Capacity factor is zero and Payback period is NaN

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Capacity factor is zero and Payback period is NaN

Hi all,
I am new for SAM. I am doing a study on CSP feasibility for Sri Lanka. I got the results and my file is attached herewith. Result shows that simple pay back is NaN and capacity factor is 0. I think that I have done some thing wrong when I entered inputs. Please help me on this.
Also my effort is to find a tariff rate which can be feasible in Sri Lanka. Please give me a guide to do that. And if you have any idea, What will be the best way to to do a feasibility on CSP in here?
Also, If I want simulate 10 MW,plant for a particular place, how can I do that? If I change gross net output and net conversion factor in power cycle tab, is that correct?

Paul Gilman


The zero capacity factor indicates that the system is not generating any power. I see that you set the solar field aperture area to 13,000 square meters, which is not big enough to supply heat to the 11 MW power cycle. For a system with no storage, you can try a solar multiple of 1 instead of specifying the field area, and let SAM determine how big of a field you need. In my test, a solar mulitple of 1 resulted in a field area of about 45,000 m2 and a system capacity factor of 13%, which is still low, but perhaps realistic given the low solar resource. Increasing the solar multiple will increase the capacity factor (and costs).

SAM's commercial financial model is for a renewable energy system that reduces a building or facility's annual electric bill and requires information about retail electricity rates to calculate the bill savings. Is that the type of project you are trying to model? The PPA single owner model is appropriate for a power generation project.

I am not aware of where to find data for Sri Lanka retail electricity rates.

Yes, you define the system's nameplate capacity on the Power Cycle page.

You may be interested in the SAM webinar on modeling parabolic trough systems, which you can find on the Webinars page of this website, under "2014 Webinars:"

Best regards,


Dear Mr.paul,
As you advised, I selected option 01 in solar field parameters instead of inserting land area. Now I can can get 20.4% capacity factor. still my pay back is NaN. Is there any wrong in my inputs.


Revised file based on your reply is attached here with.

burakomersaracoglu's picture

According to your sentence "my effort is to find a tariff rate which can be feasible in Sri Lanka" I think you should work with "Break-Even Analysis". You have three important issues 1-) Plant design, 2-) Cost Estimations 3-) Sale Price Estimations. You can easily work on SAM for plant design. For cost estimations, you can work on SAM but you need to estimate the costs in Sri Lanka. You have many different approaches here too. You can apply fuzzy models, grey models, probabilistic models, etc. You should work on some cost work breakdown structures for Sri Lanka too. May be you should study a little bit accounting issues too. For the sale price you can make simulations on SAM. You will get some financial performance measures such as rate of return and net present worth on SAM for different cost and sale price values. Afterwards when you draw your graphs for "Break-Even Analysis" you will get the "tariff rate which can be feasible in Sri Lanka". The minimum tariff rate, you should take into account and evaluate. I can help you on some approaches during your study, if you have been preparing your thesis or manuscript (only giving some guiding ideas). Some references for "Break-Even Analysis"
Good luck
Have a nice day
Burak Omer Saracoglu


Thank you Mr.Saracoglu for your valuable inputs. I'l try as u explained.


I did a parametric analysis using two inputs (TES(hrs) and Design gross out put (MW)) and two outputs (Levelized cost (nominal) (cents/kWh) and Levelized PPA price (real) (cents/kWh)). The SAM file and excel file are attached (3.Sam and SAM parametric analysis 2.xlsx) in the first Post posted on 26-10-2016. Can't we get an idea on feasibility using these results?
I have no clear idea on PPA. does PPA equal sell rate (tariff)?.In Sri Lanka there is no different tariff rates for different time slots (considering peak and off peak time periods). If I have misunderstood the definitions of these terms please advise me on that also.
Thank you,

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