Smart Energy Systems for coherent 100% renewable energy and transport solutions B.V. Mathiesen a,⇑ , H. Lund b , D. Connolly a , H. Wenzel c , P.A. Østergaard b , B. Möller d , S. Nielsen b , I. Ridjan a , P. Karnøe a , K. Sperling b , F.K. Hvelplund 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 c Department of Chemical Engineering, Biotechnology and Environmental Technology, University of Southern Denmark, Denmark d Department Energy and Environmental Management, University of Flensburg, Munketoft 3b, D-24937 Flensburg, Germany highlights  Integrating smart electricity, smart thermal and smart gas grids to enable 100% RE.  Cost and fuel synergies across electricity, heating, and transport can be exploited.  Focusing only on a smart electricity grid reduces the potential for fluctuating RE.  Smart Energy System design can ensure biomass use is limited to a sustainable level.  Smart Energy Systems can pave the way for bioenergy-free 100% RES incl. transport. article info Article history: Received 20 August 2014 Received in revised form 19 January 2015 Accepted 19 January 2015 Keywords: Smart Energy Systems 100% Renewable energy systems Energy storage Smart grids Thermal grids Gas grids abstract The hypothesis of this paper is that in order to identify least cost solutions of the integration of fluctuat- ing renewable energy sources into current or future 100% renewable energy supplies one has to take a Smart Energy Systems approach. This paper outline why and how to do so. Traditionally, significant focus is put on the electricity sector alone to solve the renewable energy integration puzzle. Smart grid research traditionally focuses on ICT, smart meters, electricity storage technologies, and local (electric) smart grids. In contrast, the Smart Energy System focuses on merging the electricity, heating and transport sec- tors, in combination with various intra-hour, hourly, daily, seasonal and biannual storage options, to cre- ate the flexibility necessary to integrate large penetrations of fluctuating renewable energy. However, in this paper we present the development and design of coherent Smart Energy Systems as an integrated part of achieving future 100% renewable energy and transport solutions. The transition from fossil fuels towards the integration of more and more renewable energy requires rethinking and redesigning the energy system both on the generation and consumption side. To enable this, the Smart Energy System must have a number of appropriate infrastructures for the different sectors of the energy system, which are smart electricity grids, smart thermal grids (district heating and cooling), smart gas grids and other fuel infrastructures. It enables fluctuating renewable energy (such as wind, solar, wave power and low value heat sources) to utilise new sources of flexibility such as solid, gaseous, and liquid fuel storage, thermal storage and heat pumps and battery electric vehicles. Smart Energy Systems also enable a more sustainable and feasible use of bioenergy than the current types allow. It can potentially pave the way to a bioenergy-free 100% renewable energy and transport system. Ó 2015 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apenergy.2015.01.075 0306-2619/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ 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), henrik.wenzel@kbm.sdu.dk (H. Wenzel), poul@plan. aau.dk (P.A. Østergaard), bernd@plan.aau.dk (B. Möller), steffenn@plan.aau.dk (S. Nielsen), iva@plan.aau.dk (I. Ridjan), karnoe@plan.aau.dk (P. Karnøe), karl@plan.aau.dk (K. Sperling), hvelplund@plan.aau.dk (F.K. Hvelplund). Applied Energy 145 (2015) 139–154 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy