京都大学 / 新制・課程博士 / 博士(工学) / 甲第23578号 / 工博第4933号 / 新制||工||1770(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 江口 浩一, 教授 陰山 洋, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20708号 / 工博第4405号 / 新制||工||1684(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 江口 浩一, 教授 安部 武志, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Hydrogen can be produced via water electrolysis, a process powered by electricity, and is often called green hydrogen if the electricity source is renewable. The purpose of this thesis is to investigate the levelised cost of hydrogen, LCOH, from two hypothetical scenarios of green hydrogen production at onshore wind farm sites. The hydrogen is used in steel manufacturing. One scenario is set in Chile, a country with excellent wind conditions, where a large wind farm of around 1 GW supplies both a hydrogen and ammonia production. Ammonia is used as a hydrogen carrier since it is easier to transport, and the ammonia is shipped to Sweden where it is decomposed into hydrogen. The Swedish scenario includes three cases with wind farms of 28.5, 114 and 285 MW (case 1, 2 and 3), where the sites are located close to the steel plant. Both the Chilean and Swedish scenarios consist of a base case and a sensitivity analysis, all simulated in MATLAB. Parameters such as equipment efficiency and cost, levelised cost of wind energy, shipping and transportation costs, electricity price and electrolyser size were analysed to see how they affect the LCOH.  The results showed that the Chilean case both could meet the hydrogen demand of a commercial steel plant and has a lower LCOH than most Swedish scenarios. The LCOH in the base case was 2.17 €/kg H2 for the Chilean case and 6.71, 6.29 and 5.14 €/kg H2, respectively, for case 1, 2 and 3. The sensitivity analysis showed that case 3 had a similar or lower LCOH than the Chilean case when it was connected to the grid, and could sell excess wind electricity, or for electrolysers of at least 100 MW. Case 3 could supply the smallest of the suggested steel plant sizes, and it would require an around three times larger wind farm and hydrogen production site to reach the level of the Chilean case. However, the Swedish case could be preferred if other factors, such as security of supply, local connection or the exclusion of fossil fueled transports, are more important than low cost and hydrogen volume.

n a world of unsustainable growth and increasingly catastrophic climate events, the quest for sustainability is open. Electrochemical ammonia synthesis (EAS) represents an eco-friendly means for green ammonia production. This technology mainly requires electricity, which can be harvested from renewable sources, as its energy input, and can be employed in a decentralized fashion, cutting down transport emissions and complexity. Green ammonia could help humanity as a hydrogen carrier, energy storage and sustainable fertilizer. However, sustainable alternatives are still far from achieving the production rates of the current adopted technology, namely the Haber-Bosch process. The present experimental-based investigation explores the feasibility of implementing a new membrane-less porous walls approach to electrochemical ammonia synthesis. This research mainly revolves around two experimental phases: the first considering a single compartment (SC) cell electrochemical set-up, and the second a membrane-less porous walls (PW) cell set-up. The former was used to gain knowledge regarding membrane-less cell behaviour, which then was applied to the latter, whose aim was to achieve ammonia synthesis. It was demonstrated that this approach can achieve high current densities (707.4 mA cm-2) and high ammonia production rate (1727.9 μmol cm-2 h-1) at -3.1V (cell voltage), through catalytic nitrate (𝑁𝑂3−) reduction, on nickel phosphide sheet cathode, in an aqueous sodium hydroxide electrolyte solution. On the contrary, it shows low faradaic efficiency, only 43%. Even if the results were partially validated by literature and contamination tests, isotope labelling experiments need to be conducted for more reliable estimates. These findings add another promising perspective to the field of electrochemical ammonia synthesis. / I en värld av ohållbar tillväxt och alltmer katastrofala klimathändelser är strävan efter hållbarhet öppen. Elektrokemisk ammoniaksyntes (EAS) är en miljövänlig metod för grön ammoniakproduktion. Denna teknik kräver främst el, som kan förses från förnybara källor, för energitillförsel och kan användas på ett decentraliserat sätt, vilket minskar transportutsläppen och komplexiteten. Grön ammoniak kan hjälpa mänskligheten som vätgasbärare, energilagring och hållbart gödningsmedel. Hållbara alternativ är dock fortfarande långt ifrån att uppnå produktionsnivån för nuvarande teknik, nämligen Haber-Bosch-processen. Detta experimentella arbete undersöker möjligheten att implementera en ny strategi för elektrokemisk ammoniaksyntes genom membranfri porösväggar. Denna forskning handlar huvudsakligen om två experimentella faser: den första handlar om enkelfack (SC) cellelektrokemisk uppsättning, och den andra en membranfri porösväggar (PW) celluppsättning. Den förstnämnda användes för att få kunskap om membranfritt cellbeteende, som sedan applicerades på det senare, vars mål var att uppnå ammoniaksyntes. Det har visats att den just nämnda tekniken kan uppnå högströmtätheter (707.4 mA cm-2) och hög ammoniakproduktionshastighet (1727.9 μmol cm-2 h-1) vid -3.1V (cellspänning), genom katalytiskt nitrat (𝑁𝑂3−) reduktion, på nickelfosfidarkatod i en vattenhaltig natriumhydroxidelektrolytlösning. Å andra sidan visar resultaten en låg faradaisk effektivitet, bara 43%. Även om resultaten delvis validerades genom litteratur- och kontamineringstester, måste isotopmärkningsexperiment genomföras för mer pålitliga uppskattningar. Dessa fynd lägger till ytterligare ett lovande perspektiv på området elektrokemisk ammoniaksyntes.