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<< Click to Display Table of Contents >> Pumping Systems Configuration |
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See also "Pumping systems: procedure".
Several system layouts and coupling strategies are possible:
| - | Direct coupling between the PV array and the pump(s), without power converter unit. This is of course only possible with DC motor pumps. Although often used owing to its simplicity, this layout requires a very careful electrical optimization, and cannot yield a good efficiency in any operating conditions. |
| The direct coupling mode may be improved by several special regulation modes: |
| - | Booster device, electronic device for overcoming high starting current due to friction losses, |
| - | Cascading when using several pumps, |
| - | Array reconfiguration (half-array serie/parallel switching), not common but rather simple technique involving simple controlling device with relays. |
| - | Power conditioning units, matching the voltage/current PV characteristics to the specific electrical needs of the pumps (DC motor behaviour are mainly current-driven) using modern electronic switching techniques. On the solar side, these can be either "Maximum Power Point Tracking" (MPPT), or with "fixed voltage" DC input. Such a device is of course necessary with AC motor pumps (inverter). |
| - | Battery buffered systems, where a battery is used to regulate the pump running in time. The PV-Battery behaves like a standard stand-alone system, and the pump is always running in optimal conditions, at the nominal battery voltage. A strategy of switching the pump ON/OFF according to the irradiance level may be used to minimize the battery solicitation. Nevertheless the simulations show that a high charge/discharge rate is unavoidable in this configuration, leading to rapid wearing of the battery pack and a high rate of replacement. |
You can have a look on the simulation Results for comparing the performances of these operating strategies.
Controller
By the way, even the simplest configurations (direct coupling) require the presence of a control device, which should at least assume the following functions:
- Manual Power ON/OFF
- Pump OFF when tank is full
- Pump OFF when aspiration level is below the pump inlet (preventing dry running),
- Eventually motor temperature protection,
- Protection against powers, currents or voltages which overcome the maxima specified for the pump (s).
The sizing constraints are very dependent on the system layout.