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Exergo-economic analysis of a direct biogas upgrading process to synthetic natural gas via integrated high-temperature electrolysis and methanation
KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Universidade de Lisboa, Portugal.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Politecnico di Torino, Italy.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology.ORCID iD: 0000-0002-3661-7016
2017 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 141, p. 1524-1537Article in journal (Refereed) Published
Abstract [en]

Biogas upgrading to synthetic natural gas (SNG) is a viable and appealing route for power-to-gas because it combines waste management with the use of the surplus electricity that might arise in energy systems having a considerable share of renewable energy sources in their production mix. In this work, the exergo-economic performance of a biogas upgrading process through integrated electrolysis and methanation is assessed in connection with the current market status to test which conditions could make the proposed option economically viable. Two different configurations, which differ mainly for the operating pressure of the electrolyser, are compared. The exergy efficiencies are high (>80%) and exergo-economic costs of the produced bio-SNG in the two analyzed configurations are 5.62 and 4.87 c(sic)/kWh(exergy), for low- and high-pressure respectively. Lower values would be required for the bio-SNG to compete with fossil natural gas. We show how both the input electricity price and the capacity factor have a substantial impact on the economic sustainability of the process. Eventually, the monetary exploitation of the oxygen produced by electrolysis and the participation to the emission trading scheme could contribute further to improve the economic attractiveness of the process.

Place, publisher, year, edition, pages
Elsevier, 2017. Vol. 141, p. 1524-1537
Keywords [en]
Power-to-gas, Biogas upgrading, SOEC, Exergo-economic analysis, Carbon capture and usage (CCU)
National Category
Energy Systems
Identifiers
URN: urn:nbn:se:kth:diva-222456DOI: 10.1016/j.energy.2017.11.080ISI: 000423249200015Scopus ID: 2-s2.0-85034747846OAI: oai:DiVA.org:kth-222456DiVA, id: diva2:1181645
Note

QC 20180209

Available from: 2018-02-09 Created: 2018-02-09 Last updated: 2018-09-12Bibliographically approved
In thesis
1. Techno-economic analysis and optimization of electrochemical energy storage solutions
Open this publication in new window or tab >>Techno-economic analysis and optimization of electrochemical energy storage solutions
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The need to integrate the rapidly growing share of variable renewable energy sources in the power sector requires solutions that are capable of mitigating the intermittent nature of these sources. They are expected to constitute the backbone of the electricity generation system in the coming years in order to reach ambitious goals in terms of energy security and reduction of environmental impact. Energy storage appears a promising solution to improve the capability of variable renewable plants to meet the energy demand at all times, mainly through the re-allocation of the generation surplus.

Among the several options that can favor the integration of variable renewables, electrochemical storage technologies - batteries and electrolysis cells - constitute the focus of this dissertation. These approaches can be used to defer substantial quantities of energy for medium to long time intervals, are largely location independent, and are considered a strategic part of the decarbonization pathway in the European Union, which represents the geo-political framework under investigation.

Battery storage systems are analyzed in both small- and large-scale settings to quantify the energetic and economic benefits deriving from a more efficient use of renewable energy. A small-scale battery system connected to a residential PV plant is analyzed and the results are compared to a demand response strategy for load shifting. The integration of a large-scale battery facility in the energy system of an island is also simulated and the results show a much lower level of renewable energy curtailment. In both the situations the projected costs of the battery technologies are used to assess their techno-economic performance.

Solid oxide electrolysis cells (SOECs) as employed in power-to-gas upgrading of biogas constitute the second electrochemical energy storage pathway that was studied. The upgrading process sought to increase the methane content in the biogas by directly converting the embedded carbon dioxide through high-temperature electrolysis and methanation. This process showed energy conversion efficiencies higher than 80%. However, its economic viability depends on the cost of electricity, the cost of the core components, and the price of natural gas.

Abstract [sv]

Behovet för integrering av förnybar energis ökande andel inom elkraftssektorn innebär lösningar som kan hantera dessa energikällors oregelbundenhet. Förnybara energikällor förväntas att bidra till elkrafts ryggrad inom de kommande åren för att kunna nå de ambitiösa målen gällande energisäkerhet och förbättrad miljöprestanda. Energilagring är en lovande teknik för att underlätta förnybara energikällors möjligheter att tillgodose energibehoven dygnet runt, primärt genom omallokeringen av överskottsel.

Bland de olika alternativen som kan öka integreringsgraden av förnybara energikällor är elektrokemiska lagringstekniker – batterier och elektrolysörer – i fokus i denna avhandling. Dessa enheter kan användas för att flytta en del av energin inom mellan- och långtidsintervaller, är i huvud sak oberoende av placeringen och är en strategisk del av EU:s plan för minskning av koldioxidutsläpp. Det senare omfattar avhandlingens geopolitiska ramverk.

