Wireless Sensor Networks (W) have drawn considerable attention in recent years due to their potential applications such as monitoring active volcano eruption, monitoring sensitive areas of military battle field, monitoring the stability of dams, bridges and roads and etc. W are Ad hoc wireless networks which consist of a large number of densely deployed miniature sensor nodes in the region of interest to monitor and capture physical environmental. As the sensors? placement can be random, such nodes can be placed in dangerous or inaccessible places. Since the sensors are battery powered devices, energy efficiency is considered as one of the main factors in designing routing protocols in W. Power failure of each node affects not only the node itself and its ability to forward packets but also other nodes as well as the overall network lifetime. The lifetime of a sensor network can be increased significantly if the operating system, MAC layer and network layer protocols and even higher layers are designed to be energy aware. The subject of routing protocols in W is very challenging due to their significant effect on the energy consumptions of nodes.The routing protocols can be divided into four categories including data–centric routing protocols, hierarchical -based routing protocols, location-based routing protocols and quality of service (QoS) routing protocols. In this way clustering techniques have been used in the Hierarchical -based protocols. Previous studies reveal that the clustering techniques can improve the performances of such routing protocols. This is because in comparison with single level communicational schemes, the cluster based hierarchical routing protocols can effectively improve the scalability of the whole network lifetimes and energy efficiency. In this thesis two new energy aware clustering based routing algorithms are proposed where the first proposed algorithms is suitable for large scale network and the seconds proposed algorithm is suitable for small scale network. The simulation results from proposed algorithms are compared to the known algorithms such as BMR, SWDN EELBCRP, DECSA and HEED. In comparison with such algorithms, the proposed algorithms enhance the network lifetime significantly through uniformly distributed energy consumption among the nodes. Keywords : Sensor network; Energy aware routing protocols; Clustering