Portable Solar Power

[Tarrel]

3kW will need about 30 square metres of panels in the UK. Not really practical for a portable setup. Also, current costs for panels work out about 80 pence per Watt, that's excluding the battery, inverter, charge controller, etc., so you'd be looking at over £2,000 just for panels.

Someone's got the sums wrong somewhere.

The way to work it out is:

1. Calculate the daily energy need, for example (and these are figures picked out of thin air):
Portable flourescent lamps x 2 at 15W each, used for 3 hours per day = 90Wh (Watt-hours) per day
iPad charging 2 hours a day = 2 x 10W = 20Wh per day
Fridge, taking 300W, running 24 hours a day and "kicking in" 10% of the time = 720Wh
TOTAL so far: 830Wh per day

2. Calculate the size of solar array you need, based on your demand and expected hours of sun, e.g.:
Assume 4 hours of sun per day. Panel size needed = 830 / 4 = 210W (roughly)

3. Calculate the size of battery bank you'll need to store the electricity and even out the peaks and troughs of production and demand. I'd go for, say, two full days worth of demand, so if you have two really rubbish days of no sun, you'll still have energy in reserve. 2 x 830Wh = 1660Wh. Using "Volts x Amps = Watts", and assuming 12V batteries, that means 138 Amp-hours worth of batteries.

This is very rough and doesn't take into account losses in your inverter, etc., but it's a starting point.

HTH.