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A problem with Own Consumption


Matthew
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Hello,

 

I have encountered a problem with the consumption results for one of our sites and I was wondering if you could help please. First I had a 300kw system with these details:

 

PV Generator Output

300.1

kWp

 

Spec. Annual Yield

839.66

kWh/kWp

Performance Ratio (PR)

88.0

%

Yield Reduction due to Shading

0.8

%/Year

   

 

PV Generator Energy (AC grid)

252,159

kWh/Year

   Own Consumption

180,016

kWh/Year

   Down-regulation at Feed-in Point

0

kWh/Year

   Grid Feed-in

72,143

kWh/Year

   

 

Own Power Consumption

71.4

%

CO₂ Emissions avoided

118,439

kg / year

Appliances

Appliances

607,209

kWh/Year

 

Standby Consumption (Inverter)

161

kWh/Year

Total Consumption

607,370

kWh/Year

   covered by PV power

180,016

kWh/Year

   covered by grid

427,354

kWh/Year

   

 

Solar Fraction

29.6

%

 

And then we increased the size of the system to a 1250kw system with these details;

PV System

PV Generator Output

1259.5

kWp

 

Spec. Annual Yield

834.08

kWh/kWp

Performance Ratio (PR)

87.6

%

Yield Reduction due to Shading

1.0

%/Year

   

 

PV Generator Energy (AC grid)

1,051,828

kWh/Year

   Own Consumption

252,228

kWh/Year

   Down-regulation at Feed-in Point

0

kWh/Year

   Grid Feed-in

799,601

kWh/Year

   

 

Own Power Consumption

23.9

%

CO₂ Emissions avoided

493,755

kg / year

Appliances

Appliances

607,209

kWh/Year

 

Standby Consumption (Inverter)

1,287

kWh/Year

Total Consumption

608,496

kWh/Year

   covered by PV power

252,228

kWh/Year

   covered by grid

356,268

kWh/Year

   

 

Solar Fraction

41.5

%

 

Could you please explain why the “own power consumption” had gone down from 71.4% to 23.9%. This client is looking to go completely on Solar so would use a lot more than 23.9%, is there a way I could say that they will use 100%?

 

Many thanks

 

Matt

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Hi Matthew,

the answer to your question is concurrency. Only if the higher amount of solar energy can be used just in time, you could raise your solar fraction.

In your case you produce more solar energy which you cannot use, since your appliances simply are not able to consume this overproduction. This is why your grid-feed-in is getting so much higher and your own power consumption is getting so much lower respectively.

To reach a high solar fraction (i.e. maximize your own power consumption) the only solution might be an energy shift which leads to batteries. The other way is to adapt your appliances as much into the period of solar energy production as possible. In some use cases, this is possible, in some other ones it is not.

Reaching 100% is not impossible but in many cases uneconomical. Plus it depends on how adaptable your use case is.

If you have further questions, feel free to ask.

Best regards,
Frederik

P.S.: Have a look into some graphs showing the load of your appliances and the PV power production to get a better feeling for this problem.

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