<I have a few questions about type1288. The first one is related to the flow rates. Other components let users to enter the test flow rate for a specific collector but I was surprised since this Type doesn’t include this variable. Why is this? How to select the best flow rate since the one reported on the test standard report is much higher than the one the manufacturer recommends?>
The "other" collector models are based on a first-principles approach where you can solve for the impact of varying flow rate on the performance of the collector (Beckman and Duffie provide an example). With the 12975 standard, the performance is based on a best-fit parameter estimation technique from measured data. I'm not sure the 12975 equation can be solved in order to adjust the parameters for flow rates other than that at which the collector was tested. Good research question.
<The second question is about the correct manner to configure a solar array of X numbers of collector in series times Y numbers of collector in parallel. Do I have to use a calculator in order to construct such configuration or is there another way by using Type1288 only?>
A calculator - no. Simply enter the total array area in the proforma (parameter 2) and then the number of collectors in series per parallel loop (parameter 1) and the model will take care of the rest for you. test it against the full array in the studio to see if you got it right!
<The third one is about IAM for diffuse radiation. I tried to set a value of 1.015 (according to a certified report) but Trnsys got stuck and I had to use Ctrl+Alt+Del in order to end the task. So I used a value of 1 and calculations were performed without any problem. Do you know the reason for this problem?>
Well the model should have generated an error as I'm not sure how a collector can collect more diffuse radiation than is incident upon the collector... This value should be limited to one theoretically but should still work with a value greater than one. I just checked the code - the model generates an error when the diffuse IAM coefficient is greater than one so I'm not sure how your simulation is even running...
<And the last question. What is the best way to calculate the efficiency of collectors using the EN-12975 standard? How do I get this value in Trnsys?>
Efficiency is typically defined as useful energy gain divided by the product of incident radiation and collector area. So this would be output 3 from the model divided by the collector area (parameter 2) and then divided by the sum of the incident beam radiation on tilt, the incident sky diffuse radiation on tilt and the incident ground-reflected diffuse radiation on tilt:
Efficiency = Quseful / Area / (Gb+Gds+Gdg)
Jeff
---
Jeff Thornton
President - TESS LLC
22 N. Carroll Street, Madison WI USA 53703
Office: (608) 274-2577 Fax: (608) 278-1475
www.tess-inc.com
E-Mail: thornton@tess-inc.com
On 06/19/2012 8:50 am, Andrés Montero wrote:
Dear Jeff,
I have a few questions about type1288.
The first one is related to the flow rates. Other components let users to enter the test flow rate for a specific collector but I was surprised since this Type doesn’t include this variable. Why is this? How to select the best flow rate since the one reported on the test standard report is much higher than the one the manufacturer recommends?
The second question is about the correct manner to configure a solar array of X numbers of collector in series times Y numbers of collector in parallel. Do I have to use a calculator in order to construct such configuration or is there another way by using Type1288 only?
The third one is about IAM for diffuse radiation. I tried to set a value of 1.015 (according to a certified report) but Trnsys got stuck and I had to use Ctrl+Alt+Del in order to end the task. So I used a value of 1 and calculations were performed without any problem. Do you know the reason for this problem?
And the last question. What is the best way to calculate the efficiency of collectors using the EN-12975 standard? How do I get this value in Trnsys?
Thank you!
--
Andrés Montero I.
+34-680705256