As described in the previous article, the HFM 446 Lambda Eco-Line is virtually indispensable when it comes to evaluating insulation materials. Instruments are in operation daily at our customers’ sites all around the world.Simultanesously, HFM 446 devices in our NETZSCH Applications Laboratory and R&D premises have not only a regional impact but also a global one too, as highlighted in the following.
Within the European Union alone, some 50% of energy consumption is related to heating and cooling of buildings and industry. It represents the main energy end-use sector, ahead of transport and electricity. This phenomenon can be attributed to various developments such as the growing world population, improving living standards, and the spreading aspiration to constantly ensure active indoor thermal comfort. To make matters worse, only about 22% of the energy used for heating and cooling can be assigned to renewable sources, whilst approximately 75% is still generated from fossil fuels. Considering the EU’s target of becoming carbon-neutral by the year 2050, the heating and cooling sector urgently needs major advances in energy efficiency, building sustainability and a cut back of fossil fuel consumption. ,,
By participating in the EU-funded NRG-STORAGE project, NETZSCH is actively contributing to the attainment of this target. Within the frame of the project, the HFM 446 M is used to support the development of new building insulation materials. Under the project management of Technical University of Darmstadt, 13 partners from Europe and one from Argentina are collaborating to develop a cement foam with embedded bio-based Phase Change Materials (PCM) and graphene-oxide particles.
The requirements of this new composite foam are to have a 25% higher insulation capacity, 10% higher energy-strorage capacity and 10% higher water and air-tightness compared to conventional building insulations. Furthermore, it will need to be less flammable than current material solutions as well as being recycable.
The project is subdivided into six work packages. The first work package focuses on the characterization of all single components and at cement paste scale. Here at NETZSCH, the thermal behavior of the single materials, for example, the heat storage capacity of all components and the melting ranges for the PCMs are determined via different measuring methods such as DSC (Differential Scanning Calorimetry) and LFA (Laser Flash Analysis), using very small sample quantities of only a few milligrams.
The second work package deals with first cement foam specimens. Such samples are more heterogeneous and larger in sample size. Therefore, they require a different measurement approach. At this stage, the thermal conductivity, the main hallmark of an insulation material, comes into play. Our task at NETZSCH is to measure composite foam specimens in different mixtures with our HFM 446 M (Heat Flow Meter Series) using samples of 30 cm x 30 cm and 4 cm in thickness to achieve their thermal conductivity, as well as Specific Heat Capacity (cp)Heat capacity is a material-specific physical quantity, determined by the amount of heat supplied to specimen, divided by the resulting temperature increase. The specific heat capacity is related to a unit mass of the specimen.specific heat capacity, and compare them to the results we previously obtained for the single components.
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As an example, the thermal conductivity results for four foam specimens are shown in Figure 2. These foams have a porosity of 80-90% and their values rise by increasing temperatures within the range of 0 to 40°C.
The highest thermal conductivities of 0.075 to 0.085 W/(m·K) were obtained on the Reference foam (not containing PCM) featuring a raw DensityThe mass density is defined as the ratio between mass and volume. density of 240 kg/m³ and lie approximately 11% above the results of the Reference foam with 220 kg/m³. Comparing the Reference foam 240 and foam with same raw density but containing 10% PCM, the thermal conductivity decreases by 17%. This effect can be explained by the lower thermal conductivity of the powder material which replaces the higher conducting concrete. The lowest thermal conductivities between 0.059 and 0.068 W/(m·K) were observed on the foam specimen with 20% PCM, this being 22% below the reference mixture without PCM. Despite the fact that the effect of PCM is not linear, the thermal conductivity of the cement foam decreases by replacing parts of the concrete with PCM. However, the main reason for adding PCM is to further increase the specific heat capacity of the composite foam, and thereby the energy storage capacity of the insulation material.
Based on these HFM results, the most promising foam mixtures will then be selected for the scale-up in work package three and four. In work package three, this insulation foam is added to wall segments replicating the final application, which results in even bigger specimen sizes and more influence factors. These walls (1.50m x 1.50m) are investigated for thermal transmittance in a so-called Hot Box device under controlled temperature and humidity conditions. The Method is similar to the HFM.
In work package four, the best performing and most promising NRG foams are selected and monitored under “real-world conditions” at demo houses in Bulgaria and retrofitted buildings in Germany and Spain over a longer period of time.
Throughout all these steps of scale-up towards the final product, the experimental work is verified by numerical simulations.
This project started in 2020 and is planned to run through to March 2024. We will keep you updated!
 L. Pérez-Lombard, J. Ortiz, C. Pout, A review on buildings energy consumption information, Energy and Buildings 40 (3) (2008) 394–398.
 N. Soares, J.J. Costa, A.R. Gaspar, P. Santos, Review of passive PCM latent heat thermal energy storage systems towards buildings’ energy efficiency, Energy and Buildings 59 (2013) 82–103.
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