Brayton-Stirling-Membrane Distillation systems for clean energy and water access in rural Bolivia
Time: Wed 2024-06-05 13.00
Location: F2, Lindstedtsvägen 26 & 28, Stockholm
Language: English
Subject area: Energy Technology
Doctoral student: Luis Antonio Choque Campero , Kraft- och värmeteknologi, Energy technology
Opponent: Professor Juha Kaikko, Lappeenranta-Lahti University of Technology
Supervisor: Professor Andrew R. Martin, Kraft- och värmeteknologi; Dr Wujun Wang, Kraft- och värmeteknologi
Abstract
Remote rural areas in developing countries face significant challenges toward securing supplies of energy and clean water. This thesis presents an investigation of an innovative concept—Brayton-Stirling-Membrane Distillation cogeneration—for the simultaneous provision of electricity and water with particular focus on small scale, decentralized applications in rural areas of Bolivia. The considered Brayton and Stirling cycles are externally fired, allowing for utilization of a locally available energy resource (waste agricultural biomass) via standard combustion processes. Both cycles can be paired thermally to make use of cascaded heat, with additional low-grade heat used to drive water purification through membrane distillation.
Thermodynamic analyses of each operation mode were used to assess the system performance. The performance of the operation modes ranges from 100-200 kW of produced electricity and up to 0.7 m3/h of drinking water. Parameters such as turbine inlet temperature, pressure ratio, regenerator effectiveness, and working fluid impact cogeneration efficiency. The turbine inlet temperature had the largest effect on the production of electricity and water. This study identified trends in water production and energy and exergy efficiency, emphasizing the capability of the system to generate both electricity and drinking water from agricultural residues.
Multi-objective Nonlinear Programming (MNLP) was employed for dispatch optimization, considering factors such as an externally fired gas turbine inlet temperature range of 973 to 1123 K, minimum daily water demand of 7.5 m3 and typical hourly-daily electrical demand of 13450 kWh. The results demonstrate the system’s ability to meet dual objectives, electricity and clean water demand, while minimizing excess power and deficits.
Expanding the scope, this thesis delves into a hybrid cogeneration system integrating PV panels, batteries, and the Brayton-Stirling-MD system. Geographical diversity was considered, emphasizing the adaptability of the system to varying solar irradiation, temperature, and altitude. Economic indicators for three villages of around 500 people, including Levelized Cost of Electricity (LCOE) and Levelized Cost of Clean Water (LCOW), are presented. The system currently lacks economic viability, but ongoing technological development and component integration will lead to cost reduction towards to accept level in the future.