Building Design and use

Architecture

The building is a two room apartment model representing a real case study in Milan, which consists of two rooms and one bathroom. The bathroom and the nightzone are considered together in a single thermal zone. So in total, two thermal zones are considered. The aparment is a newly built heavy construction. The height of each room is 2.7 m, while the other dimensions are reported in the plan below.

SmallApartmentPlan.png

The journal paper cited below shows a brief validation of the envelope model using experimental data. However, KPIs results may differ using the latest version of the testcase due to updates with respect to the manuscript version in terms of internal gains, schedules and air mass exchange between the zones.

Zanetti E, Kim D, Blum D, Scoccia R, Aprile M. Performance comparison of quadratic, nonlinear, and mixed integer nonlinear MPC formulations and solvers on an air source heat pump hydronic floor heating system. Journal of Building Performance Simulation. 2022 Sep 15:1-9. [url]

Constructions

As can be seen from the plan, there are four different types of walls that, with the floor and the ceiling, constitute the boundaries of the thermal zones. All the geometrical and thermal characteristics of the various material layers are highlighted below.

External wall
N Description x
[m]		 k
[W/(mK)]		 c
[J/(kg K)]		 d
[kg/m3]		 absIR
[-]		 absSol
[-]
1 Exterior plaster 0.005 0.300 840 1300 0.9 0.6
2 EPS 120 thermal insulation panel 0.1 0.034 1250 23 - -
3 Masonry brick 0.3 0.207 840 750 - -
4 Gypsum plaster 0.02 0.570 1000 1300 0.9 0.6

Internal partition
N Description x
[m]		 k
[W/(mK)]		 c
[J/(kg K)]		 d
[kg/m3]		 absIR
[-]		 absSol
[-]
1 Gyproc Duragyp panel 0.0125 0.250 1000 1025 0.9 0.6
2 Plasterboard panel (WALLBOARD 13) 0.0125 0.250 1000 710 - -
3 Glass wool insulation panel (CTGS Par70) 0.07 0.040 840 40 - -
4 Plasterboard panel (WALLBOARD 13) 0.0125 0.250 1000 710 - -
5 Gyproc Duragyp panel 0.0125 0.250 1000 1025 0.9 0.6

Elevator separator
N Description x
[m]		 k
[W/(mK)]		 c
[J/(kg K)]		 d
[kg/m3]		 absIR
[-]		 absSol
[-]
1 Gypsum plaster 0.02 0.570 1000 1300 0.9 0.6
2 Concrete 0.3 2.15 880 2400 - -
3 Glass wool insulation panel (Par45) 0.045 0.038 1030 13 - -
4 Plasterboard panel (WALLBOARD 13) 0.0125 0.250 1000 710 - -
5 Gyproc Duragyp panel 0.0125 0.250 1000 1025 0.9 0.6

Apartments separator
N Description x
[m]		 k
[W/(mK)]		 c
[J/(kg K)]		 d
[kg/m3]		 absIR
[-]		 absSol
[-]
1 Gyproc Duragyp panel 0.0125 0.250 1000 1025 0.9 0.6
2 Plasterboard panel (WALLBOARD 13) 0.0125 0.250 1000 710 - -
3 Glass wool insulation panel (CTGS Par70) 0.07 0.040 840 40 - -
4 Plasterboard panel (WALLBOARD 13) 0.0125 0.250 1000 710 - -
5 Glass wool insulation panel (CTGS Par70) 0.07 0.040 840 40 - -
6 Plasterboard panel (WALLBOARD 13) 0.0125 0.250 1000 710 - -
7 Gyproc Duragyp panel 0.0125 0.250 1000 1025 0.9 0.6

Ceiling
N Description x
[m]		 k
[W/(mK)]		 c
[J/(kg K)]		 d
[kg/m3]		 absIR
[-]		 absSol
[-]
1 Ceramic tiles 0.015 1.000 840 2300 0.9 0.6
2 Concrete slab with additive 0.064 1.000 880 1800 - -
3 Expanded polystyrene 0.026 0.034 1300 25 - -
4 Isover fonasoft 0.006 0.113 2100 450 - -
5 Light substrate 0.105 0.100 1200 400 - -
6 Reinforced concrete (1% steel) 0.230 2.300 1000 2300 - -
7 Gypsum and sand plaster 0.200 0.800 1000 1600 0.9 0.6

Radiant floor
N Description x
[m]		 k
[W/(mK)]		 c
[J/(kg K)]		 d
[kg/m3]		 absIR
[-]		 absSol
[-]
1 Ceramic tiles 0.015 1.000 840 2300 0.9 0.6
2 Concrete slab with additive 0.064 1.000 880 1800 - -
3 Expanded polystyrene 0.026 0.034 1300 25 - -
4 Isover fonasoft 0.006 0.113 2100 450 - -
5 Light substrate 0.105 0.100 1200 400 - -
6 Reinforced concrete (1% steel) 0.230 2.300 1000 2300 - -
7 Gypsum and sand plaster 0.200 0.800 1000 1600 0.9 0.6

These properties are defined in the model of each thermal zone respectively in the component matExtWal, IntWall, ElevatorSep, AptSep, roof and slaCon. All the material layers are defined starting from outside to room-side except for the radiant floor that requires the opposite order, as reported in the Modelica Buildings Library envelope user guide.

