Energy notes

These are my fairly raw notes from working through our energy availability issue after getting some help on motorhomefacts.com — running 2 laptops all day, self-sufficiently, to allow us to wild-camp more.

I couldn’t find a solution that was sufficiently satisfactory to lure us away from paid, powered sites. If we get desperate, we may buy a generator one day, though.

For powering our two laptops, I considered fuel cells, solar, pedal power and a generator that was recommended to us.

Example usage

See ‘Laptop power usage‘ below for notes on power usage. Figures are pessimistic, erring on the side of greater power consumption. Inverter overhead is ignored, with the assumption that we’d find a 12V power supply instead.

Heavy use

Moderate use

Options

Efoy fuel cell

• EFOY 900 provides 900 Wh/day: £2,195 ($3800 AUD)
• 10 litre fuel cartridge: £38.81 ($67 AUD) ($6.70/litre)
• 1.1 litres of fuel per kWh output
• Typical 800 Wh day: 0.88 litres = $5.90/day

Bike-based generator

• Windstream make a Bike Power Generator for US$595 ($667 AUD) (BYO Bike)
• Produces ~150W while pedalling
• To produce 800 Wh: 5.3 hours of pedalling.
• To produce 595 Wh: 4 hours of pedalling.
• Maybe we can capture passers-by and make them pedal.

Solar

• 140W solar panel: £1,250 ($2,163 AUD)
• Using the rule of thumb of 0.3 * rated capacity = amp hours/day: 42 Ah/day (60% of 70Ah, or 95% of 49 Ah)
• Or, assuming 5 hours of sunlight per day, and 50% output from the panel:  350 Wh/day (29Ah) (40% of 800Wh or 59% of 595Wh).
• 2 x 140W panels may satisfy the requirements, but are too expensive, and there may not be room on the roof

Generator

• Honda EU10i: £537-580 (~$1000 AUD)
• Rated at 1kW, and runs for 8.5 hours at 1/4 load (250W, presumably) with a 2.3L tank.
• If motorhome’s battery charger runs at 20A, would need to run for 3.5 hours a day to replace 70 Ah, or 2.5 hours/day to replace 50 Ah.
• That is, a little over 1L fuel/day for 70Ah days, or 0.7L/day for 50Ah days.  If fuel is ~£0.9/L ($1.55 AUD), that’s $1.55 or $1.08/day.

Summary

• Fuel cell: Too expensive
• Bike generator: More exercise than anyone should ever have to put up with. That just can’t be healthy.
• Solar: Too expensive, logistical issues fitting 2 panels
• Generator: Viable, aside from environmental issues (fuel usage + sound pollution)

Our conclusion: We’ll just stay in caravan parks/CLs/Aree Attrezzatas/etc. Or kidnap a vagrant and set him to pedalling.