6 Principles for Building Cost-Effective
Wind Turbine Generators
Dave Schaetz, Industry Technical Consultant, Alternative Energy, Rockwell Automation
and Steve Ludwig, Safety Programs Manager, Rockwell Automation
Aggressive state level renewable portfolio standards (RPS) are helping to reduce the nation’s
dependence on fossil fuel power generation and driving expansion of the wind industry in the
United States. The states of Colorado and California, for example, are aiming for 30 percent of
their energy to come from renewable energy sources including wind power by 2020. Seeing this
growth potential, wind turbine manufacturers around the world have their sights set on expanding
operations in the U.S. to satisfy the growing demand.
But a wind turbine manufacturer’s path for growth and expansion in new markets is not without
obstacles. Today’s challenges include establishing and managing an effective supply chain,
identifying and complying with relevant standards, improving the safety of workers and equipment
and remaining competitive as customers demand shorter time-to-market cycles.
Rockwell Automation Helps WTG
Manufacturer Manage its Supply Chain
Rockwell Automation helped WTG manufacturers get
through the economic recession by successfully managing
panel shipments. Outsourcing this activity reduced WTG
manufacturers’ financial risk and eliminated the need to have a
dedicated assembly team for the project. Rockwell Automation
also helped WTG manufacturers manage their supply
chain to keep pace with production demands, especially as
manufacturing ramps up again.
For example, when a global
WTG manufacturer enlisted
Rockwell Automation to
build its control panels and
help manage its supply chain
and production worldwide,
Rockwell Automation
reached out leveraging its
best production practices
when building panels.
These include using detailed
and standardized work
instructions, identifying
and labeling raw material,
color coding air screwdrivers to match the color coding of screws
for proper torque settings, using safety and metrics boards
and effective lockout/tag out procedures. The company also
recognized Rockwell Automation for its technical innovation in
the design of a power distribution panel and for excellence in
on-time shipments.
Another challenge is remaining competitive
against other power generation sources.
Levelized Cost of Electricity (LCOE) is the
total lifecycle cost to build and operate a
plant over a period of time, divided by the
total electricity produced by that plant. Wind
turbine manufacturers can use LCOE as a
metric to compare the cost of generating
wind power with other technologies.
Continuously improving the design and
performance of wind turbines can help lower
the cost of electricity generated from wind.
Wind turbine manufacturers building
turbines for offshore applications face
an additional set of unique supply chain
and safety challenges associated with the
extreme, unpredictable environment.
Following are six leading principles for wind
turbine manufacturers who are expanding in
the growing U.S. market by delivering costeffective, safer equipment that is compliant
with appropriate standards.
2 | Building Cost-Effective Wind Turbine Generators
1. Establish a Global Supply Chain with Regional Experience
Wind turbine generator (WTG) manufacturers expanding operations in new markets may
encounter several supply chain challenges, including how to manage costs, inventory and vendor
relationships. When working with a reliable supply chain partner that can provide value add
services, such as electrical engineering, design and manufacturing, manufacturers benefit from one
local point of contact for supply chain considerations, freeing up internal resources to focus on their
core competencies and lowering the total cost to design, develop and deliver new turbines.
A global supplier with broad industry experience also can help the WTG manufacturer implement a
successful production management system based on industry best practices and can help weather
economic downturns and boom/bust cycles that can be detrimental to smaller suppliers that only
focus on one or two industries.
WTG manufacturers partnering with a global supplier can leverage the supplier’s worldwide
manufacturing facilities, providing one point of contact for design, documentation management,
global coordination of assembly, and consistent quality of wiring, assembly and testing. Most
importantly, a global supplier’s distributor network helps ensure product availability and support.
The WTG manufacturer also can standardize component selection and panel design across all
locations worldwide, simplifying spare parts inventory, procurement methods, training and
staffing practices. Reducing the number of control platforms also helps ensure that there is always
a knowledgeable technician available because the manufacturer’s staff only needs training and
familiarity with one platform.
Finally, partnering with an outside vendor for supply chain management allows a WTG
manufacturer to effectively increase its production capacity without increasing its internal
workforce, allowing existing staff and resources to remain focused on the company’s core
expertise – designing the best WTG.
