Power Generation from Renewable Energy Sources

Fall 2012Instructor: Xiaodong Chu

Email ： chuxd@sdu.edu.cnOffice Tel.: 81696127

Course Meeting Times

• Lectures: 1 session (Mon.) or 2 sessions (Mon. and Wed.) / week, 2 hours / session

• Course materials accompanying the lectures can be obtained by visiting http://course.sdu.edu.cn/685.html –“教学资料” , “教学日历”

Course Overview

• The scope of renewable energy generation is relatively broad which includes hydropower, solar power, wind power, geothermal power, biomass power, wave power, tidal power, etc.

Course Overview

• Why do we limit the study scope with the emphasis on wind power and solar power?– Significant increase of installation capacity has

been witnessed of wind power and solar power in these years and this trend will continue evidently

– The intermittent nature of wind and solar power poses a great challenge to integrate the generation into the power network

Course Textbook

• Gilbert A. Masters. Renewable and Efficient Electric Power Systems. New York: John Wiley & Sons, 2004.

• An electronic version of the textbook is available for your reference and a translated copy in Chinese is accompanied

Course Lecture StructureTopic # Topics Readings

1 Wind power systems Chapters 6

2 Solar power systems Chapters 7, 8, 9

3 Energy storage systems Supplementary materials

Grading Activities Percentages

Class attendance and participation

30%

Final exam 70%

Wind Power Systems – Historical Development

• Wind has been used as a source of power for thousands of years

Wind Power Systems – Historical Development

• The world’s first wind turbine used to generate electricity was built by Poul la Cour ( 1846-1908) in 1891 in Denmark

Wind Power Systems – Historical Development

• Wind power industry underwent slow development worldwide until the early 1990s, although oil shocks of the 1970s had stimulated interests in wind power

• In the mid-1990s, wind power industry began to boom worldwide

• Could you make a brief survey of worldwide installed wind capacity in the first decade of 21st century, the leading countries, and the situation of China?

Wind Power Systems – Types of Wind Turbines

• Terminology of “wind driven generator”, “wind generator”, “wind turbine”, “wind turbine generator”, and “wind energy conversion system” all in use to call a machine generating electricity from wind

Wind Power Systems – Types of Wind Turbines

• Terminology of “wind driven generator”, “wind generator”, “wind turbine”, “wind turbine generator”, and “wind energy conversion system” all in use to call a machine generating electricity from wind

Wind Power Systems – Types of Wind Turbines

Wind Power Systems – Types of Wind Turbines

• One way to classify wind turbines is in terms of the axis around which the turbine blades rotate, i.e., horizontal axis wind turbines (HAWT) and vertical axis wind turbines (VAWT) and most are HAWT

Wind Power Systems – Types of Wind Turbines

• Horizontal axis wind turbines can be classified into upwind and downwind machines and most are of the upwind type

Wind Power Systems – Types of Wind Turbines

• Upwind machines require yaw control to keep the blades facing into the wind so operate more smoothly and deliver more power

• Downwind machines have the advantage to have the wind itself control the yaw, naturally orienting correctly with wind direction, but they have a problem associated with wind shadowing effects of the tower which causes the blade to flex

Wind Power Systems – Types of Wind Turbines

• Another fundamental design decision for wind turbines relates to the number of rotating blades

• Wind turbines with many blades operate with much lower rotational speed than those with fewer blades

• Most modern wind turbines have three or two rotor blades

Wind Power Systems – Power in the Wind

• Kinetic energy of a packet of air with mass m moving at a speed v

• Power represented by a mass of air m moving at velocity v through A is

• The mass flow rate through area A is

• And

2

2

1mvKE

2

2

1vm

Time

KEPw

Avm

3

2

1AvPw

Wind Power Systems – Power in the Wind

• Wind power increases as the cube of wind speed

• Wind power is proportional to the swept area of the turbine rotor– For a horizontal axis turbine, the area A is A =(π/4)D2, proportional to the square of the

blade diameter– For a vertical axis Darrieus rotor, the

approximated area A is A =2/3D·H

Wind Power Systems – Power in the Wind

• Temperature correction for air density– At 15oC and 1 atmosphere, the air density is 1.225 kg/m3

– For other temperature and pressure conditions,

RT

P -310gas theofweight molecular

Wind Power Systems – Power in the Wind

• Altitude correction for air density– Air pressure is a function of altitude and it is useful to have

a correction factor to estimate wind power at sites above sea level

H10185.10

4 ePP

Wind Power Systems – Impact of Tower Height

• Increases in wind speed have a significant impact on power production and it tends to mount wind turbine on a taller tower to get higher wind speeds

• In the few hundred meters above the ground, wind speed is greatly affected by the friction that the air experiences as it moves across the earth’s surface

• One expression to characterized the impact of the roughness of the earth’s surface on wind speed is

The friction coefficient α is a function of the terrain over which the wind blows

00 H

H

v

v

Wind Power Systems – Impact of Tower Height

• Another approach expressing the impact of the roughness is

The parameter z is called the roughness length

)/ln(

)/ln(

00 zH

zH

v

v

Wind Power Systems – Impact of Tower Height

• To use the exponential expression and the relationship between wind power and speed, we can get

• Could you indicate the relative power of the wind at height H versus the power at the reference height of H0 the using the logarithmic expression?

3

00

H

H

P

P

Wind Power Systems – Impact of Tower Height