Previous post “Steady the solar profile” introduced power control technology. It intends to transform an unsupervised power output into a stable and foreseeable output. Power control also reduces overall production and can still sometimes wrongly engage power we are not able to deliver.
Unsupervised vs power control production
Epon Energy
The idea behind small scale batteries edging is pretty straightforward. It couples the solar power plant with a small size battery to edge off part of the error. It will thereby increase reliability and eventually production intensity.
Let’s first investigate distribution of errors we observed under power control regime.
Power control errors
Epon Energy
There are many strategies that can be used to size the edging battery based on the errors observed at the solar power plant. Of course the main idea here is to keep it as small as possible as storage batteries still request significantly higher investment cost than solar panels. For the sake of simplicity, let’s just assume we choose a battery that is 10% the capacity of our solar power plant ( 1 MWp).
Our 100kW battery will then be activated during quarters when minimum production from the solar power plant falls short of the power control value forecasted for the quarter. Coming back to our example (“Steady the solar profile“), it will in this case be activated in the 5 quarters of the day were active baselining got it wrong.
Power control values with small scale edging battery
Epon Energy
In this case, as all errors were contained between 0 and 41,6 kW, small scale battery edging managed to cover all discrepancies resulting in a reliability of 100% during this day.
Throughout a whole year though you will still encounter cases were small scale battery edging does not cover for all errors. If you perform it over a 1 year period, you will likely end up with the following performances.
| Safety coefficient | Edging battery size | Reliability | Production |
| 0,5 | 100kW | 94,0% | 82,9% |
| 1 | 100kW | 96,6% | 69,6% |
| 1,5 | 100kW | 97,6% | 54,6% |
| 2 | 100kW | 98,4% | 42,5% |
Power control and 100kW battery edging for a 1 MWp solar power plant, Epon Energy
Small scale battery edging activity significantly improves performances from simple power control. It also requires as higher investment cost as you need to include batteries whose lifespan is lower than your solar power plant. It is however still way lower than a classical pv-battery coupling.
Next post “Balancing the grid with solar power” showcases the use of power control in order to enable solar power plant to take part to the aFRR downward capacity market.