Earth Sci - Geothermal and Hydroelectric energy

• Geothermal power plants use steam or hot water to generate electricity.
• The potential for hydropower development varies greatly from region to region due to differences in topography, climate, and river flow patterns.
• The rate of change in temperature with depth is called geothermal gradient.
• Friction causes the particles to produce heat.
• The heat of Earth is manifested at the surface as volcanoes, hot springs, and geysers.
• Geothermal heat can be used directly
• Heat for a house is regulated using pipes, heating fluid, and pumps buried underground,
• Shallow magma heats up underground water reservoirs.
• Steam and water from geothermal reservoirs rise through fractures and porous rocks.
• Minimum temperature for an efficient geothermal reservoir is 200 degrees Celsius and must be 3km below the surface.
• The steam is used to run turbines.
• When steam cools and condenses to water, it is returned to wells to be heated again and pumps back out.
• Gravity is essential for hydroelectric energy.
• Dams were built to allow water to move from higher to lower elevations.
• Water flows through tunnels into powerhouses where electricity is generated by turning turbines.
• Rivers that flow downhill have potential energy which can be converted into kinetic energy as they fall over dams.
• A penstock connects the high elevation water to the turbine.
• The higher the dam, the stronger the pressure and more electricity will be generated.
• Depending on the need of electricity, the amount of water entering the penstock is controlled in the intake.
• Excess water flows through a spillway. Particularly used during the rainy season to prevent overflow and flood.
• San Roque Dam in Pangasinan is the largest hydroelectric dam in the PH.
• Dams can alter river ecosystems and displace communities living in that area.
• Run-of-river power systems generate less electricity since they rely more on natural water flow rates. Sometimes it does not use dams or reservoirs.
• Small scale hydropower requires sufficient flows.
• In a small scale hydropower system, the weir diverts the water to pass through the headrace then to a forebay where sediments can settle. The water passes through the penstock to spin the turbine and then it flows back to the stream.
• Small scale hydropower systems causes less environmental damages.
• Dry steam uses steam directly from the geothermal reservoir.
• Flash steam takes high pressure hot water and turns it to steam.
• Binary heat exchange transfers the geothermal heat of hot water to another liquid. The heat causes the second liquid to become steam.
• Diversion dam provides pressure to push water into ditches, canals, or other areas for conveyance. It is typically lower in height and has a small water storage.
• Buttress dam consists of sloping deck supported by intervals of buttresses. EX: Magballo-Balicotoc-Canlamay dam
• Embankment dam is constructed with natural excavated materials or industrial wastes.
• Coffer dam is a temporary dam to close off some or all of a construction area.
• Storage dam is for emergencies. It supplies water when the elevation is low.
• Detention dam is for flood control.
• Gravity dam holds back water. It resists horizontal thrust of water and it holds the dam to the ground.
• Pumped storage - A method of storing energy in which water is pumped from a lower reservoir to a higher reservoir.
• Steps in geothermal extraction

  1. Hot water is pumped from the deep underground through a well under high pressure.
  2. When the water reaches the surface, the pressure is dropped, which causes the water to turn into steam.
  3. The steam spins a turbine connected to a generator and produces electricity.
  4. The steam cools off in a cooling tower and condenses back to water.
  5. The water is injected back into the earth
• Best locations for geothermal energy are located in the "Ring of Fire."
• Before, mechanical milling such as grinding of grains - the first use of hydropower.