Loss and efficiency in battery at Storage system(peaking shaving) with grid limited

[NancyShen060920]

Hi there,

My name is Nancy, i am wondering that how you define the (maximum and euro)efficiency in peak shaving storage system(project design/storage/peaking shaving/peaking shaving)?

In my project, it is a grid connected system with battery stored. And the battery connected in the AC side.

When we consider the loss and efficiency in the battery side(project design/storage/peaking shaving/peaking shaving), there are two efficiency in the battery input charger and battery to grid inverter(basis charging and discharging). The maximum efficiency and EURO efficiency(equivalent)(project design/storage/peaking shaving/peaking shaving/), What kinds of factors are impact those efficiency? For example, in terms of charging, Are the efficiency including the whole battery system, such as PCS(Energy Storage Power Conversion System) efficiency, transformer system, cable connect between the batteries and battery bank to PCS, PCS to the transformer? Or just the efficiency of battery itself(battery charging efficiency)

And comparing with AC loss and external transformer loss in detaid loss, Are these efficiency overlap with the AC loss after the inverter/external transformer loss(Detailed loss/ohmic losses/AC losses after the inverter(full system)?

Thanks for much

Nancy

[André Mermoud]

For the barttery system management, you have

- losses of the charging device (AC > DC converter) represented by an efficiency curve as for inverters,

- losses of the battery itself (difference Charging / Discharging energy)

- losses of the inverter device,

- all losses at the output of the inverter may also be specified (AC wiring, transfo losses) in the same way as for a usual system.

[Bryan Joshua]

How about the Cooling system or the Auxiliary loss of the BESS? at what losses does it include?
Also, can we simulate a 25 years generation and put the 25years forecast degradation of the BESS?

 

[André Mermoud]

In the "detailed losses", you can define  "Auxiliaries": this defines some auxiliary consumption, which may be a fixed value,  or with a part proportional  to the produced power (because the cooling needs may compensate the Power inefficiency loss of the inverter, about proportional to the produced power.

This auxiliaries is accounted as a loss of the system, i.e. deduced from your PV production when selling it to the grid.

Now it is you job to decide which losses you want to include in this contribution, i.e what you want to deduce from the produced energy.

The aging tool  (button  "Advanced simulation" => Aging tool) ")  takes the ageing of the battery pack into account from year to year. It will define when changing the batteries if necessary.

 

[Bryan Joshua]

Thanks. The aging tool only consider the PV module degradation. Is there any other way to consider the BESS degradation on the .BTR file itself?
do PVsyst have separate tab for BESS degradation? See attached BESS degradation sample.

 

Also, the PVsyst BESS loss parameter only shows below losses. But in actual since the Battery RTE is 85% the battery global loss should be 15% and not 1.73%, right?
may we know the reason why only 1.73% is reflected on the losses.

Lastly the auxiliary loss parameter only considers the PV side. while the Cooling loss on the BESS happen in the BESS side the result will be incorrect if we consider the BESS cooling loss on the PV side. since our system is Grid type self-consumption and allows solar injection into grid. 

Thanks

 

[André Mermoud]

In PVsyst, the wearing state of the battery is evaluated through two variables:

-  SOWCycl = wearing state due to cycling 

-  SOWStat = static wearing state (specified lifetime whatever it is used or not).

These indicators are evaluated  during each simulation. When using the "Aging tool", they are "chained" from one simulation to the next one.

This indicates when you have to replace the battery pack. You can get them in the results:

These losses are based on the battery definition properties.

Now in the reality, the aging of the battery results in a continuous diminution of the capacity. The lifetime is usually defined as the time when you attain 80% of the nominal capacity. The simulation of PVsyst doesn't take this capacity diminution along the years into account.  This is not very important, as the Capacity is not a crucial parameter during the system running: a variation of 20% has a very low effect on the final performance.