*2.4. Integration of RES into Hybrid Micro-Grid Systems*

A massive rollout of DERs, together with their real integration in the micro-grid management, is an expected requirement in achieving a real impact on technology. The cost of energy will be a critical factor for driving investments in renewable and alternative energy technologies, and a stable investment climate will be required to exploit new hydrocarbon reserves and develop alternative and renewable energy resources.

A successful hybrid micro-grid deployment depends on a fully integrated system. The integration of RES in hybrid micro-grid systems has become increasingly attractive, mainly because of the minimal operating and maintenance costs. The cost of PV systems and WTs has dramatically declined in the last few years. PV and WT systems also become more efficient due to advancing technologies and communication systems. The hybrid micro-grids combine the benefits of RES with the advantages of conventional power generation, delivering lower, long-term operating costs of ownership.

Three models have been proposed in relation to the energy prosumers that are integrated into the micro-grids: Peer-to-peer, prosumer-to-grid, and prosumer community groups [36]. The first model supports the ability of electricity producers and consumers to directly buy and sell electricity, while the next two methods are close to the centralized grid model concepts and architecture.

Each component of a hybrid micro-grid brings advantages that strengthen the entire system, but energy storage systems are a key enabler, contributing to power stability and energy time-shifting. The deployment of long-term ESS can have an important effect on the optimal operation of micro-grids. In addition to balancing the demand-supply when power shortage or surplus are encountered, ESS can be used to maintain dispatchable DG units operating at their maximum efficiency and can prevent or reduce the use of expensive energy sources during peak hours. More details on ESS will be presented in the next section.
