再生可能 エネルギー
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- Nov 28, 2019
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I am reviewing for an acquaintance an installation proposal from an installer, not a DIY, for a small grocery store.
The daily power grid consumption is 60 kWh, under 220V, mostly to run 8 professional fridges and freezers, and indoor and outdoor lightings.
It seems to make sense to use Solar power to lower the electricity bill, but the Solar input should be limited to 10 kW
from requirement from the power company for the type of contract at that location.
The use of Power walls, also limited to 10kWh, is not yet decided because of the additional cost.
The installer choice is to use two 5KWA Huawei Sun2000 inverters.
Looking at the specifications of those inverters, the Max Output Current is
25A (on Grid) or 22.7A (off Grid) for each inverter,
based on the AS 4777.2: 21.7A Grid security guidance.
Doing some quick napkin calculations, the hourly consumption is about 2.5 kWh so under 220V there is an average of 12 Amp.
If the Fridges are running about 30% of the time (5 minutes On, 10 minutes Off) there are about 3 fridges running all the time,
so each fridge would use 800W or 4 Amp under 220V. When the fridge's motor is starting I estimate the In-Rush current to be around 5x or 20Amp.
My concern is that the type of inverters proposed seems to be a little bit on the border line regarding the In-rush current,
especially in case of short power failures of the Grid, which occurs quite frequently at that location.
I would be interested getting some opinion on this installation, in particular:
The daily power grid consumption is 60 kWh, under 220V, mostly to run 8 professional fridges and freezers, and indoor and outdoor lightings.
It seems to make sense to use Solar power to lower the electricity bill, but the Solar input should be limited to 10 kW
from requirement from the power company for the type of contract at that location.
The use of Power walls, also limited to 10kWh, is not yet decided because of the additional cost.
The installer choice is to use two 5KWA Huawei Sun2000 inverters.
Looking at the specifications of those inverters, the Max Output Current is
25A (on Grid) or 22.7A (off Grid) for each inverter,
based on the AS 4777.2: 21.7A Grid security guidance.
Doing some quick napkin calculations, the hourly consumption is about 2.5 kWh so under 220V there is an average of 12 Amp.
If the Fridges are running about 30% of the time (5 minutes On, 10 minutes Off) there are about 3 fridges running all the time,
so each fridge would use 800W or 4 Amp under 220V. When the fridge's motor is starting I estimate the In-Rush current to be around 5x or 20Amp.
My concern is that the type of inverters proposed seems to be a little bit on the border line regarding the In-rush current,
especially in case of short power failures of the Grid, which occurs quite frequently at that location.
I would be interested getting some opinion on this installation, in particular:
- I think that installing Relay Timers for each fridge should be recommended to avoid having too many motors re-starting at the same time.
- When running motors I read that it is recommended to use low frequency inverters, mostly because of the in-rush current.
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