Specifying Renewable Energy Demand

(For a typical domestic user)

AC Appliance:	Hours of Daily Use:	Appliance Watts =	Daily Watt hours Used:
Lights (x2)	2 max	20	40
PC Computer*	3	300	900
Printer*	4min	2.23A	2
AnswerPhone	24	400ma	115
TV/Radio	4	20	80
Re-Charging*	3	1.55A	56
Mains drill	30min	120	60

Note: Use this example for calculating other renewable energy use.
(Remember: W = V x A)

Total Daily Watt Hours Used from last column è 1,250

Allowing for 3+ days without sun, rough battery estimate è 3,760

Safe battery size in Watts, i.e. 50% discharge è 7,520

Converted to Amp Hours, at 12 DC System Volts è 600

1. Recommended Safe Battery capacity = 600 Amp Hours
(i.e. 6 x 2V 600AH cells or similar)

2. Recommended Inverter size = 900+40+60 = 1,000
(Total Watts estimated in use simultaneously)

3. Recommended Solar Array is 300 Watts, i.e. 6 x 50 Watts
NOTE: Average hours of sun estimated at 4.5 hours/day.
The generating capacity of the Solar Array is 4.5 x 300

è 1,350 Watt Hours/Day

Recommendations for optimum use of renewable energy:

1. Use 12 volt lighting (i.e. spot lamps and fluorescent strips) and appliances where ever practical. Most portable equipment (Some TVs, Radios, Cellphone charger) actually runs on 12V DC and can be wired with 12V plug to multi-socket.

2. Use lower power energy efficient mains kit. (Avoid electric cookers, heaters, kettles)

3. Use laptops not PC desktops for example.

4. Use the power when the sun is shining and the wind is blowing.

5. Switch on only when needed.