1. PSAA Curriculum Unit Physical Science Systems

2. Problem Area Energy and Power Systems

3. Alternative Energy Sources Lesson

4. Why is there a variation in temperatures among different substances? Measure the temperature of several substances which are exposed to the same amount of sunlight.  Air inside greenhouse  Air outside greenhouse  Soil  Surface of a paved parking lot

5. Learning Objectives Define solar power as an energy source. Define wind power as an energy source. Define water power as an energy source. Define biomass as an energy source. Identify other alternative sources of energy.

6. Terms Biomass Conduction Convection Geothermal energy Hydroelectric power Hydroelectricity Hydrogen fuel cells Hydrologic cycle Photovoltaic cell Radiant energy Radiation Semiconductors Solar cell Solar collector Solar energy Water energy Wind energy Wind farms Wind turbine

7. What is solar energy and what uses does it have as a renewable energy source? Heat can be transferred from one place or object to another by conduction, convection, or radiation.

8. What is solar energy and what uses does it have as a renewable energy source? Conduction is the transfer of heat within materials or between materials that are in direct contact.  Materials that conduct heat are known as conductors.

9. What is solar energy and what uses does it have as a renewable energy source? Heat transfer by the movement of the heated substance itself is known as convection.  Warmer air in a room rises because it is less dense than cooler air.  Heated water molecules expand and the warmer water rises to the surface because it is less dense.

10. Solar Energy (cont.) Energy given off by the sun as light, heat, and other forms of electromagnetic radiation is known as solar energy. Invisible heat waves carry heat from the sun to the earth. This transfer of energy by electromagnetic waves through space is radiation.

11. Solar Energy (cont.) Radiant energy is any energy transmitted by radiation. Hot objects radiate heat waves that are received by cooler objects. Heat energy from the sun becomes radiant energy when the heat is absorbed by an object.

12. Solar-Powered Water Pump for Horses

13. Solar Energy (cont.) Darker materials absorb greater amounts of radiant energy and reflect lesser amounts.  Black material absorbs all light falling on it and reflects no radiant energy. Light-colored objects reflect more heat and light than dark-colored ones. Thus, the darker the material, the more radiant energy it absorbs and the warmer it becomes.

14. Solar Energy (cont.) A solar cell (photovoltaic cell) converts light energy into electricity. Solar cells contain semiconductors, which allow the flow of electrons to be controlled. A large solar collector is made up of many solar cells. Each solar cell includes two layers of different types of silicon.

15. Solar Cell Mount

16. Thermosyphon Water Heater with Solar Collector

17. Solar Cell An individual solar cell has an upper n-type layer of silicon and a lower p-type layer of silicon.  The n-type layer is positively charged while the p- type layer is negatively charged. Light strikes the cell; rays penetrate the upper n-type layer, and free electrons from atoms in the lower p-type layer.

18. Solar Cell (cont.) Electrons move into the upper n-type layer. The difference in charges of the layers makes the electrons move. A contact collects the moving electrons and current is generated as the electrons flow.

19. Cleaning a Solar Cell

20. What is wind energy and what uses does it have as a renewable energy source? Temperature differences in the atmosphere create variations in atmospheric pressure, which causes air to move from high low pressure regions. Air movements that prevail over a large area and remain fairly constant in direction are called prevailing winds. Wind energy is a form of solar energy that can be used to power water pumps and generate electricity or heat.

21. Wind Energy (cont.) Wind turbines with only two or three aerodynamic blades have replaced the windmill. The wind turbine drives a generator that produces electricity to operate small, submersible pumps that are more efficient than the piston pumps used by traditional windmills. Rotor blades on wind turbines can be at least 300 feet in length across.

22. Wind Energy (cont.) Electricity is now being generated on a commercial scale at large facilities called wind farms in numerous places around the world. Wind farms consist of runs of towers, sometimes 90 meters high, equipped with giant wind turbines for electricity production.

23. Wind Energy (cont.) Commercial wind energy is one of the most economical sources of new electricity in use today. Wind turbines can be set up quickly and cheaply compared to new coal-fired generating stations and/or hydroelectric installations.

24. Wind Energy (cont.) Wind generating materials are efficient, highly reliable, and becoming cheaper to purchase. Environmental impact of wind turbines is negligible compared with a coal mine or a reservoir and they produce no air pollution during use. Small, efficient wind turbines are increasing in popularity for use as a source of electricity for rural homes.

25. What is water energy and what uses does it have as a renewable energy source? Running water forms tiny streams, which gather to form rivers. Rivers find their way to the edge of continents, where they dump massive loads of fresh water and sediments into the oceans. Evaporation brings the water back into the atmosphere as water vapor.

26. Water Energy (cont.) Water vapor condenses from the air to form clouds and possibly rain, snow, or hail. Seasonal rains and snow bring fresh water back to the headwaters of streams, completing a very important system called the hydrologic cycle.

