Transcript Building simulation conference - 27th July 2009 - Glasgow Dynamic simulation of a complete solar assisted air-conditioning system in an office building.

Building simulation conference - 27th July 2009 - Glasgow
Dynamic simulation of a complete solar assisted air-conditioning
system in an office building using TRNSYS
ID 555
Sébastien Thomas and Philippe André
Department of sciences and environmental management, University of Liège
185 Avenue de Longwy, 6700 ARLON, Belgium
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Presentation overview
1. Introduction
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4
2. Simulation environment overview
3. Building
4. H&C emission and distribution
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5
5. H&C production and storage
6. Results & Conclusion
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1
Presentation overview
1. Introduction
2
4
2. Simulation environment overview
3. Building
4. H&C emission and distribution
3
5
5. H&C production and storage
6. Results & Conclusion
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Introduction : Solar air-conditioning context
Building cooling has an important impact on energy consumption,
therefore on CO2 emissions.
Moreover, strong increase in cooling installed capacity has been
encountered last years.
Assets for solar energy :
- It is one of the largest renewable
energy ressource
- There are many ways to convert
solar energy into cooling effect
- Sunny locations have more cooling
needs
Market available solar cooling
technologies
-Absorption chiller
-Adsorption chiller
-Desiccant equipment
-PV panels with classical vapour
compression chiller
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Introduction : key asset of solar energy
- The cooling load of buildings is generally high when solar radiation is high
 yearly basis
Src: (2007). Solar Air-Conditioning, 2nd International
Conference Proceedings. Regensburg, Germany,
Ostbayerisches Technologie-Transfer-Institut e.V. .
 daily basis
For an office building in August in Paris
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Introduction : Market status of Solar air-conditioning
Cooling power installed worldwide is 20 MW1.
- It represents 250 to 300 installations, from few kW cold to 1 MW cold
- Absorption is still leading the market
- Solar air-conditioning systems are installed in
Office buidings (60%)
Laboratory, Hostels, Industry, Library, …
Solar cooling costs distribution 2
Development closely linked to its economical profitability, thus it is important to
evaluate energy savings and their essential parameters …
1. Src: (2009). R. Gartner
Sun & wind energy magazine 1/09
2. Src (2008) : A. Preisler
ROCOCO project publishable part
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1
Presentation overview
1. Introduction
2
4
2. Simulation environment overview
3. Building
4. H&C emission and distribution
3
5
5. H&C production and storage
6. Results & Conclusion
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Simulation environment overview
Integral approach to evaluate energy savings : Complete simulation
environment is presented (TRNSYS is used to do this)
Sub-systems implementation :
- Building
- Hot and Cold distribution and emission
- Hot and Cold production and storage
- Climate
 Combined simulation of these sub-systems
 Possibility to substitute components
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Simulation environment overview
TRNSYS implementation of Sub-systems
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1
Presentation overview
1. Introduction
2
4
2. Simulation environment overview
3. Building
4. H&C emission and distribution
3
5
5. H&C production and storage
6. Results & Conclusion
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Building modelling
IEA-ECBCS 48 European typical office building 1-c
 Paris Climate
Complete building (3 identical floors)
modeling including :
- 5 thermal zones
- Ventilation
- External shading modulation*
- Light intensity modulation
- Occupancy profile for each zone
- Internal gains profiles
> People
> Appliances
> Light
*External shading modulation : Manual solar protections, shading fraction depends on
solar radiation on window surface. Solar protections do not move when no occupancy
Stabat P. 2007. IEA48 – Description of Type 1c airconditioned
office buildings for simulation
test,.IEA-ECBCS Annex 48 working
document.
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1
Presentation overview
1. Introduction
2
4
2. Simulation environment overview
3. Building
4. H&C emission and distribution
3
5
5. H&C production and storage
6. Results & Conclusion
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Heating and Cooling emission and distribution
This layer is linked with H&C production and building layers
When computing heating and cooling load using Type 56, control and distribution
losses are not handled : implementation done here takes these losses into account.
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Fan Coil Units modelling
It has been chosen to use a real FCU where manufacturer data is available.
