Stories told by a wave buoy through 12 months’ worth of data collection

Author: EIVA Hardware Development Manager Martin Kristensen

The EIVA ToughBoy Panchax wave buoy is the newest buoy in the class of EIVA sensor platforms offered to the maritime industry. We shipped some of the first units a couple of years ago for a project focusing on infrastructure improvements through the construction of a new coastal highway. Throughout the entire project period, the customer needed to monitor weather data, which became possible through the deployment of two ToughBoy wave buoys.

Consequently, even though we haven’t seen the buoys since they left the hands of our production team, we have followed them through the data they have continuously been transmitting to our servers and would like to share the stories told by these.

As is the case with all ToughBoy units, our web-based software solution, ToughBoy Onshore, allows for the remote configuration and monitoring of the buoys. This includes access to all the data gathered by the buoy sensors since the units’ deployment.

Excellent battery performance and taking on high waves

When looking into the details of the data provided by the buoys, it is possible to analyse their performance. Perhaps most interesting is how the power system ensures year-long battery life.

The power system of the ToughBoy Panchax is based on two energy sources, a primary and a secondary source, which are combined by the intelligent power handling system (IPHS). The primary source consists of four 50W solar panels, a deep-cycle 1,200Wh AGM battery and two MPPT (Maximum Power Point Tracking) charge controllers. The secondary source is a 16,000Wh custom-assembled alkaline battery packet. 

Whenever the primary energy source is able to contribute with sufficient power to the buoy’s sensor data collection and processing system, the IPHS will give priority to it. During periods where power harvested from the solar panels is limited by a low amount of sun hours, such as during the winter season in the North Sea, the secondary battery will step in. However, as the data shows from the deployed buoys, the primary energy source is so effective that it may not become necessary to use the secondary battery at all: Due to the location of the customer’s construction site being in an area with plenty of sun hours, the secondary battery was never activated.

The graph in Figure 1 shows the voltage of the primary battery over the course of one year. The fluctuating voltage is caused by the solar panels charging the battery. In the section view in Figure 2 it is easy to see the charging cycle. The section view is from a period with rough weather (see wave height in Figure 5), and the battery remained fully charged. This shows the level of efficiency of the primary energy source – that is, the solar panels combined with a rechargeable battery.

The graph in Figure 3 shows the voltage of the secondary battery. When comparing the voltage graphs for the primary and secondary batteries, we can see that the secondary battery was never used during the 12 months, as the location of the buoys provides enough sun hours for the primary battery. Also, the expected self-discharge of the secondary battery is 3-5% per year. In this case, however, we can see that it is less than 1%.

Another interesting data type to mention is the wave heights measured during the last year. These show that the ToughBoys have kept the guard even during rough weather, with up to seven-metre high waves.

Expanding the features of ToughBoy Onshore in 2018

Until now, the ToughBoy Onshore software has gathered all sensor data in tables for export and for online monitoring. In the beginning of 2018, features will be expanded to include visualisation of these data in graphs directly in ToughBoy Onshore.

In addition to providing graphs similar to those used above, others include the position of the buoy, wave direction and period.