INNOVATION and RELIABILITY
Preliminary....Not yet released.
SOLAR PUMPING CONTROLLER (maximum power point tracking)
Panel Connection.
Due to the variety of input voltages offered by manufacturers of MPPT regulators and pumping controllers, the user needs to be aware of some choices which will enable them to select the best option for their situation.
1/ Series Connection. Ultimately this is the best configuration for MPPT use, as it has 2 advantages. First it means lower current through the system wiring and therefore less voltage drop in the cables. Secondly it gives more headroom for the voltage to drop when the system is loaded down. Disadvantages are that for technical reasons, the higher the voltage input, the more stringent the design criteria are for the electronic side of the system, this means more space, and also mosfets over 100v drain breakdown voltage become quite expensive and their 'on' resistance is significantly higher than for those under 100v. So..what is gained in smaller wiring may well be lost in the switching devices.
2/ Parallel or series Parallel connection. For motronic MPPT devices, the maximum input voltage at this point is 60v unloaded. Our units are optimized around a 24v output system. 24v panels produce their maximum power transfer at around 34 to 37 volts, which they produce under good sun conditions.
Let's look at a Suntech 175w 24v panel.
The output voltage unloaded is 44.7v, clearly MUCH higher than it's rated voltage of 24v. Then we notice that the maximum power transfer is achieved at 35.8v again, this is much too high to be used for charging batteries or running a 24v pump motor.
REGULATOR. If a simple regulator is used, a lot of power will be lost in the regulator itself. If it is a pwm type (like Plasmatronics or Steca or others) it turns 'on' fully then 'off' fully and applies the full panel voltage to the batteries or pump. The panel is loaded down and does not (cannot) maintain the ideal voltage for maximum power transfer.
MPPT This is where the technology of an MPPT is helpful. Motronic uses a buk or step down converter with syncrhonous switching for maximum control of the panel voltage. The voltage output and current are measured accurately and the product (power) is calculated and the load is adjusted to maintain the panel voltage at the ideal for power transfer. Hence the output will be 24v but the input will be 35.8v with very little loss internally.