RE: [EnergyPlus_Support] Re: Design Day V.S. Schedule

Cannot comment without knowing what is included in your hand calculation, and whether you were using DesignDay sizing or weather file run. What is the listed solar direct normal value and Global diffused horizontal value used. What solar altutude angle did you use?

The location and roof tilt do not cover all the necessary conditions. You need to calculate the angle between the skilight normal and the solar beam at the time of calculation.

The maximum solar radiation intensity must not exceed 1400 watt/meter square. It is only around 1000 watt/meter square measured in Kuching, East Malaysia.

Because you are using IP units, it is not easy to compare the result with the weather file input conditions.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: zqianmin@xxxxxxxxx
Date: Wed, 13 Jul 2011 14:41:00 -0700
Subject: Re: [EnergyPlus_Support] Re: Design Day V.S. Schedule

I have a skylight in my modeling, the simulation result shows this skylight has following maximum value

window transmitted solar of 1142.11Btu/h,

window transmitted beam solar of 858Btu/h

window transmitted diffuse solar of 284btu/h

window heat gain of 1382.65btu/h

this skylight window has a

u-factor of 0.35,

SHGC of 0.55,

Visible transmittance of 0.71,

23ft^2,

latitude of 38.7

longitude of -121.6 (Sacramental CA)

tilt angle is 18.97degree

hand calculating with radiant time series method give me following results:

window transmitted heat gains of 3360btu/h, which two times bigger than energyplus result.

I looked at the engineering reference, but still don't know why the value from energyplus are so small, about one third of hand calculating results.

Any one could give me some help? Thanks a lot.

Qianmin

On Wed, Jul 13, 2011 at 5:19 AM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:

With DesignDay sizing, the beam intensity can be controlled by changing the skyclearance number. (0.0 to 1.1)

The diffused components will adjust itself according the rules in the manual, when the incoming beam value is changed.

However, you should know that the set values are for the whole day. The temperature profile and the RH values may be set using schedules.

You can make it rain for the whole day, and not by the hours. When it rain, the sky temperature becomes close to the outdoor air temperture for the whole day.
=====================
If a building is comfortable for the worst condition, it should be good for the other time as well. I do use the weather file to verity the conditions in the Summer and Winter transition periods.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jeannieboef@xxxxxxxxx
Date: Wed, 13 Jul 2011 06:32:08 +0000
Subject: [EnergyPlus_Support] Re: Design Day V.S. Schedule

When specifying the Design Day, I specify quite a few variables that will "override" the normal weather file variables for specified date e.g. wind velocity is set to a constant. What I don't see are options for radiation (4 kinds). Does e+ pull any hourly variables from the weather file for set date, that are not specified in the Design Day object?

I have thus far assumed this to be the case.

