Hypothesis for a more efficient and sustainable development of a district heating in Padova, integrating renewable energies and existing generation plant

The present paper shows the background analysis to develop the optimization strategy of a neighborhood heating network sited in Padua, including it in a wider project of district renovation. The case study accounts several different end users: scholastic and offices buildings, a social housing residence and residential buildings. The analysis starts from a systematic assessment of the buildings, evaluating the need of refurbishment of the envelope and of the distribution system. Further analysis focuses on the optimization of the existing heat generation system, integrating three condensing boilers, with an air to water heat pump and a ground source heat pump, which work more efficiently during base-load periods. The management of the district heating network have been investigated using the dynamic simulation tool TRNSYS, the control strategy of the delivery temperature has been tested based on the outside temperature and verifying to satisfy comfort conditions inside the buildings. A sustainable solution is the recovery and drainage of rainwater, that can be reused for the toilets' flushing. Therefore, the project solution identified aims at a more rational use of energy sources, which is the simplest and cheapest way to proceed on the decarbonization path that is a mid-term target for the Padua administration

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

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

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

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

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

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

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