The role of building-energy and urbanenvironment simulation methods in the
implementation of the 2010/31/EU
directive
The REPUBLIC Med project
Dr. George M. Stavrakakis
Recent directives
31/2010/EC
NZEB by 2018 and later for New public financed buildings.
27/2012/EC
Existing public buildings
Acceleration of public-buildings renovation: 3% of the total usable surface area of
buildings owned or occupied by the central government should be renovated each
year towards the accomplishment of minimum energy performance requirements
set in each MS.
EPBD definitions
•
•
•
•
•
•
“NZEB means a building of very high energy performance. The low amount of
energy required should be covered in a significant extent by energy from RES,
including RES on-site or nearby”
“BEP should be expressed through numeric indicator of primary energy use…”
“The calculation methodology should take into account European Standards and
shall be consistent with relevant Union legislation…”
“BEP shall be determined on the basis of the calculated or actual annual energy
consumed in order to meet the different needs associated with its typical use and
shall reflect the heating energy needs and cooling energy needs to maintain the
envisaged temperature conditions of the building and DHW needs.”
“When undergoing major renovation, existing buildings shall have their energy
performance upgraded so that they also satisfy the minimum requirements.”
“Member States shall put in place, in compliance with the aforementioned
calculation methodology, minimum requirements for energy performance in
order to achieve cost-optimal levels.”
Issues raised
•
What is a NZEB? Are any specific thresholds?
•
How reliable are simulation methods in predicting the primary and final energy
consumption?
•
How should input data and modelling uncertainty and the quest for robust designs
be integrated into simulation?
•
How should data be acquired and managed?
•
How can output of simulation be used for compliance?
•
How shall we implement cost-optimality conditions for defining minimum
requirements?
Topics of Analysis [1/4]
NZEB definition
In some MS there is still no specific definition of NZEB in terms of energy indicators’
thresholds, of a specific extent the reduced energy should be covered by RES, and of
the “nearby” term interpretation.
Need: Formulation of a sustainable, effective and practical NZEB definition
Recommendations*:
- The definition has to be reviewed in relation to the boundaries of the climate and
energy resources.
- Specification of “nearby” term.
- Specification of thresholds and additional energy and environmental indicators.
- Improvement of CEN energy calculation models (including occupants’ behaviour).
- NZEB will require high energy share in the construction phase=> LCA is also
required.
* Evaluating and Modelling Near-Zero Energy Buildings; Are we ready for 2018?, JRC Technical Reports, Expert meeting 30-31 Jan 2012, Glaskow.
Topics of Analysis [2/4]
State of the art of building simulation software
- Simulation for compliance: Concluding NZEB based on national tools (in some MS important
parameters are neglected, e.g. energy behaviour and external microclimate effects)
- Simulation for reliable predictions: Concluding NZEB based on novel tools accounting for
“uncertainties”
Need: Bridge the two simulation concepts towards recommendations for simulation tools
revision
Recommendations*:
- Include dynamic terms (max: hourly simulations).
- Prescribe input fields for innovative technologies.
- Improving usability=> Creation of skilled modellers.
- Extension of boundary conditions to account for external microclimate effects and for
interactions with the wider energy system.
- In policy-making terms new CEN standards should ensure design freedom. If CEN produce
prescriptive methods (again) then this will restrict novel methods and, consequently, it will
restrict the promotion of better-than-compliance performance.
* Evaluating and Modelling Near-Zero Energy Buildings; Are we ready for 2018?, JRC Technical Reports, Expert meeting 30-31 Jan 2012, Glaskow.
Topics of Analysis [3/4]
Occupancy related issues
BEP should be evaluated taking into account occupancy profiles patterns impact.
Need: Account for realistic occupancy behaviour patterns effects in the design stage
Recommendations*:
- Bottom-up approach: Stochastic models for predicting occupants’ journeys,
presence at each destination and presence-dependent activities and related
behaviours.
- Top-down approach: Identification of behaviour profiles effects through smart
metering and/or questionnaires.
- Simulation tools should provide access to systems’ schedules to incorporate
energy-related activities.
* Evaluating and Modelling Near-Zero Energy Buildings; Are we ready for 2018?, JRC Technical Reports, Expert meeting 30-31 Jan 2012, Glaskow.
