Parker Hannifin’s David Blood discusses how battery storage will shape the future of more efficient vessels and rigs. Andrew Dykes reports.
Battery storage is beginning to transform the ways in which we think about energy supply. Whether in electric vehicles, marine vessels or power grids, the operational and cost benefits offered by these systems mean they are no longer the domain of Silicon Valley firms with cash to burn, but viable solutions to long-fought problems. For that reason, the oil and gas industry should wake up to their potential.
Such has been the philosophy of one oil and gas equipment supplier for a few years now. Although perhaps better known for hydraulics, pneumatics, filtration, process control and other services, Parker Hannifin has also been one of the firms pioneering the use of grid-facing inverters and battery storage in new and interesting applications. Energy Grid-Tie market manager for EMEA David Blood explained more about the company’s entry into the market. Having produced large power electronics controllers for both DC and AC motors for various sectors for years, the company moved into inverters – components which convert DC into AC suitable for use on the grid. Some renewable generation applications required the permanent flow of regenerated energy from the electric motor or generator back into the power grid – something a standard inverter is unable to do. “We got involved with a project of trying to create an inverter that was grid-facing. The idea was that we got two of these – one facing the grid and one that was controlling the generator – and you could then continuously take the power produced by the generator and put it into the power grid,” Blood explained.
Successful deployment of these inverters led the group to undertake similar projects with large battery applications, allowing bidirectional energy flow in and out of the battery. From this point, the company’s remit expanded into designing and manufacturing battery container systems complete with cooling and fire suppression systems. These containerised solutions also allowed the designers to incorporate the inverters – and in later iterations, control systems and PLCs as well – meaning an entire storage system and energy management system (EMS) can be shipped to site in one package.
Initial projects have been largely confined to the power industry, particularly in frequency management applications, but include supplying more than half the capacity of a pioneering 100-MW li-battery storage system in the US.
Lightening the load
Beyond a few projects in hybridising vessels and expanding subsea electrification, large-scale batteries have not gained much traction in the industry thus far – even despite the similarities between a large platform/drillship and an islanded grid. Indeed, the drivers for deploying these technologies in oil and gas are similar to those on land, particularly in situations with high power costs, those which require added redundancy, or which have variable “peaky” loads.
Drilling platforms and rigs require considerable power generating capacity to drive operations. The nature of drilling means users can ill afford to have insufficient capacity at their disposal, so requirements for redundancy and peak load typically result in capacity that is usually oversized for the job and spread over multiple generating units. While necessary for operations, running generators in this way – at variable loads and speeds according to demand – is not ideal in terms of fuel and maintenance costs, and has knock-on effects on the quality and supply (voltage and frequency) in the system.
This is primarily because generators are best used at a specific load and speed – the so-called “sweet spot” – for maximum efficiency. The closer these units are run to those optimum levels, the better their fuel economy, emissions and power regulation. It is here that Blood sees a perfect opportunity for batteries.
“If you put an energy storage device in there, that would allow you to intelligently switch some of the generators off and cycle around them to equalise running hours,” he explained. “You still have all the redundancy, but you’re just running the system in a more efficient way.”
Blood uses the example of four generators driving a number of variable loads on a rig, including top drive, mud pumps, etc. Rather than receiving a sub-optimal supply from four units, a battery system would allow the operator to turn off one unit altogether, supplementing it with a containerised battery and control system. This can help optimise the load on the remaining three units, while additional power is dispatched from the battery to help the units cope with variable or indeed peak loads.
“These big swings in power production all cause the frequency and voltage of the generators to move, which can have a detrimental effect on other equipment on the system. With a storage system you can ensure much better power quality, keeping frequency and voltage where they should be and at the same time helping to run the generators much more efficiently,” Blood added.
Battery storage also allows the recapture of energy that would otherwise be lost. He continued: “There are times when you’ve got net regeneration in the system and there’s nowhere for that energy to go because you’re an islanded system. I believe the way they solve that problem today is just to burn the electricity in resistors and choppers – whereas what you could be doing is putting that in a storage device to consume later on.” Coupled with more optimal use of fuel in the generators, a system with this flexibility could have significant implications in terms of operator spending – both in reduced capex on generators (reduced size) and reduced opex through more efficient fuel use and maintenance.
It is helpful to put those gains into context. One scenario where storage could be of use is in lowering and raising drilling pipe sections. During lowering, regenerated energy is released on to the drill rig’s electrical grid – and that energy will increase with each new section of pipe added and lowered. Much of this regenerated energy can be consumed by other loads on the electrical grid such as positioning thrusters, but any excess can be stored for consumption later when needed.
In the reverse process, where pipe is raised, the opportunity for storage comes from capturing the energy from lowering an empty hook before raising a pipe section. Analysis of this process by Parker engineers indicates that over 10% energy could be saved over the raising process with a consequent reduction in fuel costs.
My other rig is a hybrid
Although it remains early days, Blood says that there is already appetite within the sector for these technologies – especially within the drilling business. At a recent conference in Houston, drilling contractors were already enquiring as to the potential for several energy storage technologies, including batteries, flywheels and even supercapacitors. The latter in particular could offer a neat solution to the problem of storing much smaller amounts of energy over short bursts, but may not offer the same flexibility as batteries. “When production cycle turns net regenerative can you store that energy in a supercapacitor with a grid inverter,” added Blood. “They can’t store as much energy, but they can store it and release it very quickly.”
There are also space limitations – supercapacitors are physically quite big for the energy stored, Blood explained, meaning they may not be ideal on the limited deck space of a rig or drillship. “There are all sorts of trade-offs, but it was interesting to hear that some companies are genuinely looking at this,” he continued.
Any use of energy storage in oil and gas will also raise the issue of safety. Given some of the chequered history of li-ion packs in smartphones and other devices, there are necessarily some challenges in adopting the technology in explosive and/or marine environments. However, in Blood’s experience, equipment manufacturers are already rising to the challenge: “What you see now from big battery vendors is that they are making specialist variants. You are starting to see a whole class of li-ion batteries now that are being engineered to put on vessels. These are all pretty much li-ion chemistries perhaps with different module constructions – for example in ruggedised housing, or water-cooled pouches.”
With new application-specific constructions, the hurdles to deploying these systems are rapidly diminishing. Each project of course requires its own analysis of the equipment used and its peak load, but Blood is confident that few systems should present issues to a well-managed EMS: “Essentially what you’d be doing is adding the storage on as a new piece of equipment.”
So is the technology ready to go? “For an electrical grid-facing inverter, the answer is a categorical yes, because we do it now,” he affirmed. “Never mind the drilling cycle – there’s a whole movement out there in which people are going to hybridise thrusters and drive-trains on ships. There will be generators driving the ship and coupled to battery banks through grid inverters – that’s going to be the ship of the future.”
Given the potential upsides, efficiency gains and emissions savings from battery technologies, they are already everywhere, from our vehicles to our homes to our power grid. The question now is not if they can make the jump to rigs, but when?