# State of the Art of Telecommunication Systems in Isolated and Constrained Areas
## 3 Comparison of the Solutions
### Criteria for Comparing Solutions
#### 3.1.1 The Power Supply of the Telecommunication System and the Autonomy of the System  
The telecommunication system that interests us is evolving in an isolated environment. One of the characteristics of this type of environment is the absence of an electrical network. The telecommunication system includes active structures to supply power for signal transmission, relay, or reception. Therefore, the electrical energy supply is a significant parameter for system characterization, a fortiori in an isolated environment. The use of renewable energies [52], photovoltaic or other, will be a preferred solution in the future. In this sense, the power supply of the telecommunication system is a significant criterion. In Northern Quebec, the energies widely used [53; 54] are propane and diesel generators for electricity and fuel oil for direct heating. However, the energies mentioned above have high and increasing costs such as maintenance and fuel cost, increasing linearly for years, and transportation. The isolated environment [55] is an inaccessible place, and diesel transportation, for example, is costly. If we add these energies' negative ecological impact, the energy supply systems in an isolated environment tend to be replaced with renewable energies. Industrial systems (telecommunication systems) in an isolated environment suffer the same effect. When it is a question of supplying systems that consume little electrical energy, photovoltaic panels (PV) [56] are preferred, as long as the annual sunshine of the isolated environment is sufficient [57]. They also offer great modularity. We can indeed combine several in series to increase the voltage required to supply the loads or in parallel to increase the available current. PV technologies [58] are monocrystalline (16% to 24% efficiency) or polycrystalline (14% to 18% efficiency). If the system is more demanding, power can be supplied by wind turbines, which rated power can reach in the order of MWs. In this specific case, a study of the wind distribution (simulation and measurement campaign with a mast equipped with an anemometer on the site) will have to be carried out to justify the use of a wind turbine. It should be noted that the system should include batteries [59] to store the energy supplied by the wind turbine or PV and then supply loads. If the required electrical power is constant and extensive, hybrid solutions [60] are adopted. For example, they consist of renewable sources with a diesel generator [61], which takes over if required. The diesel generator starts when there is not enough wind in the case of a wind turbine or not enough sun in the case of PV and when the batteries are almost empty. An inverter must be added when the battery or the PV's supply AC loads, as they are primarily connected to a CC bus. The wind turbine usually provides AC used with a battery charger (AC-DC conversion) or a rectifier if needed to supply DC charges. All the energy flux in the hybrid system is managed by a controller that regulates the power flux between AC and DC buses, ensuring a balance between the power produced and consumed, using, as required, the battery storage. Numerous energy solutions for isolated environments [62] have emerged recently. Mobile solutions are available that integrate photovoltaic panels integrated on a structure, with wind turbines deployed during installation on site. The GreenCube solution [63] from the company ATI based in Rimouski, Quebec, is an example of this hybrid system type. The GC6 model can supply up to 6 kW of electrical power, sufficient for a remote telecommunication station. The deployment of these renewable energy solutions on isolated sites can be worth between a few hundred to hundreds of thousands of dollars depending on the solution chosen:  
* PV only,
* Wind turbine(s) alone, or
* Hybrid systems (wind turbine, PV, diesel, and batteries).