Another Smart Meter thread.

If we take last Saturdays figures, wind produced hardly any electricity (according to gridwatch) and when it was dark, solar won't have produced a right lot. I assume people who only buy green electricity sat in the dark.

Now here's a thought. Sat here with my laptop consuming power, is it possible to say meaningfully where the energy is coming from?

Locally there are 3 turbines and a largish solar farm, but I think the nearest big generator is Nuclear. We're all connected to the grid with a multitude of other generators and consumers.

I think of DC power transfer as being like a belt and pulley drive where electrons form the belt, leaving the generator in a stream to the load and back on the other wire. AC the same except the electrons waggle backwards and forwards. The analogy is OK as far as it goes but can't be right! In that model it can't be said electrons travel across a meshed grid from one particular generator to one particular consumer. A better analogy might be energy is poured like water into the top of a pot and tapped, source unknown, by users underneath.

Consumers don't buy from a particular source. Rather there's a financial system allowing consumers to buy energy and suppliers to sell it - but not to individuals. It's a pool. When energy is bought from a Green supplier he puts that value of renewable energy into the into the system, not necessarily at the same time his customers are consuming it.

I suspect my pulley and pool analogies are both more-or-less misleading. Does anyone have a better explanation? How exactly does electricty transfer energy?

Dave

SOD,

I think your water analogy is probably a good simplification of the grid system. Think of it maybe as a water grid on the same connectivity nationally as the electric grid. For your pot and for simplification imagine a reservoir into which all the suppliers pour their contribution to demand and consumers taking what they need from the pipes.

You cannot guarantee that any consumer will necessarily receive the contribution of a particular supplier, that is why the market is set as it is, suppliers get paid for the contribution they make to your pool of energy by the wholesale utility buyer / seller and consumers pay the retail local utility provider for the energy they use who in turn have contracts with the wholesaler for the energy they sell. There are profit margins applied at each transaction.

As alluded by other posts there are times when there simply is not enough “renewable” energy being generated to meet the supply agreements of all those claiming to supply only 100% renewable energy. So the claims being made by these suppliers are simply not true on an instantaneous basis so we can apply a bit of smoke and mirror magic here to keep the lights on that over an average of time suppliers are only selling renewable energy they purchase, the fact they may purchase more renewable energy than they are selling when the wind blows and the sun shines allows the somewhat false claim to be substantiated. The excess is not stored it’s shared by load balancing. That’s my take on it anyway. Certainly where I live right close to a wind farm there is no guarantee that green wigglies from the windmills are going into my lathe 24/7 with no brown ones being excluded!

Paul.

I'm not quite sure what you're asking Dave, but your understanding seems broadly correct to me. Certainly there is no direct path from a generator to a consumer, the electrons get mixed up in the grid. I don't think there is much storage capacity in the UK so the 'pot' in your analogy is fairly small. If I'm right (and I'm happy to be corrected - I'm only just starting on my quest to understand all this) the 'pot' is filled by supply taps fed from various sources - nuclear taps provides a steady stream, wind taps sometimes gush then sometimes drip and dry up, solar taps gush and drip in more predictable ways, and the demand taps at the bottom of the pot open and close in a fairly predictable ways. To balance supply and demand the flow from the Combined Cycle Gas Turbine supply tap is turned up or down as needed. That's my (no doubt over-simplified) understanding anyway.

More generally:

When companies generate carbon-neutral energy (ie everything except that from burning fossil fuels) they also generate Renewable Energy Certificates (RECs) in proportion to the amount of energy generated. These aren't attached to the electrons unfortunately! They are abstract representations of 'value' in the same way as money is an abstraction, and are traded speculatively just as money is.

For the most part, when you buy 'green energy', or indeed 'green' anything you are buying from a company who has bought enough RECs to cover their carbon footprint. The idea behind this system is that if consumers demand more 'green' products, REC prices will rise, so supply will follow and there will be an incentive to invest in renewable energy technologies because the price of the RECs will increase. This is what is called a 'market based solution' to the problems we face. Other solutions are available I expect.

Robin.

Edited By Robin Graham on 03/09/2022 00:40:24

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It’s rather early in the morning for such things, but I think you will find the word Entropy useful:

Statistical Thermodynamics and Shannon’s Theory both use the same underlying concept … neatly encapsulated by this snippet :

The concept of information entropy was introduced by Claude Shannon in his 1948 paper "A Mathematical Theory of Communication",^[2][3] and is also referred to as Shannon entropy. Shannon's theory defines a data communication system composed of three elements: a source of data, a communication channel, and a receiver. The "fundamental problem of communication" – as expressed by Shannon – is for the receiver to be able to identify what data was generated by the source, based on the signal it receives through the channel.^[2][3]

Ref. **LINK**

https://en.wikipedia.org/wiki/Entropy_(information_theory)

MichaelG.

Edited By Michael Gilligan on 03/09/2022 05:54:15

About the only thing that makes most electricity that wasn’t green into ‘green’ is when the distributors pay for the privilege, by buying carbon tokens to make them feel better (actually unlikely) but legally covered.

It's clarification of the 'electrons mixed up in the grid bit'.

In a DC system, does an electron actually travel all the way around the circuit? Wikipedia suggests not: The drift velocity in a 2 mm diameter copper wire in 1 ampere current is approximately 8 cm per hour. AC voltages cause no net movement; the electrons oscillate back and forth in response to the alternating electric field (over a distance of a few micrometers)

Given electrons don't move very far, how do they transfer energy?

Is energy transferred in the same way in both DC and AC systems? (AC has waves, DC doesn't).

And how do they do they transfer energy in a way that allows multiple sources and sinks to be connected to the same media without interference?

I promise to try and understand Entropy as recommended by Michael, but all previous attempts ended badly!

Dave

Think of DC like a VERY large reservoir with water gushing in from a river and trickling out through many streams. A single water molecule could be in the lake for months but the reservoir level remains the same.

Hi Dave. This is inevitably a bit hand-waving, but I hope it will answer some of your questions to some extent.

Let's start with "given electrons don't travel very far...". They don't need to.

DC case: You shove electrons in (slowly) at one end of the wire, they push the electrons which were 'sitting' there along (slowly), they push the next ones along and so one until the electrons at the other end get shoved and can be made to do work. Although the electrons are individually moving slowly, the 'shove effect' moves much faster - at something approaching the speed of light. An electron injected at the generator end may or may not make its way round the circuit back to the generator, but it doesn't need to in order to transfer energy to the 'work'. A physical example of this sort of thing is given by a Newton's cradle - energy is transmitted at the speed of sound from one end of the cradle to the other by a compression wave without the particles in the intermediate balls moving very far from their equilibrium positions at all.

AC case: It's not much different at this level. The electrons are just pushed and pulled in and out of wire at the generator end, and the effect propagates as a wave down the wire to the work end. Because the drift velocity is zero averaged over an AC cycle no electron makes its way around the circuit except by diffusion. The electrons at the other end are forced to jiggle back and forth and can be made to do work.

Does that help? Apologies if I've misunderstood your questions.

I don't know anything about the practicalities of energy distribution so can't comment on that.

This has now strayed a long way from my opening post, but it's all been interesting to me at least. I am now decided firmly against a smart meter and given that it looks like I'm going to be paying about 65p per kWh for electricity after 1st Oct I'll probably switch to a supplier bound by the price cap.

Robin.

Edited By Robin Graham on 03/09/2022 23:18:26

Hi Robin

Switching to another supplier charging the capped rate may prove difficult as it seems that unit costs are not available from energy suppliers at present, or at least I couldn't find any from those supplier sites visited.

Emgee

I actually found a quote from Ecotricity (one of the three exempt from the cap) a couple of days ago, about 65p /KWh for electricity after Oct 1st. But today they won't give a price because of the "fluctuating market". So who knows!

Robin

The devil whispers ‘tick-boxes’ and ‘bandwagon’ in my ear : **LINK**

https://www.ecotricity.co.uk/support/our-energy-tariffs

MichaelG.

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Ref. __ https://politicaldictionary.com/words/bandwagon/

Edited By Michael Gilligan on 04/09/2022 06:39:46

Please excuse the further digression, but I need to share my astonishment :

gov.uk has adopted the Americanism : checkbox

https://design-system.service.gov.uk/components/checkboxes/

**LINK**

MichaelG.

Little by little, the UK & England is being dismantled.

Martin.

I hope everyone is watching Panorama on how we the great British public are getting shafted left right and centre!

Tony

You don't need to bother, all you need is one of these

Please excuse the Add

Good to see that it's not just us Brits that are gullible. £79 for a 10p capacitor in a plastic box? You must be joking.

Peter

Many posts back someone asked about energy grades. The grade of any particular energy source is related to the concept of entropy. To keep things a bit simpler and not get too deeply into thermodynamics, lets just think about heat sources. If we have a source of heat and a cooler place, we can run a heat engine on the difference in temperature. Sadi Carnot tells us that the greater the difference in temperature, the more efficient our heat engine can be. So a big difference in temperature means we have a high grade source of energy, while a small difference in temperature means we have a low grade source of energy.

On the other question of how the energy gets from place to place, well, the important thing is actually the magnetic and electric fields around the wires, not the movement of the electrons. These fields propagate through free space at the speed of light, and along wires at maybe 70% or so of the speed of light, depending on the dielectric around the wires.

John

Michael's link is to a Software Engineering document. In computer speak a checkbox is one of the widgets used to implement WYSIWYG GUI. For example:

• HTML - <input type="checkbox" id="vehicle1" name="vehicle1" value="Bike">
• JAVA - public class JCheckBox extends JToggleButton implements Accessible
• Qt - QCheckBox(const QString &text, QWidget *parent = nullptr)
• etc

The industry standardised on checkbox rather than tick-box because widgets were conceived in the USA. I don't think it's cultural imperialism because other widget names like slider, button, dropdown, textbox and label don't seem to be designed to crush the British! Rather the opposite - almost all the world's computer languages are based on English.

Dave

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That someone was me [on another thread], John
Thanks for your elucidation

As you will see from page-1 of this thread … I did manage to convince myself that Iunderstood the concept and commented accordingly.

[quote]

NDIY … you may be interested to know that [after your previous insult] I did look-up the meaning of ‘grade’ in this context; and was disappointed to find that it means very little.

I was expecting to see some sort of scale [c.f. Centigrade], but it turns out to be binary

… Fuels are either ‘Low Grade’ or ‘High Grade’

< sigh >

MichaelG.

[/quote]

Thanks again, John