Energy. on this world and elsewhere. Instructor: Gordon D. Cates Office: Physics 106a, Phone: (434)

Transcription

1 Energy on this world and elsewhere Instructor: Gordon D. Cates Office: Physics 106a, Phone: (434) Course web site available at click on classes and find Physics or at Lecture #19 March 31, 2016

2 Announcements Homework #2 is due today, March 31. Two-page paper is due April 12. Office hours, probably Tuesday at 4:30 and Wednesday at 7:30, will be available next week to discuss the paper and its content.

3 Midterm paper topics

4 Midterm paper topics

5 Midterm paper topics

6 Wind

7 Computing the power carried by wind A Power = 1/2 A ρ v 3 Here the area A is the area swept out by the blades of the windmill.

8 What is the power hitting a real windmill? r = 40 meters

9 Generated power versus wind speed How much power is carried by the wind for a wind speed of 15 meters per second? efficiency at 15 m/s = 2/10.94 = 18.3%

10 Generated power versus wind speed At 10 m/s, the graph indicates power output of roughly 1.4 MW. The power of the wind at 10/ms = 3.42 MW efficiency = 1.4 MW / 3.42 MW = 40.9%!!!

11 Windmill with broken regulating mechanism

12 Solar Energy

13 The price of solar cells

14 U.S. PV electricity installed capacity and generation I believe about half of the 2014 number is utility scale, larger than what I said before

15 U.S. PV annual capacity additions by sector From this, it looks like new capacity is being added fastest by the utilities

16 Rooftop versus utility scale

17 U.S. Concentrated Solar Power (CSP) electricity installed capacity and generation

18 U.S. utility-scale solar electricity capacity: operating and in the pipeline

19 The concept of intensity In the context of sunlight: Intensity of sunlight = Incident power of sunlight area over which it falls

20 Intensity of sunlight hitting the earth Above the atmosphere: about 1.4 kw/m2 - This is for a surface FACING the sun. On the Earth s surface: about 1.0 kw/m2 Averaged over day and night, all the seasons, for the 48 contiguous states in the U.S.: around 200 W/m 2

21 Area needed to generate electricity using solar power Power = efficiency x Intensity x Area Area = Power efficiency x Intensity

22 Area needed to generate electricity using solar power 83.4 mi. x 83.4 mi., area needed to produce (on average) all electricity currently used (assuming 200 W/m 2 ).

23 Area needed to generate electricity using solar power 83.4 mi. x 83.4 mi., area needed to produce (on average) all electricity currently used (assuming 200 W/m 2 ). 118 mi. x 118 mi. (twice the above mentioned land area).

24 Area needed to generate electricity using solar power 441 million acres devoted to cropland (for comparison) mi. x 83.4 mi., area needed to produce (on average) all electricity currently used (assuming 200 W/m 2 ). 118 mi. x 118 mi. (twice the above mentioned land area).

25 Solar thermal generation of electricity

26 Types of Solar Thermal Parabolic Trough - Most existing facilities, and currently approved facilities in California are of this variety. Solar-tracking dish-based collectors with Sterling Engines This is the SES design, and their are currently 1 or 2 proposed large-scale facilities in California. Power-tower design. - Several have been built, but in the tens of Megawatt range.

27 The Solar Power Tower Design Multiple mirrors called heliostats track the sun and reflect light onto a central collector. Temperatures are so high that molten salt is used as the liquid that get heated. The molten salt, in turn, is used to produce steam that drives turbines to make electricity. The molten salt stores heat so well that the plant can produce electricity for several days without sunlight.

28 Solar Two - 10 MW demonstration project

29 Solar Two - 10 MW demonstration project This system is no longer in operation for the production of electricity.

30 20 Megawatt System near Seville Spain

31 Solar Two - 10 MW demonstration project

32 Solar Thermal The Ivanpah Solar Plant: 377 MW facility nearing completion in the Mojave desert in California.

33 Solar-thermal technology: one example

34 Solar-thermal technology: one example

35