5% seems very very low. I do no think it includes the wire heat waste that are common to coal and nuclear, because according to this: https://blog.schneider-electric.com/energy-management-energy... "The overall losses between the power plant and consumers is then in the range between 8 and 15%." (I do not think the numbers have changed that much in 6 years).
One of the reasons China is pushing solar is it assumes solar is going to explode globally in the coming decades, and it wants to dominate the industry.
It is more important to control the technology of solar power than the locations. With the technology they can team up with countries that have great solar potential.
Tibet is the one place where it would make sense but only 3 million live in Tibet. There is over a billion Chinese citizens who are roughly three thousand kilometers away.
Hvdc can go a very very long way; thousands of miles economically.
500kv a.c. @ 60z starts to become impractical above 1000 miles if I recall correctly. I'll not sure how 50hz power is more or less affected on transmission, but it requires larger transformers, making each conversion step more expensive from a fixed cost perspective.
Edit:
I didn't recall correctly, looks like hvac is not very effective above 700mi, and in underground and underwater applications, far less.
First, because you need to turn it into AC eventually and it doesn't have a frequency, it makes connecting grids a snap. You can hook a 50Hz grid to a 60Hz grid or even just two 60Hz grids with different phases.
The lack of alternating means you can bury the line. HVAC will lose power when it is close to conductors (ground, water) due to the capacitive effect. It technically still happens when in the air, just to a much smaller extent.
HVAC's benefits are that it is cheap to make transformers for. It is relatively easy to kick it up to 2MV then down to 240V. The often cited reason AC won over DC is that you can transmit it for cheaper, which isn't totally true, the reason AC won is because you can transform it easier. It was much easier to generate power at 40V, bump it up to 1kV, then down to 240V. Higher voltage == less line loss.
Wikipedia said: "The electrical grid in Japan is isolated, with no international connections, and consists of two wide area synchronous grids which run at different frequencies and are connected by HVDC connections. This considerably limits the amount of electricity that can be transmitted between the north and south of the country."
That side benefit of the cheap HVAC transformers makes HVAC practical for transmission where you have many cities that you are passing by and need to distribute power to.
HVDC shines when you have a hydro plant a long distance away, with nothing in between.
If you want to pass by a bunch of cities in between and distribute power to them, it would get expensive to put a small HVDC substation “spur” at each.
Can you mix HVAC and HVDC on the same infrastructure?
Yeah, nothing really stops you from intermixing, you just need an inverter at every point where the two join.
The problem is that inverters are expensive enough that you really don't want to do it a lot. This is why HVDC is usually used for grid interconnection or underwater transmission.
If you can drop a bunch of lines down, then with AC there isn't to much of a reason not to just pump the voltage up to insane levels. The main drawback is that the higher the voltage you push out, the more AC power will want to "leak". That effectively means you need larger pole and you need a larger distance between the AC lines. This is why you can easily pick out high voltage AC lines from regular lines, they are larger towers with bigger distances between lines.
Would this mean that the future of long distance energy transmission will be underground HVDC? And we'll see the slow deprecation (over time) of overhead HVAC transmission lines through right of ways?
Doubt it. HVDC is still HV. While you could bury the lines without a bunch of loss, you also have to start thinking about insulating the lines to keep the electricity contained but also to make sure that if someone digs up the line they don't cause a situation where you'd have to kill a large portion of the grid.
A benefit of aerials is that, all things considered, they are pretty cheap to put up over land. You don't have to insulate the lines, the air does that. You don't have to worry about people digging them up, they are too high. And if the voltage is high enough, you don't generally have to worry about something bridging the lines and causing a fire.
About the only thing you need to worry about is some natural disaster taking out the tower.
What I see HVDC being used for is joining the various grids of the world to allow for power from Texas to supplement power in Idaho. A national grid would improve efficiency, especially of renewables across the time zones.
Perhaps we'll see it used more in places like California, where the land itself isn't so valuable where HVAC runs, but the risk of combustion and cost of remediation is so high it's cheaper to run HVDC underground where it can't start costly fires that bankrupt utilities.
> China is the global test bed for ultra-high voltage (UHV) transmission lines, a technology that can carry electricity across vast distances with much greater efficiency than the high voltage lines that you’re probably used to seeing.
> Since 2006, it’s built 19 of these multi-billion-dollar lines, stretching almost 30,000 kilometres and supplying 4% of national electricity demand. For comparison, no other country has a single UHV line in full commercial operation.
> But China’s enthusiasm for UHV is waning. The technology is beset by conflicts of interest between grid companies and central and local governments. The lines themselves are underperforming, and more recent projects are coming online amid a period of electricity generation overcapacity.
> This means that approvals for new lines have slowed, and grid companies are unlikely to meet their targets for new ones.
There isn't really a hard limit, the longer the cable, the bigger the losses. You can mitigate that somewhat by increasing the voltage, which is what they're doing.
So basically the distance is determined by economics. If China could install solar and cables cheaply enough, then they could compete with domestic European and American electricity. I find that doubtful though.
15% renewables by 2020... that's not a very ambitious plan given the fact that we have less than ten years to get to a completely carbon neutral world economy.
This is China, a huge, rapidly developing country so we need to keep in mind that the overall energy production and consumption will also seriously increase during that period.
In addition, currently it is not feasible to rely only on wind and solar because these are unpredictable sources. Which also means that a target (15%) here is probably an average and that the installed capacity has thus to be much higher.
They are inherently variable, but that doesn't necessarily imply that they are unpredictable. In many cases the degree of variability across a portfolio of sources can be predicted several days in advance, at least.
They are beginning to import LNG as well, but it is much more expensive to import it than to pipe in from somewhere else in gas form. They are trying to create pipelines from Myanmar and Easter Russia to make that much cheaper.
They also have to compete with next door Japan AND Korea for LNG imports, which runs up the price. China would also rather use domestic sources of power if possible.
No? The investment on nuclear power has been slowed down. But ironically, the competition from cheaper solar and wind power is one of the factors, so it might not necessarily be bad though.
Nuclear has the same problem as coal...worse even: it has huge startup costs, so you don't just shut it down when renewables are online instead. Flexible energy sources to balance out inflexible ones primarily mean natural gas and hydro with a reservoir.
My simplistic explanation, coal and nuclear power plants can take several hours to "bootup" (startup). Gas plants can startup in minutes. So when the sun goes in the clouds, or when power demand spikes, a gas plant can quickly come online unlike coal and nuclear.
Li-ion batteries requires a lot more investment than a more simple pumped storage reservoir. They are only going to be used when the latter isn’t viable.
The IPCC report said we have 12 years (2030) to cut emissions by 45%, and that we need to reach net zero by 2050. Not sure where the 10 year number is coming from.
How does this not apply to solar and wind? If anything Nuclear designs can at least build in additional cooling, but you have no way to make weather more consistent, especially in the case of runaway climate change.
And ignore the 1% failure rate for commercial nuclear power plants.
And the clean up costs.
And the waste storage costs.
And the decommissioning costs.
Nuclear doesn't make sense. Economically and ecologically.
