Morningstar Solar Controllers for Cathodic Protection

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As counter-intuitive as it sounds, the fossil-fuel industry, particularly oil and gas, depends on the renewable energy industry for many aspects of extraction, production and transportation.

By nature, pumping and mining operations are often very removed from any access to the electrical grid, and using generators is often prohibitively expensive and impractical based on maintenance and fueling requirements. At the well, renewables are called upon to power injection pumps, lighting equipment, and monitoring devices. Along the pipeline, renewables are often the only means of providing cathodic protection to prevent corrosion and ensure pipeline integrity. Across the board, renewable energy provides cost-effective, dependable electricity for mission-critical communications, data acquisition, metering, site security, and much more.

In practice, cathodic protection is primarily used to protect steel structures buried in soil or immersed in water and offers many advantages for corrosion protection. Electronic cathodic protection must maintain constant voltage and current to be effective. Therefore, it is important for these sites to maintain good charging control and communications typically via satellite or other wireless communications.

The “heart and brains” of any off-grid or battery-connected solar electric system is its solar controller. The solar controller will provide proper battery charging which will fully charge the batteries during the day while also protecting the battery from overcharging. By controlling the PV/solar-generated DC electricity flowing from the panels, or modules, into batteries for storage as well as sending on to run connected loads, the controller both manages the delivery and quality of the solar-produced electricity and maintains battery health—not trivial considering the fact that in an industrial system, it may involve extreme high or low temperatures and the batteries might be the most expensive component.

Morningstar’s SunSaver, ProStar and TriStar families of solar controllers have all been used with off-grid cathodic protection systems. Higher power systems may utilize multiple TriStar or TriStar MPPT controllers in parallel to charge the battery bank. Cathodic protection load control can include products from other manufacturers to provide constant voltage and/or constant current. These power supplies therefore can include DC-DC load control which may cause high current surges at times. Therefore, it is important to consider carefully whether Morningstar’s load control circuit can handle the type of surge capability for these loads. If the load current capability cannot meet the inrush current requirement for the load, Morningstar offers a Relay Driver to activate higher rated relays for LVD load control.

Communications for these sites to monitor not only the solar controller data but also the cathodic protection equipment data is very important because if the system shuts down or stops working for some reason it will be critical to visit the site to prevent extended loss of corrosion protection. Morningstar offers both serial and Ethernet communications using industry standard MODBUS™ protocol with many different solar controllers including the ProStar and TriStar families as well as the Relay Driver. These systems often include an RTU with a MODBUS™ interface which is controlled and monitored by a central SCADA system. The RTU equipment at these sights will all be powered by the solar controllers which makes it even more critical to maintain power at these remote sites.

One of the most important reasons for using Morningstar solar controllers is reliability which is the most important factor in reducing or even eliminating field-failure and downtime, since replacements can be very difficult and costly in remote locations.  Because charge controllers handle high voltages they produce heat, which means thermal management is essential to prolonging system life.  Here, charge controllers without fans have the edge, since fans have three problems. The first is that they have moving parts so inevitably fail, and in fact many solar controller manufacturers have shorter warranties on the fans in their equipment buried in their fine print for that reason. Second is that fans can suck dirt and debris into the controller’s enclosure, clogging up the ventilation and coating the electronics which results in premature failure. And third, fans need power to run, taking it away from the solar electric system as a parasitic load and reducing system efficiency.  For these reasons Morningstar has the industry’s broadest line of fanless charge controllers, including models that meet all US and International requirements for hazardous locations.

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