Extended Parameters - Net Data Calculation


#1

It is now possible to include the power value of an Extended Parameter as part of the Net Energy calculation.

Currently Net = Consumption - Generation.

Enabling the above will turn this to Net = Consumption - Generation - v7.

The net value at each 5-minute interval is multiplied by the tariff rate.

This calculation will ultimately affect the daily debit and credit amounts.


Powerwall - Extended Parameters
#2

Hi BB appreciate you implementing this.

I have turned it on for V9 which is the battery, doesn’t seem to make any changes to the net power, it is still equal to consumption when I am drawing from the battery (only just turned the battery on at 21:25 to test).

Also I tried to recalculate tariffs and tou as well as used the live loader to try and force a recalc an none seem to make a change to the net power

system is
https://pvoutput.org/intraday.jsp?id=62806&sid=55875

thanks


#3

Currently the only change this would affect is the daily debit/credit. The net graph shown still only uses the standard generation / consumption.

The calculation also only runs when v9 power is positive, we may also need to handle negative power as well which will increase the net result.


#4

ah ok, what I was hoping for was net power to give me an import and export that matches my meter, With a battery I’d like the system to give me a cost, actual export and import and TOU on the actual import, with a battery the current cost / export / import and tou really don’t tell me much of whats actually happening, just what would of happened without a battery.


#5

Thanks for the feedback, we’ll incorporate these new features with your input - currently the system settings are fine.


#6

once again excellent thanks


#7

Looking forward to the new features mentioned by BB yesterday.


#8

Hi BB,

I didn’t realise but was another change was made to this? I’m confused now as it seems the import on the daily summary is changed to add in positive values of battery (ie what the battery supplied to the load) and the debit is calculated off that.


#9

The calculation now adds both negative and positive values. Initial implementation only used positive values.

The calculation also only runs when v9 power is positive, we may also need to handle negative power as well which will increase the net result.


#10

Sorry but now I’m really confused, I don’t see any effect of negative values and positive values are treated as import.

using https://pvoutput.org/intraday.jsp?id=62806&sid=55875&dt=20180409 as an example

Day net generation view
Export 24.425
Import 9.287
Calculated cost of -$0.50 based on the above exp / import which is system without battery effecting it

Daily Detailed View
Export 24.425
Import 18.958
Calculated cost of -$3.13

wheras the real values for the day Calculated from v8 and v9 are
Actual Export 14.438
Actual Import 0.413
Actual cost is a credit of $0.61 or so
and
To Battery 10.363
From Battery 9.313

So daily export is unchanged by battery and import is increased by the the battery when it really is reduced, in this case to near total zero.

I know the overall calculations are done on live data not daily totals but I think this outlines what I’m getting at?

Thanks


#11

The Net Calculation has been set on v9 or Powerwall.

The previous implementation would only add Powerwall values when they were positive. Now both negative and positive values are accounted for.

An example calculation at 10:15AM -

Generation = (1,105Wh - 1,055Wh) = 50Wh 
Consumption = (5,987Wh - 5,934Wh) = 53Wh
Powerwall = -3,240W or -270Wh (5 minutes)

Net = Consumption - Generation - v9
    = 53Wh - 50Wh + 270Wh 
    = 273Wh

The result is positive or export, this is multiplied by the credit tariff TOU rate.

Similarly, a negative result is import and multiplied by the debit tariff TOU rate.

The negative Powerwall readings will increase the credit amount, while positive Powerwall readings will increase the debit amount.


#12

At 10:15 there should be little to no net so no export or import, in the example why do you use efficiency for Generation calculation? Shouldn’t it be Generation = 7053-6729 = 324Wh

Net = Consumption - Generation - v9
= 53-324-(-270)
= -1Wh
so import of 1Wh from the grid (ie essentially zero) which is correct to the real situation as the battery is being charged by the excess solar at this time, If this is applied across the board I cant see why then the daily import and export debit / credit is the numbers they are that days cost should be $0.61CR

Thanks


#13

Sorry - you are right, generation should be 7053Wh - 6729Wh

Net = 53 - 324 + 270
    = -1Wh

Will look into the cr/dr calculation.


#14

Was also hoping for this. Would like to compare the figures my power company says I’m using or exporting vs what my system says


#15

I have a slightly different, but related, wish. Not sure if I should open a new thread.

I’m in the UK with no net metering but I would like to keep a record of my exported energy. I have solar and Powerwalls. The Gross UK tariff works fine for actually billing for grid and FiT payments but the result is the “Exported” column is always “-”.

If I enable “Net calculations” then Exported seems to become “generation - consumption”. What I think I would like is to be able to take the total negative Grid Flow (v10 for me) over the day and make this the Exported value and without changing the financial calculations.

Does this make sense?


#16

Gross UK export model always uses Peak Tariff * Gross Generation to calculate FIT. The Net calculations setting has no affect on the FIT.


#17

Right, thanks. But when I did try, just to see what happened, the Exported column showed the difference between generation and consumption - no account of the PW charging.

What I meant was that in my circumstances (and the maybe small number of UK users with solar and battery storage) could there be a way of calculating the Exported per day based on measure “negative” grid values (in extended parameters somewhere) ?

I would simply like to keep an eye on how much I am “leaking” over time.


#18

The Net calculation option on each extended data is designed to do this.

When the Net calculation set on Battery Flow (v7), net calculation becomes -

Net = Consumption - Generation - Battery Flow (v7)

This roughly equals the Grid Flow (v10) reported.

Unfortunately Battery Flow is in kW rather than W, so this needs to be enhanced to handle this.