Inthis chapter, the tri-generation system in analysed and evaluated from theeconomic and environmental points of view, based on the system year roundsimulation and the detailed energetic performance presented in Chapter 6. Onthe economic side, the simple payback period method and the Net Present Valuemethod were employed to study and investigate the economic feasibility ofinvesting in such solar-biomass driven tri-generation systems. It was shownthat the annual financial savings due to the operation of the tri-generationsystem is about 8226 USD on the heating bill, 961 USD on the electricity billand 951 USD on the cooling bill. The payback period estimated is in the rangeof 3.6-11.
9 based on the wood pellets price. In addition, it was shown that theinstallation and delivery cost is a key factor in the evaluation of the overallsystem economic feasibility. At a delivery and installation cost of 10% of thetotal system cost, the payback period ranges between 3.4 and 11 years atdifferent wood pellets cost where the payback period increases to be in therange of 4.5-14.6 years at a delivery and installation cost of 50% of thesystem total cost. Moreover, it was shown that employing a hybrid solar-biomasssource to drive the tri-generation system under the Lebanese conditions iseconomically feasible when the biomass wood pellets cost is higher than 250USD/tonne, providing higher savings and shorter payback periods.
In addition,the Net present value reported ranges between 10624-50579 USD depending on theinterest rate employed and considering a system lifetime of 25 years with anaverage wood pellets price of 300 USD/tonne. Environmentally, the annual CO2emissions due to the biomass boiler operation is about 1296 kg where the amountof CO2 emissions avoided due to the operation of the proposedtri-generation system ranges between 3.1 tonnes in June and 9.2 tonnes inMarch, compared to the conventional cooling, heating and power generationtechniques. The economic and environmental evaluation carried out in thischapter demonstrates the large potential of the renewable energy-drivenmicro-scale tri-generation systems under the Lebanese conditions compared tothe current separate energy production technologies.