1,721,005 research outputs found
Performance analysis of a rooftop, air-to-air heat pump working with CO2
No full textThe air-conditioning sector for large buildings and shopping centers is developing a growing interest in rooftop heat pumps due to their easy installation. Instead of the application of HFC refrigerants, carbon dioxide (CO2) could be an interesting perspective in this sector for environmental reasons. This work presents new performance data of an air-to-air heat pump roof-top system working with a trans-critical carbon dioxide cycle during the heating season. In particular, the experimental results showed how the heating power and the coefficient of performance are affected by the air temperature at the inlet of the gas cooler and by part load working conditions. A thermodynamic analysis pointed out the direct and indirect effects of fans speed and air flow temperatures on the performance, defining a performance map and the optimal range of application of such systems. © 2014 Elsevier Ltd. All rights reserved
Energy Planning of Renewable Energy Sources in an Italian Context: Energy Forecasting Analysis of Photovoltaic Systems in the Residential Sector
Full text linkSolar photovoltaic systems will play a key role in the country’s energy mix thanks to their ability to meet increasing energy needs while reducing greenhouse gas emissions. Despite the potential of solar photovoltaic energy, several criticalities remain, such as the intermittent nature and the need for significant land use for its implementation. In this regard, this work aimed at evaluating the photovoltaic potentiality in a national context by 2030 and 2050, considering only installations on the roof surfaces of existing buildings, i.e., without consuming additional land. This study has allowed the answering of three key points: (i) the roof surface could represent a valuable and alternative solution for new installations, since it could amount to around 450 km2, (ii) the national target cannot be reached by only using installations on existing buildings, although some regions could get close to the target by 2050, and (iii) long-term energy incentives should be implemented branching out to each national region, considering their photovoltaic potential. Finally, a regional potential index was also defined, capable of evaluating the photovoltaic potential in each region, helping policymakers to adopt the most suitable energy strategies
Effect of growth regulator on flower differenzazion and yield in zucchini(Cucurbita pepo L.)grown in protected cultivation
No full textMessa in funzione, analisi sperimentale e caratterizzazione dell'innovativo impianto di solar heating and cooling realizzato a servizio dell'Edificio F92
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Development and experimental analysis of CO2 heat pump for DHW production
No full textThis study presents results of two experimental campaigns on a 30 kW air source CO2 heat pump prototype for domestic hot water (DHW) production. The prototype has been realized, tested and optimized within the NxtHPG (Next Generation of Heat Pumps working with Natural fluids), 7th Framework European project. The project aims to reach higher efficiency (10-20% SPF improvement) and lower Carbon footprint (20% lower TEWI) than the current state of the art HFCs/HFOs or Sorption heat pumps, with costs very similar or slightly higher than the latter systems (10%). The tested CO2 heat pump has been designed to produce water at 60°C/80° C starting from a return temperature in the range 10°C/55°C (winter) and 20°C/55°C (summer). First experimental campaign was performed to determine possible issues and potential improvements to be applied on this prototype. In the second experimental campaign, after the required modifications of the prototype, the measured performance, COP and heating capacity, have been in line with objectives. In addition, useful information have been obtained to make additional modifications to further improve the heat pump performance. © 2016, International Institute of Refrigeration. All rights reserved
Sowing time, gibberellic acid treatments and of "seed" propagated artichoke cultivars
No full textTwo trials were conducted during the period 1989–1991 in southern Italy with the aim of determining the effect of GA3 on new cultivars of seed-propagated artichokes planted during the summer months. In the first experiment the cv. 044 was direct-seeded at the end of August. Single and multiple applications of GA3 were made 90, 120 and 150 days after sowing (DAS).
In the second experiment the cv. 044 and F1 hybrids '137', '223' and '271' were seeded in June, July and August in a cold greenhouse and the seedlings were planted into the field about 40 DAS. The GA3 was applied three times at three week intervals once the plants had 10 – 12 leaves. Single or double application of GA3 90 or 120 DAS provoked an earlier and higher yield.
GA3 applied to plants transplanted in July provide a high yield and earliness. The most responsive cultivar to GA3 was the '271' because the growth regulator was very effective in enhancing head production and in increasing marketable yield
Progettazione costruttiva di un prototipo di pompa di calore a CO2 (R744) invertibile del tipo aria-aria e realizzazione della facility di prova
Full text linkQuesta relazione riguarda le attività svolte nell’ambito dell’accordo di collaborazione tra ENEA e l’Università degli studi di Napoli Federico II, Dipartimento di Energetica, Termofluidodinamica Applicata e Condizionamenti Ambientali (DETEC) per una attività di ricerca dal titolo “Progettazione costruttiva di un roof‐top a pompa di calore ad R744 (CO2)”, a sua volta rientrante nell’ accordo di programma MSE‐ENEA sulla Ricerca di Sistema Elettrico, Piano Annuale di Realizzazione 2011. L’ENEA ha poi seguito tutta la parte di progettazione e realizzazione della facility di prova della macchina prototipo.
L’applicazione considerata è pensata per la climatizzazione sia estiva che invernale di grandi locali commerciali; inoltre prevede l’utilizzo di sbrinamento a gas caldo in diverse soluzioni circuitali in modo da consentire il funzionamento tramite il solo allaccio alla rete di distribuzione dell’energia elettrica. Il sistema è stato progettato nei suoi componenti e successivamente tramite la modellazione fisica dei singoli componenti è stato sviluppato un codice di calcolo operante in matlab (e riportato in appendice) che
ha consentito la previsione del funzionamento in condizioni diverse da quelle di progetto, mostrando prestazioni previsionali soddisfacenti. Infine sono riportati anche i risultati, anch’essi soddisfacenti, di alcuni test preliminari svolti nell’ultima settimana del mese di luglio 2012 sul prodotto assemblato e le foto della posa in opera presso la sede di ENEA – Casaccia in Roma avvenuta nella prima settimana di settembre
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