Abstract
The Blue Technology Systems, such as offshore subsea energy systems, remotely operated and autonomous underwater vehicles, ocean exploration systems, and subsea oil extraction, have proliferated in the past decade. Using thick and heavy Pressure-Tolerant metal Cylinders (PTCs) is the prevailing method to enclose electronics and shield them from hundreds of bars of surrounding hydrostatic pressure while maintaining one bar inside. This approach has numerous weaknesses, including high cost, buoyancy issues, implosion or leak due to unreliable penetrators and connectors, complicated cooling, and frequent maintenance. Exposing space-demanding power-processing components to the surrounding pressure can solve these drawbacks. However, the present knowledge of Pressure-Tolerant Power Electronics (PTPE) components and systems is insufficient and often lags years behind the component technologies. Moreover, pressure-instigated high failure rates and parameter drifting of electrolytic/film capacitors and inductors require rethinking the traditional power converter designs for pressure-tolerant operation.
While electromagnetic, thermal, or even radiation specifications are commonly included in datasheets of electrical components, that is rarely the case with pressure. The so-called “survival test” in specialized laboratories followed by inspection at 1-bar pressure was often considered sufficient, neglecting that the operation of a component or system can be altered under extreme pressure without permanent damage. Companies typically retain obscure, outdated lists of pressure-tolerant components and design procedures to address this problem.
Researchers mark the beginning of the PTPE era with the work of Barnes, Gennari, Holzschuh, and Suton from the US Naval Research Laboratory in the 1970s. This research “wave” provided the initial descriptions of passive pressure cycling tests, functional tests under pressure, and prolonged soaking tests. Initial assumptions regarding the pressure impact and failure methods are validated, and compatible compensation fluids are proposed. The second research “wave” started around 2005 and was instigated by governmental agencies and companies hoping to reduce costs and improve offshore oil drilling and extraction reliability. This research advanced the practical knowledge of PTPE, focusing on modern components. The researcher identified a strong connection between the packaging technology, voids in component packages, and the pressure-tolerant operation. The Blue Economy initiated the third research “wave,” which is still ongoing. This primarily refers to the rapid expansion of offshore renewable energy generation and subsea exploration systems, identifying the lack of reliable penetrators as a critical factor.
This abstract and the final paper will comprehensively review past and current research on PTPE components and systems and identify critical challenges toward wider technology adoption. The paper will discuss four critical PTPE-related topics: i) Lacking a validated testing methodology, identifying ii) Pressure-related component models, iii) Packaging requirements of PTPE components, and iv) Lack of failure rate models of critical PTPE components. The paper will summarize how academic-industry collaboration can improve underwater and benthic systems by enhancing PTPE to be less expensive, more reliable, and more efficient. Finally, the recent development of an automated test station for live (energized) pressure testing of components and small electronic systems with absolute boundaries of 10,000 psi, 30 A, 3 kV, and -10oC to +40oC at NCSU will be discussed.