Building Cost-Effective Wind Turbine Generators | 3
2. Outsource Electrical Control Panels
Engineering the control panel is time-consuming and can have a significant impact on system cost
for the WTG design and development process. One alternative to building control panels in house
is for WTG manufacturers to retain the design and documentation responsibilities, but work with
third-party panel builders to streamline the process. As business grows in new markets, working
with multiple panel builders can become quite arduous, often resulting in the need for increased
engineering and supply chain staff resources to coordinate and monitor multiple sources of supply.
A more efficient alternative is for WTG manufacturers to work with a single automation supplier
that can design and build the entire panel – including all the control and power components –
and help standardize component selection and panel design across many locations worldwide.
This single point of contact through design, prototyping and ongoing deliveries can help a WTG
manufacturer increase production capacity without increasing its internal workforce, freeing up
existing resources that would be needed for engineering, procurement, inventory management,
testing, standards compliance and troubleshooting support.
A supplier with a testing/validation lab for environmental cycling and accelerated life testing
gives a WTG manufacturer the opportunity during the design phase to achieve the best possible
control panel design. This may lead to additional benefits such as reducing the panel size,
selecting components that generate less heat, and/or designing an integrated safety system
to help provide safe access to panels during operation. No matter which design strategies are
employed, a testing/validation lab can help a WTG manufacturer optimize the panel layout and
minimize troubleshooting.
By leveraging panel building services from a global supplier, a WTG manufacturer gains standards-compliant, custom, control and electrical distribution panels,
such as the WTG control panel pictured here, while focusing time and internal resources on its core competencies.
4 | Building Cost-Effective Wind Turbine Generators
3. Design for High Availability and Reliability
WTGs are used in extreme onshore and offshore environments. For example, the Tehachapi Pass,
California installation is in an extreme desert environment, and the proposed Cape Wind Nantucket
Sound installation is in the ocean – a potentially corrosive environment. A high level of availability
of the distributed power generation from WTGs is critical in both types of deployments. WTGs and
their equipment must be reliable when deployed in onshore and offshore environments, and spare
parts should be readily available in the event of failure.
In addition, lowering the Operating and Maintenance (O&M) costs during and after the warranty
period is important. Utilizing off-the-shelf components with long life cycles and leveraging a large
network of global support with access to spare parts inventory can help reduce system downtime
if a problem occurs.
Offshore wind turbines are increasingly used in a number
of countries because offshore winds tend to flow at higher
speeds than onshore winds, allowing turbines in offshore
environments to produce more electricity. Much of this
potential energy is near highly populated areas and energy
load centers where energy costs are high and land-based
wind development opportunities are limited.
Logix-XT controllers and Allen-Bradley FLEX I/O-XT™ products from Rockwell Automation
are conformally-coated and designed using hardened components suited for rugged
environments, without the additional installation and energy costs associated with auxiliary
heating and cooling systems.
Offshore turbines have unique technical needs because
weather conditions in offshore environments can be
extreme and fluctuate more often than on land. Many
WTG manufacturers supplying offshore equipment try
to meet design challenges by engineering their own
solutions. These solutions can be susceptible to moisture
and contaminants resulting in short circuits and corrosion
of conductors and solder joints.
A better alternative, however, is to invest in components
specifically designed for these extreme environments and include them as part of a complete
control and information architecture, helping improve product longevity while reducing
integration and installation costs. For example, extreme environment products help to reduce
panel costs and the need for additional heating/cooling equipment, resulting in lower installation
and maintenance costs. Extreme environment products are often conformally coated to provide
environmental and mechanical protection which significantly extends the life of the printed circuits
and electrical components.
Building Cost-Effective Wind Turbine Generators | 5
4. Conduct a Standards and Safety Audit
Safety is a critical element in WTG design and operation. Protecting people is most important,
and WTG manufacturers must also consider protecting the large capital investment in a WTG. The
diameter of wind turbine blades has become significantly larger in recent years, and is now larger
than the wingspan of a Boeing 747 jumbo jet, increasing the potential amount of wind energy each
WTG is capable of producing. In turn, protecting assets becomes increasingly important for wind
turbine manufacturers.
As the diameter of a wind turbine increases so does the potential to increase wind energy production. An outline
of a Boeing 747 jumbo jet is shown here against an off shore WTG to illustrate the size of the blades.
Uncontrollable, hazardous weather
conditions like high wind speeds create
unique safety challenges for wind turbine
manufacturers. For example, the turbine
must be capable of stopping quickly and
safely in the event of high wind speeds
to prevent the turbine from tearing apart.
