The design of Smart Energy Systems for 100% renewable energy and transport solutions B.V. Mathiesen A* , H. Lund B , D. Connolly A , P. A. Østergaard B and B. Möller B A Department of Development and Planning, Aalborg University, A.C. Meyers Vænge 15, DK-2450 Copenhagen SV, Denmark B Department of Development and Planning, Aalborg University, Vestre Havnepromenade 9, DK-9000 Aalborg, Denmark ABSTRACT In this paper we launch the design of Smart Energy Systems through the 100% renewable energy system analyses and research behind the CEESA research project. The transition from fossil fuels towards the integration of more and more renewable energy requires rethinking and redesign of the energy system. Traditionally a lot of focus internationally is put on the electricity sector to solve the integration puzzle focusing on electricity storage technologies e.g. batteries, hydrogen storage and on (electricity) smart grids. In Smart Energy Systems the focus is integration of the electricity, heating and transport sectors, and on using the flexibility in demands and various short term and longer term storage in the different sectors. Such a redesign also entails that the Smart Energy System is comprised of a number of smart grid infrastructures for different sectors in the energy system, i.e. the electricity grids, district heating (cooling) grids, gas grids and fuel infrastructure. KEYWORDS Smart energy systems; renewable energy systems; wind power; biomass; smart grids; district heating; combined heat and power; synthetic transport fuels INTRODUCTION Currently most energy systems are predominantly based on fossil fuels. More and more focus is being placed on energy savings, renewable energy and handling intermittent resources as the shares of fluctuating resources increase. In the current fossil based system, the flexibility is based on the fuels provided for power plants, boilers and vehicles in liquid, gas, and solid form. Current systems have built up the infrastructure and storage facilities that can provide for the demands by means of transporting fossil fuels over large distances in ships and gas pipelines on the global level and providing national or regional energy infrastructure, gas and oil storage facilities and electricity production. Hence a global system is built up based on the easy storage and density of fossil fuels that can flexibly provide for the demands at the right time and place. While this is the case now, the challenge is how such flexibility and timely energy supply can be provided with more and more renewable energy? * Corresponding author. Tel.: +45 9940 7218; E-mail addresses: bvm@plan.aau.dk (B.V. Mathiesen), lund@plan.aau.dk (H. Lund), david@plan.aau.dk (D. Connolly), poul@plan.aau.dk (P.A. Østergaard), bernd@plan.aau.dk (B. Müller)