European Shallow Geothermal Days Presentation (2022)

Presentation of GEOFIT at the European Shallow Geothermal Days 2022

Title: Introducing GEOFIT: Easy-to-install, economical and enhanced geothermal systems for energy efficient building retrofitting

Language: English

Author: Henk Witte (Groenholland)

Summary: GEOFIT is an EU-funded research project focussing on the use of shallow geothermal energy for heating and cooling of buildings. It specifically addresses retrofitting, therefore tackling the specific issues one has to face while designing, installing and operating a geothermal system in an existing building (Ground source Heat Exchanger – HEX, Heat Pump – HP, heating and cooling emission system).

GEOFIT aims to answer to the challenge by developing easy-to-install and efficient underground coupling systems, including historical buildings, to make geothermal energy a standard source of heat and cold in building renovation. Such systems consider the difficulties in drilling in built environments. The project also develops improved, more cost-efficient and less environmental-impacting heat pumps to optimize the use of the energy generated by geothermal systems. GEOFIT embraces the whole path of design-site survey-installation-operation. It particularly investigates coupling between GHEX and HP and between HP and heating/cooling emission systems, thus providing guidelines for planners to reduce errors and ensure high performance of the systems.

To aid the selection of different Ground Heat Exchanger technologies and support the design, an advanced integrated design toolkit is developed. This engineering toolkit allows the engineer to design and compare the different GHEX (vertical, horizontal, slinky and spiral/earth basket type) in an integrated model framework. The approach in the engineering toolkit is based on the well-known finite line source approach and implements G-functions to speed calculation. New finite line source models have been developed and validated for spiral type heat exchangers. Other advances include detailed (temperature dependent) fluid properties correlations and inclusion of seasonally varying temperature gradients. The finite line source model for spiral heat exchangers has been validated with sand-box experiments and CFD calculations.

Performance Analysis of a Geothermal Radiant Cooling System Supported by Dehumidification

Article published in Energies

Title: Performance Analysis of a Geothermal Radiant Cooling System Supported by Dehumidification

Language: English

Authors: Henrikki Pieskä (*1) , Adnan Ploskić (*1,2), Sture Holmberg (*1), Qian Wang (*1,3).

*1: Division of Sustainable Buildings, School of Architecture and the Built Environment, KTH Royal Institute of Technology, Brinellvägen 23, SE, 10044, Stockholm, Sweden
*2: Bravida Holding AB, Mikrofonvägen 28, SE, 12637, Hägersten, Sweden
*3: Uponor AB, Hackstavägen 1, SE, 72132, Västerås, Sweden

Abstract: Space cooling demand is increasing globally due to climate change. Cooling has also been linked to all 17 sustainable development goals of the United Nations. Adequate cooling improves productivity and thermal comfort and can also prevent health risks. Meanwhile, policy initiatives such as the European Union’s Green Deal require participants to cut greenhouse gas emissions and reduce energy use. Therefore, novel cooling systems that are capable of efficiently producing high levels of thermal comfort are needed. Radiant cooling systems provide a design capable of fulfilling these goals, but their application in hot and humid climates is limited due to the risk of condensation. In this study, we compare the performances of radiant cooling systems with and without dehumidification. The studied systems are supplied by geothermal energy. The study is conducted using building energy models of a small office building belonging to a three-building school complex located in Sant Cugat near Barcelona in Spain. The studied location has a Mediterranean climate. The simulations are conducted using IDA Indoor Climate and Energy 4.8 simulation software. The results show that the radiant cooling system with dehumidification (RCD) produces considerably improved thermal comfort conditions, with maximum predicted mean vote (PMV) reached during the cooling season being 0.4 (neutral) and the maximum PMV reached by the radiant cooling system without dehumidification (RC) being 1.2 (slightly warm). However, the improved thermal comfort comes at the cost of reduced energy and exergy efficiency. The RCD system uses 2.2 times as much energy and 5.3 times as much exergy as the RC system. A sensitivity analysis is also conducted to assess the influence of selected input parameters on the simulation output. The results suggest that maximising dehumidification temperature and minimising ventilation flow rate can improve the energy and exergy efficiency of the RCD system while having a minor effect on thermal comfort.

Thermodynamic and Thermal Comfort Performance Evaluation of Two Geothermal High-Temperature Cooling Systems in the Mediterranean Climate

Journal Paper published in Journal of Building Engineering

Title: Thermodynamic and Thermal Comfort Performance Evaluation of Two Geothermal High-Temperature Cooling Systems in the Mediterranean Climate

Language: English

Authors: Henrikki Pieskä (*1) , Cong Wang (*1,2), Behrouz Nourozi (*1), Adnan Ploskic (*1,3), Qian Wang (*1,4).

*1 Division of Sustainable Buildings, School of Architecture and the Built Environment, KTH Royal Institute of Technology, Brinellv¨agen 23, SE-10044, Stockholm, Sweden
*2 College of Urban Construction and Safety Engineering, Shanghai Institute of Technology, 201418, Shanghai, China
*3 Bravida Holding AB, Mikrofonv¨agen 28, SE-12637, Hägersten, Sweden
*4 Uponor AB, Hackstavägen 1, SE-72132, Västerås, Sweden

Abstract: The European Commission aims to reduce the greenhouse gas emissions of the European Union’s building stock by 60% by 2030 compared with 1990. Meanwhile, the global demand for cooling is projected to grow 3% yearly between 2020 and 2050. High-temperature cooling systems provide cooling with lower exergy use than conventional cooling systems and enable the integration of renewable energy sources, and can play a crucial role in meeting the growing cooling demand with less energy use. The aim of this study is to analyse and critically evaluate two high-temperature cooling systems in terms of their energy and exergy use in a case study. We also consider thermal comfort performance, CO2 emissions, and sensitivity to changing operating conditions. The two systems considered are a mechanical ventilation system with heat recovery combined with geothermal cooling (GeoMVHR) and a radiant cooling system with ceiling panels connected to the same geothermal cooling (GeoRadiant) system. The study is conducted using building energy models of a typical office building belonging to a three-building school complex located in Sant Cugat near Barcelona, Spain. IDA ICE 4.8 simulation software was used for the simulations. The results show that the two different installations can produce near-identical thermal comfort conditions for the occupants. The GeoRadiant system achieves this result with 72% lower electricity use and 60% less exergy destruction than the GeoMVHR system. Due to the higher electricity use, the CO2 emissions caused by the GeoMVHR system are 3.5 times the emissions caused by the GeoRadiant system.

Towards Discrete Element Modelling of Rock Drilling (2021)

Towards Discrete Element Modelling of Rock Drilling

Author: Wessling, Albin

Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.ORCID iD: 0000-0003-1345-0740

2021 (English)Licentiate thesis, comprehensive summary (Other academic)

Abstract [en]

