System overview
A common form of CP, or cathodic protection, is called impressed current. Impressed current means that a current is impressed between the buried structure and and an anode. This forces a reversal of the current, and causes the anode to be consumed rather than the pipe.
This current will vary considerably, depending on the surface area of the underground pipe, the soil and other factors. A typical gas wellhead is usually in the range of 2 to 6 amps, larger pipelines are usually in the 8 to 30 amp range. Where grid power is readily available, an AC to DC rectifier is usually used. In remote areas, the DC current is commonly supplied by a solar electric (PV) system
Functions of different components
Solar panel: Converts sun light into electric current. Rated in terms of peak watts produced. Apex stocks panels from 10Wp to 185Wp (70WHr to 1,295WHr @ 7 Hr Irradiance). For higher requirement, multiple panels are used which are connected in combination of parallel and series connections.
Solar charge controller: Regulates charging and discharging of the batteries to optimize the ‘retained charge’ of the batteries and maximize the life of the batteries. Apex stocks controllers from 3Amps to 140 Amps (PV current or Load current). Parallel connections of controllers for higher capacities is possible by using current sensors in the loop of master-slave combinations. For SHS system with 1 panel, a controller of 12 Amps is sufficient.
Batteries: Reservoirs of charge current that is being produced by solar panels, batteries are connected in combination of series or parallel to match the system voltage. Apex stocks batteries from 7Amps to 415Amps in different voltages.
CP Controller: Depending on the thickness of the pipe, soil type and other factors, certain level of ampere is ‘pumped’ into the pipe for protecting it from corrosion. This pumping of current is done at a particular voltage difference between the cathode an anode. CP Controllers adjusts the voltage automatically to reach the certain level of ‘fixed’ amperage.
Reliability: All the components are extremely reliable. Solar panel usually has a life of over 30 years (crystalline types). Inverter and charge controllers are also very reliable. Batteries being deep cycle type would typically last 4-6 years after which they need replacement.
Viability: For areas where there isn’t access to electricity, solar is the only way to go. For battery based system, per peak watt of installation has a cost of USD 8 – USD 10. This produces usable power of about 5 watts (in good sunny weather).
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