How do you power a fleet of electric ships?

What does it take for a hybrid, or even fully electric ships, to become the norm? Well, like with every climate oriented topic, now we come to the part of the show with more questions and challenges than answers. And probably the biggest challenge is, unsurprisingly, power.

Peter - A vessel like this, a hybrid vessel, has got two elements to it. First of all, when it's at berth, it can have a hotel load. So this is a load that needs to provide electricity for lights, for ventilation, all the basic functions of the vessel. In a ship like this, that's about 1.7 megawatts of power. Now, to give you an idea of a megawatt, if you think of a five watt LED light bulb, a megawatt would be 200,000 of those light bulbs. To recharge those eight megawatts of batteries you've got on board, you would need 20 megawatts. That's the equivalent of 4 million light bulbs of power. So if you imagine the size of the cables, the sheer volume of power that you need to provide the power for the energy for this ship is just astronomical.

Will - Two things leap to mind immediately. One, Dover and to an extent Calais, is kind of out of the way. You've got to get all of this power down, maybe not the biggest grid in the world, and then charge up these ships. And the other problem is you've got 45-50 minutes to do it.

Peter - That's right. For decades, we had centralised power stations in the coal fields of Nottinghamshire, these massive coal power stations that generated vast amounts of power and distributed the power out around the country. The challenge with that was that the further you were away from those power stations, the smaller the connections became. It's like a human body and their veins. Ports, by their very nature, are on the outside of the country, and if you've got the infrastructure that's been built up around this infrastructure being largely in the middle of the country, it's a real challenge getting these huge amounts of power to these ports. But these things are changing, particularly with the advent of renewable energy sources. A lot of offshore wind farms are coming online, and also local production, solar panels and energy production means that the grid is becoming far more complex. And trying to manage this power demand is one of the biggest challenges we're going to face in decarbonising shipping.

Lisa - In terms of the availability of energy, whether it's electricity or another fuel source such as hydrogen, nuclear ammonia, there's increasingly a need to move away from a centralised system to a decentralised system and have it where it's needed, so local hubs. The problem with that is, if you have onsite or offshore renewable generations, such as wind turbines, most ports are in areas where there is protected wildlife. So there are prohibitions about putting up a wind turbine if you're talking about onsite generation or storage even of something as toxic as ammonia. That will be a problem for the people that live and work in those ports.

Will - And I guess the question of, you have to generate all of this electricity as well, even if it's a nuclear power station or something like that. Quite a lot of the electricity we're currently generating is by burning fossil fuels, so there's also the idea that you might end up burning fossil fuels to get this electricity in the first place.

Lisa - That's exactly right. In terms of the source of the electricity that's coming to the batteries or coming to the shore power, if it isn't green, it's just as bad as if we had a diesel engine running. So there are various policy instruments to encourage people to move away from that. Things like the insistence on using shore power at European ports, that's coming in by 2030. Again, within the EU and also coming to the UK is the emission trading scheme to encourage people to think about the source of the energy and if it's from a green supply.

Peter - So there are lots of debates about, if we're just using electricity to provide shore power or to provide energy for its batteries, aren't we just changing the problem? Instead of the diesel engine that is onboard the ship producing this electricity, aren't we just changing it to a power station? But, in actual fact, the UK grid operates around about 150 grams of CO2 per kilowatt hour, whereas the engines on board a large vessel typically produces about 650 grams of CO2 per kilowatt hour. So it is far more efficient to use grid electricity to provide this energy than trying to generate it with diesel engines. And also, as we're seeing, the UK grid is gradually being decarbonised. We're seeing more renewable energies coming online, so that figure of 150 grams per kilowatt hour is only going to come down.