| 1. |
- Cardozo, Evelyn, 1984-
(författare)
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Combustion of agricultural residues : Application for Stirling micro-combined heat and power
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Access to energy services is crucial for the development of countries. Therefore, in developing countries, the access to modern conversion technologies would contribute to reduce the poverty, improve health services and promote the economy especially in rural areas. Around 2.5 billion people in these countries use biomass for cooking. However, major concerns are due to the unsustainable use of biomass and the inefficient conversion technologies employed in rural areas. Therefore, the use of locally available biomass in modern biomass conversion technologies would significantly reduce emissions and improve the energy efficiency. These modern technologies may include residential pellet stoves and boilers which at the moment only are used for heating appliances in industrialized countries. Their combination with a prime mover like a Stirling engine could a very attractive solution to produce combined heat and power (CHP) though still in prototype stage. In this context, this study is mainly focused on the development of an energy system fuelled by locally available biomass to produce heat and electricity based on a Stirling engine. The main objective is to perform experiments to find relevant parameters that characterize the energy system proposed.In the first stage of this work, the suitability of using agricultural residues in a pellet boiler was evaluated in comparison to commercial wood pellets. The agricultural residues used during the tests were: sugar cane bagasse, sunflower husks and Brazil nut shells. The first two residues were pelletized and the last one was reduced to a uniform size. Parameters and energy used during the pelletizing were found. Emission levels and boiler efficiency under steady-state and transient conditions were also presented for the different biomass sorts. In the second stage, the integration of the same pellet burner and the Stirling engine was characterized in terms of losses and efficiency calculations. Finally, the integration of the pelletizing, combustion, and heat and power generation was discussed based on experimental and predicted results.
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| 2. |
- Choque Campero, Luis Antonio, et al.
(författare)
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Biomass-based Brayton-Stirling-AGMD polygeneration for small-scale applications in rural areas
- 2024
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 304
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Choque Campero, Luis Antonio, et al.
(författare)
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Decentralized biomass-based Brayton-Stirling power cycle with an air gap membrane distiller for supplying electricity, heat and clean water in rural areas
- 2024
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 254
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Villarroel-Schneider, Johnny, et al.
(författare)
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Energy self-sufficiency and greenhouse gas emission reductions in Latin American dairy farms through massive implementation of biogas-based solutions
- 2022
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 261, s. 115670-115670
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Tidskriftsartikel (refereegranskat)abstract
- The transition towards sustainable economies with improved resource efficiency is today’s challenge for all productive sectors. The dairy sector in Latin America is growing without considering a clear path for sustainable energy and waste management solutions. This study proposes integrated solutions through a waste-to-energy approach. The solutions consider biogas production (via cow manure) as the main energy conversion pathway; technology solutions include biodigesters, power generators, and combined heat and power systems that supply not only the energy services demanded by dairy farms (for cooking gas, electricity, refrigeration and hot water) but also provide organic fertilizers. Biogas’ potential was estimated to verify whether it can cover the energy demands of the farms, while the levelized costs of producing biogas and electricity were the indicators for the techno-economic evaluation of the solutions. Greenhouse gas emission reductions were estimated by following IPCC guidelines. Specifically, the proposed solutions lead to energy self-sufficiency in most dairy farms with relevant biogas and electricity costs in the range of 1.7–3.7 and 6–12 USD cents/kWh, respectively. In addition, implementing the proposed solutions in Latin American dairy farms would allow annual greenhouse gas emission reductions of 32.8 Mton CO2 eq. with an additional 17 Mton if widespread use of the supplied organic fertilizers is achieved.
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| 5. |
- Villarroel-Schneider, Johnny, et al.
(författare)
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Open-source model applied for techno-economic optimization of a hybrid solarPV biogas-based polygeneration plant: the case of a dairy farmers’ associationin central Bolivia
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Proper sizing of energy systems is a key aspect that allows avoiding overestimated installationcosts or failures in operation and dispatch. Most of the available sizing tools focus on systemsdedicated only to electrical loads, omitting combined energy systems with simultaneous supplyof various thermal demands. This study presents an adaptation of an existing techno-economicoptimization model for broadening the design tool for small-scale energy systems supplyingboth electrical and thermal needs. For this, a new typology of the energy system was proposedadding components such as a combustor and a combined heat and power generator. Thenmodifications were made to the model framework (constraints, parameters, variables andobjective function). The developed model was applied to a polygeneration plant for anassociation of 30 small dairy farmers, where biogas is proposed to be produced to cover thedemand for cooking gas and mainly for fuelling the plant that supplies electricity, refrigerationfor milk (by using absorption refrigeration technology) and heat for drying organic fertilizersthat result from biogas production. In addition, the use of solar PV panels and batteries isconsidered. Different scenarios for analysing and validating the model were proposed; thebase scenario allows the operation of all the system components, generating surpluses ofelectricity (for selling), heat (for other uses) and biogas. The aggregated cost of producingelectricity and heat ranges from 0.043 to 0.068 USD/kWh; the penetration of solar energyranges from 27 to 36%, while the potential savings of CO2 emissions of applying the proposedpolygeneration system ranges from 109 to 131 ton of CO2 per year.
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