Wind Energy Basics - Queen's Universitymy.me.queensu.ca/Courses/MECH4301/files/Lec13... · Wind Energy Basics Lecture 13 Based ... and a complex control system but is a complex ...

Wind Energy BasicsLecture 13

Based on a Presentation made byMarc Chappell, MSC Enterprises,

Energy Efficiency and Renewable and Energy Workshop,Feb. 5, 2003, Kingston, ON,

and information from http://www.windpower.org

Plus additional sources as noted

The Wind Resource

• Wind is the approximate horizontal movement of air caused by differential heating of the earth’s surface

• Air rises from the warmer surfaces and cooler is drawn in from the surrounding areas.

The Wind Resource

• Wind is affected by topography—wind speed is affected by roughness and obstacles such as buildings and hills.

• Speed increases when approaching the obstacle and decreases and may separate and become turbulent of the downstream side

The Wind Resource

•Wind turbines are often placed near the top of hills and ridges and well away from buildings and other structures

The Wind Resource

The “windiness” of a particular site is described in terms of the Annual Average Wind Speed

The Wind Resource

• Wind speed varies with time over several orders of magnitude

• Rapid fluctuations in wind speed are called turbulence and may increase the structural and dynamic stresses on the wind turbine components

• Thus it is not desirable to install turbines in areas of high turbulence

The Wind Resource

• Near the earths surface wind speed is reduced by friction

• Wind turbines operate in the earth’s boundary layer

• The higher the wind turbine tower, the greater the annual average wind speed

The Wind Resource

Wind speed is related to height by

The exponent α depends on the type and roughness of the terrain.

For flat land without major obstructions, α = 0.16 and wind speed increase

12% for every doubling of height.

Power and Energy in WindThe Kinetic Power in a moving air stream is given by

KP = ½ ρAV3

Where KP = Power in Wind, (Watts)ρ = Air density(1.225 kg/m3 at 15oC, 1.0132 bar)A= Cross-sectional flow area (m2)V = Wind speed (m/s)

Note: Power is proportional to the CUBE of wind speed

Power and Energy in WindAverage power is not linearly proportional to the average wind speed!

KPave = 6/π (½ r AVave3)

The term , 6/π , accounts for the distribution of wind

speed, and hence kinetic power with wind with

time. Average power is not linearly proportional to the average wind speed

e,g., a 10 m/s wind blowing through a 1 m2 window

KPave = 6/π (½ 1.225 x 1 x 103)= 1170 W = 1.17 kW

Wind Speed Distributions

It is very important to be able to describe the variation of wind speeds.

Turbine designers need the information to optimize the design of their turbines, so as to minimize generating costs.

Turbine investors need the information to estimate their income from electricity generation.

Wind Speed Distributions

Weibull Distribution

If you measure wind speeds throughout a year, you will notice that in most areas strong gale force winds are rare, while moderate and fresh winds are quite common.

The wind variation for a typical site is usually described using the so-called Weibull distribution, as shown in the image. This particular site has a mean wind speed near 7 m/s. The shape of the curve is determined by a so called shape parameter of 2, i.e., k= 2.

See http://www.windpower.org/en/tour/wres/weibull.htm

Power and Energy in Wind

There is an optimum condition where the product of the wind speed and flowrate is maximum.

This known as the BETZ LIMIT and is 59.2% of the inflowing kinetic power.

On average, good wind turbines extract about half of the theoretical maximum or 30% of the power in the airstream that passes through the rotor, thus

Pave = 0.3 x 6/π (½ r AVave3)

= 0.35 AVave3

Power and Energy in Wind

Turbine output effectively increases as the square of the diameter, e.g.,

D1 = 25 m, P1= 225 KwD2 = 50 m, P2= ?

P2 = (50/25)2 x P1 = 900 kW

Actual turbine output will vary somewhat due to specific design features and turbine performance

Power and Energy in Wind

Power Example: simplified calculation

Power and Energy in WindEnergy Example: Simplified Calculation

i.e., for the above example the annual energy output would be 650 MWh/y – sufficient for 80 homes

Wind Turbines

• Horizontal Axis

Eole C, a 4200 kW Vertical axis Darrieus wind turbine with 100 m rotor diameter at Cap Chat, Québec, Canada. The machine (which is the world's largest wind turbine) is no longer operational.

• Vertical Axis

Wind Turbine Selection

• Rotor diameters may vary somewhat for a given power, because many manufacturers optimize their machines to local wind conditions.

• A larger generator requires more power (i.e., stronger winds) to start. So if you install a wind turbine in a low wind area you will actually maximize annual output by using a fairly small generator for a given rotor size (or a larger rotor size for a given generator).

• For example, for a 600 kW machine, rotor diameters may vary from 39 to 48 m (128 to 157 ft.) The reason why you may get more output from a relatively smaller generator in a low wind area is that the turbine will be running more hours during the year (i.e., higher capacity factor).

Wind Turbine SelectionReasons for Choosing Large Turbines • There are economies of scale in wind turbines, i.e. larger machines are

usually able to deliver electricity at a lower cost than smaller machines.

