Re: [TRNSYS-users] Solar Steam (steam drum) + type 22 iterative controller

[Jeff Thornton <thornton@tess-inc.com>]

Jose,

Your timing couldn’t be better.  We just finished (literally yesterday), a steam accumulator model that is intended to do exactly as you suggest; store steam in a pressurized vessel for periods of low steam production and higher load.  If you search for STEAM ACCUMULATOR online you’ll be able to see how they work.  The key is you have to store steam at a higher pressure than the load pressure to be able to use the stored steam.  This model will be part of the new TESS Libraries v18 package but can be made available as a stand alone component now if needed.  Let me know and I can get you a quote.

As for Type 22, I’ll start with my usual questions when people ask about controls:

1) Are you using a small timestep?
2) Do you have capacitance in your solar loop (pipes etc) to dampen the oscillations?

If you do then I’d like to know which collector model you are using?  Many of the TESS ones have an option for internal controls where you can set the desired outlet temperature.

Jeff - TESS LLC

Sent from my iPhone

> On Sep 14, 2019, at 8:31 AM, José María Roca via TRNSYS-users <trnsys-users@lists.onebuilding.org> wrote:
> 
> Hello community, 
> 
> I’m trying to model solar steam generation and I was wondering if there is some kind of storage that could hold steam and saturated water, that could act as buffer in case the radiation falls for a small gap of time (1h, 2h, etc).
> 
> I’m using to generate steam the type 637a HRSG using as hot source pressurized water from the solar field. I looked into the flash tank but it doesn’t have volume parameters, so this can’t hold steam and it works pretty much as the 637. Am I right?
> 
> On the other hand regarding the second part of the question, I’m using the type22 to modulate the speed of the pump in the solar field, to try and keep an outlet temperature at a certain value. The problem I’m having is that this controller in some (many) occasions goes into “stuck at previous value”, controller status value 17. This in turn makes the colector output temperature go to the maximum value and no flow goes through the solar field, until some time steps in the future it starts working again. I can’t figure out why this happens, the only thing I can think is that as the direct radiation falls in those time periods perhaps de controller can’t resolve a pump flow to keep the temp at the setpoint, but this makes the temperture to raise to maximum, seems odd. 
> 
> Thanks for reading and for any comments.
> 
> Best,
> José M. Roca
> 
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