Doug,
The Danes have done a good job with wind, but it was not
as well planned as many now want to describe it.
The Danish wind industry grow out of a crisis and the heavy
design was natural. It was built as alternative job creation for
a ship building industry in a downward spiral.
Hakan
At 11:49 PM 1/19/2005, you wrote:
Greg, I'm not exactly sure what you're driving at here.
It is not the case that small wind turbines generally use lower windspeeds
than large ones. In any case there is relatively little energy in the
lower windspeeds. Remember that power in the wind varies as the cube of
the windspeed, as well as with air dendity. And windspeed is very
sensitive to location as well as height above ground (and obstacles).
The design of a wind turbine for a particular windspeed depends mostly on
the local wind regime, not the size of the turbine.
If we have a grid then we are going to need multiple wind turbines on just
about any grid, so there is no argument for few turbines. Multiple
turbines in different locations even a few hundred metres apart are very
helpful in smoothing out wind power delivered.
For increasing the availability of wind power, we need turbines
distributed over a few hundred miles/kilometers. This effect is useful
but we still need storage or alternative sources of electricity.
There is a good graph on page 674 of the second (2000) edition of Bent
Sorensen's "Renewable Energy" (Academic Press). It's also in the first
edition at a different page number.
Storage for small turbines usually employs lead-acid batteries at present.
Other battery types are possible including "flow batteries" with fuel cell
type membrane technology and cycle efficiencies of 70-85%. Where variable
stream flows are tolerable, hydro power can be integrated with wind.
Compressed air storage with gas turbines is promising where natural gas is
available; perhaps ultimately with hydrogen.
Catalytic production of hydrogen with solar heat looks promising (see
http://www.shec-labs.com ). This suggests that electrolytic production of
hydrogen from wind power may be useful for storage if we are going to have
hydrogen produced by solar power.
In most places in North America, most of the wind energy comes in winter,
so integration of solar and wind energy is obvious. For stationary
applications storage of hydrogen in caverns under moderate pressure may
not be too expensive, especially when waste heat of combined cycle gas
turbines and fuel cells can be used for heating water, and in winter,
buildings.
I don't think the notion of the high-tech energy-independent household is
practical, at least where wind energy is concerned, and in areas with grid
access. For a long time to come, transmission will be cheaper than
storage. In unusually favoured ares wind turbines may be widespread, but
in general wind energy like retail sales is a matter of
"location, location, location". Solar energy is a different matter.
Bear in mind that a nuclear-family household with investment apportioned
rationally between efficiency and supply would need wind electric
generating rated capacity of 3-10 kilowatts. However I don't think
that nuclear-family households will be the way of the future.
You might think in terms of the "traditional" Danish pattern of
individual local investors or cooperatives putting up one or a few
*efficiently sized* turbines to supply themselves and their neighbours;
with "storage" in the grid supplied by other wind turbines elsewhere,
thermal power, and power exchanged with the Norwegian hydro system.
This is made possible by Danish law which requires that wind electricity
of the requisite quality must be paid for by the grid companies at a price
which includes the avoided health and environmental costs of burning
fossil fuels (coal in the Danish case).
It seems that the greatest efficiency in the use of materials comes at a
moderate size of turbine. It may be that as the price of energy and
mineral resources goes up the most economical size of wind turbine will
drop, but I don't expect that to happen for some time. Wooden blades for
example can be used on quite large turbines.
Early in the development of industrial wind turbines there was a notable
divergence between American designers influenced by aerospace practice who
emphasized light weight too much and reliability not enough, and Danish
designers employed by farm equipment manufacturers who entered the
wind turbine business, who were not afraid of weight but aimed at
durability, reliability and low cost. The Danes turned out to be
right. I think we may assume that low life cycle cost reflects overall
resource consumption better than turbine and generator (nacelle) weight.
The design of wind turbines including small ones is *very* demanding.
The wind is a very difficult environment for a rotating machine on a light
mounting. The economics of small wind turbines need mass production to
spread the cost of engineering over a long production run, as well as to
lower production costs. One of the keys to the rise of the Danish industry
was the early devlopment of a cooperative association of Danish wind turbine
operators, who published statistics on the operating results; electricity
production, reliability, cost, for the various makes and models; backed
up by the Danish government's Risoe research station. One could say that
the efficient functioning of a market for Danish wind turbines was enabled
by a cooperative, so that competition occurred among engineers,
technicians, and manufacturing teams instead of among promoters and
advertising copywriters. Market theory states that "efficient" markets
require complete, cost-free information available to (and, it is implied,
fully used by) both buyer and seller - among other things.
For more information on wind energy you might look at
http://www.windpower.dk
http://www.scoraigwind.co.uk
http://www.wind-works.org
http://yahoogroups.com/awea-wind-home/
http://yahoogroups.com/awea-smallwind
http://www.awea.org and other national associations.
I found Paul Gipe's book "Wind Energy Comes of Age" (Wiley, 1995)
especially enlightening.
With apologies for taking up so much space on a not strictly biofuel
topic.
Doug Woodard
St. Catharines, Ontario
On Tue, 18 Jan 2005, Greg Harbican wrote:
> I don't want to cause an argument, but, is that a flat cost in money or
over
> all cost ( environmental cost to produce the materials to make it, the
> economic and environmental cost to put the materials together and build the
> turbine ).
>
> It just seams to me that smaller turbines while in the long run may cost
> more to maintain for a given kilowatt, might be of lower over all cost
> because they are more adaptable in materials used in building them, take
> advantage of lower winds speeds, how much they affect the environment and
> similar factors?
>
> Is it better economically to have:
>
> 1 300 kw turbine that uses 78 % of the available wind, with a 98%
mechanical
> availability?
> 2 150 kw turbines that uses 80 % of the available winds ( because they can
> use slower winds speeds ), each with 98% mechanical availability ( if
one is
> down for repairs then you still have 1/2 of your power generation
> potential )?
> 3 100 kw turbines that uses 82 % of available winds, again, each with 98%
> mechanical availability ( if one is down for repairs then you still
have 2/3
> of your maximum generation potential )?
> or
> 4 75 kw turbines that uses 84% of available winds, again with a 98%
> mechanical availability ( if one is down, then you still have 3/4 of you
> maximum generation potential )?
>
> Personally, I would think that as far as cost's are concerned, it would be
> better to have 4 smaller turbines, than 1 large turbine that 2% of the time
> is not bringing in any revenue. Granted long term cost is going to be
> higher, but, you get that back, in reliability, and the ability to bring in
> revenue when the wind is blowing.
>
> Maybe I am just looking at things differently.
>
> Greg H.
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