90 research outputs found
Building Automation and Control Systems and performance optimization: A framework for analysis
No full textThe pressing global environmental issues are fostering a rapid change in the energy and sustainability policies
for the built environment. New paradigms are emerging, such as “Nearly Zero Energy Building” (nZEB), and
resource efficiency is progressively becoming a crucial topic in the building sector, implying an appropriate
consideration of performance over the whole life cycle. However, empirical evidences show how, very often, the
gap between the predicted (design phase) and measured (operation phase) performance is very large, due to
errors committed during all the phases of building life cycle. This performance gap determines a problem of
credibility in the building industry and, more in general, in sustainability oriented practices. Therefore, design
and operation practices should evolve in order to be able to cope with performance uncertainty determined, for
example, by evolution of climate conditions, variability of behavioural patterns and performance degradation of
technological components.
For these reasons, a framework for the analysis of the potential of Building Automation and Control Systems
for performance optimization is proposed. This framework aims to highlight, in particular, the possibility of
establishing an effective methodological continuity among building performance simulation, control and data
analytics, not immediately recognizable in current practices. Further, it aims to envision the possibility of
creating a unified methodological approach, which could guarantee multiple feed-backs from measured data,
useful for the evolution, first of all, of design and operation practices but also, more in general, of the whole
value chain of the building sector
Thermal inertia and energy efficiency - Parametric simulation assessment on a calibrated case study
Get PDFThe reduction of energy consumption for heating and cooling services in the existing building stock is a key challenge for global sustainability today and buildings' envelopes retrofit is one the main issues. Most of the existing buildings' envelopes have low levels of insulation, high thermal losses due to thermal bridges and cracks, absence of appropriate solar control, etc.Further, in building refurbishment, the importance of a system level approach is often undervalued in favour of simplistic "off the shelf" efficient solutions, focused on the reduction of thermal transmittance and on the enhancement of solar control capabilities. In many cases, the importance of the dynamic thermal properties is often neglected or underestimated and the effective thermal capacity is not properly considered as one of the design parameters.The research presented aims to critically assess the influence of the dynamic thermal properties of the building fabric (roof, walls and floors) on sensible heating and cooling energy demand for a case study. The case study chosen is an existing office building which has been retrofitted in recent years and whose energy model has been calibrated according to the data collected in the monitoring process.The research illustrates the variations of the sensible thermal energy demand of the building in different retrofit scenarios, and relates them to the variations of the dynamic thermal properties of the construction components.A parametric simulation study has been performed, encompassing the use of calculation tools and performance metrics at the different scales of the building (envelope-zone-overall building) considering the realistic operating conditions assumed for the initial calibrated model and different climate conditions, typical of the Italian territory and, more in general, of the Southern European and Mediterranean area
Local energy efficiency programs: A monitoring methodology for heating systems
No full textIn recent years, as a result of an important agreement with the Italian Ministry of the Environment, Lombardy Region has promoted and supported numerous measures for energy efficiency and renewableenergy sources integration within its territory. Subsequently, monitoring campaigns have been launched to evaluate the global outcomes of the different calls and programs. Among other types of interventions, the promotion of the replacement of diesel boilers with high efficiency natural gas boilers represents an effective way to reduce primary energydemand and emissions and, more in general, to support the definitive transition from oil derived fuels toless polluting fuels like natural gas.The research presents the results of the monitoring campaign performed on about 1500 heating system's retrofit interventions subsidized by Lombardy Region within its Framework Program Agreementin the field of Environment and Energy. Local energy efficiency programs are particularly important today and have to be designed, managed and monitored to clearly identify the real energy, economic and environmental benefits that they produce. The research presented aims to provide a methodology and useful insights for the implementation of such programs along with their monitoring and analysis processes. In particular, the research illustrates the use of indicators to enable a comparison according to multiple criteria and different perspectives, in particular the societal one and the end-user's one
Calibration and uncertainty analysis for computer models – A meta-model based approach for integrated building energy simulation
No full textIn energy and environment field models are constructed, in general, based on well-defined physical phenomena and properties. Calibration and uncertainty analysis hold a particular interest because models
represent a simplification of reality and, therefore, it is necessary to quantify to what degree they are imperfect before employing them in design, prediction and decision making processes. Integrated building
energy models attempt to describe the effect of various internal and external actions (weather, occupancy, appliances, etc.) through physical relations (both algebraic and differential) and they are being
widely used to design and operate high performance buildings, which are an essential component of a global energy strategy to reduce carbon emission and fossil sources depletion. An approach oriented to
systems and able to integrate effectively field measured data and computer simulations for calibration in the modeling process has the potential to revolutionize the way buildings are designed and operated, and to stimulate also the development of new technologies and solutions in the field. The research presented in this paper aims to represent an initial step towards this integrated approach
Cost optimal analysis of heat pump technology adoption in residential reference buildings
No full textIn European Union (EU) buildings consume approximately the 40% of total primary energy. Heat pump (HP) systems have proven to be an efficient and economically viable alternative to conventional systems to provide heating and cooling services in buildings. An effective penetration of this technology in the built environment is critical to achieve the ambitious goals set by the recent EU Directives on energy efficiency and energy performance of buildings. Although this technology is very versatile, its optimal design and management are related to specific climate, operational and economic conditions. The research presented aims to evaluate the performance of technical solutions for heating and cooling in residential buildings, using a "reference building" methodology. The comparison involves performance indicators such as primary energy consumption, CO2 emission and net present cost.The potential improvements with respect to conventional baseline solutions are assessed and the performance gap between air-source and water-source HP systems is shown referring to realistic operational and climate conditions within the Italian territory. The research suggests the possibility of reducing this performance gap by concentrating future research effort on design and control optimization
