How much is 1 W?
How much is 1 W? That was the question of a previous post and simply – how much is 1 W? Can we correlate it somehow to something we know from our daily life?
Some days ago I posted a discussion on energy harvesting and why we do not harvest more. I took the example of lifting up 100 kg and put it one meter up – on a shelf. That would correspond to 1 kJ.
Then we did some obscure calculations and ended up with a number of 1 W that possibly could be harvested while walking and scavenged for your wearable devices.
One Watt – what’s that?
First, let us consider something that is continuously turned on, and that the average power consumption is 1 W. In reality we would have more complex scenarios with sleep-mode and peak activities, etc.
Think of it in terms of voltage and current, P = V * I. If we have a 1-V supply, that corresponds to a 1-A current (!) In the world of integrated circuits this is a comparatively large (huge) number.
Assume you have a 1-Ohm parasitic resistance in one the wires providing the current and you end up in a quite boring functionality.
A fairly standard AA battery with a 1.5-V supply will offer you something like 2.5 Wh (Watt-hours) assuming 1.5 V output. This means that you have to take a good 2.5-hour walk to compete with a battery if your shoes would offer you 1 W while harvesting.
Below we find some examples on 1 W, or at least numbers close by, that might help to illustrate the power level.
The maximum display power on a Samsung Galaxy SIII is around 1 W.
The maximum output power of USB 3.0 is 4.5 W.
Moving a litre of milk from one shelf to another in the fridge, in one second (or a 33cl can of beer from the slab on the floor to the table – in one second).
Bluetooth low energy can be more power hungry than you think, approximate numbers are peaking at 50 mW at operation. In average though, they consume some 5 uW or even less than that in sleep mode. (Never the less: quite a lot of Bluetooth units can be connected to the tip of your toes if you harvest 1 W… )
In southern United States, with a 20-% solar panel efficiency, a 7-by-7-square cm solar panel would produce 1 W for you.
0 dBm is 1 mW, i.e., 30 dBm is 1 W. Which by the way is the average leakage power from a microwave oven.
If you would heat water with 1 W you would have to wait 4.2 seconds until the temperature of 1g of water has increased by one degree.
And please do not forget Regulation 1275/2008 from January 2010 that states that all electric household devices in the European Union must not consume more than 1 W in standby.
Any other way to illustrate 1 W?