EEVblog2 World's Largest Solar Array - HVDC Transmission Calculations...

[GreggD]

I have seen long distance transmission lines that use one wire and earth as the other.
At each end a array of electrodes are put in the ground.
I assume that earth under the water is very conductive.

Big cost savings ?

[nctnico]

I'd be surprised if there won't be bigger solar arrays in Australia in the future. Maybe 10 times or even 100 times bigger than this one.

What I'm missing is the cost per kWh in the HVDC calculations. I'll take a stab at it:

Over here ( https://en.wikipedia.org/wiki/Australia%E2%80%93ASEAN_Power_Link) I see the the cable costs about US$10 billion and has a capacity of 2.2GW. But if they plan to transport 1.21GW on average per Dave's calculation then it seems they are not using the full capacity.

According to this report an under water cable has a guaranteed lifetime of 25 years and can work up to 40 years:
https://publications.jrc.ec.europa.eu/repository/bitstream/JRC97720/ld-na-27527-en-n.pdf

25 years means a total amount of energy of: 1.21GW * 24*365.25 * 25 = 265 TWh
40 years means a total amount of energy of: 1.21GW * 24*365.25 * 25 = 424 TWh

Divide the costs by the amount of energy gives a cost price of US$ 0.038 per kWh for 25 years and a cost of US$0.024 per kWh for 40 years. Ofcourse this number is excluding ongoing maintenance like monitoring and repairs.

Some other interesting reading material on HVDC cables:
https://www.researchgate.net/publication/282546305_Review_of_high_voltage_direct_current_cables/link/5641e97008aec448fa61f3b6/download

[thm_w]

Daves calculation was single cable, so he must have assumed earth would be the return. "Many high-voltage direct current systems (HVDC) using submarine power cables are single wire earth return systems."
It was left out of the efficiency calculations, but it sounds like it would be low enough that it would not have a significant effect. You'd just need massive ground rods/grids.

https://en.wikipedia.org/wiki/Single-wire_earth_return
https://communities.theiet.org/discussions/viewtopic/1037/25348

[Circlotron]

You’d want to be careful where you put the earth connection. Given the amount of DC current that would be flowing, electrolysis might be quite a problem for metal pipes etc for quite some distance around. Hopefully the connection would be some kilometres offshore.

[nctnico]

In the grand scheme of things a loss of 10% is not that bad from a cost perspective. However what is tricky with these cables is the thermal design. One of my family members is an expert where it comes to anything to do with thermal management and he has worked on under water cables as well. Much to his own surprise under water cables (which usually are dug a bit into the sea floor and/or get covered with silt over the years) are thermally well insulated. Very counter intuitive given the huge amount of water nearby.

[Circlotron]

Enough renewable electricity to power more than 3 million homes a year.

[nctnico]

Enough renewable electricity to power more than 3 million homes a year.

Actually it is not far off. 1.21GW * 365.25 * 24= 10.6 TWh / per year.
For 3 millions homes that gives 3500kWh per year per home. This is a reasonable number for a small household like an appartment in a very densily populated city like Singapore.

[tszaboo]

For an 8 GW 40 km link laid under the English Channel, the following are approximate primary equipment costs for a 2000 MW 500 kV bipolar conventional HVDC link (exclude way-leaving, on-shore reinforcement works, consenting, engineering, insurance, etc.)

Converter stations ~£110M (~€120M or $173.7M)
Subsea cable + installation ~£1M/km (~€1.2M or ~$1.6M/km)
So for an 8 GW capacity between Britain and France in four links, little is left over from £750M for the installed works. Add another £200–300M for the other works depending on additional onshore works required.[37]

Wikipedia

So that 3800 KM cable would cost about 4B EUR to make.
10 GW system about 8B EUR.
About 100EUR/kWh for the battery would mean 3BEUR
The land is about 1000 AUD/ha, as far as I can see, if you buy a farm with cattle and everything. For 12000 ha... What a joke...

But I think we can estimate the cable thickness and losses from the economical perspective. We know, how much utility scale solar costs, it's about 0.8EUR/W.
This is designed by engineers, and they know what they are doing. So you are not going to invest about 4B into a second cable, to save 10% energy loss. Why? Because you can buy 10% extra energy capacity for 800M. Maybe they still going to install a second cable for redundancy reasons, calculating the cost of power loss is harder.
This could have actually much smaller cables, and higher losses ( maybe even higher than the estimated 20% in the video), because the solar capacity is cheaper than the cable.

[Circlotron]

Enough renewable electricity to power more than 3 million homes a year.

Actually it is not far off. 1.21GW * 365.25 * 24= 10.6 TWh / per year.
For 3 millions homes that gives 3500kWh per year per home. This is a reasonable number for a small household like an appartment in a very densily populated city like Singapore.

You may be quite right that it could power 3 million homes. My point was that the phrase "3 million homes a year" makes no sense.

[nctnico]

Nahh, you have to ignore the obvious language mistakes modern reporters make. The context is clear.

[3roomlab]

ah this topic, i could shed some light about.

You may be quite right that it could power 3 million homes. My point was that the phrase "3 million homes a year" makes no sense.

no, it is about 1.4million homes. 3million vs 1.4million is not a small difference.

this is the list of local power stations
https://en.wikipedia.org/wiki/List_of_power_stations_in_Singapore
it gives 12.3GWp (or >100TWh/year)

the government also buys power from malaysia
https://www.channelnewsasia.com/news/singapore/singapore-import-electricity-malaysia-two-year-trial-energy-13373336

but, there are 2 things weird. they already have surplus generation, they buy power from malaysia. which has more than 10 major blackouts a year. so why did they buy it? and then now some oz company is hyping a sale?
the local malaysian celebrity makes a profanity ladden (>1million views on YT) fxxking the authorities about the black outs ("namewee fxxk TNB malaysia".)

there is a long list of singapore government pdfs that is searcheable, it puts this oz solar thing in a weird spot. are they selling power? or harvesting gullible investors?

if someone in asia try to sell in reverse the same format of power to oz, will it be highlighted as a big news? or big scam?

[station240]

Basslink HVDC link between Victoria and Tasmania is single pole 400 kV DC with metalic return path.
290km of it is undersea.
So two cables, to prevent the usual issues with using Earth as a return path.

Design/engineering document on Basslink here
https://www.ptd.siemens.de/IEE_HVDC_0306.pdf

[nctnico]

ah this topic, i could shed some light about.

You may be quite right that it could power 3 million homes. My point was that the phrase "3 million homes a year" makes no sense.

no, it is about 1.4million homes
the local population is about 3million + foreign labor  >5million

Doesn't matter. Number of homes is used to translate a large number into something the general public can relate to.

(edit : for $10b cost of the cable i can probably build a humongous solar farm in johor malaysia and help stop them having more blackouts in future
they are less then 100km away and i dont need HVDC

Why this is a bad idea...  think about  farm land and rain forrest
With similar reasoning you could project the solar panels in Indonesia but then you'd need to take away a huge chunk of rainforrest or farm land. Both are a no-go.