Enhancement of shallow ground heat exchanger with phase change material

Heat pumps perform better when coupled with ground as thermal source than with air. In literature, several studies and applications suggest and analyse the use of phase change materials (PCMs) coupled with single or double U-tube vertical borehole heat exchangers (BHEs). Usually, PCMs are mixed with the grouting material during the installation. An alternative solution to vertical BHEs is the use of horizontal ground heat exchangers (HGHEs). The present work investigates the possibility of coupling PCMs with a flat-panel HGHE installed inside a trench 2 m under the ground surface. The study analyses the case in which PCMs are adjacent to the HGHE, taking a cue from alternative coupling technologies which have PCMs added to the backfilling material of the trench where the HGHE is installed. The analysis has been conducted with COMSOL software tool. A simulation model of the system was developed to carry out a parametric analysis. The objective of the simulations is the investigation of the thermal behaviour of the HGHE patent pending coupled with PCMs under cycles of operation which represent how the heat pump could work in GSHP system. The results show the meaningful difference of using the PCM in direct contact with the HGHE

Development of an advanced simulation model for solar cooling plants

Solar Cooling systems represent an effective solution to increase the use of solar energy in buildings, satisfying cooling demand in a sustainable and efficient way. Although the reference technologies are mature (solar collectors, absorption chillers, adsorption chillers, etc.), these systems often require detailed studies to define control techniques, management integration systems and energy optimization [1,2]. This work has been focused on the development and calibration of a dynamic simulation model of a solar cooling system in order to create an efficient and robust tool to support the phases of planning and management. The model was developed in Matlab-Simulink ambient taking as a reference the system installed at the building F-51 of ENEA Research Center “Casaccia” in Rome. The calibration carried out made the model representative of reality with an average error of 10% and it has allowed us to quantify the benefits obtained by some optimization measures in order to make the maximum primary energy savings in the overall operation of the system. The simulation model can help to increase the commercial deployment of solar cooling systems when used to identify the layout of plant and the associated control strategies that maximize the system's efficiency and profitability of the investment

Development of an Advanced Simulation Model for Solar Cooling Plants

Abstract Solar Cooling systems represent an effective solution to increase the use of solar energy in buildings, satisfying cooling demand in a sustainable and efficient way. Although the reference technologies are mature (solar collectors, absorption chillers, adsorption chillers, etc.), these systems often require detailed studies to define control techniques, management integration systems and energy optimization [1,2]. This work has been focused on the development and calibration of a dynamic simulation model of a solar cooling system in order to create an efficient and robust tool to support the phases of planning and management. The model was developed in Matlab-Simulink ambient taking as a reference the system installed at the building F-51 of ENEA Research Center "Casaccia" in Rome. The calibration carried out made the model representative of reality with an average error of 10% and it has allowed us to quantify the benefits obtained by some optimization measures in order to make the maximum primary energy savings in the overall operation of the system. The simulation model can help to increase the commercial deployment of solar cooling systems when used to identify the layout of plant and the associated control strategies that maximize the system's efficiency and profitability of the investment

Role of phase change materials in backfilling of flat-panels ground heat exchanger

The behaviour of a multi-source heat pump system coupled with phase change materials (PCMs) is discussed in this manuscript, as based on selected data collected during one-year testing at the TekneHub Laboratory of the University of Ferrara (Italy), as a synergic prototype setup of two European projects: IDEAS, an H2020 project, and CLIWAX, an EFDR project. Three geothermal loops of novel shallow FlatPanels ground heat exchangers (GHX) provide the coupling of a water-to-water heat pump with the ground, as backfilled with sand, a mixture of sand and granules with paraffins and containers filled in with hydrated salts. Furthermore, two hybrid photovoltaic panels and a dry-cooler complete the exploitable thermal sources landscape. Finally, a control unit manages all the elements for the exploitation of the different thermal sources. How the increased underground thermal energy storage is driven by PCMs has been investigated by means of specific tests, and compared with the standard case of backfilling sand. Results confirm that PCMs can compensate peak loads occurring during hard weather conditions. Good performances of the multi-source heat pump were found, with a winter coefficient of performance always higher than 5. Finally, the application of PCM in summer should be preferred in climatic zones with hot summers and cold winters, With evidence, latent heat, thermal conductivity and melting point of PCMs should be tuned accordingly to the energy requirements and the local ground thermal conditions. (c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Solar assisted ground source heat pump in cold climates

The geothermal heat pump(or ground source heat pump) uses the ground as heat source or sink for heating and cooling respectively. The design of the borehole field is the key element of these systems since the wrong evaluation of the boreholes’ length affects the initial costs and/or the energy performance of the heat pump. The geothermal heat pumps are considered as renewable energy technologies, consequently can help the community to reduce the primary energy uses and also the CO2 emissions. However the sustainability and efficiency are ensured in the long period only when the heat balance through the ground is guaranteed. This work evaluates the thermal behavior of ground source heat pumps in cold climates, where the thermal load profile of buildings is not balanced between heating and cooling, especially in residential sector characterized by low internal loads. In these contexts, the heat pump mainly works in heating mode, extracting continuously heat from the ground. As a result, the ground temperature decreases gradually during the years affecting the energy performance of the heat pump. A possible solution to this problem is to use solar thermal collectors to stabilize or gradually increase the mean ground temperature(these systems are called Solar Assisted Ground Source Heat Pump – SAGSHP). In this work a multi floors residential building with 12 flats (88 m2 each)is analyzed in three climate zones, making use of the simulation tool TRNSYS. Different configurations of the plant system have been investigated and the case without the solar thermal collectors has been considered as reference

Solar Assisted Ground Source Heat Pump in Cold Climates

Abstract The geothermal heat pump (or ground source heat pump) uses the ground as heat source or sink for heating and cooling respectively. The design of the borehole field is the key element of these systems since the wrong evaluation of the boreholes' length affects the initial costs and/or the energy performance of the heat pump. The geothermal heat pumps are considered as renewable energy technologies, consequently can help the community to reduce the primary energy uses and also the CO 2 emissions. However the sustainability and efficiency are ensured in the long period only when the heat balance through the ground is guaranteed. This work evaluates the thermal behavior of ground source heat pumps in cold climates, where the thermal load profile of buildings is not balanced between heating and cooling, especially in residential sector characterized by low internal loads. In these contexts, the heat pump mainly works in heating mode, extracting continuously heat from the ground. As a result, the ground temperature decreases gradually during the years affecting the energy performance of the heat pump. A possible solution to this problem is to use solar thermal collectors to stabilize or gradually increase the mean ground temperature (these systems are called Solar Assisted Ground Source Heat Pump – SAGSHP). In this work a multi floors residential building with 12 flats (88 m 2 each) is analyzed in three climate zones, making use of the simulation tool TRNSYS. Different configurations of the plant system have been investigated and the case without the solar thermal collectors has been considered as reference

Comfort and perceived air quality in refurbished social houses with mechanical ventialtion system: The impact of occupants behaviour

Abstract The ever-growing demand for a better indoor air quality in residential buildings is increasing the number of whole-house ventilation system installations in new constructions and renovation. In Italy, for residential sector, the national code does not prescribe the use of mechanical ventilation (MV) systems, so their installation is left to the choice of house owners. Two three-storey social housing apartment blocks in Northern Italy were studied. To reduce energy consumption, building envelopes as well as heating systems were refurbished. The thermal insulation was increased and the existing gas heater units were replaced with more efficient radiant ceiling systems. The refurbishment measures were the same for both constructions beside the MV system, which was installed in only one building. Indoor temperature and relative humidity were monitored for several apartments during the heating season. The occupants were surveyed to investigate their thermal comfort and perceived air quality. The occupants were interviewed to better understand their responses, and to know how they operate the heating system and the mechanical ventilation system (when present). Survey results show that there are no differences in terms of thermal comfort and perceived air quality between the occupants of the buildings with and without MV systems. The findings may be related to occupants' behaviour

Comfort and perceived air quality in refurbished social houses with mechanical ventilation system: The impact of occupants behaviour

