Query on Thermal Storage Dispatch Control for Physical Trough Model

Dear All / Mr.Paul,

I am a new comer to SAM.

As part of mini project in course work I need to find major details of parabolic trough system (am using physical trough model) (no of collectors,collector area) and thermal storage system (quantity of molten salt,dimensions of storage tanks),where in electrical power generation is final motive.

I am considering following situation for a specific location called Valencia,Spain.I am aware of latitude and longitude only for the place(39.4 N and -0.23 W.What I am confused/unclear is it is been indicated that DNI value is ~~2200 kW-hr/m2-yr,when converted into W/m2 =~ 251.2 , however I see that irradiation at design this value is usually indicated to ~800-950 W/m2(Also Mr.Gilman has mentioned in one of the posts that for southern spain this value is ~ 800 W/m2).

question 1)So is there any factor which needs to be considered to arrive at ~ 800-950 W/m2 range , that has to be applied to value of 251.2 ?

During sunshine hours say 8 months during an year (~245 days),the collector field has to address energy requirements simultaneously for 7.5 hours each into storage system and power block respectively.The remaining 9 hours energy requirement has to be addressed by fossil fuel/natural gas backup i.e 37.5% of time in a day fossil fill back up is to be present.i.e. (245*15 hours/8760 hours an year) implying capacity factor of ~0.42 , is this understanding correct ?

The remaining 4 months say during winter , the thermal energy required to run the power block has to be furnished by fossil fill/natural gas backup continuously with the presumption that there is no solar thermal field output.

question 2) : Could you please advise me on how do I incorporate the above situation into Thermal dispatch storage control of SAM.

I am going through the document Thermal Storage Dispatch Control for Physical Trough Model // Paul Gilman,Draft January 4 2012 and could not understand the below text from the document,,

For example, consider a system with a 100 MWe nameplate capacity under the following conditions for an hour when the sun is shining. If the TES is 60% full, the power block will operate at 75 MWe for that hour using both energy from the solar field and from storage. However, if the TES is 20% full in that hour, the power block will operate at 10 MWe using only energy from the solar field.
• Storage Dispatch w/solar = 0.25
• Storage Dispatch w/o solar does not apply in this hour
• Turbine Output Fraction = 0.75
• Fossil Fill Fraction = 0 (no fossil backup)
• Solar field output is 10% of the power block's design thermal input

My understanding : 100 MWe name plate capacity implies 111MWe gross capacity , as all discussion pertains to an hour m the thermal storage capacity = (111*1/0.3774),37.74 being power block eta level i.e. 294.12 MWhr,thermal.

60% of TES full implies (0.6*294.12) = 176.47 MWhr,thermal energy stored in TES,of which(176.47*0.25)= 44.12 MWhr,thermal energy has always to be present in the TES and the remaining amount can be supplied to the power block.

Storage Dispatch w/solar = 0.25 has been indicated , i.e. during sunshine hours (176.47-44.12= 132.25 MWhr,thermal is the contribution from TES , how do I convert the 132.25 MWhr,thermal into MWe fraction corresponding to TES ?

question 3)Once the fraction from TES in terms of MWe is known , the remaining part i.e. (75 MWe - fraction MWe from TES) corresponds to the share from only solar field as it has been defined that Turbine Output Fraction = 0.75 .Is my understanding correct ?

Additionally it has also been mentioned that "if the TES is 20% full in that hour, the power block will operate at 10 MWe using only energy from the solar field."

My understanding is that since the TES is full below the defined value i.e. Storage Dispatch w/solar = 0.25 , there shall be no contribution from the TES and all the energy to run the power block has to come from solar field only,which you have mentioned as 10 MWe.I could not understand how SAM considers the statement "Turbine Output Fraction = 0.75" , which has been predefined , is this statement ignored ? We are not defining in Thermal dispatch control(please correct me if I am wrong) "Solar field output is 10% of the power block's design thermal input" , how does SAM understand this statement ?

question 4)Could I infer/link from the 10 Mwe from solar field only also to 60% TES full situation that (176.47-44.12= 132.25 MWhr,thermal===> 65 MWe and in this situation also the solar field contribution is only 10 MWe ?

Kindly bear with me for the elaborative text and I would be eager to hear from you.

Have a nice weekend.

Best Regards
Pawan.

Dear Pawan,
1. Reference DNI
Please see the "Solar Multiple" topic in SAM's help system. You can find it under the "Parabolic Trough" heading in the Help system's table of contents. That topic has a section entitled "Reference Weather Conditions for Field Sizing" that discusses technicques for choosing a value for the reference DNI.
2. Dispatch Control
I recommend that you try different dispatch control settings and then looking at the power plant output using the Time Series tab on the Results page to see if the system is performing as you expect. You can look at variables like "Field thermal power incident", "TES HTF volume in hot tank" and "Power generated by system" to see how the solar field and TES are contributing to the system's electrical power output.
Best regards,

Paul.
 
 

Dear Sir,

Thanks for your prompt reply.

I will follow the links you informed for DNI and also try options for dispatch control.
However could you kindly answer/clarify my understanding on the thermal dispatch control text that I have written in my trialing comment,because to apply various options for dispatch control , I need to understand the basic properly.

I have gone through the document "Thermal Storage Dispatch Control for Physical Trough Model Paul Gilman, Draft January 4 2012" but still not convinced if my understanding is in order.

The fractions in the 4 cells would range from a minimum of 0 to a maximum of 1 , with regard to below cells

1) Storage Dispatch w/solar = 0.25; ---> Implies the TES shall dispatch stored thermal energy to the power block during sunshine period ONLY when minimum energy in the TES is atleast 25% of the maximum limit.
2)Storage Dispatch w/o solar =0.25 (chosen arbitrarily by me) ---> Implies the TES shall dispatch stored thermal energy to the power block during NON-sunshine period ONLY when minimum energy in the TES is atleast 25% of the maximum limit.
3)Turbine Output Fraction = 0.75 ---> Implies the turbine i.e. the power block shall deliver only 75% of its name plate capacity by using energy dispatched from TES,i.e. 1) above and 4) below {if Storage Dispatch w/o solar is set to 0} and rest of the energy being obtained directly from solar field.

But one would expect the power block to run continuously at its name plate capacity or even more i.e. at overload to generate more power and thereby revenues.So I suppose I need to adjust the 4 cells accordingly so that I can see/check in the graphs if my power block capacity is met or not.Is my understanding correct??
4)Fossil Fill Fraction = 0.25 (no fossil backup) ---> Implies the fossil fuel shall dispatch energy corresponding to 25% of name plate capacity ,since there is no maximum limit of energy set as in the case of TES.
5) Should the sum of all the four cells be equal to 1 ??

Kindly reply so that I can get convinced about my understanding.

Thanks and have a nice weekend.

Regards
Pawan.