Presentation Information
[O12-P22]Development of model to promote the adoption of Binary Power Generation
*Naotoshi Umezu1, *Chikara Ito1 (1. Miyagi Prefecture Furukawa Reimei high school)
Keywords:
Geothermal energy,Geothermal power generation,Binary power generation
Japan is a “geothermal powerhouse” boasting the world's third-largest geothermal resources, with a total capacity equivalent to approximately 23.47 million kW.
However, the output of geothermal power plants currently in operation in Japan is only about 520,000 kW—a mere 2.2% of the total geothermal resources—meaning that despite abundant resources, they are not being fully utilized. There are many reasons why geothermal power generation has not become widespread, including development costs, site conditions, and other factors. We have focused on one of these factors: public awareness of the advantages and disadvantages of geothermal power generation.
There are four main methods of geothermal power generation, and among them, the flash method is widely used. On the other hand, the relatively new binary method, despite being capable of utilizing low-temperature geothermal resources, is not widely known.
Therefore, this study focuses on these two methods with the aim of raising public awareness of their respective mechanisms through models.
We are currently constructing a binary power generation model in preparation for a presentation to students.
Binary power generation is a method of generating electricity by heating a solvent to vaporize it, using that steam to turn a turbine, cooling it in a cooling section to liquefy it, and then returning it to the heating section. Binary power generation has the advantage of being able to generate electricity even at low temperatures compared to other geothermal power generation methods. Hot spring sources vary in temperature, and it is not uncommon for the source temperature to be 80 degrees Celsius.
At this temperature, other geothermal power generation methods cannot generate electricity; however, since the water is too hot for humans to enter, an air-cooled method that uses the outside air temperature is employed, resulting in the waste of thermal energy during the cooling process.
Therefore, by using binary power generation, it becomes possible to generate electricity while cooling the hot spring water. Since the model currently under construction is intended for future presentations to students, I considered whether the working fluid for the binary power generation system could be made safer and opted to use an alternative refrigerant with relatively low toxicity. However, due to its extremely low boiling point, heating occurred in unexpected locations, preventing power generation.
While measuring the flow rate using ethanol, I also attempted to verify turbine rotation and power generation, but neither the turbine rotation nor power generation could be confirmed. Although ethanol movement was confirmed due to heating, it is believed that the ethanol reverted to a liquid state because the turbine and heating section were too far apart, preventing a sufficient flow of gas. Another contributing factor was that the turbine was designed for liquids and could not withstand the heat of the ethanol.
As part of our efforts to raise awareness, we gave a presentation on single-flash power generation to students. During the presentation, we used a relatively simple single-flash power generation model that we had actually built to illustrate the process.
Moving forward, we plan to implement improvements such as bringing the turbine and heating layer closer together and replacing the turbine with a more heat-resistant model. Furthermore, since binary power generation faces the issue of expensive components, we believe that using a non-contact turbine to separate the turbine from the motor will help reduce replacement costs to some extent. Additionally, we aim to eventually use a binary power generation model to demonstrate the concept during Tohoku University’s outreach classes.
However, the output of geothermal power plants currently in operation in Japan is only about 520,000 kW—a mere 2.2% of the total geothermal resources—meaning that despite abundant resources, they are not being fully utilized. There are many reasons why geothermal power generation has not become widespread, including development costs, site conditions, and other factors. We have focused on one of these factors: public awareness of the advantages and disadvantages of geothermal power generation.
There are four main methods of geothermal power generation, and among them, the flash method is widely used. On the other hand, the relatively new binary method, despite being capable of utilizing low-temperature geothermal resources, is not widely known.
Therefore, this study focuses on these two methods with the aim of raising public awareness of their respective mechanisms through models.
We are currently constructing a binary power generation model in preparation for a presentation to students.
Binary power generation is a method of generating electricity by heating a solvent to vaporize it, using that steam to turn a turbine, cooling it in a cooling section to liquefy it, and then returning it to the heating section. Binary power generation has the advantage of being able to generate electricity even at low temperatures compared to other geothermal power generation methods. Hot spring sources vary in temperature, and it is not uncommon for the source temperature to be 80 degrees Celsius.
At this temperature, other geothermal power generation methods cannot generate electricity; however, since the water is too hot for humans to enter, an air-cooled method that uses the outside air temperature is employed, resulting in the waste of thermal energy during the cooling process.
Therefore, by using binary power generation, it becomes possible to generate electricity while cooling the hot spring water. Since the model currently under construction is intended for future presentations to students, I considered whether the working fluid for the binary power generation system could be made safer and opted to use an alternative refrigerant with relatively low toxicity. However, due to its extremely low boiling point, heating occurred in unexpected locations, preventing power generation.
While measuring the flow rate using ethanol, I also attempted to verify turbine rotation and power generation, but neither the turbine rotation nor power generation could be confirmed. Although ethanol movement was confirmed due to heating, it is believed that the ethanol reverted to a liquid state because the turbine and heating section were too far apart, preventing a sufficient flow of gas. Another contributing factor was that the turbine was designed for liquids and could not withstand the heat of the ethanol.
As part of our efforts to raise awareness, we gave a presentation on single-flash power generation to students. During the presentation, we used a relatively simple single-flash power generation model that we had actually built to illustrate the process.
Moving forward, we plan to implement improvements such as bringing the turbine and heating layer closer together and replacing the turbine with a more heat-resistant model. Furthermore, since binary power generation faces the issue of expensive components, we believe that using a non-contact turbine to separate the turbine from the motor will help reduce replacement costs to some extent. Additionally, we aim to eventually use a binary power generation model to demonstrate the concept during Tohoku University’s outreach classes.