Although a relatively new technology, off shore wind energy is the leader of the three technologies with 2,946 MW currently deployed in Europe, and plans for North America’s first off shore wind farm to be developed during 2012.
The wave and tidal energy industries are at an earlier stage, lacking the head start the off shore wind industry gets from historical success with onshore wind. However, the Carbon Trust in the UK has estimated that 240 GW of wave and tidal energy could be deployed globally by 2050, with the majority of that coming online starting in 2020—the bulk of which will likely come from wave power.
All three of these sectors are still in a phase of signifi cant technology development and accurate measurement will be critical to their future rollout.
Project lifecycle monitoring
The project lifecycle in these three industries develops along a similar and consistent path. Environmental monitoring at each stage is a critical factor in the success of the energy capturing device, whether it’s a wind turbine, a wave-energy converter, or a tidalenergy converter.
Initially, developers work through an assessment phase where environmental measurement is crucial to the overall success of the site; not only in assessing the potential of the location, but also the positioning of the energy capturing devices.
• Energy potential at the deployment site;
• Long-term survivability of the device;
• Ease of access for maintenance and service; and
• Proximity to the community that will receive the energy.
Of these, the most important factor is energy potential at the site. Th is data can be acquired from historical sources such as wave watch models, or using in-situ instruments such as wind, wave, and current buoys. Th ese buoys provide reliable, highly accurate, real-time data over a long period of time, which allows developers to evaluate the location and make informed decisions about whether to use the site being monitored. In addition, the weather data analyzed by oceanographic consultants can be useful in determining if the energy capturing device will stay anchored in place so as to provide longterm energy.
Once the assessment phase is complete and the site has been confi rmed, the energy farm is then developed. Given the cost of working in such a harsh environment, accurate environmental weather data is essential to control expenses and protect assets. For example, it costs approximately £12,000 (about $19,500 US) per day to hire a service vessel, which could potentially go out to a location only to sit idle because the sea state doesn’t allow the location to be serviced. Knowing the weather in advance from a data buoy transmitting environmental conditions by satellite can save developers thousands of dollars during the manufacturing phase.
Once the energy farm is built and in a production stage, it still requires constant monitoring to ensure the maximum power output is maintained. Monitoring equipment can help developers understand if they are getting the estimated amount of power from their capture device that they were initially expecting.
To ensure developers get this data when required, a reliable telemetry choice such as Iridium, Argos, or Inmarsat satellite can be used. Data from the monitoring equipment should also be logged onboard as a backup, just in case there are transmission issues. To keep the energy capture device working year-round requires a dedicated team of trained and experienced off shore experts. Th e costs of ongoing service work over the long run are a signifi cant part of the annual operational cost of off shore energy.
Finally, at the time of upgrade, developers face similar challenges to those seen at the start of a project since they’re required to reassess and commence again. Initial program success is essential to gaining ongoing support from stakeholders.
• Wave & current buoys
Wave and current data is an important parameter to monitor to ensure safe and secure waterway navigation, as well as the energy potential for a renewable energy capture device. Th e inclusion of water level, 3D currents, and wave height, speed, and direction spectrum are essential details for off shore developers. Wave and sea surface temperature data are collected, processed, and logged on the buoy, and then transmitted to a base station where developers can analyze the data to make informed decisions regarding their project.
• Meteorological buoys
Ocean and coastal monitoring buoys can be designed and confi gured a variety of ways, depending on the data requirements and environmental conditions. A typical buoy can measure wind speed and direction, atmospheric pressure, air temperature, relative humidity, water temperature, currents, waves, pH, and other water quality parameters. Raw data is processed and can be logged onboard the buoy and then transmitted to the end user. Th ese buoys provide the dual function of automated weather station and navigational aid. Deployments can be in a variety of locations, from calm, shallow waterways to 5,000m depth in open oceans.
• Wind buoys
The standard solution for gathering wind resource assessment data is to construct a met mast equipped with anemometers. In the off shore environment this solution is diffi cult and expensive. New buoy-based technology uses a laser wind sensor, or LIDAR, to gather wind data at turbine hub-height that can survive in the hostile environment and provide accurate data due to its unique in-built motion compensating capacity. Th ese buoys can be used to assess power from a location prior to setting up or building a turbine, and then manage that turbine going forward. Additional sensors can also be integrated onto the buoy including, weather, water quality, and even bat and bird sensors.
Even though the off shore renewable energy industry is still in its infancy, ocean-monitoring technology has been in use for decades, and can play an important role in making off shore renewable energy a success in the years to come. Graham Howe is part of the International Business Development for Renewables at AXYS Technologies Inc., while Don Bryan is the company’s Marine Systems manager.
By Graham Howe & Don Bryan
Source: Axys Technologies, July 8, 2011;