In addition, WTG safety system designers
are challenged with a mix of high and
low voltages, depending on the section
of the WTG (e.g., tower, nacelle, or hub).
Within each area, there may be low
voltages, high voltages or a combination
of the two. The voltage dictates the
safeguarding mechanisms necessary
to mitigate risks in each area of the WTG
(See Figure 1).
Personnel must be protected against rotating parts in the nacelle and hub, and WTG designers may
need to use physical guarding or special access requirements to stop the WTG from rotating prior
to personnel entering the area. Other examples of effective safeguarding include employing a safespeed monitoring relay to detect over speed of the rotor, vibration monitoring sensors to detect
excess vibration, switches to control the opening of control cabinet doors, and/or medium voltage
switchgear used in the lower portion of the tower to detect and suppress arc flash hazards.
Automation suppliers will continue to validate and test solutions for mitigating arc flash hazards
through new wind turbine power cabinet designs. Continuing to develop arc flash resistant
solutions by leveraging control components will help WTG manufacturers more effectively mitigate
the risks associated with arc flash energy in the future.
6 | Building Cost-Effective Wind Turbine Generators
Performing a safety audit before control system design helps engineers chart the course for an
effective safety solution and evaluate risks early in the development process. This saves critical time
and helps machine builders get their equipment to market faster. In addition, the machine’s end
users gain optimized production, thanks to an automation system that helps operate machinery
and processes in the most efficient way. A safety audit identifies potential hazards and the
required safety control system integrity level, and helps guide the selection of the overall control
architecture to achieve the optimum level of safety.
Where hazards cannot be removed through design, machine builders typically will install a fixed
physical barrier that helps protect users from the hazard. When frequent access to the hazardous
area is required, non-fixed guards are used, such as removable, swinging or sliding doors. In areas
where non-fixed guards are impractical, guarding solutions that monitor the presence of the
operator rather than the status of the gate can be used.
Figure 1 (Source: Rockwell Automation)
Building Cost-Effective Wind Turbine Generators | 7
5. Provide Compliance to Regional Electrical and Safety Standards
As WTG manufacturers expand operations globally, they must adhere to local and regional
standards to help ensure the safety of workers and equipment in those regions. By following
appropriate international standards, WTG manufacturers can streamline production processes
globally, and gain access to customers all over the world. As an added bonus, incorporating
standards into the wind turbine design process can increase productivity and profitability for both
manufacturers and operators of wind turbines.
Some of the newest standards that are reshaping how designers approach wind turbine projects
pertain to safety:
International Organization for Standardization (ISO) 13849-1/2 and International
Electrotechnical Commission (IEC) 62061. These international safety standards were recently
mandated by the European Commission’s Machinery Directive, and issued in part to assist
with the free movement of goods and services across a single European market. They also are
considered among the most rigorous machine safety standards in the world. Wind turbines
fall under the scope of the Machinery Directive, and therefore any WTGs shipped into or out
of Europe must comply with the appropriate standard after the final withdrawal of EN 954-1
in 2011. (See figures 2 and 3.)
Article 2 (a) – fi rst indent
‘machinery’ means:
– an assembly, fi tted with or intended to be fi tted with a drive system other than
directly applied human or animal effort, consisting of linked parts or components, at
least one of which moves, and which are joined together for a specifi c application.
Figure 2 (Source: Guide to application of the Machinery Directive 2006/42/EC 2nd Edition June 2010, pages 28-29)
The moving parts of machinery are powered by a drive system using one or more sources of energy such as
thermal, electric, pneumatic, hydraulic or mechanical energy. The machinery may have a motor using its own
source of energy such as thermal energy or energy provided by a battery. It may be connected to one or
more external sources of energy such as a supply of electricity or compressed air. Machinery may use
mechanical energy supplied by other equipment such as, for example, towed agricultural machinery that is
driven by the power take-off of a tractor, or test beds for motor vehicles that are driven by the vehicles being
tested; machinery may also be powered by natural sources of energy such as wind or water power.
Figure 3 (Source: Guide to application of the Machinery Directive 2006/42/EC 2nd Edition June 2010, pages 28-29)
The international standards add two very important elements to the reliability of the
machine’s safety function: time and risk. These two elements help machine builders take
advantage of a more methodical approach to safety system design.
Both international standards require WTG manufacturers to identify and document the
potential hazards associated with machine operation and the risk levels present to users.
