Giuseppe Peter Vanoli

An evaluation of R22 substitutes performances regulating continuously the compressor refrigeration capacity

Abstract This paper presents the results of an experimental analysis which compares in terms of energetic performances the refrigeration capacity control obtained by means of a variable-speed compressor with the on/off control deriving from a classical thermostatic device. The compressor considered is semi-hermetic reciprocating and is a component of a vapour compression refrigeration plant subjected to a commercially available cold store. The compressor working with the fluids R22, R507 and R407C and designed for a revolution speed corresponding to the compressor supply current nominal frequency of 50 Hz, has been tested varying the frequency in the range 30–50 Hz. In this range, the most suitable working fluids proposed as substitutes of the R22 as the R407C (R32/R125/R134a 23/25/52% in mass), the R507 (R125/R143A 50/50% in mass) and the R417A (R125/R134a/R600 46.6/50/3.4% in mass) have been tested. The results show that, using the R407C, it is possible an average an electric energy consumption about 12% smaller when an inverter is employed to control the compressor refrigeration capacity instead of the thermostatic control which imposes on/off cycles on the compressor, working at the nominal frequency of 50 Hz. So the R407C confirms its superiority in comparison with the R417A and R507; only the R22 shows a better performance.

Transient heat transfer through walls and thermal bridges. numerical modelling: methodology and validation

The current advanced numerical codes for the energy audits carry out 0-dimensional simulation (i.e., one computational node representing the thermal zone), underestimating the effects of thermal bridges on the seasonal heating demand of buildings. The paper suggests a numerical resolution model, implemented in Matlab, aimed to be transferred in numerical engines for the hourly energy simulation. The proposed methodology solves common thermal bridges in buildings, evaluating their effects on the energy demand. Typical thermal bridges have been studied and implemented, analyzing the reliability of the methodology, in terms of accuracy, computational time, required sources, comparing the solutions with those derived by computational fluid dynamic codes. The method reveals very satisfactory results, both as regards the computational time and CPU sources required, as well as with reference to the reliability. Moreover, the solution stability is commonly very high, regardless the chosen computational time-step.

Mitigating the cooling need and improvement of indoor conditions in Mediterranean educational buildings, by means of green roofs. Results of a case study

Indoor overheating risk and increased energy demand for cooling are becoming more and more frequent in the building sector of the Mediterranean area. In detail, for the reduction of the energy consumption of educational buildings, characterized by high endogenous gains, the particular boundary conditions affecting their use should be taken in consideration, and thus schedules of occupancy, wide necessity of air-changes for air quality. This paper, with reference to a case study, proposes deep investigations aimed at optimizing the annual energy performance of an educational building of the University of Sannio, located in the Southern Italy. A numerical model of the building has been designed and validated according to monitored data. Starting from the present scenario, after a complete refurbishment of the building envelope, the potentialities of several typologies of green roofs - by considering also the implementation of the adaptive approach in the comfort standard - have been tested. The scope is the optimization of the energy demand for the annual microclimatic control, by avoiding an energy-intensive operation of the air-conditioning devices during the warm season.

Technical and economic analysis of green roofs to reduce building cooling needs

Several public/private institutions, at international and national levels, consider green roofs effective energy efficiency measures. A large feasibility study of their technical and economical profitability is proposed here. The main heat transfer phenomena and a brief literature state of the art are presented. Congruent with the cost-optimal approach, the economic indicators are described, as well as the physical set of equations for evaluating the energy performances of green roofs. Moreover, the case studies are shown by describing the various climates considered, energy and water costs, efficiency of power systems, emissions factors, and all parameters necessary for suitable feasibility studies. Various climates and building technologies are taken into account, as well as common typologies of extensive green roofs. The results show a relative feasibility of green roofs, when the watering costs are limited, and if the buildings are not properly insulated, so that the installation of greenery, combined with the added thermal insulation, provides energy savings for both heating and cooling. A final section proposes some considerations for improving the profitability of green roofs by adopting rainwater harvesting systems.

A low-cost HIL platform for testing professional refrigerators controllers

Abstract In this work, we present a Hardware In the Loop (HIL) platform for testing control strategies designed and implemented in a commercial electronic control unit for industrial refrigerators. The architecture structure consists of four elements: (i) a real-time processor, in which a detailed model of the refrigerator is implemented; (ii) the industrial control unit device under test; (iii) an Input/Output (I/O) hardware interface which allows data communication between the real-time processor (model) and the industrial device (control) and (iv) a power PC in order to display and save experimental results. Introducing the HIL methodology in the refrigerator industry could reduce electronic control unit testing costs and save time in the production stage because it is possible to verify the control strategy performances in realtime for several operating conditions and different refrigerator models avoiding expensive and time-consuming test bench procedures.

