TES : Thermal energy storage in cementitious composites
Deputy Chair: Dr. Antonio CAGGIANO
1 Main Objective
Energy consumption by heating/cooling of the existing building stock accounts for almost 40 percent of the total European energy demand. Energy efficiency, by implementing novel technologies, is considered the key approach for cutting back this high consumption for existing but also for new buildings. For this, three main visions have been identified viz. (i) energetically enhancing the building envelope (heat insulation for sealing, windows and facades), (ii) employing advanced technical building equipment (lighting, heating and ventilation systems) and (iii) using sustainable building systems (i.e., sustainable energies, automatization operations and efficiency-centred planning).
In this context, storing thermal-energy in cementitious-composites (i.e., solar and/or environmental heat/cooling) in components of residential or non-residential buildings is a promising way to level-out daily temperature differences, and to significantly reduce energy demands/consumptions.
The main aim of this new TC is, therefore, to create a State of the ARt (STAR) report, possibly along with recommendations and guidelines, on how to (i) experimentally characterize, (ii) analytically analyse, (iii) numerically describe, and (iv) provide recipes for these novel cementitious-composites capable of Thermal Energy Storage (TES), and which can be employed as energy efficient applications in buildings and/or civil engineering structures.
The TC activities will cover three main TES phenomena in cementitious composites, such as:
- Sensible Heat Storage (SHS): by using the material heat capacity and temperature changes during heating and cooling;
- Latent-Heat Storage (LHS): associated with processes of phase changes: solid-liquid (melting) and vice versa (crystallizations), solid-solid, etc. These materials are classical known as Phase Change Materials (PCMs).
- Thermo-Chemical Storage (TCS): with the thermal energy storage deriving from the conversation of chemical potentials and vice versa.
The proposed TC will review actual experimental test procedures, numerical solution strategies and other relevant results available in literature, on components, composites, constructive elements (like walls, roofs, floors, building envelopes) and buildings made of TES cementitious composites. Moreover, the TC will aim at giving further directions on the reviewed results and to the employability of available scientifically-based test methods and numerical models for TES applications. Several numerical tools and simulation programs, such as TRNSYS, EnergyPlus, ESP-r, IDA ICE or WUFI, are nowadays already available for predicting and analyzing the energy efficiency of buildings. Mostly, these models are used to determine the energy consumption, to evaluate the cost of energy usage in buildings, and/or to determine the most appropriate choice of Heating, Ventilation and Air Conditioning (HVAC) systems, with the aim to control the targeted indoor thermal comfort. The available models very often consider only one aspect of a building energy balance, such as the heat transfer and thermal comfort analysis, while sometimes couple multiple transport phenomena like heat, air, moisture, light, in a unique modelling tool. In this TC, however, emphasis will be only on the various physical-chemical-mechanical properties that determine the efficiency of TES in construction applications. Available models will be reviewed, systematically discussed and explained on their employability for academics, industrial representatives, standardisation bodies, practitioners, engineers, architects and other interested users in general. The possible RILEM recommendation will therefore provide a framework for bringing TES-based solutions via energy and building guidelines/recipes into practice, whereas it will also serve to identify eventually existing omissions and knowledge gaps that may be used by scientists for future research directions.
The TC will consider the following structure (based on a 4 years duration):
- Experimental characterization methods (year 1 and 2): Identifying and selecting the currently available experimental methods available for investigating the thermal energy storage properties of cementitious composites (storage of sensible heat - SHS, of latent heat - LHS and of chemical heat - TCS). Four scale levels will be identified: (i) components (e.g. binders, aggregates, PCM, etc.); (ii) composites (pastes, mortars, concretes); constructive systems (walls, envelope layers, etc.) and full-scale buildings. A possible set-up of a database for components, composites and constructive systems for cementitious materials and buildings will be considered as well.
- Theoretical models and numerical tools (year 2 and 3): Reviewing TES constitutive models at different levels of observations: nano-, micro-, meso-, macro and building scale level. Scientifically-based codes and commercially available models will be reviewed.
- Codes, standards and guidelines (year 3 and 4): Developing a workable and practical framework for employing TES-based composites in cement-based applications for structures and/or buildings. Three complementary documents are foreseen to be provided: i) a STAR: reporting the actual state of the art on TES-based cementitious composites; ii) Recommendations on experimental testing: standardized procedures for experimental characterization of TES-based cementitious composites; iii) Technical guidelines on how to design a TES-based cementitious composites with energy-based simulation software and/analysis.
Terms of reference
The estimated lifetime of the new TC is 4 years. During this period, objectives will be pursued by combining literature and member-based information. In this framework, members of the new TC will be actively approached via the RILEM network, conferences and/or invitation for participation. Aim is to select members from academia and industry (i.e., scientists, designers, contractors, consultants, owners, and maintainers) in such a way that the full chain of activities related to energy-saving in construction will be covered.
- Will the work imply bibliographical research? Or round-robin testing? Or development of new equipment
The work will imply bibliographical research and a targeted round-robin test. Particularly, DSC measurements for investigating the thermal-energy storage properties of material components, characterized by both sensitive and latent heat storage capacity, will be carried out within the framework of a round-robin test, among the participating institutes. The proposed methodology and approach has the purpose to identify sample and instrument-specific influences, which turned out to largely affect DSC characterization measurements (especially during latent - phase change - processes), and hence, to make DSC results more objective and comparable.
Two components/composites will be considered for this purposes:
- Paraffinic waxes (PCM having a melting ranges between 23-26 °C);
- Cement pastes enhanced with the above PCM (microencapsulated, i.e. MPCM);
TU-Darmstadt will prepare the following samples to send to each the participant:
- Paraffinic waxes: 3 samples of 10 mg and 3 samples of 20 mg;
- PCM-cement paste samples (28 days cured and fully dried – 10% of amount of MPCM): 3 samples of 20 mg;
- PCM-cement paste samples (28 days cured and fully dried – 20% of amount of MPCM): 3 samples of 20 mg.
- Clarify in which respect the work of the TC will have direct industrial relevance.
The work of the TC will have direct industrial impact since new energy saving products are demanded in order to comply with the European carbon neutrality in 2050 (https://ec.europa.eu/clima/policies/strategies/2050_en). The guidelines and/or recommendations will directly support the industry on this.
Detailed working programme
The new TC is aiming at organizing two regular meetings per year to adjust progress and to (re)schedule activities. These two meetings will be scheduled during the yearly RILEM week (classically done in autumn season) and RILEM spring convention (classically done in spring season). Two additional internet-based meeting may be also scheduled based on request. Potential events combined with the meetings are planned as follows:
Kick-off meeting: introduction of members, suggestion of new members, overview of members’ competences and experiences, overview of the activities, organisation of initial workshop.
Meeting will possibly be done during the RILEM Week 2020.
½ -year meeting: Listing initial results, presenting progress and figuring out the structure of the STAR.
1st-year meeting: Results, presenting progress, draft of chapters and discussing the overall content of the STAR.
The date and location of the two meetings will be decided during the kick-off meeting and the ½ -year meeting.
1+1/2-year meeting: Preparing first draft of the STAR and discussing the structure of the “Recommendations on experimental testing”.
2nd-year meeting: Completing the STAR draft of chapters and discussing the overall content of the “Recommendations on experimental testing”.
The date and location of the meetings will be decided during the 1st-year meeting and the 1+1/2 -year meeting.
2+1/2-year meeting: Preparing first draft of the “Recommendations on experimental testing” and discussing the structure of the “RILEM technical guidelines”.
3rd-year meeting: Completing the “Recommendations on experimental testing” draft of chapters and discussing the overall content of the “RILEM technical guidelines”.
The date and location of the meetings will be decided during the 2nd-year meeting and the 2+1/2 -year meeting.
3+1/2 -year meeting: Preparing first draft of the “RILEM technical guidelines”.
4th end of the committee: Finishing the committee work by summarizing the TC findings, presenting a special issue of an International symposium held in Sofia. One or more journal publications, STAR and RILEM Test Methods and Guidelines/Recommendation will be published.
The date and location of the meetings will be decided during the 3rd-year meeting and the 3+1/2-year meeting.
As this new TC is targeting to bring existing and further developed knowledge for characterization, simulation and design of TES cementitious composites, buildings and structures, the following committees (past and active) can be directly linked to the following running RILEM TC activities:
- TC 275-HDB: Hygrothermal behaviour and Durability of Bio-aggregate based building materials. Chair: Prof. S. AMZIANE
- TC 230-PSC: Performance-based specifications and control of concrete durability. Chair: H. D. BEUSHAUSEN
- TC 238-SCM: Hydration and microstructure of concrete with supplementary cementitious materials. Chair: N. DE BELIE
- TC 246-TDC: Test methods to determine durability of concrete under combined environmental actions and mechanical load. Chair:Y. YAO
- TC 254-CMS: Thermal cracking of massive concrete structures. Chair: Prof. E. FAIRBAIRN
- TC 263-EEC: Environmental evaluation of concrete structures toward sustainable construction. Chair: Prof. A. KATZ
Furthermore, the TC activities will establish contacts with;
- International standardisation bodies (e.g., EU commission directions: i.e., “The European Green Deal” and the “New European industrial strategy”; CEN/TC 350-Sustainability of construction works, etc.),
- National standardisation bodies (e.g., DIN German Working committee NA 062-08-14 AA “Thermal Analysis”, ANSI/ASHRAE Standards).
The TC activities will be directly linked to the following EAC official course of RILEM:
- Computational Methods for Building Physics and Construction Materials (Eduardus Koenders, TU Darmstadt, Germany)
- Multiscale Modelling for Concrete (MMC) (Erik Schlangen, Delft University of Technology, The Netherlands)
Finally, links may be established with the following international research projects:
- NRG-STORAGE project (n° 870114, 2020-2024), Integrated porous cementitious Nanocomposites in non-Residential building envelopes for Green active/passive energy STORAGE, financed by the European Union H2020 Framework under the LC-EEB-01-2019 call, H2020-NMBP-ST-IND-2018-2020/H2020-NMBP-EEB-2019, IA type, www.nrg-storage.eu; https://cordis.europa.eu/project/id/870114.
