The increased deployment of renewable energy is driving a transformation of energy systems.1 This is occurring mostly in the electricity sector, where many countries have seen significant growth in deployment driven by the rapid decline in solar photovoltaic (PV) and wind power costs, and several frontrunners are reaching relatively high shares of variable renewable energy (VRE) in their electricity mix.2 However, the vast majority of countries are in the early stages of developing renewable electricity portfolios. In addition, while modern renewables contribute to heating and coolingi and the transport sector, growth has been relatively limited.3 Whatever the rate of renewable energy uptake in various sectors, challenges related to its integration into existing energy systems remain.4
Energy systems integration, as defined here, is the significant elimination of technical, physical, organisational and legal impediments to high penetration of renewable energy (in particular VRE) in energy systems – including in power grids, district thermal systems and transport fuelling systems. Such integration encompasses changes and optimisation in the planning, design and implementation of energy-related supply- and demand-side technologies, infrastructure, markets and regulatory frameworks to facilitate much greater use of renewable energy sources across all end-use sectors while establishing, maintaining or improving sustainable, secure, adequate, reliable and affordable energy services.
i “Heating and cooling” in this chapter refers to thermal applications including climate control/space heating, heat for industrial use, cooking, agricultural drying, etc.i