HES has provided equipment for thousands of Industrial Solar Power Systems operating in Canada. The key to repeat business is a solar power system that always works. A successful solar power system is one where the potential solar production always exceeds the power needed by the equipment, the batteries stay more or less fully charged, and where there are no interruptions in power delivery. This makes for a happy customer.
Here are our keys to designing a solar power system that works:
1. Understanding your loads. Some electrical loads are easy: 100mA of constant current needed 24 hours every day – or a 2.4Ahr per day load. Some may be variable: 100mA standby current with a 500mA draw when transmitting. How often is it transmitting and for how long? You need to review and sum up all the electrical load elements. Solar design usually uses the 24-hour daily total power needs as the benchmark number for system sizing.
2. Match the December solar production to the loads. Since solar output in Canada varies by season, we need to understand what the solar panel can produce during the shortest, darkest days of the year. December is the worst month for solar insolation in Canada, though this is a variable that takes into account local climate and latitude. Edmonton and Prince Rupert are at similar latitudes, but Edmonton’s winter climate offers 40% more solar energy. A rule of thumb is that a 100W solar panel facing south in an unshaded area will deliver around 12Ahr in December in Edmonton.
3. Install a minimum of 21 days of battery reserve. It hurts to buy batteries – they are expensive, bulky, and heavy to move. But an inadequate battery cycles too deeply and becomes prone to freezing; both of which reduce service life. Batteries are there to keep loads running during extended overcast periods, or if the solar panels become covered with grime, ice, or are otherwise obstructed. A rule of thumb is to install at least three weeks of battery capacity, corrected for the winter temperatures. If your load is 2.4Ahr/day, you would need 50Ahr of battery capacity at room temperature, or 100Ahr if the battery temperature is expected to reach -30°C.
If this is overwhelming, just bring your project to the HES sales support team. They have decades of experience and can advise you on the appropriate solution for your specific application. Contact our sales support team.
These are design basics – Solar 100. The next level, Solar 101, involves variable loads, mounting options and the effect on output, charge controller technology options, DC-DC conversion in multi-voltage systems, and more. Stay tuned for more articles on the issues facing solar designers.