Wind power applications, Grid connected or not? (on photo: The wind turbines, each with a rated power output of 3.2 megawatts (MW) and a hub height of 143 metres, are intended for the Poysdorf-Wilfersdorf III wind farm.) |
- Small, non-grid connected
- Small, grid-connected
- Large, non-grid connected
- Large, grid connected
By small, we mean a size appropriate for an individual to own, up to a few tens of kilowatts. Large refers to utility scale.
Small, Non-Grid Connected
Home wind turbines - designed for ease of use, they are smooth and quiet. |
If
one wants electricity in a location not serviced by a utility, one of
the options is a wind turbine, with batteries to level out supply and
demand. This might be a your home, a remote antenna and transmitter
site, or a Third-World village.
The costs will be high, on the order of $0.50/kWh, but if the total energy usage is small, this might be acceptable.
The
alternatives, photovoltaics, microhydro, and diesel generators, are not
cheap either, so a careful economic study needs to be done for each
situation.
Small, Grid Connected
The small, grid connected turbine is usually not economically feasible. The cost of wind-generated electricity is less because the utility is used for storage rather than a battery bank, but is still not competitive.
In
order for the small, grid connected turbine to have any hope of
financial breakeven, the turbine owner needs to get something close to
the retail price for the wind-generated electricity.
One
way this is done is for the owner to have an arrangement with the
utility called net metering. With this system, the meter runs backward
when the turbine is generating more than the owner is consuming at the
moment.
The owner pays a monthly charge for the wires to his home,
but it is conceivable that the utility will sometimes write a check to
the owner at the end of the month, rather than the other way around.
The utilities do not like this arrangement. They want to buy at wholesale and sell at retail.
They feel it is unfair to be used as a storage system without remuneration.
For
most of the twentieth century, utilities simply refused to connect the
grid to wind turbines. The utility had the right to generate electricity
in a given service territory, and they would not tolerate competition.
Then a law was passed that utilities had to hook up wind turbines and
pay them the avoided cost for energy.
Unless the state mandated
net metering, the utility typically required the installation of a
second meter, one measuring energy consumption by the home and the other
energy production by the turbine.
The owner would pay the regular
retail rate, and the utility would pay their estimate of avoided cost,
usually the fuel cost of some base load generator.
Large, Non-Grid Connected
These
machines would be installed on islands, high mountains or native
villages in the far north where it is virtually impossible to connect to
a large grid. Such places are typically supplied by diesel generators, and have a substantial cost just for the imported fuel.
One or more wind turbines would be installed in parallel with the diesel generators, and act as fuel savers when the wind was blowing.
This concept has been studied carefully and appears to be quite feasible technically.
One would expect the market to develop after a few turbines have been
shown to work for an extended period in hostile environments.
It would be helpful if the diesel maintenance companies would also carry a line of wind turbines
so the people in remote locations would not need to teach another group
of maintenance people about the realities of life at places far away
from the nearest hardware store.
Large, Grid Connected
We
might ask if the utilities should be forced to buy wind-generated
electricity from these small machines at a premium price which reflects
their environmental value.
Many have argued this over the years.
A better question might be whether the small or the large turbines will result in a lower net cost to society.
Given
that we want the environmental benefits of wind generation, should we
get the electricity from the wind with many thousands of individually
owned small turbines, or should 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 on
hospitals, schools, and the like, then it follows that wind turbines
should be as efficient as possible. Economies of scale and costs of
operation and maintenance are such that the small, grid connected
turbine will always need to receive substantially more per kilowatt hour
than the utility-scale turbines in order to break even.
There is obviously a niche market for turbines
that are not connected to the grid, but small, grid connected
turbines will probably not develop a thriving market. Most of the action
will be from the utility-scale machines.
Sizes of these turbines have been increasing rapidly. Turbines with ratings near 1 MW are now common, with prototypes of 2 MW
and more being tested. This is still small compared to the needs of a
utility, so clusters of turbines are placed together to form wind power
plants with total ratings of 10 to 100 MW.
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