Geothermal Energy PDF

Artificial Neural Networks - Introduction - Birinderjit Singh Kalyan EEDEPARTMENT OF MECHANICAL ENGG. UNIVERSITY INSTITUTE OF ENGINEERING Assistant Professor CHANDIGARH UNIVERSITY, MOHALI...

Artificial Neural Networks - Introduction - Birinderjit Singh Kalyan EEDEPARTMENT OF MECHANICAL ENGG. UNIVERSITY INSTITUTE OF ENGINEERING Assistant Professor CHANDIGARH UNIVERSITY, MOHALI www.cuchd.in Mechanical Engineering 1 Campus :  Non Conventional Energy Resources MEO-453 Session : Jan-May,2024 Dr. Surender Kumar Assistant Professor Chandigarh University www.cuchd.in Mechanical Engineering Campus :  1.16 Geothermal Energy www.cuchd.in Mechanical Engineering Campus : www.cuchd.in Mechanical Engineering Campus :  Resources of geothermal energy  70% comes from the decay of radioactive nuclei with long half lives that are embedded within the Earth. Geothermal energy comes from heat in the Earth's core which was generated by the radioactive decay of materials when the planet formed. This thermal energy, stored by rocks and fluids at the centre of the Earth, can be used as a renewable energy resource.  Some energy is from residual heat left over from earth’s formation.  The rest of the energy comes from meteorite impacts. www.cuchd.in Mechanical Engineering Campus :  Different Geothermal Energy Sources Hot Water Reservoirs: As the name implies these are reservoirs of hot underground water. There is a large amount of them in the US, but they are more suited for space heating than for electricity production. Natural Stem Reservoirs: In this case a hole dug into the ground can cause steam to come to the surface. Geopressured Reservoirs: In this type of reserve, brine completely saturated with natural gas in stored under pressure from the weight of overlying rock. This type of resource can be used for both heat and for natural gas. www.cuchd.in Mechanical Engineering Campus :  Normal Geothermal Gradient: At any place on the planet, there is a normal temperature gradient of +300C per km dug into the earth. Therefore, if one digs 20,000 feet the temperature will be about 1900C above the surface temperature. This difference will be enough to produce electricity. However, no useful and economical technology has been developed to extracted this large source of energy. Hot Dry Rock: This type of condition exists in 5% of the US. It is similar to Normal Geothermal Gradient, but the gradient is 400C/km dug underground. Molten Magma: No technology exists to tap into the heat reserves stored in magma. The best sources for this in the US are in Alaska and Hawaii. www.cuchd.in Mechanical Engineering Campus : Thermodynamics of geo-thermal energy conversion-electrical conversion Direct Sources function by sending water down a well to be heated by the Earth’s warmth. Then a heat pump is used to take the heat from the underground water to the substance that heats the house. Then after the water it is cooled is injected back into the Earth. www.cuchd.in Mechanical Engineering Campus :  Generation of Electricity is appropriate for sources >150oC Dry Steam Plants: The production of geothermal power using Rising Steam from the Earth is based on harnessing naturally occurring steam from geothermal reservoirs to generate electricity. This process, primarily used in Dry Steam geothermal power plants Working Principle A Dry Steam plant is the simplest type of geothermal power plant, which directly uses geothermal steam to turn a turbine. This plant is feasible in regions with high- temperature geothermal reservoirs (around 150°C or more) that produce natural steam. Here’s how it operates: www.cuchd.in Mechanical Engineering Campus :  Extraction of Steam: High-temperature steam is extracted directly from geothermal wells drilled into underground reservoirs. Steam to Turbine: The extracted steam is routed through pipelines to a turbine. Turbine Rotation: The high-pressure steam flows over the blades of the turbine, causing it to rotate and, in turn, drive an attached generator. Condensation and Reinjection: The steam exits the turbine at lower pressure and is condensed back into water, typically in a cooling system, and is reinjected into the reservoir to sustain the geothermal source. www.cuchd.in Mechanical Engineering Campus : Thermodynamics of Dry Steam Plant : Here’s a breakdown of the thermodynamic steps involved: Isentropic Expansion (Turbine): The high-pressure steam from the reservoir expands isentropically through the turbine (i.e., without heat exchange), converting thermal energy to mechanical work to drive the generator. The steam's enthalpy decreases as it expands, producing work output. Isobaric Cooling (Condenser): The steam leaving the turbine is cooled at constant pressure in a condenser, converting it into liquid water. This phase change releases latent heat into the cooling system. www.cuchd.in Mechanical Engineering Campus : Isentropic Compression (Pump): The condensed water is pumped back into the injection well to maintain pressure in the geothermal reservoir, completing the cycle. 1. The Dry Steam cycle’s efficiency depends on the high temperature and pressure of the steam, as these increase the turbine's output. 