panel: A simplified numerical model for the optimization of the phase change material layer and general economic evaluation [Journal of Cleaner Production]

• Influence of glazed roof containing phase change material on indoor thermal environment and energy consumption [Applied Energy]

• Thermal field and heat storage in a cyclic phase change process caused by several moving melting and solidification interfaces in the layer [International Journal of Thermal Sciences]

• A phase change microactuator based on paraffin wax/expanded graphite/nickel particle composite with induction heating [Sensors and Actuators A: Physical]

• "Preparation and Characterization of Modified Porous Wood Flour/Lauric-Myristic Acid Eutectic Mixture as a Form-Stable Phase Change Material" [Energy & Fuels]

• A novel phase based cooling system for prismatic lithium ion batteries [Institut International du Froid]

• Optimization of solar photovoltaic system integrated with phase change material [Solar Energy]

• A novel heat transfer enhancement technique for performance improvements in encapsulated latent heat storage system [Solar Energy]

• Experimental and numerical investigation of a solar collector/storage system with composite phase change materials [Solar Energy]

• Enhanced thermal conductivity of phase change material nanocomposites based on MnO2 nanowires and nanotubes for energy storage [Solar Energy Materials and Solar Cells]

• Enhancing the Thermosiphon-Driven Discharge of a Latent Heat Thermal Storage System used in a Personal Cooling Device [International Journal of Refrigeration]

• An Overview of Current Status of Cold Chain in China [International Journal of Refrigeration]

• Applications of Thermal Analysis to the Study of Phase-Change Materials [Handbook of Thermal Analysis and Calorimetry]

• Thermo-physical characteristics, mechanical performance and long-term stability of high temperature latent heat storages based on paraffin-polymer compounds [Thermochimica Acta]

• High thermal conductive paraffin/calcium carbonate phase change microcapsules based composites with different carbon network [Applied Energy]

• 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]