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 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

Thermodynamic Analysis for the Selection of low GWP Refrigerants in Ground Source Heat Pumps

One of the main objectives of the European Commission in the buildings sector, responsible for approximately 40% of total energy consumption and 36% of greenhouse gas emissions, is to identify technological solutions capable of reducing energy consumption and at the same time greenhouse gas emissions. For this purpose, ground source heat pump system (GSHPs) is a technology of particular interest that promises to considerably reduce greenhouse gas emissions of HVAC systems (up to 44% compared to air source heat pumps). In order to develop and test innovative GSHPs to be used for heating and cooling in the various European climatic zones, EU has funded the GEO4CIVHIC project, which will have a duration of 4 years and will end in 2022. As part of the project, the problem of identifying new generation low environmental impact refrigerants to be used in innovative GSHPs is tackled. In this article, we report the results of an energetic and exergetic analysis of the performance of heat pumps based on simulations carried out both on simple reverse cycles and on more complex cycles. Low pressure alternative fluids have been considered as an alternative to R134a and high pressure fluids as an alternative to R410A. The simulations were conducted at various heat sink and heat source temperature conditions, in order to evaluate the GSHPs performance in the whole range of real conditions that can be found in Europe. Particular attention was paid to the compression phase, with the aim to simulate the compressor performance in a more realistic way than simply assuming constant isentropic efficiency

Italian prototype building models for urban scale building performance simulation

Urban building energy modeling (UBEM) seeks to evaluate strategies to optimize building energy use at urban scale to support a city's building energy goals. Prototype building models are usually developed to represent typical urban building characteristics of a specific use type, construction year, and climate zone, as detailed characteristics of individual buildings at urban scale are difficult to obtain. This study investigated the Italian building stock, developing 46 building prototypes, based on construction year, for residential and office buildings. The study included 16 single-family buildings, 16 multi-family buildings, and 14 office buildings. Building envelope properties and heating, ventilation, and air conditioning system characteristics were defined according to existing building energy codes and standards for climatic zone E, which covers about half the Italian municipalities. Novel contributions of this study include (1) detailed specifications of prototype building energy models for Italian residential and office buildings that can be adopted by UBEM tools, and (2) a dataset in GeoJSON format of Italian urban buildings compiled from diverse data sources and national standards. The developed prototype building specifications, the building dataset, and the workflow can be applied to create other building prototypes and to support Italian national building energy efficiency and environmental goals

A European Database of Building Energy Profiles to Support the Design of Ground Source Heat Pumps

[EN] 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 Koppen-Geiger climate scale.This work received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 657982.Carnieletto, L.; Badenes Badenes, B.; Belliardi, M.; Bernardi, A.; Graci, S.; Emmi, G.; Urchueguía Schölzel, JF.... (2019). A European Database of Building Energy Profiles to Support the Design of Ground Source Heat Pumps. Energies. 12(13):1-23. https://doi.org/10.3390/en12132496S1231213De Carli, M., Tonon, M., Zarrella, A., & Zecchin, R. (2010). A computational capacity resistance model (CaRM) for vertical ground-coupled heat exchangers. Renewable Energy, 35(7), 1537-1550. doi:10.1016/j.renene.2009.11.034Grossi, I., Dongellini, M., Piazzi, A., & Morini, G. L. (2018). Dynamic modelling and energy performance analysis of an innovative dual-source heat pump system. Applied Thermal Engineering, 142, 745-759. doi:10.1016/j.applthermaleng.2018.07.022Engineering Reference Manual. In EnergyPlus V8.5https://energyplus.net/Sandberg, N. H., Bergsdal, H., & Brattebø, H. (2011). Historical energy analysis of the Norwegian dwelling stock. Building Research & Information, 39(1), 1-15. doi:10.1080/09613218.2010.528186Application of Energy Performance Indicators for Residential Building Stocks Experiences of the EPISCOPE Projecthttp://episcope.eu/fileadmin/episcope/public/docs/reports/EPISCOPE_Indicators_ConceptAndExperiences.pdfGustafsson, M., Dipasquale, C., Poppi, S., Bellini, A., Fedrizzi, R., Bales, C., … Holmberg, S. (2017). Economic and environmental analysis of energy renovation packages for European office buildings. Energy and Buildings, 148, 155-165. doi:10.1016/j.enbuild.2017.04.079De Carli, M., Bernardi, A., Cultrera, M., Dalla Santa, G., Di Bella, A., Emmi, G., … Zarrella, A. (2018). A Database for Climatic Conditions around Europe for Promoting GSHP Solutions. Geosciences, 8(2), 71. doi:10.3390/geosciences8020071Cartalis, C., Synodinou, A., Proedrou, M., Tsangrassoulis, A., & Santamouris, M. (2001). Modifications in energy demand in urban areas as a result of climate changes: an assessment for the southeast Mediterranean region. Energy Conversion and Management, 42(14), 1647-1656. doi:10.1016/s0196-8904(00)00156-4Kottek, M., Grieser, J., Beck, C., Rudolf, B., & Rubel, F. (2006). World Map of the Köppen-Geiger climate classification updated. Meteorologische Zeitschrift, 15(3), 259-263. doi:10.1127/0941-2948/2006/0130Herrera, M., Natarajan, S., Coley, D. A., Kershaw, T., Ramallo-González, A. P., Eames, M., … Wood, M. (2017). A review of current and future weather data for building simulation. Building Services Engineering Research and Technology, 38(5), 602-627. doi:10.1177/0143624417705937Peel, M. C., Finlayson, B. L., & McMahon, T. A. (2007). Updated world map of the Köppen-Geiger climate classification. Hydrology and Earth System Sciences, 11(5), 1633-1644. doi:10.5194/hess-11-1633-2007D’Amico, A., Ciulla, G., Panno, D., & Ferrari, S. (2019). Building energy demand assessment through heating degree days: The importance of a climatic dataset. Applied Energy, 242, 1285-1306. doi:10.1016/j.apenergy.2019.03.167Al-Hadhrami, L. M. (2013). Comprehensive review of cooling and heating degree days characteristics over Kingdom of Saudi Arabia. Renewable and Sustainable Energy Reviews, 27, 305-314. doi:10.1016/j.rser.2013.04.034Degree Days.net-Custom Degree Day Datahttp://www.degreedays.netAnnunziata, E., Frey, M., & Rizzi, F. (2013). Towards nearly zero-energy buildings: The state-of-art of national regulations in Europe. Energy, 57, 125-133. doi:10.1016/j.energy.2012.11.049Principle for Nearly Zero-Energy Buildings, Ecofys Germany GmbHhttp://bpie.eu/documents/BPIE/publications/LR_nZEB%20study.pdfAhern, C., Griffiths, P., & O’Flaherty, M. (2013). State of the Irish housing stock—Modelling the heat losses of Ireland’s existing detached rural housing stock & estimating the benefit of thermal retrofit measures on this stock. Energy Policy, 55, 139-151. doi:10.1016/j.enpol.2012.11.039Kaklauskas, A., Zavadskas, E. K., Raslanas, S., Ginevicius, R., Komka, A., & Malinauskas, P. (2006). Selection of low-e windows in retrofit of public buildings by applying multiple criteria method COPRAS: A Lithuanian case. Energy and Buildings, 38(5), 454-462. doi:10.1016/j.enbuild.2005.08.005Zavadskas, E., Raslanas, S., & Kaklauskas, A. (2008). The selection of effective retrofit scenarios for panel houses in urban neighborhoods based on expected energy savings and increase in market value: The Vilnius case. Energy and Buildings, 40(4), 573-587. doi:10.1016/j.enbuild.2007.04.015Aerts, D., Minnen, J., Glorieux, I., Wouters, I., & Descamps, F. (2014). A method for the identification and modelling of realistic domestic occupancy sequences for building energy demand simulations and peer comparison. Building and Environment, 75, 67-78. doi:10.1016/j.buildenv.2014.01.021Yang, Z., & Becerik-Gerber, B. (2014). The coupled effects of personalized occupancy profile based HVAC schedules and room reassignment on building energy use. Energy and Buildings, 78, 113-122. doi:10.1016/j.enbuild.2014.04.002Richardson, I., Thomson, M., & Infield, D. (2008). A high-resolution domestic building occupancy model for energy demand simulations. Energy and Buildings, 40(8), 1560-1566. doi:10.1016/j.enbuild.2008.02.006Villi, G., Peretti, C., Graci, S., & De Carli, M. (2013). Building leakage analysis and infiltration modelling for an Italian multi-family building. Journal of Building Performance Simulation, 6(2), 98-118. doi:10.1080/19401493.2012.69998

Monitoring the change of indoor environmental conditions of refurbished buildings in Milan

