| Abstract | This thesis is intended at answering the question: What is the feasibility of using synthetic
fuels for reaching a 100% renewable transport sector? To answer this question an energy
system analysis was carried out and two pathways for producing synthetic fuels were created
with a specific focus on solid oxide electrolyser cells (SOEC) which are combined with the
recycling of CO2. The first pathway entails co-electrolysis of steam and CO2 and the second
one includes hydrogenation of CO2. These scenarios have been compared in terms of primary
energy supply, biomass consumption, flexibility of system and socio-economic costs with two
pathways that have direct usage of biomass in the production process of liquid fuels -
hydrogenation of biomass and conventional biodiesel pathway. The scenarios provide all
liquid fuels that cannot be replaced by direct electrification which has the first priority.
The reason for this analysis lies in the fact that at present, the transport sector is the only
sector in which there have been no significant renewable energy penetrations and it is heavily
dependent on oil with rapid growth in the last decades. Moreover, it is challenging to obviate
the oil dependence due to the wide variety of modes and needs in the sector. Nowadays,
biofuels are proposed as one of the main options for replacing fossil fuels in the transport
sector, along with electricity. The main reasons for avoiding the direct usage of biomass in the
transport sector, i.e. producing biomass derived fuels, are land use shortage, limited biomass
availability, interference with food supplies, and other impacts on environment and biosphere.
Hence, it is essential to do a detailed analysis of the transport sector in order to match the
demand and to meet the criteria of a 100% renewable energy system in 2050. The analysis
was carried out for Danish system, because the most developed 100% renewable energy
system is available from the CEESA project, which includes a wide variety of transport and
other energy system measures.
The analysis showed that the synthetic fuel scenarios increase the system flexibility and this is
essential for the conversion of the energy system into a 100% renewable system. The costs of
synthetic fuel scenarios are more expensive, but biomass savings associated with this make
the additional costs worthwhile due to the scarcity of biomass for the energy system. With
feasible technological development and mass production of the Solid Oxide Electrolyser
Cells, synthetic fuels could be competitive and have market advantage over biomass derived
fuels based on their supply related issues, land use shortage, limited biomass availability, etc. |
| Abstract (croatian) | Svrha ovog rada je pružiti odgovor na pitanje: Kolika je opravdanost korištenja sintetičkih goriva u svrhu postizanja 100% obnovljivog prometnog sektora? Stoga je provedena analiza energetskog sustava te su osmišljena dva scenarija za proizvodnju sintetičkih goriva, scenarij koji obuhvaća elektrolizu vode i CO2 (eng. co-electrolysis) i hidrogenizacija CO2 (eng. CO2 hydrogenation), s posebnim fokusom na elektrolizatore s elektrolitom od krutih oksida (SOEC) u kombinaciji s recikliranje CO2. Usporedba, s dva scenarija sa izravnom upotrebom biomase za proizvodnju goriva - hidrogenizacija biomase (eng. hydrogenation of biomass) i scenarij s konvencionalno proizvedenim biodizelom, je provedena u pogledu opskrbe primarnom energijom, potrošnje biomase, fleksibilnosti sustava te društveno-ekonomskih troškova. Scenariji osiguravaju potrebe za tekućim gorivima koja ne mogu biti zamijenjena prvim prioritetom - izravnom elektrifikacijom sektora. Razlog analize jest činjenica da je prometni sektor trenutno jedini sektor u kojem nije bilo značajnih penetracija obnovljivih izvora energije, u potpunosti je ovisan o nafti, te ima brzi porast potražnje u posljednih nekoliko desetljeća. \Nadalje, veliki je izazov otkloniti ovisnost o nafti zbog različitih oblika i potreba prometnog sektora. Biogoriva, odmah nakon elektrifikacije, predstavljaju glavnu zamjenu tekućim fosilnim gorivima u sektoru. Glavni razlozi za izbjegavanje izravne uporabe biomase u sektoru prometa, tj. proizvodnji biogoriva, su problemi vezani za nedostatak dostupnog zemljišta, ograničenost resursa, utjecaj na opskrbu hranom te drugi utjecaji na okoliš i biosferu. Stoga je neophodno napraviti detaljnu analizu prometnog sektora kako bi se namirile potrebe te zadovoljili kriteriji 100% obnovljivog energetskog sustava u 2050-toj. Analiziran je danski sustav, najrazvijeniji 100% obnovljivi energetski sustav dostupan u CEESA projektu, koji uključuje široku raznolikost mjera u prometnom kao i ostalim energetskim sustavima. Analiza je pokazala da scenariji za proizvodnju sintetičkih goriva potvrđuju poboljšanja fleksibilnosti sustava što je ključno za pretvorbu energetskog sustava u 100% obnovljivi sustav. Scenariji za proizvodnju sintetičkih goriva su skuplji, no dodatni troškovi se isplate zbog ušteda na biomasi, čija je količina ograničena u energetskom sustavu. S mogućim tehnološkim razvojem i masovnom proizvodnjom SOEC-a, sintetička goriva mogla bi postati konkurentna i imati tržišnu prednost u odnosu na biogoriva, s obzirom na sigurnost opskrbe, nedostatka zemljišta, ograničenost resursa itd. |
