1,721,009 research outputs found
Performance assessment of photovoltaic, ground source heat pump and hydrogen heat generator in a stand-alone systems for greenhouse heating
No full textThe energy balance is one of the most important factors of the commercial greenhouses. Diesel, LPG and natural gas are generally used as fuel for greenhouses heating. A great amount of scientific research are focused on innovative renewable energy systems in the agricultural sector. The goal is to reduce the use of fossil sources and to change the energy mix of the traditional greenhouses heating system. However, the renewables energies sources and the micro-generation systems still play a niche role in the energy panorama, mainly due to the intermittence of the energy production. In particular, for the solar energy systems used for greenhouse heating applications, the energy produced must be storage and used at night. Stand-alone energy storage systems is necessary to overcome the discontinuity in the energy production and consumption. In this paper, the performance of the stand-alone renewable energy systems for greenhouse heating during the winter season was analyzed. The aims of this research is to compare the energies efficiency of two different stand-alone systems based on hydrogen. The first systems consist of a photovoltaic array connected to an hydrogen electrolyzer, a pressure tank, a fuel cell and a ground source geothermal heat pump. The second system is analogous to the first but a direct air hydrogen burner was used instead to the fuel cell and the heat pump. The second system was designed in order to shorten the energies chain and to simplify the plant. A performance analysis ware conduct in order to define the energy efficiency and the power productions of the both systems. The results show that the heating power produced by the first system is greater than 30% compared to the second one if the hydrogen production and consumption of the two solutions are the same and the coefficient of performance of the heat pump is 5. Furthermore, the first system increasing the greenhouse temperature by 6°C to 10°C compared with the ambient conditions, while the second system by 3°C to 7°C
La revisione delle trattrici e delle macchine agricole
Full text linkL’entrata in vigore del “Testo Unico sulla salute e sicurezza nei Luoghi di Lavoro” (D.lgs. 81/08) ha certamente prodotto notevoli cambiamenti rispetto
al passato nella mentalità dei lavoratori e oggi le tematiche legate alla sicurezza sono considerate essenziali per la qualità della vita. Nonostante ciò, numerosi
incidenti avvengono in tutti gli ambienti di lavoro senza alcuna distinzione: edilizia, industria, terziario, artigianato; il settore agricolo non è esente soprattutto per l’enorme utilizzo di macchine di diversa tipologia e tecnologia che rende questo comparto ad elevato indice infortunistico
Dal fotovoltaico al termico
No full textUn gruppo di ricerca dell’Università di Bari ha messo a punto un sistema di produzione energetica integrato per il condizionamento delle serre. Da ogni kWh di energia elettrica, attraverso un impianto geotermico, si ottengono dai 3 ai 6 kWh di calor
Re-Use of Agricultural Biomass for Nurseries Using Proximity Composting
No full textThe purpose of this study is to provide a proximity composting plant at a nursery.
The disposal of pruning is an economic burden for farms. This paper shows that the
reuse of pruning for composting and producing substrates for the nursery is an
efficient procedure to reduce the environmental load and obtain quality ornamental
plants. After a spatial analysis on the availability of pruning in a sample area, we
have arranged, at a research partner’s nursery, a plant for proximity composting.
Using the collected data, a life cycle assessment (LCA) analysis was prepared for
the compost and substrates. Agronomic tests, whose results will be published later,
were conducted on four Mediterranean ornamental species. A comparison between
the agronomic and environmental results shows that proximity composting is a
convenient practice that significantly reduces the environmental load of substrates
Dal fotovoltaico al termico
No full textUn gruppo di ricerca
dell’Università di Bari ha messo a punto un sistema di
produzione energetica integrato per il condizionamento delle
serre. Da ogni kWh di energia
elettrica, attraverso un impianto geotermico, si ottengono dai 3 ai
6 kWh di calor
Energy efficiency analysis of a hydrogen and geothermal stand-alone system for greenhouses heating
No full textThis study investigates the performance characteristics of a hydrogen and geothermal stand-alone system for greenhouses heating. The systems consist of photovoltaic panels connected to an electrolyzer that, during the daylight hours, produce hydrogen and then it is stored in a pressure tank. However at night, thank to a fuel-cell, the hydrogen was converted to electric energy in order to feed a ground source geothermal heat pump for greenhouse heating. The following conversion energy efficiencies factor of each system were measured: photovoltaic panels, 13%, electrolyzer, 48%, fuel-cell, 41% and finally, the coefficient of performance of geothermal heat pump of 5, and then the overall system efficiency, starting from the amount of solar energy available during the daylight hours, was of 12.8%
Study of a pilot photovoltaic-electrolyzer-fuel cell power system for a geothermal heat pump heated greenhouse and evaluation of the electrolyzer efficiency and operational mode
No full textThe intrinsic factor of variability of renewable energy sources often limits their broader use. The photovoltaic solar systems can be provided with a power back up based on a combination of an electrolyzer and a fuel cell stack. The integration of solar hydrogen power systems with greenhouse heating equipment can provide a possible option for powering stand-alone greenhouses. The aim of the research under development at the experimental farm of Department of Agro-Environmental Sciences of the University of Bari “Aldo Moro” is to investigate on the suitable solutions of a power system based on photovoltaic energy and on the use of hydrogen as energy vector, integrated with a ground source heat pump for greenhouse heating in a self sustained way. The excess energy produced by a purpose-built array of solar photovoltaic modules supplies an alkaline electrolyzer; the produced hydrogen gas is stored in pressured storage tank. When the solar radiation level is insufficient to meet the heat pump power demand, the fuel cell starts converting the chemical energy stored by the hydrogen fuel into electricity. This paper reports on the description of the realized system. Furthermore the efficiency and the operational mode of the electrolyzer were evaluated during a trial period characterized by mutable solar radiant energy. Anyway the electrolyzer worked continuously in a transient state producing fluctuations of the hydrogen production and without ever reaching the steady–state conditions. The Faradic efficiency, evaluated by means of an empirical mathematic model, highlights that the suitable working range of the electrolyzer was 1.5÷2.5 kW and then for hydrogen production more than 0.21 Nm^3h^-1
Oscillations Analysis of Front-Mounted Beet Topper Machine for Biomass Harvesting
Full text linkThe beet leaves and tops, which currently are excluded from the production process of sugar, could be an interesting opportunity for the production of renewable energy. Usually, the defoliators are joined with root collar remover machines, which are installed in front of the tractor. In working conditions on soils having natural roughness these front-mounted beet topper machines carried by tractors are aected by angular oscillations in a longitudinal-vertical plane that strongly aect the cutting uniformity. A theoretical study of these oscillations was carried out in this paper using Lagrange II kind equations, with the aim to assess the design and kinematic parameters of a front-mounted beet topper, corresponding to more stable and suitable movements in the longitudinal-vertical plane. A numerical simulation was then performed adopting the developed mathematical model. In order to improve the eciency of this harvesting machine, a significant role is assumed by the soil preparation. In this work the stiness and damping parameters of the feeler wheels pneumatic tires have been considered constant but further studies are in progress to assess their eective importance and influence for reducing the vibration of the front-mounted beet topper machine with the final aim to achieve a better machine design
- …
