DGs are small scale generation sources which are located as near as possible at center of loads.
Nowadays, these DGs are becoming more prominent in distribution systems due to the incremental
demands of electrical energy and to reduce the power disruption in the power system network.
Fuel cells (FCs) are new types of DGs which have numerous benefits that make them superior
compared to the other types of DGs. This paper presents a deep review of FCs technology,
(definition, structure and theory of work). A general description of FC types is explained,
indicating advantages and disadvantages of each type and pointing out their principal use. Finally,
economics of producing electricity from different types of FCs, wind and solar energy are
examined under different conditions.