The Sub-Sea Economy of the Future

Energy from the deep? How and why should we get this?

Over 70% surface of our world is water – yet men can’t live or work at the bottom of the ocean.

It’s too cold – if it were colder the water would turn to ice. Cold water is heavier than warm water – so it sinks to the depths.

It’s too dark – sunlight doesn’t penetrate to these depths.

The pressures are too great – 400 atmospheres. The human record to withstand pressure stands at around 30 atmospheres – and the free-diver, Herbert Nitsch suffered from severe decompression sickness on surfacing, including several strokes. Add 1 atmosphere for every 10 meters underwater.

So, men can’t live at the bottom of the ocean – but robots can.

The tough robots can get us energy from the deep

Robots like a steady temperature – cold doesn’t bother them and working parts are less likely to fail. The dark doesn’t faze them – and they can withstand pressures that would crush a man.

Of course, they need to be controlled – and here man’s superior ability to solve problems, organize communication and control systems and design the infrastructure needed to maintain the robots is crucial.

Robots don’t get lonely! And the human operator keeps in touch by video and wire telemetry. The pilot of the Remotely Operated Vehicle or of the robot can work safely from the support vessel or land. A bit like having a brain in one place and the body in another!

Sure, there are and will be, autonomous robots that think and act on their own. There are swarms of them in the oceans right now working at the bottom of the seas for the deep oil drills. But it’s extremely difficult to make a machine think. So, progress on that will be slow.

Why do we need to exploit the seabed?

Fossil fuels are running out. It is becoming increasingly difficult to extract oil and gas. The oil fields in the continental United States and the North Sea are getting smaller and new discoveries cannot keep up with the decline.

True, there are huge reserves in for example the Venezuelan oil sands, but not counting these the British Petroleum estimates a 40-year limit to our supplies. Add in Venezuela and the estimate raised to 75 years and add in the Middle East the figure is still just 80 years.

So, if we haven’t replaced these oil and gas reserves by the time our grandchildren are adults – they will be destitute.

The undersea resources give them a chance – if we can put the infrastructure in to utilize them, and design efficient robots to repair and work in the deep, dark depths of the sea.

What uses will robots be put to?

There are large oil resources under deep water at the outer continental shelf – but they are difficult to extract – and expensive. These will become increasingly important as the easier to obtain oils and gases run out. In addition, there are large deposits of methane hydrate to help replace our present natural gas when it runs out.

And what when even these deposits are exhausted?

  • Geothermal heat. The mid-ocean ridges where the tectonic plates are separating are hot spots on the bed of the ocean. The “black smokers” release water in quantities like a small nuclear reactor. In fact, the energy released by the mid-ocean ridges is only a little less than the world’s needs today. You can read more about geothermal heat here.

Another benefit is that no one could complain about drilling causing earthquakes – or at least not so easily.

  • Storage. Real estate is becoming scarce and expensive. But there is a vast amount of space on the seabed as the picture of the Pacific Ocean from space shows. Storage will allow us to store energy from the deep and use it as we need.

     In addition, the storage would be protected from the ravages of weather – and people couldn’t complain about eyesores spoiling the landscape.

More future uses?

  • Increase telecommunications – high fuel prices may prohibit travel on the scale we enjoy.
  • Trash disposal – we have to dump our rubbish somewhere – preferable on someone else’s backdoor, or as far away as we can.
  • Intercontinental pipelines for the transfer of freshwater and manufactured goods need to made and maintained.
  • Mining – valuable minerals are there for the grabbing.
  • Transport of humans – and other robots as well as materials.
  • Police force? To counter sabotage, uncontrolled robots – including a pound to keep them secure.
  • Hospitals for sick robots – if they can be repaired on-site it would save transport costs.

What robots won’t be doing

  • Using deep ocean currents to extract energy by use of turbines – not enough energy and too dangerous in terms of altering the world’s climate.
  • Getting energy for the tides – not worth the effort

How can we store energy on the seabed?

The easiest way to store energy on the seabed is to store compressed air in tanks. It takes a lot of energy to compress air for these depths – but the energy could be retrieved by letting the air up in stages – releasing the energy as it ascends and using it to drive turbines.

A quick look at Lake Mead

Lake Mead
https://pixabay.com/photos/lake-mead-hoover-dam-nevada-water-664653/

Lake Mead is the biggest reservoir in the United States – it holds – or can hold- more water than any other reservoir. It lies just 24 miles from Las Vegas.

The maximum capacity is 32,220,000 ml of water. (26.12 million acre-feet) although it is said to be drying out over the last 20 years. The lake is 112 miles (180 km) long and 532 162 m) feet deep.it has a surface area of 247 square miles (640 km2).

So how does that compare with the possible storage facilities on the seafloor?

The robots would build tanks in situ. The tanks would be huge – over half the height of the hoover dam – 725 feet (221 metres). All the energy in Lake Mead would need about 400 tanks – and could provide power for Los Angeles for 2 months and would need an area only 1 1/4 square miles (2 km square). i.e. 200 times less than the area of Lake Mead.

And for the whole world, we would need about 300,000 tanks for one year’s supply of electricity and the ocean floor has room and to spare!

However, at present underground caverns are the preferred storage options, and there are plenty of them. They are fine for natural gas but less suitable for compressed air.

The cost of energy from the deep

Robots are not cheap – yet. The prices will fall as we mass-produce them. And of course, there is the cost in terms of natural resources needed to build them. However, the cost will probably plummet – look at the prices of our laptops and mobile phones, becoming cheaper for more.

At present a simple robot costs about the same as a medium-sized car – and these can only work at simple tasks and only at the same depths as a scuba diver. For deep-sea work and more complex activities you are looking at a few million dollars, plus the topside vessel, crew – ie a multi-dollar ship.

But sadly, the nature of man will probably require armies of robots just to defend one nation’s “rights” – and we all know that many advances in technology come as a direct result of the development of war machines.

So, you can imagine vast armies of soldier robots defending huge groups of worker robots on the ocean floor in the not so distant future! And, look at the computer games our youngsters are playing right now – the operators of the future.

Communication with the robots

At present, we envisage that robots will always need cables for communication power and power. Water does not permit us to transmit information fast over more than very short distances – a few tens of yards.

So, if there are a number of robots, they will need underground links. Imagine it as like an up-side-down tree with branches diving down from a trunk where sits the operator, safe and dry, on land or in the control vessel. The bigger the tree the fewer medium-sized control centres will be needed.

And the robots themselves will have to build and maintain this complex structure.

How safe is energy storage in tanks?

Leaks and tank collapse

Despite the very considerable amount of energy (equivalent to 3 atomic bombs per tank) stored in the tank this a safe method of storage. Even if the roof of the tank collapsed the sir would slowly bubble up, cool down and start to freeze the sweater to ice. This might result in a slurry of ice-cold water, most of the rest of the energy would have been used up in producing this. And so, the sea might be perturbed – and we are not sure how by how much. Unless you were in a ship right above the leak you should be unaffected.

In fact, this is unlikely to happen often because of the tank’s small overpressure. However, if turbines and compressors were at the surface, they would be destroyed by a huge pressure leak. But if they, too were underwater at a similar pressure they would be perfectly safe.

Small leaks will occur thus releasing tiny amounts of pressure –so one might see a few ice-cubes bubbling to the surface from time to time.

Cold at sea depths

Because it is generally cold at the ocean’s depths it makes storing energy there very safe. However, managing heat flow does limit the safe sites for the tanks and they would most probably be sited just beyond the continental shelf. The shelf would give us places to build the infrastructure like heat exchangers and auxiliary storage tanks without the need for enormously long cables and pipes.

The slope would be useful in helping to regulates the controlled ascent and release of the compressed air thus releasing the energy in a controlled fashion and avoid icing problems. It would also help to prevent energy wastage by minimizing temperature differences.

Regulating the heat flow presents challenges to which there are various solutions – but exactly how this will be done is yet to be formulated.

Brine lakes under the sea

Another way to store energy under the sea is to create brine lakes. Very salty water is heavier than less salty water and will sink, and if we dump it quickly enough to prevent mixing, we can form undersea lakes.

So, if we could build two artificial brine lakes at different levels of the seafloor, we could store energy by pumping brine from the lower lake against gravity to the upper one and to extract the energy drop the brine back to the lower lake.

Energy from the deep from brine lakes?

We could in theory store huge amounts of energy by the use of brine lakes. for example, a pair of underwater brine lakes the same size as Lake Mead, one placed on the shelf and one on the deep seafloor, could store four times the energy of Lake Mead.

And nature has its own way to manufacture underwater brine lakes by the saturation of water from large salt outcrops on the floor. Deepwater brine lakes have been found in the Red Sea, the Gulf of Mexico and the Eastern Mediterranean.

Final thoughts about energy from the deep

Time and fossil fuels are running out. We need to keep up and develop accessible, long term sources of energy and energy storage. Energy from the deep provides us with an opportunity to enable our grandchildren to benefit from sufficient and safe energy without too much further damage to our world.

Energy from the deep? Challenges lie ahead! Are we up for them – or will they floor us?

%d bloggers like this: