Do building integrated wind turbines actually work?
The integrated building
turbines are definitely one of the emerging technologies in harnessing the wind
energy. But there have been various discrepancies in the performance of the
building integrated wind turbines. There is no question that they do make a green
statement. But do they actually do what they say?
(Above: Largest Building Integrated Power System Installed in Oklahoma
City. US)
One of the biggest challenges
of the turbines has been the air turbulence. The wind turbines often work
efficiently only when the airflow is steady or also known as laminar wind.
According to the American Wind Energy Association (AWEA), although it is pretty
windy on the roof, it is more turbulent than steady wind. “A common rule is to elevate a wind turbine at least 30 feet (9
m) above anything within a 500-foot (150 m) radius, including the building
itself.”(Stimmel)
Various surveys were conducted
to analyze the performance of the building integrated wind turbines. These
surveys projected that only those wind turbines mounted high-rise apartment
buildings were able to generate electricity close to the projected output.
Moreover these turbines were switched off for most period of the survey because
of the complaints from the residents about the noise created by the turbines.
If the turbines are installed at a greater height away from the turbulent flows
and into the laminar winds, the building is subjected to various stresses which
may create substantial problems.
Although there have been an
increasing number of installations of the wind turbines throughout the North
American continent, obtaining the desired performance and the expected output
has been an issue. Manufacturers of these systems do not reveal such data.
Hence the actual production has been worse than expected.
The greatest barrier to
building integrated wind energy is the economics. The large free standing wind
turbines provide the least expensive renewable electricity today, small wind
turbines are far less cost effective and when small turbines are put on the
buildings, the costs increase while the production decreases. AeroVironment
installations have been running at $6,500 - $9,000 per kW, which is fairly
close to photo voltaic installations. According to a study
conducted by the Lawrence Berkeley National Laboratory, the wind
system will deliver 750-1500 kWh annually per kilowatt of rated capacity. When
the performance is factored it is found that the photo voltaic system delivers
closer to its rated output on a building than the wind turbines, also the
maintenance costs for the photo voltaic installation is comparatively less. According to Paul Gipe, a leading
advocate of wind power for 30 years and author of numerous books on the topic,
if you’re looking to put renewable energy on buildings, “there’s nothing better
than photo voltaic.”
(Above: This Wind side turbine is being tested by Madison Gas and Electric is nominally rated at 10 kW AC but has never produced more than 600 watts. It is installed at a height that might be typical for a rooftop application)
Hence installation of wind
turbines makes sense only if done on a larger scale. However, the cost
effective wind turbines are too large for the building structure. So far it can
be said that wind energy can be harnessed effectively for the large free
standing turbines .The small integrated wind turbines provide electricity that
is much more expensive than the photo voltaic installations.
Wind turbines have always seemed like a clever idea in areas, that have plenty of space and fewer obstructions such as wind farms but i have rarely ever heard of installing them on buildings. Looking at some of the measurements you included in your blog, such as the 30 feet above anything within a 500 foot radius, how do they address mounting the turbine on structure? It seems that the wind load in combination with the heavy head of the turbine, that it make would be hard for a structure to support the load. Just wondering if you ran across any details or practices in your reading.
ReplyDeleteThe wind turbines have been used extensively on wind farms for generating electricity. The same concept was integrated with the design of a building and it was first implemented by a South African Architect Shaun Killa in the construction of The Bahrain World Trade Center, Bahrain, UAE. (http://www.youtube.com/watch?v=iRKkxjotEjk )
DeleteI haven’t exactly come across any specific data as to how they address the construction of the wind turbines. But, the height to which the turbines have to be mounted is decided depending upon the laminar flow of wind. Usually the flow of wind on the roof is pretty turbulent and the turbines must extend beyond this turbulent flow so that it operates in a laminar wind flow. Hence, an approximate minimum height of 30 feet above the structure is recommended for the turbines. This height may vary for different areas.
As regards to the structural design, the building is subjected to the various loads, as you mentioned the wind load and dead load of the wind turbine. Also, at greater heights the supports on which the turbines are mounted are susceptible to resonance due to stronger currents. As a solution to this the building structure as well as the turbine supports is designed to be more structurally rigid. These wind loads (usually obtained from regional airports) and the dead loads are incorporated with the structural design in the design phase.
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ReplyDeleteNeed to include some illustrations and hyperlinks to make your blog interesting to others so they will want to read it. Also proof the blog before publishing it.. you had a lot of different font sizes in this blog.
ReplyDelete