They are used in congested areas where electrical shielding might occur with other groundbeds. Deep Anode Groundbeds are remote to the structure by virtue of the vertical distance between anode and structure. Deep anode groundbeds therefore achieve results similar to remote surface groundbeds. A deep anode groundbed is an appealing choice when space is not available for a conventional groundbed or when surface soil has high resistivity and deeper strata exhibit low resistivities. Shallow Vertical Groundbeds are commonly used where space is limited.
Rectifiers are the most common power source for cathodic protection systems.
If a manufacturer were to offer each of the options listed in one reference, then that manufacturer would be offering 8,957,952 variations, assuming the choices are independent. Solar Cells can provide an dependable power supply in certain parts of the world. Great inefficiencies may result if the entire CP system is not designed with the power supply in mind. Any reliable external source of DC current will suffice - the pipe doesn't care about the power source. Scrap iron is sometimes used as an anode simply because it is available.