37
votes
Accepted
Why does it take so long to restart a nuclear power plant?
When a reactor is shut down the core produces much less heat, but they do still produce heat through a mechanism known as decay heat. The fact that the core is producing less heat means that the ...
- 3,525
15
votes
What are the disadvantages of concentrated solar thermal power?
There are no silver bullets when it comes to decarbonising the grid. That's good news: it means you can stop looking for one, and accept that every form of generation has its pros and cons.
...
- 3,701
13
votes
Why does it take so long to restart a nuclear power plant?
Xenon is a result of the nuclear reaction and a neutron poison. If you don't wait for the xenon to decay, it eats up too many neutrons and you can't go critical. They always say "there are not ...
- 965
10
votes
What are the disadvantages of concentrated solar thermal power?
Everything we do as humans has consequences of some sort. Although not a huge downside (in my opinion), critics have often cited the plant's supposed adverse effects on wildlife:
Wikipedia Article:
...
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9
votes
What are the disadvantages of concentrated solar thermal power?
In the UK, the sun does not shine every day. We also need the most power in winter when the sun shines the least.
Therefore every solar power station must be backed up by anther power station that ...
- 191
7
votes
Why does it take so long to restart a nuclear power plant?
The answer really boils down to two factors: safety and testing. I'm going to give a generic summary of these two things below, but the real answer is quite complicated.
The crux of nuclear plant ...
- 3,587
6
votes
Why aren't gravity batteries everywhere?
So, this battery costs US$70, weighs 406 grams, and holds around 200,000 Joules of energy.
To get the same energy from that weight as a "gravity battery" you'd have to pick it up over 49 kilometers ...
- 2,228
5
votes
Accepted
Why are both conductors in a High Voltage Direct Curent powerline isolated from ground?
Because they're both live
Just because you see multiple wires doesn't mean they are carrying different things. They are frequently paralleled for more ampacity.
It's perfectly common in HVDC lines to ...
5
votes
Why are both conductors in a High Voltage Direct Curent powerline isolated from ground?
There are a few possible reasons.
Elimination of electrolysis problems with ground connections.
Elimination of variations in ground resistance.
Grounding one of the conductors on the HVDC line might ...
- 8,449
5
votes
Why aren't gravity batteries everywhere?
Consider 1 kWh = 1000 W * 3600 seconds = 3,600,000 J.
1 kg lifted 1 m = ~10J.
Let's use 1 metric tonne. 1000Kg. So we get 10,000 J per meter of elevation.
3,600,000 / 10,000 = 360 meters. Around ...
4
votes
Accepted
Why shouldn't we put high voltage cables physically underground?
Your four drawbacks are very good reasons for not laying cables on the ground and just covering them with soil or "stuff".
Erosion will be a major issue. Exposed cables would be a safety hazard to ...
- 9,517
4
votes
Accepted
What, roughly, are the characteristics of nuclear power in grid management?
In the US, Nuclear is used to base load the grid.
As implemented in the USA, Nuclear energy has very high fixed costs and relatively low variable cost. So it is in the utility's interest to run their ...
- 4,810
3
votes
Expected power increase when replacing old (>20 years) wind turbines
Wind turbune efficiency is limited to 59% by Betz law
Modern turbines are close to this limit, about 75% of optimum. Older turbines, that are also of the same type, will have almost the same ...
3
votes
What are the disadvantages of concentrated solar thermal power?
Concentrated solar power plants are best located in isolated areas that receive a lot of sunshine all year round, which basically means arid or semi-arid regions. Most of these regions don't have ...
- 9,517
3
votes
At what cold ambient air temperature will power lines fail?
Here are some pylons in Norilsk, Northern Siberia, where temperatures get down towards -50°C
(source)
It's all a question of design and engineering: pylon spacing, the range of max and min ...
- 3,701
2
votes
Why shouldn't we put high voltage cables physically underground?
I do not know the laws in your country, but the key is "risk assessment". And the risk we are talking about is the risk of killing someone, not the risk of the cable being damaged.
Irrespective of ...
- 7,489
2
votes
What's the history of the 345 kV voltage level in power transmission?
With the high voltage AC power lines, there are trade offs between losses due to resistance in the wires, where the higher voltages are better and losses due to capacitance to the air, etc. where ...
- 965
2
votes
Power consumption of mining rig?
Since I lack the reputation to write comments:
The electricity cost of mining is way higher than the earnings. Small scale mining is not profitable anymore for a long time already, mining farms have ...
- 1,673
2
votes
Accepted
What is the specific issue with frequency fluctuation in the grid?
A 1% shift in grid frequency will shift the running speed of every AC induction motor connected to it by 1%. Factory machinery and AC-powered clocks would all slow down, with potentially disastrous ...
- 12.2k
2
votes
Why aren't gravity batteries everywhere?
Are there some shortcomings that I am missing here?
Yes there are a couple of things you have missed.
Firstly I will deviate slightly from your question but I believe this is relevant.
The need for ...
- 308
1
vote
Expected power increase when replacing old (>20 years) wind turbines
Larger turbines have to be spaced further apart. See Sustainable Energy Without the Hot Air by David MacKay. He gives a figure of 2 W/m2 although this may have improved a bit since his book was ...
- 8,449
1
vote
What, roughly, are the characteristics of nuclear power in grid management?
Re: load following, from Wikipedia
Modern nuclear plants with light water reactors are designed to have maneuvering capabilities in the 30-100% range with 5%/minute slope. Nuclear power plants in ...
- 1,367
1
vote
Simple clarification about EV charging
The listing in the provided link is a summary of generally accepted sources of power for EV charging systems. Your question appears to be what is allowed by those sources, which really is not related ...
- 6,282
1
vote
Simple clarification about EV charging
On a 230 V system 16 A would be the circuit breaker rating for one circuit with a couple of sockets on it. A typical cooker would be 35 A. In Ireland the traditional connection is single-phase 63 A.
A ...
- 8,449
1
vote
Accepted
Do high votlage transmission lines disturb other electrical devices?
Generally, no. Transmission lines can act like antennas, but they operate at around 50 Hz. The wavelength of a 50 Hz EM-wave is $6\times 10^6$ m. In order to effectively couple that energy, you'd have ...
- 297
1
vote
Why shouldn't we put high voltage cables physically underground?
When we had to run HV lines to a building, we put them in steel pipes 6 ft deep, covered the pipes with 2 feet of sand, then laid a foot of concrete on that and painted it red, and filled the trench ...
1
vote
Why does it take so long to restart a nuclear power plant?
They are many reasons for the time it takes to startup or return to full power operation in commercial nuclear power plants. In the US there are two main types of plants, Boiling Water Reactors(BWRs) ...
- 11
1
vote
What are the disadvantages of concentrated solar thermal power?
Some of these answers already touched on the environmental impact of CSP, I would like to add this article as a source. It reiterates on the points made by others who answered the OP's question and ...
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Only top scored, non community-wiki answers of a minimum length are eligible