The main purpose of this article is to establish a storage facility and to support the network. GES/RES integration is the motivator for this, but in fact, it can be integrated into GES/RES production and can be made to benefit more from this production. How Does? Let’s set the technical parameters and move on to the analysis.
First of all, units and limits;
- “up to installed power”: Here we assume that the storage system is based on MWe (ie output power). In other words, the sum of the output powers of how many inverters there are in the storage system or the grid limit.
- MWh: Storage system energy. There is an energy stored in these products from Power *Time. No reference has been made to this unit, so we can determine it.
- MWp: Total power of solar panels used in SPP projects. It is a unit that everyone who reads this article is already familiar with.
- “up to installed power”: Here again, we assume that the MWe value of the SPP is referred to.
- The charging power of the batteries (MWp-MWe or just MWe) should not fill the total MWh capacity in less than 1.5 hours. Actually recommended at least 3-4 hours. If we take into account, we should have a maximum charging power of 666kWe for a 1MWh storage facility. Recommended range is 250kWe-300kWe for 1MWh storage.
- The discharge power of the batteries should not be shorter than 1 hour. This means a maximum of 1MWe for a 1MWh plant, but that’s the limit. In order for the system to be long-lasting, this value should be around 3-4 hours, that is, in the 250kWe-300kWe band.
- Usable Energy (DOD): Batteries are damaged when they are fully charged and completely discharged. More than 20% discharge, more than 80% charge is not recommended for lithium batteries (60%DOD). For LFP (Lithium Iron Phosphate) batteries, it is still not recommended to go below 20%, but it can go up to 95% (75%DOD) during charging.
After units and limits, we have two more parameters that will affect the financial part of the design;
- How much energy would we lose if the batteries were fully charged? (Unstorable energy)
- If we choose the battery group as too large, how much kWh of storage will not be used at all, but we will have to base it on CapEx in the financial model (inactive storage investment).
If we proceed through a SPP facility with storage installed in Burdur Turkey,
Let’s consider a 1MWe storage facility. This facility needs around 4MWh of storage to properly recharge/discharge. Considering that we have established a facility with 80% DOD (15%-95%), we actually need to install 5MWh in order to deliver 4MWh. For this reason, let’s take our installed storage capacity as 5MWh.
So, if we build a solar power plant with an output power of 1MWe, how many MWp DC power would be the right choice for us? We can determine this with a few simulations.
1MWe:1MWp = Storage not used at all
1MWe:2MWp (2x overload) = 18.4% of annual production is stored. An energy of 0.05% is also lost because the storage system is full.
1MWe:3MWp (3x overload) = 23.5% of annual production is stored. 14.56% is lost before being stored.
1MWe:4MWp (4x overload) = 20% of annual production is stored (Note the decrease compared to the previous overload). 30.69% is inert energy and is lost before being stored.
As seen in this technical scan, the installed power of SPP in storage facilities can reach very high values. Of course, technical parameters are not enough for investments alone. Values to be considered are always financial (IRR, RoE, etc.) returns.
So how to optimize financial return? At this stage, many more parameters come into play, for example the aging rate of the batteries we call “State of Wear”. AC power, battery maximum charging power, battery maximum discharging power are repeatedly examined and reflected as CapEx/OpEx in financial models, according to the battery behavior parameters according to the number of cycles received from the battery manufacturer and the DOD. At this stage, the PV power is optimized again according to these expectations. At this stage, technical optimizations are carried out within the PV part itself and sensitivity analyzes are created.
For a correct integrated PV/Storage solution, more than 50,000 different simulations must be performed at the correct parameters and inserted into the financial model. Only in this way, an accurate dimensioning and projecting can be realized.
You can contact our team for storage design .