Full energy sector transition towards 100% renewable energy supply: Integrating power, heat, transport and industry sectors including desalination

•Sector coupling leads to lower cost of energy supply in a RE-based system.•Power sector becomes the backbone of the entire energy system.•Integration impact depends on demand profiles, flexibility and storage cost.•Electrolysers are an important source of flexibility in an integrated system.•All sector defossilisation is achieved even for severe conditions as of Kazakhstan. Transition towards long-term sustainable energy systems is one of the biggest challenges faced by the global society. By 2050, not only greenhouse gas emissions have to be eliminated in all energy sectors: power, heat, transport and industry but also these sectors should be closely coupled allowing maximum synergy effects and efficiency. A tool allowing modelling of complex energy system transition for power, heat, transport and industry sectors, responsible for over 75% of the CO2eq emissions, in full hourly resolution, is presented in this research and tested for the case of Kazakhstan. The results show that transition towards a 100% sustainable and renewable energy based system by 2050 is possible even for the case of severe climate conditions and an energy intensive industry, observed in Kazakhstan. The power sector becomes backbone of the entire energy system, due to more intense electrification induced sector coupling. The results show that electrification and integration of sectors enables additional flexibility, leading to more efficient systems and lower energy supply cost, even though integration effect varies from sector to sector. The levelised cost of electricity can be reduced from 62 €/MWh in 2015 to 46 €/MWh in 2050 in a fully integrated system, while the cost of heat stays on a comparable level within the range of 30–35 €/MWh, leading to an energy system cost on a level of 40–45 €/MWh. Transition towards 100% renewable energy supply shrinks CO2eq emissions from these sectors to zero in 2050 with 90% of the reduction achieved by 2040.