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Photovoltaic/battery system sizing for rural electrification in Bolivia:Considering the suppressed demand effect
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.ORCID iD: 0000-0003-1878-1530
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes.ORCID iD: 0000-0002-1351-9245
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes.ORCID iD: 0000-0001-8271-7512
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2019 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 235, p. 519-528Article in journal (Refereed) Published
Abstract [en]

Rural electrification programs usually do not consider the impact that the increment of demand has on thereliability of off-grid photovoltaic (PV)/battery systems. Based on meteorological data and electricity consumptionprofiles from the highlands of Bolivian Altiplano, this paper presents a modelling and simulationframework for analysing the performance and reliability of such systems. Reliability, as loss of power supplyprobability (LPSP), and cost were calculated using simulated PV power output and battery state of chargeprofiles. The effect of increasing the suppressed demand (SD) by 20% and 50% was studied to determine howreliable and resilient the system designs are. Simulations were performed for three rural application scenarios: ahousehold, a school, and a health centre. Results for the household and school scenarios indicate that, toovercome the SD effect, it is more cost-effective to increase the PV power rather than to increase the batterycapacity. However, with an increased PV-size, the battery ageing rate would be higher since the cycles areperformed at high state of charge (SOC). For the health centre application, on the other hand, an increase inbattery capacity prevents the risk of electricity blackouts while increasing the energy reliability of the system.These results provide important insights for the application design of off-grid PV-battery systems in ruralelectrification projects, enabling a more efficient and reliable source of electricity.

Place, publisher, year, edition, pages
Elsevier, 2019. Vol. 235, p. 519-528
Keywords [en]
photovoltaic energy storage, state of charge, renewable energy, rural electrification, li ion batteries
National Category
Energy Systems
Research subject
Energy Technology
Identifiers
URN: urn:nbn:se:kth:diva-295635DOI: 10.1016/j.apenergy.2018.10.084ISI: 000458942800043Scopus ID: 2-s2.0-85056217184OAI: oai:DiVA.org:kth-295635DiVA, id: diva2:1556973
Funder
Sida - Swedish International Development Cooperation Agency
Note

QC 20210526

Available from: 2021-05-24 Created: 2021-05-24 Last updated: 2022-06-25Bibliographically approved
In thesis
1. Lithium-ion batteries for off-grid PV-systems
Open this publication in new window or tab >>Lithium-ion batteries for off-grid PV-systems
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis provides a comprehensive and detailed analysis on the effect ofthe battery operation strategy on the lifetime of commercial lithium-ionbatteries and on the economics of off-grid photovoltaic (PV)-batterysystems.Lithium-ion batteries play a key role in the transition to a fossil-freesociety. Compared to electric vehicles, stationary energy storage hasdifferent requirements for the performance and lifetime of batteries.Although optimal battery design is critical to achieve high energy densityand longer lifetime, operation plays an important role in preventingpremature performance degradation. Understanding the effects ofsuppressed demand, geographical location, and application on system lifecycle costs also enables optimal system design.Load profiles for three applications were estimated and implemented in asimulation model, along with meteorological data for three locations andthe suppressed demand (SD) effect. Using the hourly state of charge (SOC)profiles, four battery operation strategies were designed using partialcycling with different cut-off voltages and two state of charge windows(ΔSOC). Commercial cells were used for the experimental tests. After over1000 cycles a post-mortem characterization was performed.The experiments revealed the cause of premature degradation at high SOCoperation to be a combination of impedance rise in the positive electrodeand loss of lithium inventory at the negative electrode leading to decreaseof capacity. Studies on the impedance spectra of the cells using physicsbasedmodeling revealed a loss of conductivity between particles in thepositive electrode. At system level, as the SD increases, so does theoperational ΔSOC width, while the reliability of the system decreases. Wedefined the reliability as loss of power supply probability. Finally,optimization of cost and reliability, revealed that an optimal system designfavors a battery operation strategy with wider ΔSOC instead of batterylifetime.

Abstract [sv]

Denna avhandling ger en omfattande och detaljerad analys gällande hurupp och urladdningsstrategin påverkar livslängden för kommersiellalitium-jonbatterier och ekonomin för solcellssystem som är frikoppladefrån elnätet. Litiumjon-batterier spelar en nyckelroll i övergången till ett fossilfritt samhälle. Jämför man med elfordon, så ställer stationära energilagringssystem andra krav på prestanda och livslängd för dess batterier. Även om optimal batteridesign är kritisk för att uppnå hög energidensitet och lång livslängd så spelar användningen (driften) av batteriet en viktig roll för att förhindra för tidig prestanda försämring. Genom att förstå effekterna av undertryckt efterfrågan, geografisk placering och applikation på systemets livscykelkostnad möjliggörs optimal systemdesign. Elkonsumtion profiler för tre applikationer beräknades och infogades i en simuleringsmodell tillsammans med meteorologiska data för tre geografiska placeringar, samt effekten av undertryckt efterfrågan (SD). Med hjälp av erhållna timprofiler för laddningsnivå, designades fyrabatteridrifts-strategier som använder partiella cykler vid tre olika spänningsnivåer och två laddningstillståndsintervall (ΔSOC). Kommersiella celler användes för de experimentella testerna. Efter mer än 1000 cykler och kontinuerliga mätningar under åldringsprocessen, utfördes en post-mortem karakterisering. Experimenten visade att orsaken till för tidig prestandaförsämring vid drift vid höga laddningstillstånd (SOC) är en kombination av impedansökning hos den positiva elektroden och inlagring av litium i den negativa elektroden vilket leder till kapacitetsförlust. Studier av impedansspektra för cellerna där fysikaliska modeller använts avslöjade en minskning avledningsförmåga mellan partiklarna i den positiva elektroden. När man på systemnivå analyserade inverkan av undertryckt efterfrågan så observerades att laddningstillståndsfönstret ökade och en försämrad systempålitlighet. Den avslutande optimeringen av kostnad och pålitlighet visade att en optimal systemdesign bör använda en driftstrategi för batteriet med ett bredare laddningstillståndsintervall.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2021. p. 57
Series
TRITA-CBH-FOU ; 2021:24
Keywords
Lithium-ion batteries, aging, partial cycles, DVA, EIS, NCA, stationary energy systems, PV systems, rural electrification.
National Category
Energy Systems
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-295688 (URN)978-91-7873-918-9 (ISBN)
Public defence
2021-06-14, https://kth-se.zoom.us/meeting/register/u5Iuc-utrzojHd1XkYyhqRKmF999ZWgqVqwy, Stockholm, 15:00 (English)
Opponent
Supervisors
Funder
Sida - Swedish International Development Cooperation Agency
Note

QC 2021-05-25

Available from: 2021-05-25 Created: 2021-05-25 Last updated: 2022-06-25Bibliographically approved

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Publisher's full textScopushttps://doi.org/10.1016/j.apenergy.2018.10.084

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Benavente Araoz, Fabian AndresCampana, Pietro EliaZhang, YangLindbergh, Göran

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