OFF-GRID SOLUTIONS

Like a PV Hybrid solution, an off-grid system is a combination of power sources. It makes use of a battery storage inverter with DC/AC coupled PV solar system and in many cases a diesel generator is added to minimize the battery usage on consecutive bad weather days when PV energy isn’t readily available. The PV array and battery storage is carefully selected to ensure the solution works for what is required due to the utility grid being absent.

BACK-UP PORTION

OF THE SOLUTIONS

BACK-UP INVERTERS

The recommended inverter topology would be a low frequency transformer-based inverter as the loads connected to systems like these are generally highly inductive and capacitive loads and the longevity of the inverter running such loads depend on the topology.

 

Especially if the system is to be AC coupled with PV, only LFTB inverters are Bi-directional and can handle the back feed of excess energy from PV Grid-tie inverters for battery charging.

The battery technology recommended for off-grid use is lithium. Lead-acid batteries can be used, but there are many reasons why they're not an economical option:

  • Lead acid batteries cannot handle frequent cycling and disintegrate rapidly. 

  • Lead acid batteries take longer to charge due to their high resistance prohibiting high currents. This leads to overheating and thermal run-away.

  • The absorption period for a lead acid batteries is long and takes up to 20 hours to fully recharge.

GENERATORS

Small (<12kVA) portable generators should include functionality as: 

  • Pull or electric start. 

  • With or without an automatic voltage regulator (AVR) if used with an inverter or UPS then it should include this.

  • Generally, petrol engines. 

  • Generally, they aren't silent types. 

Large (>12kVA) stationary generators can include functionality as:

  • Manual or automatic start based on mains failure

  • Should have a decent automatic voltage regulator (AVR) – especially if it is to be used with inverter or UPS technologies.

  • Fuel type can be Gas (LPG or Natural) or Diesel engines

  • Automatic Transfer Switch (ATS) 

  • Protection devices that take care of overheating, oil pressure, output quality monitoring with automatic shutdown and more. 

  • Generally, they are silent types.

PV SOLUTIONS

  • For AC coupled solutions The Grid-tie inverters used for PV Hybrid solutions run in parallel with the load and do not physically support the capacity thereof, for this reason high frequency transformer-less topology is suitable and mostly used. 

  • For DC coupled solutions the MPPT solar chargers should be matched with the brand of inverter for best functionality, monitoring and reliability. 

  • The elaboration on various PV panels technologies and which is best is quite elongated. However, the conclusion we have derived is: 

    • If you have space restraints, use mono-crystalline 

    • If space is no concern, use poly/multi crystalline

TECHNICAL DESIGN CRITERIA

& INFORMATION

This refers to locations where there is no power from the utility. The design of these systems are very specific and unique.

The only time the size of the system can be altered is if the load magnitude is reduced or additional power sources are added to the system like: a diesel or petrol generator or other alternative energy sources like wind or hydro power.

 

The battery autonomy would be user preference, if no generator is added then careful research needs to be done around:

  • The consecutive number of bad weather days possible from historical data,

  • The frequency of the generator running and where it is added would be dependent on the storage sizing and weather data.

 

We design, supply and install these based on the customer’s needs.

Contact Us

(+27)79 449 1292

(+27)66 244 0067

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