Datawell's Ocean Buoy ultracapacitor assisted solar power system - Maxwell Technologies - #1

By Dennis van Weeren and Henny Joosten, Datawell BV, The Netherlands; Roger Scrivens, RS Aqua Ltd, UK, and Adrian Schneuwly, Maxwell Technologies SA.

The world's oceans are constantly in motion, and a knowledge of the ocean waves is vital for safe shipping and to understand coastal erosion. Wave measurement and analysis is therefore of great importance.

To measure waves in remote locations or far offshore, the most common solution is to use buoys that contain measuring instruments, a power source, and the means to transmit measurements. Once put in position, it is desirable to be able to leave the buoys unattended with no maintenance for as long as possible, ideally a number of years.This means that the power source, or sources, of the buoy must have an extremely long lifetime, and be completely reliable. Buoys are often deployed in remote locations, and maintenance and service is difficult and expensive. Batteries have traditionally been the main power source, but recently a new solution using ultracapacitors has doubled the battery lifetime.

One of the world's leading suppliers of wave measurement buoys is Datawell BV of the Netherlands. Since its introduction in 1968, the company's Waverider (WR) buoy has been recognised as a standard wave data acquisition tool. The more recently-introduced Directional Waverider (DWR) buoy uses three accelerometers to measure wave height and wave direction, and also monitors sea surface temperature. The buoy tracks its position using techniques based on the Global Positioning System (GPS), and transmits data using a high frequency transmitter at a range of up to 50km. Optional modules allow it to transmit datea via satellite telemetry or GSM mobile phone links.The Waverider has through its development used batteries as its main power source. In the early days there were no reliable alternatives, and work focused on achieving the lowest possible power consumption. Continuous improvements in electronics have resulted today in a specified power consumption of less than 0.35 watts for a Directional Waverider (DWR) continuously measuring and transmitting wave data. Using primary cells, the 0.9 metre diameter Directional Waverider has an operational life of three years between battery changes and the 0.7-metre version achieves more than one year.

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