The method of percussive rotary drilling is recognized as the most efficient method for hard rock drilling. Despite the clear advantages over conventional rotary meth-ods, there are still uncertainties associated with percussive rotary drilling. For geothermal applications, it is estimated that 50 % of the total cost per installed megawatt of energy is associated with drilling and well construction, with drill bit wear being a predominant cost factor. Numerical modelling and simulation of rock drilling, calibrated and validated towards rigorous experiments, can give insight into the rock drilling process. This thesis is focused on the prerequisites of numer-ical simulations of rock drilling, i.e. the development of a numerical model and experimental characterization of rock materials. A new approach for modelling brittle heterogeneous materials was developed in this work. The model is based on the Bonded Particle Method (BPM) for the Discrete Element Method (DEM), where heterogeneity is introduced in two ways. Firstly, the material grains are rep-resented by random, irregular ellipsoids that are distributed throughout the body. Secondly, these grains are constructed using the BPM-DEM approach with mi-cromechanical parameters governed by the Weibull distribution. The model was applied to the Brazilian Disc Test (BDT), where crack initiation, propagation, coalescence and branching could be investigated for different levels of heterogene-ity and intergranular cement strengths. The initiation and propagation of the cracks were found to be highly dependent on the level of heterogeneity and cement strengths. In the experimental study, the static and dynamic properties of two rock materials – Kuru grey granite and Kuru black diorite – were obtained from uniaxial compression and indirect tension tests. A Split-Hopkinson Pressure Bar was used to obtain the dynamic properties. Using high-speed photography with frame rate 663,000 fps, the crack initiation and propagation could be studied in de-tail, and the full-field exterior deformation fields of the samples were evaluated by using digital image correlation. From the high-speed images, the onset of unstable crack growth was detected. The crack-damage stresses, associated with unstable crack growth, was approx. 90 % of the peak strength in the dynamic compression tests, whereas the tensile crack-damage stress was approx 70 % of the tensile peak strength.

Place, publisher, year, edition, pages

Luleå: Luleå University of Technology, 2021.


Licentiate thesis / Luleå University of Technology, ISSN 1402-1757

A Statistical DEM Approach for Modelling Heterogeneous Brittle Materials (2021)

Article published in Computational Particle Mechanics, Springer, 2021.

Title: A statistical DEM approach for modelling heterogeneous brittle materials

Language: English

Authors: Albin Wessling (*1), Simon Larsson (*1), Pär Jonsén (*1), Jörgen Kajberg (*1)

*1: Division of Mechanics of Solid Materials, Luleå University of Technology, 97187 Luleå, Sweden

Abstract: By utilizing numerical models and simulation, insights about the fracture process of brittle heterogeneous materials can be gained without the need for expensive, difficult, or even impossible, experiments. Brittle and heterogeneous materials like rocks usually exhibit a large spread of experimental data and there is a need for a stochastic model that can mimic this behaviour. In this work, a new numerical approach, based on the Bonded Discrete Element Method, for modelling of heterogeneous brittle materials is proposed and evaluated. The material properties are introduced into the model via two main inputs. Firstly, the grains are constructed as ellipsoidal subsets of spherical discrete elements. The sizes and shapes of these ellipsoidal subsets are randomized, which introduces a grain shape heterogeneity Secondly, the micromechanical parameters of the constituent particles of the grains are given by the Weibull distribution. The model was applied to the Brazilian Disc Test, where the crack initiation, propagation, coalescence and branching could be investigated for different sets of grain cement strengths and sample heterogeneities. The crack initiation and propagation was found to be highly dependent on the level of heterogeneity and cement strength. Specifically, the amount of cracks initiating from the loading contact was found to be more prevalent for cases with higher cement strength and lower heterogeneity, while a more severe zigzag shaped crack pattern was found for the cases with lower cement strength and higher heterogeneity. Generally, the proposed model was found to be able to capture typical phenomena associated with brittle heterogeneous materials, e.g. the unpredictability of the strength in tension and crack properties.

Design Requirements for Condensation-Free Operation of High-Temperature Cooling Systems in Mediterranean Climate

Article pulished in Building and Environment (2020)

Title: Design Requirements for Condensation-Free Operation of High-Temperature Cooling Systems in Mediterranean Climate

Language: English

Authors: Henrikki Pieskä (*1) , Adnan Ploskić (*1,2), Qian Wang (*1,3).

*1: Division of Sustainable Buildings, School of Architecture and the Built Environment, KTH Royal Institute of Technology, Brinellvägen 23, SE, 10044, Stockholm, Sweden
*2: Bravida Holding AB, Mikrofonvägen 28, SE, 12637, Hägersten, Sweden
*3: Uponor AB, Hackstavägen 1, SE, 72132, Västerås, Sweden

Abstract: Radiant cooling systems are a subject of increasing scientific interest due to their efficiency and ability to use high-temperature cooling sources. In hot and humid conditions, they have generally been studied in combination with dehumidification systems. For retrofit projects, a control system that would eliminate the need for dehumidification would be beneficial. In the present study, a passive geothermal-based radiant high-temperature cooling system is studied in a Mediterranean climate. The system is operated with supply water temperature control using dew point temperature as a controlling variable. The system’s performance is compared with that of an all-air cooling system. The systems are evaluated using IDA-ICE building energy simulations, validated with on-site measurement data. The results show that the radiant cooling system produces the same level of thermal comfort with 40% lower energy use and 85% lower exergy consumption than the all-air system. The risk of condensation limits the cooling capacity of the radiant cooling system. Consequently, insufficient cooling capacity causes thermal discomfort for the occupants due to the operative temperature exceeding 26 ◦C.

IBPSA UK Conference paper (2020)

Conference paper presented in IBPSA-England Building Simulation and Optimisation Conference 2020

Available for download in NUIG repository and Zenodo.

Title: A novel ROM methodology to support the estimation of the energy savings under the Measurement and Verification protocol.

Language: English

Authors: Alessandro Piccinini (*1,2,3), Magdalena Hajdukiewicz (*1,2,3), Letizia D’Angelo (*1,2,3), Luis Miguel
Blanes (*1,2,3), Marcus M. Keane (*1,2,3)

*1: School of Engineering, College of Science and Engineering, National University of Ireland
Galway, Ireland
*2: Informatics Research Unit for Sustainable Engineering (IRUSE) Galway, Ireland
*3: Ryan Institute, National University of Ireland Galway, Ireland

Abstract: This paper presents a novel Reduced Order grey box Model (ROM) methodology, based on a Resistor-Capacitor (RC) network, which supports the creation of the baseline energy consumption and the estimation of energy savings due to Energy Conservation Measures (ECMs) under the Measurement and Verification protocol. Within this scope, a description of the RC network, including a calculation of the parameters’ needed to execute the ROM, are presented. This ROM methodology is demonstrated on an educational building located in Sant Cugat, Spain as part of the H2020 GEOFIT project. The results presented in this paper demonstrate that the ROM is sufficiently accurate for the creation of the baseline energy consumption and for estimating the energy savings of different ECMs.

Energies Article (2020)

Article pulished in Energies Journal (2020)

Title: An Integrated HBIM Simulation Approach for Energy Retrofit of Historical Buildings Implemented in a Case Study of a Medieval Fortress in Italy

Language: German

Authors: Cristina Piselli (*1,2) , Jessica Romanelli (*2), Matteo Di Grazia (*2), Augusto Gavagni (*2), Elisa Moretti (*1,2), Andrea Nicolini (*1,2), Franco Cotana (*1,2), Francesco Strangis (*2), Henk J. L. Witte (*3) and Anna Laura Pisello (*1,2).

*1: Department of Engineering, University of Perugia, 06125 Perugia, Italy.
*2: CIRIAF – Centro Interuniversitario di Ricerca sull’Inquinamento da Agenti Fisici, Interuniversity Research
Centre, University of Perugia, 06125 Perugia, Italy.
*3: Groenholland Geo-Energysystems, Valschermkade 26, 1059CD Amsterdam, The Netherlands

