February, 2004
Page 3
Science News - Solar Electricity
Most solar power that we use on Earth is indirect solar power. That means that the heat and energy from the sun are collected and used to heat water or air or other materials. The heated materials can be used to give off heat or to heat water or something that can turn a turbine to produce electricity. I knew there were no turbines on the Mars rovers so they had to be using something else. What I found out was that the Mars Rovers use a direct method of solar power which means that it uses the sun's energy to actually make the electricity. They use solar cells that are put into panels. Here's how it works:
*The silicon has to be prepared in a special way.
*The silicon is made up of a strong glass-like material.
*The silicon is put into a layer of the solar cell and acts like a barrier to the movement of electrons in a certain direction. (I already knew that when electrons move in one direction they create a flow of electricity.)
*When the sun's rays hit the solar cells, photons are absorbed in the surface of the silicon and negative charges are displaced (moved). The silicon barrier allows the negative charges to move to the other side of the cell, but it is much harder for the positive charges to pass through. So the negative charges move across the barrier and create a flow of electricity.
*This electricity is what powers the Mars Rovers!