Single-zone emulator (by University of Southern Denmark)

General model description


Building Design and Use

The overall description of the actual building can be found in the following paper: M. Jradi et al., A World Class Energy Efficient University Building by Danish 2020 Standards, Energy Procedia 132 (2017), 21-26. Some of validation reference data are taken from this paper directly. The following documentation contains only information relevant for the simplified model included in BOPTEST. Additional details regarding the simplified building validattion can be found in the following paper: T. Tang et al.,Implementation and performance analysis of a multi-energy building emulator, In Proc. of 2020 6th IEEE International Energy Conference (ENERGYCon), Sep 28 - Oct 1.

Architecture

The building surface area is 8500 m2. There are 3 above-ground floors containing classrooms (40% of floor area), study zones (25%), offices (15%), and common spaces (20%). There is also a basement level containing main HVAC facilities and the main heat exchanger connected to district heating. The building can accommodate around 1350 people.

Constructions

The building thermal envelope is comprised of three different opaque constructions: ground floor (floor), external wall (extWall), and roof (roof). The internal walls are modeled by a single-layer generic construction representing medium-weight partitions. All opaqua construction layers and thermal characteristics are described in Table 1. All windows are modeled using the same contruction type, based on a triple-glass window model from the Buildings library (Buildings.HeatTransfer.Data.GlazingSystems.TripleClearAir13ClearAir13Clear), with the following layers: triple pane, clear glass 3mm, air 12.7 mm, clear glass 3mm, air 12.7 mm, clear glass 3mm.

Table 1: Opaque constructions and their thermal parameters (x - width [m], k - conductivity [W/(mK)], c - specific heat [J/(kgK)], d - density [g/cm3])

Construction

Layers

Parameters (x, k, c, d)

floor

Concrete

0.2, 1.4, 840, 2.24


Insulation

0.15, 0.04, 1000, 0.05

extWall

Concrete

0.2, 1.4, 840, 2.24


Insulation

0.27, 0.04, 1000, 0.05

roof

Concrete

0.27, 1.4, 840, 2.24


Insulation

0.52, 0.04, 1000, 0.05

intWall

Generic material

0.15, 0.5, 1000, 0.25

Occupancy schedules and comfort requirements

The building is equiped with camera-based sensors that estimate real-time occupants number. Occupancy data is extracted from our internal database"Volta" and stored in "occ.txt" file in the model. Comfort requirements are defined as indoor thermal comfort (temperature) and CO2 concentration, with the temperature setpoint as 21°C during occupied hours (7 AM to 7 PM on weekdays) and 15°C otherwise and CO2 concentration upper limit as 800ppm.

Internal loads and schedules

Internal heat gains only consider heat from occupancy. It is assumed that the internal gain per person is 120W and it is evenly distributed over the floor area (i.e. 120 W / 8500 m2). The heat generated per occupant is divided as 40% radiant, 40% convective and 20% latent heat.

Climate

The weather data is based on Copenhagen Typical Meteorological Year. The weather file is located in modelica://OU44Emulator/Resources/Weather/DNK_Copenhagen.061800_IWEC.mos.

HVAC System Design

Primary and secondary system designs

The actual building is equipped with 4 balanced Air Handling Units (AHU) with heat recovery wheels and pre-heating coils (Fig. 1) and each room is equipped with radiator heating. The heating is provided by district heating grid. Since the model is a single-zone model, all AHUs are modeled with a single AHU oversized by a factor of 4, and all radiators are modeled with a single radiator. The following description covers the HVAC design as implemented in the model, and not the HVAC system in the actual building. The AHU contains two identical fans, one for supply air and one for extract air. The nominal air volume flow rate capacity is 140000 m3/h. Both the radiator and the pre-heating coil in the AHU are connected to the main heat exchanger connected to the district heating grid. The water flow to the radiator and AHU's pre-heating coil is controlled with two 3-way valves. In real building, supply air of ventilation is controlled via adjusting damper position, and temperature of supply air from ventilation has been controlled to be 21° C.

Fig. 1: Air Handling Unit diagram with exemplary measurements from the BMS system (screenshot).

Fig. 2: Hydronic heating system as modeled.

Rule-based or local-loop controllers

The model implements three PI controllers. The first, with parameters kp=0.1 and Ti=600 s, regulates indoor CO2 concentration to the upper limit by controlling the supply fan speed in the air handling unit. The second, with parameters kp=0.05 and Ti=800 s, regulates the supply air temperature of ventilation to be consistent with setpoint by controlling the hot water coil valve position in the air handling unit. The third, with parameters kp=0.05 and Ti=800 s, regulates indoor temperature of the zone to the heating set point by controlling the hot water valve position serving the radiator.

Model IO's

Inputs

The model inputs are

Outputs

The model outputs are

Forecasts

The model forecasts are

Additional System Design

Lighting

Lighting is not considered in the model.

Shading

The model assume there is no shading in the building.

Onsite generation and storage

There is no onsite power generation or energy storage in the model.

Model Implementation Details

Moist vs .dry air

The model uses moist air despite that no condensation is modelled in any of the used components.

Pressure-flow models

A circulation hot water loop is used to model the heating emission system.

Infiltration models

Inflitration is modeled with a fixed ACH parameter (0.2).

CO2 models

CO2 concentration of the zone is included in the model. We introduce a scale factor of 4 for occupancy CO2 generation to calibrate control of the AHU with real building operation, since the model is lumping unoccupied zones with occupied zones that would drive AHU usage in real building operation.

Important Model Implementation Assumption

The major assumptions are as follows:

Scenario Information

Time Periods

The Peak Heat Day (specifier for /scenario API is 'peak_heat_day') period is:

The Typical Heat Day (specifier for /scenario API is 'typical_heat_day') period is:

Energy pricing

Energy Price consists of electric power price and district heating price.

Electric power price:

Distric heating price=0.0828 euro/kWh,source:https://www.c40.org/case_studies/98-of-copenhagen-city-heating-supplied-by-waste-heat

Emission factors

Two emission factors are considered based on Danish scenario: