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Hi TRNSYS users,
I am trying to model a district heating network which uses horizontal ground heat exchanger. The ground above the GHX would absorb solar radiance and heat the ground which would eventually affects the buried GHX.
Besides this, I wanted to use a PVT system to generate heat and electricity. The electricity would be stored in a Lead acid battery. I need a controller that compares the PVT fluid temperature and compares it to the GHX outlet temperature and starts a pump to feed the PVT in case the PVT fluid temperature is 4 degrees more than the GHX fluid temperature. the pump would also stops working if the temperature difference would drop below 1 degree. In this way, the extracted heat can be used efficiently. Furthermore, PVT would not be fed in case the temperature drops below zero (the soil temperature would not go below zero)
I used a Microprocessor controller (Type 40) with the T_On deadband: comparator as 4 and T_Off deadband: comparator as 1. However, I receive the following error:
"13 Parameters are required and 11 Parameters were specified". How to solve this problem?
Besides that, I need the heated fluid to be stored in a tank and use it in different stages as follows:
T>55: The water directly exchange heat with a DHW loop without mixing.
T<20: The water directly exchange heat with GHX loop without mixing.
I want the system to give priority to heating the DHW loop and in case it is not capable of doing so, I want the fluid to heat the GHX loop.
I would appreciate if you could guide me for this problem.
Thanks
Shams
ShamsoddinGhiami Topic starter
29/04/2024 3:46 pm
For the first part of the question, what would be the alternative option for Microprocessor controller?
Regarding the issue with the parameters in Type 40:
In Type 40, there should be one or more "Controller Output" parameters to specify the output mode for each output of each controller mode. Simulation Studio sometimes has trouble cycling parameters that are dependent on multiple other parameters, and as a result, these parameters sometimes don't appear by default. You can force the hidden parameters to appear with the following order of operations:
- Change the "Number of controller modes" to 1.
- Change the "Number of outputs" from 1 to any number between 2 and 18.
- Re-set the "Number of outputs" back to 1 (or set it to whatever value you like).
- Re-set the "Number of controller modes" back to 2 (or set it to whatever value you like).
Following the above instructions in that order, you should see the same number of controller modes and number of outputs as the default proforma, but a "Controller Output" parameter will also appear for each controller mode, and the total number of parameters specified will match what TRNSYS expects.
Users are welcome to use the microprocessor controller if it suits their needs, but I personally would recommend it may be easier to use the differential controller (or perhaps an equation block to combine signals from the differential controller and other controllers) than to use Type 40.
The first part of your scenario would be the perfect application for a differential controller (Type 165 in the standard library or Type 911 in the TESS Controllers library). You can see a differential control example in the SDHW example in the Examples folder of your main TRNSYS directory. The major difference between Type 165 and Type 911 is that Type 911 has a lock-out feature, but unfortunately (for your purposes) it's designed to be a high-limit lock out, not a low-limit lock out. You could achieve the same effect by placing a differential controller between the PVT and GHX fluid temperature, placing a cooling mode aquastat on the temperature you want to monitor that should stay above zero, and multiplying the two signals in an equation block, so the resulting signal to the pump is only 1 if *both* differential and aquastat signals are 1:
PumpOn = Aquastat_is_On*Differential_is_On
For the second part, it sounds like you'll want to combine one or more aquastat controls on the tank outlet temperature with one or more diverting valves that direct flow to different portions of your system based on the signal(s) from the aquastat(s). The standard diverting valve (Type 11f in the standard Hydronics library) has a control signal input that directs flow to one outlet when its signal is 1, and to the other outlet when its signal is 0. There is also a multi-port diverting valve in the TESS Hydronics library (Type 647) that can allow up to 100 outlet ports.
