Operating Hydrogen-Based Energy Storage Systems in Wind Farms for Smooth Power Injection: A Penalty Fees Aware Model Predictive Control

Smooth power injection is one of the possible services that modern wind farms could provide in the not-so-far future, for which energy storage is required. Indeed, this is one among the three possible operations identified by the International Energy Agency (IEA)-Hydrogen Implementing Agreement (HIA) within the Task 24 final report, that may promote their integration into the main grid, in particular when paired to hydrogen-based energy storages. In general, energy storage can mitigate the inherent unpredictability of wind generation, providing that they are deployed with appropriate control algorithms. On the contrary, in the case of no storage, wind farm operations would be strongly affected, as well as their economic performances since the penalty fees wind farm owners/operators incur in case of mismatches between the contracted power and that actually delivered. This paper proposes a Model Predictive Control (MPC) algorithm that operates a Hydrogen-based Energy Storage System (HESS), consisting of one electrolyzer, one fuel cell and one tank, paired to a wind farm committed to smooth power injection into the grid. The MPC relies on Mixed-Logic Dynamic (MLD) models of the electrolyzer and the fuel cell in order to leverage their advanced features and handles appropriate cost functions in order to account for the operating costs, the potential value of hydrogen as a fuel and the penalty fee mechanism that may negatively affect the expected profits generated by the injection of smooth power. Numerical simulations are conducted by considering wind generation profiles from a real wind farm in the center-south of Italy and spot prices according to the corresponding market zone. The results show the impact of each cost term on the performances of the controller and how they can be effectively combined in order to achieve some reasonable trade-off. In particular, it is highlighted that a static choice of the corresponding weights can lead to not very effective handling of the effects given by the combination of the system conditions with the various exogenous’, while a dynamic choice may suit the purpose instead. Moreover, the simulations show that the developed models and the set-up mathematical program can be fruitfully leveraged for inferring indications on the devices’ sizing.publishedVersio

Multi-Sine EIS for Early Detection of PEMFC Failure Modes

Electrochemical impedance spectroscopy (EIS) is a powerful technique that can be used to detect small changes in electrochemical systems and subsequently identify the source of the change. While promising, analysis is often non-intuitive and time-consuming, where collection times of a single EIS spectrum can reach several minutes. To circumvent the long collection times associated with traditional EIS measurements, a multi-sine EIS technique was proposed in which the simultaneous application of many frequencies can reduce the acquisition time to less than a minute. This shortened acquisition time opens the possibility to use multi-sine EIS as a real-time diagnostic tool for monitoring the state-of-health of commercial fuel cell systems. In this work, a single-cell proton exchange membrane fuel cell (PEMFC) was characterised using multi-sine EIS, by establishing steady-state impedance response under baseline conditions before systematically changing operating conditions and monitoring the dynamic changes of the impedance response. Our initial results demonstrate that full multi-sine EIS spectra, encompassing a frequency range from 50 kHz to 0.5 Hz, can be collected and analysed using simple equivalent circuit models in 50 s. It is shown that this timeframe is sufficiently short to capture the dynamic response of the fuel cell in response to changing operating conditions, thereby validating the use of multi-sine EIS as a diagnostic technique for in-situ monitoring and fault detection during fuel cell operation.publishedVersio

Value of green hydrogen when curtailed to provide grid balancing services

This paper evaluates the potential of grid services in France, Italy, Norway and Spain to provide an alternative income for electrolysers producing hydrogen from wind power. Grid services are simulated with each country's data for 2017 for energy prices, grid services and wind power profiles from relevant wind parks. A novel metric is presented, the value of curtailed hydrogen, which is independent from several highly uncertain parameters such as electrolyser cost or hydrogen market price. Results indicate that grid services can monetise the unused spare capacity of electrolyser plants, improving their economy in the critical deployment phase. For most countries, up-regulation yields a value of curtailed hydrogen above 6 €/kg, over 3 times higher than the EU's 2030 price target (without incentives). However, countries with large hydro power resources such as Norway yield far lower results, below 2 €/kg. The value of curtailed hydrogen also decreases with hydrogen production, corresponding to the cases of symmetric and down-regulation.This publication has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under the European Union's Horizon 2020 research and innovation programme under grant agreement No. 779469. Any contents herein reflect solely the authors' view. The FCH 2JU and the European Commission are not responsible for any use that may be made of the information herein contained. TECNALIA is a “CERVERA Technology Centre of Excellence” recognised by the Spanish Ministry of Science and Innovation. The authors wish to thanks Stefano Rossi of ARERA for his advices on the Italian energy market and regulation aspects

