About PV, Wind and Batteries

Hi Paul.
Apparently there was a problem with the previous message, because you have not answered me, I will send it to you again, and I have more questions.

Previous message:
So far the only pdf file I can see is the SWH one, I still can't see the photovoltaic and wind files.
I want to consult you about electricity rates:
- For the minimum charges of money, it happens to me that the net present value changes a lot if I put as a value, both monthly and annually, the minimum monthly energy charge multiplied by the rate of purchase of energy from the grid. As an example I am sending you my work, and in the part of the photovoltaic analysis you can see the difference between putting $ 0 and $ 150 monthly, and $ 0 and $ 1800 annually, which corresponds to what I mentioned (835.38 kWh corresponding to the energy load of November, multiplied by $ 0.18 / kWh for one month)
- I am following the "net energy metering with $ credits" format to calculate energy charges, in order to sell what I have surplus energy to the grid and thus be able to balance the net present value, but I have doubts about the management of the periods, tiers, purchase and sale prices. Here in my country the purchase price of electricity from the grid is $ 0.18 according to various sources, and so far I have not found information about the prices of selling energy to the grid. Is there a standard or efficient format that can be followed? All this I seek with the purpose of positively balancing my net present value and that the project is viable. I have seen the format that comes by default when starting a new project in SAM, but besides that I would not know how to apply another, since the regulations depend on who carries out the project, or not?

New message:
- I have a question about what the K factor of the weibull distribution means, what does it indicate specifically? It seems to me that this information is in the technical manual of the wind system, but it cannot be seen.
- In the photovoltaic summary, in the metric table, there are 2 values of the batteries that I need to understand (battery roundtrip efficiency and battery charge energy from system), what do they indicate?
- In the wind summary, in the table of metrics, there is the value "p90 energy", what does it indicate?

Best regards.

Hi Aldo,

Both of those publications should be available now. I just tested the links.

As for the electricity rate inputs, the monthly minimum charge and annual minimum charge are described in Help. Some examples:

Assume that the minimum monthly charge is $100 and SAM calculates the electricity bill for based on the fixed, energy, and demand charge to be $80 in February and $120 in March. The resulting February bill is $100 (due to the monthly minimum), and the March bill is $120 (because it is greater than the minimum).

Assume that the minimum annual charge is $800, and SAM calculates a total annual bill by adding up the monthly bills to be $600. The resulting annual bill is $800.

If you want to determine the sell rate that results in a positive net present value (NPV), you can try different values for the sell rate until the NPV is positive, or use a parametric simulation as described here: sam.nrel.gov/simulation-options.html

Best regards,
Paul.

Hi Aldo,

The links to PDF documents should be working now.

Here is a good discussion of the Weibull distribution for wind speed: wind-data.ch/tools/weibull.php?lng=en

For battery systems, the battery roundtrip efficiency is the overall efficiency of the battery, accounting for losses as the battery charges and discharges. The metric is useful to verify that the battery is working properly: A value of 100% indicates the battery is not charging or discharging, and a value below about 80% may indicate that there is a problem with the battery's configuration.

The p90 metric in the Wind summary table is calculated based on the inputs on the Uncertainties page.

p75 = total annual energy * ( -0.67 * total combined uncertainty / 100 + 1 )
p90 = total annual energy * ( -1.28 * total combined uncertainty / 100  + 1 )
p95 = total annual energy * ( -1.64 * total combined uncertainty / 100 + 1 )

Best regards,
Paul.

Hi Paul.

Unfortunately, I don't have access to those pdfs yet, and I just realized that the pdf from the uncertainties page can't be seen either.
Could you send me those 3 files through this platform, please? As I do not have the possibility to see them, and I do not know if it is a problem with the page or the pdf viewer.

Best regards.

Hi Aldo,

Please try downloading the PDF files rather than opening them in your browser. If you still have trouble you can search the internet for the publication numbers, or look in the NREL publications database: www.nrel.gov/research/publications.html .

Best regards,
Paul.

Hi again,
As you can see, I cannot download the files as they must first be uploaded online. I went to the nrel publications page, but it sends me to the same link.
Best regards.