4000 miles below the ground, the earth’s core radiates heat at around 9900 degrees F, similar to the sun’s surface! Basements are often cool in the summer and warm in the winter because the ground within 10 ft of the earth’s surface is a constant 50-60 degrees F. But, if we keep going deeper below the surface, we encounter molten rock known as magma around 90 miles down. The rock above magma is still extremely hot while remaining solid. If we can access this thermal energy to power our lives, we could have a clean and practically unlimited resource! This warmth is known as geothermal energy, a renewable and clean resource that comes from within the earth. Have you ever seen a hot spring or a geyser erupt? They are both examples of geothermal energy at work, using the heated rock miles below the surface.

Activity 1 – Rock, Water, and Heat Transfer

What is your thought about using heated rocks to heat water? Can some rocks better hold the heat than others? Find 3- 5 rock samples of different types, but as close as weight as possible. Make a guess which rock type will hold the highest heat and which will retain the lowest.

You’ll need boiling water, 3-5 rock samples, tongs, Styrofoam cups, and thermometers. Fill 3-5 Styrofoam cups with water at room temperature. Place the rocks in separate cups and submerge the rock samples in boiling water. Place a thermometer in each cup, until they reach 160 degrees F. Use tongs and be careful! After 30 seconds, take the temperature in each of the cups. Record the rock type and the temperature. How does heat transfer vary from one cup to another? Try this out with metals or other household materials

Activity 2 – Uses of Geothermal Energy

Research different uses for geothermal energy. How is it used in power plants, to heat and cool buildings, or for refrigeration? Pick a use for geothermal energy that you find interesting, and dive in to find out more about it! You’ll want to know:
- Target temperature and use
- History of its use
- Examples of it being used today
- How the heat is used (direct or electricity generation)
Write down your findings and make a brief report, or put together a slide presentation!

Activity 3 – Dry Steam Plants

The first type of geothermal power invented, dry steam plants drill directly into an underground resource to collect steam, which is used to power turbines. The steam is then condensed back into liquid water and injected back into the underground reservoir to ensure its reusability. Learn more about dry steam plants and draw a diagram showing how they work!

Activity 4 – Flash Steam Plants

Hydrothermal fluid at high temperatures is shot to the surface by high pressure in a subsurface reservoir (similar process to the eruption of geysers). At the surface, the fluid enters a separator where a drop in pressure flashes most of the liquid into steam. This steam powers turbines and generates electricity, while excess fluid joins water in the condenser and is reinjected back underground. Learn more about flash steam plants and draw a diagram showing how they work!

Activity 5 – Binary Power Plants

Hydrothermal fluid is pumped from a subsurface reservoir to the surface, where heat is transferred to a working liquid that has a low boiling point. This vapor creates powers in turbines. The working liquid is then condensed, while the hydrothermal fluid is injected into the Earth. This process can occur quickly because the hydrothermal fluid does not convert to steam or condense. Learn more about binary power plants and draw a diagram showing how they work!

Activity 6 – Direct Use

In areas where hydrothermal fluid is present close to the surface, geothermal energy can be used to heat buildings, dry crops, warm sidewalks, and more! These systems are prevalent in the western United States, where geothermal energy is available near the Earth’s surface. Learn more about the uses of geothermal energy and draw a diagram showing how it works!

Activity 7 – Geothermal Heat Pumps

Geothermal heat pumps enable heating and cooling of buildings even in regions where there is little geothermal energy near the surface. Two wells are drilled; one that pumps water to the surface to heat the building (during cold months) and one that drains heat (during warm months). While these systems are expensive in the short term, they provide long-term savings and utilize a clean and renewable resource. Learn more about geothermal heat pumps and draw a diagram showing how they work!

Review

• What is the constant temperature of the ground within 10 feet of the Earth’s surface?
• Molten rock below the Earth’s surfaces is known as
• first type of geothermal power plant to be made was the
• Geothermal energy sources are less prevalent in the western United States than the eastern United States.
• Geothermal heat pumps are used only in areas with plenty of geothermal energy near the surface