Nilanjan Mahata Nilanjan good question.

I head up an Off Grid Standalone System Design and PCE manufacturing Company (Solar PV + Battery + Converter's), and for the last 15 years have designed, manufactured, installed and supported our Off-Grid Power Solutions (10 - 100 kW Solar PV) plus Battery Storage using only DC Coupling designs via the system DC Bus backbone concept.

So you can easily draw your own conclusions from that statement on what our company favours between DC verses AC coupled designs.

The reasons are understandable - at least from our design perspective:-

(1) Solar PV junction DC current quality is about as good as it gets. Negligible noise; negligible ripple and most suitable as a clean charging current for batteries.

(2) Solar PV is not just an open-ended DC current source, it has important equivalent circuit attributes that can be exploited fully in the hands of an experienced DC Energy System design engineer. I recommend that you learn as much as you can about PV Junction Equivalent Circuit attributes Nilanjan, and how they can be exploited in best practice design concepts.

(3) Circuit/System Efficiency and cost-effective designs. Most important and not often focused on fully by Energy System designers.

Think more laterally about multi power source DC circuit design Nilanjan involving PV and Batteries. Predictably, you seem focused on DC Voltage considerations rather than DC current considerations and I recommend that you think more about this point and particularly as you learn more about the equivalent circuit attributes of a Solar PV Array and how they can be exploited as an "intrinsic controlled current limiting power source" . Voltage is a very important design consideration when sizing PV and Battery DC source designs; but current is (more) important to understand fully.

Lastly but most importantly is "circuit robustness" and durability through MTBF conscious power circuits design. You know what I mean by that - limit the risk through robust hardware design considerations focusing on Higher DC Bus Voltage and Lower Current designs. Preserve and protect the life span of batteries by clever charging and discharging current management design controls.

Good luck with your projects moving forward.

DC coupling is better with respect to high efficiency and stability of the output. In contrast, it will be more complicated and expensive.

Dear Mahata,

If you mean by solar plant the PV panels not thermal.

In this case, your source is DC and the storage systems are mostly DC so there is no need for AC coupling. By this you will add an extra system which means high cost, low efficiency....

Nilanjan Mahata Nilanjan good question.

I head up an Off Grid Standalone System Design and PCE manufacturing Company (Solar PV + Battery + Converter's), and for the last 15 years have designed, manufactured, installed and supported our Off-Grid Power Solutions (10 - 100 kW Solar PV) plus Battery Storage using only DC Coupling designs via the system DC Bus backbone concept.

So you can easily draw your own conclusions from that statement on what our company favours between DC verses AC coupled designs.

The reasons are understandable - at least from our design perspective:-

(1) Solar PV junction DC current quality is about as good as it gets. Negligible noise; negligible ripple and most suitable as a clean charging current for batteries.

(2) Solar PV is not just an open-ended DC current source, it has important equivalent circuit attributes that can be exploited fully in the hands of an experienced DC Energy System design engineer. I recommend that you learn as much as you can about PV Junction Equivalent Circuit attributes Nilanjan, and how they can be exploited in best practice design concepts.

(3) Circuit/System Efficiency and cost-effective designs. Most important and not often focused on fully by Energy System designers.

Think more laterally about multi power source DC circuit design Nilanjan involving PV and Batteries. Predictably, you seem focused on DC Voltage considerations rather than DC current considerations and I recommend that you think more about this point and particularly as you learn more about the equivalent circuit attributes of a Solar PV Array and how they can be exploited as an "intrinsic controlled current limiting power source" . Voltage is a very important design consideration when sizing PV and Battery DC source designs; but current is (more) important to understand fully.

Lastly but most importantly is "circuit robustness" and durability through MTBF conscious power circuits design. You know what I mean by that - limit the risk through robust hardware design considerations focusing on Higher DC Bus Voltage and Lower Current designs. Preserve and protect the life span of batteries by clever charging and discharging current management design controls.

Good luck with your projects moving forward.