Renewable energy to power a laptop
Here you find 3 ways of powering a laptop round the clock with renewable energy sources.
- Energy reference to power a laptop round the clock
- Solar powered laptop
- Human powered laptop
- Wind powered laptop
- Portable solar power
Powering an average laptop 24 hour round the clock for standard office use takes about 1 KWh [Kilo-Watt-hour]. Thats 1000 Watts consumed in 1 hour or an average of 41 Watts consumed during a period of 24 hours.
Normally a laptop is used for about 6-8 hours in an office environment. The rest of the time it just sits in a bag or is connected to a charger keeping the battery topped up. Actual daily power consumption is therefor less including weekends, off-days or whatever. As a benchmark the 1KWh is used as worst case reference.
The 1 Kwh energy equivalent
Based on 1 KWh, any eco-power source should be able to supply an average of 1 Kwh per day. To store 1 KWh in a common 12 Volt battery, a minimum capacity of 90 Ah is required. That's the energy equivalent of an average starter battery for a diesel car.
An average starter battery for a diesel car contains about 1KwH
So as a reference, 90Ah @ 12 volts must be gathered over a period of a day (24hr). That's 3.75 Amps per hour - that seems doable. Or when in a hurry, 22,5 Amps in 4 hour - but that's already unrealistic and quite heavy battery charging. The 12 volt battery would start boiling and it's life-time rapidly reduced.
Now let's look at a few eco power options to charge a common 12 volt battery with a minimum 90Ah capacity.
Solar electricity power (voltaic) is what probably comes to mind first. Roughly put, gathering 1 KWh / day using solar electricity takes a bit in many ways.
First of all, 1Kwh of solar power is not portable at all. It takes quite a bit of solar panel surface to capture 1 Kwh/day - ruining the portability of a laptop - drop-dead.
Secondly solar power is expensive - it's about a solar panel, a solar battery charger, a battery and (usually) a power inverter to power a laptop from the solar battery.
|The components of a simple solar power system|
Third location, and the angle to the sun is everything - a solar power solutions require sun, and in the best case lots of it. In northern regions of the world, gathering 1Kwh/day requires quite a few roof-top solar panels. 4th a 12 Volt / 90Ah battery is heavy - not to be carried around. Solar power a good solution for a RV / Mobile home or a boat, although not a cheap one. When the solar panel is big enough, it's possible to run a laptop directly on a solar panel when there is sun, eliminating the wait for a battery charge.
Eco Solar Power Tip
A real example: The machine has two 120 Watt rooftop solar panels - not angled at the sun. On a very good day from 10:00am to 15:00pm the panels output roughly 6 Amps. That's 30 Amps @ 24 volts -so about 720 Watts which makes 60 Amps @ 12 volts. Nearly there but still missing 1/3 of the 1KWh reference. Unfortunately all solar power is used for powering a laptop. There's more in the machine to power than a laptop.
Read about Laptop car charger (DC-DC converter) or Laptop power inverter (DC-AC converter)
Now take it one step further - Human muscle power. Say you're someone who likes to work out every day, as a cyclist or a runner or whatever. That's a lot of power for the grabbing - which could be converted into power for your laptop.
The Mk III Human Power Generator - 250 Watts of power from your legs - at maximum speed
Now, this is not a unrealistic scenario by far. Even in World War 2, people pedaled a bicycle connected to a car alternator to listen to BBC radio.
So how much can be generated from pedaling a bicycle? Roughly one can work up about 250 Watts - at maximum pedaling. So lets lets half of that at a moderate load - 125 Watts. It would take 8 hours of spinning to produce that 1 KWh reference. That's a *lot* of pedaling.
So let's say, use the laptop till a fully charged laptop battery runs out. For a DELL Latitude D610 laptop battery thats about 54 Wh [Watt - hour]. 60 Wh can roughly be produced in 30 minutes of pedaling including losses to charge the battery. That's doable - given the produced energy goes to the 12 volt battery first. Why? If the D610 laptop battery would be charged directly - it would take at least 1,5 hours of continuous pedaling - which is the time it takes to fully recharge a D610 laptop battery.
|The components of a simple human powered electrical system|
The investment would take a bicycle, a bicycle stand with alternator, a 12 Volt battery and a laptop power inverter or a more efficient DC-DC laptop power converter. The portability is a lot better than solar power, however the battery does weigh. Again for a RV / Mobile home or a boat - it's a good solution, although it works up a sweat but it's cheaper investment than solar power for sure. The best news is, a laptop can be run directly on the power source, eliminating the wait to charge a battery - but don't stop pedaling!
Now, wind power is another source of eco power. As for solar power, these are voluminous solutions. Carrying a wind turbine to power a laptop is only for those with a mobile home / rv, a boat or a static installation for a home. The solution is of course all about having wind. So what amount of wind should be there? First of all wind turbines have a “Startup Wind Speed”. The minimum amount of wind to turn the turbine blades. Skimming the tech specs of a few wind turbines, it seems the average is about 8 Mph or 13 Km/hr or about 4 m/sec. How much wind is that? That’s a gentle breeze according to Beaufort.
The “Air X” from Southwest Windpower
So how much energy brings a day of gentle breeze generate? Let’s take the “Air X” from Southwest Windpower. It’s a 400 Watt wind turbine for portable use rated at 38kwh @ 12mph per month. That’s a bit more that the “Startup Wind Speed”, hence the gentle breeze. So that’s about 1,2 kwh for a full day and 51 watt generated during 1 hour. So lets size the brochure talk a little bit down and say it’s 40 Watts generated in 1 hour. That’s not bad at all when the turbine is mounted at the correct height. Actually this is enough to run an average laptop on being used moderately, when there is wind!!. Compared to solar power or human peddling power, quite an option to consider. Specially when traveling by mobile home / RV or boat.
Read about a Simple Solar Cell Phone Charger.
Seemingly nice solutions are solar powered laptop bags. Based on experience with 2 large 120 Watt solar panels, running 2 laptops through an inverter with large capacity battery storage in between; the solar powered laptop bag really is a Mikey Mouse solution. To charge just one laptop battery (53WH) it will most likely take one day in full sun - angled correctly. If you have the time to wait for it, adjust the solar laptop bag angle, without having your laptop bag nicked, it might be worth the wait. Portability is great, unfortunately to have a decent solar power source, one needs quite a solar panel surface. Unless laptop power consumption is reduced dramatically and can be run directly on the solar power system - eliminating the wait to charge a battery.