The ever-growing demand for a better indoor air quality in residential buildings is increasing the number of whole-house ventilation system installations in new constructions and renovation. In Italy, for residential sector, the national code does not prescribe the use of mechanical ventilation (MV) systems, so their installation is left to the choice of house owners. Two three-storey social housing apartment blocks in Northern Italy were studied. To reduce energy consumption, building envelopes as well as heating systems were refurbished. The thermal insulation was increased and the existing gas heater units were replaced with more efficient radiant ceiling systems. The refurbishment measures were the same for both constructions beside the MV system, which was installed in only one building. Indoor temperature and relative humidity were monitored for several apartments during the heating season. The occupants were surveyed to investigate their thermal comfort and perceived air quality. The occupants were interviewed to better understand their responses, and to know how they operate the heating system and the mechanical ventilation system (when present). Survey results show that there are no differences in terms of thermal comfort and perceived air quality between the occupants of the buildings with and without MV systems. The findings may be related to occupants' behaviour. © 2015 The Authors

Use of municipal solid waste landfill as heat source of heat pump

The heat pump systems are considered today an environmentally friendly technology and, together with other energy production systems from renewable sources, are fundamental for reducing energy consumption and the resulting greenhouse gas emissions due to air conditioning of buildings. The ground source heat pumps use the ground as a heat source able to provide the better energy performance if compared with more common systems which using air as source. The increase of the temperatures inside the controlled landfills of municipal solid waste (MSW), due to the decomposition of waste materials can make the volume of waste a viable alternative in this context, to be used as a heat source for the production of heat. The present work has the objective of analyzing the potential of use of a MSW landfill for space heating through a heat pump. The first part of the work analyzes the main features of a landfill of municipal solid waste starting from system design through to biological degradation processes of organic matter. Subsequently the possible configurations of heat exchangers to be inserted within or covering the landfill is discussed. Based on the findings found in the literature, a dynamic model has been created for a real case study of a MSW landfill located in the north-east of Italy. Boundary conditions (i.e. annual temperature cycles for the soil, heat exchange by convection with the ambient air and radiation, a heat generation function distributed on the rejection of mass) have been imposed to the model in order to carry out annual simulations by means of finite element method, thanks to which the values of temperature reached by the mass of waste have been obtained. By means of the creation of a thermal load profile of a group of users it has been possible to determine the total energy extracted from the landfill and the electricity needed for the operation of the heat pump. The potential energy saving achievable with this type of plant was obtained by comparison with a ground source heat pump using horizontal pipes

Use of Municipal Solid Waste Landfill as Heat Source of Heat Pump

Abstract The heat pump systems are considered today an environmentally friendly technology and, together with other energy production systems from renewable sources, are fundamental for reducing energy consumption and the resulting greenhouse gas emissions due to air conditioning of buildings. The ground source heat pumps use the ground as a heat source able to provide the better energy performance if compared with more common systems which using air as source. The increase of the temperatures inside the controlled landfills of municipal solid waste (MSW), due to the decomposition of waste materials can make the volume of waste a viable alternative in this context, to be used as a heat source for the production of heat. The present work has the objective of analyzing the potential of use of a MSW landfill for space heating through a heat pump. The first part of the work analyzes the main features of a landfill of municipal solid waste starting from system design through to biological degradation processes of organic matter. Subsequently the possible configurations of heat exchangers to be inserted within or covering the landfill is discussed. Based on the findings found in the literature, a dynamic model has been created for a real case study of a MSW landfill located in the north-east of Italy. Boundary conditions (i.e. annual temperature cycles for the soil, heat exchange by convection with the ambient air and radiation, a heat generation function distributed on the rejection of mass) have been imposed to the model in order to carry out annual simulations by means of finite element method, thanks to which the values of temperature reached by the mass of waste have been obtained. By means of the creation of a thermal load profile of a group of users it has been possible to determine the total energy extracted from the landfill and the electricity needed for the operation of the heat pump. The potential energy saving achievable with this type of plant was obtained by comparison with a ground source heat pump using horizontal pipes