Introduction: Renewable energy sources offer the opportunity to reduce fossil fuel consumption. Energy derived from solar, wind, hydroelectric, geothermal, and biomass sources are considered as renewables. As a renewable energy source, geothermal fluids extracted from geothermal wells can be used in various processes such as power generation, area and district heating applications. The Organic Rankine Cycle (ORC) is a power system that can be operated at low and medium temperature level heat sources and can also be utilized with geothermal source. The ORC has the same components as those of the conventional Rankine cycle and it differs from the conventional cycle by the working fluid. An organic fluid is used in the system, and the simple cycle mainly consists of a pump, an evaporator, a condenser and a turbine-generator group. The heat energy obtained from the geothermal source absorbed by the working fluid is first converted into mechanical energy and then to electrical energy. Hydrogen is an effective energy carrier that can also be obtained from the renewable energy sources such as geothermal, solar or biomass-derived synthesis gases, serves an alternative to fossil fuels. Thus, the hydrogen production technologies are researched by many scientists because of its high energy intensity and clean use. Objective: The investigation of a biomass-derived hydrogen production process integrated with a geothermal assisted organic Rankine power cycle was aimed. Scope: A hybrid system was designed for hydrogen production and a power generation system using renewable energy. The required energy for hydrogen production was provided by modeling the integrated power cycle. For this purpose, Aspen Hysys software was used to simulate the system. Limitations: Geothermal energy was used to provide the energy required by the hydrogen production process. The supply of the energy demand depends on the amount of energy transferred from the heat source to the organic Rankine power cycle. In addition, the operating conditions and the net power output of the organic Rankine cycle is limited by the mass flow rate and the properties of the selected working fluid. Method: Hydrogen production technologies are generally classified under three main processes. These are thermal, electrolytic and photolytic processes. Thermal processes can also be divided into four groups that are the steam-methane reforming of natural gas, reforming of bio-based liquids, coal-biomass gasification and thermochemical production. Furthermore, the hydrogen production from biomass-derived synthesis gas consists of four main steps that synthesis gas production, gas cleaning processes, hydrogen enrichment of the gas and purification of the hydrogen. The required energy for hydrogen production process can be obtained by using a geothermal based organic Rankine power cycle. Geothermal energy, which is a domestic, cheap and environmentally friendly renewable source, is a sustainable and important choice for energy systems. In this study, the required energy for hydrogen production that is provided by an ORC system utilizing a geothermal source was investigated by using the simulation and modeling methods. Results: The investigation of a hydrogen production system integrated with geothermal-assisted Organic Rankine Cycle (ORC) was performed. The R134a was used in the ORC as the working fluid. The energy requirements of power consuming equipment were determined, and the operating conditions of the ORC were obtained. According to the simulation results, as the mass flow rate of the synthesis gas increased, the efficiency of the hydrogen production system enhanced. On the other hand, this led to an increase in the electrical energy consumption of the hybrid process. Conclusion: Hydrogen gas production systems based on renewable energy sources are among the environmentally friendly technologies and clean energy systems. Thus, the development of renewable hybrid power systems to supply the energy requirements of the hydrogen production process is important research area for the sustainable hydrogen technologies. In this study, the investigation of the proposed hybrid system was successfully performed by using Aspen simulation software, and the results were obtained. The methodology and results of this paper can be beneficial for designing similar systems.
Anahtar Kelimeler: Renewable Energy, Hydrogen Production, Organic Rankine Cycle, Simulation
|
