Is it possible to melt icebergs for water at below the cost of desalination with 1960s/1970s technology?

Question

(i'm going to use dollars for cost because i don't really want to figure out currency conversions for the in world currencies)

In this world people need water, a lot of water. But in areas that don't actually have a lot of water, so, they need to find water elsewhere. But desalination is still extremely expensive.

The technology in question is about that of the 1960s-early 1970s with the main relevant exception for this question being early semi-submersible offshore cranes. Because of this technology level, desalination is very expensive, around 10 dollars a cubic meter.

The way the process (in theory) works to get the icebergs turned into liquid water where they need to go is that of:

1. Find a large iceberg
2. Pull it to somewhat clear waters where it can be easily manipulated. Maybe 100-200 kilometers away.
3. Blast it apart with explosives into more "manageable" chunks of ~7,000 tonnes. Around the lifting limits of early large semi-submersible crane vessels.
4. Use the crane platforms to lift the broken up icebergs inside a spar platform for it to be melted. The spar platform would be partly filled with fresh water prior to being sent out so the iceberg can float in it as it's melted. The platform would be insulated to minimize heat losses to cold sea water.
5. Pump the water from the spar into a tanker to be carried off to where it's going to be used.

Now what i thought would be the biggest costs, transport & energy to melt. Would only be about 2.40 a kiloliter for transport & 15 cents for melting. But my primary concern here is if the other costs could be realistically below the 7.45 before the cost exceeds desalination.

So the question is, is it realistic for 1970s technology be able to preform the above process at a cost below $10 a kilolitre?

Cost of the equipment is comparable to our own 1970s. I don't really need specific numbers, just if it sounds possible or if there are any obvious holes in this idea.

Answer 1

No it is just too dangerous

Ice harvesting was a real thing, but no one used icebergs it was just too much trouble. Ice harvesting usually involved frozen lakes which you can you know have workers and equipment walk on at minimal risk.

Icebergs are inherently dangerous, they break, tip, and flip over which puts any workers or ships at high risk. It is hard to imagine a job more dangerous than blasting an iceberg. Iceberg explorers, people who just climb on briefly to study icebergs is already a very high risk job and they are not trying to break the iceberg.

You may think, so what if it is dangerous, the issue is you need to pay workers more to do dangerous work and you have to add losses of men and equipment in your cost.

Answer 2

The good news for you is that iceberg towing has been a thing since the 1,800's. The bad news is that, according to the same article in the link, it is just not economically feasible for most uses.

For solving droughts, the article has this to say about a project from the 70's:

Sponsored by Prince Mohammed al Faisal, a nephew of Saudi Arabia's King Khalid, the conference demonstrated that there is no shortage of ideas for using icebergs to slake the world's growing thirst. Prince Faisal's own company, Iceberg Transport International, is considering a plan to find a 100 million-ton iceberg off Antarctica, wrap it in sailcloth and plastic to slow its melting, and then use powerful tugboats to tow it to the Arabian peninsula, where it would supply enormous quantities of drinking water. The journey would take about eight months and the project would cost around $100 million, according to estimates.

The price quote is from 1977. So that's about a dollar per ton (about the weight of a cubic meter of fresh water)... 10% of the desalinization costs of your world. Sounds really good, right? Except the project lacked support and had so many technicalities to be solved that it hasn't been implemented to this day. Many other such projects had been proposed for other parts of the world, but none was ever executed even halfway through.

By the way, I didn't see it in the article, but I remember reading in other sources that one of the challenges was the amount of water you would lose on the way to lower latitudes. Towing a 100 million tons iceberg to the Middle East does not mean you end up with 100 million tons of freshwater at the destination. In this magazine article a scientist says the trip would take far longer and you would end up with nothing.

If your world has dry areas close to where icebergs are, and there are no rivers nearby, then iceberg towing might become a thing. Otherwise, look at an hydrographic map of our own world. Even in places that are largely desertic and relatively close to the poles such as Australia, there are always rivers that are close enough to make water trucks cheaper than iceberg towing.

Answer 3

No

I don't think it's possible, not for any technical reason per se, but there's a fundamental problem that you've overlooked:

Icebergs aren't pure.

Even if you tow your Iceberg somewhere, in order for it to be safe, potable water fit for human consumption - you are going to have to pass it through a number of processes to filter out any impurities or microbes.

Those processes are, for the most part, functionally identical to the processes required for desalination

Impurities could be minerals frozen in the ice, could be animal material etc.

If we are boiling the ice to get rid of these items, that would be similar to desalination. If we are just melting the ice and then passing through filters to capture these impurities, that would be similar to desalination.

This is, I believe (not a desalination engineer), where most of the cost(s) associated with Desalination come from, taking water from say 100 ppm of thing down to a safe 1 ppm of thing and then controlling/ensuring it stays at or under safe levels.

Your Iceberg is going to have those problems.

Rain water and running river water (especially down a mountain) naturally do this, which is why it's generally safe to drink.

Answer 4

Have you heard of a Fresnel Lens?

These are relatively cheap, they can be molded from glass or optical plastic, they are flat lenses that can be used to focus light. Originally used in Lighthouses, but they can be adapted to any focusing job. They can even be rectangular, with no loss of efficiency, so you can fit them in frames and cover a large surface.

These can be huge, several square meters. But even one square meter lenses would probably be manageable by humans, they don't have to be heavy.

Since you plan to fill tankers with water anyway, forget the glacier. Just set up a water farm in at either pole. post the lenses to melt ice; they are just magnifying glasses. Gather the runoff with piping; filter it if you like, fill up your tankers.

In Antarctica, there are plenty of stable spots where the ice is kilometers thick; anywhere from 2 kilometers to over 4 kilometers.

Your lenses will need some adjustments as the ice melts, to continue focusing. This gives the crew something to do while filling up the tanker. Much of that work can be motorized and automated, and monitored by camera.

Pack up your kit when your tanker is full.

Sail home. Repeat.

Before complaining about the amount of work, I think it is considerably less than the work of dismantling an iceberg. And there is much less danger involved.

EDIT: Midnight Sun and Polar Night. At the North and South poles, we have periods of 24 hour sunlight (Midnight Sun) and 24 hour darkness (the Polar Night). These alternate with each other. When the North Pole has the Midnight Sun and 24 hour daylight (during the Summer Solstice, about June 21), and has Polar Night at the Winter Solstice, about December 21.

The South Pole is the opposite. It has Midnight Sun in December, and Polar Night in June.

The total time to farm water would likely be the same between the two, we would just have water-farming seasons for the two poles. It will be most efficient to farm at the pole with the longest days and best sun.

Note that even at the equator, we can only focus sunlight about 40% of the day. At the poles, it will be better, we can produce water for more of the day in "farming season", up to 24/7. We just need to switch poles every six months. And perhaps have some significant water tank facilities in the country to even out demand.

Answer 5

Use the crane platforms to lift the broken up icebergs inside a spar platform for it to be melted. The spar platform would be partly filled with fresh water prior to being sent out so the iceberg can float in it as it's melted. The platform would be insulated to minimize heat losses to cold sea water.

1. Why lift it? Rigging lifting slings for 7000 tons on a iceberg doesn't sound trivial. Submerge your spar! Ballast it so you can float in your ice berg.

2. Why insulate? Use the sea water heat! Water has extreme heat capacity, and you have nearly unlimited amount of it available. Granted, it's not warm, but it's cheap. Simply pump as much of it as possible through pipes embedded in your artificial lake, and presto, your ice berg will be melting. You only have to power a few pumps.