8/12/2019 Electrical-Engineering-portal.com-Wind Power Applications Grid Connected or Not

http://slidepdf.com/reader/full/electrical-engineering-portalcom-wind-power-applications-grid-connected-or 1/4

electrical-engineering-portal.comhttp://electrical-engineering-portal.com /wind-power-applications- grid-connected-or-no t?utm_source=Technical+Articles&utm_campaign=2cc7961649-RSS_EMAIL_CAMPAIGN&utm_medium=email

Wind p ower app lications, Grid co nnected or no t? (on photo: The wind turbines, each with a rated p ower output of 3.2megawatts (MW) and a hub height of 143 metres, are intended for the Poysdorf-Wilfersdorf III wind farm in the north-east of

Aus tri a.)

by Edvard

Wind power applications, Grid connected or not?

Thereareperhapsfour distinct

categories o f wind power which sho uld be discussed.

These are:

By small, we mean a size appropriate f or an individual to o wn, up to a f ew tens of kilowatt s. Large refers toutility scale.

Small, Non-Grid Connected

8/12/2019 Electrical-Engineering-portal.com-Wind Power Applications Grid Connected or Not

http://slidepdf.com/reader/full/electrical-engineering-portalcom-wind-power-applications-grid-connected-or 2/4

Home wind turbines - des igned for ease o f use, they are smoo th and quiet.

Small wind turbine - Grid connected (Horizo ntal-axisturbine d esig ned and installed in San Francisco)

If one wants electricity in a locat ion notserviced by a utility, one o f the options isa wind turbine, with bat teries t o level outsupply and demand. This might be a your home, a remot e antenna and transmitter site, o r a Third-World village.

The costs will be high, on the order of

$0.50/kWh , but if the to tal energy usageis small, this might be acceptable.

The alternatives, photovoltaics,microhydro, and diesel generators, are no tcheap either, so a careful economic st udyneeds to be done f or each situation.

Go to top ↑

Small, Grid Connected

The small, grid connected turbine is usually not economically feasible . The cost of wind-generatedelectricity is less because the utility is used f or s to ragerather than a batt ery bank, but is s till not competitive.

In order f or t he small, grid connected turbine to have anyhope o f f inancial breakeven, the turbine owner needs t oget so mething close to t he retail price f or t he wind-generated electricity.

One way this is done is for t he owner to have anarrangement with the utility called net metering. With thissyst em, the meter runs backward when the turbine isgenerating more t han the owner is consuming at t hemoment.

The owner pays a monthly charge for t he wires to hishome, but it is conceivable that t he utility will sometimeswrite a check to t he owner at t he end of the month, rather than the o ther way around.

The utilities do not like this arrangement. They want t o buy at wholesale and sell at ret ail.

They f eel it is unf air to be used as a st orage system without remuneration.

For mos t o f the twentieth century, utilities simply ref used to connect the grid to wind turbines. The utility hadthe right t o generate electricity in a given service territo ry, and they would not to lerate co mpetition. Then a lawwas passed that ut ilities had to hoo k up wind turbines and pay them the avoided cos t f or energy.

Unless the s tat e mandated net metering, the utility t ypically required the installation o f a second meter, onemeasuring energy consumption by the home and the o ther energy production by t he turbine.

8/12/2019 Electrical-Engineering-portal.com-Wind Power Applications Grid Connected or Not

http://slidepdf.com/reader/full/electrical-engineering-portalcom-wind-power-applications-grid-connected-or 3/4

Large, non-grid connecte d wind turbines installed on mountain

The owner would pay the regular retail rate, and the ut ility would pay their est imate o f avoided cos t, usually thef uel cost of some base load generator.

The owner might pay $0.08 to $0.15 per kWh , and receive $0.02 per kWh f or t he wind-generatedelectricity. This was f ar f rom enough to eco-nomically just ify a wind turbine, and had the ef f ect of killing thesmall wind turbine business.

Go to top ↑

Large, Non-Grid Connected

These

machines would be installed on islands, high mountains o r native villages in the f ar nort h where it isvirtually impossible to connect to a large grid. Such places are typically supplied by diesel generators , and havea substantial cost just f or t he imported f uel.

One or more wind turbines would be installed in parallel with the diesel generators , and act as f uel saverswhen the wind was blowing.

This concept has been s tudied caref ully and appears to be quite feasible technically . One would expect themarket to develop af ter a f ew turbines have been shown to work for an extended period inhostile environments.

It would be helpf ul if the diesel maintenance companies would also carry a line of wind turbines so the peoplein remote locations would not need to teach another group of maintenance people about the realities of life atplaces f ar away f rom the nearest hardware sto re.

Go to top ↑

Large, Grid Connected

8/12/2019 Electrical-Engineering-portal.com-Wind Power Applications Grid Connected or Not

http://slidepdf.com/reader/full/electrical-engineering-portalcom-wind-power-applications-grid-connected-or 4/4

In Schlalach-Mühlenfließ, a small town in the German region of Brandenburg, 16 gigantic wind turbines stretch into the air.Every tower has huge, ro tating b lades and a height of clo se to 180 meters.

Wemightask if theutilitiesshouldbeforced

to buywind-

generated electricity f rom thes e small machines at a premium price which ref lects t heir environmental value.

Many have argued this over the years.

A bet ter question might be whether t he small or t he large turbines will result in a lower net cost to so ciety.

Given that we want t he environmental benef its o f wind generation, should we get the electricity f rom the windwith many thousands of individually owned small turbines, o r sho uld we use a much smaller number of utility-scale machines?

If we could make the argument that a dollar spent on wind turbines is a dollar not spent o n hospitals, schoo ls,and the like, then it f ollows that wind turbines should be as ef f icient as poss ible. Econo mies of scale andcosts of operat ion and maintenance are such that the s mall, grid connected t urbine will always need to receivesubst antially more per kilowatt hour than the utility-scale turbines in order to break even.

There is o bvious ly a niche market for turbines that are not connected to the grid, but small, grid connectedturbines will probably not develop a thriving market. Mos t of the action will be f rom the ut ility-scale machines.

Sizes o f these turbines have been increasing rapidly. Turbines with rat ings near 1 MW are now common, withprotot ypes of 2 MW and more being test ed. This is s till small compared to the needs o f a utility, so clust ers o f

turbines are placed to gether to f orm wind power plants with to tal ratings o f 10 to 100 MW .

Go to top ↑

Resource: Electric Power Generation: Non-Conventional Methods – Saifur Rahman Virginia Tech