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The Stirling engine as a part of a hybrid power system

a study of applications in rural areas of Bolivia

Time: Tue 2021-05-25 13.00

Location:, Stockholm (English)

Subject area: Energy Technology

Doctoral student: Luis Antonio Choque Campero , Tillämpad termodynamik och kylteknik, Energy Technology

Opponent: Professor Emeritus Carl-Johan Fohelholm, Aalto University

Supervisor: Professor Per Lundqvist, Tillämpad termodynamik och kylteknik

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Rural electrification in developing countries has become one of the greatest challenges for achieving global access to electricity—one of the United Nation’s sustainable development goals. Governments, international entities and private companies are tasked with improving the quality of life for people and reducing environmentally harmful emissions. Bolivia’s political agenda has been working in coordination with international cooperation organizations, and it has achieved great improvements in access to electricity in recent years. Different strategies and technologies have been used in the various climate scenarios that span Bolivia’s territory. Although more Bolivians have access to electricity than 10 years ago, insufficient knowledge, training, and follow-up from local and national actors (such as power producers, power distributors, and electricity service providers) prevent these solutions from operating as expected.

This study explores the integration of a Stirling engine into a small power production system for use in remote rural areas. The Stirling engine is a well-known technology that can use local fuels to generate power and heat. Here two different hybrid power systems in three case studies are compared: the first system is using photovoltaic (PV) panels, batteries, and diesel engines and the second is using PV panels, batteries, and Stirling engines. In a sustainability analysis the environmental effects, economy, and performances—efficiency and reliability—of the two systems are compared. In addition, the study discusses the maintenance of the Stirling engine in Bolivia rural conditions.

The study began by gathering data from 17 households in different communities, which had just obtained access to electricity. These communities are characterized by different environmental and climate conditions, which allows us to better understand how the systems operate under Bolivia’s varying climate and to consider the state of its economy and technical capacity. With the help of GIS (Geographical Information System) maps, three Bolivian communities were selected: Tirina, Tablani, and El Carmen. Six hybrid power system were simulated for these communities, two dynamic models per community. 

The comparison between the two systems shows that Stirling engine hybrid power system produces at least 7 Tons per year less CO2 emissions than the Diesel hybrid power system per community. The financial analysis used the levelized cost of electricity (LCOE) to show the two systems’ cost per kilowatt-hour (in USD). The LCOE of the Stirling system is higher than the diesel engine in the three communities. The net present value was calculated to reflect the costs of the initial investment, as well as maintenance, spare parts, and so on, over the duration of the study. Finally, performance of the two systems was analyzed through a simulated one-day dynamic test of both systems in the three communities. The two systems responded without problem to the communities’ power demands. These power demands have peaks between about 5 kW and 7 kW.