## 3 Transfer and Harvesting Energy Metamaterials
### Transfer Energy Metamaterials  
Metamaterials can be used in energy transfer in a few different ways, and the number of applications is still growing. Their specific parameters and the ability to change them in different applications leads to the fact that these materials are very desired. MM can be used in high-efficiency transmission lines. They can lead to creating high-efficiency power transmission lines. This can be performed by using metamaterials to control the way that electromagnetic waves travel through transmission lines [47]. By controlling the way that waves pass through the lines, it is possible to reduce the amount of energy lost during transmission, which would make the transmission lines more efficient.  
[PERSON] et al. [45] reviewed focuses on the recent advances in MM for simultaneous wireless information and power transmission technology. He introduced the potential technologies and also pointed out wireless transmission technologies, even concluding with perspectives on the rapidly growing transmission technology requirement for 6G.  
Looking for other potential applications of metamaterials in the transfer energy process, the following can be noted: power line conditioners, smart grids, and wireless power transfer [45; 46].  
There are many control system ideas for power line conditioners, such as using AI [48]. Power line conditioners are referred to to improve the quality of the electrical power that is transmitted over power lines. Whereas, metamaterials can be used to create conditioners that are even more efficient by means of their properties, which can improve and optimizethe whole process. Smart grid systems are used to control the flow of electricity through power lines. Now, we are facing a huge transformation of power systems all over the world.  
[PERSON] et al. [49] made a taxonomy of a large number of technologies in smart grids and their applications in scenarios of smart networks, neural networks, blockchain, the industrial Internet of Things, etc. He presented challenges and opportunities for smart grids. The biggest challenge that can be faced is the growth of the massive exposure of algorithms. This is due to the fact that the number of users increases day by day, requiring more data speed and bandwidth to avoid channel propagation delay [49]. Let us not forget that the main factor of smart grids is communication between all of the local energy market participants. It is a part of the Internet of Things world, where metamaterials can be applicated to make more efficient connections for delivering huge masses of important data.  
In terms of wireless communication, we can also find applications of MM in wireless power transfer [46], where they can be used to create them. These systems can transfer energy wirelessly over a distance. By using metamaterials, we can control the way that energy is transferred, and it is possible to create systems that are more efficient than traditional ones. Typically, a wireless power transfer system is a suitable alternative for power transmission, where conventional wired power transfer faces geographical challenges. In a long-range wireless power transmission system, power is transmitted through microwaves, and a highly directive antenna is required for an effective transmission through this system [46].  
[PERSON] et al. [46] presented a circularly polarized microstrip rectangular patch antenna incorporated with a metamaterial slab. Thanks to the application of metamaterial, this antenna can enhance the amount of transferred power to wireless sensors network with less radiation loss and improve other important antenna parameters. For example, it can reduce beam width radiated power.