Topics of Analysis [4/4]
Input data and optimization
Important input data referring mainly to boundary conditions when setting up the
simulation problem should overcome the barrier of being considered as
“Uncertainties”, e.g. climate data time series and realistic properties of technologies.
In addition, cost-optimal minimum requirements should be concretely defined.
Need: Account for physical and technology “uncertainties” as well as for coupled
optimization methods
Recommendations*:
- Indoor-outdoor physical interactions should be taken into account in the study
phase.
- Provision of realistic properties of technologies should be boosted by policy
makers.
- Numerous exercises and scenario assessments and in some level optimization
approaches are required to conclude cost-optimal minimum requirements.
* Evaluating and Modelling Near-Zero Energy Buildings; Are we ready for 2018?, JRC Technical Reports, Expert meeting 30-31 Jan 2012, Glaskow.
Design for
reliable
predictions
Methods thatBuildings
respond to new
Open spaces
forinteractions
directives
-requirements
- Indoor-outdoor
UHI assessment
implementation
- - Energy
Plans
behaviour
to introduce
New
insights
on urban approach to
Optimization
-
Pilotpolicy
applications
Retrofit
technologies
makers
environmental
planning
Training seminars
Design for
compliance
-
-
Enrich design for compliance
Impact of accounting for external
microclimate effects
Impact of accounting for behaviour
Reduce uncertainties
Optimization=> Possibilities in costoptimal minimum requirements
Train the stakeholders
Physical models-Buildings
Building Thermal Behaviour Modelling
Method
Technical
approach
Application field
Field models (CFD)
Discretization
into control
volumes
Contaminant distribution
Finite volume
method
Advantages
Detailed description of
the airflow field within
Evaluation of Ventilation buildings
systems regarding the
creation of comfortable Accounting for physicaland healthy
parameters nonenvironments.
uniformity
Drawbacks
High computational time
requirements for high
computational resources
Modelling complexity.
Perception of comfort
and air quality
Multi-zonal (BES)
Discretization
into thermal
zones
Perfect mixing
Finite difference
method
Determination of total
energy consumption
Indoor average
temperature
cooling/ heating loads;
Time evolution of energy
consumption.
Accounting for external
microclimate effects.
Whole building energy
simulation over long
time periods
Reasonable
computational time
within modest
computational resources
Difficulty to study large building
spaces
Unable to study local effects as
heat or pollutant source
Disregard external airflow
effects.
Multi-zonal approach/BES tools
The US Department of Energy has developed a directory of building energy software
tools which reports 402 building software tools for evaluating energy efficiency,
renewable energy and sustainability in buildings.
http://apps1.eere.energy.gov/buildings/tools_directory/
Tools often used for whole building energy performance assessment
Autodesk Green DeST
Building Studio
ENER-WIN
ESP-r
SUNREL
BEAVER
DOE-2
Energy plus
IDA-ICE
TAS
BSim
ECOTECT
eQUEST
IESVE
TRNSYS
Most popular BES tools
DOE-2:
EnergyPlus:
TRNSYS:
Predicts
Modular
It isthe
a simulation
structure
hourly energy
that
engine
implements
usewith
andinput
energy
aand
component-based
cost
output
of a building
of text files.
approach.
given
Loads
hourly
Its
are
weather
calculated
components
information,
by amay
heatbebalance
aasbuilding
simple
engine
geometric
as a at
pump
a user-specified
and
or pipe,
HVAC
ordescription,
astime-step
complex and
as
anda they
utility
multi-zone
are
rate
structure.
passed
building
to model.
It
the
has
building
one
Building
subprogram
systems
inputsimulation
data
for translation
is entered
module
through
of at
input
thea(BDL
same
dedicated
processor)
time-step.
visual
and four
simulation
interface
subprograms.
(TRNBuild).
Each of themodule,
simulation
subprograms
also produces
EnergyPlus
building
systems simulation
with
a variable time-step,
calculates
printed
reports
of thesystem
resultsand
of its
calculations.
