A method to analyze the performance of geocooling systems with borehole heat exchangers. Results in a monitored residential building in southern alps

Geothermal heat is an increasingly adopted source for satisfying all thermal purposes in buildings by reversible heat pumps (HP). However, for residential buildings located in moderate climates, geocooling, that implies the use of geothermal source for cooling buildings without the operation of HP, is an efficient alternative for space cooling not yet explored enough. Geocooling allows two main benefits: to cool the buildings by high energy efficiencies improving summer comfort; to recharge the ground if space heating is provided by HP exploiting the geothermal source (GSHP). In these cases, geocooling allows to avoid the decreasing of the performances of the GSHP for space heating over the years. To explore these issues, a method has been developed and tested on a real case: a new residential building in Lugano (southern Switzerland) coupled with 13 borehole heat exchangers. The system provides space heating in winter by a GSHP and space cooling in summer by geocooling. During a 40 months monitoring campaign, data such as temperatures, heat flows and electricity consumptions were recorded to calibrate the model and verify the benefits of such configuration. Focusing on summer operation, the efficiency of the system, after the improvements implemented, is above 30, confirming, at least in similar contexts, the feasibility of geocooling. Achieved results provides knowledge for future installations, underlining the replication potential and the possible limits

Low and Ultra‐Low Temperature District Heating Equipped by Heat Pumps—An Analysis of the Best Operative Conditions for a Swiss Case Study

The manuscript analyses the management of low and ultra‐low‐temperature district heating systems (DHS) coupled with centralised and decentralised heat pumps. Operative conditions are defined in order to satisfy the heating needs without overloading the electric grid. The results are achieved by dynamic simulations, based on a real DHS located in southern Switzerland. At the building level, the heating needs are estimated considering real data and simultaneous energy simulations. Two DHS configurations, alternatives to the existing one, are simulated and suitable parameters for the management of the DHS are selected. The global performance of the two DHS is evaluated by KPIs also including the flexibility and the impact on the electric peak due to heat pumps. The achieved results are discussed providing suggestions for the stakeholders involved in DHS management for an optimal matching of the electric grid and thermal networks towards a reduction of the peak power. The rule‐based control strategies defined allow the expected electric peak shaving and load levelling, conversely, the yearly energy consumptions are lightly increased and have to be further investigated. The outcomes demonstrate a global better performance of the ultra‐low temperature DHS in terms of response to the applied control strategies and of energy savings

Geocooling potential of borehole heat exchangers in low energy office buildings analysed with dynamic system simulations

A reference office building has been defined in order to simulate its thermal behaviour and comfort conditions and for assessing potentiality of geocooling with borehole heat exchangers. The building has low heating and cooling demands, a condition that makes it possible to use active concrete plates for heating and cooling. Starting from the reference case, a list of buildings has been defined varying the glazing ratio, internal or external solar protections, windows typologies and the heat distribution systems. A borehole heat exchanger field is coupled to a heat pump in winter and to the heat distribution system in summer through a flat plate heat exchanger. The cooling requirement satisfied by a direct heat transfer into the ground through the borehole heat exchangers is so called geocooling. A dynamic system model has been developed to simulate the building, the emission of thermal energy, the technical installations including the borehole heat exchanger field and the interconnected thermal interactions. Building design, system technical feasibility and limits of the ground coupled system are discussed and result from the analysis of the numerous system simulations. Geocooling potential depends on the quality of the building design and its heat emission. The importance of the ground thermal conductivity and the ground recharge ratio on the system design are highlighted

Geocooling potential of borehole heat exchangers’ systems applied to low energy office buildings. Renewable Energy

ABSTRACT A reference office building has been defined in order to simulate its thermal behaviour and comfort and for assessing potentiality of geocooling with borehole heat exchangers. The building has low heating and cooling demands, a condition that makes it possible to use active concrete plates for heating and cooling. Starting from the reference case, a list of buildings has been defined varying the glazing ratio, internal or external solar protections, windows typologies and the heat distribution systems. A borehole heat exchanger field is coupled to a heat pump in winter and to the heat distribution system in summer through a flat plate heat exchanger. The cooling requirement satisfied by a direct heat transfer into the ground through the borehole heat exchangers is so called geocooling. A dynamic system model has been developed to simulate the building, the emission of thermal energy, the technical installations including the borehole heat exchanger field and the interconnected thermal interactions. Comfort conditions are simulated to fulfil SIA Swiss regulations and standards. They determine the building thermal requirements that have to be covered by the geocooling system. A design procedure is presented for best system design. Building design, system technical feasibility and limits of the ground coupled system are discussed and result from the analysis of the numerous system simulations. Geocooling potential depends on the quality of the building design and its heat emission. The importance of the ground thermal conductivity and the ground recharge ratio on the system design are highlighted

Geocooling potential of borehole heat exchangers' systems applied to low energy office buildings

The potentiality of geocooling (i.e. free cooling) with borehole heat exchangers is analysed for low energy office buildings. The borehole heat exchanger field is coupled to a heat pump in winter and to the cold distribution system in summer through a flat plate heat exchanger. The cooling requirement satisfied by a direct heat transfer into the ground through the borehole heat exchangers is so-called geocooling. A dynamic system model has been developed to simulate the building, the emission of thermal energy through thermally activated building systems, the technical installation including the borehole heat exchanger field and the interconnected thermal interactions. Thermal comfort requirements determine the building energy needs and the size of the ground coupled system. A methodology is presented for best system design. Building design, system technical feasibility and limits of the ground coupled system are discussed and result from the analysis of the numerous system simulations. Geocooling potential depends on the quality of the building design and its heat emission. The importance of the ground thermal conductivity and the ground recharge ratio on the system design are highlighted. Simple design sizing keys are proposed for a fast pre-sizing of a borehole field

District thermal systems: State of the art and promising evolutive scenarios. A focus on Italy and Switzerland

In the framework of the built environment enhancement towards energy strategy 2050, interesting debates have been developed at building and district scale. In relation to thermal energy end-uses, that are the most impacting in buildings, district thermal systems (DTS) offer a great flexibility in terms of heat generation technologies and renewable resources integration, resulting, in case of proper management and supply conditions, in primary energy and greenhouse gases savings compared to the most diffuse technologies operating at building scale. Recent progresses in DTS have followed over the years the development of technologies and energy policies resulting in different configurations and operative schemes. The present contribution reviews the different classifications of DTS provided in the technical literature. The European framework of DTS is then analysed, with particular insights to the Italian and Swiss operative context. Currently, DTS have a marginal role in these two countries and can mainly be classified as high-temperature or mid-generation systems. However, there are also innovative systems, on which the attention of the involved stakeholders is focusing. The technological features of DTS are discussed, in order to provide possible challenging evolutive scenarios to enhance their performance and economic appeal through the evaluation of successful recent examples

Application of a method for the sustainable planning and management of ground source heat pump systems in an urban environment, considering the effects of reciprocal thermal interference

The “Most Easy, Efficient and Low Cost Geothermal Systems for Retrofitting Civil and Historical Buildings” (GEO4CIVHIC) project aims to accelerate the deployment of shallow geothermal systems for heating and cooling purposes when retrofitting existing and historical buildings. Analyzing the implementation process of borehole heat exchangers (BHEs), allows the understanding of how to promote the long-term sustainability of shallow geothermal energy systems. The thermal interference between BHE systems represents a problem, especially due to the increasing deployment of this technology and its spread in densely built-up areas. The main goal of this paper is to propose a conceptual model and to apply this to different case studies. The methodology includes phases to adopt an integrated approach for preventing long term thermal interference in neighbouring borehole heat exchangers, by providing management strategies and technical suggestions for design and operation. The method developed follows the following steps: 1) literature review to determine what are the main drivers for thermal interference between shallow geothermal systems, in the context of the GEO4CIVHIC project case study sites; 2) to create a conceptual model to limit thermal interference at both design and operational phases; 3) to apply the developed method to real and virtual case studies in countries with different regulatory frameworks and to test its main strengths and weaknesses. The application of this conceptual model to specific case studies provides evidence of critical planning and operational characteristics of GSHP systems and allows the identification of measures to mitigate impacts of thermal interference to be identified

Definition of standardized energy profiles for heating and cooling of buildings

For promoting the diffusion of GSHP (Ground Source Heat Pumps) a tool for sizing these systems will be carried out in the H2020 research project named \u201cCheap GSHPs\u201d. The paper presents the set up of a database with energy profile of a certain amount of buildings representative of the typology (single family houses, block of flats, office buildings) with different insulation levels and in different climatic conditions. Based on the weather analysis among European climatic files, twenty locations have been considered. For each location the overall energy and the mean hourly monthly energy profiles for heating and cooling (sensible and latent) have been calculated. Based on the results, the correlations with Degree Days (DD) for heating and cooling have been found in order to generalize the results to have pre-calculated profiles for sizing GSHP

A European database of building energy profiles to support the design of ground source heat pumps

The design of ground source heat pumps is a fundamental step to ensure the high energy efficiency of heat pump systems throughout their operating years. To enhance the diffusion of ground source heat pump systems, two different tools are developed in the H2020 research project named, "Cheap GSHPs": A design tool and a decision support system. In both cases, the energy demand of the buildings may not be calculated by the user. The main input data, to evaluate the size of the borehole heat exchangers, is the building energy demand. This paper presents a methodology to correlate energy demand, building typologies, and climatic conditions for different types of residential buildings. Rather than envelope properties, three insulation levels have been considered in different climatic conditions to set up a database of energy profiles. Analyzing European climatic test reference years, 23 locations have been considered. For each location, the overall energy and the mean hourly monthly energy profiles for heating and cooling have been calculated. Pre-calculated profiles are needed to size generation systems and, in particular, ground source heat pumps. For this reason, correlations based on the degree days for heating and cooling demand have been found in order to generalize the results for different buildings. These correlations depend on the Köppen-Geiger climate scale