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Techno-economic models in Smart Grids: Demand side flexibility optimization for bidding and scheduling problems
Full text linkSummary of the thesis
Introduction of power-intensive appliances such as electric vehicle chargers and induction cooktops, as well as technologies for local renewable electricity generation from solar panels and wind turbines will provide challenges for distribution in the coming years. High power peaks, rapid power changes and less predictability will increase the need for transmission capacity and reserves. Traditionally, such problems are met with costly investments in new capacity. An alternative approach is to use flexibility from the end users, which means that generation and consumption of electricity is changed as a response to prices or other signals. Introduction of batteries in buildings, advanced metering infrastructure (AMI) and the Internet of Things (IoT) increase the potential for demand side flexibility. Altogether, these technologies constitute the concept denoted the Smart Grid.
To realize this increased flexibility potential, financial incentives must be introduced. Major changes are therefore expected in the electricity market in the coming years, including introduction of new, innovative contract types and business models, changes in market designs and the establishment of new market roles.
To maximize the benefit of demand side flexibility, there is a need for development of new decision support models. This thesis proposes and analyzes models for trading in different markets and for the scheduling of flexible devices in an operational situation. The models are based on operations research. The decision problems are mathematically formulated, and a particular focus is on how to handle uncertain parameters, such as consumption, generation and market prices. Stochastic programming is used for this purpose.
The thesis consists of four articles. In Article 1 a basic model is established where flexibility is divided into different classes. The article analyzes a prosumer in the retail market, where flexibility gives cost savings by exploiting price variations over a day, between energy carriers and by reducing the demand charge at the grid tariffs. In Article 2 several prosumers are coordinated via an aggregator who buys and sells electricity in a spot market and where imbalances are settled in a balancing market. Article 3 focuses on flexibility trade, where the value of an aggregated flexibility portfolio is maximized by trading in three sequential markets. The last article analyzes the decision problem to a service provider who operates a charging site for electric vehicles, where the capacity is limited. All articles contain case studies that have been conducted in close cooperation with companies in the Norwegian electricity market.Sammendrag av avhandlingen
Innføring av effektkrevende forbruksapparater som elbiler-ladere og induksjonskoketopper, samt teknologi for lokal, fornybar elektrisitetsproduksjon fra sol og vind vil gi utfordringer for distribusjonsnettet i årene som kommer. Høye effekttopper, raske effektendringer og mindre forutsigbarhet vil gi økt behov for overføringskapasitet og reserver. Tradisjonelt vil slike problemer møtes med kostnadskrevende investeringer i ny kapasitet. En alternativ tilnærming er å benytte fleksibilitet hos sluttbrukerne, som innebærer at innmating og uttak av elektrisitet endres som følge av priser eller andre signaler. Innføring av batterier i bygg, avanserte målings- og styringssystemer (AMS) og tingenes internett (IoT) gjør at potensialet for sluttbrukerfleksibilitet er økende. Til sammen utgjør disse teknologiene konseptet som benevnes det smarte nettet, Smart Grid.
For å realisere dette økte fleksibilitetspotensialet, må økonomiske insentiver innføres. Det forventes derfor store endringer i elektrisitetsmarkedet i årene som kommer, blant annet ved introduksjon av nye, innovative kontraktstyper og forretningsmodeller, endringer i markedsdesign og etablering av nye markedsroller.
For å maksimere nytteverdien av sluttbrukerfleksibilitet, vil det være behov for utvikling av nye beslutningsstøttemodeller. Denne avhandlingen foreslår og analyserer modeller for handel i ulike markeder og for planlegging av hvordan fleksible enheter skal benyttes i en driftssituasjon. Modellene baseres på operasjonsanalyse. Beslutningsproblemene modelleres matematisk, og det fokuseres spesielt på hvordan optimale beslutninger skal tas under forutsetning av at enkelte parametere, som forbruk, produksjon og markedspriser, kan være usikre på beslutningstidspunktet. Til dette benyttes stokastisk programmering.
Avhandlingen består av fire artikler. I artikkel 1 etableres en grunnleggende modell der fleksibilitet deles inn i ulike klasser. Artikkelen analyserer en prosument i sluttbrukermarkedet, der fleksibiliteten gir kostnadsbesparelser ved å utnytte prisvariasjoner over døgnet, mellom energibærere og ved å redusere effektledd på nettleiekontrakter. I artikkel 2 koordineres flere prosumenter via en aggregator som kjøper og selger elektrisitet i et spotmarked og der ubalanser avregnes i et balansemarked. Artikkel 3 rendyrker fleksibilitetshandel, der verdien av en aggregert fleksibilitetsportefølje maksimeres ved å handle i tre sekvensielle markeder. Den siste artikkelen analyserer beslutningsproblemet til en tjenestetilbyder som drifter et ladested for elbiler, der kapasiteten er begrenset. Alle artiklene inneholder case-studier som er gjennomført i tett samarbeid med aktører i det norske kraftmarkedet
Methodology for assessing short-term flexibility in demand-side assets
Full text linkGlobal electricity grids, and especially the distribution grids, encounter new challenges during the transmission to a sustainable energy chain. Decarbonization involves electrification and a massive deployment of variable renewable energy sources, which ultimately increase the complexity at the demand-side of the grid. There is a growing need to promote demand-side flexible power and to actively utilize it to deal with an anticipated increase of local congestions and ramping problems. Local flexibility markets have emerged to provide a platform where the distribution grid operator or another flexibility buyer can activate demand-side flexibility that is offered by prosumers, e.g. balance the grid.
In order for a prosumer to make its flexible power accessible on markets, new methodologies are needed. The main goal of this thesis is to develop a methodology for assessing short-term flexible power in a demand-side asset. Such a methodology has been developed for a generic flexible asset and consists of four stages: (1) load forecasts (2) physical asset models (3) estimation of available flexibility and at last (4) the shaping of a flexibility bid for flexibility markets. The thesis gives conceptual descriptions on how the methodology is implemented for each of five different flexible assets. Python is used as a tool for implementing the methodology, using the package Keras to make RNN forecast models and object-oriented programming to create an Asset class framework.
The methodology is applied on a real use-case scenario where multi-step RNN forecast models are created, using real consumption data for an asset that powers a cooling storage. Data are provided by ASKO (end-user) and eSmart (smart grid company). The forecast results seems promising even with relative short data, but must be optimized, tested on multiple test sets and include explanatory variables. Many assumptions had to be made for the asset parameters and the final hypothetical flexibility estimates were shown to be sensitive to these choices. Nevertheless, the methodology has been proven to work and is applied to a full demonstration of a bid procedure. Applied examples are also given for other assets, such as water heater and a battery.
The conclusion is that the methodology itself is stable and applicable to many different assets. Its results however, being the flexibility estimates, are prone to be very wrong if the constitutional stages in the methodology are weakly implemented. A strength is that each stage is flexible to be changed or improved without disturbing the flow of the methodology. For the methodology to work successfully, it is of utmost importance that accurate load (or production) forecasts and correct asset parameters are provided
Modelling dimensioning el-specific load for apartments in Fjellhamar Bruk
Full text linkData fra AMS-målere i norske husholdninger viser at dimensjonerende last i leiligheter blir betydelig overdimensjonert i planleggingsfasen. Dette gjelder spesielt for leiligheter der elektrisitet er energibærer for el-spesifikke laster. Sentrale årsaker er en samtidighetsfaktor som tallfestes for høyt og en planleggingsprosess med sikkerhetsmarginer i flere ledd.
Denne oppgaven har som hensikt å finne dimensjonerende last og tilhørende lastkurver for det el-spesifikke behovet for én leilighet, i et område bestående av 1500 leiligheter i Fjellhamar Bruk. Dette gjøres ved bruk en statistisk modell. For å tilse at dimensjonerende last fra modellen er tilstrekkelig, gjøres en evaluering mot reelle måledata fra AMS-målerne. Deretter undersøkes det hvordan samtidighetsfaktoren påvirker dimensjonerende last for én leilighet i et område bestående av 1500 leiligheter. Til sist skal potensialet for forbrukerfleksibilitet undersøkes, med hensikt å redusere forbruket i timene som er avgjørende for dimensjonerende last. Overordnede problemstilling for oppgaven er: Er dimensjonerende last på 1 kW per leilighet tilstrekkelig i et område med 1500 leiligheter ved Fjellhamar Bruk der elektrisitet kun brukes til el-spesifikke tjenester?
Resultatene ved evalueringen av den statistiske modellen tilsier at metoden ikke er tilstrekkelig for bruk ved dimensjonering. Dimensjonerende last fra modellen tilsa en dimensjonering på 0,95 kW for én leilighet, der reelle målinger tilsa en maks last per time på 1,15 kW per leilighet. Tidspunktet i modellen var time 20, og i time 19 i reelle måledata. Videre vil samtidighetsfaktoren i modellen føre til en overestimering av dimensjonerende last. Dette viser at modellen ikke er tilstrekkelig, da både størrelse, tidspunkt og samtidighetsfaktoren ikke gjenspeiler reelle forhold.
For å finne dimensjonerende last genereres nye parametere. Reelle AMS-data ble inndata i den statistiske modellen. Dette ga en tilstrekkelig dimensjonerende last med tilhørende lastkurve. Samtidighetsfaktor ble korrigert til å gjenspeile dimensjonerende last for 1500 enheter. Noe som resulterte i en dimensjonerende last for én leilighet, i et område med 1500 leiligheter, på 1,05 kWh/h. Fleksibilitetspotensialet i Fjellhamar ble kartlagt i to ulike scenario. I dårligste scenario kan dimensjonerende last reduseres til 1,02 kWh/h per leilighet. I beste scenarioet kan dimensjonerende last reduseres til 1,00 kWh/h per leilighet.Measurements from the smart meters in Norwegian households shows that the dimensions of the electrical infrastructure are being highly overestimated in the design process. This is especially the case for households where electricity is the carrier for el-specific loads. Reasons for this overestimating is a coincidence factor that is set too high and a planning process where margins for safety are added by different stakeholders throughout the design process.
The purpose of this thesis is to find the dimensioning load and associated load curves for the el-specific consumption for one apartment, in an area consisting of 1500 apartments. A statistical model is evaluated by using actual measurements from the smart meters. The coincidence factor is investigated to see how it affects the dimensioning load for one apartment, in an area consisting of 1500 apartments. The potential of demand-response is investigated to reduce the dimensioning load, by moving the consumption in dimensioning hours. This leads to the research question for this thesis: Is a dimensioning load of 1 kW sufficient for one apartment in an area consisting of 1500 apartments in Fjellhamar Bruk where electricity is used for el-specific services?
The evaluation of the model indicates that the statistical model is not sufficient for dimensioning. The model gives a dimensioning load of 0,95 kW for one apartment while measured values show a peak-load of 1,15 kW from one apartment. Hour 20 was the hour of dimensioning load from the model, and hour 19 in the measured load. Furthermore, the coincidence factor in the model is too high and will lead to an overestimation of the dimensioning load. This result show that the model is insufficient when the model is underestimating the size and time of peak-load, and it doesn’t reflect the coincidence factor when the numbers of households are larger than 38.
To find the dimensioning load, new parameters are generated from the model. The measured values were used as input data in the statistical model. This provided a sufficient sizing and a correct timing of the dimensioning load. The coincidence factor was corrected to reflect a dimensioning load of 1500 apartments. The results of the gives a dimensioning load of 1,05 for one apartment in an area consisting of 1500 apartments. The potential of utilizing demand-response to reduce the dimensioning load was investigated in two different scenarios, best-case- and worst-case scenario. The worst-case scenario gives a dimensioning load of 1,02 kW for one apartment. The best-case scenario gives a dimensioning load of 1,00 kW for one apartment.submittedVersionM-FORN
Modellering av dimensjonerende el-spesifikk last for leiligheter i Fjellhamar Bruk
No full textData fra AMS-målere i norske husholdninger viser at dimensjonerende last i leiligheter blir betydelig overdimensjonert i planleggingsfasen. Dette gjelder spesielt for leiligheter der elektrisitet er energibærer for el-spesifikke laster. Sentrale årsaker er en samtidighetsfaktor som tallfestes for høyt og en planleggingsprosess med sikkerhetsmarginer i flere ledd.
