macd
Active member
My point was, why the 'hour'. It's either 1kw or it isn't.
Generator -v- solar panels
- Thread starter Slow_boat
- Start date
My point was, why the 'hour'. It's either 1kw or it isn't.
rustybarge
Active member
Hi mac,
Electricity is measured by flow, just like a waterhose. 1kw means that 1000 watts flows for 1 hour. Speed of flow is volts, volume of flow is kw, and kw/hr is time measurement.
Electricity is measured by flow, just like a waterhose. 1kw means that 1000 watts flows for 1 hour. Speed of flow is volts, volume of flow is kw, and kw/hr is time measurement.
sailinglegend420
Member
The ones I've seen only deliver 10 amps!
macd
Active member
No, that'd be a kW/hour (or 3.6 megajoules, if you prefer).
Of course that wouldn't allow for the hefty voltage drop to the Moon
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gavin_lacey
New member
I manage with 200w of panels plus a rutland 213 wind genny. 480ah of house batteries to bridge the gaps. It has been said many times but it is far more cost effective to reduce consumption than to buy and run generation.
A really well insulated fridge and LED lighting (Those from Sea Rolf are excellent) mean that consumtion is covered by the wind and solar.
The only time that I would have a problem would be sailing for many days continuously with nav equipment and nav lights, I have not yet done this since when the wind dies I start the engine. If going trans atlantic then a towed generator would be my choice regulated by the same regulator as the rutland.
A really well insulated fridge and LED lighting (Those from Sea Rolf are excellent) mean that consumtion is covered by the wind and solar.
The only time that I would have a problem would be sailing for many days continuously with nav equipment and nav lights, I have not yet done this since when the wind dies I start the engine. If going trans atlantic then a towed generator would be my choice regulated by the same regulator as the rutland.
rustybarge
Active member
Hi mac,
those mega joules, are they diamonds or diamanté ? Moonlight will power your solar cells at nightime, no- probs.
Me, I failed physics, that's why I put a question mark after the answer.
A fuel cell generates electricity, it does not store it.....so I was correct when I said it produced 1kw/hr.
Whereas batteries store power, a fixed amount ie 1kw or 100 amps etc.
those mega joules, are they diamonds or diamanté ? Moonlight will power your solar cells at nightime, no- probs.
Me, I failed physics, that's why I put a question mark after the answer.
A fuel cell generates electricity, it does not store it.....so I was correct when I said it produced 1kw/hr.
Whereas batteries store power, a fixed amount ie 1kw or 100 amps etc.
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Chalker
Member
If a generator puts out 1kW for 1 hour that is 1kWh.
If you run the same generator for 2 hours, that is 2 kWh.
Obviously it has not changed the the power output of the generator (kW), only the total energy produced (kWh).
So a generator or a fuel cell will have a power output in kW not kWh
1kw at 12v is 1000/12 = 83.33 Amps, not 100
(These days I never can remember which units are capitals and which are lower case!)
If you run the same generator for 2 hours, that is 2 kWh.
Obviously it has not changed the the power output of the generator (kW), only the total energy produced (kWh).
So a generator or a fuel cell will have a power output in kW not kWh
1kw at 12v is 1000/12 = 83.33 Amps, not 100
(These days I never can remember which units are capitals and which are lower case!)
rustybarge
Active member
Hi chalker,
If you run a 1kw genie for 2hrs it will still only produce 1kw/hr, not 2kw/hr.
So all generators are rated in the work they can do in one hour. A fuel cell is a genie.
I allowed for losses in the inverter and cable losses by dividing by 10 not 12.
If you run a 1kw genie for 2hrs it will still only produce 1kw/hr, not 2kw/hr.
So all generators are rated in the work they can do in one hour. A fuel cell is a genie.
I allowed for losses in the inverter and cable losses by dividing by 10 not 12.
Chris_Robb
Well-known member
well -not quite, sorry about the a level.
Batteries store - so are referred to as amp/hours. ie they can give out 110 amps for 1 hour (110amp/h)
Generators are referred to by output (at this instant) so measured in KiloWatts and not generally KW/h
rustybarge
Active member
Hi chris,
Ok I agree bhp is a measurement of power at that instant, but all generators have a continuous power output rating.....ie. kw/hr.
I hp (.7 kw) approx) means one horse can plough x amount of a field in one hour, so all work output has an element of time to define it.
So power output is like speed. Ie: 100 miles in one hour, or Mph.
Ok I agree bhp is a measurement of power at that instant, but all generators have a continuous power output rating.....ie. kw/hr.
I hp (.7 kw) approx) means one horse can plough x amount of a field in one hour, so all work output has an element of time to define it.
So power output is like speed. Ie: 100 miles in one hour, or Mph.
Chris_Robb
Well-known member
Paguro 6500
6.5 kVA / 6 kW
101-0302
Clipped from a web site.
KW/h is primarily a measure of stored electricity.
BHP
Brake horsepower (bhp) is the measure of an engine's horsepower before the loss in power caused by the gearbox, alternator, differential, water pump, and other auxiliary components such as power steering pump, muffled exhaust system, etc. Brake refers to a device which was used to load an engine and hold it at a desired RPM. During testing, the output torque and rotational speed were measured to determine the brake horsepower. Horsepower was originally measured and calculated by use of the "indicator" (a James Watt invention of the late 18th century), and later by means of a De Prony brake connected to the engine's output shaft. More recently, an engine dynamometer is used instead of a De Prony brake. Although the output delivered to the driving wheels is less than that obtainable at the engine's crankshaft, a chassis dynamometer gives an indication of an engine's 'real world' horsepower after losses in the drive train and gearbox. This gives a reasonably accurate indication of how a wheeled vehicle engine will perform once on the road.
rustybarge
Active member
Thanks.
Your electricity is measured by your meter in Kw/hr..........is that stored electricity?
Power 'output' is a measure of work, just like speed is a measure of distance travelled.
Maybe this is why I failed physics !!!
Your electricity is measured by your meter in Kw/hr..........is that stored electricity?
Power 'output' is a measure of work, just like speed is a measure of distance travelled.
Maybe this is why I failed physics !!!
Chris_Robb
Well-known member
rustybarge
Active member
So it's a case of the blind leading the blind...........oh heck!
Chris_Robb
Well-known member
Should have gone to specksavers
macd
Active member
Maybe it is.
Rusty, when in a hole, stop digging.
An electrical device is rated in kW, not kW/hr. If it's 1kW and on for an hour, that's 1 kW/hr, but so what? kW is already a measure of work over time (one watt is the rate at which work is done when an object's velocity is held constant at one meter per second against constant opposing force of one newton). To add a second time constant, your 'hr', to that is absurd.
A battery, as has been mentioned, doesn't have the luxury of time: it's capacity is finite (although somewhat variable depending on load): so the Amp-hr in its description is more or less an absolute. Your 1kW heater, on the other hand, can keep going for a year, munching leccy at 1kW the whole time.
Bhp, as you write, is also a measure of work over time, which is precisely how it was originally defined. In imperial units it's derived from bhp = torque x rpm/5252. The 'm' in rpm is obviously minutes....i.e. time. Thus bhp can also be expressed in kW, and often is.
What will you come up with next, the bhp/hr?
Chalker
Member
Thanks Mac
The output of a generator is measured in kiloWatts (kW) or VA which is similar(but can be different for AC). Not kilowatts per hour kW/h or kiloWatthours kWh. The generator has a voltage x current rating = Watts that has no time component.
Batteries capacity is normally rated in Ah. A 100Ah battery can give 100 amps for 1 hour or 20 amps for 5 hours etc. (Yes I know that at higher currents you will actually get fewer Ah but lets not add to the complication!)
If you have a 12 volt 100Ah battery then you could also describe the same battery as storing 12 volts x 100Amps = 1200 Watt hours = 1.2kWh (Watts = Volts x Amps).
If this battery has a load that takes 20 amps you are producing 12x20=240 Watts.
If you do this for 1 hour you have used 240 Watt hours (Wh) = 0.24kWh.
If you only take the 20A for 1/2 hour you are still producing 240 Watts but have only used 120 Wh = 0.12 kWh.
kWh is kW x hours, I don't think kiloWatts per hour (kW/h) has any real meaning.
Rusty, I half agree with you.
A 1kw generator produces 1kWh in 1 hour or 2kWh in 2 hours.
The output of a generator is measured in kiloWatts (kW) or VA which is similar(but can be different for AC). Not kilowatts per hour kW/h or kiloWatthours kWh. The generator has a voltage x current rating = Watts that has no time component.
Batteries capacity is normally rated in Ah. A 100Ah battery can give 100 amps for 1 hour or 20 amps for 5 hours etc. (Yes I know that at higher currents you will actually get fewer Ah but lets not add to the complication!)
If you have a 12 volt 100Ah battery then you could also describe the same battery as storing 12 volts x 100Amps = 1200 Watt hours = 1.2kWh (Watts = Volts x Amps).
If this battery has a load that takes 20 amps you are producing 12x20=240 Watts.
If you do this for 1 hour you have used 240 Watt hours (Wh) = 0.24kWh.
If you only take the 20A for 1/2 hour you are still producing 240 Watts but have only used 120 Wh = 0.12 kWh.
kWh is kW x hours, I don't think kiloWatts per hour (kW/h) has any real meaning.
Rusty, I half agree with you.
A 1kw generator produces 1kWh in 1 hour or 2kWh in 2 hours.
rustybarge
Active member
Hmmmm, well now let's see.
All those caluations look good, but remember we are talking output, yes output.
Eg. A 1kw Honda petrol genny has a continuous output rating, which means it can run a daylong at spec. Load.
It also has a max. Rating which usually states something like : not more than 2kw for more than 10 mins period.
So genny's are rated output/hr, ..........that's kw/hr....or work they can achieve in 1 hour.
You are watering your lawn with a garden hose. It's a 20 gallon hose.....what?
Eg water flows at 20gal/hr.
That's a great looking horse(1hp) ...it can plough 1acre in a day=1hp/day.
Power output from that fuel cell was 1kw/hr...continuous rating...=work/time
L
Phew.......hanging on by my finger tips !
All those caluations look good, but remember we are talking output, yes output.
Eg. A 1kw Honda petrol genny has a continuous output rating, which means it can run a daylong at spec. Load.
It also has a max. Rating which usually states something like : not more than 2kw for more than 10 mins period.
So genny's are rated output/hr, ..........that's kw/hr....or work they can achieve in 1 hour.
You are watering your lawn with a garden hose. It's a 20 gallon hose.....what?
Eg water flows at 20gal/hr.
That's a great looking horse(1hp) ...it can plough 1acre in a day=1hp/day.
Power output from that fuel cell was 1kw/hr...continuous rating...=work/time
L
Phew.......hanging on by my finger tips !
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Chris_Robb
Well-known member
Chalker
Member
Rusty, let's see if we can change your view of watts, watt hours and watts per hour. I think that you just have an incorrect picture in your mind.
Water flows through a pipe at 10 gallons per hour into a big bucket, in an hour you have 10 gallons.
Gallons per hour (g/h) is the rate of flow, gallons are the amount that has flowed.
Amps and Watts are the same type of unit as gallons per hour, a rate of flow. The difference between them is that Watts includes the voltage.
So Watt hours are the same type of unit as gallons, rate of flow x time.
Are you clear that Wh (Watt hours) are Watts x hours and w/h are Watts divided by hours?
W/h (or kW/h) are equivalent to gallons per hour divided by hours. .????
So 10 gallons per hour per hour might give 10 / 2 = 5. But 5 what?
Water flows through a pipe at 10 gallons per hour into a big bucket, in an hour you have 10 gallons.
Gallons per hour (g/h) is the rate of flow, gallons are the amount that has flowed.
Amps and Watts are the same type of unit as gallons per hour, a rate of flow. The difference between them is that Watts includes the voltage.
So Watt hours are the same type of unit as gallons, rate of flow x time.
Are you clear that Wh (Watt hours) are Watts x hours and w/h are Watts divided by hours?
W/h (or kW/h) are equivalent to gallons per hour divided by hours. .????
So 10 gallons per hour per hour might give 10 / 2 = 5. But 5 what?