Switching to a DC grid to solve the power challenge

Switching to a DC grid to solve the power challenge
Carlo Cecchi, director, business development, Yaskawa Environmental Energy / The Switch. Image courtesy of The Switch.

A big weakness of conventional AC electrical systems on ships is that they´re generally cumbersome, inefficient and potentially expensive to maintain, says Carlo Cecchi, director, business development, Yaskawa Environmental Energy / The Switch.

Switching to a DC grid based on state-of-the-art modular technology offers a unique degree of flexibility, improving energy efficiency and helping to curb fuel burn. It´s a great way to reduce pollution right now while saving money in the long run, said Mr Cecchi. As new energy carriers emerge, future-proofing vessels for any type of power source is a shrewd investment. Compact size and lighter weight also make a DC grid the best answer from a vessel design perspective.

As the maritime industry becomes more environmentally aware, Yaskawa Environmental Energy / The Switch believes that around 80 per cent of vessels in future will be either fully electric or powered by hybrid systems. Many will have multiple power sources in addition to main engine gensets running on diesel, LNG or a combination of both. Renewable power from hydrogen and potentially ammonia fuel cells, solar and even wind may increasingly be part of the mix as shipping adapts to the changing energy landscape to combat emissions. Other onboard power sources will include stored power from batteries, power from shore, and shaft generators converting mechanical power into electricity.

Making the complex simple

Managing and distributing all that energy effectively is an intricate business amid a proliferation of load demands ranging from main propulsion and thruster drives to all sorts of electric actuators (winches, cranes, pumps, chargers etc). Not to mention onboard data systems and hotel demand.

Yaskawa Environmental Energy / The Switch has a solution for power management that takes that complexity and simplifies it. Switching from an AC to a DC grid delivers better fuel consumption, cost savings, and reliability. The company’s DC Hub can reduce fuel burn by 20 per cent up to 35 per cent – depending on the ship´s operational profile and fuel hedging – while boosting energy efficiency resulting in less emissions. It also guarantees overall lesser opex and a reduction in maintenance costs of 10 to 20 per cent.

Optimal design

A future-proof system requires components that can produce, transmit and consume energy as efficiently as possible. Yaskawa / The Switch’s DC Hub uses standardised independent power drives (inverter and rectifier modules) fully integrated into one coherent solution. The Hub works with any power source to ensure flexibility. Frequency converters ensure a constant supply of power that is 100 per cent reliable, which Mr Cecchi said is essential for specialised tonnage such as offshore vessels and wind-turbine service vessels using dynamic positioning for precise steady-state operations. This modular design offers unparalleled malleability in that module cabinets can be added in series to match changing requirements. Before that would have required a complete electrical redesign, now, Mr Cecchi said it´s as easy as arranging Lego bricks and scalable to any number of actuators.

The problem with AC

Power sources feeding in parallel into an AC system means you have to match frequency, voltage and phase to the running grid. That means an array of bulky components like transformers and gears, causing waste and losses in the system. The rectifiers in a DC system convert the AC generator voltage to the DC main bus voltage resulting in very fast power-generation response. DC Hubs are also especially efficient for DC energy sources like batteries and fuel cells, minimising the number of conversions required. Managing stored electric power effectively is particularly important when vessels need to sail pollution-free, that is in electric mode – for example, a superyacht sailing into a protected bay, ferries carrying passengers in emission-free zones, or a cruise ship navigating an urban port.

Space saving and time saving

By reducing the number of bits in a conventional AC system, the DC Hub is both lighter in mass and more compact, requiring less valuable space below deck. Another advantage is that the control software is located in a separate control cabinet, not in the drive modules themselves. That means each cabinet can easily be unplugged and replaced. A crew member can do this in under half an hour with no lengthy specialised training. This cuts down not only wear and tear, but also the need for spare parts and downtime for maintenance.

Mr Cecchi said that in his book it’s also a smart investment from a lifecycle perspective; choosing a DC Hub is guaranteed to extend the lifetime of vessels and ensure their residual value remains high. Fitting out newbuildings is obviously easier in terms of optimal design because you´re starting from scratch, whereas on a retrofit you have to work with the space that´s already there. Whatever the vessel, we´re calling them E-vessels, where the E stands for engineered. The firm’s permanent magnet (PM) technology complements the package to drive efficiency to a new level.

Don´t be fooled by cheap options

Mr Cecchi said that he doubts some suppliers who are touting solutions for variable speed frequency conversion on the cheap can guarantee performance. While they might look good in terms of short-term capex, in the long run such solutions will likely require a lot more TLC (tender loving care). Which means operating expenses go up, eating away at the profit an asset is generating.

Mr Cecchi also confirmed that he’s had quite a few conversations with shipping bankers who really like the company’s approach. “Some have told me it could be easier for owners to get a loan at preferential interest rates if they choose our technology; in other words, it can shine up an owner´s bankability, to steal a word from the solar industry. That´s a strong intrinsic advantage.”

Lowering carbon footprint

The main point is lowering a vessel´s carbon footprint. The onus is on the industry to do all we can to curb emissions for a cleaner world. Helping to make that happen motivates all of us every day at Yaskawa Environmental Energy/The Switch, said Mr Cecchi. “Just like we´re seeing with the Coronavirus threat, we´re all in the same boat and this is a communal effort. Forward-looking shipowners are already there, saving money in the long run.”