The safety system is then designed to the level of risk associated with the hazards present
on the machine. Because appropriate documentation proves a machine’s level of safety,
designers can better justify a need for a safety system upgrade, and operators can be more
confident in the reliability of a machine’s safety system.
8 | Building Cost-Effective Wind Turbine Generators
Electromagnetic Compatibility (EMC) Directives. EMC management has emerged as a critical
means of improving the reliability and operating life of electronic equipment employed
in WTGs. EMC directives aim to help ensure that all electrical devices in one electrical
environment work properly and safely together. Specifically, the EMC Directive (2004/108/EC)
requires that the electromagnetic disturbance generated by any fixed installation does not
exceed the level above which radio and telecommunications equipment or other equipment
cannot operate as intended. Under this directive, WTGs are considered fixed installations, and
therefore must be built according to the engineering practices outlined in the directive. (See
Figures 4 through 7.)
“Fixed installation” means a particular combination of several types of
Apparatus and, where applicable, other devices, which are assembled,
installed and intended to be used permanently at a predefi ned location.
Figure 4 (Source: Guide for the EMC Directive 2004/108/EC February 8, 2010, page 21)
Examples of fixed installations:
Industrial plants, power plants, power supply networks, telecommunication
networks, cable TV networks, computer networks, airport luggage
handling installations, airport runway lighting installations, automatic
warehouses, skating hall ice rink machinery installations, storm surge
barrier installations (with the control room etc), wind turbine stations, car
assembly plants, water pumping stations, water treatment plants, railway
infrastructures, air conditioning installations.
Figure 5 (Source: Guide for the EMC Directive 2004/108/EC February 8, 2010, page 21)
Owing to their characteristics, fixed installations are not subject to the need
for free movement within the Community. Therefore, they are not subject
to the requirements for CE marking, DoC or for formal EMC assessment
before putting into service. However, fixed installations have to comply
with the protection requirements and other specific requirements (Annex I
of the Directive) which are applicable to them.
Figure 6 (Source: Guide for the EMC Directive 2004/108/EC February 8, 2010, page 42)
ANNEX I
ESSENTIAL REQUIREMENTS REFERRED TO IN ARTICLE 5
1. Protection requirements
Equipment shall be so designed and manufactured, having regard to the state of the art, as to ensure that:
(a) the electromagnetic disturbance generated does not exceed the level above which radio and telecommunications
equipment or other equipment cannot operate as intended.
(b) it has a level of immunity to the electromagnetic disturbance to be expected in its intended use which allows it
to operate without unacceptable degradation of its intended use.
2. Specific requirements for fi xed installations
Installation and intended use of components
A fixed installation shall be installed applying good engineering practices and respecting the information on the
intended use of its components, with a view to meeting the protection requirements set out in Point 1. Those good
engineering practices shall be documented and the documentation shall be held by the person(s) responsible at the
disposal of the relevant national authorities for inspection purposes for as long as the fixed installation is in operation.
Figure 7 (Source: Directive 2004/108/EC of the European Parliament and of the Council of December 15, 2004 on the approximation
of the laws of Member States relating to electromagnetic compatibility and repealing Directive 89/336/EEC, page 8)
Building Cost-Effective Wind Turbine Generators | 9
Product Directives. Many product directives have been issued in Europe as part of an effort
to create a unified European market. Limited to “essential requirements,” which are general
in nature and primarily focus on health protection, these directives are compulsory for any
product put into circulation and so apply to wind turbines and their sub-assemblies.
GL Guideline for the Certification of Wind Turbines (Edition 2010). The latest edition of this
guideline makes specific references to the EN ISO 13849-1: 2006 Functional Safety Standard
and requires that WTG manufacturers conduct a risk assessment to determine the maximum
permitted probability of failure. By providing numerical evidence of the probability of failure,
WTG manufacturers can help justify a customer’s investment in new safety systems. WTG
manufacturers must follow ISO 13849-1: 2006 and IEC 60204-1 to gain GL certification of a
WTG. GL publishes guidelines for certifying WTGs. (See Figure 8.)
