# Routing with Renewable Energy Management in Wireless Sensor Networks
###### Abstract  
In wireless sensor networks (WSNs), power consumption is an important aspect when designing routing protocols. When compared to other components of a sensor node, the power required by radio transmitters is responsible for most of the consumption. One way to optimize energy consumption is by using energy-aware protocols. Such protocols take into consideration the residual energy information (i.e., remaining battery power) when making decisions, providing energy efficiency through the careful management of energy consumption. In this work, we go further and propose a new routing protocol that uses not only the residual energy information, but also the available renewable energy information from renewable energy sources such as solar cells. We then present the Renewable Energy-Based Routing (REBORN  
low processing and memory requirements, and is extremely self-organizing, since each node only needs local positioning information from its neighbors [12; 13]. However, the optimization of energy resources can significantly impact the routing processes in a WSN. Most proposed energy-aware routing protocols use the residual energy of the sensor nodes to provide routes that minimize the number of hops while trying to avoid sensor nodes with almost depleted batteries [14; 15].  
More recently, solutions based on energy harvesting and renewable energy resources have been proposed. This is an exciting technology for WSNs, since many envisioned scenarios are based on open, outdoor areas in which external energy sources can be found. As shown in [16], sensor nodes can be equipped with devices that can both collect and store energy so it can be used to increase the network lifetime. This energy harvesting can be done, for instance, by using solar cells that are also able to identify the intensity of the available energy, important information that we will explore in our solution.  
Thus, in this work, we are proposing a new and novel routing algorithm, called Renewable Energy-Based Routing (REBORN), that can route the gathered information toward the sink node while also managing the energy consumption of the sensor nodes by using the knowledge of both residual energy and available renewable energy. By combining the residual energy information with the available solar intensity (provided by the solar cells), our proposed solution can make better decisions on whether to send the available information, sending extra data when the energy is abundant while reducing the energy consumption when the batteries are low and/or when the available renewable energy is scarce (i.e., no sunlight availability).  
Our contributions are summarized as follows:  
* We propose a new routing algorithm for WSNs that takes advantage of both the residual battery energy and the available renewable energy to allow energy savings.
* Our proposed algorithm not only generates efficient path routes, but also decides when is the best time for a node to send the data in order to save energy.
* We also propose a new and simplified solar model to be used on the simulation of WSNs with renewable energy.  
This paper is organized as follows. In the next section, we describe the related work. Section 3 describes our proposed REBORN algorithm, which is evaluated in Section 4. Finally, Section 5 presents our conclusions and future directions.