Miniaturization of Energy Conversion Systems: Energetic Analysis

A great number of research groups and manufacturers are involved in the development of micro energy conversion systems. In particular the analysis is focused on heat exchangers and it deals with several aspects, such as the physical principles regulating heat and mass transfer in microchannels and the production process itself. Many benefits are expected from the on going process, such as improvement of the heat exchange, improved performances with partial loads, the opportunity to use innovative materials. On the other hand this process, started within the industrial sphere, could be boosted by the necessity of less costly production processes, through the cost reduction for materials and power, and through economy of scale. This paper aims to confirm if the actual trend of miniaturisation drives to effective benefits in terms of energy saving. For this purpose various aspects influencing the efficiency of the energy conversion devices are considered. For the efficiency of the global system (user, device and connection), special attention is paid to find the optimal trade off between the advantages due to the reductions of ducting and cycling losses and the disadvantages due to the negative influence of the size on the system’s performance.Copyright

5.21 Energy Management in Hospitals

Hospitals are complex structures that require the highest energy intensity of the building sector. Thus, in both cases of new construction and retrofit, their proper energy design and management are a critical issue, because these must consider all levers of energy performance, from the building envelope to the operation and efficiency of energy systems. Furthermore, different objective functions to minimize can be pursued, for example, energy consumption, thermal discomfort, lifecycle costs, and polluting emissions. Definitely, comprehensive approaches are required to address the aforementioned issues. The chapter provides an overview of these approaches by showing the application to different case studies.

Artificial Neural Networks for Predicting the Energy Behavior of a Building Category

Abstract The reliable assessment of building energy performance requires significant computational times. The chapter handles this issue by proposing an original methodology that employs artificial neural networks (ANNs) to predict the energy behavior of all buildings of an established category. The ANNs are generated in MATLAB by using EnergyPlus simulations for testing and training purposes. The inputs are properly set by means of a thorough preliminary sensitivity analysis. The final aim is a reliable assessment of the global cost for space conditioning as well as of the potential global cost savings produced by energy retrofit measures for each category’s building. The benefit is a huge reduction of computational times compared to standard reliable simulation tools. Definitely, this can support the diffusion of rigorous approaches for cost-optimal energy retrofits. Beyond the presentation of the methodology, this is applied to the office building stock of South Italy built in the period 1920–1970. The results show a high ANN reliability compared to EnergyPlus simulations, with regression coefficients ( R ) always higher than 0.98.

Cost-Effective Refurbishment of Italian Historic Buildings

Abstract This chapter investigates strategies for approaching the energy refurbishment of historic buildings, by proposing, beyond a general methodology aimed at guaranteeing feasibility of the design, its application to two cases studies in the context of South Italy, in a typical Mediterranean climate according to the Koppen classification. According to the latest international guidelines in matter of building energy efficiency and future trends, by 2020, a great effort should be applied to both new constructions and building refurbishments, to achieve goals of nearly zero-energy impacts or very low energy demand. Of course, the energy refurbishment of architectures characterized by historical or artistic values should not determine damage of the valuable peculiarities. In this study, by means of the proposed case studies, and thus an admirable Italian building, examples of an approach toward cost-effective and architecturally compatible actions are proposed, according to the European methodology of cost optimality. Moreover, by comparison with the feasible refurbishment of an existing building, the difference in energy retrofit designs of historical or modern edifices is evidenced. The proposed case studies are an educational ancient palace built beginning in the 12th century and, as an existing building, a railway station located in the same city. In both cases, replacement of components of thermal envelope and active energy systems will be applied, by evidencing that, based on the building peculiarities, technologies, architectural values, and kinds of loads, different boundary conditions imply different cost-optimal energy conservation measures.

Cost-Effective Energy Refurbishment of Health Care Facilities in Heating Dominated Climates of Italian Backcountry. The Case Study of the Hospital Veneziale of Isernia

Maximizing energy efficiency within hospitals and healthcare facilities is a major challenge for sustainable development and energy saving objectives. In this study, the case study of the public hospital of Isernia (Italian backcountry city) is proposed, being typical of the hospital building stock developed in reinforced concrete all around Italy in the last 40 years. Starting from deep on-site investigations, based on direct surveys and documents, a transient energy model has been developed and calibrated, in order to reproduce the present scenario. This, in a next phase, has been modified for proposing a multi-target optimization of energy performances, by taking into consideration all main uses (heating, cooling, ventilation, lighting, domestic hot water), by refurbishing the building envelope, active energy systems and providing energy conversion from renewables. The whole energy retrofit, formulated on the basis of a multi-stage optimization problem, resulted technically efficient and economically feasible. Moreover, the peculiarities of the case study and of the method make that investigation repeatable with reference to both studying approach and outcomes.