# Internet of Things for Modern Energy Systems: State-of-the-Art, Challenges, and Open Issues
## 2 Key Features in the Energy Internet
### Energy Consumers  
Although energy is used in many forms (e.g., thermal, chemical, electrical, etc.), some are well-accepted at the end-use due to easier transmission and conversion [31]. Consumers of energy mostly use an electrical form, as it is easy to use and transfer and related infrastructures are well developed. However, energy consumers act differently based on their needs (i.e., demand level) and their types (e.g., residential, commercial, industrial, etc.). In this regard, some features of the energy consumers that should be considered are as follows:  
\(\bullet\) Controllability of the loads  
Some loads can be curtailed, while others cannot be curtailed or shed. This significantly affects energy management of the system [32; 33] and it has pros and cons either from a system operator's or end-user's perspective. If the system could shed a load whenever it wants, then it may be able to reach its optimum point easier. On the other hand, this facility will cost money for the system, as it may be undesirable from the end-user's viewpoint. In the manner of Smart Grids, Internet of things can be used interchangeably with ICT. Therefore, it is involved in Demand Response (DR) of the smart grid, as it is widely discussed in [34]. On the other hand the energy consumption pattern of a system can be detected by studying the consumers' behavior over time: collecting information via sensors, storing, and analyzing the information by defining a data processing system. Finally, a logical decision can be made to shed or curtail loads regarding decision makers' benefit and/or consumers' preferences [35]. Other applications, which can be applied in energy systems in respect of load controlling, is related to time-shiftable loads and thermostatically controllable loads [36; 37; 38]. In this regard, system operators control shiftable loads by using incentive-based offers.  
\(\bullet\) Mobility of the loads  
Some loads have the ability to move from one place to another. This brings both challenges and opportunities to energy systems. The main challenge lies in efficient scheduling of these loads over different time scales and locations. On the other hand, the main opportunity relates to the mobility and load shaping capability. As an example, optimal charging/discharging scheduling of Electric Vehicles (EVs) can help smoothing the system load profile [39]. EVs bring a new aspect of EMS in smart grids, as real-time machine to machine communications are needed in order to exchange information among EVs and local or central controllers [40].  
\(\bullet\) Load type and nature  
According to loads nature and function, loads can be categorized and modeled in different types, and, subsequently, their behavior can be simulated differently [41; 42]. Based on that, systems behavior can be studied in different ways. As an example, when nonlinear loads are connected to the grid, they draw harmonic currents, which cause voltage harmonics and losses over the system [43].  
* Effect of loads on global emission  
Without any doubt, global warming affects industries. This feature really changes the future of loads. Loads that produce greenhouse gases will be less used in near future; instead, there will be a tremendous increase in the number of loads that are green. This means that people wish to use electric vehicles instead of traditional cars, which results in both a change and opportunities in energy consumption [44].