A problem with Own Consumption

[Matthew]

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

[developer_fw]

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.