Denne oppgaven har som hensikt å finne dimensjonerende last og tilhørende lastkurver for det el-spesifikke behovet for én leilighet, i et område bestående av 1500 leiligheter i Fjellhamar Bruk. Dette gjøres ved bruk en statistisk modell. For å tilse at dimensjonerende last fra modellen er tilstrekkelig, gjøres en evaluering mot reelle måledata fra AMS-målerne. Deretter undersøkes det hvordan samtidighetsfaktoren påvirker dimensjonerende last for én leilighet i et område bestående av 1500 leiligheter. Til sist skal potensialet for forbrukerfleksibilitet undersøkes, med hensikt å redusere forbruket i timene som er avgjørende for dimensjonerende last. Overordnede problemstilling for oppgaven er: Er dimensjonerende last på 1 kW per leilighet tilstrekkelig i et område med 1500 leiligheter ved Fjellhamar Bruk der elektrisitet kun brukes til el-spesifikke tjenester?
Resultatene ved evalueringen av den statistiske modellen tilsier at metoden ikke er tilstrekkelig for bruk ved dimensjonering. Dimensjonerende last fra modellen tilsa en dimensjonering på 0,95 kW for én leilighet, der reelle målinger tilsa en maks last per time på 1,15 kW per leilighet. Tidspunktet i modellen var time 20, og i time 19 i reelle måledata. Videre vil samtidighetsfaktoren i modellen føre til en overestimering av dimensjonerende last. Dette viser at modellen ikke er tilstrekkelig, da både størrelse, tidspunkt og samtidighetsfaktoren ikke gjenspeiler reelle forhold.
For å finne dimensjonerende last genereres nye parametere. Reelle AMS-data ble inndata i den statistiske modellen. Dette ga en tilstrekkelig dimensjonerende last med tilhørende lastkurve. Samtidighetsfaktor ble korrigert til å gjenspeile dimensjonerende last for 1500 enheter. Noe som resulterte i en dimensjonerende last for én leilighet, i et område med 1500 leiligheter, på 1,05 kWh/h. Fleksibilitetspotensialet i Fjellhamar ble kartlagt i to ulike scenario. I dårligste scenario kan dimensjonerende last reduseres til 1,02 kWh/h per leilighet. I beste scenarioet kan dimensjonerende last reduseres til 1,00 kWh/h per leilighet
Second-life electric vehicle batteries in the Norwegian power system : a feasibility study
Full text linkAs a result of the acknowledgment of climate change and the agreements set forth to combat it, the share of renewable energies in our power systems is growing. Due to the interlinking of the European power systems, imbalances can be expected to increase in the Norwegian grid as well as in other European countries. Combined with the rising amount of distributed energy production and the electrification of the Norwegian society, it is evident that new solutions are needed.
This thesis investigates the use of used electric vehicle batteries in second-life battery systems, with the goal of determining its feasibility in the Norwegian power system. Several aspects are examined in a literature review: suitability, availability, costs, laws and regulations, and the repurposing process. In addition, an in-depth use case is conducted for the peak shaving application in south-eastern Norway.
The use case employed consumption data from one substation and its associated consumer nodes and explored peak shaving in both households and at the associated substation. Household peak shaving was achieved, but to what degree was dependent on the individual consumption patterns. The cost of the battery system was too high for it to be reasonable for households to implement these systems at current electricity prices. Substation peak shaving was most efficiently accomplished by using one large battery at the substation, although the collected peak shaving of the households also shaved the peaks at the substation. The cost of one large battery is expected to be considerably lower than the aggregated cost of the household batteries needed to achieve the same peak shaving effect as one larger battery, but it is not necessarily profitable in comparison to upgrading the substation.
The literature study revealed promising results with regards to capabilities, availability of batteries, and an increasing experience level. However, some questions remain regarding the second-life aging and lifespan. Lifespans of 4-29 years have been suggested, depending on the application. Also, guidelines and clearer regulations are needed to ensure safe handling during processing. How feasible or profitable a second-life battery system is, depends on the application, battery price, and repurposing cost. Balancing services and frequency regulation might be feasible applications today, while others could become feasible within the decade. In conclusion, second-life battery systems could have a future in the Norwegian power system, given some conditions and developments. However, it is not likely until 2025 at the earliest.Som et resultat av målsetningene til ulike klimaavtaler, er en økende andel fornybar energi på vei inn i kraftsystemene. Det europeiske kraftsystemet knyttes stadig mer sammen og resulterer i utfordringer for nettet, både i Norge og i Europa for øvrig. Dette, kombinert med en økende andel av distribuert kraftproduksjon og elektrifiseringen av det norske samfunnet, gir opphav til et behov for nye løsninger.
