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Abstract: The optimization of design and operation of trigeneration plants for civil applications is a very complex task, because of the large number of internal and external variables affecting the energetic and economic results that may be achieved. Further, energy-saving and profit-oriented optimization processes usually lead to different solutions, in terms of plant lay-out, optimal size of components and operation strategy. Thermoeconomic methodologies are very effective theoretical structures for the optimization of industrial energy-systems characterised by regular energy-demand profiles; however, they are hard to use when approaching civil applications and energy systems in unsteady operating-conditions. In this paper, the potential of thermoeconomics for the analysis of CHCP applications in buildings is explored; two main procedures to address the problem are presented, a simplified design optimization and a detailed integrated optimization of plant lay-out and operation. The former approach, based on the use of aggregate consumption data, is described more in detail and finally applied to a trigeneration plant serving a 300-bed hospital, situated in a Mediterranean area; the results are finally compared with those available in the literature and determined by using demand cumulative curves or numerical methods. [Copyright &y& Elsevier]

Aerosol optical depth and Ångström exponent were obtained from multi filter rotating shadowband radiometer (MFRSR) observations carried out at the island of Lampedusa, in the Central Mediterranean, in the period July 2001-September 2003. The average aerosol optical depth at 495.7 nm, τ , is 0.24±0.14; the average Ångström exponent, α, is 0.86±0.63. The observed values of τ range from 0.03 to 1.13, and the values of α vary from -0.32 to 2.05, indicating a large variability in aerosol content and size. In cloudfree conditions, 36% of the airmasses come from Africa, 25% from Central-Eastern Europe, and 19% from Western France, Spain and the North Atlantic. In summer, 42% of the airmasses is of African origin. In almost all cases African aerosols display high values of τ and low values of α, typical of Saharan dust (average values of τ and α are 0.36 and 0.42, respectively). Particles originating from Central- Eastern Europe show relatively large average values of τ and τ (0.23 and 1.5, respectively), while particles from Western France, Spain and the North Atlantic show the lowest average values of τ (0.15), and relatively small values of α (0.92). Intermediate values of α are often connected with relatively fast changes of the airmass originating sector, suggesting the contemporary presence of different types of particles in the air column. Clean marine conditions are rare at Lampedusa, and are generally associated with subsidence of the airmasses reaching the island. Average values of τ and τ for clean marine conditions are 0.11 and 0.86, respectively. The largest values of α (about 2) were observed in August 2003, when large scale forest fires in Southern Europe produced consistent amounts of fine combustion particles, that were transported to the Central Mediterranean by a persistent high pressure system over Central Europe. Smoke particles in some cases mix with desert dust, producing intermediate values of α. The seasonal distribution of the meteorological patterns over the Mediterranean, the efficiency of the aerosol production mechanisms, and the variability of the particles' residence time produce a distinct seasonal cycle of aerosol optical depths and Ångström exponent values. Particles originating from all sectors show a summer maximum in aerosol optical depth. The summer increase in optical depth for European aerosols is linked with an increment in the values of α, that indicates an enhancement in the number of fine particles. The summer maximum of τ for African particles is associated with a weak reduction in the Ångström exponent, suggesting an increase in the total number of particles and a relatively more intense transport of large particles. The observations were classified according to the aerosol optical properties, and two main classes have been identified: desert dust and biomass burning/urban-industrial aerosols. Values of τ and α averaged over the whole observing period are 0.37 and 0.15 for desert dust, and 0.27 and 1.77 for urbanindustrial/ biomass burning aerosols. [ABSTRACT FROM AUTHOR]

