Geothermal Energy

Geothermal energy uses heat from within the earth to provide power. It is considered renewable
because of the constant supply of heat from the earth and is “green” because there are minimal
emissions.

Geothermal plants are developed after exploration for a suitable location. Plants need access to
aquifers that are adjacent to hot rock. A production well is drilled to access the heat and steam used to
generate electricity. Once brought to the surface, there are three methods used to produce electricity.
They are flash, dry steam, and binary. 

Geothermal plant (US Energy Information Administration)

A flash plant uses a steam separator to separate steam from water. Steam goes to turbines that power a
generator, while the water is reinjected into the ground where it becomes steam to start the cycle over.
A dry steam plant functions similarly, but there is no water and no need for a steam separator. Steam
alone turns the turbines. As it cools and condenses into water, it is reinjected back into the ground.

Binary geothermal plants use hot water from beneath the surface to boil another liquid, such as
isobutene, that has a lower boiling point than water. The vaporized fluid powers the turbines. The
water is reinjected into the ground, while the vaporized fluid goes through a condenser and a preheater
before returning to the vaporizing chamber and powering the turbines again.

How a geothermal plant works (Mechanical Technology)

A geothermal heat pump is similar to passive solar heating and cooling. Water circulates into the
ground to bring up the earth’s heat or to carry indoor heat underground to cool a building. Direct use
geothermal uses geothermal heat without use of a plant or heat pump. Hot water or steam is brought to
a plate heat exchanger for heating and cooling of a building.

Geothermal plants emit low levels of carbon dioxide and sulfides (hydrogen sulfide mainly) that occur naturally in the subsurface water and steam. Scrubbers can remove most of the hydrogen sulfide. Sulfide emissions are generally lower than fossil fuel plants (US Energy Information Administration, 2015).

This week's information comes from Geothermal Energy Association and US Energy Information Administration. Next week we'll be taking a break for the Species of the Month before returning to check out the pros and cons of nuclear energy.

The Good Old Days

This week’s adventure takes a peek at the past. Earth was a vastly different place in the good old days. Dinosaurs ruled and everything was just a bigger, sabre-toothed version of the critters we have today. OK, maybe not the bigger, pointier critters. But scientists can tell us a lot about the way things used to be by looking at the fossil record.

Fossils are like prehistoric pictures. They form when dead organic material is slowly replaced by mineral material. Not everything that ever died was destined to become a fossil; only in certain conditions could the transition take place. Being in a situation without oxygen would’ve helped your cause if you were hoping to fossilize. Oxygen is a requirement for decomposition. If you’re decomposing, you won’t leave behind anything to fossilize. 

Little worm fossils imprinted on a rock

Usually when you think of fossils you think of huge dinosaur bones. There are other types of fossils too. Footprints in dried mud that later turned to stone can be found in Alaska and Africa.

Dinosaur footprint found at Denali National Park (NPS)

Imprints of shells in rock are mountains that used to be sea floor. One wound up in my back yard in Pennsylvania. One day a dead plant was buried in between layers of sediment that hardened into rock. Years later, I squeezed that rock and found black images of that plant inside the rock. Whole trees can be fossilized into petrified wood. Ancient insects trapped in tree sap that hardened into amber are also fossils.

A rock full of shells from my back yard

Plant fossils inside a piece of sedimentary rock

If you want to find some fossils, you don’t need to be a paleontologist or geologist. All it takes is a little luck and some sedimentary rock. Igneous rock is volcanic in nature, so that won’t be likely to preserve any critters. Metamorphic rock is rock that has changed from heat and pressure, so no luck there either. But sedimentary rock is just dirt that compacted into rocks. If you go on a fossil hunt, respect private property and remember not to take anything from or do any damage to national parks.

Petrified wood- looking at the rough bark

Petrified wood- look closely and you can see the grains

Ant trapped in amber (Smithsonian)