I’m looking for a solution that will allow a continuous electricity backup if the electricity supply grid goes down but without relying on a backup generator but instead using a solar PV array. The electricity generated needs to be stored (obvious choice would be a battery array using deep cycle maritime batteries).
The solar PV array would be constantly in use providing a reduction in electricity drawn from the grid with the consequent energy and financial savings.
After doing some calculations the PV array would need to be about 1.2 to 1.5 KW. This was calculated after carrying out an online solar energy calculator, which will provide an average over the year of 5.5-6KW/hrs per day. Saving $11/week or $572/year. (This would cut current electricity bills by about 30-40%)
By using energy efficient lighting using a combination of modern CF and LED lighting the total lighting load (upstairs and downstairs ring mains) for an average 3 bedroom house would be around 250-300 Watts peak and the normal continuous load would be around 60 Watts say for 6-8 hrs/day i.e 0.48 KW/hrs
Refrigeration load would be a continuous 200W i.e 4.8 KW/hrs per day
Communications and entertainment (Low powered PC with Digital Satellite card, Digital TV card, cable router and amplifier/speakers) would account for 130-150 Watts again for 6-8 hrs/day. i.e 1.2 KW/hrs per day
There would be no other appliances except for possibly a microwave oven i.e 600 Watts for 30 min maximum/day i.e 0.3 KW/hrs per day.
A generator around 2KW would be used as a backup to top up the battery array if solar conditions were poor during an emergency grid outage.
Therefore peak power usage would be no more than 1.25 KW at any one time. Typical power would average 250W over 24 hrs
Therefore over a continuous 24hr period of operation the battery array would need to be around 800-900 AH
There is a product called the
Xantrex Powerhub 1800 which is essentially a powerful UPS but has additional inputs from solar arrays, wind turbine and generators etc but can only support a 420 AH battery array.
Costs for the setup would be around approx $6000 for the PV array, approx $1400 for the Powerhub, approx Deep Cycle Batteries $1500 and modern lighting CF and LED $800 and cabling $250 and approx $1500 for the generator.
Total Project cost would be approx $12,000
Time to recover initial project cost approx 20 years.
Would this be a worthwhile project?