The lack of access to electricity and clean water still affects a substantial proportion of rural areas worldwide, in particular the global south. This paper presents a sustainable polygeneration system that can provide electricity, heat, and drinking water by using agricultural residues in remote rural areas. This polygeneration system consists of a solid biomass-fueled Brayton-Stirling combined cycle system, a boiler, and an air-gap membrane distillation unit. Four different system operation modes were designed to examine the most ideal configurations for maximizing power output, overall efficiency, and/or clean water production, considering a polygeneration system designed for a rural village with daily demands of 13450 kWh electricity and 7.5 m3 drinking water. A thermodynamic analysis are employed to analyze and compare these modes, each operating under steady state conditions. The highest electricity output, up to 160 kW, while the highest clean water is up to 0.7 m3/h. The fuel consumption can reach 0.9 kWh/kg of solid fuel and provide up to 0.0045 m3 of freshwater. In addition, nonlinear multi-objective optimization is used to meet the power demands of typical day in rural areas by varying the polygeneration operation modes and turbine inlet temperature.

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.

Avlägsna landsbygder i utvecklingsländer står inför stora utmaningar när det gäller tillgång till stabil energiförsörjning och rent vatten. Denna avhandling presenterar en utredning av ett innovativt koncept, Brayton-Stirling-membrandestillation (BSMD) kraftvärme, för att samtidigt tillhandahålla el och vatten med fokus på småskaliga, lokala applikationer på landsbygden i Bolivia.

BSMD-systemet kombinerar Brayton- och Stirlingcykler för att utnyttja termisk energi från förbränning av lokalt tillgänglig jordbruksbiomassa. Värmeenergin från förbränningen utnyttjas kaskadkopplat i cyklerna, där även restvärme på låg temperatur används för att driva vattenrening genom membrandestillation.

Termodynamiska analyser visade att systemets prestanda varierar från 100-200 kW producerad el och upp till 0,7 m3/h dricksvatten. Parametrar som turbinens inloppstemperatur, tryckförhållande, regeneratorns effektivitet och arbetsmedium påverkar värme- och kraftverkningsgraden. Turbinens inloppstemperatur hade störst effekt på både el- och vattenproduktion.

Flermålsoptimering med icke-linjär programmering (MNLP) användes för att optimera systemets effekt, med hänsyn till faktorer som turbinens inloppstemperatur, vattenbehov och elbehov. Resultaten visar systemets förmåga att uppfylla dubbla mål, efterfrågan på el och rent vatten, samtidigt som man minimerar överskottseffekt och underskott.

Avhandlingen utökar konceptet genom att integrera PV-paneler, batterier och BSMD-systemet. Geografisk mångfald beaktades, vilket betonade systemets anpassningsförmåga till varierande solinstrålning, temperatur och höjd.

Ekonomiska indikatorer för tre byar med cirka 500 personer presenteras, inklusive jämförande kostnad för elektricitet (LCOE) och jämförande kostnad för rent vatten (LCOW). Systemet saknar för närvarande ekonomisk bärkraft, men pågående teknisk utveckling och komponentintegrering kan leda till kostnadsreduktioner i framtiden.

Ensuring access to essential services, such as clean water and electricity, is a key challenge for achieving sustainable development goals in rural areas. This study proposes a novel Brayton-Stirling combined cycle-based cogeneration system for utilizing locally available biomass waste to generate both electricity and clean water. The system employs an externally fired gas turbine, a Stirling engine, and an air–gap membrane distiller. Four operation modes—parallel-powered, fully-fired, straightforward, and by-pass—were modeled for their efficiency and output. Four operation modes can be switched by two three-way valves. Sunflower husk, identified as the most effective biomass source, enabled the system to achieve up to 160 kW of electricity and 0.7 m3/h of freshwater. The electrical and exergy efficiencies of the system peaked in the parallel-power mode, offering a practical solution for enhancing rural sustainability. Moreover, the by-pass mode maximized water production, highlighting its effectiveness in addressing water scarcity along with energy generation. Through a case study, the cogeneration system has demonstrated its capability in satisfying both rural electricity and water demands throughout the day by controlling the combination of different operation modes and parameters. Therefore, it provides a promising solution for advancing rural electrification and water purification in rural areas.

The necessity for green technology to generate power in rural regions is becoming more widely recognized. Stirling engines have attracted a lot of interest in recent years due to their relative ease of maintenance and simple design. Practical experience from the operation and maintenance of the Stirling engine Genoa-01 in Bolivia is the subject of this case study. The project uses a trial-and-error approach to maintain the engine in order to find relevant lessons that may be used in training of power plant personnel based in locations with limited technical resources. Analysis of the information gathered during the study identified the main challenges to overcome for small, decentralized power technologies as supply chain of spare parts, technical capacities, and promotion of the technology.

Access to electricity in many remote rural areas of the world is wanting and often relies on decentralized concepts that are environmentally detrimental, costly, and unreliable. The purpose of this study was to examine an approach to meet this need that is based on an external biomass-fueled cogeneration system incorporating combined cycles for maximizing efficiency while ensuring robust operation. Specifically, the first and second laws of thermodynamics were analyzed in a system composed of a Brayton-Stirling cycle and a water boiler to compare efficiency, heat and electricity generation under three different power layouts of cogeneration for applications in the range of 100-200 kW electrical power output. The results show that overall efficiency is maximized at 85% with a hybrid power layout for cases where the turbine inlet temperature is 1273 K, the pressure ratio is 0.4, the regenerator effectiveness is 0.95, and the dead volume of the Stirling engine is 0.3. These findings provide a basis for implementing cogeneration systems to improve the reliability and robustness of power systems for rural electrification.

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. 

Landsbygdselektrifiering i utvecklingsländer har blivit en av de största utmaningarna för global tillgång till el - ett av FN: s mål för hållbar utveckling. Regeringar, internationella enheter och privata företag står inför utmaningen att förbättra livskvaliteten för människor och minska miljöfarliga utsläpp. Bolivias politiska agenda har handlat om att arbeta samordnat med internationella samarbetsorganisationer och har uppnått stora förbättringar avseende tillgången till el de senaste åren. Olika strategier och tekniker har använts i de olika klimatscenarierna som spänner över Bolivias territorium. Även om fler bolivianer har tillgång till el än för tio år sedan, förhindrar otillräcklig kunskap, utbildning och uppföljning från lokala och nationella aktörer (som kraftproducenter, kraftdistributörer och elsleverantörer) att dessa lösningar fungerar som förväntat.

Denna studie undersöker integrationen av en Stirling-motor i ett litet kraftproduktionssystem för användning i avlägsna landsbygdsområden. Stirling-motorn är en välkänd teknik som kan använda lokala bränslen för att generera energitjänster. Här jämförs två olika hybridsystem i tre fallstudier: det första systemet har solcellspaneler (PV), batterier och dieselmotorer [1] och det andra har solcellspaneler, batterier och Stirling-motorer. I en hållbarhetsanalys jämförs de två systemens miljöeffekter, kostnader och prestanda - effektivitet och tillförlitlighet. Dessutom diskuterar studien underhållet av Stirling-motorn i landsbygden i Bolivia.

Studien började med insamling av data från 17 hushåll i olika samhällen, som just hade fått tillgång till el,. Dessa samhällen kännetecknas av olika miljö- och klimatförhållanden, vilket gör det möjligt för oss att bättre förstå hur systemen fungerar under Bolivias varierande klimat och att ta hänsyn till läget för dess ekonomi och tekniska kapacitet. Med hjälp av GIS-kartor (Geographical Information System) valdes tre bolivianska samhällen ut: Tirina, Tablani och El Carmen. Sex hybridsystem simulerades för dessa samhällen, två dynamiska modeller per samhälle.

Jämförelsen mellan de två systemen visar att Stirling-motorns hybridkraftsystem producerar minst 7 ton per år mindre koldioxidutsläpp än Diesel-hybridkraftsystemet för respektive samhälle. I den finansiella analysen användes ”levelized cost” för el (LCOE) för att visa de två systemens kostnad per kilowattimme (i USD). LCOE för Stirling-systemet är högre än dieselmotorn i de tre samhällena. Nettonuvärdet beräknades för att återspegla kostnaderna för den initiala investeringen, såväl som underhåll, reservdelar med mera under studiens varaktighet. Slutligen analyserades de två systemens prestanda genom ett simulerat dynamiskt test omfattande en dag för respektive system i de tre samhällena. De två systemen uppfyllde då utan problem samhällenas effektbehov. Dessa effektbehov har toppar mellan  5 kW och 7 kW.

The Bolivian government's concerns that are related to reducing the consumption of diesel fuel, which is imported, subsidized, and provided to isolated electric plants in rural communities, have led to the implementation of hybrid power systems. Therefore, this article presents the performance analysis in terms of energy efficiency, economic feasibility, and environmental sustainability of a photovoltaic (PV)/Stirling battery system. The analysis includes the dynamic start-up and cooling phases of the system, and then compares its performance with a hybrid photovoltaic (PV)/diesel/battery system, whose configuration is usually more common. Both systems were initially optimized in size using the well-known energy optimization software tool, HOMER. An estimated demand for a hypothetical case study of electrification for a rural village of 102 households, called "Tacuaral de Mattos", was also considered. However, since the characteristics of the proposed systems required a detailed analysis of its dynamics, a dynamic model that complemented the HOMER analysis was developed using MATLAB Simulink TM 8.9. The results showed that the PV/Stirling battery system represented a higher performance option to implement in the electrification project, due to its good environmental sustainability (69% savings in CO2 emissions), economic criterion (11% savings in annualized total cost), and energy efficiency (5% savings in fuel energy conversion).

This article presents the performance analysis related to energy efficiency, economic feasibility and environmental sustainability of a hybrid power system, composed of photovoltaic modules, batteries and a Stirling engine powered by wood pellets. The analysis includes the dynamic start-up and cooling phases of the system, and then compares its performance with a hybrid photovoltaic-diesel-battery system. The first system consists of a 5.45 kW solar array, a 6 kW Stirling engine, a 6.92 kW bidirectional inverter and a 71.28 kWh VRLA gel lead-acid battery bank. The second one is comprised of 3.95 kW PV panels, a 7.1 kW diesel genset, a 4.46 kW bi-directional inverter and a 50.16 kWh VRLA gel lead-acid battery bank. The initial sizing of both systems was based on the demand estimated for a hypothetical case study of electrification for a 102-household rural village in Bolivia called “Tacuaral de Mattos”. Both systems were initially optimized in size using the well-known energy optimization software tool, HOMER. However, since the characteristics of the proposed system required a detailed analysis of its dynamics, a dynamic model that complements the HOMER analysis was developed using MATLAB Simulink TM 8.9. Furthermore, due to fluctuations of photovoltaic energy as well as the importance of the battery life cycle, a smart power management was implemented through combined dispatch algorithms. These control algorithms were composed of typical “Cycle charging”, “Load Following”, “Frugal” and “SOC set point” strategies. Additionally, a supervisory controller was designed in order to compensate the energy difference during the warmup, stand-by and cool-down modes of the Stirling engine and diesel generator. The results showed that PV-diesel-battery system represented a higher-performance option to implement in a rural electrification project compared to a PV-Stirling-battery system. However, the last one showed a better environmental sustainability as it was able to reduce carbon dioxide emissions during its operation (Around 10% savings in CO2 emissions).