DancingDavidE's profile - activity

The pumps may be defined as variable speed, but double check that there is some driver from the system that causes them to vary by tracking a variable to show the actual flow rate during the simulation.

A simplified way to describe the sizing - verify from the output reports that the total chiller capacity matches the load reported by the AHUs/coils. Make a manual adjustment if necessary so that you have two chillers that are each sized at one-half the needed coil load.

The sequence for the chillers may have constant speed condenser water pumps, providing the same amount of condenser water flow any time that the chiller is operating. (Use of constant speed condenser water pumps is common in practice.)

In your case with two chillers, you are actually reducing the flow rate and required energy by half when only one chiller is operating (which may be most of the time) as opposed to two chillers.

Similarly on the chilled water side, if you have primary pumps that are constant speed the same effect will take place. The magnitude should be less than for the condenser water pumps. Secondary pumps should be more or less the same in both cases if the buildings are identical.

Lastly, if the single chiller is oversized, then there could be minimum flow rate requirements that are hit resulting in excess energy use. The case with two smaller machines may not be hitting any limit.

I recommend to review the building load requirements and verify that the 1.0 and the 2 x 0.5 capacities are suitable. The savings by moving to two chillers at 1/2 the load should be less than what you observed if the chillers are sized to equal the load. Your results are understandable if the load can actually be satisfied by one chiller at 0.5 factor.

Verify the capacities of chillers and pumps, don't rely only on the sizing factor to determine the capacities.

I hope this helps!

David

In the meantime, I'd say go ahead and leave your comment...either the person will see the comment and add it themselves, or someone else with 200+ might do it if they agree.

Compare your end-use breakdown per area vs AEDG or other similar reference point. Maybe the fans are normal, and the other end-uses are too low?

Or more likely, confirm with that your other end-uses are in the proper range so that you know your are troubleshooting the correct equipment.

If the published costs are "reasonable" then this sounds like the easiest path to use them directly. However, I know of some district energy systems that include a pretty high cost for capital recovery among the other cost components. This will provide a higher emphasis on the heating and/or cooling efficiencies relative to other certified projects.

Philosophically, a chilled water energy cost of $0.40/ton-hour could more than four times the energy-only cost that you would pay in a university setting using the default plant efficiencies.

In particular for Solar PV the industry is advancing so quickly that a set of default values made at some unknown time in the past may not be accurate for a modern PV system.

If it is possible to substitute your own performance from a current product that might be the preferred path.

Can you clarify what your role is on the project? Are you asking what information can be provided without a building energy model? These calculations still may take some time, if not quite as much as a BEM.

To answer your question, it largely depends on several factors that would reduce your opportunity for energy use reduction:

1) You have a constant or nearly constant need for the same quantity OA.

2) Your need for OA quantity changes, but there aren't controls in place (in the design AND in your model) that allow the quantity of OA to be reduced at times.

3) The OA quantity is small and the resulting DOAS fan motor horsepower is small. Although the total magnitude of savings may be little, a VFD may still provide an ROI in this case.

4) You have many economizer hours where it is beneficial to take a larger quantity of outside air, even though the OA requirement is less.

@Julien Marrec - there still could be a small energy benefit if the VFD could be used for airflow balancing, or to adjust pressure to maintain constant airflow over time while filters loaded and then were replaced. Large motors that start and stop frequently may also benefit from use of a VFD at startup as an operational (non-energy) measure.

If you mouse over "Karma" next to your username it will list all of the rights that you have currently, just so that you can confirm your current level of authorization.

Also be sure that you entered the "captcha" text correctly at the bottom, or use the audio alternative if it is difficult to make out the text on your screen.

I had this in draft all afternoon, and now I like the prior answers that came before. But just in case those don't solve it...

The real-world scenario (obviously breaking down before reaching 200C!) is that the system can't reject enough heat that is being added to your system.

1) Can you also trend flow rate in addition to the tower's temperature?

2) What internal loads did you assume for the spaces? Could there be an error that is way overloading the space with heat gain'? You said the building ran with a VAV system though and the results were reasonable, so this probably isn't the fix.

3) Check your equipment capacities to be reasonable for this size building - cfm/sf, square feet per ton (add up all the heat pumps), square feet per ton of cooling tower, etc. Do these match up with the VAV system case?