TRNSYS
heating
library
and cooling
includes
components
electrical
for
solarsystem
thermal
response.
and photovoltaic
This integrated
systems, low
DOE-2
solution
energy
has been
provides
buildings
used extensively
more
and HVAC
accurate
systems,
for space
morerenewable
than
temperature
25 years
energy
prediction,
for both
systems,
building
which
cogeneration,
design
is crucial
studies,
for
fuel
system
cells,
analysis
and
etc. plant
of retrofit
sizing,opportunities,
occupant comfort
and for
anddeveloping
occupant health
and testing
calculations.
building
energy
Integrated
standards
simulation
in thealso
US allows
and around
users the
to evaluate
world. realistic system controls,
moisture adsorption and desorption in building elements, radiant heating and
cooling systems and interzone airflow.
Strengths and weaknesses of BES tools [1/5]
Tool
Autodesk
Green
Building
Studio
BEAVER
Strengths
> Provision of hourly
whole building energy,
carbon and water
analysis
> Reduces design and
analysis costs, allowing
more design options to
be explored
> Accelerates analysis
for LEED compliance
> Hourly whole building
energy consumption
> Estimation of building
structure and systems'
types to maintain
specific environmental
conditions
> Modelling of a wide
range of building
services
> inputting of data can
be very rapid compared
to most other similar
programs
Handling of
climate
Weaknesses
conditions
> Resulting
> Input
DOE-2 and
available data
EnergyPlus
of specific
models can be climate zones
very detailed
> User-defined
climate-data
time series
In terms of user
friendliness, reliability
> Some system
types are not
and applicability
included and
it does not
model chilled
and
condenser
water loops
> limited range
of windows
available for
selection
> It cannot
model natural
ventilation or
daylighting
Special features
Handling of
building systems
operating
schedules and
occupancy
Building systems
> User-defined
> Common building
schedules
systems for heating,
cooling, Domestic Hot
Water (DHW), etc.
> Determination of
renewable energy
potential
(Photovoltaic and
wind)
In terms of Flexibility in input data:
- External climatic conditions
- Profiles
of systems’> Detailed
schedules
> Input
> User-defined
schedules
available
representation
- data
Options
of building
systems’of
of specific
heating and cooling
climate zones
systems
representation
> User-defined
climate-data
time series
(measured or
simulated)
> Various extra
components or
operating strategies
can be added
including Heat
Recovery, Preheating
Coils, Exhaust Fan,
Temperature reset on
heating and cooling
coils, etc.
Most
common
application
s
Whole
building
thermal
performan
ce
Availa
bility
Subscr
iption
webbased
servic
e
In terms of
common
cases the
tool is used
Whole
for and ofCom
its
building
merci
al
energy
availability
performan
(commercial
ce
or Free)
Physical models- Open spaces [1/3]
“The Urban Heat Island is the most obvious climatic manifestation of urbanization”
Landsberg, 1981
Causes:
 Decreased
Reduced
potential
convective
for
heat
evapotranspiration
removal
due
to
the
reduction
ofsky-view
wind
speed
Trapping
long-wave
short
and
radiative
long-wave
heat
radiation
loss
due
in areas
to
reduced
between
buildings
factors
Increasedof
Anthropogenic
storage
heat
of
released
sensible
heat
from
in
fuel
the
combustion
construction
materials
Urban Heat Island Effect
Physical models-Open spaces [2/3]
Approach
UCM
CFD
Macroscale
Comfort indicators
- Comfort and air quality indicators
Simulation of heat conservation effects - Fairly accurate
Fairly accurate
- Main use: UHI effects on global
Main use: UHI effects on comfort
climate change
indicators of pedestrians and on
building energy performance
Microscale
Advantages
-
- Comfort and air quality indicators
- Accurate
- Main use: UHI effects on comfort and
air quality of pedestrians and on
building energy performance
Major limitations
- Decoupled velocity field
- Limited resolution of building
geometries
- Applied for steady-state simulations
mainly
- Empirical assumptions for convective
latent and sensible heat
- Assumption of the urban canopy
layer as roughness
- Difficult to provide Land-use profiles
(user-defined functions are required)
- Turbulence modelling is required
- Planetary Boundary Layer effects are
ignored
- Complex setting up
- Reliable boundary conditions are
required
- Turbulence modelling is required
Maximum size of
city-scape domain
Spatial resolution for
grid meshing
Temporal resolution
(time-step)
Computational cost
Whole City
Whole City
Building block
1-10 m
1-10 km
0.2-10 m
Hour
Minute
Second
Medium
High
Very high (depending on the turbulence
model applied and grid size)
Physical models- Open spaces [3/3]
MESOSCALE CFD MODELLING
Evaluation of UHI impact on global climate change
UCM may be used
MICROSCALE CFD MODELLING
Evaluation of UHI impact on pedestrian comfort, air quality and
building energy consumption
UCM may be used for more approximate estimations
Open spaces-Tools [1/5]
Rayman:
ENVI-met:
Fluent:
ItDeveloped
isItthe
is aone
micro-scale
in
of the
the Meteorological
most
model
complete
for theInstitute
platforms
prediction
ofexisting
Albert-Ludwigs-University
of UHI in
effects
the CFD
within
industry
the urban
of
Freiburg,
canopy with
including
itwell-known
is aacceptable
variant and
of accuracy
energy
the latest
balance
fordevelopments
relatively
models,
simple
and
of itfluid-flow
geometries.
