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- Cardozo Rocabado, Evelyn, et al.
(author)
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Combustion of agricultural residues : An experimental study for small-scale applications
- 2014
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In: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 115, s. 778-787
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Journal article (peer-reviewed)abstract
- Energy services could be greatly improved by using of residues from local food industries in small-scale combustion units. Wood pellets are a reliant and proven fuel to be used in small-scale combustion units. However, these units should preferably be able to use different types of biomass depending what it is locally available. Therefore, studies have been focused on exploring the suitability of using agricultural residues for small-scale heat and power generation using direct combustion. This study targets to compare the combustion of different agricultural residues in a single unit designed for wood pellets. The different biomass fuels used are circle divide 6 mm and circle divide 8 mmwood pellets, circle divide 6 mmbagasse pellets, circle divide 6 mmsunflower husk (SFH) pellets and Brazil nut (BN) shells. The results reveal a decrease in the fuel power input, higher oxygen levels in the flue gases and shorter cycles for ash removal when using the agricultural residues. The excess air ratio was calculated based on a mass balance and compared with a standard equation showing a good agreement. CO and NO emission levels as well as the relative conversion of fuel-C to CO were higher for the BN shells and SFH pellets in comparison to the other biomass types. SO2 emission was estimated based on the analysis of unburned sulfur in ash and mass balances; the higher estimated levels corresponded to the BN shells and SFH pellets. All the biomass sorts presented over 95% relative conversion of fuel-C to CO2. Wood pellets and BN shells presented the highest amount of unburned carbon in ash relative to the fuel-C. The relative conversion of fuel-N to NO and fuel-S to SO2 were higher for wood pellets. Bagasse pellets showed similar emission levels and relative conversion efficiency to wood pellets.
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| 2. |
- Cardozo Rocabado, Evelyn, et al.
(author)
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Comparison of the thermal power availability of different agricultural residues using a residential boiler
- 2016
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In: BIOMASS CONVERSION AND BIOREFINERY. - : Springer. - 2190-6815 .- 2190-6823. ; 6:4, s. 435-447
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Journal article (peer-reviewed)abstract
- This study presents a comparison of combustion performance, losses, and efficiency at steady-state and transient conditions for different biomass types in a residential boiler. The types of biomass used were 6 and 8 mm wood pellets, 6 mm sugarcane bagasse pellets, 6 mm sunflower husk pellets, and Brazil nut shells. The comparison in the development of the temperature in the combustion chamber during the start-up revealed that the 6 mm wood pellets ignite and propagate faster than the rest of the biomass fuels due to their smaller size compared with 8 mm wood pellets and lower ash content compared with the rest of the biomass sorts. Thermal power output and efficiencies under steady-state and transient conditions were calculated by the direct method, i.e., by measuring the heat recovery by the water boiler, and the indirect method, i.e., by measuring the heat losses. By using the indirect method, the availability of the flue gas thermal power during the start-up was seen more in detail than when the other method was applied. When comparing both methods as tools for boiler efficiency evaluation for different fuel types, the discrepancy of the resulting efficiencies between is larger when there are higher amounts of chemical losses in the boiler. Therefore, this method shows good agreement also for bagasse pellets but is, without modification, proposed not to be valid for fuels emitting higher amount of carbon monoxide (CO). Boiler efficiencies reached class 3 boilers according to EN 303-5 (> 74.8 %) for all biomass sorts.
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| 6. |
- Villarroel-Schneider, Johnny, et al.
(author)
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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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In: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 261, s. 115670-115670
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Journal article (peer-reviewed)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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| 7. |
- Villarroel-Schneider, Johnny, et al.
(author)
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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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Other publication (other academic/artistic)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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