Hacker News Reader

Comment by bin_bash | Hacker News Reader

Solar doesn’t provide nearly as much energy and for desalination you need a surprising amount.

Nuclear is a great use-case since the problem with nuclear is it needs a constant water source. If you’re desalinating you’ve got that problem covered.

View on HN

Solar doesn’t provide nearly as much energy and for desalination you need a surprising amount.

That statement doesn't make any sense to me. If you need more power, install more panels. Space certainly isn't an issue in like northern Africa. It is cheaper to order a gigawatt or more of solar panels than building a new nuclear reactor, and faster to set up too. Even Germany today has way more solar capacity than it ever had in nuclear, and it is less a great place for solar than Africa.

> Even Germany today has way more solar capacity than it ever had in nuclear

That's because it never had much nuclear capacity, not because it now has a lot of solar

I don't know what you mean by "much", but Germany has a peak power capacity of 56 GW of Solar. On good days the output comes close to the nuclear output of France, which is mostly nuclear in power production. German wind power occasionally eclipses French nuclear power production.

The vast majority of our freshwater comes from sources that cost us effectively zero in energy: the water cycle moves water towards higher elevations and it flows down towards our populations. Worst case scenario, water in ancient underground reservoirs is pumped to the surface.

If we had to desalinate all that water and actively distribute it instead, it'd be a significant fraction of our current global power consumption. The power sources need to be concentrated near the desalination plants and at least half the world lives 100km+ away from a coastline. At 3 kWh per m^3 of water[1] and ~3.5 m^3 per person per day [2], that's an extra ~3800 kWh per year, which would increase per capita energy consumption by 25-30% [3] in the United States just for desalination.

We have enough challenges replacing existing power infrastructure with solar and wind. Placing the burden of desalination on top of that is unrealistic, especially since the NIMBY fight over solar installations of that size would probably be just as fierce as for a nuclear reactor.

[1] https://res.mdpi.com/d_attachment/energies/energies-12-00463...

[2] https://www.usgs.gov/special-topic/water-science-school/scie...

[3] https://data.worldbank.org/indicator/EG.USE.ELEC.KH.PC?locat...

I have never claimed, that we would replace all fresh water used on this planed by desalinated water. This certainly is neither feasably nor necessary. At best, it can be an important contribution to water supply in many regions.

I was only answering to the original post which suggested we would build nuclear power plants to desalinate water. There I commented that solar would be cheaper (and more environment friendly) for the same task.

The Sydney desalination plant is entirely powered by Wind:

https://www.sydneydesal.com.au/caring-for-the-environment/10...

Nuclear power is severely restricted and building a nuclear power plant in a country dealing with active terrorist movements is probably something to be avoided.

Solar is relatively inefficient, but it can't be used to build a dirty bomb or worse. With large patches of uninhabit{ed,able} desert, many African countries have more than enough space to build large solar farms if they can find a solution to the sand blowing onto the panels.

Does nuclear need fresh water? I'd imagine salt water would wreck all the equipment, and you probably don't want to use up all the fresh water you generate...

You need very pure water for most portions of a nuclear power plan.

that'd depend on the reactor type, no?

Not really. Pure heavy water along with pure uranium and pure CANDU reactors are imported components. The quality of cooling water and feed water doesn't matter much.

Remember, nuclear power plant is merely a very large heat engine. The main problem is terrorism there.

The turbines do but you can recycle much if not nearly all of that water by cooling the steam and condensing it, which you could use sea water to heat exchange to for it.

The water is just there for thermal mass to conduct waste heat away from the condenser. The water that gets heated by the reactor core and turns the turbines is isolated and highly purified, since many of the internals can only be accessed during refuels. Some designs go further and separate the reactor coolant system from the steam generator to prevent contamination, but AFAIK there isn't a single commercial design that allows outside water to feed into the reactor cooling or power generation systems. The parts of the condenser that touch the external body of water are basically just blocks of metal that have to be scrubbed on the outside from time to time.

You have heat exchangers between saltwater and clean freshwater that circulates through the sensitive parts of the plant.

> Solar doesn’t provide nearly as much energy and for desalination you need a surprising amount.

Are there numbers for this? One one hand solar might provide more energy than nuclear if you're only interested in heat generation, but on the other hand using heat to desalinate (ie. boiling water) is also less efficient than using reverse osmosis.

Last I checked Algeria has a bit of solar energy hitting it. :)

Reply on news.ycombinator.com