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Federation of European Heating, Ventilation and Air-conditioning Associations
Revision of REHVA nZEB
technical definition for nearly
zero energy buildings
Jarek Kurnitski Professor, Vice-president REHVA
Tallinn University of Technology
REHVA Technical Seminar, Buildings and HVAC-Products
Related EU Regulations, October 18, 2012 Brussels
Federation of European Heating, Ventilation and Air-conditioning Associations
Background
• EPBD recast (2010/31/EU) launched nZEB target in 2010 with the need
for the Member States to define what nZEB for them exactly constitutes
• REHVA realized the problem that various definition of nZEB may cause
in Europe
• CEN EPBD standards published 2007/2008 do not include nZEB and
have system boundary definitions with national decision options – which
depending on the choice, may lead to conflict with EPBD recast for on-
site renewable energy utilization
• In this situation, REHVA nZEB definition/energy calculation system
boundaries launched in May 2011 were widely utilized and affected the
preparation of national definitions, codes and calculation methods in
many countries as only available methodology
• REHVA definition has been popular: at the time the revision was decided
in 4/2012 it was viewed 1070 times and was downloaded 409 times
Federation of European Heating, Ventilation and Air-conditioning Associations
Simplified system boundary with major
energy flows – illustrative changes
For thermal and electrical energy it applies: Delivered – exported energy = energy use – on site renewable
net
i
iiidel
A
fEE
E
exp,,
net
i
ii
i
idelidel
A
fEfE
E
exp,exp,,,
Total energy useof the building
Delivered energy
Exported energy
Building site = system boundary of delivered and exported energy
System boundary of building technical systems
(simplified primary
energy equation is
deleted)
Federation of European Heating, Ventilation and Air-conditioning Associations
EPBD recast – Nearly zero energy
buildings nZEB
• In the directive ‘nearly zero-energy building’ means a building that has a very high energy performance. The nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced on-site or nearby.
nZEB = very high energy performance + on-site renewables
• Definition of “a very high energy performance“ and “significant extent of renewables” let for Member States
Federation of European Heating, Ventilation and Air-conditioning Associations
Most difficult decisions in the
preparation of REHVA definition in 2011
• On site renewable energy is inside the system boundary, i.e. is
directly subtracted from energy use (is not treated as delivered
energy – the option of EN 15603:2008)
– This is confirmed in the EC’s Cost-optimal regulations (No 244/2012).
Quote: “the RES-based active technologies enter into direct
competition with demand-side solutions, which is in line with the
purpose and intention of the cost optimal calculation to identify the
solution that represents the least global costs without discriminating
against or favouring a certain technology.”
• Primary energy factors are by the definition of the system
boundary non-renewable primary energy factors
– EC’s Cost-optimal regulations requires the use of non-renewable
primary energy in the cost optimality assessment
– (in reality, factors for renewable fuels often in between of the total and
non-renewable, and energy policy has an effect)
Federation of European Heating, Ventilation and Air-conditioning Associations
Detailed system boundary – illustrative changes
BUILDING
NEEDSHeatingCooling
VentilationDHW
LightingAppliances
Building site boundary = system boundary of delivered and exported energy
Heating energy
Cooling energy
Electricity for
lighting
Fuels
ENERGY
USE
BUILDING
TECHNICAL SYSTEMS
Energy use and production
System losses
and conversions
Electricity
ON SITE RENEWABLE
ENERGY W/O FUELS
District heat
District cooling
Electricity
Solar gains/
loads
Heat
transmission
ENERGY NEED
DELIVERED
ENERGY
EXPORTED
ENERGY
(renewable and
non-renewable)
Electricity for
appliances
Internal heat
gains/loads
RE generators
He
atin
g e
n.
Ele
ctr
icity
Co
olin
g e
n.
Energy use SB
Cooling en.
Heating en.Energy need SB
• System boundaries (SB) for energy need, energy use and delivered and exported energy calculation. The last one may be interpreted as the building site boundary.
