Poll

Do you keep records of your solar production

No I dont have solar
20 (57.1%)
No I don't care
3 (8.6%)
I look at the GTI LCD occasionally
4 (11.4%)
I look at the GTI display often
3 (8.6%)
I look at the GTI display even after dark
3 (8.6%)
I have solar, no GTI and I keep records (like Mike)
2 (5.7%)

Total Members Voted: 35

Author Topic: UK solar doldrums  (Read 6765 times)

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Offline ahbushnell

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Re: UK solar doldrums
« Reply #50 on: January 13, 2018, 08:38:44 am »
any measurement of W or A is an assumption over time and can be only taken as an equivalent or verified after 1 hour if it is to be Ah or Wh, we could equally use minutes or seconds but for general transmission, storage and generation we use the hour as the unit of time
I think the word equivalent is important and it need not be verified, for example if 300W is measured for 30 minutes it is correct to quantify it as 600Wh because that is the equivalent hourly energy production. I have some Kwh displays that update every minute (for example how much energy have I consumed today), its just a ratiometric progression.

BTW I see we have added miles into the mix now :)

300 watts for 30 minutes is 300 watt* .5 hours =150 watt-hr.

 

Offline Simon

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Re: UK solar doldrums
« Reply #51 on: January 13, 2018, 08:39:58 am »
both speed and watts are time related, you have to set a standard unit. 1W = 1J/s but we never intend a watt as the energy (Joules) used in a second but in one hour and probably hence the more accurate but not always used Wh, we would equally say 3600 J/h
« Last Edit: January 13, 2018, 08:48:18 am by Simon »
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Offline GeorgeOfTheJungle

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Re: UK solar doldrums
« Reply #52 on: January 13, 2018, 08:48:37 am »
both speed and watts are time related, you have to set a standard unit. 1W = 1J/s but we never inten a watt as the energy (Joules) used in a second but in one hour and probably hence the more accurate but not always used Wh, we would equally say 3600 J/h

Because Wh is not the same as W/h, 1Wh is not 3600 J/h, it is 3600 J, or, if you prefer, 1Wh = 1W * 1h = 1J/s * 3600s = 3600J.

But you're trolling me, no?
« Last Edit: January 13, 2018, 08:54:10 am by GeorgeOfTheJungle »
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Offline Simon

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Re: UK solar doldrums
« Reply #53 on: January 13, 2018, 08:56:03 am »
both speed and watts are time related, you have to set a standard unit. 1W = 1J/s but we never inten a watt as the energy (Joules) used in a second but in one hour and probably hence the more accurate but not always used Wh, we would equally say 3600 J/h

Because Wh is not the same as W/h, 1Wh is not 3600 J/h, it is 3600 J, or, if you prefer, 1Wh = 1W * 1h = 1J/s * 3600s = 3600J.

But you're trolling me, right?

Erm why would I be trollin you?

1W = 1J/s, there are 3600s in 1h, so if you are using 1W for 1h you need to use 3600W as in 3600 J/s, but we usually refer to watts as over an hour period so what might technically be referred to as 1W is actually 1Wh

if 1W = 1J/s then 1Wh = 3600W = 3600 J/s.

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Offline Simon

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Re: UK solar doldrums
« Reply #54 on: January 13, 2018, 08:57:28 am »
what is the difference between Wh and W/h then ?
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Offline coppice

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Re: UK solar doldrums
« Reply #55 on: January 13, 2018, 09:41:47 am »
what is the difference between Wh and W/h then ?
Wh is a measure of energy - i.e. the first integral of power over time.
W/h is a rate of change of power - i.e. the first differential of power with respect to time. E.g. if a load is increasing by 10W every hour it would be increasing at a rate of 10W/h.
 

Offline Simon

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Re: UK solar doldrums
« Reply #56 on: January 13, 2018, 09:49:14 am »
but I was previously corrected and told that 1W = 1J/s which is intended as joules per second not changing by a rate of 1J every second.
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Offline coppice

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Re: UK solar doldrums
« Reply #57 on: January 13, 2018, 09:55:13 am »
but I was previously corrected and told that 1W = 1J/s which is intended as joules per second not changing by a rate of 1J every second.
A steady sustained load power of 1W means the consumed energy is increasing by 1 Joule every second
Conversely a steady sustained generated power of 1W means the produced energy is increasing by 1 Joule every second
 

Offline Simon

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Re: UK solar doldrums
« Reply #58 on: January 13, 2018, 09:58:26 am »
but no one has talked about changing power levels simply constant power use to use x amount per second is usually referred to as W/s same as m/s is speed not changing speed.
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Offline coppice

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Re: UK solar doldrums
« Reply #59 on: January 13, 2018, 10:04:38 am »
but no one has talked about changing power levels simply constant power use to use x amount per second is usually referred to as W/s same as m/s is speed not changing speed.
m/s is a rate of change of position = distance/time = speed.
W/s is a rate of change of power.

You were the one to introduce rates of change of power, by using the wrong units.
 

Offline tggzzz

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Re: UK solar doldrums
« Reply #60 on: January 13, 2018, 10:12:05 am »
There are lies, damned lies, statistics - and ADC/DAC specs.
Gliding aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline tggzzz

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Re: UK solar doldrums
« Reply #61 on: January 13, 2018, 10:31:10 am »
both speed and watts are time related, you have to set a standard unit. 1W = 1J/s but we never intend a watt as the energy (Joules) used in a second but in one hour and probably hence the more accurate but not always used Wh, we would equally say 3600 J/h

Why are you concentrating on "standard" time units? Power is not the energy transferred in unit time; power is the rate of transfer of energy.

Consider that if you have a resistor that is perfectly thermally insulated, then any of the following will increase its temperature by the same amount:
  • 1W for 1ms
  • 0.25W for 4ms
  • 1mW for 1s
  • 1MW for 1ns
  • 1/pi mW for 1 nanocentury (OK, only a reasonable approximation!)
In all cases the same energy is dumped into the resistor.
There are lies, damned lies, statistics - and ADC/DAC specs.
Gliding aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline lewis

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Re: UK solar doldrums
« Reply #62 on: January 13, 2018, 10:52:13 am »
1W = 1J/s, there are 3600s in 1h, so if you are using 1W for 1h you need to use 3600W as in 3600 J/s,

NO! One watt is one watt whether you're using it for an hour or a century. Power is not a time-dependent quantity.

One watt for one hour (1Wh) is 3600 joules. Not 3600 J/s.

but we usually refer to watts as over an hour period so what might technically be referred to as 1W is actually 1Wh

if 1W = 1J/s then 1Wh = 3600W = 3600 J/s.

NO NO NO! We do NOT refer to watts as over an hour period. A 60W lightbulb uses 60 watts even if I switch it on for half a second.

1W is NOT 1Wh. They are completely different units. Watt = power. Wh = energy.

1Wh does NOT equal 3600W. 1Wh = 3600J.

I will not be pushed, filed, stamped, indexed, briefed, debriefed or numbered.
 

Offline ahbushnell

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Re: UK solar doldrums
« Reply #63 on: January 13, 2018, 01:31:54 pm »
1W = 1J/s, there are 3600s in 1h, so if you are using 1W for 1h you need to use 3600W as in 3600 J/s,

NO! One watt is one watt whether you're using it for an hour or a century. Power is not a time-dependent quantity.

One watt for one hour (1Wh) is 3600 joules. Not 3600 J/s.

but we usually refer to watts as over an hour period so what might technically be referred to as 1W is actually 1Wh

if 1W = 1J/s then 1Wh = 3600W = 3600 J/s.

NO NO NO! We do NOT refer to watts as over an hour period. A 60W lightbulb uses 60 watts even if I switch it on for half a second.

1W is NOT 1Wh. They are completely different units. Watt = power. Wh = energy.

1Wh does NOT equal 3600W. 1Wh = 3600J.
I suggest looking at a Physics book.

 

Offline Simon

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Re: UK solar doldrums
« Reply #64 on: January 13, 2018, 08:06:51 pm »
1W = 1J/s, there are 3600s in 1h, so if you are using 1W for 1h you need to use 3600W as in 3600 J/s,

NO! One watt is one watt whether you're using it for an hour or a century. Power is not a time-dependent quantity.

One watt for one hour (1Wh) is 3600 joules. Not 3600 J/s.

but we usually refer to watts as over an hour period so what might technically be referred to as 1W is actually 1Wh

if 1W = 1J/s then 1Wh = 3600W = 3600 J/s.

NO NO NO! We do NOT refer to watts as over an hour period. A 60W lightbulb uses 60 watts even if I switch it on for half a second.

1W is NOT 1Wh. They are completely different units. Watt = power. Wh = energy.

1Wh does NOT equal 3600W. 1Wh = 3600J.



Yes I know that 1Wh is not 3600W I was just trying to emphasis the confusion that can arise. but if 1W = 1J used in one second then the definition of a watt is tied to seconds. So yes 1Wh is 3600 joules because to use 1W for one hour you are burning 1J every second and there are 3600 seconds in one hour so you need a joule for each of them to sustain 1W for 1h and as we measure everything in hours you get 1Wh. If you were to say that this thing uses 1W anyone would assume you are saying it is a 1Wh device and yes in an instant, or second it will have 1W going into it.

We would do just as well to rate storage systems in joules and state how many joules can be put out in a second, minute or hour. If in seconds then it ties directly with the definition of a W so you just say I am using xW as 1 second is small enough to consider instantaneous but as we meter everything in hours we end up saying Wh
« Last Edit: January 13, 2018, 08:42:53 pm by Simon »
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Offline donotdespisethesnake

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Re: UK solar doldrums
« Reply #65 on: January 13, 2018, 11:29:01 pm »
Good grief, I thought this was supposed to be a technical forum  :palm:

Next time I get pulled over, I will claim to be driving at "22 meters"  :-DD
Bob
 
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Offline tggzzz

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Re: UK solar doldrums
« Reply #66 on: January 14, 2018, 12:52:23 am »
Good grief, I thought this was supposed to be a technical forum  :palm:

Next time I get pulled over, I will claim to be driving at "22 meters"  :-DD

Alternatively, when somebody asks "how far away is London", you could answer 66mph.
There are lies, damned lies, statistics - and ADC/DAC specs.
Gliding aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline tggzzz

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Re: UK solar doldrums
« Reply #67 on: January 14, 2018, 12:57:02 am »
... but if 1W = 1J used in one second then the definition of a watt is tied to seconds. ...

Let's consider a different phenomenon - heartbeats.

What is your heart rate, expressed in beats per minute, bpm? You can add any caveats you feel helpful or appropriate; the answer cannot be exact.

I'll give you my answer later, but I'm curious about your answer or answers.
There are lies, damned lies, statistics - and ADC/DAC specs.
Gliding aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline lewis

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Re: UK solar doldrums
« Reply #68 on: January 14, 2018, 03:23:08 am »
I suggest looking at a Physics book.

Not sure what you mean, did I get something wrong?
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Offline ahbushnell

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Re: UK solar doldrums
« Reply #69 on: January 14, 2018, 03:38:39 am »
I suggest looking at a Physics book.

Not sure what you mean, did I get something wrong?
Yes
 

Offline lewis

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Re: UK solar doldrums
« Reply #70 on: January 14, 2018, 03:45:53 am »
I will not be pushed, filed, stamped, indexed, briefed, debriefed or numbered.
 

Offline ahbushnell

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Re: UK solar doldrums
« Reply #71 on: January 14, 2018, 03:46:22 am »
 

Offline lewis

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Re: UK solar doldrums
« Reply #72 on: January 14, 2018, 03:49:26 am »
Look at what I wrote above.

Perhaps you can help me out a bit more than that! Which part of my post was wrong?

I suggest reading it again.
« Last Edit: January 14, 2018, 04:38:25 am by lewis »
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Offline lewis

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Re: UK solar doldrums
« Reply #73 on: January 14, 2018, 04:03:51 am »
Yes I know that 1Wh is not 3600W I was just trying to emphasis the confusion that can arise.

You said:

Quote
if 1W = 1J/s then 1Wh = 3600W = 3600 J/s.
I think you're confusing yourself!


If you were to say that this thing uses 1W anyone would assume you are saying it is a 1Wh device...
No. A 1W thing is not a 1Wh device:

A 1W thing, if left on for 1 minute, uses 0.0167Wh of energy
A 1W thing, if left on for 30 minutes, uses 0.5Wh of energy
A 1W thing, if left on for 1 hour, uses 1Wh of energy
A 1W thing, if left on for 10 hours, uses 10Wh of energy
A 1W thing, if left on for 1 year, uses 8760Wh of energy


...and yes in an instant, or second it will have 1W going into it.

A 1W load has 1W going into it for 1 second
A 1W load also has 1W going into it for 1/2 second
A 1W load also has 1W going into it for 1 nanosecond
A 1W load still has 1W going into it even for 1 picosecond
A 1W load also has 1W going into it for 1000 years

The power (watts) of a constant load does not change depending on time.
The energy (joules or watt-hours) DOES change depending on time.
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Offline coppice

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Re: UK solar doldrums
« Reply #74 on: January 14, 2018, 04:26:09 am »
if 1W = 1J/s then 1Wh = 3600W = 3600 J/s.
One of the very first things they would have taught you in high school science is that units must match across an equals sign, so what you wrote there is bogus. 1Wh = 3600W is the most blatant garbage any 11 year old with an IQ around average should know is wrong, even if they struggle to figure out what is right.

Try something that keeps the units in good shape, like:

1Wh = 3600Ws = 3600J
 


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