Unit 6.10 - Geothermal Energy

Question 1

Geothermal Basics

Answer 1

• Natural Radioactive decay os elements deep in earth’s core gices off heat, drivin magma convection currents which carry heat to upper portion of mantle, close to earth’s surface
  - water can be piped down into the ground and heated by this heat from the mantle (hot water can be converted into stea, -> turbine -> electricity or be used to heat homes directly)
• Geothermal for electricity: naturally heated water reserviors underground are drilled into and piped up to the surface (or water can be piped down into naturally heated rock layers)
  - the heat from the magma turns the water into seam, which is forced through piped to spin a turbine
  - Water is cooled in cooling towers and returned to the groud to start the process over
  - Renewable since heat from the earth’score won’t run out, but only if groundwater is returned after using

Question 2

Ground Source Heat Pump

Answer 2

• Often referred to as “geothermal” but technically the heat does not come from geologic activity (comes from the ground storing heat from the sun)
  - More accurate name is “ground source heat pump”
  - 10 feet down, the ground stays a consistent 50-60o due to holding heat from sun (not warmed by geothermal energy from magma - so not technically geothermal energy
  - Heat absorbing fluid is pumped through a pipe into the ground where it either takes on heat from the ground, or gives off heat to the ground
  - In summer, heat from home transfers to liquid & liquid transfers heat to the ground, cooling house
  - In winter, liquid takes heat from ground & transfers it to the house, warming house

Question 3

Geothermal Heating

Answer 3

• True geothermal heating involves piping water deep into ground to be heated by magma and then transfering heat from water to the building
  - different than groundsource heat pump
  - well must go thousands of meters (kms) down into the ground to reach heated watr reservior
  - Heated water is piped up to surface and sent to homes or businesses to heat them

Question 4

Geothermal Pros

Answer 4

• Potentially renewab;e only if water is piped back into the ground for reuse
• much less CO2 emissions than fossil fuel electricity
• No release of (PM, NOx, SOx, CO) as is the case with fossil fuels

Question 5

Geothermal Cons

Answer 5

• Not everywhere on earth has access to geothermal energy reaching close enough to surface to access it
• Hydrogen sulfide can be released, which is toxic and can be lethal to humans and animals
• Cost of drilling that deep in the earth can bevery high initially
  - sometimes so high that its noteven worth it