Abstract
A hybrid solar-assisted trigeneration system is analyzed in this paper. The system is composed of a 20 m2 solar field of evacuated tube collectors, a natural gas fired micro combined heat and power system delivering 12.5 kW of thermal power, an absorption heat pump (AHP) with a nominal cooling power of 17.6 kW, two storage tanks (hot and cold) and an electric auxiliary heater (AH). The plant satisfies the energy demand of an office building located in Naples (Southern Italy). The electric energy of the cogenerator is used to meet the load and auxiliaries electric demand; the interactions with the grid are considered in cases of excess or over requests. This hybrid solution is interesting for buildings located in cities or historical centers with limited usable roof surface to install a conventional solar heating and cooling (SHC) system able to achieve high solar fraction (SF). The results of dynamic simulation show that a tilt angle of 30° maximizes the SF of the system on annual basis achieving about 53.5%. The influence on the performance of proposed system of the hot water storage tank (HST) characteristics (volume, insulation) is also studied. It is highlighted that the SF improves when better insulated and bigger HSTs are considered. A maximum SF of about 58.2% is obtained with a 2000 L storage, whereas the lower thermal losses take place with a better insulated 1000 L tank.
Highlights
In the European Union, energy consumption in the residential sector with respect to the total final energy use increased from 37.4% to 40.6% in the period 2011–2013 [1,2]
By comparing the analyzed trigeneration plant with a similar solar heating and cooling (SHC) system in which the micro-CHP is replaced by a natural gas fired boiler and the electricity is drawn entirely from the grid a significant primary energy savings is achieved
The hybrid solar-assisted trigeneration system based on micro-CHP coupled to solar thermal collectors shows a certain primary energy saving (7.77%) with respect to the conventional air conditioning system used in Italy, that consists of a natural gas fired boiler for the heating operation and an electric chiller for the cooling
Summary
In the European Union, energy consumption in the residential sector with respect to the total final energy use increased from 37.4% to 40.6% in the period 2011–2013 [1,2]. Kegel et al [18] performed a comparison of different solar thermal, cogeneration and thermally driven heating/cooling systems to supply the energy demands of a typical apartment in Canada They evaluated the GHG emissions, the annual costs savings and the primary energy consumption of various system configurations with respect to the base case. In this case the system can achieve an annual cost saving and avoided GHG emissions of 21%. The choice of a backup system, that has a higher overall conversion efficiency, results in significant primary energy savings compared to the conventional SHC and air conditioning systems
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