Figure 8 (Source: GL Guideline for the Certification of Wind Turbines, July 2010, Figures 2.1.4 “Required risk reduction through protection
functions,” 2.2.3.3 “Safety System,” and 2.3.2.15 and 2.3.2.15.2 “Emergency stop requirements”)
10 | Building Cost-Effective Wind Turbine Generators
Underwriters Laboratories, Inc. (UL) Standards. Large and small WTGs are evaluated
according to UL Subject 6140-1, UL’s “Outline of Investigation for Wind Turbine Generating
Systems.” The systems are evaluated for risk of fire and shock, including safety-related control
system electrical performance and utility grid-interconnect performance for utility interactive
models. While these standards apply in North America, they do not align directly with many of
the European IEC standards, making it difficult for European WTG manufacturers to conform to
standards when expanding to the U.S.
Certification (CE) Markings. Similar to UL Standards in North America, a CE marking denotes a
product’s compliance with European standards. A CE marking symbolizes that the equipment
conforms to the applicable requirements imposed on the manufacturer. WTG manufacturers
need to earn a CE marking on any WTG so it can be shipped throughout Europe.
Tackling the many, often complex, standards can be daunting. WTG manufactures should leverage
the expertise of certified safety consultants from a global supplier to navigate requirements and
design an acceptable safety system.
Building Cost-Effective Wind Turbine Generators | 11
6. Integrate WTG Safety into the Control System Design
to Reduce Complexity
The evolution of safety standards and economic factors are driving the evolution of safety systems
from hardwired to contemporary, highly integrated configurations. Using an integrated platform
for safety and standard control eliminates the need for electromechanical or hardwired controls.
The more designers integrate the standard and safety control functions of a system, the better
the opportunity to reduce equipment redundancies, improve productivity and minimize costs.
See Figure 9 for how standard and safety control systems should interact in a WTG.
This integrated control functionality reduces the number of unique components in use as part
of the WTG control system, which in turn reduces inventory costs, as well as maintenance team
training requirements. End users also benefit from less waste with fewer parts to maintain and
replace throughout the WTG life cycle. In addition, integrated control systems, having broader
intelligence regarding machine operation and status, reduce nuisance shutdowns and prolonged
restarts, further improving machine efficiency and productivity.
Figure 9 (Source: Rockwell Automation and GL Edition 2010)
Safety controllers provide this integrated control functionality and offer significant benefits in
multistep shutdown or ramp-down sequences because they provide the necessary logic through
software rather than the hard-wired logic of relays. An integrated safety controller is an ideal
solution for any application requiring advanced functionality, such as zone control. Being able
to monitor and control access to what is active on each level of the WTG is critical due to the size
and height of the decks within a WTG tower design. With properly designed safety controls and
guarding, designers reduce access time, helping make machines safe and efficient.
Along with eliminating the need for a separate safety controller, integrated safety systems also
use a single programming software package. This can eliminate the need to write and coordinate
multiple programs on different controllers, which in turn can simplify application programming and
help reduce training and support costs. See Figure 10 for an illustration of how standard and safety
functions are integrated into a single control solution.
Figure 10 (Source: Rockwell Automation) An Allen-Bradley GuardLogix PAC from Rockwell Automation incorporates
standard and safety control in one controller.
Safe-speed control solutions provide a great example of effective control integration. With
safe-speed control, safety input devices, such as guard-locking switches and emergency stop
pushbuttons, connect directly to the speed-monitoring core of the control solution. This eliminates
the need for a separate, dedicated safety controller. Extending use across multiple platforms, safespeed control solutions help reduce overall system cost and improve flexibility because they allow
operators to perform maintenance and other tasks while a machine is in motion. Safe-speed control
also helps increase uptime and decrease energy costs because a machine need not be completely
shut down and then restarted.
Networking offers another way to integrate safety and standard controls. The introduction of
networks to industrial environments helps increase productivity, reduce wiring and installation,
improve diagnostics and ease access to facility data. Using an existing network to include safety
information extends those same benefits, allowing seamless communication of the complete
automation process on one standard network with one set of hardware and wiring. Diagnostics from
smart devices that are networked together also can simplify designs and reduce integration costs.
On the Horizon
Thanks to advancements in technology and globalization of safety standards, WTG manufacturers
can expand to new markets and help customers improve worker safety and protect equipment
and assets. By enlisting the help of global suppliers, WTG manufacturers can provide a smooth
expansion to new markets and continue growing as the wind energy industry expands.
Allen-Bradley, FLEX I/O-XT and GuardLogix are trademarks of Rockwell Automation, Inc.
Trademarks not belonging to Rockwell Automation are property of their respective companies.
Publication OEM-WP010A-EN-P – September 2011
Copyright ©2011 Rockwell Automation, Inc. All Rights Reserved. Printed in USA.