<blockquote><cite>Posted By: skyewright
The 'cost' to the UK comes later in terms of buying any electricity produced (at a guaranteed price).

In 9-10 years time,-- SWAG.

Nothing deep about it Tom - we don't have the money to build it - we only buy power - they have to generate that power first

We have decided however, we need that power and as is typical of most of these transactions, we have given a basic underwriting to the cost of that power - it's exactly the same for private funded lagoons like Swansea, wind farms and solar farms all over the country and pretty well all privately funded schemes for AD gas generation etc etc

I was looking at an off shore wind farm where the strike price is over £130 MWh - makes the scale, longevity and stability of HPC look like a good deal - easy money for the funders, and no one is looking 'cos it's offshore and green

I can show you a perfectly reasonable energy from waste scheme that won't go ahead as the reliability and quality of the feedstock coming from local authorities is unattractive to the private funders - basically "If we build it, can you fuel it ?" - and the answer seems to be no - so would you put money into that ? - it's quite "green" and ticks a lot of boxes - but the LA are making demands on guarantees that are unreasonable - so my client is walking away from it - that's roughly 60MW of pretty green energy lost

Posted By: SteamyTeaYou can easily go to the old DECC website and download the appropriate spreadsheets, they are there for the taking, Just that I don't have time right now to look at them all (summer being my busy time).
https://www.gov.uk/government/organisations/department-of-energy-climate-change/about/statistics

Finally got to look at this. As I suspected, it shows about 70% of energy is space heating, 14% appliances/lighting. So why do we discuss appliances so much?

So say if we fixed homes to use 20% of their energy.

That leads to a reduction of about 56% of our domestic energy requirement.

Domestic energy use is about 28% of total. I think it works out about 16% decrease in energy demand by doing this work. That's 25m tonnes of oil equivalent. I make this 290750TWh .

Now ignore all that because I wasn't looking at electrical space heating, and electrical is what HC is all about.

For that we could save about 1.5m tonners of oil, which I make to be 17.45PWh.

I know HC is supposed to provide 3.2TWe of power but how does this translate to energy - do they run it full pelt all year?

I'm sure I've cocked up somewhere.

Most of the profit of nuclear comes from the last 5% or 10% of reliability. The difference between running at 85% and 95% is what gives the payback, as most of the costs are fixed regardless of the output.

What I'm asking is how does the power rating relate to the energy output?

If it's average 70%, does that mean it's 3.2TWe * 365 * 0.7 = 817TWd of energy (d meaning days, not sure if that is right).

Of course you then have all the grid inefficiencies to consider...

The 2015 DUKES statistics give nuclear capacity factors:
2011 66.4
2012 70.7
2013 73.8
2014 66.6
2015 74.1
and data for quite a few other kinds of power plants, too. Amusingly, coal power plants are at capacity factors closer to 50%.

The exact capacity factors are a bit tricky to calculate because some plants
might only come into operation (or be decommissioned) partway through the year.

I'm puzzled by the suggestion that preponderance of physically rotating generators is the only practical way of synchonising AC phases. Surely it can be done by heavy duty electronics, in this day and age?

Tom - Google synchronous and asynchronous

Without degenerating into electrical engineering 101, anything that has an invertor output (so a PV panel as an example) can only provide an AC output if the complex electronics ( 6 or 12 pulse rectifier or pulse width modulation) ie it is asynchronous - these need a stable AC supply to track and provide a synchronous output in parallel with a synchronous supply

Basically anything big, turning at the right speed and with the correct number of pole pairs in the alternator

Given that the bulk of supply is very big synchronous alternators, and speed is relatively easy to control, when all connected together we have this big, stable AC supply onto which all the asynchronous outputs can lock in and deliver power

As you start to reduce the synchronous component and introduce more asynchronous components you start to get (In Steam Tea's language) the tail wagging the dog

At a grid level, you cannot connect all this asynchronous stuff unless you have a synchronous supply

As an example - lets say we have 10 houses all needing 10kW - currently we feed that from a grid that is principally synchronous

Now we put 5kW PV on the roof of each house - so simple maths tells us that actually we only now need a grid capacity of 50kW and the remainder comes from the PV's

Then Bob the builder arrives with his big yellow cable finding tool - and everything is off supply (as the PV can't track a non supply, isn't configured for island mode and trips out)

Now, we try and close our 50kW supply into the 100kW load - it trips due to overload and the PV again can't be used

So what we have to do is go around and turn off half the houses, reconnect the supply, that then holds, the PV connects and we can then start turning on more houses

Multiply this to a grid level - how do we go around turning people off other than in big groups - and only then when we hope to god it isn't dark and there is no big high pressure system with no wind

It gets more complex with things like overvoltage and the inability of the small scale stuff (even collectively) to clear big faults so you get essentially a "cascade" tripping effect - it's a runaway process and doesn't take long to collapse the whole grid and jolly old blighty is now entirely tripped - back to the initial problem

Does that give you a sense of the problem and why simply wishing for more renewables isn't as simplistic as a lot of people who really should know better would have you believe - you need "how guys" and pretty deep pockets

And government wants cheap and secure - which is most certainly not what I described above if we do end up with the tail wagging the dog

Regards

Barney

Posted By: barneyNow, we try and close our 50kW supply into the 100kW load - it trips due to overload and the PV again can't be used

Try a large council estate (5000 homes) where they all have electric heated water tanks, and they have all done the evening washing up while off, additionally a lot of them would have had fan heaters that will all turn on when the power is restored. Then do it every day for months due to the miners being on strike.

Then you will understand why the people at the time wished to move to gas, or just about anything that the miners could not mess up!

Discussion on Hinkley C now: Radio 4 - The Briefing Room (20:00). Too soon to post a Listen Again link.

Posted By: fostertomIt sounds like mechanical-era technology, when everything was controlled by relays, valves, thermostats, governors - before electronic logic arrived.

Local grids quite often used to be DC. Part of the reason to change to AC was that it makes switching easier and cheaper. It also makes cables smaller as it is simple and relatively cheap to step the voltage down.

By HVDC linking asynchonous grids I meant regions or countries that have different AC grids. For example Great Britain and France have asynchronous grids because they are not in sync. Same with Great Britain and Ireland (the island of). HVDC can be used to export electricity from one to another because it can be converted to AC at each end. It does not even have to be used for distance, there are back-to-back HVDC schemes at borders such as Finland/Russia.

The US NOAA seems a good enough sourece for me, if they say it can be done and done affordably.

Ed

It’s delicate confronting these priests of the golden bull
They preach from the pulpit of the bottom line
Their minds rustle with million dollar bills
You say Silver burns a hole in your pocket
And Gold burns a hole in your soul
Well, uranium burns a hole in forever
It just gets out of control.
– Buffy Sainte-Marie, “The Priests of the Golden Bull”

Protestations? I rely on you Dave

I'm voting on the side of large power electronics being able to substitute for rotating machinery: switched mode devices are quite capable of supplying large amounts of reactive power and exactly simulating a big rotating thing inducing a current. You need a bit of storage (say 30 seconds worth) on the DC side for an inverter to completely replace the stabilising role of an alternator. This can also be done on the demand side (e.g. inverters for battery chargers).

There is plenty of rotating stuff on the demand side. Also much renewables involves big rotating things. And worst case scenario, as djh mentioned, nothing to stop you putting some flywheels in (or just spinning gas turbines in air).

So the grid stability stuff seems a bit overblown to me: this will require some effort, but the intermittency/storage issue is much harder. After all, large countries occasionally run entirely on renewables without all the lights suddenly going out.