This thesis summarizes a degree project in Sustainable Energy Engineering, carried out by two students at the Royal Institute of Technology, Stockholm, in the year of 2014. As the extension of the power grid in Bolivia is largely underdeveloped, approximately half of the country’s rural inhabitants live in areas without access to electricity. Access to electricity not only improves standard of living for individuals, it also enables a more developed and sustainable society.
The aim of this study was to design an off-grid energy system containing a Stirling engine, designed for rural households in lowland areas of Bolivia. The Stirling engine is externally heated, have a high efficiency and high fuel flexibility. The engine was supposed to be fueled by biomass combustion, a renewable source highly accessible in Bolivia.
In order to design the energy system, the electricity demand, the daily routine of energy use and the Stirling technology had to be researched and analyzed. As a result, a conceptual model of the energy system was made, and a simulation of the model was conducted using HOMER software. In the simulation, a 2 kWel Stirling engine system with a 1 kWel support engine during peak hours and 3 kWel Stirling engine were analyzed.
Test results show that a 3 kWel engine, with an electrical efficiency of 15 %, combined with two 6 kWh batteries can provide 30 households with the required amount of electricity, also in critical situations such as fluctuating demands and occasional interruptions of the engine operation.
The 2 kWel engine system in combination with 25 batteries, 6 kWh each, could also supply the required demand. The power plant consisting of two engines provide a more flexible and resource effective solution, requiring 21 % less biomass than the 3 kWel engine. However, the combined system also requires a larger involvement from a user’s perspective.
Results revealed that Stirling engines are a viable solution for rural electrification in Bolivia. However, there are obstacles regarding the Stirling technology that have to meet a solution before the engine will reach a commercial breakthrough.
Source: KTH
Authors: Ljunggren Falk, Hugo | Berg, Sandra