[Bldg-sim] Modeling different Energy Recovery Scenarios

[Keith Swartz]

Adam,

We have also used spreadsheet calculations on the side for dual wheel energy recovery systems with coils between the wheels. Neither eQUEST nor Trane TRACE will model this type of system. When the coils have chilled water or hot water that we want to have TRACE (or eQUEST) include in the chilled water and hot water plants, we have the spreadsheet calculate the hourly cooling and heating coil loads, which can then be input into TRACE (or eQUEST) as  hourly load profiles assigned to the respective plants.

Semco also has a spreadsheet calculator for the Pinnacle and other products on their website. It’s kind of hidden…

Go to www.semcoinc.com<http://www.semcoinc.com>.
On the far left side select “Energy Recovery Products.”
On the far left side select “Pinnacle” (or whichever product you want)
Scroll down to the box at the bottom labeled “Product Library.”
In the “Select a category” field in the upper right corner of the box select “Selection Software.”
Click on the spreadsheet icon and save the spreadsheet wherever you want.

There are a few quirky things to be aware of…

The natural gas utility cost is in units of $ per million BTU, which is 10 times $ per therm.

The cooling source kW/ton is for the entire system, including any pumps and cooling towers.

Electric consumption (kWh) is not calculated directly, but you can get it indirectly by setting the utility cost as $1 per kWh and $0 for everything else. Then the dollar amount shown matches the kWh. The gas consumption can be calculated indirectly in a similar way by entering $1 per million BTU (or $1000 to get more significant figures) and $0 for everything else. The same trick does not work for kW. I don’t remember why.

In the past we have experienced a problem with the Pinnacle spreadsheet not showing any change when the external static pressure is changed, so we did fan power calculations on the side. A quick check with the latest spreadsheet shows a change. Perhaps my original change from long ago was not significant enough to increase the cost by $1. (Some of my clients have very cheap electricity, which makes implementing efficiency tough sometimes!)
________________________________
Keith Swartz, P.E., LEED AP

Energy Engineer / Senior Project Manager
Energy Center of Wisconsin
455 Science Drive, Suite 200, Madison, WI 53711
Phone: 608.238.8276 x123
Fax: 608.238.0523

The Buildings Team
Design decisions through energy, economics and emissions analysis.
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From: hamnmegs at ozemail.com.au<mailto:hamnmegs at ozemail.com.au> [mailto:hamnmegs at ozemail.com.au]<mailto:[mailto:hamnmegs at ozemail.com.au]>
Sent: Monday, January 03, 2011 3:31 PM
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>; 'Adam Niederloh'
Subject: Re: [Bldg-sim] Modeling different Energy Recovery Scenarios

We have modelled similar systems by using traditional simulation to get the off-coil and on-coil conditions.  We dump these to an hourly spreadsheet and model the psychrometrics there.  We use the ASHRAE toolkit if wel feel necessary to model wet coils robustly etc.  Many simulation programs assume a constant bypass (or contact) factor when in fact this is dynamic.  I believe this is significnt to take into account with the types of systems decribed in humid climates.  I haven't seen a simulation programe that can model your systems correctly but then I have only been exposed to EQuest (DOE-2.2), IES VE, TAS, HAP.  I suspect TRNSYS may allow you to model it, but if you aren't already using it would you not be better off spending the time on a robust spreadsheet template ... good luck.
Regards,
Graham

On Tue Jan 4 5:24 , "Adam Niederloh" sent:
All,

Happy New Year!

I know that I recently asked the question shown below; however I did not receive any replies so I thought I would try again seeing as how it’s a brand new year.  The question as previously asked:


I am curious to know what programs/methodologies people have used to effectively model the following types of energy recovery systems:

1.)   Dual Wheel Heat Recovery with a Cooling Coil between the wheels.  This system is similar to the SEMCO Pinnacle system. As the outdoor air travels through the air handler it passes first through a total energy wheel, then through a cooling coil and then through a passive dehumidification wheel.  The exhaust air, as it leaves the building, travels through the passive dehumidification wheel and then the total energy wheel.

2.)     Twice through Heat Recovery with a Cooling Coil in between the first and second pass.  This system is similar to a DesertAire system. The outside air passes through the heat recovery device, through a cooling coil, and then through the other side of the same heat recovery device thus pre-cooling the outdoor air and reheating the supply air.

Please see the attached PDF for very simple schematic sketches of each option.

Thanks,

Adam

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