Analysis of Vertical Ground Heat Exchangers: The New CaRM Tool☆

Abstract The ground source heat pump systems are worldwide used for space heating and cooling of buildings. The energy efficiency of the heat pump depends on the temperature of the heat carrier fluid on the ground side, which is affected by the annual ground load profile and the arrangement of the boreholes. This paper conducts long-term analysis of two office buildings with unbalanced load profiles in Italy. Work focuses the effects of the heat imbalance on the heat pump entering fluid temperature over ten simulated years. A detailed numerical simulation tool was used to conduct the analysis

Development of a Modelica-based simplified building model for district energy simulations

none4siUrban Building Energy Simulation (UBES) is an efficient tool to investigate and subsequently reduce energy demand of urban areas. Nevertheless, UBES has always been a challenging task due the trade-off between accuracy, computational speed and parametrization. In order to reduce these computation and parameterization requirements, model reduction and simplification methods aim at representing building behaviour with an acceptable accuracy, but using less equations and input parameters. This paper presents the development and validation results of a simplified urban simulation model based on the ISO 13790 Standard and written in the Modelica language. The model describes the thermo-physical behaviour of buildings by means of an equivalent electric network consisting of five resistances and one capacitance. The validation of the model was carried out using four cases of the ANSI/ASHRAE Standard 140. In general, the model shows good accuracy and the validation provided values within the acceptable ranges. © Content from this work may be used under the terms of the Creative Commons Attribution 3.0 Licence.noneMaccarini, Alessandro; Prataviera, Enrico; Zarrella, Angelo; Afshari, AlirezaMaccarini, Alessandro; Prataviera, Enrico; Zarrella, Angelo; Afshari, Alirez

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

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

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

A simulation-based analysis of photovoltaic thermal hybrid solar collectors with a new TRNSYS type model

Nowadays buildings are responsible of 36% of CO2emissions and space heating and cooling alone accounts for 40% of the final energy consumption at European level. In this context, solar-assisted systems represent an important solution to support the decarbonisation pathways in residential sector. In this work, a novel lumped parameter simulation model for photovoltaic thermal hybrid solar collectors developed by Authors as a type of Transient System Simulation (TRNSYS) software is used to carry out computer simulations in different climatic conditions. The model is based on the electrical analogy method to solve the transient heat transfer problem and considers the effect of the thermal capacitances of the elements composing the photovoltaic thermal collector. The simulation tool was also validated with the experimental data in terms of both electrical and thermal power. In this work, a simulation-based analysis is carried out considering three climatic zones in order to evaluate the thermal performance of photovoltaic thermal hybrid solar collectors under different operating conditions

a new air handling unit system for residential buildings experiment and simulation based analysis

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Analysis of a double source heat pump system in a historical building

This work presents the case study of the retrofitting of a historical building of the University of Padua, equipped with a hybrid heat pump system, which uses as heat source/sink the ground and ambient air. The building is located in Padua (Italy) and it is a historical complex of the late 1800, previously used as a geriatric hospital, in which a retrofit process is occurring in order to build the new humanistic campus of the Padua University reaching the highest energy efficiency. The refurbishment is in progress and regards both the building envelope and the plant-system. The building is equipped with two types of heat pumps: the first one is coupled to the ground with borehole heat exchangers and the second is a common air-to-water heat pump. The entire building plant system has been investigated through integrated computer simulations making use of EnergyPlus Software. A new control strategy in order to manage the two types of the heat pumps has been developed in order to increase the energy efficiency. The results outline the potential of the computer simulations in order to control the hybrid heat pump system. In fact, a suitable switch temperature was found in order to move from ground to air source/sink for the heat pumps. In addition, this strategy allows the control of the thermal drift of the ground temperature throughout the years