• The cost of foundations, road building, electrical grid connection, plus a number of components in the turbine (the electronic control system etc.), are somewhat independent of the size of the machine.

• Larger machines are particularly well suited for offshore wind power. The cost of foundations does not rise in proportion to the size of the machine, and maintenance costs are largely independent of the size of the machine.

• In areas where it is difficult to find sites for more than a single turbine, a large turbine with a tall tower uses the existing wind resource more efficiently.

• Large machines, however, will usually have a much lower rotational speed than small machines, i.e., one large machine really does not attract as much attention as many small, fast moving rotors.

Wind Turbine SelectionReasons for Choosing Smaller Turbines

• Local electrical grids may be too weak to handle the output from a large machine. This may be the case in remote parts of the electrical grid with low population density and little electricity consumption in the area.

• There is less fluctuation in the electricity output from a wind park consisting of a number of smaller machines, since wind fluctuations occur randomly, and therefore tend to cancel out.

• Costs for large cranes and building adequate roads to carry the turbine components may make smaller machines more economic in some areas.

• Several smaller machines spread the risk in case of temporary machine failure, e.g., due to lightning strikes.

• Aesthetic landscape considerations may sometimes dictate the use of smaller machines.

Turbine Performance: The Power Curve

The power curve of a wind turbine indicates the electrical power output for the turbine at different wind speeds.

The graph shows a power curve for a typical 600 kW wind turbine. Power curves are found by field measurements of power output versus wind speed. An anemometer is placed on a mast reasonably close to the wind turbine to measure the wind speed.

Turbine Efficiency (Power Coefficient)

The graph shows a power coefficient curve for a typical wind turbine. The average efficiency is about 20 per cent. It varies with the wind speed, but is largest at around 9 m/s.

At low wind speeds efficiency is not as important because there is not much energy to harvest. By design, at high wind speeds, the turbine wastes excess energy above the generator rating.

The power coefficient tells you how efficiently a turbine converts the energy in the wind to electricity. Very simply, we just divide the electrical power output by the wind energy input to measure how efficient a wind turbine is.

Actual performance

The power output of a particular wind turbine will be significantly lower than the available wind due to Betz’ Law and turbine efficiency.

As well, the turbine may not operate all the time, further reducing the annual energy delivered.

Annual Performance

The graph opposite shows the expected annual output versus wind speed for different values of the

Weibull function, k.

This function describes the distribution of the wind velocities at a particular site.

The performance of a particular wind turbine will be a function of the conditions and design features previously described.

Horizontal Axis “HAWT”

Horizontal Axis “HAWT”

Rapid fluctuations in wind speed are called turbulence and may increase the structural and dynamic stresses on the wind turbine components

Turbine Loading

Wind turbines are therefore generally designed so that they yield maximum output at wind speeds around 15 m/s.

Its does not pay to design turbines that maximize their output at stronger winds, because such strong winds are rare.

Speed and Power Output Control

In case of stronger winds it is necessary to waste part of the excess energy of the wind in order to avoid damaging the wind turbine. All wind turbines are therefore designed with some sort of power control.

Stall Controlled Wind Turbines

(Passive) stall controlled wind turbines have the rotor blades bolted onto the hub at a fixed

angle. The geometry of the rotor blade profile is aerodynamically designed to ensure that as

wind speed becomes too high, it creates turbulence on the leeward side of the rotor blade.

Stall control avoids moving parts in the rotor, and a complex control system but is a complex

aerodynamic design problem. It introduces design challenges in the structural dynamics of

the whole wind turbine, e.g. to avoid stall-induced vibrations.

Speed and Power Output ControlPitch Controlled Wind Turbines On a pitch controlled wind turbine the turbine's electronic controller checks the power output of the turbine several times per second. When the power output becomes too high, it sends an order to the blade pitch mechanism which immediately pitches (turns) the rotor blades slightly out of the wind.

Conversely, the blades are turned back into the wind whenever the wind drops again. The pitch mechanism is usually operated using hydraulics.

As a rule of thumb, turbines in wind parks are usually spaced somewhere between 5 and 9 rotor diameters apart in the prevailing wind direction, and between 3 and 5 diameters apart in the direction perpendicular to the prevailing winds.

Wind Parks

Wind Parks

Melancthon I Wind Plant – Spring time

Melancthon I Wind Plant - Summer

Construction

Construction

Wolfe Island Project Description

• 198 MW wind facility on Wolfe Island in Township of Frontenac Islands

• 537,000 MWh/year (enough power for 75,000 households)

• 20 year power purchase agreement (PPA) with the Ontario Power Authority (OPA)

• Originally operated by Canadian Renewable Energy Corp. (CREC), a wholly owned subsidiary of Canadian Hydro Developers, Inc.

