The purpose of a regulator in renewable energy is to prevent your battery bank from being overcharged when full. There are a few types on the market but first let's look at how regulators work. There are 4 types of regulator on the market that are applicable to solar or other renewable energy power generation. these 4 types are: Switching, pulse width modulated (PWM), maximising and load diversion regulators. Some types do either PWM or load diversion.
Switching regulators: These regulators are simple units designed for smaller solar arrays and simply switch off the solar array when a set battery voltage has been reached (high point cut out) and switch back on the solar array when a lower voltage has been reached (low point cut in).
PWM regulators: PWM regulators are the most common and work like a switching regulator except the switching is at a very rapid rate. They usually offer more sophisticated charging profiles and instead of having a high cut out point a PWM regulator will maintain preset voltages to ensure a complete charge profile.
Maximising regulators: These regulators allow for big differences between the solar array voltage and the battery bank voltage and allow commonly available grid feed solar panels to be used in battery charging situations. In low light and in cold climates they can also boost the efficiency of the solar to battery charge rate by allowing the solar panel to operate at its most efficient voltage.
Load diversion regulators: Switching, PWM and Maximising regulators all simply disconnect the solar array from the battery when it is not required. This sort of regulation is not suited to wind generators or micro hydro generation because simply disconnection these devices can allow them to over speed dangerously with result and device damage. Load diversion regulators take the unneeded power from the device they are regulating and switch it to another device, usually an air or water heating element.