Micro Electro-Mechanical Systems (MEMS) sensors are microscopic devices, typically etched from a layer of silicon and mounted inside a tiny enclosure with integrated electronics. MEMS were first commercialised in the 1980s but today they are mass-produced devices and feature in a huge number of home electronics and industrial applications. For example, every car leaving the production line today has dozens of MEMS sensors including accelerometers, gyroscopes, pressure sensors, flow sensors and inclinometers. They are relied upon in these safety critical automotive applications. Mobile phones and video games use MEMS accelerometers and gyroscopes, and it is estimated that over 11 billion MEMS sensors were produced globally in 2018.
There are significantly more MEMS sensors than people living in the world today!
Surprisingly, most condition monitoring systems (CMS) in the market today still use traditional piezoelectric (also known as ICP or IEPE) accelerometers. This sector has perhaps been a bit too comfortable with existing technology and not had the pressure to innovate? One factor is that ICP sensors are effective, they work well. However, they are not cheap and require expensive analogue electronics inside the CMS unit. MEMS sensors are a reliable and more affordable alternative that provide the required performance, whilst allowing for lower cost electronics. They also bring additional sensing capability.
In the wind industry this is particularly relevant, as price is a major factor for purchasers of CMS. MEMS have changed the landscape and now allow owners to fit CMS to wind farms where they previously had not been able to make the business case stack up, due to the upfront install cost.
Historically, even up to a few years ago, MEMS accelerometers did not offer a high enough frequency bandwidth for condition monitoring and this is a factor in the slow pace of adoption. However, MEMS technology has advanced rapidly in recent years – driven partly by the uptake in sensors for mobile phones and video games – and MEMS sensors are now available that can measure up to 10 kHz, more than enough for monitoring every component in a wind turbine drivetrain.
MEMS technology is mature and the supply chain is well established. In 2018 the global MEMS market was estimated to be worth over $53 billion. To put this in perspective, this is nearly five times the size of the entire global wind turbine O&M market for the same period!
MEMS in action
In a recent case study, Alistair Warwick, VP at BP Wind Energy, talked about how disruptive MEMS technology changed their cost calculation: “We looked in the past at retrofit but it wasn’t affordable, however ONYX InSight brought a new value proposition to the table and combined with their track record of quality engineering with BP, it was an easy decision to move ahead with adopting this technology.” And it has proven its worth, in the recent Wind Turbine Technical Symposium, in Golden, Colorado, BP presented information that for the first 50 turbines fitted with ecoCMS, ONYX detected 10 drivetrain issues, all confirmed and repaired, with a considerable cost saving. BP Wind subsequently installed 300 additional systems across 5 wind farms.