Abstract: The Italian building stock consists of buildings mainly constructed until the mid-20th century using pre-industrial construction techniques. These buildings require energy refurbishment that takes into account the preservation of their architectural heritage. In this view, this work studies an innovative integrated modelling and simulation framework consisting of the implementation of Historical Building Information Modeling (HBIM) for the energy retrofit of historical buildings with renewable geothermal HVAC system. To this aim, the field case study is part of a medieval complex in Central Italy (Perugia), as representative ancient rural offshore architecture in the European countryside. The system involves of a ground source heat pump, a water tank for thermal-energy storage connected to a low-temperature radiant system, and an air-handling unit. The building heating energy performance, typically influenced by thermal inertia in historical buildings, when coupled to the novel HVAC system, is comparatively assessed against a traditional scenario implementing a natural-gas boiler, and made inter-operative within the HBIM ad hoc platform. Results show that the innovative renewable energy system provides relevant benefits while preserving minor visual and architectural impact within the historical complex, and also in terms of both energy saving, CO2 emissions offset, and operation costs compared to the traditional existing system. The integrated HBIM approach may effectively drive the path toward regeneration and re-functioning of heritage in Europe.

Data in Brief Paper (2020)

Paper published in Data in Brief Journal (2020)

Title: Data collected by coupling fix and wearable sensors for addressing urban microclimate variability in an historical Italian city

Language: English

Authors: Benedetta Pioppi (*a), Ilaria Pigliautile (*a), Anna Laura Pisello (*a,b)

*a: CIRIAF – Interuniversity Research Centre on Pollution and Environment Mauro Felli, Perugia, Italy
*b: Department of Engineering, Perugia, Italy

Abstract: This article presents the data collected through an extensive research work conducted in a historic hilly town in central Italy during the period 2016-2017. Data concern two different datasets: long-term hygrothermal histories collected in two specific positions of the town object of the research, and three environmental transects collected following on foot the same designed path at three different time of the same day, i.e. during a heat wave event in summer. The short-term monitoring campaign is carried out by means of an innovative wearable weather station specifically developed by the authors and settled upon a bike helmet. Data provided within the short-term monitoring campaign are analysed by computing the apparent temperature, a direct indicator of human thermal comfort in the outdoors. All provided environmental data are geo-referenced. These data are used in order to examine the intra-urban microclimate variability. Outcomes from both long- and short-term monitoring campaigns allow to confirm the existing correlation between the urban forms and functionalities and the corresponding local microclimate conditions, also generated by anthropogenic actions. In detail, higher fractions of built surfaces are associated to generally higher temperatures as emerges by comparing the two long-term air temperature data series, i.e. temperature collected at point 1 is higher than temperature collated at point 2 for the 75% of the monitored period with an average of þ2.8 [1]C. Furthermore, gathered environmental transects demonstrate the high variability of the main environmental parameters below the Urban Canopy. Diversification of the urban thermal behaviour leads to a computed apparent temperature range in between 33.2 [1]C and 46.7 [1]C at 2 p.m. along the monitoring path. Reuse of these data may be helpful for further investigating interesting correlations among urban configuration, anthropogenic actions and microclimate variables affecting outdoor comfort. Additionally, the proposed dataset may be compared to other similar datasets collected in other urban contexts around the world. Finally, it can be compared to other monitoring methodologies such as weather stations and satellite measurements available in the location at the same time.

European Heat Pump Summit Presentation (2019)

Presentation of GEOFIT at the European Heat Pump Summit (2019)

Title: GEOFIT: Ground source heat pump systems for energy efficient building retrofitting.

Language: English

Author: Michael Lauermann (*1)

*1: AIT Austrian Institute of Technology GmbH, Center for Energy,

Summary: The integration of geothermal systems for heating / cooling solutions in conjunction with heat pump technology is a major challenge, particularly in the case of renovation. In order to find the best solution for the increased flow temperatures compared to a new building for the renovation, various heat pump configurations are evaluated according to energy and economic criteria. A refrigerant with low greenhouse gas potential (GWP) is used as the working medium, e.g. R1234ze (E)) less than 10 used. A favorable refrigeration circuit configuration for high flow temperatures is a twin-circuit system, which essentially consists of two heat pumps with different condensing temperatures and the same evaporation temperatures. An alternative to this is a single-stage configuration with a significantly larger condenser for improved supercooling. Both systems should enable efficient operation when renovating buildings.