About PV, Wind and Batteries

Hi Aldo,

You can use the project after-tax cash flow to help identify ways to increase the net present value (NPV).

For example, in your "PV/Bat Condominio" case, the after-tax cash flow graph on the Summary page shows large expenses in Years 7, 12, etc. It also shows that the annual savings (positive) are very small compared to the Year 0 cost (negative), so even without those expenses, it is unlikely that this project will have a positive NPV.



You can investigate further on the Cash Flow tab to see that those expenses are for battery replacements:



The cash flow also shows that the annual electricity bill savings are small compared to the costs:



To increase the NPV for that case, you could decrease the installation cost, adjust the battery dispatch to reduce the frequency of replacements, adjust the electricity rate, etc.

One observation is that the manual dispatch schedule on the Battery Storage page allows the battery to discharge between 10 am and 2 pm from November to April, and from 3 pm to 7 pm all year round. You might consider changing the dispatch schedule to better match the load profile so that the battery charges during the day when the sun is up and discharges at night when the load is high.

You can use similar techniques to investigate the cash flow of the other cases, and make adjustments to either decrease costs or increase the value of the system.

Best regards,
Paul.

Hi Aldo,

For the solar water heating system, you may need to scale the hot water usage, number of collectors, and solar tank volume to represent multiple houses.

For the PV/Battery system, the inverter seems larger than it needs to be, but that should not affect your results unless you expect inverter power limiting or clipping to be a significant factor in your design.

Best regards,
Paul.

Hi Aldo,

I agree that SAM reports a lot of output variables. In general, high-level metrics like the net present value, annual energy, and capacity factor are useful quick indicators of potential problems, either with the assumptions, or with the design of the project. Otherwise, you can choose output variables that show aspects of your analysis that are important to you.

"DC module deviation from STC" in the loss diagram indicates how the module performs compared to its expected performance under standard test conditions (STC). It represents losses in the module's irradiance-to-electricity conversion process, accounting for temperature effects on module performance. For some locations that have a combination of high solar resource and low temperatures, the value can be negative.

The monthly energy and load graph on the Results page is useful for projects with net energy metering, where the electricity bill is calculated by comparing the total monthly generation with the total monthly load.

For all of SAM's performance models, the "System Availability Losses" are available to model factors that SAM does not consider. These may include system down time for maintenance or other situations that prevent the system from operating as designed.

Best regards,
Paul.