Keystrokes to power smartphones? It's just a waste of energy

Avoiding wasted energy is a big part of the green credo, and at first sight collecting excess power seems a good idea. But in reality good design always trumps those kinds of scheme.

Ideas such as using keystrokes and screen swipes to power laptops, phones and tablets is pointless. There is no free lunch. Photo: Shutterstock

Written in Montreux, Switzerland, and despatched to TechRepublic at 2Mbps over an open wi-fi hub..

Over the past 18 months a number of articles and scientific papers have hit my screen describing various energy-harvesting schemes. Bluntly, these have spanned the vaguely feasible to the purely nonsensical.

At the unlikely end of the spectrum is the idea of using keystrokes, button presses and screen swipes to power mobile phones, tablets and laptops. Equally problematic schemes include collecting energy from cycling and rowing machines at health clubs and gyms.

Even at the apparently obvious end of these endeavours, which involve collecting energy from vehicles and people excercising, success depends on bad design and incomplete thermodynamic accounting. The best description I can come up with for the misplaced enthusiasm focused on this topic is:

These people want to fill a swimming pool with a tea spoon when it makes more sense to plug the leak.

Let's just examine the incomplete analysis and wrong-thinking on this topic by probing the health-club example.

Here we have people expending energy to keep fit and well by exercising on running, cycling and rowing machines. But, you may ask, where the harvested energy is coming from. It certainly doesn't come for free.

The true cost of energy

To create this power, these gym habitués have to eat food that has cost energy and materials to produce, transport, store and prepare. And those modified exercise machines have required materials, production, transport, installation and maintenance in materials and energy. Do you suppose for a moment that the energy collected is somehow green after all this? I don't think so. It has a cost.

So what about the vibration caused by engines and road movement in vehicles? There is definitely energy to be collected here, but better design that dampens engine vibration and improves suspension systems saves more energy than can be harvested.

Obviously, collecting energy from existing vehicles could make sense, but new ones should not be designed with that in mind.

How can we be so sure that my argument is all true? The laws of thermodynamics. They mean there is no free lunch. You never get something for nothing. No matter what you do, entropy always increases.

In most areas we can get a far better outcome by concentrating on better design and greater primary efficiency.

Implanted electronics in human beings

Collecting μW, mW and watts when the object of our attention should be the consumption of kW is not very smart. However, there are a few areas where the trade-offs might just work well. One such is the powering of implanted electronics in human beings such as pacemakers, respiratory and brain stimulators.

Inserting batteries into people and then sewing them up, or having wires protruding through the skin is far from ideal. Energy harvesting from arterial blood flow, heart or muscle movement is therefore very attractive. Better still, the numbers actually make sense.

Watts of energy are available but only μW and mW are required – and better still a life is saved, improved, and extended.

But on another level batteries are always nasty in terms of the materials used, manufacture processes, their disposal and recycling. For me, this is one equation that works.


Peter Cochrane is an engineer, scientist, entrepreneur, futurist and consultant. He is the former CTO and head of research at BT, with a career in telecoms and IT spanning more than 40 years.


There is a difference between cost and consequences. If you assume that: - Climate Change is real and man-made, then the consequences (costs and other) of not swapping to non-Carbon emitting energy sources outweigh the current costs. - Fossil fuels are finite, then the consequences (costs and other) of not swapping to "renewable" energy sources outweigh the current costs. It is false economy to save a billion dollars now, only to have to pay a 10s of billions in a decade's time. That said, the amount of reduction in energy consumption required should be achievable by improved energy efficiency. Do most devices really need to use Watts of power in stand-by mode? Take the cheap power packs that a lot of devices have these days. My friend and I measured 3 in our house and found they used 10W each, [b]even though the items they powered were turned off![/b] IMO, a good example of capturing waste energy is regenerative braking. In vehicles above a certain weight, the additional weight of the system can be offset by a weight reduction in the main engine.


It may not be green to use the energy expend by fitness nuts and people trying to lose weight but if harvesting some of that otherwise wasted energy were able to help reduce the impact of energy generation to the planet. . . Then the only question would be what does it cost to implement? Does it cost less to implement than to generate the same amount of energy normally? More than likely the answer to the second question is yes so it would be a moot point anyway.


You are quite correct - and all down to thermodynamics and the 'sophistic economy' of the planet - both of which seem to escape the political and management minds!


You ask the key question here ...and the one that is always overlooked by the wind farm and solar cell enthusiasts....and the answer is not always all that positive!

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