A Hi Rocky Relationship Is it Not? Water & Electricity!

A Hi Rocky Relationship Is it Not? Water & Electricity! 

Mixing water and electricity doesn’t usually end well, but marine engineering group Knud E Hansen A/S sees this rocky relationship as a challenge.

According to the Handy Shipping Guide, the company has designed a new ferry capable of making an entire voyage on electric power. 

Many shipbuilders are following suit, looking for ways to create more eco-friendly, sustainable seafaring options, but all-electric propulsion systems come with their own unique issues especially in terms of maintenance; how do engineers and operators make sure their boats stay afloat?

Slow & Steady:

The new ferry comes in at 35 meters in length with a beam of 11 meters, capable of carrying 170 passengers and 12 cars from Nolsoy island to Torshavn and back again on single battery charge. 

It can also withstand waves of up to three meters high and was designed with energy conservation in mind, featuring both batteries and a heat recovery system. 

It won’t win any speed records, since it’s nowhere near the 100 km/hr or better ships designed to run on liquid natural gas (LNG), but the ability to run entirely on battery power and survive a potentially rough sea crossing is no mean feat. 

Simply put, the Knud E Hansen A/S ferry speaks to function more than form—and eschews traditional fuel-based thrust for clean and reliable electricity. 

Emerging Issues:

According to a Hitachi white paper, on board electrical propulsion systems come with a number of advantages including reduced noise and the integration of both power and thrust systems, but they aren’t without issues: Electric systems come with a higher initial cost, increased energy conversion loss and large overall “footprint” owing to more total component parts. 

Water infiltration can cause serious issues, anything from short circuits to total system failure.For example, Cruise Critic reports that last year a Carnival Cruise ship was forced to cut out a port of call after an electrical transformer malfunction, which limited the ship’s overall speed. In the case of a complete electrical drive system, such a short could be disastrous.

The New Maintenance:

What does this mean for shipping companies and marine organizations? That in an era of clean power, new maintenance tools are needed. 

Marine Insight argues that on board engineers must now be able to tackle challenges such as electrical motor overhauling and shore power supply connection, in addition to having complete knowledge of an engine’s automation system. 

Scale deposits also pose an issue, potentially inhibiting electrical connections and leaving a ship dead in the water; regular and precise descaling is required to keep engines in top shape.

The rise of Eco-friendly ship propulsion systems means less waste and better ROI for companies, but also comes with unique maintenance challenges—even the best electric system generates no profit in dry dock. 

Dealing with Scale Deposits in Maritime Environments:

Within ocean water, dissolved solids lead to lime scale deposits in offshore equipment systems.

Build-up of lime scale (calcium carbonate) deposits present problems, particularly in water cooled engine jackets as well as heat ex changers for production of hot water service for crew and passengers. In ship waste water piping, scale deposits will block off lines and scale up tanks as well causing adverse effects on pump seals and valves.

Boilers, steam turbines and ballast systems are also vulnerable to scale build-up of and subsequent problems of overheat, shut down or blockages.

Lime Scale deposits in these equipment systems can be effectively remedied by the use of inhibited acid descaling. 

Descalers quickly dissolve calcium, lime, rust, lithium carbonate and other types of deposits from passages in water cooled or heated equipment as described.

Hi Direct approach: improving wind turbine drivetrain reliability.

Hi Direct approach: improving wind turbine drivetrain reliability.

Offshore wind turbines have been plagued by reliability issues that have driven up costs and damaged confidence in the technology. But could a new generation of drivetrain technologies change this?

For nearly a year, people gazing across Scotland’s Firth of Forth have been able to catch sight of an impressive feat of engineering: the world’s most powerful offshore wind turbine. The 7MW monster — the first of its kind — has blade tips that tower 196m above sea level, sweeping an area twice the size of the London Eye.

The majestic structure is part of a bigger plan to make use of the UK’s offshore wind capabilities. The total offshore generating capacity in UK waters provides around eight terawatt-hours (TWh) of electricity each year, enough to power around two million homes. Industry estimates suggest that by 2020, offshore wind will supply between eight to 10 per cent of the UK’s electricity annually.

One way to overcome reliability issues is to take the direct-drive route. That is what Alstom has beenm attempting with its 6MW Haliade WTG wind turbine.

The technology is giving the UK a chance to conquer a growing global market. Offshore construction costs are high, but fairly predictable. Without the same size constraints, wind turbines at sea provide economies of scale. They also produce far more energy than their land-based equivalent, with offshore turbines reaching 3–8MW of capacity. These energy gains, however, come at a cost when it comes to maintenance.

A wind turbine’s drivetrain provides the biggest headache for engineers. ‘They are a classic issue in the wind industry,’ said Daniel Castel, offshore platform director at Alstom. ‘Lots of effort has been made to improve the reliability of the gearboxes but the truth is that there are still some issues that prevent the achievement of a lifetime solution. This is especially critical for offshore where the operating expense is so high.’

’Haliade WTG is a direct-drive solution featuring our pure torque layout that allows for sharp control of the loads that go through the power train. 

Daniel Castel, Alstom.

To avoid excessive damage, Ricardo has come up with a solution dubbed MultiLife, which involves rotating the fixed inner components so that wear take place throughout the full circumference of the bearing rather than just on a small section.

Historically, gearboxes have suffered from failures in both the planet bearings and the high-speed shaft bearings. The high-speed shaft bearings, which undergo huge forces, can often be replaced on site, but any planet bearing failure requires removal of the gearbox from the turbine for repair elsewhere. The downtime this creates means that close to 25 per cent of a wind farm’s maintenance costs are linked to gearbox failures.

‘Individual offshore turbines are now pushing well above 5MW capacity, so it is crucial to design and build in the highest standards of reliability from the outset,’ said Paul Jordan, Ricardo’s global head of clean energy and power generation. ‘We need to avoid the risk of high costs of failure and remedial replacement of major components such as gearboxes.’

Jordan’s team has been working on a gearbox and drivetrain design for the Samsung Heavy Industries 7MW offshore wind turbine being tested in Scotland. The mammoth structure is designed to gather energy in some of the world’s roughest oceans. It has a rotor diameter of 171.2m with a hub that stands around 110.6m above sea level. The rotor tip moves at 95m/sec, meaning the drivetrain has to handle torque of 6.9MNm.

‘The most challenging aspect was the six degree of freedom dynamic analysis of the full drivetrain,’ said Jordan. This analysis allowed the team to subject each piece of the gearbox to finite element (FE) analysis testing. ‘It was important for us to consider gravitational and assembly loads as well as those due to operation,’ added Ricardo’s chief engineer for the project, John Stanton.

The team’s simulation revealed wear on the inner bearing concentrated over a small arc of around 40˚. The team came up with a solution — dubbed MultiLife — which involves rotating the fixed inner components so that the wear would take place throughout the full circumference of the bearing. This, the team claims, extends the life of the bearing by up to five times and avoids the bearing damage reaching a critical condition.

But to achieve more gains in reliability, Ricardo claims new innovations are needed. ‘There are limits to the optimisation of drivetrains that can be achieved through intensive simulation,’ said Jordan. ‘However, there are further step-changes that can be achieved through the adoption of advanced technologies that we have developed from our experiences in other, more mature industrial sectors such as off-highway equipment, motorsport and 

road vehicles.’

Ricardo’s TorqLife technology is claimed to improve wind turbine architectures susceptible to damage from loads such as strong gusts or emergency stops.

One way to overcome the reliability issues is to take the direct-drive route. That’s what Alstom has been attempting with its 6MW wind turbine, dubbed Haliade WTG. ‘We do not have any gearbox in the drive train,’ said Castel. ‘It is a direct-drive solution featuring our pure torque layout that allows for sharp control of the loads that go through the power train.’ With no gearbox coupled to the generator, the turbine consists of fewer rotating parts, increasing reliability.

Ricardo has also developed a technology, named TorqLife, which it claims improves wind turbine drivetrain architectures susceptible to non-torque loads transmitted into the gearbox. The same potentially failure-inducing mechanism can also affect the generator for direct-drive architectures. This load can be created under certain operating conditions such as gusts or turbulent wind conditions and fault conditions such as grid loss and emergency stop.

TorqLife uses a dual-function coupling that avoids drivetrain overloads. It is based on an arrangement of hydraulic cylinders between the rotor shaft and gearbox, or direct-drive generator, which are able to isolate non-torque loads. Ricardo claims this innovation offers the prospect of enabling wind turbine drivetrains to survive in the harshest conditions for their full lifetime.

‘What makes our job really rewarding is that our endeavours will help ensure that a much greater proportion of renewable power is delivered to the grid, and at a much lower cost than would otherwise be the case,’ said Jordan. If the UK is to make the most of its offshore wind power potential, then technologies such as this will be vital to ensuring investors’ support for the industry. Addressing concerns over reliability could also help win over those who remain on the fence over renewable’