Rolling Blackouts

CALLD
CALLD Solar Expert Posts: 230 ✭✭
Ok, so for those who were wondering why I chose an off grid system over grid-tied when I have a grid at my disposal this is it.

Africa's largest and most advanced power utility has finally started to crack under pressure. We are in our third week of regular rolling blackouts. Eskom, a power utility with 42,000MW of installed capacity is currently unable to meet a demand of just over 30,000MW. It is currently in "stage 3" of load shedding which it says is needed to remove up to 4,000MW of load from the grid.

My question is how far can load shedding actually help? At what point does demand actually exceed supply by such a large margin that total grid collapse is inevitable? What happens for example if an entire power station, approximately 4000MW which is a typical size for one of Eskom's coal fired stations, decides to trip? Does a cascading failure result? Would the entire grid collapse? Or are modern power grids able to protect themselves?

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Rolling Blackouts

    I actually know a family that lives in South Africa. I've been hearing about the Eskom disaster for some time now. Corruption at the top has left the power company without the funds to maintain and upgrade infrastructure, or even to keep the gas burners on. It's absurd, and it doesn't look like it will be fixed any time soon.

    Your suspicions about the viability of "load shedding" are correct. Especially in that when the power returns to any given circuit it is going to have to deal with the fact everything has been left turned on: one big start-up surge. This can instantly take down the circuit that was just re-energized.

    If they really want to deal with this they are going to have to find a way to 'permanently' shed loads and take the strain off an aged and failing system. That means co-operation from all utility customers, which is not easily had or ensured, and management knowing what they are doing. That last point seems even less likely to occur.

    Homes and businesses could install large amounts of GT solar to reduce their individual effect on the grid, but no one has the money for it do they? So what is left? Power Police removing 'unnecessary' devices from peoples homes? "Sorry; you're only allowed one light bulb and a refrigerator"?

    Frankly I don't think you've got anyone in the country capable of evaluating the situation properly and coming up with a viable plan to get past this point. Prepare for anarchy.
  • CALLD
    CALLD Solar Expert Posts: 230 ✭✭
    Re: Rolling Blackouts

    Yeah it's pretty dire! Propaganda is also the biggest problem. We are told something is being done about it but see something different. 2 x 4800MW power plants have been under construction for the last 7 years but both are nearly 4 years behind schedule for various reasons. Had they been on schedule we would not be experiencing any rolling blackouts.

    Lack of information is a big problem, typically the warning of impending blackouts is given an hour or so before they start.

    Anarchy? Well hopefully not as Africans are pretty used to blackouts.

    Power police? Well they would be wise to start with all the illegal power connections in the townships (slums). Obviously people who make illegal power connection use whatever they want as they are not paying for the electricity anyway.
    I would love to see what the "power police" have to say when I tell them I'm making my own power so "get lost!"
  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Rolling Blackouts

    What is the explanation for the discrepancy between the installed capacity and their ability to only meet about 70% of it? Undersized (or permanently offline) transmission lines? Plants that are permanently offline? Sounds like they don't need those new plants, just the ability to get the rated capacity from their existing infrastructure.

    Even here in the US I feel the same way you do - I'd rather have an offgrid system than grid-tie, no matter the efficiency gains lost by doing it.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • CALLD
    CALLD Solar Expert Posts: 230 ✭✭
    Re: Rolling Blackouts
    techntrek wrote: »
    What is the explanation for the discrepancy between the installed capacity and their ability to only meet about 70% of it? Undersized (or permanently offline) transmission lines? Plants that are permanently offline? Sounds like they don't need those new plants, just the ability to get the rated capacity from their existing infrastructure.

    Even here in the US I feel the same way you do - I'd rather have an offgrid system than grid-tie, no matter the efficiency gains lost by doing it.

    Because of sheer bloody incompetence that's how. Have a look at this tip-off someone just shared on my Facebook page:

    Duhva Power Station turbine smash.
    Sweeping the **** as well as the taxpayer’s money under the carpet!!

    Not really intended for the public, BUT, amazing how pics like these can get out even after Eskom put a blanket of secrecy around the whole incident. Eskom like hiding stuff like this?

    So I found out what happened at Duhva power station and the busted turbine.
    They were doing a test of the turbine overspeed protection system, and in short, the protection did not kick in. Conventional wisdom tells me that there should be a better way to test a protection system than to try and destroy the turbine and see if it feels like protecting itself, but that’s basically what they did.
    The turbine has a governor valve which controls the amount of steam coming into the turbine In order to keep it running at the right speed (3000 rpm for our grid frequency) and then it has a main isolation valve to shut the steam off completely. The protections systems (of which there are 3 independent systems, and a dude with his finger on the emergency button) are supposed to close this main isolation valve in a fraction of a second when the turbine overspeeds.
    So they get ready for the test, they dump a helluva lot of steam onto the turbine, speed starts going crazy, it went from 3000 RPM to 4500 RMP in ten seconds (they are generally only designed for 10 to 15% overspeed, all three protection systems should have kicked in by the time you get to 110%). Anyway, I don’t know why, but all three systems failed, and the dude with his finger on the manual trip button wasn’t at his post. So the result was a big bang, some fire and a lot of steam going where it shouldn’t go.
    Scary thing is Duvha has a shared turbine hall. All six units are placed in one long straight stripe, with no missile shield between them. And if you look at the third pic you can see how big that shaft is, if that landed on another turbine it would have destroyed that too. They are very lucky they didn’t lose the entire station.
    So anyway, what gets reported in the news? “Unforeseen maintenance” at one of the units at Duvha requires it to remain shut down for 18 months. understatement of the century in my book. But you shut off the containment ventilation system at Koeberg for one hour and a radiation alarm goes off, then it’s a front page news national crisis. I give up.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Rolling Blackouts

    a little more accurate statement:

    Johannesburg - It may cost Eskom up to R3bn to replace the turbine generator that spun out of control and burst during a maintenance test
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    Re: Rolling Blackouts
    techntrek wrote: »
    What is the explanation for the discrepancy between the installed capacity and their ability to only meet about 70% of it?

    I think Bill or someone I trust anyway, said as much as 50% of generated capacity is lost in transmission! I was surprised since they use so much higher voltage, but I guess they have a lot longer wire runs!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    Re: Rolling Blackouts

    Here is (I think) an original source for CALLD's post with some pictures:

    http://www.watkykjy.co.za/2011/03/eskom-se-duvha-powerstation-kaboom/

    Note there is some bad language in Afrikaans if you speak it, or run it through a translator.

    Before:

    Attachment not found.

    After:

    Attachment not found.

    Hope nobody was killed:

    Attachment not found.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    Re: Rolling Blackouts

    Regarding utility losses...

    50% is about the best efficiency from gas turbines (fuel in to electricity out). Coal and others are less efficient.

    Regarding transmission/distribution losses--I did not quite remember saying that (although I probably did). But I wanted to double check. It appears what I remembered was wrong. Some quick searching seems to indicate total grid electrical efficiency in the range of:

    http://blog.schneider-electric.com/energy-management-energy-efficiency/2013/03/25/how-big-are-power-line-losses/
    Electricity has to be transmitted from large power plants to the consumers via extensive networks. The transmission over long distances creates power losses. The major part of the energy losses comes from Joule effect in transformers and power lines. The energy is lost as heat in the conductors.

    Considering the main parts of a typical Transmission & Distribution network, here are the average values of power losses at the different steps*:
    • 1-2% – Step-up transformer from generator to Transmission line
    • 2-4% – Transmission line
    • 1-2% – Step-down transformer from Transmission line to Distribution network
    • 4-6% – Distribution network transformers and cables
    The overall losses between the power plant and consumers is then in the range between 8 and 15%.
    Is it the biggest challenge?

    This must not be mixed up with the efficiency of power plants like nuclear, coal-fired or natural gas turbine. These technologies are based on a thermodynamic cycle, which efficiency is in the order of 35%. This means that the combustion of coal, for example, will produce heat, which will be converted into mechanical energy and then into electricity.

    Given that California ships its power in from other western states and Canada, I would have to think we are looking at a handful of percentage points more losses--But just a guess.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    Re: Rolling Blackouts

    I did not intend to misquote you, perhaps I was thinking of an energy conversion discussion.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    Re: Rolling Blackouts

    Not a problem--I may have said 50% losses in distribution. I just don't remember.

    In any case, I wanted to confirm one way or another what the "real numbers" were.

    Now we both know.

    -Bill :D
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Rolling Blackouts

    I've just been told by my friend in SA that Eskom predicts these conditions will continue for 5-10 years. That definitely makes investing in battery-based back-up power worthwhile.

    Meanwhile the company advises you buy candles and a generator. Wrong.
  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Rolling Blackouts

    Wow, that last picture is incredible. Like someone shot a giant-sized shotgun.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Rolling Blackouts

    check out the pictures BB linked to, bloody scary what happened!

    add: wait for the page to stabilize and then scroll down (or use 'down' arrow)
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    Re: Rolling Blackouts

    Yea, there are some more pictures at the link.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset