A smart energy system is an energy system architecture that enables a 100% renewable energy supply, without consuming an unsustainable level of bioenergy. The primary sources of energy in the smart energy system are bioenergy and intermittent renewable energy, such as wind, solar, wave, and tidal power. There are a number of key technical issues to overcome when implementing a smart energy system, primarily how to avoid an overdependence on bioenergy and how to accommodate the fluctuations of intermittent renewable energy. To overcome these obstacles, the key principle behind the smart energy system is the integration of the various energy sectors (electricity, heating, cooling, industry, and transport) so that intermittent renewable sources can be accommodated with new sources of flexibility, such as thermal storage, gas ...