  Nowadays, the network and the Internet applications have gained a substantial
importance in the digital world, due to the great impact which it provides for
health and community services. Among the most important services that have been
provided are smart devices and vital factor measurement devices for patients,
whether in a hospital or outside the hospital. Furthermore, sensors that
collect medical data or measurements of temperature and humidity, in various
critical environments. The proper types of network that may be used in such
difficult environment are Wireless Sensor Networks, that used to sense and
process data. Additionally, the Wireless Sensor Networks have been used in the
environment of Internet of Things and smart cities in the general services and
health fields. All these reasons have made researchers focus on Wireless Sensor
Networks and addressing the challenges that face them. The most important
challenge facing this type of network is energy consumption and increase
battery life. This paper discusses the methodologies used in energy
conservation in Wireless Sensor Networks, such as data reduction technology,
shortest path selection and artificial intelligence algorithms used in smart
routing and energy saving. Besides, we have introduced comparisons between the
standard algorithms which are suggested by the researchers, to make a clear
picture of the energy consumption problem and propose some effective solutions
in Wireless Sensor Networks field.
