Northern Arizona Wind & Sun
Solar Powered Cathodic Protection Systems
Why are our CP controls better?
Contents:
Cathodic Control
Summary
Key Features
Basic Theory of Operation
Basic overview of how our CP controls can make life easier and save you money.
Our controls are designed specifically for use with solar powered systems, and are unmatched for efficiency in transferring power to the load. Older controls and controls designed for use with AC powered systems can be very costly when used with solar electric systems.
We sell two brands of CP control - AERL and Solar Converters Inc.
Both operate in a similar fashion, with direct high frequency DC to DC conversion. The Solar Converters unit is preferred for most applications that require 24 volts or less, and .40 to 15 amps. The AERL units are capable of going up to 180 volts on the standard units. For "micro control", where you need steady currents in the 1 to 500 milliamp range, the AERL "micro-CP" control is preferred.
CP Control Summary
Primitive controls abound
Even in today's "electronic age" many of the CP controls being sold for use with solar powered CP systems are pretty primitive. Many still use the old resistor taps for current adjustment. Even the most sophisticated electronic controls available have pretty poor efficiencies - typically in the 60% to 80% range. Resistor tap type controls can be as low as 30% efficient.
Save Money
These controller losses translate directly into money. If your CP control is using
up 25% of the power from the panels, the system design has to be oversized to ensure
that you will have sufficient power to put into the ground. Solar power is expensive,
but in many designs it is much more expensive than it has to be.Retrofit for a cheap
upgrade and quick fix
Many older systems have some pretty primitive controls. From what we have seen, the
majority of them are not working - some have not worked for years. Using our control
systems for a retrofit, using your existing panels, can restore operation to normal.
In almost all cases, it will improve system capacity and reliability. If your system
has been down for more than a few weeks, it is almost certain that you will need new
batteries.
Key Features
Smaller Systems
Because the our controls are almost 100% efficient, total system size almost always comes out much smaller than with conventional rectifiers and controls. This translates not just into fewer panels, but a smaller battery system, less wiring, and a smaller mounting system.Match any Ground Bed
Nearly all other controls are limited in what they can match, due to limitations on the voltage output range. Our controls can match any ground bed likely to be encountered - and can automatically adjust under changing conditions. There are no resistor taps to adjust, and once the current is set it will remain constant even if the anode to structure resistance changes. Our larger AERL controls are capable of putting out up to 24 amps at 140 volts.Can Match almost any Power Supply or Voltage Input
Standard AERL controls can take a wide variety of input voltages. The MV unit can
take input voltages of 18 to 90 volts DC, while the HV can take 50 to 145 volts. This
allows the power system to be designed for best efficiency, or can match almost any
pre-existing power system without modification. Since the down conversion is almost
100% efficient, you can use a high voltage supply even while feeding a ground bed that
might only require 1 volt or so. No more fooling around trying to come up with odd 4,
16, or 40 volt systems trying to match the battery/panel voltages to the load. Industry
standard panel and battery configurations can be used.Constant Potential Control
All Solar Converter controls come standard with potential control input. AERL controls
can be ordered with the potential control option. This allows you to use a half-cell
for control. This is useful in applications where changing bed and/or ground conditions
might require that the structure be kept at a constant potential, such as in a water
tank where the water level is not constant.Compact SizeThe controls are smaller than
almost any other similar range CP control (our "Micro-CP" units are only about 2" square,
and the Solar Converter controls are about 2.25" square). This allows all of the controls
for the system to be contained in one NEMA pole mounted enclosure, reducing wiring,
installation, and setup times.Back to Top
Basic Theory of Operation
Why our CP controls save you money and time
There are losses inherent in any system. In an AC powered system, this might cost you
(or the customer) an extra $50 a year or in higher electric bills. In a solar powered
system, that same inefficiency can cost hundreds or thousands of dollars. By reducing
those losses, the overall systems can be smaller, with fewer panels and batteries. Fewer
components equals lower costs and higher reliability. More reliability means less time
and money spent on repairs and parts.How our CP controls and systems save you money
In a typical CP system, such as for a well head, you might need 3 amps going into a
1.5 ohm groundbed. With most systems or controls, that means that you need to come up
with something that will apply 4.5 volts. (And then you hope that the ground bed does
not change). If you have a six volt system, dropping that 6.3 volts down to 4.5 volts
gives you an automatic 28% loss - which means that you are only getting $280 worth of
power from those $400 panels. With our controls, you can use a 12 or 24 volt system,
and the CP control will convert it down to 4.5 volts with almost no losses. If you are
using a 12 volts system and dropping it down to 4.5 volts, you are losing about 65%
of your money.Constant Current means it adjusts to changing groundbeds
Ok, so now you have your 6 volts system feeding a 1.5 ohm bed. Then it rains, or the
farmer next door floods it. So your ground bed drops to .8 ohms. Hmmm.. That means
that you are now feeding a lot more than 3 amps, and probably producing enough hydrogen
to do funny things to your pipe. Or, in a year or so the anode bed get all dried out,
and your bed goes up to 2.5 ohms. Now you are feeding a lot LESS than 3 amps. With our
controls, you set the current and forget it - it will adjust automatically to any resistance
from .02 ohms up to 4 ohms (with a 12 volt system, 8 ohms with a 24 volt).The CP control
is only half the story on saving power
Even though our CP controls will save you power on the anode/structure side, there are
usually some VERY significant losses on the solar panel to battery side also. For a
discussion on this, and to find out why 75 watts actually equals 54 watts, click here
to read about our maximum power point trackers, also built by Solar Converters and AERL.
See also our section on "Sizing a solar powered CP system". Northern Arizona Wind &
Sun, Inc
Toll free Telephone: (USA only) 800 383-0195 (Flagstaff)
Technical Support: 623 877-2317 (Phoenix) or 928 526-8017 (Flagstaff) FAX: 928 527-0729
Mailing and shipping address: 4091 East Huntington Drive, Flagstaff AZ 86004
Webstore for PRICING and online ordering, 24 hours/7 days a week
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For technical support, website comments, or questions email us at: windsun@wind-sun.com
© 1997-2006 Northern Arizona Wind & Sun, Inc. and the respective manufacturers and may
not be used without permission.
Note: This website is being updated, but there are still many old and/or obsolete pages,
and some broken links. Some updated pages are available at www.solar-electric.com.
Last updated: Wednesday, September 06, 2006