2. Since there’s no working fluid change, the cycle is simpler but limited to high-temperature geothermal reservoirs. www.cuchd.in Mechanical Engineering Campus :  Constructional features and associated prime movers Flash Steam Plants: These are the most common plants. These systems pull deep, high pressured hot water that reaches temperatures of 1820C/3600F or more to the surface. This water is transported to low pressure chambers, and the resulting steam drives the turbines. The remaining water and steam are then injected back into the source from which they were taken www.cuchd.in Mechanical Engineering Campus : Binary Cycle Geothermal Power Plant Working Principle Binary Cycle plants are used in low-to-moderate temperature geothermal areas (typically between 85–170°C), where the geothermal fluid alone cannot reach the steam requirements to drive a turbine. Instead, a secondary working fluid with a lower boiling point (like isobutane or pentane) is used to create a closed-loop system. Here’s how a Binary Cycle plant works: Heat Transfer to Working Fluid: Hot geothermal water (or brine) is pumped from the reservoir and flows through a heat exchanger. This brine does not directly contact the turbine but transfers its heat to a secondary working fluid. Vaporization of Working Fluid: The secondary fluid in the heat exchanger absorbs heat from the geothermal brine and vaporizes. This vapor then expands, creating high pressure to drive the turbine. www.cuchd.in Mechanical Engineering Campus : Turbine and Generator: The high-pressure vapor flows into a turbine, causing it to rotate and generate electricity through an attached generator. Condensation and Recirculation: After passing through the turbine, the vapor is cooled in a condenser, converting it back to liquid form. The working fluid is then recirculated to the heat exchanger, repeating the process. www.cuchd.in Mechanical Engineering Campus : Thermodynamics of Binary Cycle Plant The Binary Cycle plant operates based on the Organic Rankine Cycle (ORC), as it uses organic fluids with lower boiling points than water. This system’s thermodynamic steps are as follows: Isobaric Heating (Heat Exchanger): The geothermal brine transfers heat to the organic working fluid at constant pressure, causing it to vaporize. This phase change absorbs heat and converts the fluid to high-energy vapor. Isentropic Expansion (Turbine): The vaporized working fluid expands isentropically through the turbine, converting heat into mechanical work, which drives the generator. The working fluid's enthalpy decreases, releasing energy as it expands. www.cuchd.in Mechanical Engineering Campus :  Isobaric Cooling (Condenser): The expanded vapor is condensed back into liquid in a condenser at constant pressure, allowing the release of latent heat to the environment or a cooling medium. Isentropic Compression (Pump): The condensed working fluid is then pumped back to the heat exchanger, where it is reheated, and the cycle begins anew. The efficiency of the Binary Cycle is enhanced by the lower boiling point and specific heat properties of the organic working fluid, allowing the plant to harness energy from lower- temperature sources. This closed-loop cycle minimizes the release of geothermal fluids into the environment and can operate with a relatively low geothermal brine temperature. www.cuchd.in Mechanical Engineering Campus :  Availability of Geothermal Energy On average, the Earth emits 1/16 W/m2. However, this number can be much higher in areas such as regions near volcanoes, hot springs and fumaroles. As a rough rule, 1 km3 of hot rock cooled by 1000C will yield 30 MW of electricity over thirty years. It is estimated that the world could produce 600,000 EJ over 5 million years. www.cuchd.in Mechanical Engineering Campus : Geothermal production of energy is 3rd highest among renewable energies. It is behind hydro and biomass, but before solar and wind. Iceland is one of the more countries successful in using geothermal energy: -86% of their space heating uses geothermal energy. -16% of their electricity generation uses geothermal energy. www.cuchd.in Mechanical Engineering Campus :  Merits of Geothermal Energy 1.Renewable and Sustainable: Geothermal energy is derived from the Earth's natural heat, which is continually replenished, making it a renewable energy source with a reliable supply. 2.Environmentally Friendly: It emits significantly fewer greenhouse gases compared to fossil fuels, making it a cleaner energy source. 3.Low Operating Costs: Once a geothermal plant is established, the operating costs are relatively low compared to traditional fossil fuel-based power plants. 4.Local Economic Benefits: It can create jobs and stimulate local economies, especially in areas with substantial geothermal resources. www.cuchd.in Mechanical Engineering Campus :  Demerits of Geothermal Energy: 1.High Initial Costs: The cost of drilling and establishing a geothermal plant is high, especially if the site requires deep drilling to access the heat. 2.Location-Specific: Geothermal resources are only available in certain areas, typically near tectonic plate boundaries, which limits widespread adoption. 3.Potential Environmental Impact: Drilling into geothermal reservoirs can release trapped gases and minerals into the atmosphere and water, which may harm the environment if not managed carefully. 4.Earthquake Risk: Geothermal drilling and the process of injecting water into hot rocks can trigger small seismic events. www.cuchd.in Mechanical Engineering Campus :  FAQs What are the financial benefits of solar energy? What are the environmental benefits of solar energy? What is net metering? How does solar impact my property values? www.cuchd.in Mechanical Engineering Campus :