hoovering up robot data

I recently replaced the power supplies to my Drobo disk drives. These file servers each have 5 disks and one was starting to struggle after a reboot. Older disks seem to need a bit more oomph to restart.

Just for fun it's got me thinking about all these recent robot TV stories - Humans, Westworld and similar shows. I know, it's fiction, but I'm interested in the power needed for an untethered human-sized robot to operate for 24 hours. That's before it develops the m-m-minor g-g-glitches favoured in most sci-fi and by my Drobo (Data Robotics) disks.

So when sitting idle I consume about 80 watts, increasing to 100-130 watts for very light exercise, about 200 watts when cycling (according to my Garmin Edge 810) and up to about 500 watts for short bursts of time (also Garmin).

Distributing that power through a day I get to a figure of about 2900 watts, or 121 watts per hour. It is higher than Wikipedia says, but when I do a quick cross check of my figures with an average daily calorie intake, it gets to the following:

I've generalised these numbers so that they equate to someone consuming 2,500 Kcal per day. Coca Cola cans say people consume 2,000 Kcalories per day, but I suspect that the 2,500 Kcal is still a reasonable guess.

My numbers are only rough figures and an hour or so of cycling could skew the energy consumption upward. It's still enough for some further fun calculations.

Now assume a battery equivalent to supply the energy - i.e. a robot version of the same form consuming electricity instead of salads, spaghetti and cups of tea.

I use a couple of examples of modern high-tech batteries (from a Dell computer and from an e-bike) to gauge an average of around 130 Watt hours per Kilogram of battery weight. I'll leave clever mini reactors and insanium out of this for the moment.

The battery efficiency equates to a bizarrely heavy 22 Kilos or 50 lbs of battery weight per day to drive a human-sized machine doing human type things if the efficiency was 1:1. I suppose a substitute humanoid could be made of structurally light materials, although the design of a human already optimises much of this. Come to think of it, probably removing the 55% water in a human would be the biggest reduction in weight?

There's still a a big 'but' though. Most machine efficiency is considerably lower than biological efficiency.

As an example, a modern petrol car runs at about 21% efficiency after decades of honing. A 1:5 reduction in efficiency would drastically increase the battery need for a 24 hour human-shaped self-contained machine to 111 Kilos, or 245 lbs. Ironically there would also need to be fans and coolant to dissipate heat created during bursts of activity.

But I suppose we'd remove the water and make other redesigns. That's where non fictional untethered robots would operate very differently, by not needing to move around in the same way as a human.

I begin to understand why robots in Star Wars and other series are often shaped like industrial vacuum cleaners.