By Edwin L. Aguirre
Wind energy capacity continues to grow worldwide each year. In 2021, the global wind industry added 93.6 gigawatts of new capacity, according to a recent report from the Global Wind Energy Council. This brings the total installed wind capacity to 837 GW, which is helping the world avoid more than 1.2 billion tons of carbon dioxide annually – equivalent to the yearly carbon emissions of South America, the report states.
In the United States, more than 70,800 wind turbines are currently operated by utility companies, according to the U.S. Geological Survey. A growing challenge for commercial turbine operators is the upkeep of the blades, which are made of fiberglass composite and can measure hundreds of feet in length and weigh several tons. Cracks or holes in the blades’ edges can cause the turbine to fail, disrupting power generation.
“As global demand for clean, renewable energy increases, the need to monitor wind turbine blades for structural integrity and damage is becoming even more crucial,” says Mechanical and Industrial Engineering Assoc. Prof. Murat Inalpolat of UMass Lowell’s Structural Dynamics and Acoustic Systems Laboratory and Center for Energy Innovation.
Inalpolat and his research team are developing and implementing, for the first time, a continuous, sound-based sensor system for monitoring the structural health and integrity of offshore wind turbine blades, which can span 450 feet or more.
“No such system exists before for monitoring the operational health of full-scale offshore wind turbine blades, which are much larger and heavier than onshore turbine blades and therefore entail more risks in their operation,” says Inalpolat.
“These turbines are located far from the coast, so remote monitoring technologies will be vital. For the first time, we will be able to collect health data for a relatively long duration, which will help wind farm operators and utility companies in keeping the turbines operable, safe and reliable,” he says.
Inalpolat’s research is funded by an $800,000 grant from the National Offshore Wind Research and Development Consortium (NOWRDC), a nonprofit organization collaborating with industry on R&D activities to reduce the cost of offshore wind energy in the U.S. while maximizing the economic and social benefits. It is one of six new projects that were awarded a total of $3.4 million by the consortium this year to improve supply chain efficiency for turbine components and asset monitoring and inspection of turbine infrastructure.
“It was an extraordinarily competitive grant program,” says Inalpolat. “UMass Lowell is the only university selected for the consortium’s specific turbine operations and maintenance awards.”
The UMass Lowell project aims to reduce operational costs of offshore wind farms. In addition to UML, the other awardees include the Electric Power Research Institute, GE Renewable Energy, the National Renewable Energy Laboratory, GE Research and Dive Technologies. They will support NOWRDC’s goal of generating 30 GW of U.S. offshore wind power by 2030.
The Sound of Damage
Inalpolat’s project builds on earlier research that he led and that was supported by a $1.4 million grant from the U.S. Department of Energy.
“Our acoustic monitoring system is low-cost, reliable and robust, and it can be installed on both new and existing offshore wind turbines,” says Inalpolat. “There is no other technology in today’s market that can monitor the condition and safety of turbine blades while they are operating.”
He says their acoustic system is an integral blade monitoring system that fuses real-time information from internal and external blade sensors and can identify different, multiple damages and operational deficiency scenarios.
Because of continually varying operating conditions, all blades will experience splits, cracks or holes along their edges that are currently not detectable except by visual inspection or after a blade has failed. Inalpolat’s research will help determine in real time if and when blade damage occurs. By catching the damage in time, the team hopes to prevent it from progressing into a catastrophic failure of the blade, allowing the operator to schedule repair or maintenance work at an appropriate time and minimize the turbine’s downtime.
Inalpolat’s system will use inexpensive, low-maintenance wireless microphones mounted inside the blade’s structural cavity to passively monitor blade damage, while a single down-tower sensor will help maintain regular surveillance of extraneous noise sources as well as blade tip damage.
“Blade damage will manifest itself in changes to the cavity’s frequency response functions and anomalies in sound level and frequency generated by and across the composite structure. It’s a fundamentally simple but effective idea,” he says.
Inalpolat’s external collaborators include the Electric Power Research Institute and Dominion Energy.
The monitoring system will be applied initially on one of the two 6-megawatt turbines of Dominion Energy’s Coastal Virginia Offshore Wind pilot project, which is currently under construction 27 miles from the shores of Virginia Beach. When fully completed in 2026, Dominion’s commercial-scale wind farm will feature a total of 176 turbines, capable of delivering up to 2.6 GW of zero-carbon energy to as many as 660,000 customers at peak output, according to the company.
Assisting Inalpolat in monitoring and processing acoustic data from the sensors is mechanical engineering Ph.D. student Connor Pozzi.
“The global need for clean, renewable energy is at an all-time high as the effects of the climate crisis grow more apparent with each passing day,” says Pozzi, a Seekonk, Massachusetts, resident who received his bachelor’s degree, also in mechanical engineering, from UML in 2022.
“The energy sector accounts for one of the largest portions of greenhouse gas emissions due to its current heavy reliance on fossil fuels, so the faster we can switch to renewable resources, the better chance we have at slowing down, and possibly stopping irreversible damage to our planet due to climate change,” he says.
Pozzi says the hands-on training he gets working on the project, as well as his co-op experience last year at ASM Nexx, Inc. in Billerica, Massachusetts, is helping him bridge the gap between concepts taught in the classroom and how they can be applied in the real world. “They will help me better navigate how to work together on projects once I join the workforce full time,” he says.
Inalpolat says graduate student John Yirrell has significantly helped the NOWRDC project move forward, though he will most likely not work on project. “John is scheduled to graduate in spring, so I will still need to hire one or two grad students to work on the project,” he says.
Inalpolat’s sound-based approach can be applied to monitoring both offshore and onshore wind turbines. By increasing turbine reliability and operability while reducing project risks and associated costs, his research has the potential to greatly boost the profitability of wind energy and help the country’s transition to renewable energy.
“Aside from creating a considerable number of jobs in the wind energy sector, our technology can help power more homes and avoid electric supply issues and interruptions, and thus significantly help the energy sustainability of the U.S. and other countries,” he says.