Quote from: kerick on October 13, 2024, 08:35:09 PMSince you are in the power transmission field maybe you could answer a serious question for me. How efficient is it to transmit electricity for long distance? I just read about how a hydroelectric dam in Yosemite NP delivers power 136 miles to San Francisco. How much energy is lost in the process? I just want to be able to speak intelligently about the subject.

Obviously, this is a bit complicated. If not, everyone and his aunt would be doing it, but let's draw up a few basic lines at least:

Yes, there are transmission losses as a result of different obstacles and bottlenecks in the transmission system. Drawing power through any cable/line (conductor) is a bit like drawing lemonade through a straw. The longer and narrower the straw, the more you'll have to suck to get any. Consistently, the longer or thinner the connection, the more energy losses you'll have. But there are ways to at least make things less onerous. Obviously, you can build thicker conductors - to a degree - but after a while, that way will turn cumbersome and expensive. Then, as power equals current times voltage (P = I x U), you can up the voltage, that way lowering the current. And it is the current that is dimensioning when it comes to conductors, so that will counteract the need for thicker conductors
Then, you can use other technologies to further minimise transmission losses, such as serial capacitors on long uninterrupted lines in HVAC systems, or HVDC that does away with the entire AC transient problem, and so forth. And in some future, IF we can solve the problem of supra-leading materials, maybe we actually will be able to move even further towards a loss free system. But we're not there yet. Current level of losses is in the region of 2-7%, depending on many factors, as seen above. But 136 miles for supplying a big city is nothing.

So, long distance lines are always forming "bottlenecks", and ideally, you'd like an as short a connection between your power production facility and your consumption/load as possible. But power production is as a rule more efficient the larger the production facility gets, so there will be trend towards fewer and further between. Consumption, on the other hand, is widespread as every dwelling, every little workshop and even your odd streetlight in the middle of nowhere will need power. Hence, there will always be a need for longer lines. Also, interconnecting these big producers will be beneficial for everyone, because there's maintenance down periods, and sometimes technical problems, that both will lead to intermittent availability. The impact of that intermittence can be very much mitigated by such interconnections, allowing facility A and B to cover for facility C when the latter needs an overhaul, or something. There is, however, also a limit to the losses you're prepared to accept, and perhaps more problematic, to the amount of sheer conductors you actually can afford and operate over longer distances. This is the main reason why Europe hasn't PV-panel-covered that little 20 by 20 km area in Sahara that's all you need to supply all of Europe's power need. The amount of power to be transported is too big, and the distance to transport it is too long. For now. When there are useable supra-leaders available - Hold my beer..

In a larger system, this is amplified, and even a big grid, connecting many consumers and several big producers (a Transmission System Operator, or TSO), will have huge gains by being well connected to it's neighbouring TSO's, thereby being able to "borrow" capacity over these borders when necessary. The US system delivered one of the best/worst recent reminders of that during the winter storm in Texas a few years ago, when large parts of the state were in blackout for days, even up to a week, leaning people to actually freeze to death in their own beds. Compare that to NW Texas and Oklahoma, that was hit by the same weather but connected to another TSO, instead of those major blackouts experiencing only short interruptions of about 30 minutes each. The problem here was that Texas main TSO (ERCOT, if memory serves) over many years has been staunchly independent, refusing interconnections to neighbouring US TSO's, whereas the TSO in OK has not, instead it's seen to that it could get support from both the west and the east during this stress event. The following map shows that in an very clear way.



So - long powerlines are important. Nationwide connections are important, even if they're expensive and cause losses. Continental connections, even, are important.

Right. Now I've spilled precious time on work again..     

Wow, an erudite treatise on the subject if ever I read one! 

While I knew the basics from way back, that's a superb explanation of the issues involved, thanks very much.

Adding insult to injury, here's an even better US TSO map:



Greens and blues are well interconnected within their own main colour, basically being able to import 20-30% of their internal max load at any time. Between the green and blue areas, a transfer of 10-12% is possible but from ERCOT (black) to anyone - only ca 1% of what Texas uses. Not ideal.

Quote from: Pellson on October 14, 2024, 04:18:02 AMAdding insult to injury, here's an even better US TSO map:



Greens and blues are well interconnected within their own main colour, basically being able to import 20-30% of their internal max load at any time. Between the green and blue areas, a transfer of 10-12% is possible but from ERCOT (black) to anyone - only ca 1% of what Texas uses. Not ideal.

Texas doesn't want to be subject to Federal regulations when it comes to the power grid, which is why they don't interconnect with anyone...which is why the "Reliability" in the ERCOT acronym (Energy "Reliability" Council of Texas) has become a joke of late. 

Quote from: scooter on October 14, 2024, 04:26:16 AMTexas doesn't want to be subject to Federal regulations when it comes to the power grid, which is why they don't interconnect with anyone...which is why the "Reliability" in the ERCOT acronym (Energy "Reliability" Council of Texas) has become a joke of late. 

Yep. And above, I've explained in layman terms why that's about as daft as most of the other "independency" ideas within any given union..
Buuuut I'l leave that particular discussion not, for the sake of Chris's mental wellbeing.. 

You lost me at "this is a bit complicated"... 

Quote from: zenrat on October 14, 2024, 04:40:58 AMYou lost me at "this is a bit complicated"... 

                

Quote from: zenrat on October 14, 2024, 04:40:58 AMYou lost me at "this is a bit complicated"... 

OK.

• Powerlines will incur minor losses to the power transmitted through them. However, the penalty of not being connected is far less than the penalty of being distantly connected, so if you can build a power line - do so.
• Texas during the winter storm in 2021 was a more or less living proof of the above

Clearer? 

Quote from: Pellson on October 14, 2024, 04:32:49 AM

Quote from: scooter on October 14, 2024, 04:26:16 AMTexas doesn't want to be subject to Federal regulations when it comes to the power grid, which is why they don't interconnect with anyone...which is why the "Reliability" in the ERCOT acronym (Energy "Reliability" Council of Texas) has become a joke of late. 

Yep. And above, I've explained in layman terms why that's about as daft as most of the other "independency" ideas within any given union..
Buuuut I'l leave that particular discussion not, for the sake of Chris's mental wellbeing.. 

Oh I most definitely concur.

Quote from: Pellson on October 14, 2024, 04:32:49 AMBuuuut I'l leave that particular discussion not, for the sake of Chris's mental wellbeing.. 

Thank you 

Thanks for that explanation!
2-7% loss is far less than the 50% on long runs I was told many years ago. Also the interconnection is vitally important. Thanks again.

That brings back memories from fifteen years ago when I was at college doing an HNC in Electrical Engineering

Gondor

Yet more proof, if it were ever needed , that no matter how complex the question, there is someone here who has the appropriate knowledge .

Quote from: Pellson on October 14, 2024, 05:15:51 AM

Quote from: zenrat on October 14, 2024, 04:40:58 AMYou lost me at "this is a bit complicated"... 

OK.

• Powerlines will incur minor losses to the power transmitted through them. However, the penalty of not being connected is far less than the penalty of being distantly connected, so if you can build a power line - do so.
• Texas during the winter storm in 2021 was a more or less living proof of the above

Clearer? 

Mate, my degree is in Mechanical Engineering.  I barely know how to wire a plug.  But thanks for trying.   

Quote from: Rheged on October 14, 2024, 11:11:01 AMYet more proof, if it were ever needed , that no matter how complex the question, there is someone here who has the appropriate knowledge .

Righttttttttttttttt.........would someone care to explain woman to me ?