BESS-grid connected systems

[Mariyam]

I am simulating a PV farm with 2 cases of BESS: 
Case 1: 12.1 MWp with 10MWh
Case 2: 12.1MWp with 40MWh 

After generating the results from the report, I can see that the % of grid consumption is higher in the 40MWh case than the other. Also, the stored energy is lower in the 2nd case, which is puzzling. I have attached the losses diagram. Can someone explain this discrepancy?

 

[Linda Thoren]

Hello,

The system is not completely the same before the battery (you have a 9.2% loss to the right compare to 2.3% to the left), thus you have less solar production to the right.

Also have a look at for instance the charging and discharging power. 

Kind regards

[Mariyam]

Thank you for clearing my doubts regarding the grid consumption. 
Like you said, I do realise the losses are higher in the second case (due to auxiliary power required for cooling of BESS), and so it makes sense to have lower solar production & higher grid consumption to meet the demand.

But why is the percentage of stored energy lower in the second case? Does this value depend on the charging & discharging power?

[Linda Thoren]

If you have less production, there will be less energy to charge the battery with, no matter the size of the battery. But it could indeed also depend on the charging and discharging power 

[Mariyam]

Thank you for clearing this. 

Is there any relationship between the values EDirUse, EBatDis, E_Solar, and E_User? I am trying to find what is the generation from the BESS and solar (only) as per hour values and add it to gain the total energy (E_Solar). I have attached the hourly generated graph and table FYI. 

 

[sagar b]

Hi Mariyam,

E_user= EfrGrid+E_Solar; where E_Solar is total solar generation- injected energy from solar to grid.

EDiruse= [((E_Solar+E_grid)*% of direct use)-E_grid]

E_user= Efrgrid+E_solar

E_solar here is energy to user from solar but to know the total solar generation from your plant, you need to add E_grid.

In your case, E_grid is 0.  So, E_Solar= Total solar generation.

You can get it all from the bottom part of loss diagram.

Hope this helps.

 

[Mariyam]

Hello Sagar, 

Thanks for your reply. The losses diagram also states the percentage of grid consumption, how do we arrive at this value?

Its clearly not the solar share from the user's needs? Then what does it indicate?

[Linda Thoren]

Hello Mariyam,

The the percentage of grid consumption in the loss diagram shows how big portion of the time you are consuming from the grid. In the bottom of the graph it is indicated how much energy is consumed from the grid.

For example, if the electricity consumption is far larger than the PV production, you will have grid consumption 100% of the time, and still have self-consumption to user from solar. 

[Mariyam]

Thank you, Linda! This clears a lot of things!!