Geothermal Energy Renewable Resources

Introduction to Geothermal Energy OjV26Q OjV26Q Watch this short video for an overview of how geothermal energy is harnessed.

Introduction From the surface down through the crust, the normal temperature gradient - the increase of temperature with the increase of depth - in the Earth's crust is 17 °C - 30 °C per kilometer of depth

Temperature results like this would definitely encourage the drilling of a larger, deeper well to try to find a hydrothermal reservoir.

Australia and Geothermal Australia has extensive hot granites and suitable geological formations that can be used for heating, cooling and to generate electricity. Geothermal energy directly under Perth is already being used to heat some of Perth’s swimming pools, such as Challenge Stadium, Christchurch Grammar School, Manjimup and Fremantle. In the Cooper Basin in South Australia, Geodynamics Australia is demonstrating the use of deeper ‘hot rocks’ 3–5 km under ground. The rock is fractured hydraulically and water is pumped down and circulated repeatedly, transferring heat to the surface with each circulation to generate electricity.

How does geothermal energy work? Dependent on four things: 1.A large heat source geothermal heat is produced from radioactive decay and from heat of earth’s core 2.A reservoir to contain the heat Reservoirs are permeable, hot rocks that when surrounded by impermeable rock layers (the barrier) act as heat-storage containers. Geothermal reservoirs can be structurally similar to the reservoirs of oil and gas reserves 3.A barrier to lock it on Impermeable cap rock 4.A fluid to carry and transfer the heat Injection of water Using existing water that is naturally heated

Hot Rocks In some places, the rocks are hot, but no hot water or steam rises to the surface. In this situation, deep wells can be drilled down to the hot rocks and cold water pumped down The water runs through fractures in the rocks and is heated up It returns to the surface as hot water and steam, where its energy can be used to drive turbines and electricity generators

How energy is harnessed Hot water and steam from deep underground can be piped up through underground wells and used to generate electricity in a power plant. Three different types of geothermal power plants exist: – Dry steam plants. – Flash steam plants. – Binary cycle plants.

Dry steam plants Hot steam is piped directly from geothermal reservoirs into generators in the power plant. The steam spins turbines, which generate electricity.

Flash steam plants Water that's between 300 and 700 degrees Fahrenheit (148 and 371 degrees Celsius) is brought up through a well. Some of the water turns to steam, which drives the turbines. When the steam cools it condenses back into water and is returned to the ground.

Binary cycle plants Moderately hot geothermal water is passed through a heat exchanger, where its heat is transferred to a liquid (such as isobutene) that boils at a lower temperature than water. When that fluid is heated it turns to steam, which spins the turbines.

Advantages of geothermal energy Clean and efficient energy source – do not burn fuel to generate energy so emission levels low/non-existent Water used in this processed is returned and replenished by rainfall Vast amount of heat in the earth that can be tapped Geothermal fields produce 1/6 of CO2 that a clean natural-gas fueled power plant produces Geothermal energy always available Inexpensive – savings from direct use can be as much as 80% over fossil fuels

Disadvantages of geothermal energy Release of hydrogen sulphide into atmosphere Concerns over disposal of geothermal fluids – may contain low levels of toxic materials In the future, specific locations may cool down, minimising reach for geothermal energy

Pros and Cons More detailed pros and cons of geothermal energy can be found at: energy-pros-and-cons/ energy-pros-and-cons/

Geothermal induced earthquakes Read this article about how earthquakes have been induced by geothermal activity wiss-geothermal-power-earthquakes-basel wiss-geothermal-power-earthquakes-basel Consider the cons of this activity and how you could incorporate it into an exam question discussing the pros and cons of geothermal energy