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  3. Exploitation

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- [Voiceover] Let's see briefly the types of geothermal exploitation that we have had in the past because we need to understand that to be able to see what we can do with the results of that, we had available in the oil industry. The very first type of exploitation is usually the direct use, and in this case, we have the direct heating, that we can see in the, applied in Iceland and many other countries, where they use for the AC, singular applications or domestic uses also, the hot water. But we have another use that has been widespread too, and this is the heat pump. In this case, instead of using the air and the heat exchange here for air conditioning and heating, then we use the materials of the air which have a lot of advantages for that, in terms of the stability of the temperature and so on. However, we are not going to touch that because that's relatively on a shallower depth. On the other hand, for the traditional electrical energy production, you once had the flash steam power systems. Most of the volcanic hydrothermal systems around the world are using flash steam power. For the very hot fluids that are usually liquid at the pressure and temperature dip in the air, are extracted and then to the production well, the production well is where it circulates through the pipe, pressures are lowered, and then steam is generated, and then we have to separate the steam from the brine, and the steam is then used to generate electrical energy in the turbines. Then the colder water together with the brine that was separated can be re-injected back into the system. So this was the very first way that we did traditional geothermal resources. But we also have systems that, what we have is dry steam. The pressure and temperature that happens in the interior of the reservoir, is the most, is adequate to produce the steam instead of liquid water. In that case, you only have to extract the steam, and direct to use to move the turbines, and then reject the cool water. The system that is probably more interesting for us is the binary power system, because these are the system that can be used for temperatures lower than 150 Celcius degrees. In this case, the temperature of the water that is extracted in the pressure, the water that is extracted from the reservoir, is not at a point for a flash steam power system, so what we do is to get a second fluid, usually organic fluid, that can circulate through a heat exchanger, where the hot water exchanges heat with the fluid. This fluid obviously has to have a boiling temperature that it is lower than water, so the fluid picks up the heat, and then can move the turbines, and then is recycled again, so this is how the binary power plants work, using the organic ranking power systems. In sense that the binary power or the Rankine cycle, the secondary fluids that we can use, or examples of the secondary fluids that we can use are butane, isobutane, freon, ammonia, and in this case, the cycle is called the Kalina Cycle, carbon dioxide, and so on. But one thing that it is important to notice here is that the choice of the secondary gas depends on the inlet temperature and the inlet pressure. Different gases have optimum pressures and temperatures produce a net power output. In other words, we have to consider those parameters in order to select the gas. Obviously the price is also another parameter. The last system that we need to see here for produce electrical energy the traditional ways is system that use a combination of a steam power and binary system. The reason why this is have been developed is because in beginning of the thermal energy expoitation around the world, flash steam power units were the ones that were in style, and the waste water that was generated during the process usually had still a very high temperature. We didn't take advantage of that energy, so often that we had to reject or discard the water, even at a high temperature. So later on, we had the development of the flash-binary system and then the remaining water from the primary power plant, which is the flash steam system is used to generate electricity with a binary cycling. Here we see, for example, plant that was recently installed in the Berlin Geothermal Field in El Salvador, that it is using binary power system as a second way to generate energy.