Elements That Contribute to Healthy Building Design

BACKGROUND: The elements that contribute to a healthy building are multifactorial and can be discussed from different perspectives. OBJECTIVES: We present three viewpoints of designing a healthy building: the importance of sustainable development, the role of occupants for ensuring indoor air quality, and ongoing developments related to indoor finishes with low chemical emissions and good fungal resistance. DISCUSSION: Sustainable design rediscovers the social, environmental, and technical values of pedestrian and mixed-use communities, using existing infrastructures including “main streets ” and small-town planning principles and recapturing indoor–outdoor relationships. This type of design introduces nonpolluting materials and assemblies with lower energy requirements and higher durability and recyclability. Building occupants play a major role in maintaining healthy indoor environments, especially in residences. Contributors to indoor air quality include cleaning habits and other behaviors; consumer products, furnishings, and appliances purchases, as well as where and how the occupants use them. Certification of consumer products and building materials as lowemitting products is a primary control measure for achieving good indoor air quality. Key products in this respect are office furniture, flooring, paints and coatings, adhesives and sealants, wall coverings, wood products, textiles, insulation, and cleaning products. Finishing materials play a major role in the quality of indoor air as related to moisture retention and mold growth. CONCLUSIONS: Sustainable design emphasizes the needs of infrastructure, lower energy consumption, durability, and recyclability. To ensure good indoor air quality, the product development for household use should aim to reduce material susceptibility to contaminants such as mold and should adopt consumer-oriented product labeling

Impact of cycling on the performance of mm-sized salt hydrate particles

Potassium carbonate is shown to be a promising salt for thermochemical heat storage. For a thermochemical reactor application, the salt hydrate is manufactured in mm-sized particles. It is known that salt hydrate particles undergo swelling and cracking during cyclic testing. Therefore, in this work the influence of cycling on structural and morphological evolution is investigated and the resulting impact on the hydration performance. It is found that the incremental volume increase during cycling is independent of the density at which a particle is produced. With lower starting relative density particles are found to be stable for more cycles compared to particles produced with high starting relative densities. Powder formation at the particle surface starts as soon as the particle density is close to values reported for percolation thresholds. The morphological changes during cycling result in formation of isolated pores and a highly tortuous pore system. As a result, the effective diffusion coefficient for cycled particles is lower compared to what is predicted for as produced particles with similar porosity resulting in lower power output than expected based on porosity. The results from this work help in understanding the reasons for swelling, cracking, powder formation and decreased performance with cycling, laying the foundation for mitigating these unwanted effects.</p

Impact of cycling on the performance of mm-sized salt hydrate particles

Potassium carbonate is shown to be a promising salt for thermochemical heat storage. For a thermochemical reactor application, the salt hydrate is manufactured in mm-sized particles. It is known that salt hydrate particles undergo swelling and cracking during cyclic testing. Therefore, in this work the influence of cycling on structural and morphological evolution is investigated and the resulting impact on the hydration performance. It is found that the incremental volume increase during cycling is independent of the density at which a particle is produced. With lower starting relative density particles are found to be stable for more cycles compared to particles produced with high starting relative densities. Powder formation at the particle surface starts as soon as the particle density is close to values reported for percolation thresholds. The morphological changes during cycling result in formation of isolated pores and a highly tortuous pore system. As a result, the effective diffusion coefficient for cycled particles is lower compared to what is predicted for as produced particles with similar porosity resulting in lower power output than expected based on porosity. The results from this work help in understanding the reasons for swelling, cracking, powder formation and decreased performance with cycling, laying the foundation for mitigating these unwanted effects.</p

A scaling rule for power output of salt hydrate tablets for thermochemical energy storage

Salt hydrates are thermochemical materials capable of storing and releasing heat through reversible reaction with water vapor. In a heat battery, salt hydrate tablets of millimeter size are necessary to ensure a sufficient permeability of the packed bed. A profound understanding of the hydration process of these tablets is required to improve their kinetic performance. In this study we show that the hydration timescale of salt tablets is transport limited and that it depends primarily on the porosity and on the driving force (Δp). From gravimetric measurements done on SrBr2·6H2O and CaC2O4 we derived the intrinsic reaction and effective diffusion coefficients (k and Deff) and found that they validate a front-diffusion limited hydration hypothesis. In particular, the obtained Deff values (0.8–4.5 mm2 s−1) only depend on the tablets' porosities. Based on these parameters, we calculated the second Damköhler number (DaII) and proved that many other hydration reactions are diffusion limited. In the case of identical structures, the power output is therefore controlled only by the driving force. Its variation could be predicted by calculation of a so-called power scaling factor (Λ) for a selection of salts. This power scaling factor depends on the enthalpy (ΔH) and entropy (ΔS) of the reaction. For a temperature output of 40 °C and at 12 mbar most hydration reactions fall in the interval 0&lt;Λ&lt;30 and Λ exceeds 30 only in very few cases. This parameter establishes therefore another important constraint to the selection of the most ideal salt. Suitable strategies to circumvent the diffusion limitation will lead to the development of next generation salt hydrate tablets for thermochemical energy storage.</p

NMR Profiling of Reaction and Transport in Thin Layers:A Review

Reaction and transport processes in thin layers of between 10 and 1000 µm are important factors in determining their performance, stability and degradation. In this review, we discuss the potential of high-gradient Nuclear Magnetic Resonance (NMR) as a tool to study both reactions and transport in these layers spatially and temporally resolved. As the NMR resolution depends on gradient strength, the high spatial resolution required in submillimeter layers can only be achieved with specially designed high-gradient setups. Three different high-gradient setups exist: STRAFI (STRay FIeld), GARField (Gradient-At-Right-angles-to-Field) and MOUSE (MObile Universal Surface Explorer). The aim of this review is to provide a detailed overview of the three techniques and their ability to visualize reactions and transport processes using physical observable properties such as hydrogen density, diffusion, T1-and T2-relaxation. Finally, different examples from literature will be presented to illustrate the wide variety of applications that can be studied and the corresponding value of the techniques.</p

Boosting thermochemical performance of SrBr₂·6H₂O with a secondary salt hydrate

This work systematically investigates the effect of 9 inorganic salt hydrates on the performance of strontium bromide (SrBr2) a thermochemical material (TCM). The goal is to boost the performance of this base salt by enhancing the reaction kinetics of the SrBr2 6-1 transition or by shrinking the reaction hysteresis. The study shows that the added salts that do not share a common ion with SrBr2 (LiCl, LiF, ZnF2, ZnI2, K2CO3) give limited to no benefits. The lack of improvement is due to a side reaction between SrBr2 and the added salt leading to the formation of new salt hydrate with low hygroscopicity that does not contribute to the thermochemical reaction. The addition of hygroscopic bromide salts with divalent cations (ZnBr2, CaBr2, MnBr2) gave mixed results depending on the sample history. The most likely cause is cation exchange between bromide salts occurring during exposure to high vapour pressures which promote ionic mobility. The overall best performance was achieved with the addition of LiBr, which we attribute to its high hygroscopicity.</p

Stabilization of salt hydrates using flexible polymeric networks

The use of salt hydrates for thermochemical energy storage is associated with mechanical instabilities during cyclic hydration/dehydration. On the other hand, some salt hydrates do not suffer from these drawbacks, but manufacturing of mm-sized particles is still a challenge. In this work a one pot synthesis method is presented which results in composites using poly (dimethyl siloxane) (PDMS) as binder. Energy densities of 1.14 GJ/m3 and 0.67 GJ/m3 are achieved for a K2CO3 and CaC2O4 composite, respectively. Swelling upon hydration decreases compared to non-stabilized particles. The best K2CO3 composite shows mechanical stability for at least 35 cycles, and the average power output at 50 % conversion increases with cycling to 50–55 kW/m3 at 20 °C and 33 % relative humidity. Also, a stable CaC2O4 composite is made suitable for heat storage. The particle volume and hydration kinetics remain constant for at least 20 cycles. An average power output at 50 % conversion of 5 kW/m3 at 20 °C and 33 % relative humidity is generated. The results from this work show how a one-pot fabrication method can be used to obtain mm-sized particles with enhanced mechanical stability during cycling. Stabilization can be achieved independent of the salt hydrate solubility or material properties.</p

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

Participatory Sensemaking Through Visualising Conversations

Both conversations between people and finding ways to visualize complex phenomena are important topics for sensemaking in systemic design research. This presentation introduces the COCOnUT and TaCo projects, which together create a system that extracts words from conversations, visualizes them using a diagrammatic approach, and enables participants to combine and annotate them in near-real time, using a tangible interface. Particularly in multi-stakeholder contexts such as democratic deliberation, or participatory policy-making, the ability for participants to see what is being said (and what has been said) by themselves and others and to investigate and interact with themes emerging from the conversation—ideas that have been re-stated or reframed, terms used to mean different things, different terms used to mean the same thing, ideas which should be grouped together, and so on – are all part of a process of understanding each other’s understanding. Ongoing work will explore possibilities for this kind of tool as part of participatory sensemaking in design and conversation processes

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