is used mainly
related
It isto
amodels.
3D
compute
model
In for
radiant
simulating
addition
heat
tomicroclimate,
phenomena
fluxes from the
simulated
taking
human
intoby
body.
account
ENVI-met,
Thethe
inputs
itphysical
includes:
the user
interactions
Ahas
wide
tovariety
provide
among
ofare
solid
the
following:
surfaces (e.g.
turbulence
temporal
models;
ground
data
Aand
wide
(date
building
variety
and hour);
surfaces),
of two-phase
Geographical
vegetation
flow models
data
and (longitude,
air.
to Itcapture
is based
latitude
particles
on theand
elevation);
theoreticalmeteorological
dispersion;
background
A wide variety
ofdata
of
CFD.
radiation
(temperature,
modelsrelative
to simulate
humidity
shortand
andcloud
long wave
covering);
personal
radiation;
parameters
A pluralism
of grid-meshing
and activity
options
level);
including
Geological
structured
morphology;
and unstructured
urbanrelative
Inputs: properties
of(clothing
the
incoming
wind
(wind
speed,
direction,
temperature,
design
grids
to
features
build
grids
(buildings,
with
the
trees).
minimum
computational
ensuring adequate
humidity);
simplified
geometry
of the urban
domain; cost
thermo-physical
properties of
resolution
ofbuilding
results;by
Access
toand
input
user-defined
functions.
The
ground
results
andobtained
materials
the model
include,
of vegetation,
amongpersonal
others,
the
parameters
following:ofDistribution
pedestrians.
ofoutputs:
mean radiant
Distribution
temperature,
of temperature,
radiationrelative
fluxes and
humidity,
thermal
pollutant
comfortconcentration,
indicators (PMV,
SET*
turbulence
and PET).
parameters, wind speed and thermal comfort indicators, at different
heights throughout the urban area of interest.
Open spaces-Tools [2/5]
Special modelling features
Tool
SOLWEIG
Method
UCM
Strengths
Weaknesses
> Modelling of 3D
radiation fluxes
> Velocity pattern
decoupled from
heat transfer
In terms>of
the
Turbulence is
not modeled
completeness of
> Solves for
> Limited
calculated
mean radiant
documentation
temperature
and tutorials
(thermal indicators,
comfort)
prediction
> Average urban
physics
expertise and user
accuracy
is required
friendliness
> Relatively
accurate
geometry
Evaporation and
evapotranspiration
> By-default
models for
Evaporation
Radiation
Short and long
wave radiation
models are
included
Accuracy
Satifying for
weak winds only
CPU time
Medium
Availability
Research-based
> Evapotranspiration is ignored
In terms of whether
they account for
important urban
physics phenomena
related to UHI
Limitations in
accuracy and
computational
time
Availability
CFD/BES coupling for building energy assessment
Heat exchange between indoor and outdoor space reveals that building surrounding
environment influences building energy performance. These influences may be
described as follows:
 The incident solar radiation on building walls, which is affected by the adjacent
obstacles such neighbouring buildings, trees and hills.
 The convective heat flux at the exterior surfaces, which is determined by the
Convective Heat Transfer Coefficient (CHTC) and by temperature difference
between the outdoor air and exterior surfaces.
 The intensity of incoming long wave radiation.