Control of Fuel Cells

This thesis deals with control of fuel cells, focusing on high-temperature proton-exchange-membrane fuel cells. Fuel cells are devices that convert the chemical energy of hydrogen, methanol or other chemical compounds directly into electricity, without combustion or thermal cycles. They are efficient, scalable and silent devices that can provide power to a wide variety of utilities, from portable electronics to vehicles, to nation-wide electric grids. Whereas studies about the design of fuel cell systems and the electrochemical properties of their components abound in the open literature, there has been only a minor interest, albeit growing, in dynamics and control of fuel cells. In the relatively small body of available literature, there are some apparently contradictory statements: sometimes the slow dynamics of fuel cells is claimed to present a control problem, whereas in other articles fuel cells are claimed to be easy to control and able to follow references that change very rapidly. These contradictions are mainly caused by differences in the sets of phenomena and dynamics that the authors decided to investigate, and also by how they formulated the control problem. For instance, there is little doubt that the temperature dynamics of a fuel cell can be slow, but users are not concerned with the cell’s temperature: power output is a much more important measure of performance. Fuel cells are very multidisciplinary systems, where electrical engineering, electrochemistry, chemical engineering and materials science are all involved at various levels; it is therefore unsurprising that few researchers can master all of these branches, and that most of them will neglect or misinterpret phenomena they are unfamiliar with. The ambition of this thesis is to consider the main phenomena influencing the dynamics of fuel cells, to properly define the control problem and suggest possible approaches and solutions to it. This thesis will focus on a particular type of fuel cell, a variation of proton-exchange-membrane fuel cells with a membrane of polybenzimidazole instead of the usual, commercially available Nafion. The advantages of this particular type of fuel cells for control are particularly interesting, and stem from their operation at temperatures higher than those typical of Nafion-based cells: these new cells do not have any water-management issues, can remove more heat with their exhaust gases, and have better tolerance to poisons such as carbon monoxide. The first part of this thesis will be concerned with defining and modelling the dynamic phenomena of interest. Indeed, a common mistake is to assume that fuel cells have a single dynamics: instead, many phenomena with radically different time scales concur to define a fuel-cell stack’s overall behaviour. The dynamics of interest are those of chemical engineering (heat and mass balances), of electrochemistry (diffusion in electrodes, electrochemical catalysis) and of electrical engineering (converters, inverters and electric motors). The first part of the thesis will first present some experimental results of importance for the electrochemical transient, and will then develop the equations required to model the four dynamic modes chosen to represent a fuel-cell system running on hydrogen and air at atmospheric pressure: cathodic overvoltage, hydrogen pressure in the anode, oxygen fraction in the cathode and stack temperature. The second part will explore some of the possible approaches to control the power output from a fuel-cell stack. It has been attempted to produce a modularised set of controllers, one for each dynamics to control. It is a major point of the thesis, however, that the task of controlling a fuel cell is to be judged exclusively by its final result, that is power delivery: all other control loops, however independent, will have to be designed bearing that goal in mind. The overvoltage, which corresponds nonlinearly to the rate of reaction, is controlled by operating a buck-boost DC/DC converter, which in turn is modelled and controlled with switching rules. Hydrogen pressure, being described by an unstable dynamic equation, requires feedback to be controlled. A controller with PI feedback and a feedforward part to improve performance is suggested. The oxygen fraction in the cathodic stream cannot be easily measured with a satisfactory bandwidth, but its dynamics is stable and disturbances can be measured quite precisely: it is therefore suggested to use a feedforward controller. Contrary to the most common approach for Nafion-based fuel cells, temperature is not controlled with a separate cooling loop: instead, the air flow is used to cool the fuel-cell stack. This significantly simplifies the stack design, operation and production cost. To control temperature, it is suggested to use a P controller, possibly with a feedforward component. Simulations show that this approach to stack cooling is feasible and poses no or few additional requirements on the air flow actuator that is necessary to control air composition in the cathode

