Telecom FAQ

Telecom FAQ

Explain Off-Grid Industrial Solar Power Systems to me. What do I need?

The key to designing a successful solar power system for industrial loads is to understand the power needs. Exactly how much power will need to be delivered each day? Some loads are continuous and don’t vary - great! Others are variable and will vary throughout the year. What will you need each month, particularly in winter when the solar resource is at its lowest.

Successful design means the loads are never interrupted due to lack of power. They also minimize battery cycling and depth of discharge, which helps maximize life. A good design seeks to balance system size and cost with reliability and life. The variables are solar panel size, battery capacity, and sometimes loads. Our design team can help determine what an appropriate solar solution would be, based on the delivery of thousands of systems in Canada. To get our help, ask here. However, here are some basics.

How Big a Solar Panel do I need to run an Industrial Load?

The output of a solar panel is a function of latitude, climate and temperature. Environment Canada provides solar data for all of Canada, and we have modelled the potential output for all HES Industrial Solar Modules for locations across Canada. The key for industrial loads is to understand what happens in the worst month – December. If we are successful at running the loads in December, then the rest of the year is easy; summer in Canada has 3-4 times the solar resource of December.

Our system design goals are to size the solar panel so that its daily average December production exceeds the load needs. If our load is 100 watt hours per day, we want a panel that will produce more than 100 watt hours in December. For example an HES-150W solar panel will deliver between 150 and 300 watt-hours of energy per day in December in Canada, assuming the panel is exposed to direct sunlight. This is not a daily guarantee though, December might have 5 very sunny days and 26 cloudy ones. The numbers are a monthly average and depend on local climate conditions and site.

So a basic design rule of thumb for all of Canada is to expect 1 peak hour of panel performance per day in December. A 100w panel will produce at least 100 watt-hours of energy in most of Canada. HES can model other areas more specifically. Choose a panel or solar array that exceeds the load needs.

Battery Sizing in Solar Power Systems?

Typical industrial systems use 15 to 30 days of battery autonomy in Canada. That means the batteries alone would run the loads in the field for 2 to 4 weeks without solar input. Don’t forget to derate the battery capacity for temperature – a nominal 100Ah battery is really only a 60Ah battery at -20C. Use this Battery Derating for Temperature Chart for low rate discharges as a guide. Example: A 250mA continuous load, or 6Ah per day, would need a useable battery capacity of 90 to 180 Ah to maintain the load properly in variable winter weather conditions. If the site is at -20C, then a 150 to 300 Ah battery would be recommended. The higher the battery autonomy the more reliable the system in winter.

What kind of Batteries are recommended for Industrial Solar Power Systems?

The most common batteries used in small industrial systems are the AGM (Absorbed Glass Matt), sealed, maintenance free batteries. They combine cycle performance and better low temperature performance. Key choices are the Stark SRK-121, a 121 Ah, 12V battery, or Surrette AGM-460, a 6V, 460Ah. Other options are flooded batteries, with cell capacities up to 2000 Ah or more, or even larger sealed Telecom batteries such as the Deka Unigy.

Why do I need a Charge Controller and which one is right for me?

In the simplest case, charge controllers limit the solar power going to the batteries so they don’t overcharge. Series Controllers do this with a relay that is opened after a certain battery voltage is reached. This is the simplest and cheapest route. PWM Controllers taper the current to the battery as the voltage rises through Pulse Width Modulation of the energy input. This is better for battery life as it adds a float charge to keep batteries at 100% full.
See the Morningstar Controllers for great PWM options.

Larger solar arrays use MPPT Charge Controllers. Maximum Power Point Tracking circuits monitor solar panel current, voltage and temperature and get the maximum amount of power they can out of the solar array. This type of controller works with all voltage panels, and can accept high voltage input while charging a low voltage battery, allowing you to wire panels in series rather than parallel. MPPT controllers are more expensive, but the extra energy harvest is usually worth it.
Check out MPPT Controllers here.

What is the Optimum Angle to Mount Solar Panels?

With a constant year round load, industrial solar systems are designed to maximize the solar production in the winter. While the optimum tilt angle is about 75 degrees in Canada, 10 to 15 degrees off the optimum does not have much impact in production. A steeper tilt angle helps shed snow and takes advantage of reflected light off snow. For that reason, vertical mounts, holding the solar panels at 90 degrees and facing south, are the most popular.
Check out the VPM Series of pole mounts.