1,941 research outputs found
Israel, ISIS and the Iran Nuclear Deal: The Comeback of the Middle East in the 2016 American Presidential Campaign
No full textThis chapter investigates the relevance of the Middle East issue in the 2016 American presidential campaign. After describing the early campaign’s international context and the past and current public opinion’s perception on foreign policy, the article analyzes the primary candidates’ proposal on Middle East and other linked topics. The whole presidential primary campaign on both sides was full of references to the Middle East, often linked to other adjacent topics such as immigration and terrorism. Republicans are usually favoured by voters on foreign politics while Democrats are preferred when it comes to welfare. As shown by electoral manifestos and TV debates, the Middle East issue remained central also in the Clinton v. Trump final race. However, opinion polls and media coverage explained how the 2016 presidential campaign will probably be remembered for the harsh personal attacks exchanged against each other by the two nominees. The unexpected Donald Trump’s victory was certainly not driven by his statements on Middle East, but his presidency will probably be characterized by a complete new approach towards that area
Business Cycle in a Macromodel with Oligopoly and Agents’ Heterogeneity: An Agent-Based Approach
No full textThis paper introduces a macromodel with oligopoly and entry/exit in a
framework where individuals are heterogeneous in their budget constraints, since
they can be workers, new entrant entrepreneurs, incumbent entrepreneurs or unemployed
and may change their status due to a stochastic process, associated to entry and
exit. Agents’ heterogeneity is explicitly modelled in the aggregate demand, that also
accounts for the income distribution. Heterogeneity also plays a relevant role in the
process of entry/exit in the goods market, which interacts with the labour market and
generates macroeconomic fluctuations. As shown in the agent-based numerical simulation,
the model provides a newinterpretation of the busines
A model for the simulation of the gas cleaning system in a syngas-fed CHP plant
No full textBiomass gasification is a promising solution for power generation and combined heat and power (CHP). The conversion to syngas allows for a more efficient use of biomasses with low pollutant emissions in internal combustion engines. Small-scale plants do not have the expected diffusion, mainly due to a lack of experimental experience. To overcome this drawback, accurate simulation models may be useful for the diagnostics and control of these systems. A commercial-grade system, fueled by syngas from lignocellulosic woodchips, has been installed in the Science and Technologies Campus of the University of Parma, within the SYNBIOSE project. The scope is to acquire knowledge to improve small-scale gasification and CHP plants for the tertiary sector. The project includes the development of a simulation model for system diagnostics. The syngas cleaning line is a critical part of CHP plants. It must remove any solid/liquid fraction from the raw syngas, as produced by the gasifier, yielding the clean gas. To this extent, a MATLAB®/Simulink® model has been developed and is described in the paper. It is able to predict the operation according to the inputs and operating parameters, e.g. considering fluid inlet characteristics and fouling. Model analysis showed that the calculation results are consistent with the physical behavior of the plant, providing a first validation of the proposed model. The model can be useful for system simulation and diagnostics
Climate Influence on Seasonal Performances of Air-to-water Heat Pumps for Heating
No full textAbstractA mathematical model for the evaluation of the seasonal performances of electric air-to-water heat pumps for heating is used to analyze the efficiency of on-off heat pumps, multi-compressor heat pumps and heat pumps with inverter compressor, integrated by electric heaters as back-up system, in the service of several buildings located in different Italian climates.The paper points out the importance of a good dimensioning of the heat pump as a function of the building energy signature and of the climate of the city where the building is placed, in order to enhance the system seasonal efficiency
Annual Performances of Reversible Air Source Heat Pumps for Space Conditioning
No full textAbstractThe paper presents the results obtained by a numerical simulation of a heating and cooling system based on a reversible air-to-water electric heat pump and electric resistances as back-up. According to the procedure suggested by the current standards EN 14825 and UNI/TS 11300-4, by using the bin method the influence of outdoor conditions and of the typology of heat pump installed has been investigated by determining the value assumed by the seasonal coefficient of performance (SCOPon), the seasonal efficiency ratio (SEER) and the annual performance factor (APF). The numerical results allow discussing the rules for an optimal heat pump sizing in a fixed site
Valutazione delle prestazioni energetiche ed ambientali di impianti basati su pompe di calore operanti con diversi fluidi refrigeranti
No full textIn questo lavoro sono state valutate attraverso il software TRNSYS le prestazioni energetiche ed ambientali ottenibili da un impianto di tipo idronico, basato su una pompa di calore elettrica ed accoppiato ad un edificio mono-familiare di recente costruzione situato a Padova. In particolare, sono state considerate due tipologie di pompa di calore, una macchina aerotermica ed una geotermica, entrambe operanti con fluidi refrigeranti alternativi: R-410A e R-454B.
Le simulazioni numeriche effettuate hanno confermato come l’utilizzo di una pompa di calore geotermica permetta di incrementare le prestazioni energetiche complessive dell’impianto di circa il 10%, a parità di refrigerante. L’impatto ambientale delle configurazioni impiantistiche studiate è stato valutato per mezzo del TEWI (Total Warming Equivalent Impact). L’utilizzo del refrigerante R-454B comporta da un lato un lieve calo delle prestazioni energetiche complessive dell’impianto, pari al 2-3% su base annuale, mentre consente di ottenere una marcata diminuzione del TEWI. Considerando infatti l’attuale fattore di emissione italiano dell’energia elettrica prelevata da rete, le emissioni totali lungo l’intero ciclo di vita della pompa di calore calano di circa il 25% grazie all’utilizzo del fluido a basso GWP. Tuttavia, seguendo l’attuale trend di riduzione del fattore di emissione ed assumendolo nullo al 2050, tale riduzione può arrivare in prospettiva fino all’80%, azzerando così le emissioni indirette di CO2 dell’impianto
Modellazione dinamica di un impianto solare termico per il riscaldamento di una piscina scoperta
No full textIl presente lavoro analizza il dimensionamento di un sistema solare di riscaldamento per piscine scoperte. Attraverso un modello dinamico dell’impianto realizzato in ambiente Matlab/Simulink viene mostrato come il dimensionamento dell’impianto solare dipenda dalla tipologia di pannello solare termico utilizzata. Il modello permette di apprezzare l’influenza dell’inerzia termica dell’acqua della piscina e dei diversi termini di dispersione sulla performance energetica stagionale del sistemaThis work describes the sizing of a solar heating system for outdoor swimming pools. Through a dynamic model of the system implemented in Matlab/Simulink environment is shown as the sizing of the system depends on the characteristics of the selected solar collectors. The model allows to appreciate the influence of the thermal inertia of the pool water and of the heat losses on the seasonal energy performance of the syste
Design rules for the optimal sizing of a hybrid heat pump system coupled to a residential building
No full textNowadays the use of heat pumps is spread widely in new and refurbished high-efficient buildings. Heat
pumps can be very efficient but their energy performance is influenced by the temperature of their external
thermal reservoir which can be unstable during the heating season (i.e. outdoor air) and characterized by low
values. For this reason, the thermal capacity of the heat pump decreases in the colder days and in order to match
the maximum heating load of a building the unit must be slightly oversized. A suitable solution to avoid the energy
losses due to an excess of on-off cycles during the milder part of the season is the adoption of a hybrid system,
consisting of a heat pump, sized to partially cover the peak load of the building, coupled to a second heat
generator (back-up device). The aim of this paper is to assess the influence of the heat pump sizing, the unit
cycling losses and the typology of back-up system on the seasonal performance of a heating plant based on a
hybrid generator obtained by coupling a single-stage on-off air-to-water heat pump to a back-up device (electrical
heater or gas boiler). In this work, the dynamic model of the hybrid heat pump system is presented; several
simulations were performed to assess the seasonal energy performance of the system coupled to a single-family
house located in Bolzano (Italy) and to compare it with those of monovalent heating systems based on an air-towater
heat pump or a gas boiler only. The analysis enables to evaluate the energy savings achievable by
employing a hybrid system in which the generators can work in parallel or alternatively and to study the influence
of the cut-off temperature on the seasonal performance of the system. Results point out that hybrid systems can
be a suitable solution to achieve significant energy savings with respect to the classical monovalent systems.
More in detail, the largest seasonal efficiency was obtained by selecting a heat pump sized to cover the half of
the building peak load and by setting a control logic in which back-up and heat pump work in parallel: the
introduction of a cut-off temperature larger than the design external temperature is not beneficial. It is
demonstrated that an energy savings close to 16% can be achieved by adopting a hybrid system (air-to-water
heat pump + gas boiler) if compared to a traditional heating system based on a single gas boiler, even in
presence of an undersized heat pump
Influence of sizing strategy and control rules on the energy saving potential of heat pump hybrid systems in a residential building
No full textHybrid heat pump systems are a suitable solution to mitigate the well-known disadvantages of air-source heat pumps, such as energy losses linked to defrost cycles and a significant reduction of their heating capacity during the most severe part of the season. In hybrid systems the heat pump is sized to satisfy only a fraction of the building peak load and is coupled to a second heater (back-up device), which helps the heat pump during the coldest part of the winter. In this paper, a series of dynamic simulations has been performed to calculate the seasonal performance of hybrid systems based on an air-to-water heat pump and to assess the optimal configuration of the system. Results point out that the energy performance of these systems strongly depends on the heat pump sizing, the back-up device typology and the control algorithm used for the activation of the heat generators. It is demonstrated that the adoption of hybrid systems in which the heat pump is coupled to a gas boiler allows to obtain relevant primary energy savings. The overall seasonal efficiency can be increased up to 6% and 22%, if compared to monovalent systems respectively based on a heat pump or a gas boiler, only if the heaters are activated following an alternative operating mode, with a cut-off temperature selected between the design and the bivalent temperature. On the contrary, if the back-up device of the hybrid system is an electric resistance, the heaters have to work in parallel during the whole heating season and the only achievable advantage is that the heat pump can be slightly under-sized with respect to the nominal building load
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