National Oilwell Varco

Background

The offshore Oil & Gas industry is being challenged to reduce pollutant emissions. To achieve this, in the current market situation of low oil prices and very low newbuild activity, new and innovative concepts are needed to combine reaching environmental goals with improved economic viability. Reduction of system cost, as well as reduction of operational cost are essential to increase profitability under such economic climate or conditions.

One of the largest potentials for offshore installations and vessels to reduce both operational costs and emissions is by reducing fuel consumption. National Oilwell Varco has developed a compact and reliable high efficiency hybrid energy storage system that will enable significant fuel saving on floating drilling vessels where space is limited.

Challenge

Offshore installations far out at sea do not have the benefit of being supported by onshore power grids. They rely on local power generation by means of a set of large diesel-powered generators. For drilling vessels (floating installations in particular), strict requirements are set for the power supply system. The equipment they need to power is operated under challenging and constantly changing (weather) conditions and require large amounts of energy in order to perform their main task. Compensation of wave motions, sea currents, and wind, as well as hoisting and lowering extremely high loads are causing peak demands in the power supply. These peak power demands on top of the normal power requirement on board for utilities are causing a high fluctuation in the diesel engines powering the generators, resulting in low engine efficiency. Solution National Oilwell Varco AS (NOV) is battling this inefficiency by introducing a kinetic energy recovery system together with a battery bank designed for assisting heavy electrical machinery. The system, named Power Blade Hybrid (PBH), will level out the power fluctuations seen by the generator engines and will be able to store excess energy and utilize this energy when needed.

 In the current market situation of low oil prices and very low new build activity, new and innovative concepts are needed to combine achievement of environmental goals with improved economic viability 

The solution will optimize and improve generator supply performance, with fewer diesel engines needed online. Each engine-generator can be heavier loaded and will also offset the need to start new engines. It will lead to reduced engine running hours, while the running hours are more efficient. Machinery with great fluctuating power demands cause extreme loads on the power generating equipment, will experience the greatest benefits from this system.

The project to develop and test a full-scale prototype is in full motion. NOV has partnered up with Odfjell Drilling and the project received financial funding from the Research Council of Norway through their DEMO 2000 program.

The PowerBlade Hybrid system consists of a flywheel and a battery bank. The flywheel has been thoroughly tested by NOV in a previous development project, the innovation for this project is adding the battery bank creating a true hybrid system where two energy storage systems work efficiently together

Adding a battery solution with a flywheel enables the system to utilize the advantages of the batteries which the flywheel is lacking, and vice versa. An illustration of this relationship is shown in the matrix below:

A flywheel energy storing system is the best choice for reliability and long lifetime, but has practical limitations when it comes to energy storage density. However, peak power output performance is still very good. 

A battery is the best choice with regard to storage density, but has practical limitations when it comes to limited cycle capacity and has a reduced lifetime. A hybrid solution allows superior support for all drilling modes: full peak power shaving in heave compensation and also when tripping in/out. Batteries in combination with flywheel enables nonstop operation of drilling equipment also through periods of generator blackouts.

With its energy storage desnity, PBH will offer large electric machines to accelerate faster and work more dynamically. Ultimately, this results in higher operational speed and efficiency for the entire offshore installation.

Currently the prototype has been assembled and tested at NOVs R&D testing facilities in Vennesla, Norway, only 20 minutes’ drive from NOVs office in Kristiansand. Now that the testing is completed, Odfjell Drilling has selected a drilling vessel with an NOV drilling system package and other supportive power service equipment for use as a case-study and pilot for large-scale testing. The main objective of the project is to proofthe key objectives regarding economic feasibility, energy storage capacity, safety, reliability and lifespan, and specific applications related to rules and regulations for drilling. Eventually show the industry that the new technology behind this concept should be embraced.

In conclusion the system greatly contributes to more energy efficient operations, reduction of environmental footprint, load leveling of generators by peak power shaving, and so lowering maintenance costs while increasing safety.