Preventing Biofouling of Oceanographic Sensors Using UV Illumination Powered by a Compact Wave Energy Converter

Oceanographic instrumentation is typically located far from power grids, and in environments prone to biological growth that covers scientific instruments and interferes with data collection. The objectives of this program are to extend the deployment period – thereby reducing costs and ship emissions – by capturing renewable energy from the motion of the instrumentation platform, and to improve scientific data collection by powering an anti-biofouling device to keep the instrumentation clear of biological growth. These systems must be cost effective, yet still survive the harsh ocean environment. The small business partnered with a research institution for Phases I and II. Phase I analyses calculated average available power >30W in an Atlantic buoy’s tilt, sufficient for a buoy-mounted Wave Energy Converter (WEC) to drive a light-emitting diode (LED)-based illuminator in the sub-300nm ultraviolet (UV) spectral region with 1W. Wave energy is frequently available when sun and wind power are absent; the WEC can charge batteries to run the UV illuminator during doldrums. The LED approach is far less toxic than the chemical anti-biofoulant tributyltin. A dockside test using such an LED effectively prevented bio-fouling growth on optical window materials. During Phase II, an oscillating laboratory test platform was built to test WEC performance. Prototype WEC engines with meter-long tracks were designed, built and tested. Average WEC output powers of over 8 W were measured into resistive loads for 16° amplitude tilts. A control circuit is being developed to charge a battery. This WEC design will be completely sealed and mounted on the deck of an existing buoy, avoiding corrosion and entanglement. Also during Phase II, the UV illuminator design was optimized for passive oceanographic conductivity measurements. A novel optical system delivers a collimated beam down the axis of a conductivity cell with drinking-straw-like dimensions. UV intensities at the entrance and exit comfortably exceed intensities that inhibited biofouling for months during an associated experiment using open field seawater at another partner research institution. A housing for the novel optical system passed a 200m pressure test. An experiment with two conductivity sensors (one UV -protected, the other a control) will be tested off a dock shortly and is scheduled for buoy deployment this fall. Objectives of the Phase IIA program include: analyzing equipment performance during buoy test, improving WEC control system, making design changes if parts exhibit significant mechanical wear or UV degradation, reducing costs, particularly for WEC housing, testing revised prototypes on buoy The WEC and anti-biofouling systems will reduce operating costs and pollution by extending oceanographic instrumentation deployment periods through power generation and improved data collection.