Off the Grid – Port Strategy, April 14, by Stevie Knight
Read the full version of the article here.
Battery improvements
There’s one change that stands to create an entirely new market dynamic: evolution of batteries.
“Only recently has efficient, lithium-ion based energy storage technology dropped to the right price threshold,” says Brent Perry of PBES. Further, he explains there’s been a lot of solid work on the technical side to avoid headline-grabbing thermal runaway incidents.
These two developments have already sparked a certain curiosity about the potential applications for both ports and ships, but Mr Perry explains a reality check is necessary: “We say although there are a thousand things you could do with batteries, there’s probably only five or so that you should do.” While these vary, number one is often about meeting new environmental legislation.
To deliver on the promise of easy, clean, on-the-spot power without large scale infrastructure work, PBES has developed a couple of practical solutions. On the waterfront a battery barge can supply 4MWh of energy to visiting ships, allowing them to turn off the engines while at berth. On the land side, the company’s newest project is an array on a skid “which provides 1MWh of power that can go anywhere in the port”.
As the units are plugged in and recharged from the grid, it does need to be approached ‘holistically’, in partnership with the local electricity supplier explains Mr Perry. However, since the recharge is typically overnight the port could go beyond, gaining from cheaper energy: “In some places we’ve found that the grid has so much excess during hours of low demand that there’s money to be had in offering to help balance the grid by taking some off on a reliable basis.”
So the port generates revenue and cleans up, both literally and figuratively.
Metric difficulties
However, Mr Perry adds that “backup power remains very much a fringe benefit that’s difficult to apply payback metrics to. There is a global trend for national electricity networks to be challenged by more demand than they were originally designed for.”
He points out that given this, batteries retain a very useful characteristic. “For example an energy storage unit rated at 6MWh is actually capable of squeezing out 40MW for just a short burst, and a fully charged device can offer 60 minutes of full power backup or two hours (or more) at reduced power.” He adds that it’s a useful trick as even half an hour is almost always enough to allow the engineers to get something back online. It’s also fast: “Even with a so-called ‘black start’ a sudden, complete failure from the grid – the batteries cut in so quickly you don’t notice it.”
However, although complete failures might be rare in developed countries, what’s not so uncommon is a wide variation in voltage as ports are typically at the furthest reaches of the grid, and are often left without a good, stable power supply. A grid supply can wander over 10V in either direction while by contrast an energy storage solution typically operates within a quarter of a percent of the right power.
Therefore, Mr Perry explains that discussions are beginning around permanently attaching an energy storage unit to the grid along with other renewable sources, collecting the charge when it’s viable and dealing out the electricity from there.
Of course, the port can charge the incoming vessels and even its tenants something for the service.
He concludes: “Since we are now looking into installations with a one to three year payback and five years at worst, I’d say the opportunities presented by batteries are getting to the point where they are becoming irresistible.”
RTGS PRESENT THE ‘PERFECT STORM’
In the yard, diesel driven RTGs are ideal for hybridisation as they present the perfect storm of inefficiency, unreliability, and are emissions-prone, according to PBES’ Brent Perry.
“They have oversize generators to deal with peak draw and the container lifting energy, over three quarters of the entire demand, is most often just wasted. Plus they occasionally just run out of diesel throwing the loading schedule completely off.”
PBES replaces the usual 600kW generator with a cleaner genset one sixth of the size and an approximately 65kWh battery pack, based on high power, high cycle life titanate chemistry. “The battery pack takes all the variable load, leaving the diesel engine to run at its optimum, feeding the batteries from behind. This gives the solution a certain redundancy, he explains.
“Also, as we can recapture the lifting energy through regenerative braking, we can save around 80% of the RTGs annual fuel costs, plus if you change the engine for a Tier IV compliant genset, you drop the emissions by a massive 92%.”
Most importantly, he says “payback is less than a year”.
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