In line with the efforts to achieve net-zero carbon emissions, the energy system is experiencing significant paradigm shifts, both on the supply and the demand side. On the supply side, the capacity of variable renewable energy (RE) is markedly growing at the expense of conventional fossil power generation plants. On the demand side, there has been an increasing thrust for electrification of sectors, in particular heating and mobility. Additionally, other sector coupling options, such as the use of green hydrogen in hard-to-electrify sectors are being developed. This thesis aims at analyzing the potential of flexibility and sector coupling to support the integration of RE and low carbon technologies as part of the energy transition in Switzerland. Various models and methodologies are developed for this purpose: i) In the first study (Chapter 2), RE technologies are combined with different energy storage (ES) technologies to form hybrid systems supplying firm electricity under various supply strategies at three different scales of deployment. ii) The second study (Chapter 3) focuses on distribution grid reinforcement needs to facilitate integration of rooftop PV on the supply side and electrification of heating and mobility on the demand side. iii) The third study (Chapter 4) identifies hotspots for green hydrogen and power-to-methane plants deployment across Switzerland. iv) Finally, in the last study (Chapter 5), the work on green hydrogen deployment is expanded to also assess macroeconomic impacts of a new green hydrogen sector on the Swiss economy. Overall, the studies carried out in this thesis lead to the following key results of relevance for decision-makers: i) The first study presents a new model on the operation of renewable hybrid systems to supply firm electricity across three different scales of deployment - residential, utility, and bulk level, thereby providing results on the levelized cost of hybrid systems (LCOHS) across different cantons in Switzerland. This model is then used to point to the optimal combination of renewable and storage technologies depending on the scale and supply mode. ii) The second study estimates the cost required to reinforce the distribution grid under different penetration scenarios of rooftop solar PV, heat pumps and electric vehicles charging, all modelled at high spatial resolution. This type of information is highly valuable for DSOs to plan the investments for future grid development. Additionally, the study highlights the role of batteries in deferring distribution grid upgrades, besides offering additional services (benefit stacking). iii) The third study presents hotspots for deployment of green hydrogen and power-to-methane plants in Switzerland by mapping different supply and demand sources at a high spatial resolution. This study can provide guidance to project developers and investors for profitable deployment of green hydrogen and methane plants across Switzerland. The study also showcases a roadmap for green hydrogen deployment from now until 2050, considering the estimated reduction in technology costs. iv) The fourth study provides insights into the macroeconomic impacts of a green hydrogen industry from both construction and operation phases, at a country level. Using input-output modelling, the study provides a transparent and replicable approach for assessing the direct and indirect impacts of this emerging industry.