• Estimated $410 million capital construction budget

• Obtained all federal, provincial, and municipal permits and approvals (over 90 of them)

• Sited on lands optioned or leased by CREC (10,850 of 30,000 acres)

Overall Project Layout

Wolfe Island Project Description

• 86, Siemens 2.3 MW Mark II wind turbines

• Ancillary facilities include access roads, power lines, and concrete pad-mounted transformers

• Substation and support facilities like an Operations & Maintenance (O&M) building on Wolfe Island

• Connection to Gardiners Rd. Transformer Station behind Home Depot

• 7.9 km of submarine cable to connect Wolfe Island to the mainland

• 4 km of high voltage underground transmission line on the mainland

Wolf Island, Kingston

Siemens Specs

Wolfe Island Wind Project

Why Develop Wind? Advantages

• Rural economic development

– Revenues to rural landowners

– Increase to municipal tax base

– Contributions to the community

– Investment, job creation

• Environmental benefits

– No air pollution, water pollution, GHG emissions, or solid/toxic wastes

• Costs

– Stable long-term electricity pricing - No fuel cost

– Rapid & incremental installation

C/B Henry P. Lading

C/B Henry P. Lading

The tension in the cable at C/B Henry P.

Lading can be calculated from:

T = h x w + H

where: w is the weight of the cable per

unit length in seawater and h is the

water depth.

For the actual cable laying operations,

the normal surface tension in the cable

will depend on the water depth.

C/B Henry P. Lading

Cranes

Cranes

Wolfe Island

Projected Market Growth (2004 estimate)

Actual Cumulative Global Wind PowerInstalled Capacity (Data source: GWEC, Global Wind Statistics 2012

Canadian Wind Power (Data source: http://www.canwea.ca

• Canada is now the ninth largest producer of wind energy in the world with current installed capacity at 6,500 MW – representing about 3 per cent of Canada’s total electricity demand.

• In 2012, wind energy grew by nearly 20 per cent in Canada with the addition of 936 MW – driving over $2 billion in investments and creating 10,500 person-years of employment. (http://www.canwea.ca)

Wind Energy in Ontario https://www.ieso.ca/map/index.html

• Ontario is at the forefront of wind energy in Canada, with more than 1,700 MW of wind generation capacity connected to the province's power grid.

• As system operator, the IESO plays a fundamental role in helping bring wind projects into service and ensuring that Ontario's power system can effectively support increased levels of wind generation.

• An estimated 2,400 megawatts (MW) of embedded solar and wind generation are expected to be in service by Feb 2015.

https://www.ieso.ca/imoweb/marketdata/windpower.asp

Wind FarmCapacity

(MW)Operational

Amaranth I,Township of Melancthon 67.5 Mar. 2006

Kingsbridge I,Huron County 39.6 Mar. 2006

Port Burwell (Erie Shores),Norfolk and Elgin Counties 99 May 2006

Prince I,Sault Ste. Marie District 99 Sep. 2006

Prince II,Sault Ste. Marie District 90 Nov. 2006

Ripley South,Township of Huron-Kinloss 76 Dec. 2007

Port Alma (T1) (Kruger),Port Alma 101.2 Oct. 2008

Amaranth II,Township of Melancthon 132 Nov. 2008

Underwood (Enbridge),Bruce County 181.5 Feb. 2009

Wolfe Island,Township of Frontenac Islands 197.8 Jun. 2009

Port Alma II (T3) (Kruger),Municipality of Chatham-Kent 101 Dec. 2010

Gosfield Wind Project,Town of Kingsville 50 Jan. 2011

Spence Wind Farm (Talbot),Townships of Howard and Oxford

98.9 Mar. 2011

Dillon Wind Centre (Raleigh) 78 Nov. 2011

Greenwich Wind Farm 99 Jan. 2012

Pointe Aux Roches Wind 49 April 2013

Comber Wind Limited Partnership 166 April 2013

Project Capacity (MW)

East Lake St. Clair Wind 99

Conestogo Wind Energy Centre 1 69 2013-Q3

Summerhaven Wind Energy Centre 125 2013-Q3

Erieau Wind 99 2013-Q3

McLean's Mountain Wind Farm 60 2013-Q4

Bow Lake Phase 1 20 2014-Q1

Port Dover and Nanticoke Wind Project 105 2014-Q1

Dufferin Wind Farm 100 2014-Q1

Nigig Power Corporation 300 2014-Q1

Niagara Region Wind Farm 230 2014-Q1

Haldimand Wind Project 150 2014-Q1

South Kent Wind Project 270 2014-Q1

Amherst Island 75 2014-Q2

Goulais Wind Farm 25 2014-Q2

Bow Lake Phase 2 40 2014-Q2

Adelaide Wind Power Project 40 2014-Q3

Bornish Wind Energy Centre 74 2014-Q3

Grand Bend Wind Farm 100 2014-Q3

Grand Valley Wind Farms (Phase 3) 40 2014-Q3

Gunn's Hill Wind Farm 25 2014-Q3

Cedar Point Wind Power Project Phase II 100 2014-Q3

Adelaide Wind Energy Centre 60 2014-Q3

Bluewater Wind Energy Centre 60 2014-Q3

Goshen Wind Energy Centre 102 2014-Q3

Jericho Wind Energy Centre 150 2014-Q3

White Pines Wind Farm 60 2014-Q3

Armow Wind Project 180 2014-Q4

K2 Wind Project 270 2014-Q4