Biomass gasification for combined heat and power generation in the Cuban context: Energetic and economic analysis

Abstract

In the present work is performed a technical and economic analysis of a combined heat and power 9 generation system (CHP), designed to operate coupled to an internal combustion engine (ICE) fuelled with 10 biomass producer gas, in order to generate electricity and hot water for isolated communities of power 11 distribution network. In the proposed system configuration, the energy of the engine's hot exhaust gases is 12 recovered (cogeneration), making this system more attractive in relation to conventional configurations, which 13 are normally used to produce solely mechanical and electrical energy. The proposed system is composed of a 14 modified downdraft gasifier, Imbert technology; coupled to an internal combustion engine, model ZIL−130. 15The system is designed and built in the laboratory of fluid mechanics at the University of Camagüey. The 16 feedstock studied for the gasifier was Dichrostachys Cinerea, collected in neighboring areas to the proposed 17 place of installation. The main energy flows and the costs associated with the production of producer gas were 18 determinate. From the mass and energy balances, the thermal and electric efficiencies of the cogeneration 19 systems resulted in η hw =32.4% and η ge =23.4% respectively, whereas the overall efficiency led to η global =33.3%. 20 In the economic analysis were studied the Internal Rate of Return (IRR), the Net Present Value (NPV) and time 21 of return on investment (TRI) or payback, considering a project lifespan of 15 years. For the annual interest rate 22 of 12%, the electricity should be sold at 0.3USD/kWh in order to the project be feasible. The IRR resulted in 23 12%, the NPV was 20,571 USD and payback period resulted in 5.3 years. In the proposed configuration, the 24 system consumes 1.46 kg of biomass per kWe produced, with a maximum cost of generated electricity of 0.022 25 USD/kWh.26 27 Nomenclature ݉ሶ − mass flow rate [kg/s or m 3 /h] n −r.p.m cw − cool water T − temperature [K] HHV-High hating value exh − flue gas N − power [kW] LHV-low heating value [kJ/kg or MJ/m 3 ] elec − electricity C 1 ,C 2 ,C 3 − coefficients of the engine Subscript e-electric ge − specific fuel consumption[g/kWh] bio − biomass net -net Tr − torque [kgf.m] i− each parameter of engine gas-producer gas Cp − average specific heat [kJ/kgK] N − nominal parameter of engine csys-cogeneration systems E − energy [kWh] out − outlet Superscripts I − Investment [USD$] in − inlet t-amortization periods C M − maintenance cost [USD$/kWh] hw − hot water Greek symbols C − cost [USD$/kWh] hw HE 1,2,4 -hot water in heat exchangers ߟ− efficiency Fp − adjustment factor air HE3 -hot air in heat exchanger 3 r-annual interest rate th − thermal q -factor eng/ger − engine generator

The potential of coffee stems gasification to provide bioenergy for coffee farms: a case study in the Colombian coffee sector

“…Overall, the cogeneration system efficiency, results in 45.6%, agreeing with numbers reported in similar works about the gasification of agricultural residues in gasifiers-CHP systems [63,71,72]. The maximum low-grade heat recovered from both cooling systems could be used to supply the internal heat requirements of the system and/or external heat demands of the coffee drying process.…”

“…Producer gas with calorific values (> 4 MJ Nm −3 ) and low pollutant contents (< 100 mg Nm −3 for tar content and < 50 mg Nm −3 for particulates) can be directly injected into ICE [61,62]. Spark ignition engines currently designed to work with petrol or diesel require adaptations in the injection systems to be fuelled with producer gas [62,63]; however, these do not affect performance at the level being assessed in this work.…”

“…Measures the ratio between the sum of the net electric power output (E el ) and useful thermal power output (E th ) over the biomass energy input (E bm ) [63] η cogen ¼ EelþEth Ebm , where E bm = m bm . LHV bm temperature profile.…”

Technical assessment of discarded tires gasification as alternative technology for electricity generation

“…The development of new engines and gas turbines able to use gas with low heating value as fuel (Barsali et al, 2015;Gobbato et al, 2015;Pérez et al, 2015) and the relatively high heating value of TDF enable the implementation of the gasification of TDF for electric and thermal power generation.…”

“…5 shows the interconnection between the installations that compose the Gasification Island; which is formed by the ASU, the BFBG and the Cleaning System. The considered technology of BFBG was the RENUGAS, technology commercially available and tested (Pérez et al, 2015).…”