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[EnergyPlus_Support] Re: Baseboard heater water inlet temperature higher than central boiler outlet
Dr Li,
I must say that I didn't understand last paragraph completely.
Since you have experience with coupling measurements to E+, I will feel free to ask for your opinion on several topics (if you could help on them).
1. From the literature survey I had done considering calibration of BEM (building energy model) I understood that the idea is to check hourly measurements from the utilities (in my case Gas and Electricity supplier) with E+ outputs on the same resolution. In most papers buildings were equipped with air based HVAC systems and the calibration was done mainly with electricity, and in some cases with "fossil fuels". Compared to these buildings my building is fairly simple, both in area and in HVAC complexity (I have only hydronic heating with radiators and local air heaters), but this building of mine is of industrial type. I have several production machines which all consume electricity. Unfortunately, I haven't yet installed equipment to measure this consumption but I intend to. Besides machines electricity is used only for interior lighting and plug load. This plug load I have measured on most of devices (energy logger) in order to create their schedules and energy consumption. Lighting system will be "measured" through surveys for each zone since I know installed power and coefficients needed in E+. Depending on the equipment I am going to find maybe some electricity stress tests will be carried out. Machine energy consumption can be translated to type of equipment is being produced and then based on technological calculation to establish daily or weekly profiles.
2. Considering gas consumption, in my case is very simple to check since I have gas meter on the facility level (only one consumer-gas boiler) and ultrasonic heat meter - so in real time I can determine the boiler efficiency (supply side) by dividing these two.
3. Temperature measurements in hydronic system supply side will be part of the building control system, and a good way to check whether modeled control is good (I will assume this temperature enters all heating bodies). Also, on the return side temperatures will be measured since radiators are equipped with thermostatic valves (since return temperature will be different).
4. Indoor air temperature measurements will be carried out in order to check the model and maybe in zones with higher heat dissipation from machines to include in control loop in order to reduce heat delivery to these zones.
5. weather measurements will be carried out as I described earlier in the post
Finally, the idea is to calibrate the building model as-is and then to do some improvements (currently I do not know which, probably in the HVAC control since the building owner is the producer of HVAC control equipment, and the building is newly built).
At the end If you could send me some of your references and the PhD which you mentioned, I would be very greatfull.
Marko
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
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> Hi, Marko One of my former students started his reserch on a similar pattern as you haave described, in 2006. He has now being awarded the PhD degree. The problem with loading the .epw file with current loacal data is that not all the fields are available from the meteorological station. At that time there were three locatins were used.1) the MET statin at the airport, 2) the data from the mini-weather station on the Univerity campus, 3) OD temperature measured outside the building. About five fields of .epw were changed. The distance between 1) and 2) is about 5 km. There were noticeable differences. The buildng under investigation is a row of single storey conference rooms, surrouonded by some trees. The entrance to the room has a 4m roof over hang. When the outdoor temperature were measured, the four direction did not gave the same readings, although the difference was only 0.5 to 1 degreeC. This means that the temperature measured in the room would be different from the three simulations using the three sets of data. EPlus uses one value for a wall surface. The measured temperature on a surface is not constant. So which value should be used for comparison. Using a 30 channel data recorder for thermal juction probes, five probes each were on the out side and inside surface of a wall, and the others for ceiling, floor, outdoor, attic, and the room at different height. It was hard work. Mounting, construction of the shield, and backing of the probe are all important to get the desired result. My conclusion was that using the locally measured value near the building in the .epw would make the match better. However, for enrgy saving and building design the TMY is good enough. His thesis covered a lot more other related topics. The measurements on the equipment side are straight forwar, as they are all single value points. COP, efficientcy curves are all part of the equpment characteristic determined by the manufacturer. EPlus simply used them to get the cost values. The simulation program simply uses the demand as the input to get the operating point to do the cost conversion and produces a report. When you try to match the gas bill with the simulated cost, you would need the actual local weather data. Then, why do you need to match the two?. Because you are not sure that the demand calculated using EPlus may not be correct. Then, where is the possible source of error? The EPlus program or the IDF or the curves produced by the manufacturer? By the time you have complete the study, you will be a weather data expert, an EPlus user expert on how to design a comfortable building without much HVAC, and understand a lot more about the various HVAC equipment available.
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> Dr. Li
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: marko.ignjatovic1980@...
> Date: Thu, 20 Dec 2012 09:20:41 +0000
> Subject: [EnergyPlus_Support] Re: Baseboard heater water inlet temperature higher than central boiler outlet
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> Dear Dr Li,
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> I am familiar (theoretically speaking) with calibration process, and know that I must record actual weather data and incorporate it in model, and in the same time to measure parameters in real system. Considering implementing real weather data (when measurements are going to be carried out) the idea is to do the following:
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> 1. epw file for my city (Nis, Serbia) translate in csv,
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> 2. in csv overwriting measured parameters with actual weather data (in particular day and time) like: dry bulb temp., humidity, wind speed and direction, barometric pressure (from on-site measuring equipment), Radiation (from local meteo station)
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> Considering measurements in the system, there is only one gas boiler supplying radiator heating system and unit heaters. Some measuring equipment is already installed like: gas meter, ultrasonic heat meter, supply and return temperatures for both radiator heating and unit heater branches. As a control I will measure indoor air temperatures in most of the zones.
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> Maybe on one radiator additional temp measurement could be carried out, but without flow measurement.
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> I must say it is industrial building and until now electricity measurements were main focus since large part of it is consumed by machines.
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> P.S. On what mail should I send you an IDF?
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> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@> wrote:
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> > Without the IDF I can only make guesses. My guess is that you were looking at the temperature of the baseboard heater when it is not in use. The baseboard heater is a zone equipment. when the water is not flowing, it follows the temperature of the zone. To verify, compare the value with the zone mean air temperature. Be very careful in your measurements. EPlus is demand and schedule driven. To compare the plant or system simulated results with these measured on a real equipment, the demand must be known and kept repeated to match that of the real weather when the measurements are carried out. This is not a simple project and have many problems that is at PhD level of investigation. Many user on this forum could not find the correct procedures to tackle this type of problems. What do you need to measure in order to define the demand of the real building and the capacity of the equipment? Dr. Li
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> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
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> > From: marko.ignjatovic1980@
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> > Date: Wed, 19 Dec 2012 12:53:40 +0000
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> > Subject: [EnergyPlus_Support] Baseboard heater water inlet temperature higher than central boiler outlet
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> > Dear All,
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> > I am modelling real building with hydronic heating system (radiators) using baseboardheater:water:convective objects. I followed the steps from engineering reference and entered manufacturer data where existed in the model. I also put control on the boiler in order to follow outdoor conditions.
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> > When I double checked variables in output I found that from 7 AM until app. 3 PM baseboard water inlet temperature is higher that the supply temperature (this is the case also when the heating system stops from 11 PM to 7 AM but it doesn't mater since there is no flow). After this period until 11 PM is lower. All pipes in the model were adiabatic.
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> > Where does this increase come from?
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> > If anyone needs clarifications I can e-mail *.IDF (although some names are in my native language).
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> > I am asking this because I want to calibrate this model to real measurements (most likely part of my PhD), and just checking things before any investments are made.
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> > Thanks in advance
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> > Marko
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