Quantifying the decarbonization potential of mobile heat battery in low-temperature district heating

This research assesses the potential of a mobile thermochemical storage system, the mobile heat battery (M-HB), for decarbonizing a low-temperature district heating (DH) system in the Netherlands. The assessment is built on a case study where the M-HB is used to transport waste heat from different sources to a neighborhood interface of a DH system. This case study utilizes a simulation-based methodology to calculate the emissions from grid electricity, DH, and M-HB transport and charging. Building performance simulation is used as the main experimental method in combination with both empirical data and theoretical assumptions. Various system operational strategies and uncertain factors are explored, and waste heat sources are screened by different decarbonization targets. Findings indicate that using the M-HB can reduce the operational carbon emissions by up to 80%, from approximately 60-70 kgCO2/GJ of the system without M-HB to around 13 kgCO2/GJ in optimal scenarios. Emissions from M-HB transport and charging are identified as more influential to the decarbonization potential than other considered factors, which addresses the significance of choosing proper waste heat sources. Despite some limitations from data availability and assumptions, this work identifies both opportunities and challenges for using M-HB to decarbonize DH systems

Accelerating the hydration reaction of potassium carbonate using organic dopants

Potassium carbonate has recently been identified as a promising candidate for thermochemical energy storage. However, as for many salt hydrates, the reaction kinetics is limited, and moreover, the hydration transition is kinetically hindered due to a metastable zone, involving limited mobility. This work aims to improve mobility by using organic potassium dopants, it shows that doping with potassium-formate and -acetate, can accelerate the hydration reaction. It has been shown that these dopants can enhance the hydration rate by two mechanisms i.e. introducing mobility due to adsorption of more water or introducing more surface area, where water adsorption can occur. This work opens up new possibilities for organic dopants to enhance the performance of salt hydrates.</p

Elucidating the Dehydration Pathways of K₂CO₃·1.5H₂O

Potassium carbonate sesquihydrate has previously been identified as a promising material for thermochemical energy storage. The hydration and cyclic behavior have been extensively studied in the literature, but detailed investigation into the different processes occurring during dehydration is lacking. In this work, a systematic investigation into the different dehydration steps is conducted. It is found that at higher temperatures, dehydration of pristine material occurs as a single process since water removal from the pristine crystals is difficult. After a single cycle, due to morphological changes, dehydration now occurs as two processes, starting at lower temperatures. The morphological changes open new pathways for water removal at the newly generated edges, corners, and steps of the crystal surface. The observations from this work may contribute to material design as they elucidate the relation between material structure and behavior.</p

A design optimization method for solar-driven thermochemical storage systems based on building performance simulation

The challenge of the temporal mismatch between energy supply and demand in buildings is growing with the increasing share of renewable energy in total energy consumption. Among all the state-of-the-art energy storage solutions, thermochemical heat storage shows a unique potential thanks to its considerable energy density, acceptable cost, and negligible heat loss. For this reason, it becomes a promising alternative to common sensible heat storage solutions for building applications. The integration of such a novel technology in buildings necessitates a method for the assessment of its potential impact and benefit, the comparison to common alternatives, and the optimization of the system design. This work proposes a method based on modeling and simulation of the interaction between the thermochemical heat storage system and the building using a data-driven surrogate model of the storage system in combination with a building performance simulation engine. The data-driven model was developed and validated based on laboratory measurements of a novel closed-loop thermochemical heat storage system, the heat battery (HB). The method was demonstrated in a case study to identify the optimal size of the HB in a solar-driven configuration based on a residential building use case. The results show that the heat battery can digest the thermal energy transferred from the solar thermal collector to reduce the original electricity consumption for heating the detached house (0.7 MWh to 1.0 MWh in considered cases) without any obvious sacrifice in thermal comfort and that the small-scale HB (with a storage volume below 160 liters) shows efficient usage of the designed storage capacity

A use case assessment method for mobilized heat battery in residential buildings

Mobilized thermal energy storage is a potential way of transporting heat from sustainable sources to buildings for their heat consumption. The heat battery, a novel closed-loop thermochemical heat storage system, can also be integrated into a mobilized configuration. To steer the development of the mobilized heat battery toward this promising application, this paper proposes a method for assessing the use case of mobilized heat battery based on building performance simulation experiments. The method is demonstrated in an investigation into the use case based on two residential communities in the Netherlands. The investigation indicates the method can be used for assessing the use case of the mobilized heat battery, as well as other purposes such as heat battery demand prediction, waste heat scheduling, cost management, and system optimization