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
>
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> Hi, QiangMin Table is useful to get an overall view of the result. Meters, etc. are useful only for those who are interested in preparing 'Green' reports. Solar loading on the building is a daily cyclic property. It cannot be separated into hourly value from the daily, monthly averaged values.
>
> This is why I am not very interested in the reports and annual simulation, when trying to design a comfortable building with natural ventilation. By the way, there will not be any monthly results in the table, if you do not do an annual simulation.========================= I high lighted some fields in the DesignDay object in the other mail. For your building, because the roof overhang is shielding the windows, you may not get any solar beam to beam through windows except in the morning and afternoon periods, when the sun altitude angle is low. If you plot this variable, you will see two peaks during one day, on the windows facing South. The North facing windows will see these during the Summer. I used March 21, June 21, September 21, December 21 in the four DesignDay object for the four seasons. If you want to have special schedules, you can use CustomDay1, SUmmerDesignDay, CustomDay2, WinterDesignDay for them. The maximum temperature occured on July 21 2 pm, because it is an diffused heat transfer effect from the ground and cloud to the environment outdoor air. This is a statistical value. The OA temperature etc. can be selected from the stat file, or the epw weather file for the location. These controls the convection heat balance on the exterior surfaces. Do not forget to turn on the skyclearance to unity in Winter. This controls the solar beam into the windows and change the MRT in the room. Blinds inside the window will reduce the solar heating, but not as afficient as the external one. Interior window temperature may not be the window glass temperature. The rate tells you how strong is the sun, the energy gives you the total heat transmitted. You can sum this on the spread sheet to get the monthly solar beam heating component. In building design, the annual value is not very useful. When you rotate the building, the window area and orientation are the controlling factor. In order to reduce the two peaks, you add vertical fins on two sides of the windows. Changing the glass position would also help. (recessed and bay window.) With natural ventilation, an open window can work like a fin and reduces the beam into the room.=================All surface temperature are reported. You can find these in the .rdd file. Use timestep to list and plot them. You can reduce the number of variables displayed using the .rvi file to selected from the .eso file, provided the variables are requested in the IDF. The advancedOutput directory under the exampleFiles directory has an exercise to show you the use of .rvi to get hourly, daily, monthly listing.=========================The heating and cooling load is calculated by summing all the zone surfaces and obtain a heat balanced condition. The internal heat is added, and then get a mean temperature. If this temperature is higher than the set point, a volume of air is exchanged with the cooled air, until the set point is met. Then the air change will still go on, if the fan is on, but the temperature of the cooled air would be different, because the coo > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: zqianmin@...
> Date: Tue, 12 Jul 2011 16:51:40 -0700
> Subject: Re: [EnergyPlus_Support] Design Day V.S. Schedule
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> Thank you so much for your help!
> I have a question about the report output. I want to take a look at the solar heat gain through all the fenestration, and heat gain through walls in different orientations to understand how energyplus calculate the cooling load. But I couldn't find these in my summary report. I selected all summary and monthly in output:Table: summary reports.
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> Regards,Qianmin
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> On Tue, Jul 12, 2011 at 1:52 PM, YuanLu Li <yli006@...> wrote:
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> Hi, QiangMin
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> ==================SizingPeriod:DesignDay,
> SACRAMENTO Ann Clg .4% Condns DB=>MWB, !- Name
> 38.4, !- Maximum Dry-Bulb Temperature {C}
> 18.6, !- Daily Dry-Bulb Temperature Range {deltaC}
>
> 20.6, !- Humidity Indicating Conditions at Maximum Dry-Bulb
> 101229., !- Barometric Pressure {Pa}
> 2.4, !- Wind Speed {m/s}
> 260, !- Wind Direction {deg}
>
> 1.00, !- Sky Clearness
> 0, !- Rain Indicator
> 0, !- Snow Indicator
> 21, !- Day of Month
>
> 7, !- Month
> SummerDesignDay, !- Day Type
> 0, !- Daylight Saving Time Indicator
>
> WetBulb; !- Humidity Indicating Type
>
> There are more fields below this line in the later version of EPlus.
> For temperature profile, comfort typw, RH, etc.
>
>
> ======================SummerDesignDay and WinterDesignDay are the name of the schedules which you would like to use with the Sizing object. (day types 9 and 10) Because the weekdays, etc. are related to the real situations, EPlus provided four extra conditions for you to do the simulation. In your schdules, if you wanted to use a week day to do the simulation, simply replace SummerDesignDay with, say, Monday.
> The Day of Month and Month specify the solar angle or earth tilt angle. The Daylight saving time adjust the local time, as the solar noon and local time noon is changed by one hour. You may change these to other days and define special schedules and call them CustomDay1 and CustomDay2 (daytypes 11 and 12).
> You can use as many DesignDay object as you want. However, you may need to use unique names. The data fields can be identical. When you use the annual simulation or short runPeriod simulation, the actual weather file conditions are used.
> When you use the Designday sizing simulation, the 24 hour period is repeated until the midnight conditions are the same. When you use the weather file simulation, the conditions of the previous day is carried forward to the next day at midnight.
> Sizing is controlled by what you think the system should be and is fixed. You have used sizing multiplier of 1.2, which means you want the system to be larger. You can also make it smaller and veriy with the PLR listing for the whole year.
> The schedule can be changed according to occupancy and can have many different conditions for the whole year. Therefore you have National, Xmas, Easter holidays, etc.By default,I think Saturday is in the Holidays group. You can list all the schedules to verify as in my attached IDF. I have removed all your unused material and constructions.
> School holidays can be scheduled as a period with allDays with holiday values.==========================
> RunPeriod,
> Annual, !- Name
> 1, !- Begin Month
>
> 1, !- Begin Day of Month
> 12, !- End Month
> 31, !- End Day of Month
> UseWeatherFile, !- Day of Week for Start Day
>
> Yes, !- Use Weather File Holidays and Special Days
> Yes, !- Use Weather File Daylight Saving Period
> No, !- Apply Weekend Holiday Rule
> Yes, !- Use Weather File Rain Indicators
>
> Yes, !- Use Weather File Snow Indicators
> 1.0000; !- Number of Times Runperiod to be Repeated
> =======================
> If you use short period for simulation, the first day result may not be accurate, therefore, the repeat field is provided for you to run the simulation a few time and use the second or third group results.
> You can shift the week days along by specifying a different day, say Monday, as day of week for start day of the weather file.
> Dr. Li
>
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
>
> From: zqianmin@...
> Date: Tue, 12 Jul 2011 13:01:50 -0700
> Subject: [EnergyPlus_Support] Design Day V.S. Schedule
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> Hello, I have a question about sizing:design day.The project I'm working on is a primary school, the occupancy, lighting, and other schedule is different in summer time. There is no people at school during June and July.
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> But my design day from weather data is July 21st. If I run and do the load calculation, it will be calculated on the design day, which means no occupancy and less lighting. Is there any way that I can size my unit on design day with full internal load in summer time and less internal load for winter design day?
>
> I don't want to change my occupancy and other schedules to increase the energy consumption.Thanks for your help!
> Qianmin
>

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