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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 We'll select the best and post the answers here each week.




RAL Quality Association PCM works to spread the word on phase change material

Ben Welter - Wednesday, November 25, 2015

Stefan ThommanThe RAL Quality Association PCM was established in 2004 to develop standards for the phase change material industry. Its European focus is reflected in its member list: BASF, Rubitherm, EMCO and va-Q-tec (Germany), Salca and global-E-systems (Netherlands), and Croda (United Kingdom). Sasol (South Africa) and Pluss Advanced Technologies (India) are also members.

The annual membership fee is 4,000 euros plus a one-time admission fee of 2,000 euros. Members and non-members alike can submit their products to the association for independent testing and earn the RAL Quality Mark.

But the RAL Quality Association PCM does more than establish performance standards and conduct tests. We asked Stefan Thomann, the association's managing director, to speak in detail about the organization’s objectives and the benefits of membership. He kindly responded by e-mail:

“Generally speaking," he explained, "our association has two key objectives":

1. Influencing the political landscape in the EU in favor of PCM

“The EU have set ambitious targets in their 2020 Energy Strategy: reducing [greenhouse gas] emissions by 20%, increasing the share of renewable energy to 20% of consumption and achieve energy savings of 20% as minimum targets. The buildings sector is the one in which the largest savings in energy consumption and [greenhouse gas] emissions could be achieved. The Energy Performance of Buildings Directive (EPBD; from 2010 was certainly a step into the right direction, requiring Member States to set minimum energy performance requirements for new buildings and buildings undergoing deep-renovation.

“One of our key points of criticism is that the EPBD and its national transpositions do pay a lot attention on insulation and efficient heating systems, but do not (sufficiently) address the problem of overheating and thermal comfort in summer. With the modern way of lightweight building these problems will undoubtedly increase or require cooling systems that will spend parts of the saved energy. Both you and I know that PCM would be a perfect solution via passive cooling systems or by combining HVAC systems with PCM. But unfortunately neither the EPBD nor 95% of its national transpositions allow to count PCM as an appropriate means of saving energy and getting incentives for them. We are intensively working on changing this at the moment, both on EU and national level.

“Another interesting aspect in terms of the Energy Strategy is promoting the use of thermal storages based on PCM. Since heat (or cold) is usually the form in which energy is needed, it makes sense to efficiently store thermal energy instead of inefficiently store electricity. This would help increasing the use of renewable energy by storing it from when it is available until when it is actually needed.

2. Promoting the use of high-quality PCM

“The other key objective is to provide high-quality PCM for the various applications, independently certified by the RAL Quality Mark. If customers decide to use PCM in their applications, they want to be 100% sure that the products perform in the way the supplier promised they would and continuously do over their anticipated lifetime. For this reason, we developed Quality and Testing specifications (RAL-GZ 896) for PCM and PCM composites, objects and systems.

RAL Quality Association PCM logo “If manufacturers of PCM comply with the Quality and Testing specifications and can prove the continuous quality with an internal and external monitoring systems, they can use the RAL Quality Mark for their products as a well-acknowledged and independent proof of quality. …

“In my opinion, there is no better way to convince customers of the [value of] high-quality products compared to inferior but cheaper ones than having their long-lasting effectiveness independently confirmed and documented by the RAL Quality Mark. Although the RAL Quality Association is located in Germany, it is open for companies from all over the world and the Quality Mark can just as well be used in all countries – it is not limited to the German market.

“Apart from the actual use of the Quality Mark, I would say that the biggest benefit of being member is the close contact to some of the leading companies producing and applying high-quality PCM and products with PCM and to the European research facilities that are active in this area. [Members] have the right to attend all our General Assembly Meetings – which are about 3 per year at the moment – and to vote on all decisions … [and] shape the future of the Quality Mark and PCM in general. 

“The annual membership fee is 4,000 EUR plus a one-time admission fee of 2,000 EUR in the first year of membership. This is some sort of a compensation payment because the foundation members had to bear the costs for the whole establishment of the association, the Quality and Testing Specifications and all other documents and services like the homepage for example. This amount is only invoiced once and will be strictly used for the association’s objectives.

“The annual membership fee entitles you to attend all General Assembly meetings and to vote on all decisions. There will be no extra fees for using the Quality Mark no matter for how many products you would like to use it – apart from the mere testing costs for the initial test and the external testing.”

Q&A: Determining the melting point of phase change material

Ben Welter - Monday, March 30, 2015

Sankalp Arpit, a junior research fellow at the Indian Institute of Technology in Mumbai, asks:

"I am working on phase change material in which I am doing characterization. I am getting melting point as 168 degree Celsius in DSC. When I am keeping it in quartz glass by increasing its volume, and I am keeping it in furnace and I am also attaching thermocouple to it and I am measuring it by data logger, then I am getting 179 degree Celsius. Which is the correct method?”

Dr. Mohammed Farid's reply:

"There is no melting point but rather a melting range since these are not pure compounds. I assume you are referring to the start of the melting. If the DSC is done at a very low heating rate, such as 1°C/minute, then the measurement should be accurate but not if the heating rate is high. If the sample is placed in an oven and heated very slowly then that the measured melting point is correct, especially if a clear constant temperature is observed during melting."

Q&A: How is PCM selection dependent on PV panel temperature?

Ben Welter - Friday, March 06, 2015

Shivangi Sharma, a Ph.D. student at the University of Exeter, asks:

"How is the phase change material selection dependent on the photovoltaic panel temperature? For instance, for a PV panel with Tmax = 80°C, but most suitable operating temperature of about 25°C, what should be the best targeted phase change temperature range? Should it be around 25°C or about 80°C for maximum cooling benefits?"

Dr. Mohammed Farid's reply:

"Phase change material cannot work in such an application unless you have an environment where the temperature varies significantly between day and night. You need to select the melting temperature between those two to ensure that the PCM can solidify at night. If the maximum ambient temperature is 25º C and maximum PV temperature is 80º C, then a 30º C PCM may work based on the condition that night temperatures drop to at least 20º C. There is no simple answer to this, but we have built such a system in our laboratory and completed research that will be published soon. I would be happy to direct you to the paper when it becomes available."