Rural electrification in Bolivia through solar powered Stirling engines Carlos Gaitan Bachelor of ScienceI Thesis KTH School of Industrial Engineering and Management Energy Technology EGI-2014 SE-100 44 STOCKHOLM Bachelor of Science Thesis EGI-2014 Rural electrification in Bolivia through solar powered Stirling engines Carlos Gaitan Approved Examiner Supervisor Catharina Erlich Commissioner Contact person II Abstract This study focuses on the rural areas of Bolivia. The village investigated is assumed to have 70 households and one school. Electrical supply will be covered with the help of solar powered Stirling engines. A Stirling engine is an engine with an external heat source, which could be fuel or biomass for example. The model calculates the electrical demand for two different cases. One low level demand and one high level demand. By studying the total electrical demand of the village, the model can calculate a sizing for the Stirling system. However, for the sizing to be more accurate, more research needs to be done with regards to the demand of the village and the incoming parameters of the model. III Sammanfattning Den här studien fokuserar på landsbygden i Bolivia. En by som antas ha 70 hushåll och en skola är det som ligger till grund för studien. Byn ska försörjas med el med hjälp av soldrivna Stirling motorer. En Stirling motor är en motor som drivs med en extern värmekälla. Denna värmekälla kan vara exempelvis biomassa eller annan bränsle. Modellen som tas fram i projektet beräknar elektricitetsbehovet för byn för två nivåer, ett lågt elbehov och ett högt elbehov. Genom att studera det totala elbehovet över dagen kan modellen beräkna fram en storlek för Stirling systemet. För att ge mer noggranna svar, krävs dock att forskning utförs i byn som ska försörjas. Dessutom krävs en mer noggrann information om de ingående parametrarna i modellen. IV Table of Contents Abstract ...............................................................................................................................................................III Sammanfattning ................................................................................................................................................ IV Table of Figures .............................................................................................................................................. VII Table of Tables.............................................................................................................................................. VIII Nomenclature ....................................................................................................................................................IX 1 Introduction ................................................................................................................................................. 1 2 Problem formulation .................................................................................................................................. 1 2.1 Aim of study......................................................................................................................................... 1 3 Literature study ............................................................................................................................................ 2 3.1 Bolivia .................................................................................................................................................... 2 3.1.1 Energy Situation in Bolivia ....................................................................................................... 2 3.1.2 Potential for solar energy in Bolivia ....................................................................................... 4 3.2 Common concentrated solar power technologies ....................................................................... 5 3.3 Stirling Engine ..................................................................................................................................... 6 3.3.1 Stirling Cycle ................................................................................................................................ 7 a. Mode of Operation ........................................................................................................................... 8 b. Forms of Coupling ........................................................................................................................... 8 c. Phase Difference ............................................................................................................................... 9 d. Working Fluid for Stirling Engine ................................................................................................ 9 e. Heat Source for Stirling Engine ..................................................................................................... 9 3.3.2 Solar Powered Stirling Engines ............................................................................................... 9 3.3.3 Parabolic Dish Stirling Technology ........................................................................................ 9 3.3.4 Global case studies for solar powered Stirling engines .................................................... 10 3.3.5 Disadvantages with the Stirling engine ................................................................................ 12 4 Model ........................................................................................................................................................... 13 4.1 System boundaries ............................................................................................................................ 13 4.2 Energy demand in the rural areas .................................................................................................. 14 4.2.1 Demand levels ........................................................................................................................... 14 4.2.2 Electricity demand.................................................................................................................... 16 4.2.3 Sensibility analysis of electricity demand ............................................................................. 16 4.3 Stirling system .................................................................................................................................... 17 4.3.1 Sensitivity analysis of the Stirling system ............................................................................ 19 V 5 Results and discussion .............................................................................................................................. 20 5.1 Results and discussion from the model ....................................................................................... 20 5.2 Results and discussion of the sensitivity analysis for the village electricity demand.......... 23 5.3 Results of the sensitivity analysis for the Stirling system ......................................................... 24 6 Conclusions ................................................................................................................................................ 25 7 Future work ................................................................................................................................................ 25 8 Bibliography ............................................................................................................................................... 26 Appendix A. Matlab code for the simulation ............................................................................................. 29 VI Table of Figures Figure 1: Energy sources in Bolivia year 2012 (EIA, Bolivia Full Report, 2012) ................................. 2 Figure 2: Installed capacity (GW) in Bolivia during 1990-2011 (EIA, Country Data - U.S. Energy Information Administration, 2011)....................................................................................................... 3 Figure 3: Electrification coverage in Bolivia (Energypedia, 2010)........................................................... 4 Figure 4: Solar irradiance in Bolivia (Energetica, 2014) ........................................................................... 4 Figure 5: Comparing the Annual Solar Irradiance in major cities of Germany, Spain and Bolivia (Maxwell, 2013) ......................................................................................................................................... 5 Figure 6: Stirling Cycle (Pierre Gras).............................................................................................................. 7 Figure 7: Concept of Stirling cycle (Foster, 2011) ....................................................................................... 7 Figure 8: Alpha, Beta and Gamma Coupling (Sayma, 2013) .................................................................... 8 Figure 9: Solar dish Stirling system (M Abbas, 2011) ............................................................................. 10 Figure 10: Flowchart for the rural village .................................................................................................... 13 Figure 11: Variation in solar irradiation in summer and winter (Christiana Honsberg, 2009) ........ 18 Figure 12: Stirling engine output as a function of the solar irradiation ................................................ 18 Figure 13: Load