4) The system seems to take a drastic turn for the worse at the beginning of February, are there any changes in occupancy schedules or equipment availability around that time?

5) Does the system have a boiler? If so, maybe get rid of the glycol.

ASHRAE 90.1-2007 or 2010?

Did you mean five zones per floor?

I have seen new construction incentive programs that reward based on incremental 0.1 W/ft2 improvements over the 90.1 (or IECC) values.

I think it will be difficult to find too many general references for "state of the art" that provide a fixed LPD value, since the selection of an advanced technology may be specific to the space type, owner, etc.

Your best bet may be to look for a similar case study in High Performance Buildings Magazine, or other repository of case studies for specific buildings.

I think the big changes affecting the energy modelers are coming with 90.1-2013.

Here's a link with all of the changes... https://www.energycodes.gov/training-courses/ansiashraeies-standard-901-2013

Here's the direct link to the Appendix G presentation... https://www.energycodes.gov/sites/default/files/becu/90.1-2013PerformanceBECU.ppt

Check out the page about window-to-wall ratios! And computer rooms!

For comparison of two files, if you weren't already using Notepad++ for editing, I like "Compare-It!" - you can add a list of keywords to highlight, and it will identify different types of modeling input file extensions if you add a description.

http://www.grigsoft.com/wincmp3.htm

Actually I need to check out the latest version, there may be new features since I last checked.

Edit: I tried a couple scenarios and it worked, I believe it may be back online.

There may not be a lot of EE4 users on the forum yet. Can you clarify what the constraints are in EE4?

In other programs it might be possible to create an occupied zone and an unoccupied zone that allows temperature stratification to take place, where otherwise the program assumes a "well mixed zone" as we say. Then, some portion of the heat gain from occupants or equipment might be assumed to be going directly to the unoccupied zone.

Another common issue in the simulation is that you need to account for an accurate air supply and return pressure drop. Also the supply air temperature may be warmer than other conventional VAV systems allowing efficiencies back at the cooling equipment.

If this will be an underfloor system, one of the construction issues is the air-tightness of the plenum and ability to deliver to all portions of the floorplate, and from occupants obstructing their vents...this is difficult to account for.

Hopefully this helps you find a workaround. If not, let us know what the specific constraints are in EE4 and maybe someone will have an idea for you.

"Templatized" HVAC systems save time on those projects that have HVAC systems that are a match for the templates.

Easy reporting of variables for investigation, calibration.

Easy to setup project geometry and zoning.

CSV output available by hacking the eQUEST.ini file.

DOE2 report types and format are well known to others, facilitates review of the model by others (or my review of them).

Wizard mode provides a method for someone who is knowledgeable about building science to learn modeling.

Large peer group of consultants...who tend to run into many of the same issues.

Parametric simulations.

3D rendering, other GUI innovations (that are now common among other simulation programs).

The price!

Going to downvote until we hear a little bit more about the request...which program is key in terms of describing what the actual procedure is to add one. Also what is the goal for having this included? Some programs can't model an interior window like this for light transmittance, but if the question was about conduction then there might be a workaround that approximates the effect. So depending on the program we might decide how to add one, but may not accomplish the modeling goal anyway.

A few things to get you started:

1) EUI, kWh/sf, W/sf, therms/sf, $/sf -- all of these should be benchmarked as if the building was currently in operation, do the values make sense?

--- also the consumption values may change seasonally, do the patterns make sense? --- cfm/ft2 match expected values for auto-sized systems.

2) Does major HVAC equipment operate throughout it's capacity? (i.e. reconcile designed capacities with modeled loads)

--- check auto-sized capacities against ASHRAE rules of thumb if not using designed capacities. --- if you have designed values or actual values, verify against those capacities for major HVAC equipment

3) If the modeling package includes a rendering feature, does it match the architect's drawings for new buildings or photos of the actual site for existing buildings.

4) See previous thread on this site about calibration methods for existing buildings...this is an area with a wealth of resources.

5) For new buildings, do the results track with the project's goals? If not that will need to be resolved either by changes to the model or revising the goals.

6) Energy end-use breakdown should be compared to other projects, variances explained.

7) Calculate average annual efficiencies for primary equipment, are they reasonable?