In Search of a Common European Approach to a Healthy Indoor Environment

Increasingly, policymakers in Europe and around the world are realizing the importance of healthy indoor environments for public health. Certain member states of the European Union (EU) have already achieved successes in improving indoor environmental quality, such as controlling certain contaminants (e.g., environmental tobacco smoke) or developing nationwide policies that address indoor air generally. However, a common European approach to achieving healthy indoor environments is desirable for several reasons including providing a broader recognition of the problem of unhealthy indoor air, setting a policy example for all 27 EU member states, and achieving greater public health equity across the different European nations. In this article we address the question “Why is it so difficult in the EU to develop a coherent approach on indoor environment?” We identify and describe four main barriers: a) the subsidiarity principle in EU policymaking, introducing decentralization of decision making to the member states; b) fragmentation of the topic of the indoor environment; c) the differences in climate and governance among different member states that make a common policy difficult; and d) economic issues. We discuss potential lessons and recommendations from EU and U.S. successes in achieving healthier indoor environments through various policy mechanisms

Direct observation of the moisture distribution in calcium aluminate cement and hydratable alumina-bonded castables during first-drying: an NMR study

The drying behavior for various calcium aluminate cement and hydratable alumina-bonded refractory castables was investigated in the first-drying temperature range (100°C-300°C). Using a specialized high-temperature Nuclear Magnetic Resonance setup, we were able to directly and nondestructively measure the spatially and temporally resolved moisture distribution, while simultaneously measuring the temperature distribution as well. These measurements show that the drying front position is a linear function of time, which can be explained on the basis of a simplified model where only vapor transport is considered. Based on the measurements and the model, one can directly determine the permeability at high temperatures. Moreover, the results demonstrate that the drying front speed and temperature strongly correlates with the control of key material parameters (eg, water demand, binder content, etc). In particular, microsilica fume-containing low-cement castables displayed the highest vapor pressures, while regular castables generated the lowest vapor pressures reflecting the permeability of these materials

Penicillium rubens germination on desiccated and nutrient-depleted conditions depends on the water activity during sporogenesis

Fungal growth often appears in a surrounding where water and nutrients are scarce. The impact of this environment during sporogenesis on subsequent growth is often neglected. This study investigates the effect of water availability during sporogenesis on subsequent early growth. Therefore, a carbon-depleted substrate was constructed. Humidity is then the only parameter of interest. The water conditions during sporogenesis, and during subsequent growth, were varied. This is a stressing environment: no carbon source is present, and water provided solely via the vapour. The lag time, t l, and initial growth rate, μ fp, of the germ tubes were monitored. The effect of a w history on germination and initial growth depends on the RH of the environment. Only at low RH do spores produced at low a w have a smaller t l and higher μ fp compared to those grown at high a w. This result was remarkably pronounced when the substrate was also made hydrophobic: growth only occurred when spores were developed at low a w and placed in high RH. Spores grown on lowered a w attract more water. It is hypothesized that this attraction affects subsequent growth behaviour, and is the reason why growth on hydrophobic glass only prevails in the condition of high RH and lowered a w history. We demonstrate the influence of cultivation conditions on germination, which becomes more pronounced in a more desiccated environment

Hyphal growth of Penicillium rubens in changing relative humidity

When considering mold prevention strategies, the environmental conditions in which fungi grow need to be taken into consideration. This environment is often characterized by a time-dependent relative humidity, and porous substrate. Growth has mainly been investigated in steady-state experiments. Therefore, the goal of this study is to understand the hyphal growth of Penicillium rubens on porous gypsum, under dynamic humidity conditions. Spores of P. rubens were inoculated on porous gypsum containing nutrients, and placed in a small incubation chamber, allowing for microscopic hyphal observation. The relative humidity in this chamber varied multiple times between a high (close to 100%) and low value (35%, 55%, or 75%). The hyphae reacted to a lowered relative humidity by an immediate growth stop and dehydration. When the relative humidity was increased again, the hyphae re-hydrated and three responses were found: regrowing after approximately 4 h, after a time equal to the germination time, or no regrowth at all. No substantial regrowth was found for fluctuations faster than 4 h. This time-scale was found for multiple decreases in relative humidity, and has been reported for the first time. Key points: • Hyphae restart growth after a characteristic time of approximately 4 h. • Relative humidity fluctuations of 3 h can suppress hyphal growth. • Hyphae do not regrow after a severe desiccation and short periods of high humidity

NMR study of the microstructures and water-polymer interactions in cross-linked polyurethane coatings

The microstructure of a polymer coating plays an important role in the water uptake behavior. This paper aims to correlate the molecular mobility and the water–polymer interactions with the microstructures of a highly cross-linked PU system. GARfield NMR imaging was used to monitor in situ the water uptake of the PU coating at different temperatures. The results of continuum T2 fitting show that at temperatures below the enthalpy relaxation temperature (65 °C) the PU coating uptakes water, whereas the polymer matrix is not plasticized by the presence of water. At higher temperatures, however, the polymer matrix is significantly mobilized by the presence of water molecules as indicated by the appearance of the longer T2 component. The water content in the PU coating is monitored by GARfield NMR at different temperatures. The results show that the water content decreases in two steps as the temperature decreases from 85 °C to the room temperature. This result is explained in combination with the molecular relaxation phenomenon probed by the DSC. A microstructure model was formulated based on the experimental results