- Switch2Save project (n° 869929, 2019-2023), Lightweight switchable smart solutions for energy saving large windows and glass façades, financed by the European Union H2020 Framework under the LC-EEB-01-2019 call, H2020-NMBP-ST-IND-2018-2020/H2020-NMBP-EEB-2019, IA type, https://switch2save.eu/; https://cordis.europa.eu/project/id/869929.
- PowerSkin+ project (n° 869898, 2019-2023), Highly advanced modular integration of insulation, energising and storage systems for non-residential buildings, financed by the European Union H2020 Framework under the LC-EEB-01-2019 call, H2020-NMBP-ST-IND-2018-2020/H2020-NMBP-EEB-2019, IA type, https://www.powerskinplus.eu/; https://cordis.europa.eu/project/id/869898.
- PoroPCM Project, Functional Porous Cementitious Nanocomposites for Heat Storage in Buildings Using Phase Change Materials, (part of the EIG CONCERT-Japan funding, http://concert-japan.eu/).
Direct deliverables of this new TC will be the realization of a RILEM STAR report, RILEM Recommendation on experimental testing and RILEM Technical guidelines that enable to (i) TES characterize and (ii) energy-saving simulate and design cementitious composites, constructive systems and structures which adopt TES-based systems.
Therefore, the new TC will produce:
- STAR report (complementary to the RILEM Recommendations), which will contain major theoretical backgrounds of models, methods and theories used;
- RILEM Recommendations on experimental testing: based on the STAR document;
- RILEM Technical guidelines: based on both the STAR document and recommendations.
Group of users
The group of users (GUs) should contain academia, industry, end-users, standardisation and governmental bodies that represent the main actors for what concerning the residential and non-residential buildings energy consumption worldwide.
In particular GUs will be:
- Designers, engineers and consultants who apply the new RILEM Recommendations and Guidelines for designing most energy efficient new buildings and/or retrofitting existing ones. The new RILEM Recommendations and Guidelines will guide to design, execute, (actively and passively) operate and maintain novel TES concrete technologies employable in ultimate energy-saving buildings.
- Owners of concrete structures and infrastructures, e.g. governmental or private developers that require a certain guarantee on energy performance/consumption along Typical Meteorological Years for different countries and locations.
- Materials suppliers that will understand better their customers’ needs, requirements and criteria for characterizing their products, in view of TES and energy-saving cementitious composites and structures.
- Contractors that will have a guideline to execute the construction in line with the RILEM Recommendations and Guidelines requirements and to achieve the so-called “Nearly-Zero-Energy Buildings”.
- Laboratories in charge of materials testing, quality control and site monitoring will know how to conduct TES tests during the design, execution, operation and maintenance stage.
- In order to foster awareness and acceptance of the new TES concretes through a hugely conservative market, specific actions are foreseen for establishing contacts with relevant standardisation bodies at national and international level. The TC is willing to promote collaboration and sharing with national and international standardisation associations, as well as governmental bodies.
Specific use of the results
Energy-efficient materials and technologies, as general perspective, will add value on decarbonising the EU building stock and developing affordable and integrated energy storage solutions with a huge economic, scientific and environmental impact in terms of recyclability, favouring renewable resources and respect of sustainability principles. The reduction of embodied energy and CO2, footprint of the materials and components used to realise building envelopes will be key to further decrease the CO2 emissions and energy consumption of new buildings or retrofitted ones over their whole life cycle.
The results of the TC work can be evaluated via the following impacts:
- Reduced CO2 emissions due to the improved heat storage capacity of energy-saving concretes. This TC will allow to give directions in significantly improving of materials heat storage capacity (embodied energy), which leads to have highly efficient performance, reduction use of materials (thickness) and maximum CO2 savings. For example, huge improvements of insulation properties in ultra-lightweight concretes, designed together with their TES (dynamic and passively activated) capacities, generate reduced insulation thicknesses or costs of the final building envelope.
- Reduced need of natural resources: the projected reduction of the overall thicknesses of constructive systems (roof, walls, facades, and building envelopes) in comparison with the current adopted technologies (e.g. a regular insulation EPS layer) enables the possibility to significantly reduce the amount of raw materials and associated energy demands to produce these raw materials.
- Enhanced fire safety: critical fire safety of insulation material like EPS or wools, used in building envelopes, has become a key issue. The new TC will favour to design novel TES cementitious composites which have a particular non-flammability and favouring their use will help on enhancing fire protection in buildings.
- Towards Nearly-Zero-Energy Buildings: this is one of the key elements of the 2019/2021 EU Buildings Directive, where it has been emphasized that new buildings of the EU-Member States have to be designed as “Nearly-Zero-Energy Buildings" as from the beginning of 2021 onwards. For public non-residential buildings, this obligation should become active in 2019, and will be permanently anchored in future building legislation. Therefore, this TC will have a huge impact in this field