LIFE CYCLE ASSESSMENT OF SOLAR COMMUNITIES: A SCENARIO ANALYSIS

The study proposes the comparisonof the life cycle performances of two different energy systems aimed at covering the needs of a large mixed-mode community, in Calgary (Canada). The two systems investigated are a“conventional” one, using heat pumps for heating, cooling and domestic hot water, and another one widely deploying solar thermal panels as well as a district heating infrastructure and a borehole seasonal thermal storage. The analysis is based on the LifeCycle Assessment (LCA) methodology and includes the stages of raw materials and energy supply, system manufacturing, use stage of the systems, generation and use of energy on-site, maintenance and components’ substitution, and explo…

Use of HFC fluids as suitable replacements in low-temperature refrigeration plants

An experimental investigation of the performance of a low-temperature refrigerating unit working with R22 and a comparison of its performance when operating with replacement HFC fluids in accordance with the European Regulation CE-1005/2009 are presented in this paper. Plant working efficiency was tested with R22, as baseline, and then compared with four different HFC fluids: R413A, R417A, R422A and R422D. The refrigerating unit was a vapour-compression plant equipped with a reciprocating double-cylinder compressor able to keep the cold room at -20ºC. Lower values of the temperature at the end of compression and polytrophic exponent can be achieved with the HFC tested. Substituting the R22 …

RESEARCH AND DEVELOPMENT ON HEAT PUMPS AT DEAF, PALERMO UNIVERSITY, ITALY

A CCHP system fed by low enthalpy sources in Mediterranean area

Climate change and energy consumption increasingly call for a better use of energy sources. Renewable sources are still growing in the power production of many countries, so leading to the reduction of CO2 emissions. Further restrictions will be applied to the use of fossil fuels with a lot of consequences; for example, major German cities such as Stuttgart, Dusseldorf and Hamburg are all contemplating bans related to diesel pollution, and on the other hand some of the biggest car producers - FCA, Toyota, etc. - are planning to stop the diesel engines production in a few years. At the same time, some restrictions are applied also to many refrigerating fluids, in order of firstly limiting th…

Modelling heat transfer-controlled cooling and freezing times: a comparison between computational values and experimental results

Modelling of heat transfer-controlled cooling and freezing time predictions are very important for a good preservation of foodstuffs. In that regard, we used a computer code based on the finite-element method that allowed us to analyse the phase-change of various foodstuffs during their freezing. The model was exercised to predict process times. The results can be used to design high efficiency plants. In this work, the results predicted by the FEM program are compared with the experimental values given in technical literature.

Performance Enhancement of Vapour-Compression Refrigeration Systems Using Nanoparticles: An Experimental Study

In recent years, the development and characterization of new refrigerants with higher energetic efficiency have gained considerable interest [1], with a particular emphasis on the energetic performance of suitable replacements. Nanofluids have been proposed as possible alternative due to their role in enhancing the thermophysical proprieties of traditional refrigerants [2]. The comprehensive review in [2] suggests that thermal conductivity of nanofluid increases with temperature and volume concentration, but it is dependent on nanoparticle size distribution; specific heat is also increased if nanoparticles are added to the refrigerant.

Estimating the temperature evolution of foodstuffs during freezing with a 3D meshless numerical method

Abstract Freezing processes are characterised by sharp changes in specific heat capacity and thermal conductivity for temperatures close to the freezing point. This leads to strong nonlinearities in the governing PDE that may be difficult to resolve using traditional numerical methods. In this work we present a meshless numerical method, based on a local Hermite radial basis function collocation approach in finite differencing mode, to allow the solution of freezing problems. By introducing a Kirchhoff transformation and solving the governing equations in Kirchhoff space, the strength of nonlinearity is reduced while preserving the structure of the heat equation. In combination with the hig…