We use an industrial strength uninterruptible power supply because out here at the end of the grid, power outages are so common that we would lose work a couple of dozen times a year. In the last two years, we would have lost two weeks of work to power outages. Our power company is a little more candid than most, and they admit that the situation will get worse, because they have had to defer maintenance and cut crews to keep between the rock of rising fuel costs and the hard place of the state public utilities commission.

We are not alone. Prudent engineers almost always isolate mission critical process controllers and communications gear from the grid. In old systems where this isolation is not in effect — take the air traffic control system, please — down-time for the control equipment means that all those unfinished processes are just floating around in mid-air. The FAA is aware of the problem, and is installing stand-alone equipment much like that used by us here at SUN.

On a good day, sun shines on our eight photovoltaic modules, and is metered in to our 400-amp-hour nickel-cadmium battery bank. On cloudy days when the grid is working properly, our solar-electron harvest is often supplemented when our inverter's built-in charger kicks in. We estimate that over the course of the year, about 25% of our electrons actually come from the grid. Direct current electricity from the batteries is converted by the inverter into the kind of electricity our computer equipment wants to see.

Days of Autonomy

Would a system like ours make sense for you? If you want to be absolutely sure your power will not fail, you certainly need to do something. We like our solution because it will work without surprises for a couple of decades. If you are prepared to wait for the power to come back on, you only need enough uninterruptible energy to make an orderly exit from your mission critical processes. If you are as intrigued as we are by energy, and want to make it a hobby, this is a good serious project to undertake. Does it make economic sense compared to the grid? That depends on how valuable you consider your work.