[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: [EnergyPlus_Support] Re: Baseboard heater water inlet temperature higher than central boiler outlet

Hi, Marko

I was not involved directly in doing the reserch work using the EPlus.  I help him in solving the IDF input problems, because I had more programming experience and could follow the error messages and find the errors for him.
As I followed his progress I noticed that the EPlus is a schedule driven simulation program.  It uses the epw TMY weather input to calculate effect of the weather on the  the building heat balance.  Set points are used to define the required HVAC conditions in the zones.  The energy required to bring the temperature to the setpoint temperature in a zone is the energy demand of that zone.  Therefore, if the cooling or heating setpoint temperature is set  higher or lower than the natural zone temperature, the HVAC demand is zero.  All zone, system equipment, plants would be turned off.
The zone thermostat can normally control one device. If a device which does not turn off at low  or zero demand, the system or plant would remain on and uncontrolled, to produce temperature too high or too low problems.
The calculation is one wat from demand to the plant source.  One cannot define a plant condition to control the zone demand.  This is why, if the boiler temperature is known and changed, the zone temperature cannot be calculated or controlled, even if the HW flow rate through the baseboard heater is kept constant.  If the weather is not changed, the zone thermostat would turn on and off the HW in order to maintain the zone temperature.  The PLR is changed.
When you have a multi-zone building feeding from one plant, the plant PLR may not be synchronized with the  zone PLR.  In a real system, the fuel consumption, or the fire comes on and off as the temperature of the HW tank of the boiler.  You have set up your measuring system to do this, but it is not used in the same way in the EPlus simulation.  This is one possible one mismatch point.
Similarily, a system providing an air loop to the zones depends on the use of the manufacturer's  efficienty curves to convert the energe used to the electrical source enrgy to run the equipment.  This can be done when the demand is known, and not the other way a round.  To calculate the demand, local weather condition must be known.  This is the second  difficult task, because the local weather condition cannot be simply obtained unless you measure all the parameters yourself.
Local wether condition cannot be easily measured.  For example, if you measure the outdoor temperature on the four sides of the building, you may find them provide different readings.  It is also height wind dependent.
EPlus only have one value for the exterior temperature of a wall.  How do you measure this temperature? This is another difficult task in real measurement.  How or where to place the thermometer to     
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.




Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx

The primary EnergyPlus web site is found at:

The group web site is:

Attachments are currently allowed but be mindful that not everyone has a high speed connection.  Limit attachments to small files.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.

Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe