Environmental Science Environmental Science Solar Energy Lecture Notes.

Environmental Environmental ScienceScience

Solar Energy Solar Energy Lecture NotesLecture Notes

Solar Energy is Solar Energy is RENEWABLERENEWABLE

Renewable vs. Renewable vs. Nonrenewable Energy Nonrenewable Energy

ResourcesResources

DEMO:DEMO:

Solar Energy can Solar Energy can be used 3 ways:be used 3 ways:

Solar HeatingSolar HeatingSolar Heating Solar Heating Electricity ElectricitySolar Radiation Solar Radiation Electricity Electricity

Solar Hot Water Solar Hot Water 1890: solar water heaters used in sunny 1890: solar water heaters used in sunny

states like California, Arizona, and Floridastates like California, Arizona, and Florida Artificial gas made from coal was Artificial gas made from coal was

available, but cost 10X the price we pay available, but cost 10X the price we pay for natural gas todayfor natural gas today

1920: 1,000’s of solar water heaters had 1920: 1,000’s of solar water heaters had been sold. BUT … large deposits of been sold. BUT … large deposits of oil/natural gas were discovered in U. S. oil/natural gas were discovered in U. S.

Solar water systems were replaced with Solar water systems were replaced with heaters burning these cheaper fossil heaters burning these cheaper fossil fuels.fuels.

Solar collector forheating water

A home in California in 1906

• Today, solar water heaters are Today, solar water heaters are making a comeback (more than making a comeback (more than ½ million in California alone!).½ million in California alone!).

• Heat water for Heat water for homes/businesses and homes/businesses and swimming pools (see picture) swimming pools (see picture)

• Panels on roof contain water Panels on roof contain water pipes. Sun hits the panels and pipes. Sun hits the panels and pipes. pipes.

• Warmed water is then used in a Warmed water is then used in a poolpool

Solar Thermal Electricity Solar Thermal Electricity Solar energy Solar energy electricity electricity Some solar power plants (see Some solar power plants (see

picture from Mojave Desert) use picture from Mojave Desert) use curved mirror called PARABOLIC curved mirror called PARABOLIC TROUGH to focus sunlight on a TROUGH to focus sunlight on a pipe running down center of mirror.pipe running down center of mirror.

Mirror focuses sunlight onto the Mirror focuses sunlight onto the pipe, causing the water to boil and pipe, causing the water to boil and produce steam. Steam can then be produce steam. Steam can then be used to turn a turbine to make used to turn a turbine to make electricity. electricity.

These rows of solar mirrors These rows of solar mirrors arranged in "solar thermal power arranged in "solar thermal power plants“. They make electricity for plants“. They make electricity for more than 350,000 homes. more than 350,000 homes.

Solar Thermal Electricity Solar Thermal Electricity PROBLEM: Works only when sun is PROBLEM: Works only when sun is

shining. On cloudy days/at night, the shining. On cloudy days/at night, the power plants can't make electricity. power plants can't make electricity.

Some solar plants, use "hybrid" Some solar plants, use "hybrid" technologytechnology During day they use sun. During day they use sun. At night/cloudy days they burn At night/cloudy days they burn natural gas to boil water to natural gas to boil water to generate electricity.generate electricity.

SOLAR THERMAL ELECTRICITYSOLAR THERMAL ELECTRICITY

Another form of solar power (heat) to make electricity:

(Central Tower Power Plant)

Sunlight is reflected off 1,800 mirrors (HELIOSTATS) circling the tall tower.

Fluid (liquid sodium) is heated by sun's rays. The fluid is used to boil water make steam turn a turbine and generator

This experimental power plant is called Solar II. It was built in California's desert.

Scientists say larger central tower power plants can make electricity for 100,000 to 200,000 homes.

Solar Cells or Photovoltaic Energy Solar Cells or Photovoltaic Energy Sunlight converted directly to electricity

using solar cells Solar cells also called photovoltaic cells (PV

cells) and can be found on many small appliances, like calculators, and even on spacecraft

First developed in 1950’s for U.S. space satellites.

Made of silicon, special type of melted sand Sunlight strikes solar cells and electrons

(red circles) are knocked loose. They move toward treated front surface (dark blue color). When the two surfaces are joined by a wire, a current of electricity occurs between negative and positive sides.

Solar cells PV module Array. Some arrays are set on special tracking

devices to follow sunlight all day long.

Photovoltaic Energy Video

Electrical energy from solar cells can be used for lights/appliances

Solar energy can be stored in batteries to light roadside billboards at night

Energy can be stored in a battery for emergency roadside telephones where no phone wires are around

Some experimental cars also use PV cells. They convert sunlight directly into energy to power electric motors on the car.

Solar cells are used in satellites in outer space. Here's a picture of solar panels extending out from a satellite.

Rooftop PV Modules