Technoeconomic assessment of solar combined heat and power systems based on hybrid PVT collectors in greenhouse applications

This paper presents a technoeconomic analysis of a solar combined heat and power (S-CHP) system based on hybrid photovoltaic-thermal (PVT) collectors for distributed cogeneration in a greenhouse tomato-farm in Bari, Italy. The thermal and electrical demands of the greenhouse of interest are currently fulfilled by a gas-fired CHP system that features an internal combustion engine (ICE) prime mover, and partially by an auxiliary gas boiler and electricity from the grid. A PVT-water S-CHP system is designed and sized based on a transient model, with hourly weather data and measured demand data given as inputs. Annual simulations are performed to predict the transient behaviour of the S-CHP system and to assess the system's energy outputs. The economic profitability of such solution is also evaluated by considering the investment costs and cost savings due to the reduced on-site energy consumption. The results show that, with an installation area of 30,000 m2, the PVT S-CHP system is able to cover up to 73% of the annual thermal demand of the greenhouse, while delivering a net electrical output 2.6 times that of the annual electrical demand. This performance is similar to that achieved by the equivalent ICE-CHP system (92% and 2 times, respectively). Furthermore, the total annual cost saving of the PVT S-CHP system is more than 6 times higher than that of the ICE system, due to the much lower fuel cost of the PVT system. Similarly, the potential CO2 emission reduction associated with the PVT system is considerably higher, at 3010 tCO2/year saved (vs. 86 tCO2/year). The payback time of the PVT system is not significantly longer than that of the ICE system (10.4 years vs. 8.4 years), but its levelized cost of energy is much lower (0.076 /kWh vs. 0.132 /kWh) due to the higher annual cost savings. These results indicate that such PVT S-CHP systems have an excellent technoeconomic potential in the proposed greenhouse applications and could be competitive over conventional fossil-fuel-based ICE-CHP systems in terms of energetic, economic and also environmental metrics.