The energy performance gap, i.e. the difference between measured and predicted behaviour of buildings, is one of the main challenges for the building simulation community and it is highly relevant due to the increasing number of building renovations fostered by recent European Directives. In fact, occupants have a high influence on the building energy use for space heating and cooling, especially in refurbished buildings. The user behaviour may be indirectly investigated by monitoring the indoor environmental conditions before and after the refurbishment. However, in the literature there is a lack of monitoring studies that study the impact of user habits on the predicted energy savings for retrofitted buildings. This study contributes to filling this gap by analysing the air temperature and relative humidity monitored in twenty apartments in the city of Milan (Italy) during two consecutive years. Among them, eight were refurbished during the spring/summer period between the two monitored heating seasons. The analysis of the measured data shows that there is a slight increase in the average indoor air temperature of refurbished apartments. Moreover, the application of a simple hygrometric balance show that users are likely to increase air change rate in naturally ventilated buildings after their refurbishment. Finally, Energy Plus simulations of two monitored apartments showed that such changes in the indoor environmental conditions lead to significant variation in the energy needs for space heating

Toward a resilient campus: Analysis of university buildings to evaluate fast implementing strategies to reduce the energy consumption

The present energy crisis together with the evolving climate have raised awareness on the need of improving the energy performance of existing buildings and their resilience. Actions implementable within a short time and without the need of large retrofit interventions should be prioritized. In this research, the effect of easy to implement control strategies promoted by the enrgy manager on the buildings of a university campus were investigated. The energy performance models of seven buildings composing the Ca´Foscari University Scientific Campus in Venice (Italy) were constructed using EnergyPlus energy modeling software and calibrated by means of monitoring data, with the scope of defining a baseline for the simulation of control strategies adjustments. Different actions applied to all the buildings were simulated and analysed: during the heating season the set point temperature was lowered first by 1 °C and then by 2 °C, whereas during the cooling period the upper temperature limit of 26 °C was raised at 27 °C and 28 °C. Such adjustments in the setpoints should couple with user adaptation, mainly for what concern clothing and the use of low-energy personal devices (e.g. small desk fans). Results show a positive trend in lowering energy consumption levels, and additional scenarios are tested in order to assess their benefits. Results of these analyses are meant to inform the energy management department of the university on the impact that such strategies may have on operational costs, and can be of inspiration for other universities seeking for fast and low-cost strategies to contain building consumptions without compromising thermal comfort

A critical review on heat transfer coefficients between heated and cooled horizontal and vertical surfaces and the room

Since radiant heating and cooling systems have become more and more popular, it is crucial to correctly predict their performance in different operating conditions. Currently, different convective heat transfer coefficients between the surfaces (floor, ceiling and walls) and the room are used. Various equations can be found in literature, based on measurement procedures or on detailed calculations, but there is no general agreement on which values should be used. In this paper a critical review on convective heat transfer coefficients is presented and available expressions for calculating these coefficients are listed. A general agreement has been found between plates and three-dimensional enclosure relations, nonetheless convective coefficients resulting from real or simulated rooms should be preferred. Based on literature studies involving measurements in three-dimensional enclosures, an equation has been proposed. For this equation, also the influence of the chosen reference temperature (air temperature or operative temperature) has been considered

Analysis and application of a lumped-capacitance model for urban building energy modelling

Buildings are one of the major responsible of energy consumption and carbon emissions worldwide. Due to the continuous growth of cities, researchers moved their focus from single buildings to urban scale analyses. The present work aims at demonstrating the reliability of a lumped-capacitance model in the evaluation of heating and cooling demand at urban level. The model presented extends a previous one with different modules for solar radiation pre-processing, HVAC systems and photovoltaic production estimation. A case-study district of 13 buildings in Padua (Italy) has been analysed, considering detailed single buildings simulations with EnergyPlus as benchmark. Results show that the model leads to good accuracy in the evaluation of the district energy demand for both space heating and cooling. The major sources of error are geometrical simplifications, shadowing and thermal zoning effects, thus showing the importance of high-quality input data in urban modelling. However, results highlight how simple corrections may enhance the accuracy when detailed geometrical information is not available. Finally, the model has been used to assess the cost and energy saving potential of several building retrofit measures and PV installations on the considered district, providing an important indication in the investment priority for decision makers

Global Sensitivity Analysis applied to a dynamic energy simulation model: the case study of UniZEB prototype building

Nowadays, due to the growing interest in improving building energy performance, energy models and simulation tools offer new chances to manage the increasing complexity of environments such as nearly Zero- Energy Buildings and Smart Buildings. These tools enable the acceleration of innovation cycles, rapidly exploring new solutions that range from the use of ground source to air source heat pumps, photovoltaic systems, and controlled mechanical ventilation to building automation and HVAC system control. In this scenario, it becomes relevant to define the importance of model inputs and their interactions with respect to the outputs of the model. This paper presents a Global Sensitivity Analysis (GSA) of the TRNSYS-based dynamic model of an nZEB Living-Lab at the University of Padova (Italy). GSA, and in particular the application of the Morris method, provides an overall view of the influence of inputs on outputs, as all the model input factors are varied simultaneously, and the sensitivity is evaluated over the entire range of each input factor