A Brief History of Small Wind
Electric Turbines
The
first windmill for
electricity production was built in Cleveland, Ohio by Charles Brush in
1888.
By 1908 there were 72 wind generators in
use, ranging in size from 5 kW to 25 kW.
By the 1930's and
1940's, hundreds of
thousands of wind electric turbines had been built in the U.S.
and
were typically used to provide electricity to farms far beyond the
reach of power lines. These
machines were in the 200 to 3,000
watt range and were configured to charge storage batteries which
operated radio receivers and a few light bulbs.
By the early 1950's,
the Rural
Electrification Administration (REA) had extended the utility grid to
the majority of American households and the availability of low cost
electricity eliminated the market
for these
machines.
The energy woes of the
1970's helped
resurrect the small wind turbine industry. Fueled in large part
by tax
credits and the federal PURPA act, over 4500 small grid-tied wind
systems were installed
between 1976 and 1985.
In 1985 oil prices dropped, the tax credits expired and the small wind
industry was in limbo once again.
Today, the high cost
of energy and the
specter of another energy crisis is helping to increase public
awareness of and demand for renewable energy solutions. The small wind
industry is back!
Installing a Wind Turbine (or any
renewable energy system) is a great way for us to
practice our own personal energy policy and help
improve our little corner of the world!
The Definition of a Small Wind Turbine
The
generally accepted definition is 100 kilowatts of rated power or less.
However, as commercial
turbine sizes
increase, the definition of small wind is likely to increase as well.
The following
chart
helps put it all into perspective.
This
chart also illustrates the relationship between rotor diameter and
rated
power. Rotor diameter (as
opposed to manufacturer's claims) is rapidly becoming the standard for
determining a turbine's rated power.
How
Small Wind Electric Turbines
Work
•Wind is created by uneven heating of
the earth’s surface by the sun. Wind
energy is kinetic energy
(mass
and momentum) so indirectly it's
all solar
energy!
The wind turbine converts
the wind's kinetic energy into electricity.
Most modern small wind
turbines use a permanent magnet alternator or induction generator
to accomplish this. Once the electricity leaves the turbine via the "down
tower wiring,"
where it goes next is determined by the
type of system it's connected to.
For
a residential grid tie system,
the electricity is processed to make it compatible with utility
standards, then fed into the household wiring at the breaker panel.
This point of interconnection is
where the
power from the turbine "blends" with the utility power. From there it
will flow into the
home or out onto the utility grid, depending on the following
conditions.
During periods
of low or no wind, power is being purchased from the utility. As the
wind speed
increases, the turbine power production increases, reducing
the amount power purchased from the utility.
When the turbine output
surpasses the home's electrical needs, the excess flows out to the
utility grid
and a credit is generated. This credit system is known as
net metering and more in-depth information
may be found on our Net Metering
Page.
For more information on the NY State wind incentive program please
visit NYSERDA
For turbines used in off-grid homes
the electricity flows to a controller, where it's converted to DC
(direct current),
regulated and used to charge batteries. These batteries are used to
power one or
more inverters, which in
turn provide standard 120/ 240
volt AC current for the home's appliances.
For a more in-depth
explanation
of how off-grid systems work, please visit our Backup
Power Page.
Turbines used for water
pumping:
Although wind electric water pumping systems are in use
all over
the world, we have not found them
to be cost-effective for
most agricultural applications in NY and PA.
The wind in our region is
at it's lowest
when you need the water most, just the opposite of solar
energy.
Reliability
New
York is notorious for turbulent wind sites that will chew up and spit
out poorly designed wind
turbines. Those of you that know me, know I tend to
be a bit intense on this subject, so I'll try to
keep it short!
* Not all turbines are created equal! They are man made and have moving
parts…buyer beware!
* Do your homework!! Just as you would if buying a car or home appliance
*Heavy metal is a
good thing! A heavy machine will typically outlast it’s lightweight
counterparts
*Slow is also a good thing! Low RPM machines have
significantly less maintenance and longer life
than low cost/ high rpm turbines. 175-500 rpm good…500+ not so good
(and noisy too!)
*You get what you pay for! Low cost turbines are
great for small cabins and hobbyists. What do you
want... expensive lawn art or a reliable, cost-effective, long term
investment?
Maintenance
* Low maintenance does not mean no maintenance
* Inspection (and
possibly maintenance) every 1-2 years. Inspection includes mechanical
and
electrical connections, checking for corrosion, guy wire
tensionioning, inspect blades/replace
leading-edge tape, etc.
* Beyond 10 years blade or bearing replacement may
be needed
* Typical annual maintenance costs are typically 1%
to 2% of installed cost
* Lifetimes of 10 to 20 years and more with the appropriate turbine, proper
installation and regular maintenance
“A wind turbine may see as many
operating hours in one year as an automobile will in 200,000 miles!”
Wind Turbine Fuel
It's amazing how many people will pay
good money for a small wind turbine and then install it on a
short tower where it's starved for wind. You wouldn't starve an
automobile for fuel and expect
it to
perform properly, so why expect that from your wind turbine??
It's actually quite simple:
wind
speed increases with height. Wind speed is affected by friction
against
the earth's surface, so the higher up the turbine is, the
more fuel it has to work with. It's not uncommon
to see a 5-7% increase in energy
production for every 20 feet of additional tower height above
80 feet. And the
additional cost for that extra height is only about 2 to 3%.
Over the life of the system,
that adds up to a lot more energy produced and a much better return on
your investment.
FYI: Betz's law states that the energy content of the wind varies with
the cube of the average wind speed.
Simply
put: double the wind speed and you increase the energy 8 times. Tower
height is critical!!
Siting
Another
reason to avoid short towers is turbulence. When wind
encounters obstructions such as
trees and buildings it becomes
turbulent. As this illustration shows, the turbulent zone extends well
beyond the obstruction. A turbine installed within this zone will give
poor performance. The turbulence
will also stress the machine and tower, increasing the maintenance and
decreasing the turbine's lifespan.
Site a turbine a minimum of
30
feet higher than obstructions within 500 feet, even higher
if those obstructions are young trees!
"Trees
will grow but the
tower never will!” Mick
Sagrillo
The
3 most common tower types used for small wind turbines are the following
Guyed
Lattice
Tilt Up
Self
Supporting or SSV
The guyed lattice tower
is the most economical for mid-sized turbines (5-10KW). This tower is
shipped
in sections, assembled on-site, turbine and wiring installed and a
crane used to lift the completed
assembly into place. The 100' and 120' versions are the most popular.
The tilt up tower is
typically used on smaller turbines up to 5KW or so. And yes, there are
larger
turbines on tilt ups out there, but they are not very cost-effective
option. This type of tower usually
consists of pipe or tube held together with couplers, with guys at each
coupler.
A gin pole provides the leverage for raising/ lowering via a
tow cable and pulley system.
The tow cable is pulled with a winch or tow vehicle.
The self supporting 3
legged tower is the industry standard for turbines 10KW and up.
This
tower is assembled on-site and placed onto it's foundation by a crane.
Of the 3 tower types shown here, this is
the most expensive. When used with the larger turbines, it is still a
cost-effective option.
Zoning and
Permitting
This subject is probably the
most complicated of all. NY State is a home rule state with no
standardized zoning ordinances. Each municipality has it's own unique
zoning and land use regulations.
The first step in any small wind project should be to find out if your
town has any wind specific ordinances, tower height
restrictions or
anything else which might impact your project. A large number of
potential
wind projects stall at this point due to zoning and permitting barriers.
At some point I will post more detailed information on this subject,
but right now I have other walls to
beat my head against!
Thanks
for dropping by!
This
website was created with solar and wind power!
© 2012 By Roy
Butler
