Energy Savings Calculation by replacing Ammonia chiller with Desiccant Dehumidification 1

[Kazinscky]

Hello engineers,
I am currently working on a project for a client, and I am trying to find resources that will help me calculate potential savings that come as a result of replacing
Ammonia chiller with desiccant dehumidification for moisture removal in a food manufacturing facility. Any tips or software referal will be appreciated.

My thought is to compare energy usage for the two systems and find the difference.

Thanks

 

[nuuvox000]

The spec sheets should tell you the efficiencies of each. Look for IPLV/NPLV or something similar.

 

[BronYrAur]

easier said than done. The dessiccant will require a heat source and a cooling source. The ammonia system will probably still be in use for refrigeration, correct? So it will be difficult to determine the savings. Both of course require power. Tricky calculation, but I would assume that the desiccant manufacturers have a way to do it as a selling point.

 

[SAK9]

If it is dehumidification of compressed air it is a straight forward calculation.If it is dehumidification of an air-conditioned space you will struggle to split the energy requirement between dehumidification and cooling processes when you analyse the energy consumption of chiller.

 

[Kazinscky]

Thank you for all your inputs. The idea is dehumidify conditioned space. Trying to minimize load caused by moisture content in facility.

I knew it was going to be a challenging task but was wondering if there’s similar work or literature to reference. The challenge is to split energy requirements for the two processes. Any safe assumptions?

 

[HVAC-Novice]

You need to perform some energy simulation. I don't know if Trace 3D has all the HVAC capabilities or IES. but one of the simpler energy software won't be able to do it.

This isn't something where you just look at 2 nameplate numbers. It depends on the air properties over every hour of the year, you climate, efficiencies of the specific equipment under all load conditions, heatsource etc.

the desiccant manufacturer likely has a simplified Excel file or so. but obviously they also are in the business to favor their product.

 

[SAK9]

Assuming your production space is not filled with lot of people in these days of automation, the biggest contribution to moisture load is likely to be from the fresh ventilation air. Divide the total cooling capacity of the chilled water plant by its maximum energy consumption and that will lead you to average cost of cooling per kw(to be precise plant efficiency will vary while operating under part load conditions) Calculate the cooling Kw required for dehumidifying the ventilation air using a DOAS AHU and its annual operational cost based on varying outside air conditions and plant operational hours. An energy simulation calculation software like IES or Carrier HAP will be required to do this calculation. You will now need to do the same calculation for the desiccant wheel as well to do a comparison. If the desiccant vendor is keen he may help you with that part of the calculation but take it with a pinch of salt

 

[Kazinscky]

@ SAK9 Thank you so much! I set up my spreadsheet close to what you just described. Finding calculation tools you pointed out was the hard part. I think this might work or at least give me an idea.

 

[MedicineEng]

As said above, don't forget of the external heating and cooling source that you need to regenerate the desiccant.
A few years ago, we were looking on dessicant dehumidication and it looked quite interesting until we factored in the heat necessary to regenerate the dessicant which was the (big) straw that broke the camel's back.
If you have low grade waste heat that can be repurposed for dessicant regeneration, then it would a plus on the desiccant solution side.

 

[HVAC-Novice]

I don't think a spreadsheet can do this. You'll need a more sophisticated software. You need to include varying equipment efficiencies based on air conditions, % load, staging etc. you also run fans (and maybe pumps) at varying speeds and efficiencies.

There is a reason dedicated software exists.