Dear Editor,
It is very encouraging to see the use of solar power for President’s College back-up lights and security. But there’s something not quite right here.
The difference between a solar power system and a UPS backup system must be fully understood. A UPS backup system works from GPL and is much cheaper to buy and operate. It simply uses GPL to power the selected lights, etc, when GPL is present, and it automatically switches over to battery power when GPL fails or is outside limits (low voltage and surges).
A 2400 watt inverter charger unit of this nature will charge the batteries at 80 amps initially, with a tapering charge depending on the depth of discharge of the batteries due to the preceding blackout.
We need to remember that, if we get a 30-minute blackout, we need to urgently put that power back in the batteries to keep them topped up because we might get another blackout after an hour or so or even less. So rapid charging is the key here.
If we use solar power then we need a large bank of batteries to keep the system running throughout the hours of darkness and any blackouts which occur during that time, because there’s no charge until the sun comes up.
If we try and charge our batteries with solar power at 80 amps we need some 10 solar panels rated at around 140 watts and 12 volts. Other 24 volts panels are available but the physics is more or less the same. A 140-watt solar panel costs around $70,000, so there’s $700,000. This will be a 24 volts system so 250 amp-hours of storage will cost in the region of $260,000 and for this size of system you would probably need three times that ‒ $780,000. Add in charge control, wiring, fuses, breakers, etc, and you are well up towards $2 million. That is for 2,400 watts of power. We aren’t told how much power the President’s College system is, but the above figures show the calculations.
On the other hand, you can buy a 2,400 watt inverter/charger which runs from GPL for $358,000 locally. Couple with two batteries costing $260,000, you’ve spent $618,000 and with fuses, etc, probably $700,000. That is a whole lot less than $2million. And it has automatic seamless changeover in the event of a blackout.
Solar power is great when there is no other power source. Where GPL exists it is unfortunately still the cheapest form of energy. A UPS will take care of the blackouts and is far cheaper than solar power as shown above.
Yours faithfully,
Peter Bouchard
