High-power energy storage provider Corvus Energy has been selected by Houston-based National Oilwell Varco (NOV) to supply the energy storage system (ESS) for a PowerBlade installation, the energy storing unit developed by NOV that receives and provides energy based on operational needs of offshore drilling units.
NOV notes that PowerBlade is used in two ways to improve the efficiency of its drilling rigs – energy regeneration and peak shaving. For the former, operations involving frequent and cyclic hoisting of heavy loads require high levels of energy from power systems to lift the loads. Until now, drilling units have not typically been able to make use of the regenerated energy created when lowering a load.
“Offshore drilling units perform advanced operations in uniquely challenging environments that involve waves, winds and currents. Capitalizing on energy regenerated during heave compensation or tripping operations on offshore drilling units can be challenging,” explained Oddbjørn Øye, product responsible energy recovery systems – robotic control drive tech and winch at NOV.
PowerBlade harvests the braking energy emitted when a drillstring is lowered, storing it in the ESS, and then reusing that energy for the next hoist of the drillstring. “With our first PowerBlade installation, we determined that an energy storage system can reduce power consumption by the drawworks onboard a rig by up to 80% in active heave compensation mode compared to traditional design,” added Øye.
On an offshore rig, the drilling drawworks places the heaviest burden on the rig’s energy supply by causing a wide variation in energy consumption over large power peaks. “Typically, six to eight large diesel generators account for the rig’s total energy supply,” stated Øye.
“An energy storage system smooths the load, levels out the power peaks of the lifting system, and provides the generator system a uniform load, improving equipment performance, enabling the generators to run at optimal load, and reducing wear and tear.
“By enabling some of the generators to shut down and run the remaining in high load, the ESS increases fuel efficiency and reduces emissions. A generator set running on high load consumes approximately 15% less energy compared to two generator sets when producing an equivalent total power. PowerBlade enables the operator to rely on a higher, optimum sustained generator load.”
According to NOV, impressive energy savings were shown in a study of the PowerBlade installation and other energy optimization projects onboard the drilling rig Deepsea Atlantic. Estimated savings on this specific rig for the entire project, including the PowerBlade installation, were 6.5 tons of diesel, 20 tons of CO2 , and 300kg of NOx per day compared with log data prior to the project.