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

[Dr D.A.G. Redpath]

On 2019-09-14 15:52, Jeff Thornton via TRNSYS-users wrote:
> 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 at 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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Hi Jeff,

Would it be possible to obtain this model for version 17 of TRNSYS? I've 
been working on a steam accumulatoras well but in the process of 
building the component myself. Thanks
-- 
Best Regards,

David Redpath

Research Associate,
Generation Integrated Energy Storage,
Cambridge University Engineering Department,
Trumpington Street,
Cambridge,
CB2 1PZ,
UK