Faktagrunnlag til Akershus Fylkeskommunes hydrogenstrategi

-På oppdrag av Akershus Fylkeskommune har SINTEF utarbeidet dette faktagrunnlaget til Akershus Fylkeskommunes hydrogenstrategi. Denne rapporten omtaler status og forventet utvikling for hydrogenteknologien, både hydrogenforbrukere og forsyningsinfrastruktur, samt anbefalinger til Akershus Fylkeskommune for dens videre hydrogensatsing. Flere hydrogenteknologier er i dag kommersielt tilgjengelige, nemlig flere privatbiler, bagasjehåndterings- og gaffeltrucker, busser, persontog og ubåter. Utviklingen fremover forventes å fokusere på større applikasjoner som lastebiler, ferger, skip og godstog. Infrastrukturen som er nødvendig for at privatbilister skal velge å kjøpe hydrogenbil er stor og omfattende, og det er derfor viktig at det utvikles på en økonomisk bærekraftig måte; dette kan gjerne skje ved at hydrogenstasjoner kobles til industrielle brukere som kan benytte hydrogenet i en flåte kjøretøy, mens stasjonene beholdes åpne til eksterne brukere. Det anbefales å satse i første omgang på drosjer, logistikk og busser, da alle ledd i teknologien er kommersielt tilgjengelig; ettersom teknologien rulles ut til markedet, kan lastebiler, ferger, skip, og andre industrielle applikasjoner komme i fokus. Privateide hydrogenbiler vil etablere seg først når et stort nettverk av hydrogenstasjoner vil ha utviklet seg, og vil derfor etablere seg senere enn andre hydrogenteknologier. Oppdragsgiver: Akershus fylkeskommun

Zero-Emission Rail in Czechia: Techno-economic analysis of lines R14, R21, R22, R25, R26, R27, SP14, U28

This report analyses several representative regional, non-electrified rail lines in Czechia and evaluates different zero-emission technologies for their electrification: hydrogen, batteries, partial and full catenary. Single-train simulations are set up for every line to calculate energy requirements and state-of-charge profiles for batteries; the resulting data is fed into a detailed techno-economic analysis to rank the technologies. The results indicate that some lines are best served by hydrogen, other ones by batteries, which in some cases may be cheaper than diesel operation overall; catenary electrification (predictably, as these are all non-electrified lines) is always far more expensive.Zero-Emission Rail in Czechia: Techno-economic analysis of lines R14, R21, R22, R25, R26, R27, SP14, U28ISBN: 978-82-14-07242-6publishedVersio

The Giantleap Project: Improving the reliability of hydrogen buses

<p>Presentation of the general status of hydrogen technology, incentives for zero-emission vehicles in Norway and their success and unintended consequences, how batteries and hydrogen differ, and how the Giantleap project fits into this.</p

Brenselceller i ASKOs distribusjonsbiler. Forprosjekt for å verifisere egnethet

Muligheten til å benytte et brenselcellesystem med dieselreformering i distribusjonsbiler ble undersøkt. ASKO Midt-Norge har biler i forskjellige størrelser og to typer kjølesystemer, nemlig med dieselaggregat og med flytende CO₂. Brenselcellesystemet som er foreslått av PowerCell, PowerPac, ble studert for egnethet i disse distribusjonsbilene.Det ble foretatt en statistisk analyse av kjøremønstrene av forskjellige distribusjonsbiler, som viser at disse endrer seg lite med årstidene, men er ganske forskjellige bilene imellom.PowerPac egner seg ikke for å erstatte dieselaggregater, da det ikke har tilstrekkelig effekt, leverer elektrisitet i uegnet form, og er heller ikke testet for bruk under kjøring.Derimot er PowerPac svært godt egnet til å erstatte 24 V-batteriene og -dynamoene som brukes under tomgang ved varelevering. Endringene i prosedyrene for ASKO-personellet ville være minimale, og det ville alltid være mulig å gå tilbake til tomgang i tilfelle det oppsto problemer med brenselcellesystemet.Det er betydelig potensiale for utslippsreduksjon med opptil 1400 tonn CO₂ i året, som tilsvarer ca. 800 gjennomsnittlige biler på norske veier