8) Unmet hours, and/or zone temperature reports used to show that conditions are met appropriately. Verify that air temperatures and water temperatures are reasonable.

9) Verify that correct weather file was used, any elevation adjustments are made if needed.

10) Verify modeled building area against the design or actual area. Don't count the plenums or dummy zones.

11) Assess any key assumptions that were made. Perform sensitivity analysis to determine what effect might result if the assumption was too high/low/etc.

Lots of other factors that might be specific to your model. Too many to list!

As far as someone else's model, I'd ask them some of these same questions.

Pretty much any whole-building modeling program will be able to handle this the same way. You can enter the power consumption of the oven.

You'll need to use some calculation outside of the program as to how many kW are used through out the day based on what is being cooked, and what the hours of operation will be. You'll also need to note how much heat from the oven is convected/radiated to the space and how much might be exhausted through a hood so that it isn't part of the cooling load.

Does one of these comments answer the question? Currently when I sort the forum by "unanswered" this one keeps taking the top spot.

And what does a popular brand of khaki pants have to do with EnergyPlus?

I'd like to offer a slightly shorter answer - apparently "yes"

This manufacturer will provide an exceptional calculation spreadsheet for you - http://www.kone.us/sustainability/leed/

Also pass this PDF along to your LEED consultant/architect, they may count the elevator in additional credits, and also not embarrass themselves by claiming credit where elevators are excluded.

http://cdn.kone.com/www.kone.us/Image...

@Kent Beason "geothermal" and/or "geo-exchange" and/or "ground-coupled heat exchanger" might be good tags as well, especially if your end goal is modeling a geo-exchange system more so than specifically using the AEDG model.

If you have found a particular issue, please let the group know. Sometimes these are traceable and correctable.

Weather files posted alongside modeling programs will have originated more or less from reputable sources although certainly there might be an error here or there due to faulty processing, missing data, or irregularity in the original source.

A couple of paid services are:

http://weather.whiteboxtechnologies.com/

http://www.weatheranalytics.com/get-w...

As far as Africa in particular, I can't say if these sources are better than others, or if the availability in general is going to be good. I can imagine that there might be difficulty with microclimate where the available sources are far apart if your modeled building is located somewhere between.

@yongqingzhao - if that's the "correct" answer, then click that checkmark to mark the question as closed.

This sounds like a question about using the wizard to zone a building with specific layout, instead of using the default shapes?

In case the question pertains to "how to calculate latent loads and equipment sizing" -- here is one page of resources that will help you determine the model inputs in generating the latent load.

http://www.desert-aire.com/index.php?...docman&task=catview&gid=128&Itemid=179

There are a lot of variables though pertaining to how active the pool occupants will be throughout the day, temperature of the pool, whether there is a cover, etc.

I think National Capital Chapter was mentioned in the "Where to Meet Energy Modelers" thread, but this topic could be appropriate there, maybe not with the full agenda but about the chapter more generally.

I'm "thinking out loud here" - so if someone can jump in that knows the specific answer, please post.

I don't expect that the prototype buildings necessarily had separate thermal zones for the UPS equipment in an office building's data center. I guess the common practice might vary somewhat throughout the time periods of the prototype buildings (only modeled explicitly after 2004 apparently!) as to which energy storage technology is used in office building data centers, and whether this room would have a separate ventilation system or would have the equipment located in the same room as the server racks.

The assumption for 45 W/ft2 of heat gain likely includes losses related to the UPS system to be picked up as heat, and I wouldn't expect the model to include any dedicated time for charging the UPS showing a spike in kW.

@Emir Pekdemir, if you are working on a specific building that had UPS batteries requiring separate ventilation, then I think you should modify the prototype model to include a separate zone if you are also itemizing the server floor power, cooling, and ventilation energy.

I guess we users can't mark the answer "correct"...consider this comment to be a small transfer of unmet-hour karma. The inputs (and what you are doing with the outputs) are key.

The answer to your question is that you can choose one of the single-zone systems with a type of DX cooling.

PTAC is probably the best match...take a look at that system description in the documentation and see if it matches up with what you have.

*I'll edit mine too then :)

Are the spikes of long enough duration and frequent enough that you won't be getting the correct answer from the modeling results at a holistic level?

