Analysis of biomass gasification systems using a rural community development model

Abstract

Biomass is still regarded as an important energy resource in Thai rural communities for the future. The utilization of producer gas obtained from the gasification of biomass to power internal combustion engines is one application of interest to provide self-power generation in areas where grid electricity is unavailable. Scientists, engineers and decision makers do not generally have sufficient details of the economic and technical interactions between a given gasification technology system and a given rural community. This study is an attempt at giving a general assessment regarding introduction of gasification systems based on one rural community. The Rural Community Development Model (RCDM) was developped to simulate a decision process for the development of rural communities with emphasis on rural energy development, taking into account income, economic conditions, occupations of people and local resources, then arrange them in an appropriate manner to maximize income of the community. A FINERG software was used to solve the RCDM and is composed of the Reference Energy System (RES), the Energy Sector Data Base, the Simulation Model and the Optimization Model. For this study Nongwang, a rural community in Sakhon Nakhon Province with about 1,500 people or an average of 6 persons per household, was chosen as a case study for gasification technology systems introduction using local resources such as wood, charcoal, rice husk as against the conventional gasoline or diesel energy systems. Simulation of several gasification systems were made for electricity generation, operatiobn of diesel engine water pumps for irrigation and shaft power for the existing rice mill. RCDM was used firstly to choose the most economically acceptable system for the community and indicate by how much investment and variable costs the remaining systems should be decreased by in order to be compatible with the system selected. Secondly, a sensitivity analysis of fuel prices was performed. The model was also able to indicate economic operating hours for the various systems and arrange some activities to maximize income of Nongwang. At gasoline and diesel prices above 8.9 and 6.3 BT/LIT respectively, the most economic charcoal gasifier system introduced is the dual-fuel diesel engine system in the capacity of 10 KW with an investment cost not exceeding 12,635 BT/KW and a minimum operating time of 2,880 HRS/YEAR, for charcoal prices up to 1.50 BT/KG. Among the wood gasifier systems we have introduced, the optimum design compatible with a conventional diesel system is the 50 KW dual-fuel diesel engine system with the maximum gasifier investment cost of 13,965 BT/KW at wood prices up to 1,082 BT/T0N. The minimum operating time for the system to be economic are 2,524; 2,571 and 2,880 HRS/YEAR for wood prices of 288, 509, and over 797 BT/T0N, respectively. For rice husk gasifier, the most favorable system introduced is the gasifier-gaso1irie engine in the capacity of 50 KW with the maximum gasifier investment cost of 13,965 BT/KW at rice husk prices up to 515 BT/TON which could be operated only 2,400 HRS/YEAR. The higher cost of rice husk requires more running time towards 2,880 HRS/YEAR. In case of Nongwang, a charcoal gasifier dual-fueled with diesel engine (10 KW) to be used for lighting yielded an unexpected negative income of 246,000 Baht for the 1985-1989 period at an electricity cost of 4.38 BT/KWH which is unlikely to be competitive with the old system of kerosene lamps. However introducing one 20 KW diesel pump and a wood gasifier dual-fueled with diesel as another pumping system indicated a decrease in income at the first year due to the high capital investment, but the total income in the five years period would increase by about the same amount for both systems or about 835,000 Baht. Then only after five years would the gasifier-diese system be more interesting than the diesel system alone. Finally introducing a 50 KW rice husk gasifier-gaso1ine engine to the mill would have the most important impact on the Community by increasing income by 1,152,000 Baht for the same five years period.