• Demand reduction measures can be distinguished from RE solutions in the energy use SB, not in the delivered/exported energy SB
Federation of European Heating, Ventilation and Air-conditioning Associations
Reasons for the revision
• EC’s Cost-optimal regulation (EU No 244/2012), January 2012, confirmed
the principles used in Rehva delivered/exported/primary energy
calculation frame, but RES (renewable energy contribution) calculation
was not included in the REHVA definition/system boundary
• RES was strongly needed, because it can be easily mixed with
delivered/exported energy calculation
• EPBD standards will be revised – coordination with CEN project-team –
as only available methodology with calculation examples REHVA
document is also important input to CEN
• Many countries work with national definitions – the cost optimal regulation
provided extra reporting time by March 2013
• Cost optimal calculations include nZEB performance levels – detailed
technical definitions needed
• The EPBD laws and regulations shall be adopted and published in MS by
9 July 2012 and most of requirements shall apply from 9 January 2013,
but preparation of fully nZEB compliant regulation is longer process
Federation of European Heating, Ventilation and Air-conditioning Associations
Some major revisions of the Draft
v3 (Sept 05, 2012) • RER – renewable energy ratio equation included
• time step issue (to be able to calculate exported energy)
addressed in page 9
• additional CO2 indicator added, Eq. 4
• ≤ 0 added to ZEB definition with explanation of “net” and
reference to Sartori, page 11
• improved wording for nZEB definition, page 11
• explanation of renewable energy nearby, page 17
• sites with multiple buildings, Figure 5
• explanation of heat pump equations, Figure 7
• new chapter on load matching and grid interactions, Ch. 4.4
• comments on emission/distribution losses in examples, Ch. 5
Federation of European Heating, Ventilation and Air-conditioning Associations
REHVA nZEB definition (improved wording, no major changes)
net zero energy building (ZEB) Energy use of ≤ 0 kWh/(m2 a) primary energy.
NOTE A net ZEB is typically a grid connected building with very high energy performance. A net ZEB balances its
primary energy use so that the primary energy feed-in to the grid or other energy network equals to the primary energy
delivered to ZEB from energy networks. Annual balance of 0 kWh/(m2 a) primary energy use typically leads to the
situation where significant amount of the on-site energy generation will be exchanged with the grid.
nearly zero energy building (nZEB) Technically and reasonably achievable national energy use of > 0 kWh/(m2 a)
primary energy, achieved with a combination of best practice energy efficiency
measures and renewable energy technologies which may or may not be cost
optimal.
NOTE 1 ‘reasonably achievable’ means by comparison with national energy use benchmarks appropriate to the
activities served by the building, or any other metric that is deemed appropriate by each EU Member State.
NOTE 2. Renewable energy technologies needed in nearly zero energy buildings may or may not be cost-effective,
depending on available national financial incentives.
ZEB has exact performance
level of ≤ 0 kWh/(m2 a)
primary energy use
nZEB depends on national
conditions
Federation of European Heating, Ventilation and Air-conditioning Associations
Example of nZEB office – primary energy
• Electricity use of cooling, ventilation, lighting and appliances is 39.8 kWh/(m2 a)
• Solar electricity of 15.0 kWh/(m2 a) reduces the net delivered electricity to 24.8 kWh/(m2 a)
• Net delivered fuel energy (caloric value) is 4.2 kWh/(m2 a) and primary energy is 66 kWh/(m2 a)
3.8 heating
11.9 cooling
10.0 lighting
BUILDING TECHNICAL SYSTEMS
15.0 PV electricity,from which 6.0 used in the building and 9.0 exported
Fuel 4.2
Electricity 33.8
Solar and internal heat gains/loads
Heat exchange through the building envelope
NET ENERGY NEED (47.2 kWh/(m2 a))
DELIVERED ENERGYBoiler3.8/0.9 = 4.2
Free cooling 4.0/10 = 0.4 Compressor cooling 7.9/3.5 = 2.3
Lighting 10.0
Ventilation 5.6
Appliances 21.5
Primary energy: 4.2*1.0 + (33.8-9.0)*2.5 = 66 kWh/(m2 a)
EXPORTED ENERGY
System boundary of net delivered energy
Ne
t de
live
red
en
erg
y
Electricity 9.0
21.5 appliances
(Sum of electricity 39.8)
21,5
10
3,2
0,61,1
10,8
NET ENERGY NEED (47.2 kWh/(m2 a))
Appliances (users')Lighting
Space
heatingHeating of air in AHUCooling in room unitsCooling of air in AHU
Federation of European Heating, Ventilation and Air-conditioning Associations
New: RER system boundary
Heating energy
Cooling energy
Fuels
RENEWABLE
ENERGY USE
BUILDING
TECHNICAL SYSTEMS
Energy use and production
System losses
and conversions
Electricity
ON SITE RE SOURCES
District heat
District cooling
Electricity
DELIVERED ENERGY (renewable and non-renewable)
EXPORTED ENERGY (renewable and non-renewable)
RE generators
(solar, wind, hydro)
He
atin
g e
n.