It will depend on what you are trying to get out of the model -- if you are trying to optimize other parts of the building, maybe these spikes don't change the larger recommendation.

However if the analysis is specifically pertaining to the zone airflow and OA quantity, then I think you need to review the parameters as suggested by Mike Witte, and/or investigate the possibility of a bug.

Complex geometry can certainly be a big influence on the cost of creating a model. Similarly, if the zoning will be very precise this can result in a higher level of effort.

Another factor to consider if whether the modeling program allows for multipliers to be used for floors and systems that are similar to each other.

Look for ways that the model can remain accurate, but be simplified in terms of input to reduce the level of effort.

Much of your time might be spent after the model is producing results. Either the design may change, or many alternatives will be considered. As the earlier response noted it may be prudent to discuss the anticipated architectural updates and include a limitation on how many of these will be modeled.

If the model will be calibrated, allow time to compile the data that will be used for tuning the modeled controls.

ASHRAE Handbook of HVAC Systems and Equipment Chapter 4 describes some of the air-side systems with diagrams.

These are more than just the Appendix G mapped system types, and you'll have to look at other chapters for the description of the primary heating and cooling systems...overall a great resource if you aren't familiar with some of the potential variations in configuration for air distribution systems.

Chapter 4 will be a great read for you if you aren't familiar with some of the older system types that are common in existing buildings, more so than for Appendix G which is focused on a few modern system types.

Particularly for existing buildings there needs to be a qualitative examination. You'll be able to gauge the envelope's construction type -- is it made of materials that would tend to yield higher or lower infiltration rates? Are there many penetrations and joints? Are thermal images of the windows available when the HVAC system is on and when it is off?

Then also assess the construction or maintenance quality which may be a factor that you can observe...was the envelope well-sealed originally, and has it been maintained?

In some cases you may be able to acquire trend data or deploy data loggers to show how temperature changes when the HVAC system is off. In past experience this will mainly be useful as backup for your assumptions in cases where the infiltration rate is very high...in those instances the client probably has some idea that the building is leaky.

For most cases it will be difficult to confirm or deny the constants in the more detailed formulas, but by comparing the utility bills and maybe the space temperature trends you can partially calibrate.

This works in conjunction with knowing the other energy using systems in the building -- the more of those that are well-known, the less energy use that is eventually left over to vary as infiltration or process loads.

Lastly, run a sensitivity analysis to determine how important infiltration is to the results. (And your other major unknowns that were assumed to have a certain value.)

61.6 is pretty low for most types of labs! What were the parameters that were entered to define the building characteristics?

If you attend the ASHRAE conferences, we always have an IBPSA-USA dinner meeting on the Saturday afternoon and evening prior to the start of the ASHRAE technical program on Sunday morning.

Details are still being finalized, but the next meeting will be January 24th, 2015 in Chicago -- location TBD although I'm hoping we come to an agreement with the Berghoff.

There will be at least an hour of networking time at that meeting. This is one of the best opportunities to meet other energy modelers in person.

In addition to the networking, there will be industry updates, as well as a technical dinner presentation. Hope to see many of you there!

David

Here is a better laboratory specific data set. This would only apply towards buildings that are laboratories (although the percentage of lab space vs other space can be used to filter the results), not necessarily a medical laboratory inside of another facility.

http://labs21benchmarking.lbl.gov/

Here is some general information about hospitals and medical offices.

http://www.nrel.gov/docs/fy14osti/610...

It's not a comprehensive list of laboratory equipment, but may still be helpful.

I believe that there is actually a separate question pertaining to the auto-sizing for multiple chillers which has been buggy in the past, which is separate from the issue of why the values might vary between the two reports in a general sense.

This issue has frequently come up when auto-sizing multiple chillers unless this has been remedied in recent versions of the software. You'll need to go back and enter the capacity for each chiller and re-run the simulation once you've established the loads.

For your design case models, you should have the proposed capacity from the engineers, auto-sizing will only be in the early stages of the project where the capacity may not yet be determined and for the baseline case where there isn't a designed chiller.

As far as the variance between the two reports, verify what method you are using to size the plant equipment either the connected coil capacity or the modeled coil load (which often will be less), and if any oversizing is included.