# Future Renewable Energy Communities Based Flexible Power Systems
## 5 Role of Flexible Energy in Renewable Energy Communities  
Energy communities have existed even before the world decided to head towards renewable, sustainable, and decentralized power systems. In remote areas and islands where access to a central grid is not possible, several prosumers joined together and build an energy community to satisfy their electricity need. Currently, achieving the Paris agreement target requires that power systems deal with a larger share of renewables. However, the current power systems are unable to accommodate the high injection of intermittent renewable power into the system. Hence, power systems need to be more flexible and be able to match the high share of intermittent renewable generation with the demand. To this end, energy communities can increase the flexibility of power systems through their energy storage resources and demand response capabilities. They can also produce green energy through their shared resources and contribute to achieving decentralized power systems. In general, energy communities consist of a group of members including consumers, prosumers or even small-scale enterprises who voluntarily join together to follow a specific objective. They also have some community-level energy resources such as PV panel(s), wind turbine(s), and storage system(s). These assets are shared between the members. The community utilizes the shared assets in order to fulfil its objective. The objectives of energy communities can be increasing the self-sufficiency of the members, maximizing the profits of the members by selling energy and flexibility to the upstream grid, or any common goals that lead to the members joining together. However, according to regulations set by European Union Renewable Energy Directive and Internal Electricity Market Directive, energy communities need to \"provide environmental, economic, or social community benefits for its shareholders or members or for the local areas where it operates, rather than financial profits\" [29]. In this way, renewable energy communities not only provide economic benefit for their members, but their renewable and flexible assets also benefit the upstream grid by helping it become more flexible and environmentally friendly. The flexibility potential of energy communities enhances considerably by adding interconnectivity options [29]. Interconnectivity options allow the integration of various types of energy and connect different sectors within an energy community. Integrated systems can help the community to achieve its objective more efficiently. For example, a community may include district thermal networks that circulate hot water or low-pressure steam around the community's members. In this way, along with electricity, heat, cold,  
Figure 9: A smart prosumer in a smart-city. and steam are distributed between the members [30]. District network heat can be fueled by the energy resources within the community such as the excess energy of wind and PV. The industrial process that produces heat, combined heat and power, geothermal, waste-to-energy resources, biofuels, and biomass are the other examples of the resources used for producing heat. On the other hand, lake cooling water is an example of the resource producing cold. An integrated hybrid system is also able to use the flexibility potential of heat pumps and heat storage technologies. The integration of thermal systems with electricity systems increases the energy efficiency of the community [31]. In addition to thermal systems, transportation systems that include a high number of electric vehicles (EV) are another source of flexibility in the community. In this regard, EVs are charged during a time that is in line with the objective of the community. The community's central energy management system plays an important role in integrating different networks and sectors within the community. Figure 10 summarizes the responsibilities of the EMS that aims to operate the energy community with hybrid energy resources.