Considering the two glazing systems of the small apartment, they have the same construction and shading system, differing only in the dimensions. These characteristics are reported in the tables below.

Glazing system dimensions
Room height
[m]		 length
[m]
Day Zone 2.35 2.5
Night Zone 2.35 1.6

Glazing system physical properties
N Description x
[m]		 k
[W/(mK)]		 tauSol
[-]		 rhoSol
[-]		 tauIR
[-]		 absIR
[-]
1 Glass 0.003 1 0.6 0.075 0 0.84
2 Air 0.013 - - - -
3 Glass 0.003 1 0.075 0 0.84
Shading system physical properties
tauSol
[-]		 rhoSol
[-]		 tauIR
[-]		 absIR
[-]
0.1 0.8 0 0.84

The dimensions of the glazing system of the two thermal zones that face towards outside are two parameters that have been defined in the zone components, while the glazing system and shading system physical properties have been defined in the record "Window24".

The thermal zone model also includes the radiant slab component taken from the Modelica Buildings Library. The properties are reported in the following table.

Radiant slab properties
Pipe distance [m] 0.1
Interface layer in which pipes are located [-] 2
Pipe properties
Outer diameter [m] 0.017
Inner diameter [m] 0.015
Roughness [m] 0.000007
Density [kg/m3] 983
Thermal conductivity [W/(m K)] 0.4

Occupancy schedule

The apartment is occupied from 8 P.M. to 8 A.M. from Monday to Friday by two people, one per thermal zone. The thermal zones are considered unoccupied on Saturday and Sunday.

Internal loads and schedules

The heating setpoint is considered 21 [°C] for occupied periods and 16 [°C] for unoccupied periods. The main heat gains come from people, appliances and lighting. For people it corresponds to 60 (W/person) of sensible gains divided equally between convective and radiative contributions and 20 (W) of latent gains. Internal gains for the appliances are 4 (W/m2) and for lighting 1.5 (W/m2) of sensible gains were considred divided equally between convective and radiative contributions. These values are taken from a combination of ASHRAE 90.1 standard and ENI 13200. CO2 generation is 0.0048 L/s per person (Table 5, Persily and De Jonge 2017) and density of CO2 assumed to be 1.8 kg/m^3,making CO2 generation 8.64e-6 kg/s per person.Outside air CO2 concentration is 400 ppm. However, CO2 concentration is not controlled for in the model. Lastly, infilatrations was considered a constant value of 0.5 (vol/h) for each thermal zone.

Climate data

The climate is assumed to be near Milan, Italy with a latitude and longitude of 45.44,9.27. The climate data comes from the Milano Linate TMY set.

HVAC System Design

Primary and secondary system designs

Only heating is considered. The HVAC system is made up of two floor heating circuits, one per thermal zone that can be controlled with an on-off valve. The generation system is an air source heat pump with a nominal heat capacity of 5kW modelled after a Daikin heat pump. Below is reported a schematic view of the HVAC system.

HVACscheme.png

Equipment specifications and performance maps

The heating system circulation pump has the default efficiency of the pump model, which is 49%; at the time of writing. The flow rate for each thermal zone floor heating circuit is 620 [l/h]. The heat pump perfomance map is the default map present in the IDEAS Library heat pump model coming from a Daikin heat pump.

Rule-based or local-loop controllers (if included)

The default controller has two levels of control. The first level is done by the thermostats using a hysteresis controller with 2 [K] bandwidth. When the room temperature is lower than setpoint minus half the bandwidth the thermostat will open the floor heating circuit valve. Viceversa, when the room temperature is higher than setpoint plus half the bandwidth the thermostat will close the valve. The second level controller controls the heat pump supply temperature using a climatic curve based on the external temperature and an hysteresis controller. The figure below reports a scheme of the controls.

ControlScheme.png

Model IO's

Inputs

The model inputs are:

Outputs

The model outputs are:

Forecasts

The model forecasts are:

Additional System Design

Lighting

Artificial lighting is provided by LED lights in the thermal zones.

Shading

There are no shades on the building.

Onsite Generation and Storage

There is no energy generation or storage on the site.

Model Implementation Details

Moist vs. dry air

A moist air model is used, but condensation is not modeled in the HVAC and humidity is not monitored.

Pressure-flow models

The pump is an ideal constant head pump and provided each floor heating circuit with exactly 620 [l/h] if the circuit valve is open.

Infiltration models

A constant infiltration flowrate is assumed to be 0.5 ACH.

Other assumptions

No further assumptions are needed.

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

The Constant Electricity Price (specifier for /scenario API is 'constant') profile is:

The Dynamic Electricity Price (specifier for /scenario API is 'dynamic') profile is:

The Highly Dynamic Electricity Price (specifier for /scenario API is 'highly_dynamic') profile is:

Emission Factors

The Electricity Emissions Factor profile is: