11 ms·

> Although that sounds like a very light load, if you run it for 24 hours, it's equivalent to using 84 Watts continuously for one hour. Its called 84 watt-hour

> Although that sounds like a very light load, if you run it for 24 hours, it's equivalent to using 84 Watts continuously for one hour. Its called 84 watt-hours and this is energy consumed in 24 hrs. 3.5 watts is energy consumption rate and is called as power(joules/sec). 84 Wh is not actually lot. I made a calculator for raspberry pi energy consumption https://tinyurl.com/nwu6sn4s https://tinyurl.com/nwu6sn4s

walrus01 3y ago
For a comparison, 50W doesn't seem like much, right? Maybe if you're older you had 50W incandescent light bulbs in your house. Normal thing. Let's say a WISP wanted to run a very basic off grid relay site with some radios that are 8-12W DC load each and a router that's 15W. Total around 50W 24x7x365. ((50 x 24 x 31)) / 1000 That's 37.2 kWh per month. You need a surprisingly large amount of solar panels to generate a reliable 45-50 kwH per month to refill a battery bank every day when the sun comes up, in November, December, January, February at latitude 45N or above. Like, really, a lot more than you might think. Four or more 370W 72-cell.
- jakewins 3y ago
  PVwatts says a 4-module array of 370w panels, including AC losses, will produce about 100kWh in January at 45N FWIW
  - walrus01 3y ago
    That's assuming perfect sun exposure on a roof or ground moving with no shadowing at any time of the day and at the optimal tilt. Pvwatts says that usable energy from a 1480W system at 43.6N in Boise ID might be more like 77kWh a month in December, the shortest sunlight month of the year. An off grid system generally needs to be calculated to survive December. January will be a few percent better as days start getting longer. Realistically, to get through entire week long periods of snow and overcast, if I had a load that was 50kWh a month I would want a 75-80kWh a month predicted PV production system to make it worry free in December.
- sgt 3y ago
  Going against the trend here but I still use incandescent bulbs in key places like my desk and so on. I find LED to give a terrible light (not the whole spectrum), but they are getting harder and harder to find.
  - bityard 3y ago
    Incandescent bulbs are not full spectrum, though. They are on the warm end of the color temperature scale, much more "orange" than mid-day sunlight. The good news is that you can get LED bulbs in any color temperature you like. My house is full of "warm white" LED bulbs and I could not tell any difference in brightness or color when I swapped them in for incandescent many years ago.
    - madaxe_again 3y ago
      The difference is colour rendering and the nature of the spectrum. An incandescent bulb is, by definition, emitting black body radiation - it’s a nice curve encompassing a good chunk of the spectrum, but as you say biased towards the red end. LEDs tend to emit discrete quantised frequencies of light, as a result both of the dopants in the LEDs and the phosphors used on bulbs. They have got better, due to better phosphors, but they still don’t render colour as well as incandescent bulbs. That said, I’m all LED here as I cannot afford within our energy budget to burn a kilowatt or more on lighting.
    - ilyt 3y ago
      They are continuous black body spectrum which we got used to
  - goodpoint 3y ago
    > LED to give a terrible light Let's stop spreading this myth. Cheap LED lights can have terrible spectrum. Good LED lights have a better spectrum than incandescent.
    - sgt 3y ago
      I should have phrased it differently. See madaxe's comment: > The difference is colour rendering and the nature of the spectrum. If you compare it with your own eyes, you should definitely be able to see it.
vegardx 3y ago
But 84Wh is still enough energy to drive a modern battery-electric vehicle around 500 meters. Kind of puts things into perspective. I find these numbers really fascinating because it shows how efficient battery-electric vehicles are, especially when you think about things like incandescent bulbs, which easily will run at 50W just to light up a small room. Don't get me started on cars that display usage in kWh/h per 100km. Yes, you read that right.
- pyrale 3y ago
  Conversely, it shows how sparse kinetic energy is, and that's a good explanation to tell people that would see storage issues solved by damming every stream.
- bartislartfast 3y ago
  > Don't get me started on cars that display usage in kWh/h per 100km. Yes, you read that right. ICEs use litres per 100km which I think is where this comes from. And I hate it. miles-per-gallon is much easier to understand I think. I wish we could have split the difference in the EU and just had km-per-litre. I'd rather know how far a tank will get me than how much fuel I'll use to travel exactly 100km
  - Cyykratahk 3y ago
    The biggest problem with MPG is its inverse nature makes it a bad unit to use to compare cars. A 20 MPG car is not twice as efficient as a 10 MPG car. http://www.mpgillusion.com/p/what-is-mpg-illusion.html http://www.mpgillusion.com/p/what-is-mpg-illusion.html L/100km has the length and volume units reversed, which allows comparisons.
    - deleted 3y ago
      [deleted]
    - deleted 3y ago
      [deleted]
    - Goz3rr 3y ago
somishere 3y ago
Agree it doesn't feel like a lot. We run our house, including a decent sized pool pump, off solar for most of the day. A Pi seems like very small fry in the scheme of things. Getting something like this up and running in a few short hours of Dutch summer sun just shows that everyone should be trying it (that includes me).

walrus01 3y ago

For a comparison, 50W doesn't seem like much, right? Maybe if you're older you had 50W incandescent light bulbs in your house. Normal thing. Let's say a WISP wanted to run a very basic off grid relay site with some radios that are 8-12W DC load each and a router that's 15W. Total around 50W 24x7x365. ((50 x 24 x 31)) / 1000 That's 37.2 kWh per month. You need a surprisingly large amount of solar panels to generate a reliable 45-50 kwH per month to refill a battery bank every day when the sun comes up, in November, December, January, February at latitude 45N or above. Like, really, a lot more than you might think. Four or more 370W 72-cell.

jakewins 3y ago
PVwatts says a 4-module array of 370w panels, including AC losses, will produce about 100kWh in January at 45N FWIW
- walrus01 3y ago
  That's assuming perfect sun exposure on a roof or ground moving with no shadowing at any time of the day and at the optimal tilt. Pvwatts says that usable energy from a 1480W system at 43.6N in Boise ID might be more like 77kWh a month in December, the shortest sunlight month of the year. An off grid system generally needs to be calculated to survive December. January will be a few percent better as days start getting longer. Realistically, to get through entire week long periods of snow and overcast, if I had a load that was 50kWh a month I would want a 75-80kWh a month predicted PV production system to make it worry free in December.
sgt 3y ago
Going against the trend here but I still use incandescent bulbs in key places like my desk and so on. I find LED to give a terrible light (not the whole spectrum), but they are getting harder and harder to find.
- bityard 3y ago
  Incandescent bulbs are not full spectrum, though. They are on the warm end of the color temperature scale, much more "orange" than mid-day sunlight. The good news is that you can get LED bulbs in any color temperature you like. My house is full of "warm white" LED bulbs and I could not tell any difference in brightness or color when I swapped them in for incandescent many years ago.
  - madaxe_again 3y ago
    The difference is colour rendering and the nature of the spectrum. An incandescent bulb is, by definition, emitting black body radiation - it’s a nice curve encompassing a good chunk of the spectrum, but as you say biased towards the red end. LEDs tend to emit discrete quantised frequencies of light, as a result both of the dopants in the LEDs and the phosphors used on bulbs. They have got better, due to better phosphors, but they still don’t render colour as well as incandescent bulbs. That said, I’m all LED here as I cannot afford within our energy budget to burn a kilowatt or more on lighting.
  - ilyt 3y ago
    They are continuous black body spectrum which we got used to
- goodpoint 3y ago
  > LED to give a terrible light Let's stop spreading this myth. Cheap LED lights can have terrible spectrum. Good LED lights have a better spectrum than incandescent.
  - sgt 3y ago
    I should have phrased it differently. See madaxe's comment: > The difference is colour rendering and the nature of the spectrum. If you compare it with your own eyes, you should definitely be able to see it.

vegardx 3y ago

But 84Wh is still enough energy to drive a modern battery-electric vehicle around 500 meters. Kind of puts things into perspective. I find these numbers really fascinating because it shows how efficient battery-electric vehicles are, especially when you think about things like incandescent bulbs, which easily will run at 50W just to light up a small room. Don't get me started on cars that display usage in kWh/h per 100km. Yes, you read that right.

pyrale 3y ago
Conversely, it shows how sparse kinetic energy is, and that's a good explanation to tell people that would see storage issues solved by damming every stream.
bartislartfast 3y ago
> Don't get me started on cars that display usage in kWh/h per 100km. Yes, you read that right. ICEs use litres per 100km which I think is where this comes from. And I hate it. miles-per-gallon is much easier to understand I think. I wish we could have split the difference in the EU and just had km-per-litre. I'd rather know how far a tank will get me than how much fuel I'll use to travel exactly 100km
- Cyykratahk 3y ago
  The biggest problem with MPG is its inverse nature makes it a bad unit to use to compare cars. A 20 MPG car is not twice as efficient as a 10 MPG car. http://www.mpgillusion.com/p/what-is-mpg-illusion.html http://www.mpgillusion.com/p/what-is-mpg-illusion.html L/100km has the length and volume units reversed, which allows comparisons.
  - deleted 3y ago
    [deleted]
  - deleted 3y ago
    [deleted]
  - Goz3rr 3y ago

somishere 3y ago

Agree it doesn't feel like a lot. We run our house, including a decent sized pool pump, off solar for most of the day. A Pi seems like very small fry in the scheme of things. Getting something like this up and running in a few short hours of Dutch summer sun just shows that everyone should be trying it (that includes me).