EEVblog2 World's Largest Solar Array - HVDC Transmission Calculations... - Page 1
Forum section: electronics / general

author: GreggD
author_rank: Regular Contributor
timestamp: February 04, 2021, 01:50:07 pm
content: 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 ?

author: nctnico
author_rank: Super Contributor
timestamp: February 04, 2021, 09:55:27 pm
content: 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$10 billion and has a capacity of 2.2GW. But if they plan to transport 1.21GW on average per Dave's calculation then it seems they are not using the full capacity.According to this report an under water cable has a guaranteed lifetime of 25 years and can work up to 40 years:https://publications.jrc.ec.europa.eu/repository/bitstream/JRC97720/ld-na-27527-en-n.pdf25 years means a total amount of energy of: 1.21GW * 24*365.25 * 25 = 265 TWh40 years means a total amount of energy of: 1.21GW * 24*365.25 * 25 = 424 TWhDivide the costs by the amount of energy gives a cost price of US$ 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

author: thm_w
author_rank: Super Contributor
timestamp: February 04, 2021, 10:10:04 pm
content: 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_returnhttps://communities.theiet.org/discussions/viewtopic/1037/25348

author: Circlotron
author_rank: Super Contributor
timestamp: February 04, 2021, 10:26:40 pm
content: 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.

author: nctnico
author_rank: Super Contributor
timestamp: February 04, 2021, 10:30:24 pm
content: 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.

author: Circlotron
author_rank: Super Contributor
timestamp: February 04, 2021, 10:51:32 pm
content: Quote

author: nctnico
author_rank: Super Contributor
timestamp: February 04, 2021, 11:12:11 pm
content: Quote from: Circlotron on February 04, 2021, 10:51:32 pmActually 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.

author: tszaboo
author_rank: Super Contributor
timestamp: February 04, 2021, 11:39:15 pm
content: QuoteWikipediaSo 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 3BEURThe 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.

author: Circlotron
author_rank: Super Contributor
timestamp: February 05, 2021, 12:26:29 am
content: Quote from: nctnico on February 04, 2021, 11:12:11 pmYou 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.

author: nctnico
author_rank: Super Contributor
timestamp: February 05, 2021, 12:44:37 am
content: Nahh, you have to ignore the obvious language mistakes modern reporters make. The context is clear.

author: 3roomlab
author_rank: Frequent Contributor
timestamp: February 05, 2021, 01:14:04 am
content: ah this topic, i could shed some light about.Quote from: Circlotron on February 05, 2021, 12:26:29 amno, it is about 1.4million homes. 3million vs 1.4million is not a small difference.this is the list of local power stationshttps://en.wikipedia.org/wiki/List_of_power_stations_in_Singaporeit gives 12.3GWp (or >100TWh/year)the government also buys power from malaysiahttps://www.channelnewsasia.com/news/singapore/singapore-import-electricity-malaysia-two-year-trial-energy-13373336but, 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?

author: station240
author_rank: Unknown
timestamp: February 05, 2021, 03:30:00 am
content: 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 herehttps://www.ptd.siemens.de/IEE_HVDC_0306.pdf

author: nctnico
author_rank: Super Contributor
timestamp: February 05, 2021, 10:24:31 am
content: Quote from: 3roomlab on February 05, 2021, 01:14:04 amDoesn't matter. Number of homes is used to translate a large number into something the general public can relate to.QuoteWhy this is a bad idea... think about farm land and rain forrestWith 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.