[Equest-users] Outdoor swimming pool and heater

Fri Apr 22 15:05:55 PDT 2016

To “roll your own” savings for pool covers:

1.       First calculate heating loads sans pool cover measures.

a.       I do not do pools every day, but have also adapted the 2004 Shah method in lieu of ASHRAE Applications approach a few times now (discussed in the link shared previously by Elizabeth).  Note both models are intended for indoor pool applications, so “correctly” adapted/applied to exterior conditions you might get odd results – keep a sharp eye out! 

b.      An outdoor heated pool would be a slightly trickier problem to accurately calculate, as you are now dealing with variables from your weather file to include air velocity (hourly windspeed – you mentioned rooftop so this might require further processing considering elevation) and a broader range of air conditions (DB temperature + RH), from which you could derive hourly dewpoint <https://iridl.ldeo.columbia.edu/dochelp/QA/Basic/dewpoint.html>  à saturation pressure for those air conditions <http://www.srh.noaa.gov/images/epz/wxcalc/vaporPressure.pdf> ,  and then also  the saturation pressure at the  pool surface <http://www.engineeringtoolbox.com/water-vapor-saturation-pressure-air-d_689.html> .  You may also want to consider conductive losses to the environment/ground below the pool depending on the circumstances.  I haven’t done it, but it seems like there may be a workable path here (looking at the 2015 ASHRAE Applications equation #1, specifically).

c.       I recommend at minimum reading up on some of the already cited literature, but here’s an open-source/public tool building upon the Shah approach to if you need to get a fast approximation – be mindful again this is without further edits intended for indoor applications: http://www.energyideas.org/documents/spreadsheets/IndoorPoolCalc.xls

2.       Take a moment to look hard at the pool cover system(s) under consideration.  Decide for yourself by what factor that cover system, when deployed, will reduce evaporation/convection losses (a lot, typically), and radiation losses as well if an insulated variety (I’d estimate this leveraging the hourly weather data + pool temperature profile + cover R-value à UAdT).  

3.       Determine a likely profile for cover system deployment – consider whether the system is automated or human-deployed when evaluating your results… if you are ultimately into “guessing at human behavior” territory here, recognize you shouldn’t spend too much time worrying about the finer nuances for this estimation and should consider presenting your savings as more of a “range.”

4.       With that information at-hand, calculate hourly heating reductions from your “sans cover” calculations.

5.       To spoon feed back into eQuest:  

a.       Take your before/after hourly heating loads columns, 

b.      Normalize each to a maximum hourly load (loop process load input for eQuest), 

c.       Punch them into EMIT to generate annual normalized load profile INP files you can import, 

d.      Assign those schedules & maximum hourly load to the appropriate eQuest heating loop

Note if this is already a large model, be mindful EMIT’s 8760 hour fractional schedules can be quite heavy to deal with in multiples – use that tool judiciously and simplify to averaged daily/weekly/monthly load profiles if it doesn’t make a huge difference ;).

~Nick

------------------------------------------------------------------------------------------------------------------------------

Nick Caton, P.E.

  Senior Energy Engineer
  Energy and Sustainability Services
  North America Operations
  Schneider Electric

D  913.564.6361 
M  785.410.3317 
E  nicholas.caton at schneider-electric.com <mailto:nicholas.caton at schneider-electric.com> 
F  913.564.6380

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Rehana Jiffrey
Sent: Thursday, March 31, 2016 6:58 AM
To: Jayant Patil
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Outdoor swimming pool and heater

Thanks all. Ideas were helpful. 

Now trying to figure out how much energy energy can be saved if a pool cover is installed. It is possible to model this in equest?.

Rehana.

On Mon, Mar 28, 2016 at 8:18 PM, Jayant Patil <jppatil at gmail.com> wrote:

I use the methodology described in the below link. It is pretty much close to the ASHARE  method and EPA's energy star performance rating technical document.

http://www.rlmartin.com/rspec/whatis/studies_outdoor_inactive.htm

Jay

On Mon, Mar 28, 2016 at 9:14 AM, Elizabeth Gillmor <elizabeth at energetics-eng.com> wrote:

I use bin calcs for this, though I am interested to hear if others have a better way.  Total load = losses from evaporation + radiation + convection.  Use 8760 data from your weather file to get OA DB, humidity, solar radiation, wind speed etc.  Useful paper with equations here:

http://www.mmshah.org/publications/ASHRAE%202014%20Evaporation%20paper.pdf

From my bin calcs I get a total annual load in Mbtu/year, then convert that to Mbtu/hr for the days that the pool is open (which averages the load across its operating period), and model that as a process load on a boiler loop with an on/off schedule ("on" during the open season).  It's a relatively OK estimate for a fuel rate that doesn't have a demand charge, but might not be the best way for your electric pool heater if you have a demand charge on your rate.

Elizabeth Gillmor  PE, BEMP, LC, LEED AP

e n e r g e t i c s  consulting engineers, llc

energetics-eng.com | 303.619.0091

On Mon, Mar 28, 2016 at 9:42 AM, Christian Kaltreider <ckaltreider at sudassociates.com> wrote:

	Rehana,

	Estimating the energy consumption of a pool heater can be very tricky.  The dominant mode of heat loss is generally evaporation.  Some major influences include activity level of people using the pool (splashing/stirring increases evaporation), wind speeds, and the use of a pool cover.  The US DOE has some material on the subject:  http://energy.gov/energysaver/gas-swimming-pool-heaters  There is a table on this page which I have used to back calculate and extrapolate heating requirements for a specific project as a sanity check.  

	Also, ASHRAE HVAC Applications 2015 addresses pool heat loss starting on page 5.6.  The discussion is helpful and provides sound calculation methods, but they are more easily applied to indoor pools than outdoor pools.

	That’s all I have at the moment; hopefully you can find some additional resources.  

	Good luck,

	Christian

	From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Sunayana Jain
	Sent: Monday, March 28, 2016 8:23 AM
	To: Rehana Jiffrey; equest-users at lists.onebuilding.org
	Subject: Re: [Equest-users] Outdoor swimming pool and heater

	Rehana,

	You can model pool heater load on electric meter (see image below) with winter months schedule:

	Thanks,

	Sunayana Jain CEM, LEED AP BD+C

	From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Rehana Jiffrey
	Sent: Saturday, March 26, 2016 11:21 AM
	To: equest-users at lists.onebuilding.org
	Subject: [Equest-users] Outdoor swimming pool and heater

	Dear All,

	I'm trying to model an outdoor swimming pool located at the roof top of a residential building. Pool heater (45Kw) operates from December to March (4 months). 

	I was wondering if anyone could help me how to model this scenario, and where to input these consumption values. 

	FYI, this is my first time modeling an outdoor pool and pool heater.

	Thank you,

	Rehana.

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