Batterilagringssystem är analyserade i både små- och storskaliga faller för att kvantifiera de energimässiga och ekonomiska fördelarna med en mer effektiv användning av förnybar energi. Ett småskaligt batterisystem kopplat till villabaserade solceller analyserades och resultaten jämfördes mot en efterfrågans-baserad strategi. Integrering av en storskalig batterianläggning för ett energisystem p en ö simulerades och resultaten visar en lägre nivå av slösad elkraft. I både fallen används projicerade kostnader för att utvärdera den tekno-ekonomiska presentandan.

Fastoxid elektrolysörer (SOFC) inom ramen av elkraft-till-gas uppgradering av biogas omfattar det andra energilagringssätt som studerades. Uppgraderingsprocessens mål var att öka metanhalten hos biogasen med direktomvandling av koldioxid genom högtemperatur-elektrolys och -metanisering Denna process visade verkningsgrader för energiomvandling högre än 80%. Däremot är den ekonomiska konkurrenskraften en funktion av elkostnaden, kostnaderna hos de olika komponenterna och gaskostnaden.

Abstract [pt]

A necessidade de integrar o rápido crescimento dos recursos renováveis no setor da geração da energia elétrica exige soluções capazes de mitigar a intermitência destes recursos. As energias renováveis têm o potencial para se tornar a espinha dorsal da produção elétrica nos próximos anos para alcançar os objetivos ambiciosos que dizem respeito à segurança energética e à reducão do impacte ambiental. O armazenamento da energia parece uma solução promissora para melhorar a capacidade das renováveis variáveis (eólica e fotovoltaico) de satisfazerem continuamente a procura de energia elétrica, principalmente através da disponibilização do excesso de energia gerada.

Entre as diferentes opções que podem favorecer a integração dos recursos renováveis intermitentes, as tecnologias para o armazenamento eletroquímico – baterias e células de electrólise – constituem o foco desta tese. Estas abordagens permitem adiar o uso de grandes quantidades de energia a médio-longo prazo, são independentes da localização e são, além do mais, consideradas uma componente estratégica do plano para a descarbonização na União Europeia – a entidade geo-política sobre a qual o trabalho se concentra.

Os sistemas de armazenamento com baterias são analisados para casos de estudo de pequena e grande escala para quantificar os beneficios energético e económico que derivam de um uso mais eficiente dos recursos renovaveis. Para a pequena escala apresenta-se a análise de um sistema de baterias conectado a um sistema fotovoltaico residencial e os resultados são comparados a uma estratégia de demand response para o deslocamento da carga. Para a larga escala, simula-se a integração de uma instalação de baterias no sistema de energia de uma ilha e os resultados mostram um nível muito menor de curtailments de energia renovável. Em ambas as situações, usaram-se os custos projetados das tecnologias para avaliar o seu desempenho técnico-económico.

As células de eletrólise de óxido sólido (Solid Oxide Electrolysis Cells – SOECs) foram analisadas para um processo power-to-gas mediante o upgrading de biogás. Esta tecnologia constitui o segundo tipo de armazenamento eletroquímico de energia que foi estudado. O processo de upgrading serve para aumentar o conteúdo de metano no biogás, convertendo diretamente o dióxido de carbono contido nele, por meio de eletrólise a alta temperatura e metanação. A eficiência de conversão de energia deste processo mostrou-se superior a 80%. Contudo, a viabilidade económica deste conceito depende maioritariamente do custo da eletricidade, do custo dos componentes principais e do preço do gás natural.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. p. 114
Series
TRITA-ITM-AVL ; 2018:43
Keywords
Electrical Energy Storage, Battery Energy Storage, Lithium-ion Batteries, Vanadium Flow Batteries, Power-to-Gas, Electrolysis, Biogas Upgrading, Armazenamento de Energia Elétrica, Armazenamento de Energia em Baterias, Baterias de Iões de Lítio, Baterias de Fluxo de Vanádio, Power-to-Gas, Eletrólise, Upgrading de Biogás, Elenergilagring, batterilagring, litiumjonbatterier, vanadinflödesbatterier, elkraft-till-gas, elektrolys, biogasuppgradering
National Category
Engineering and Technology Energy Engineering Chemical Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-234822 (URN)978-91-7729-940-0 (ISBN)
Public defence
2018-10-08, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
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Note

QC 20180912

Available from: 2018-09-12 Created: 2018-09-11 Last updated: 2018-09-12Bibliographically approved

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