To model heating/cooling coil in a FCU, TRNSYS gives some possibilities :
- Using one of the numerous available types of heating cooling coil :
Effectiveness approach, Bypass approach, …
 Tuned with one parameter, not accurate for the whole coil
range of temperatures, mass flow
- Read manufacturer data using type 697
 Manufacturer data needs to be post processed to suit to type 697,
it can be source of errors
- Implement a polynomial approximation of coil behavior based on the
whole manufacturer data and integrate it into a TRNSYS equation
 This last solution is chosen :
Heating coil sensible heating energy = f((Twater supply – Troom),Water mass flow)
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1
Presentation overview
1. Introduction
2
4
2. Simulation environment overview
3. Building
4. H&C emission and distribution
3
5
5. H&C production and storage
6. Results & Conclusion
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Heating and cooling production and storage
The picture represents the lowest energy consumption configuration for this layer
Mistake in the text : 142,3 m²  200 m²
Sub-system main components (for one floor) :
- Evacuated tube collector
- Storage tank
- Absorption chiller
COPnom
- Back up boiler
- Cooling tower
- Backup chiller
COPnom
200 m²
7 m³
105 kWC
0.695
150 kW
263 kW
105 kWc
3.5
For each component, parameters have been fixed
based on market available equipment.
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Simulation of solar air-conditioning system : chiller control
It appears that absorption chiller control
has a huge impact on energy consumption
3 strategies have been developed:
case
A
B
case
A : Gas and sun are the only energy sources
B : Storage is not heated by boiler,
when tank temperature is not enough
to feed ABS, vapour compression
chiller (VCC) is used.
case
storage is not used for building heating
C : idem than B but
storage is also used for heating
Comparison is done with classical A-C (vapour compression chiller – gas boiler)
C
For Paris climate
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Absorption chiller new type
Existing type 107 : energy balance but no dynamic effect
based on external performance data file
Read in
Data file
f nc
f dei
Fraction of nominal capacity
Fraction of design energy input
Depends on current conditions : Chilled water set point, Entering cooling water
temperature, Inlet hot water temperature, part load ratio (fraction of design load)
Cold production and Hot water
consumption are computed
Qc  Qc,rated . f nc
Qh 
Qc,rated
COPrated
. f dei
Things to take care :
-Fraction of nominal capacity is limited to 1  Rated power is maximum power
- Part load ratio independent of current condition (based on rated capacity only)
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Absorption chiller new type
- Part load ratio independent of current condition (based on rated capacity only)
When dealing with classical chiller (e.g. type 655), part load ratio (so called fraction
of design load in type 107) is the load met by the chiller divided by the capacity of
the chiller at the given conditions.
Obviously it is between 0 and 1
In type 107, part load ratio is load met by the chiller divided by the capacity of the
chiller at the rated conditions.
It implies values larger than 1 and has less sense than previous definition
New type 255 = existing type 107 + part load ratio depending on current conditions
PLR 
Qcool required
Qcool chillernom
TChilled water setpo int
Thot water in
Tcooling water in
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1
Presentation overview
1. Introduction
2
4
2. Simulation environment overview
3. Building
4. H&C emission and distribution
3
5
5. H&C production and storage
6. Results & Conclusion
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Simulation of complete solar air-conditioning system : results
Building Heating and Cooling loads
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Simulation of complete solar air-conditioning system : results
SF 
Collector energy
Collector energy Boiler cons.  VCC cons.
SF Cooling 
Load m et by ABS chiller
Load m et by ABS chiller  Load m et by VCC chiller.
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Simulation of complete solar air-conditioning system : results
H&C and auxiliaries consumptions have been computed
H&C
Auxiliaries
Case A
For Paris climate
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Conclusions and next developments
A complete office building solar air-conditioning application was presented
and divided into three major parts to enhance readability.
System control has a huge impact on energy consumption. It appears that
VCC chiller as backup is useful for energy savings (but implies cost of new
equipment). Savings reach more than 30% !
Solar air-conditioning is efficient when used in efficient buildings. Work
can be done to decrease cooling load. In actual office building simulations,
auxiliaries have a great impact on the whole building energy consumption.
Limitations – Next developments
- Steady state absorption chiller model
- Control strategy improvements should be done
(e.g. adjust hot water temperature to cooling load)
- Convergence problems with hot water storage
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