1.3 Utility Scale Power

PRESENTER: All right, we all know that the sun's energy creates heat and light. But it can also be converted to make electricity, and lots of it. One technology is called solar photovoltaics, or PV for short. You've probably seen PV panels around for years. But recent advancements have greatly improved their efficiency and electrical output. Enough energy from the sun hits the Earth every hour to power the planet for an entire year.

Here's how it works. You see, sunlight is made up of tiny packets of energy called photons. These photons radiate out from the sun. And about 93 million miles later, they collide with a semiconductor on a solar panel here on Earth. It all happens at the speed of light. Take a closer look, and you can see the panel is made up of several individual cells, each with a positive and a negative layer-- which create an electric field. It works something like a battery.

So the photons strike the cell, and their energy frees some electrons in the semiconductor material. The electrons create an electric current, which is harnessed by wires connected to the positive and negative sides of the cell. The electricity created is multiplied by the number of cells in each panel and the number of panels in each solar array. Combined, a solar array can make a lot of electricity for your home or business. This rooftop solar array powers this home. And the array on top of this warehouse creates enough electricity for about 1,000 homes.

OK, there are some obvious advantages to Solar PV technology. It produces clean energy. It has no emissions, no moving parts. It doesn't make any noise, and it doesn't need water or fossil fuels to produce power. And it can be located right where the power is needed, in the middle of nowhere, or it can be tied into the power grid. Solar PV is growing fast. And it can play a big role in America's clean energy economy-- anywhere the sun shines.

Ok Take the natural heat from the sun, reflect it against a mirror, focus all of that heat on one area, send it through a power system, and you've got a renewable way of making electricity.

It's called concentrating solar power, or CSP. Now, there are many types of CSP technologies. Towers, dishes, linear mirrors, and troughs. Have a look at this parabolic trough system. Parabolic troughs are large mirrors shaped like a giant "U." These troughs are connected together in long lines and will track the sun throughout the day. When the sun's heat is reflected off the mirror, the curved shape sends most of that reflected heat onto a receiver. The receiver tube is filled with a fluid. It could be oil, molten salt, something that holds the heat well. Basically, this super-hot liquid heats water in this thing called a heat exchanger, and the water turns to steam. Now, the steam is sent off to a turbine, and from there, it's business as usual inside a power plant. A steam turbine spins a generator and the generator makes electricity. Once the fluid transfers its heat, it's recycled and used over and over. And the steam is also cooled, condensed, and recycled again and again.

One big advantage of these trough systems is that the heated fluid can be stored and used later to keep making electricity when the sun isn't shining. Sunny skies and hot temperatures make the southwest, U.S. an ideal place for these kinds of power plants. Many concentrated solar power plants could be built within the next several years. And a single plant can generate 250 megawatts or more, which is enough to power about 90,000 homes. That's a lot of electricity to meet America's power needs.