 The heat and moisture transfer through infiltration.
UHI affects building energy performance
CFD/BES coupling for building energy assessment
Findings of past study*
Classic method (farfield climate data)
Novel method (Local
climate data via
CFD/BES)
20% difference!!!
*J. Bouyer et al., Microclimatic coupling as a solution to improve building energy simulation in an urban context, Energy and Buildings 43 (2011) 1549-1559.
Decision making [1/5]
Problem statement
Determination of the optimal blend(s) of retrofit measures that ensure:
- acceptable values of living conditions (thermal comfort and air quality indicators)
- under minimum energy consumption (for buildings)
- minimum costs and
- minimum attenuation periods of investments.
Decision making [2/5]
Recognition of targeted parameters
- Thermal comfort indicators: PMV, PMV(SET*), SET*, PET, etc.
- Air quality indicators: Pollutant concentration, Displacement efficiency
- Energy indicators: Energy demand, Energy consumption, etc.
- Cost indicators: Installation and Operation
- Time indicators (if applicable): Attenuation period
Decision making [3/5]
Determination of desired values of targeted parameters
Which is the desired value of targeted parameter (GOAL)???
E.g.
- Reduction of absolute value of PMV by 15%.
- Pollutant concentration: Within limits based on the pollutant (thresholds can be
found in indoor-health handbooks)
- Pollution displacement efficiency (Ventilation efficiency): <1
- Energy demand: Minimum
- Energy consumption: According to legislation for major retrofits
- Costs and attenuation periods: Minimum
Decision making [4/5]
Recognition of design parameters (Retrofit options)
Once the goals have been specified, the decision maker should focus on the design
parameters, i.e. the ways to achieve the specified goals.
- Buildings: Insulation materials; Windows; Systems for heating, cooling, lighting and
hot water production; etc.
- Open spaces: Ground materials; vegetation species, size and orientation; Water
surfaces size and orientation; other measures such as size and orientation of
pedestrian roads.
Decision making [5/5]
Means to solve the problem
Parametric analysis
OR
Algorithm
Level of use of novel methods-BES
TRNSYS
Level of use in partner Countries and Worldwide
EnergyPlus
Level of use in partner Countries and Worldwide
120 France
4%
Greece
2%
100
Italy
7% Spain
1%
France
13%
Greece
4%
Italy
9%
80
Elsewhere
86%
Elsewhere
71%
60
Spain
3%
40
20
0
Italy
France
Greece
Spain
Croatia
Level of use of novel methods-Field models
ANSYS-Fluent
Level of use in partner Countries and
Worldwide
60
50
France
Greece Italy
5%
2%
7% Spain
3%
40
30
20
Elsewhere
83%
10
0
Italy
France
Greece
Spain
Croatia
Reasons of limited use
 Complexity
 Time consuming
 Requirement for advanced urban and building physics expertise
 Lack of designers’ flexibility and know-how
 Lack of stimulating mechanisms-Prescriptive design indicated by CEN Standards
 As regards urban planning, other than empirical guidelines no regulation exists to
guide designers towards the use of simulation tools in order to estimate
microclimate in open spaces.
Conclusions
•
Current tools used for Compliance are weak as important parameters, such as indooroutdoor effects and energy behaviour are roughly approximated.
•
Current policies are prescriptive in the use of novel methods that will provide a more realistic
NZEBs (No room for design freedom and imagination).
•
Novel methods are not widely used due to prescriptive regulations and to lack of awareness
of today’s engineers.
Conclusions
The REPUBLIC-MED will:
-
Propose applicable and cost-effective improvements in the existing design-forcompliance tools
-
Reveal the impact of important effects being considered as uncertainties
-
Suggest ways to account for climatic and behaviour effects
-
Reveal possibilities in cost-optimal requirements through optimization approaches
-
Get engineers familiarized through training seminars and dissemination activities
-
Influence policy makers
THANK YOU
Dr. George M. Stavrakakis
Chemical Engineer, PhD, MSc
Division of Development Programmes
Centre for Renewable Energy Sources and Saving
(CRES)
Email address: gstavr@cres.gr Postal address: 19th
km, Marathonos Av., GR-19009, Pikermi, Attiki, Greece
Tel.: +30 210 6603372
Fax: +30 210 6603303