27. Hydrologic Cycle

28. Water Energy (cont.) Rivers and streams are among nature’s most powerful forces. The force of water moving down a moderately-sized river can exceed several million horsepower. This is the force humans attempt to harness when they build dams to generate electricity.

29. Water Energy (cont.) Besides rivers, ocean waves, tides, and currents move unimaginable amounts of water around everyday. Currents and waves are usually caused by winds blowing over the surface, while tides are caused by the moon’s gravity pulling gently on the earth. Wave, tide, and current action are especially noticeable near coastlines and islands.

30. Water Energy (cont.) Electricity produced from the falling water energy is called hydroelectricity. Hydroelectric power facilities often depend on a dam to raise the level of the water in the reservoir. Water from the reservoir is allowed to fall through large pipes to a building that houses water-driven turbines.

31. Water Energy (cont.) Pressure from the falling water spins the turbines at high speed. The turbines are connected to large generators that make electricity as they turn.

32. Water Energy (cont.) Large-scale hydroelectric facilities usually have a big impact on the ecology of the river upstream from the dam. Areas of forest or farmland are covered with water when the reservoir is filled and dams block the natural migration of fish and aquatic creatures up and down the river.

33. What is biomass and what uses does it have as a renewable energy source? Biomass refers to any form of plant or animal tissue. In the energy industry, biomass refers to wood, straw, biological waste products such as manure, and other natural materials that contain stored energy.

34. What is biomass and what uses does it have as a renewable energy source? Bioenergy is energy stored in items made from living things. Wood is produced from living trees and its heat is humanity’s oldest energy source. Other sources of bioenergy are alcohol and biogas. Alcohol is a flammable liquid made by certain yeasts, and biogas is a flammable gas similar to natural gas, made by bacteria.

35. Biomass (cont.) Green plants have large amounts of a material called cellulose. Green plants manufacture cellulose from sugars, which are made during photosynthesis.

36. Biomass (cont.) Cellulose contains stored chemical energy, energy that originally came from the sun, and can be released as heat when wood is burned. Wood has been used as a fuel far longer than any fossil fuel. Grass, peat, and cow manure can be used as fuel if wood is scarce, but the fires are extremely smoky.

37. Biomass (cont.) Ethanol and methanol are alcohols and are highly flammable. Alcohol is produced by feeding plant materials into large heated tanks called digesters. Chemicals or yeasts are added to change the plant materials into alcohol. The alcohol is extracted, purified, and prepared for use as fuel.

38. Biomass (cont.) Ethanol and methanol make excellent fuels for vehicles. Ethanol burns very cleanly and delivers more power than gasoline. Gas stations sell fuels that contain a blend of gasoline and ethanol. Methanol and ethanol are deadly poisons, especially in the amounts used to make fuels for transportation.

39. Biomass (cont.) Most mammals produce a flammable gas called biogas as they digest their food. Bacteria living in the digestive systems of these animals produce methane as they break down cellulose in the food.

40. Biomass (cont.) Biogas consists mainly of a gas called methane, which is the same as natural gas, commonly burned in our furnaces. Biogas generators have been developed to blend shredded plant materials and animal wastes with water.

41. Biomass (cont.) Naturally occurring bacteria exist on the shredded plant material. The generator is sealed for an anaerobic environment that produces methanogenic bacteria that produce methane. The methane is piped off and stored until needed. Once the process fades, a new batch of water and manure is added to start the process again.

42. Biomass (cont.) Another source of biogas is landfills. This gas is collected and burned to heat buildings. Biogas can contain traces of hydrogen sulphide gas, especially in landfills, and may be fatal in small amounts.

43. What other sources of alternative energy are in use today or the near future? Wind, solar, biomass, and water are not the only sources of clean, environmentally friendly energy. Other energy sources can also provide heat, light, and electricity without polluting the air or disturbing large areas of land or water.

44. Other sources of alternative energy. Geothermal energy is the energy created by the slow breakdown of radio-active elements, and by the immense gravitational pressure acting on the rocks and minerals of the earth’s interior. Temperatures in excess of 500 degrees Celsius can be found in the earth’s crust just a few thousand meters below the surface.

45. Other sources of alternative energy. Hydrogen fuel cells allow hydrogen and oxygen gases to pass near each other on opposite sides of a thin membrane. The chemical interaction of oxygen and hydrogen across this membrane produces an electric charge, similar to that produced by a regular alkaline battery. Unlike the battery, the fuel cell continues to produce electricity as long as it receives fresh supplies of air and hydrogen. The only by-product of the process is water, which is released as steam.

46. Review/Summary What is solar energy and what uses does it have as a renewable energy source? What is wind energy and what uses does it have as a renewable energy source? What is water energy and what uses does it have as a renewable energy source?

47. Review/Summary What is biomass and what uses does it have as a renewable energy source? What other sources of alternative or renewable energy are in use today or the near future?