Solar power systems for polar instrumentation: why night consumption matters

Autonomous instruments, powered using solar panels and batteries, are a vital tool for long-term scientific observation of the polar regions. However, winter conditions, with low temperatures and prolonged lack of sunlight, make power system design for these regions uniquely challenging. Minimising winter power consumption is vital to successful operation, but power consumption data supplied by equipment manufacturers can be confusing or misleading. We measured the night consumption (power consumption in the absence of sunlight) of 16 commercially available solar regulators and compared the results to the manufacturers' reported values. We developed a simple model to predict the maximum depth of discharge of a battery bank, for given values of regulator and instrument power consumption, solar panel size, location, and battery capacity. We use this model to suggest the minimum battery capacity required to continuously power a typical scientific installation in a polar environment, consisting of a single data logger (12 mW power consumption) powered by a 12 V battery bank and 20 W solar panel, for eight different models of solar regulator. Most of the tested solar regulators consumed power at or below the manufacturer's reported values, although two significantly exceeded them. For our modelled scenario, our results suggest that the mass of the battery required may be reduced by a factor of 26x by exchanging a solar regulator with high night consumption for a more efficient model. These results demonstrate that a good choice of solar regulator can significantly increase the chances of successful year-round data collection from a polar environment, eases deployment and reduces costs.