Environmental Engineering Reference
In-Depth Information
large-, medium-,
and
small-scale
horizontal-axis wind turbines (HAWTs), and also reviews
vertical-axis wind turbines (VAWTs).
Wind power applications described include
wind power stations
delivering electricity
on utility grids,
distributed (dispersed) turbines
on utility grids, turbines on
isolated and/or
small electrical grid systems
, and
stand-alone units
for mechanical and electrical power.
Trends in cost of energy (COE) from wind systems in various applications are also discussed.
Operation and maintenance
(O&M) requirements for current systems are included that re-
flect the commercial experience, including typical maintenance scenarios, associated costs,
and trends within the industry.
The development of current wind systems did not occur in a vacuum. This chapter
concludes with material that describes the
social, business, and regulatory environment
that
led to the development of the current wind power industry and provides the past, current,
and future
cost goals
for commercial wind turbines. These nontechnical factors strongly
affect the present wind power industry and the development and deployment of future wind
turbines and applications.
Wind turbines today have an established reputation as practical and reliable systems with
widespread use throughout the world. Examples of wind turbines in commercial service are
pictured in Appendix E. The vast majority of wind turbines have been installed on land. In the
past few years some wind turbine systems have been installed in waters offshore to capture
higher wind speeds and to locate near energy needs such as population centers.
For remote, unattended locations,
battery chargers
employing highly reliable rotor control
methods are selected. If power is required to supplement the needs of homes or small business-
es,
small alternating current (AC) units
with outputs up to 0 kW are the machines of choice.
For farms and agricultural applications where grid interruptions are common, multi-unit
applications with turbines up to abut 25 kW, can provide standby AC power provided there
are batteries and a
direct current
(DC)/AC inverter
are available. An engine-driven generator
can also be used to set line voltage and frequency. Operating in this mode is mandatory to
disconnect from the grid for safety reasons and to prevent frequency synchronization issues
when power is restored. In Europe it is common for farmers, individually or in small groups,
to purchase several
medium-scale
systems ranging from 00 up to ,000 kW that are installed
in clusters that are producing farmstead power but are also sending electricity to the grid.
Clusters of small- to medium-scale turbines are attractive to be used as fuel-savers in
mini-
grids
in isolated communities. In these applications isolated communities have
continuous duty
diesel engine-driven generators providing power day and night serving electrical loads of 0 to
50 MW. But fuel cost and delivery can make wind plants desirable for such applications.
Finally, the largest market is for large-scale multi-unit wind power stations containing
multi-megawatt
machines with rotor diameters up to 00 m and larger, providing bulk elec-
tric power to utility grids. Wind power stations are mainly deployed in North America and
Europe, but applications in developing countries will become critically important as their
appetite for electricity increases and indigenous wind resources are available.
The HAWT configuration continues to dominate wind power production, as it has for most
of the modern era. Since the interconnection of wind turbines to utilities became their principal
application during the 980s and continues to be so today, the average size of wind turbines has
grown. In the United States, many small machine designs have simply disappeared as manu-
facturers have scaled them up into the medium-size range. However, several small turbines are
being mass produced with more than 9,000 units sold in 2007 alone, adding 9.7 MW of new
capacity and bringing the total small-turbine capacity to more than 55 MW.
Scale Classifications
For purposes of this chapter, wind turbines are classified as shown in Table 4-, accord-
ing to their diameters and/or their rated powers. This table follows the terminology used in the
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