A simplified model for the estimation of energy production of PV systems
No full textThe potential of solar energy is far higher than any other renewable source, although several limits exist. In detail the fundamental factors that must be analyzed by investors and policy makers are the cost-effectiveness and the production of PV power plants, respectively, for the decision of investment schemes and energy policy strategies. Tools suitable to be used even by non-specialists, are therefore becoming increasingly important. Many research and development effort have been devoted to this goal in recent years. In this study, a simplified model for PV annual production estimation that can provide results with a level of accuracy comparable with the more sophisticated simulation tools from which it derives is fundamental data. The main advantage of the presented model is that it can be used by virtually anyone, without requiring a specific field expertise. The inherent limits of the model are related to its empirical base, but the methodology presented can be effectively reproduced in the future with a different spectrum of data in order to assess, for example, the effect of technological evolution on the overall performance of PV power generation or establishing performance benchmarks for a much larger variety kinds of PV plants and technologies
Performance monitoring and modeling of an uncovered photovoltaic-thermal (PVT) water collector
No full textPVT technology presents many attractive features for a wide application in the building sector since it is able to produce electricity and thermal energy at the same time with better overall performances and reduced surfaces in comparison with the two separated solar technologies. However the effectiveness of the PVT modules is most evident when they are integrated in complex systems, capable of fully exploiting their multi-functionality (e.g. heat pump coupling, multi-storage interconnection, etc.). For that reason, the research work presents a mathematical model for energy simulation of PVT systems, which takes in account all factors and parameters involved in the energy performance of an uncovered hybrid collector; the model can be easily implemented in any performance calculation tool in order to carry out technical-economic assessment of PVT systems.The experimental calibration and validation of the proposed model was performed in outdoor conditions on a commercial PVT product, at the Test Facility of the Politecnico di Milano University, and finally the model was ran supposing the application in three different locations. The validation of the developed simulation model shows a good agreement with monitored data also if a mismatch occurred due to an assembling defect of the tested commercial PVT component
Thermal-electrical optimization of the configuration a liquid PVT collector
No full textThe study focuses on the optimal thermal and electrical configuration of hybrid Photovoltaic-Thermal (PVT) collectors. The electrical production of a PVT system is, in fact, highly affected by the temperature of the PV cells. In a PVT collector a temperature gradient exists along the absorber, so not all cells may be able to operate with the same electrical characteristics due to their temperature coefficient. In order to evaluate temperature distribution on solar
cells, thermal analysis has been carried out with computational fluid dynamic (CFD) software. The study was focused on two absorbers types, characterized by different designs: a serpentine tube absorber and a parallel tubes absorber. Starting from the thermal analysis, alternative electrical configurations were simulated in order to define the best solution to maximize as much as possible the photovoltaic performance
Optimization of solar thermal fraction in PVT systems
No full textOver the last years there has been a growing interest in hybrid Photovoltaic-Thermal (PVT) collectors for their applications in building integration. The hybrid systems integrate the features of the photovoltaic and the solar thermal (water or air) systems in one combined product/system.
The PV electricity production in a hybrid system could be significantly different from the one of a standard PV module because, mainly, cells temperatures change according to the amount of heat removed by the absorber of the PVT system and, moreover, to the insulation level of the PVT system. This last factor is related to many parameters,
among which it is possible to identify water flow rate and temperature, which are directly related to PVT plant configuration and size as a function of users heat demand.
Starting from these considerations, the aim of this paper is to calculate the optimal value of solar fraction f for hybrid PVT systems, under energetic end economic point of views, and to find a correlation between the percentage of heat demand covered by the PVT system and photovoltaic cells temperature. In fact, changes in solar fraction imply different average cells operating temperatures and consequently, variation in total energy efficiency. For this purpose,
simulations of liquid-based PVT systems for domestic application have been performed through TRNSYS energy simulation tools, carrying out subsequently a detailed energetic and economic analysis
District heating: results of a monitoring compaign in Lombardy Region
No full textUrban neighborhoods could represent an optimal scale for the implementation of innovative energy strategies.
However, barriers at the economic, regulatory and administrative level are still present. In this framework, it is important to operate on three levels of the energy system: by reducing energy demand; by optimizing generation and management system, and by integrating local renewable energy sources. In recent years, as a result of an important agreement with the Italian Ministry of Environment, Lombardy Region has supported numerous measures for energy
efficiency and renewable resources integration among its territory. The funding supported different actions such as improvements of the buildings envelope, substitution of old gas boilers for heat generation with more efficient components, integration of solar thermal systems in buildings, hydrogen and more sustainable mobility, and district
heating plants, which present contribution concerns. About district heating the incentives were provided within two different calls: one aimed at the creation of plants and district heating networks and another for the extension of existing systems. Main aim of the research is to evaluate effects, effectiveness, pros and cons of the several calls for funding; to that end a methodology was developed in order to collect the data and elaborate representative energy,
environmental and economic indicators. The most important characteristics, conditions and technical features of the considered plants are described in the present paper trying to provide information on the effectiveness of the supporting measures taken in order to orient future choices and to identify the most promising strategies and technologies for improving energy and environmental performances of communities. In particular present paper is
related to 10 district heating plants: 6 are based on biomass and located in mountain areas, 3 are based on natural gas and located in urban areas, while the last is connected to the urban waste to energy plant.
One of the important lesson is learned is that district heating (fuelled by biomass, fossil, waste and CHP or not) represents an innovative field of knowledge far from standard: in general each plant has to be evaluated on the basis of specify characteristics and it is very hard to find out average performances from the environmental and economic
point of view
- …
