Lesson 8 Energy Conversions

The gasoline or diesel that you put into an automobile comes from the refining of fossil fuels. Remember that fossil fuels were formed millions of years ago from dead plants and animals. The original source of energy for all plants and animals is the sun.

When riding a bicycle, you must first supply the energy required to get the bicycle moving. You pedaling the bicycle transforms chemical energy in your body to mechanical energy (kinetic energy) that is the movement of the bicycle.

When it comes time to apply the brakes and stop the bike, what transformations occurs?

The fuels used in thermal power plants are most often fossil fuels. Again, remember that fossil fuels were formed millions of years ago from dead plants and animals. The original source of energy for all plants and animals is the sun.

Photosynthesis is the beginning of a chain of energy conversion in an ecosystem, and is in every food chain. When animals feed on the plants that undergo photosynthesis, the energy is transferred to the animal. As you move up the food chain, energy continues to be transformed and transferred.

Much of the energy is used at each level, and some “waste” energy is also lost. Approximately 10% of the energy gets transferred from one level to the next.

$$\begin{gathered} \mathrm{sun}\to \mathrm{grass} \stackrel{10\% \mathrm{chemical} \\ \mathrm{energy} \mathrm{passed} \mathrm{on}}{\to } \mathrm{vole}\stackrel{10\% \mathrm{chemical} \\ \mathrm{energy} \mathrm{passed} \mathrm{on}}{\to } \mathrm{great} \mathrm{grey} \mathrm{owl} \end{gathered}$$

A heat pump is a device that is designed to move thermal energy in the opposite direction that heat naturally moves. According to the second law of thermodynamics, thermal energy moves from warm spaces to cold spaces. A heat pump absorbs heat from a cold space and releases it to a warmer one. This is similar to how active transport, which you learned about in Unit A, is moving particles against the concentration gradient.

Air conditioners and freezers are examples of devices that use heat pumps. Heat pumps contain a fluid that is a refrigerant, which will absorb and release heat easily. There are also reversible heat pumps, which can work in either direction to provide heating or cooling in the same space.

Similar to active transport in cells, energy is required to move thermal energy in the opposite direction that heat naturally moves. Heat pumps use electrical energy to force the transfer.

Sunlight warms up surface water, causing it to evaporate. Water vapor rises and forms clouds, which release water as rain or snow. Water then becomes part of the flowing river.

A hydroelectric power plant uses a dam on a river to store water in a reservoir behind the dam. When water is released from the reservoir, the water flows through a turbine, spinning the blades of the turbine. The spinning turbine then activates a generator, which produces electricity.

A windturbine uses the kinetic energyof the windto create electricity. The air is heated by the sun, which creates wind. Then, the windflows through a rotor, spinning the blades of the rotor. The spinning rotor then activates a generator, which produces electricity.