Ele
ctr
icity
Co
olin
g e
n.
RE energy use SB
Cooling en.
Heating en.
RE generators
(geo- , aero- and hydrothermal)
ON SITE RE SOURCES
New element
in the system
boundary
• Thermal energy from ambient heat exchangers to be accounted (in the
delivered/exported energy calculation calculated with COP)
Federation of European Heating, Ventilation and Air-conditioning Associations
New: RER Equation (not weighted energy)
expexp
exp
NRECNRECRECRECREC
RECRECRECRER
siteoffsiteon
siteoffsiteon
where
RER is the renewable energy ratio, -; RECon-site is the collection of the renewable energy carriers produced on-site, kWh/a; RECexp is the collection of the renewable energy carriers produced on-site and exported, kWh/a; RECoff-site is the collection of the delivered (imported) renewable energy carriers produced off-site, kWh/a; NREC is the collection of the delivered (imported) non-renewable energy carriers, kWh/a; NRECexp is the collection of the exported non-renewable energy carriers, kWh/a.
Federation of European Heating, Ventilation and Air-conditioning Associations
RER example: Figure 9 in the working document
• Discussion on the RECexp term, 9.0 in the figure – should or
should not subtracted? (Not subtracted in the CEN proposal)
4.0 aerothermal
BUILDING TECHNICAL SYSTEMS
15.0 PV electricity,from which 6.0 is used in the
building and 9.0 exported
Fuel 4.2
Electricity 33.8
(20% renewable)
SOLAR ENERGY
DELIVERED ENERGYBoiler3.8/0.9 = 4.2
Free cooling 4.0/10 = 0.4 Compressor cooling 7.9/3.5 = 2.3
Lighting 10.0
Ventilation 5.6
Appliances 21.5 EXPORTED ENERGY
Electricity 9.0
(Sum of electricity 39.8)
Solar panels
System boundary of renewable energy
Condenser(air cooled liquid chiller)
AEROTHERMAL ENERGY
Renewable energy ratio:
35,08.338.02.48.332.00.90.40.15
8.332.00.90.40.15
RER
Federation of European Heating, Ventilation and Air-conditioning Associations
New: system boundary for multiple buildings
Building site boundary = system boundary of delivered and exported energy
Fuels
Electricity
District heat
District cooling
Electricity
DELIVERED
ENERGY
EXPORTED
ENERGY
(renewable and
non-renewable)
Building 1
Cooling en.
Heating en.
Building 2
Building n
SITE ENERGY
CENTRE
Federation of European Heating, Ventilation and Air-conditioning Associations
Coordination with CEN
• CEN has started the preparation of 2nd generation of CEN-
EPBD standards (CEN mandate M/480)
• CEN comments prepared by CTL collective team leaders group
working in parallel on the same subjects
• 2-way information exchange – REHVA document utilized in the
preparation of EPBD Overarching Standard
• CEN has utilized and further developed the RER – assessment
boundary for renewable energy contribution calculation
• In the CEN proposal, primary energy factors are included in the
RER equation (REHVA draft v3 operates with not weighted
energy flows)
• CEN also provided improved wording for clear distinction
between on-site, nearby and off-site, as well as the use of CEN
symbols and some other specific comments
Federation of European Heating, Ventilation and Air-conditioning Associations
Next steps
• Final draft v4 will be prepared for REHVA TF approval
procedure
• Final draft will be available in December 2012 – roughly the
same schedule as for CEN EPBD Overarching Standard
• Will include the summary of available nZEB and low energy
definitions in MS
• To be published in February 2013
Federation of European Heating, Ventilation and Air-conditioning Associations
nZEB case studies • nZEB office buildings in France, Netherlands, Switzerland and Finland
reported according to REHVA definition (and can be compared), see REHVA Journal (3/2011 and 2/2012)
Federation of European Heating, Ventilation and Air-conditioning Associations
• Is intended to help the experts in the Member States in defining the
nearly zero energy buildings in a uniform way – so that local
conditions are taken into account, but the uniform methodology used
• Can be seen as a proposal for uniformed national implementation of
EPBD
• Proposes a technical definition for nZEB buildings following EPBD
recast and Cost-optimal regulation
• Provides energy calculation framework and system boundaries
associated with the definition to specify which energy flows in which
way are taken into account
The original objective of REHVA nZEB
definition does not need revision