The effects of different physical and biogeochemical drivers on the carbonate system were investigated in a semi-enclosed coastal area characterized by high alkalinity riverine discharge (Gulf of Trieste, Northern Adriatic Sea, Mediterranean Sea). Our 2-year time-series showed that a large part of the seasonal carbonate chemistry variation was controlled by the large seasonal change of seawater temperature, though air-sea CO 2 exchange, biological activity (primary production-respiration), and riverine inputs also exerted a significant influence. With the exception of summer, the Gulf of Trieste was a sink of atmospheric carbon dioxide, showing a very strong CO 2 fluxes from atmosphere into the sea (−16.10 mmol m −2 day −1 ) during high wind speed event of north easterly Bora wind. The CO 2 influx was particularly evident in winter, when the biological activity was at minimum and the low seawater temperature enhanced CO 2 solubility. During spring, the drawdown of CO 2 by primary production overwhelmed the CO 2 physical pump, driving a significant decrease of dissolved inorganic carbon (DIC), [CO 2 ], and increase of pH T25 °C . In summer the primary production in surface waters occurred with the same intensity as respiration in the bottom layer, so the net biological effect on the carbonate system was very low and the further reduction of seawater CO 2 concentration observed was mainly due to carbon dioxide degassing induced by high seawater temperature. Finally, during autumn the respiration was the predominant process, which determined an overall increase of DIC, [CO 2 ], and decrease of pH T25 °C . This was particularly evident when the breakdown of summer stratification occurred and a large amount of CO 2 , generated by respiration and segregated below the pycnocline, was released back to the whole water column. Local rivers also significantly affected the carbonate system by direct input of total alkalinity (A T ) coming from the chemical weathering of carbonate rocks, which dominate the river watershed. Our finding clearly demonstrates a high A T concentration in low salinity surface waters (A T max = 2742.8 μmol kg −1 ) and a negative A T -salinity correlation. As a result the Gulf of Trieste revealed a low Revelle factor (10.1) and one of the highest buffer capacities of the Mediterranean Sea (ß DIC = 0.31 mmol kg −1 ), which allows the system to store a significant amount of atmospheric CO 2 with a small decrease of seawater pH. [ABSTRACT FROM AUTHOR]

This paper investigates the integration of solar and geothermal energy in a novel polygeneration system producing simultaneously: electricity, thermal energy, cooling energy and fresh water. The polygeneration system under analysis includes concentrating photovoltaic/thermal solar collectors (CPVT), a Geothermal Well (GW) a multi-effect distillation (MED) system for seawater desalination, a single-stage LiBr–H 2 O absorption chiller and additional components, such as: storage tanks, heat exchangers and balance of plant devices. The CPVT produces simultaneously electrical energy and thermal energy, at a maximum temperature of about 100 °C. The electrical energy is delivered to the grid, whereas the thermal energy can be used for different scopes. First, the thermal energy can be used for heating purposes and/or Domestic Hot Water production. As an alternative, solar thermal energy can be used to drive an absorption chiller, producing chilled water for space cooling. Finally, solar energy, in combination with the thermal energy produced by low-enthalpy (about 80 °C) geothermal wells, may be used by the MED system to convert seawater into desalinated water. Geothermal energy is also used to produce Domestic Hot Water at 45 °C. The system is dynamically simulated by means of a zero-dimensional transient simulation model. The simulation model also includes detailed control strategies, for the management of the different technologies included in such a complex system. The system is assumed to be operated in some of the several small volcanic islands in the Mediterranean Sea, assuming Pantelleria (Trapani, Italy) as main case study. Here, the availability of solar and geothermal energy is high whereas the availability of fresh water is scarce and its cost consequently high. Results show an excellent energetic performance of the system under investigation. From the economic point of view, the profitability of the system dramatically increases when user Domestic Hot Water demand is high. [ABSTRACT FROM AUTHOR]

Abstract: Measurements of spectral actinic flux were performed at the ENEA Station for Climate Observations on the island of Lampedusa, in the central Mediterranean, during several periods in 2003, 2004, 2006 and 2008 with a METCON diode array spectrometer. The ozone photolysis frequency, J(O1D), was calculated from the spectral actinic fluxes. Actinic fluxes determinations were complemented with measurements of total ozone and aerosol optical depth, made with a Brewer spectrophotometer and a multi-filter rotating shadowband radiometer, respectively. As expected, J(O1D) shows a strong dependency on total ozone. The behaviour of J(O1D) was examined at fixed values of total ozone and solar zenith angle; a significant dependency on the aerosol optical depth emerges. The dependency on the aerosol optical depth at 416 nm appears to be linear, and weakly dependent on the total ozone value. The photolysis frequency amplification factor for aerosol is between 0.09 and 0.17 at 30°, and between 0.12 and 0.22 at 60° solar zenith angle, depending on total ozone. Day-to-day changes in AOD produce larger effects on J(O1D) than day-to-day changes in total ozone in summer, and comparable effects in spring. Ozone changes are dominant in autumn and winter. To our knowledge, this is the first attempt to characterize the influence of aerosol optical depth on J(O1D) from a relatively large dataset. [Copyright &y& Elsevier]