Weighted Technical Availability

The weighted technical availability is applied to the individual inverters. Here, either the runtime (same DC power) or their different DC power is assumed.

Example case with inverter downtime*:

3 Inverter:

• Inverter 1 with a DC power of 6 kWh, downtime of 3 hours

• Inverter 2 with a DC power of 4 kWh, downtime of 1,5 hours

• Inverter 3 with a DC power of 7 kWh, no downtime

Calculation:

For the basis according to MIT, a time of 15 hours is assumed. This would be with a 100% runtime:

• Inverter 1 = 15 x 6 kWh = 90 kWh

• Inverter 2 = 15 x 4 kWh = 60 kWh

• Inverter 3 = 15 x 7 kWh = 105 kWh

Total availability at factor 1 (100%) = 255 kWh

Formula

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Explanation:

• T_{Total (DC power)} = Total time in which the plant could produce (considering the total DC power of the inverters in kWh).

• T_{Down (DC power Inverter(n))} = Not planned time in which the production of the plant is down (taking into account the DC power of each inverter in kWh).

Calculation assuming the above example:

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In words:

Availability = 45 h (255 kWh) - Inverter 1 (3 h / 18 kWh) + Inverter 2 (1,5 h / 6 kWh) / 45 h (255 kWh) * 100.

Meaning:

• Inverter 1 = 12 h (72 kWh)

• Inverter 2 = 13,5 h (54 kWh)

• Inverter 3 = 15 h (105 kWh)

Total:

• 40,5 h (231 kWh)

Calculation simplified using the numbers:

Splitting to the individual inverters:

• Inverter 1 = Value 0,8 (15 h - 3 h / 12 h) = 80%

• Inverter 2 = Value 0,9 (15 h - 1,5 h / 13,5 h) = 90%

• Inverter 3 = Value 1 (15 h - 0 h / 15 h) = 100%

*Production/energy values only assumed as examples. No liability and warranty.