The overall objectives of the project are to demonstrate a "SUNSTORE 4" energy concept of a large scale innovative cost efficient, and technical reliable 100% renewable energy supply system for a (Marstal, DK) large scale (district) heating system with yearly heating production of 28,000 MWh - based on 55% solar energy and 45% biomass energy (willow wood chips from energy crops) including a CO2 heat pump and electricity production from biomass energy through an Organic Rankine Cycle (ORC) unit. The plant comprise:15,000 m2 solar system, CHP system with a low emission 4.0 MW wood chips thermal oil boiler and a 750 kWel ORC; 75,000 m3 pit heat storage, 1.5 MW (thermal) CO2 –driven heat pump - supplementing the existing demonstration plant (SUNSTORE 2) including 18,300 m2 solar thermal and 10,340 m3 pilot pit storage.The targets on cost efficiency are for solar thermal to meet the vision of ESTTP with a cost of 3-6 €-cent per kWh, total energy production costs of 78 Euro/MWhthermal and (low) investment costs of 33 Euro/m3 of the pit heat long term storage. Flexibility in energy output has been obtained through including ORC and the heat pump. The capacity of the pit heat storage has been increased through innovative application of the heat pump. Other types of SUNSTORE 4-energy concepts will be developed adapted to the regional conditions of energy loads, energy costs, renewable energy sources etc. in regions of Eastern, Southern, Central and Northern-Western EU. Dissemination activities will be carried out in 10 EU-countries with short term impact with an indicative target of 20 systems in AT-CZ-DK-FR-DE-IT-PL-ES-UK. The medium (2020) and long time impacts are indicative targets of 0.9-1.8 GWth and 5-10 GWth. The SUNSTORE 4-team comprise European leading experts as J.O. Dalenbäck (Chalmers University), D. Mangold/T. Schmidt (Solites), R. Obernosterer-I. Obernberger (BIOS), R. Battisti (Ambiente Italia) and P.A. Sörensen (PlanEnergi)