Solar + storage system design is a technical and complicated work. In this paper, we will provide just a rough procedure for it. Please consult your installer or designer for details according to your particularity if it is necessary.
For system design, usually it requires an overall and predictive consideration, including site condition, natural environment, operation scenario and budget as well. And all these considerations stand in queue possibly as below:
1. Background Research
Background means where the system will be located and operated. Roughly as below.
Background research here is very important as it leads the way to a proper system design. And background research shall be as detailed as possible.
2. Operation Scenarios
Operation scenario indicates the purpose of solar + storage system, especially storage application. It is installed for self-use maximization because of lower FIT, or to decrease electricity bill because of TOU billing or demand charge strategy, or to use as backup power because of unexpected blackout, or any other reason.
Different scenario leads to a specific system capacity design and operation mode. As well, system performance ratio is considered in a higher or lower priority. Here is a general consideration on each scenario.
| Scenario | Consideration | Operation Mode |
| Tiered Pricing | Price Tiers, Monthly Energy consumption, etc. | Self-Use Mode |
| Time of Use Billing | TOU prices, Regular daily/Weekly Energy Consumption, Regular Power Consumption at Peak Prices, etc. | TOU Mode |
| Backup Operation | Blackout Regularity/History and General Lasting Time, Energy and Power Consumption Expectation During Blackout, etc. | Self-Use + Backup Mode |
| Demand Charge | Exceeding Consumption Power and Regularity, Expected energy for Peak-shaving, etc. | Peak-shaving Mode |
| Net-Zero Housing | House Consumption Energy (Monthly/Daily/Weekly), House Daily/Weekly Power Consumption Pattern of a Year, Peak Consumption Power, etc. | Self-Use Mode |
| Other | … … | … … |
3. Cost Performance Calculating
Cost performance could be a big concern, which means how much you will get paid for each coin based on the expected solar + storage system.
It is not necessary to do it here before system phenotype, unless your budget is really tight.
Cost Performance calculation here is to tell you how much the capacity of the system is most cost-efficient. The calculation shall come out with the following items at least.
| Month | Savings and Profits | |||||
| Consumption | Solar Production | Battery Use | Tier Shave | Incentives | Total Savings/Profit | |
| Jan | — | — | — | — | — | — |
| Feb | — | — | — | — | — | — |
| Mar | — | — | — | — | — | — |
| Apr | — | — | — | — | — | — |
| … … | — | — | — | — | — | — |
| System Costs / Budget | LCOE (5 years) | ||
| Hardware | Soft Cost | Total Cost | |
| — | — | — | — |
Cost performance on this stage could be very rough, a detailed calculation shall be based on the detailed system phenotype and detailed system performance expectation based on each scenario.
4. System Phenotype and Devices Selection
It means to select the proper hardware devices and system capacity, further to define the best operation mode of the system. All is based on the backgrounds and target operation scenarios of each site, and of course the family budget. System phenotype is complicated, and the details will be updated And here we just give a general rough concern on devices selection as below:
| age Inverter | MPP Trackers | Based on your roof conditions |
| Charge/Discharge Power | Power supply ability during shavings and blackouts | |
| Nominal Output Power | ||
| Backup Overload Ability | Power supply ability during blackouts, especially for conductive loads | |
| Specific Functions | Accordingly, E.g. peak-shaving for demand charge, Unbalance Output function for 3-phase system, etc. | |
| Battery | Usable Energy | Based on system phenotype |
| Max Charge/Discharge Power | Power supply ability during shavings and blackouts | |
| Compatibility With Inverter | Including communication, battery voltage, max charge/discharge current, and protections etc. | |
| Cycle Life | ||
| Other |
For details, please follow the updates on Solar Community.
5. Performance Simulation
Performance simulation is to simulate daily/month or yearly expected performance of the solar + storage system based on system phenotype and the designed operation mode. It includes at least solar production, battery performance and how the system couples house consumption behavior.
Solar production is the basis of all. PVsyst could be used to do the simulations on hourly base. (See attached for details)
And storage performance shall be simulated on the specific scenarios, here we put TOU as an example. (See attached for details)
Performance simulation could be done on a professional program like PVsyst or PV Sol etc. but for off-grid use or peak-shaving, the program is for reference only.