Denne masteroppgaven har som hovedmål å finne ut om gjenbrukte elbilbatterier har en fremtid i det norske kraftsystemet. For å avgjøre dette, er flere faktorer blitt undersøkt i en litteraturstudie: egnethet, tilgjengelighet, kostnader, lover og forskrifter og hvordan slike batterier kan gjenbrukes. I tillegg til litteraturstudiet er det uført en case-studie for såkalt "peak shaving" i Hvaler, sør-øst i Norge.
Case-studiet er basert på forbruksdata fra en nettstasjon og dens tilknyttede kunder, og undersøker peak shaving ved hjelp av simuleringer for både husholdninger og nettstasjonen de er knyttet til. Forbrukskutt ble oppnådd i varierende grad for husholdningene, avhengig av forbruksmønster. Kostanden til batterisystemet viste seg å uansett være for høy til at det vil lønne seg for husholdningskunder. Den samlede effekten av forbrukskutt hos husholdningene førte til redusert forbruk hos nettstasjonen også, men ett enkelt stort batteri gjorde jobben mer effektivt. I tillegg er kostnaden forventet å være betydelig lavere, men ikke nødvendigvis et mer lønnsomt alternativ til en eventuell oppgradering av nettstasjonen.
Litteraturstudiet ga lovende resultater når det kom til egnethet og tilgjengelighet av batterier. Kunnskapsnivået ser også ut til å være stigende. På den andre siden gjenstår en del spørsmål angående aldring og levetid for gjenbrukte batterier. En levetid på 4-29 år har blitt foreslått, avhengig av bruksområde. Det er også behov for tydeligere retningslinjer og forskrifter for håndtering av brukte elbilbatterier. Lønnsomheten til disse batterisystemene avhenger av batteripris, prosesseringskostnader og bruksområde. Systemer brukt i nettjenester, som frekvensregulering, kan være levedyktige allerede i dag. Andre bruksområder kan bli lønnsomme innen dette tiåret. Altså kan gjenbrukte elbilbatterier ha en fremtid i det norske kraftsystemet, gitt noen forutsetninger. Likevel virker det ikke sannsynlig at dette skjer før tidligst 2025.M-M
Techno-economic models in Smart Grids: Demand side flexibility optimization for bidding and scheduling problems
No full textSummary of the thesis
Introduction of power-intensive appliances such as electric vehicle chargers and induction cooktops, as well as technologies for local renewable electricity generation from solar panels and wind turbines will provide challenges for distribution in the coming years. High power peaks, rapid power changes and less predictability will increase the need for transmission capacity and reserves. Traditionally, such problems are met with costly investments in new capacity. An alternative approach is to use flexibility from the end users, which means that generation and consumption of electricity is changed as a response to prices or other signals. Introduction of batteries in buildings, advanced metering infrastructure (AMI) and the Internet of Things (IoT) increase the potential for demand side flexibility. Altogether, these technologies constitute the concept denoted the Smart Grid.
To realize this increased flexibility potential, financial incentives must be introduced. Major changes are therefore expected in the electricity market in the coming years, including introduction of new, innovative contract types and business models, changes in market designs and the establishment of new market roles.
To maximize the benefit of demand side flexibility, there is a need for development of new decision support models. This thesis proposes and analyzes models for trading in different markets and for the scheduling of flexible devices in an operational situation. The models are based on operations research. The decision problems are mathematically formulated, and a particular focus is on how to handle uncertain parameters, such as consumption, generation and market prices. Stochastic programming is used for this purpose.
The thesis consists of four articles. In Article 1 a basic model is established where flexibility is divided into different classes. The article analyzes a prosumer in the retail market, where flexibility gives cost savings by exploiting price variations over a day, between energy carriers and by reducing the demand charge at the grid tariffs. In Article 2 several prosumers are coordinated via an aggregator who buys and sells electricity in a spot market and where imbalances are settled in a balancing market. Article 3 focuses on flexibility trade, where the value of an aggregated flexibility portfolio is maximized by trading in three sequential markets. The last article analyzes the decision problem to a service provider who operates a charging site for electric vehicles, where the capacity is limited. All articles contain case studies that have been conducted in close cooperation with companies in the Norwegian electricity market
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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