IEA HPP Annex 28 Calculation method Workshop IEA HPP Annex 28 8 th International Heat Pump Conference, Las Vegas, 30 May 2005 Carsten Wemhöner, Operating.

IEA HPP Annex 28

Calculation method

Workshop IEA HPP Annex 288th International Heat Pump Conference, Las Vegas, 30 May 2005

Carsten Wemhöner, Operating Agent IEA HPP Annex 28

Institute of Energy, University of Applied Sciences Basel

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Outline of the presentation

Objectives

Extension to combined systems

Simplifications, calculations steps and input data

Principle of the calculation

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Objectives of the calculation method Transparent

no correction factors as far as possible

Easy-to-use “hand calculation”, no extensive computer application or simulation suited for standards

Based on publicly available data standard testing results component characteristics from technical data sheets

Applicable to the majority of systems on the market

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Calculation method – basic situation

Output capacity and efficiency (COP) strongly dependent on source and sink temperature and changes over the operation range

Output capacity and efficiency (COP) are known at defined testing points (from standard component testing)

Meteorological data available for evaluation of the source temperature

Controller settings available for the characterisation of the sink temperature

Annual energy requirement for space heating and domestic hot water are known from standard calculations (building regulations)

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Principle of the calculation method

Annual frequency of the ambient dry bulb air temperature

ambient dry bulb temperature [°C]

Cumulative annual frequency of the ambient dry bulb air temperature

Meteo data processing

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Principle of the calculation method

ambient dry bulb temperature [°C]

Bin distribution

Operation conditions at the operating points valid for the entire bin

Bins should have connection to available information on the heat pump characteristic

Conclusion: Operating point in the centre of the bin

Bin limits between operating points

Design indoor temperature

OP1

OP3

OP2

design outdoortemperature

3, upper

3, lower

Upper ambient temperature for heating

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Performance factor at operating point

Efficiency values from standard testing valid for the whole bin COP interpolated for the conditions at the operating point

Further system losses Storage losses

Additional electrical auxiliary expense heat pump auxiliaries not considered in the COP boundary (e.g. brine source

pump) Circulation pumps Control only in times when heat pumps is not running

PFi = Qnet,i + Qloss,i

COPi

Qnet,i

+ Eaux,i

Qnet,i

COPi

Qnet,i

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Principle of the calculation method

Measure for the energy requirement:Heating degree hours(HDH)

Energy requirement

Heating degree hours=

dt)( aID

Energy requirement in the bin corresponds to difference of cumulative heating degree hours at bin limit

Area of the bin (area between cumulative frequency and indoor design temperature) corresponds to energy requirement

Relative energy requirement in the bin corresponds to ratio of bin areas(weighting factor)

Operation conditions at operating point valid for the entire bin

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ambient dry bulb temperature [°C]

Design indoor temperature

OP1

OP3

OP2

design outdoortemperature

3, upper

3, lower

Upper ambient temperature for heating

ID

a

dt

HP2

HP1

HP3

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Seasonal performance factor of heat pump

Seasonal performance by summation over all bins

Electricity input can be expressed with performance factor SPFhp =

iQnet,i

i PFi

iEi

Ratio between bin heat requirement

and total heat requirement can be

expressed by weighting factor

Qnet1

·Qnet

wiQnet,i

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Principle of the calculation methodBack-up energy

ambient dry bulb temperature [°C]

Design indoor temperature

OP1

OP3

OP2

design outdoortemperature

Upper ambient temperature for heating

HP2

HP1

HP3 Mixed operation mode

heat pump is switched- off at low temperature cut-out

BU

HP1

BUBU

Balance point temperature

Alternate operation modeheat pump is switched- off at balance point

Operation of the back-up heating defined by Operation mode Balance point

temperature Low temperature cut-

out

Parallel operation modeheat pump runs through

low temperature cut-out

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Seasonal performance factor of heating mode

Overall performance of heat pump and back-up heating by weighting with delivered energy fractions

SPFh =Qhp

SPFhp

EhpQhp

+ Qbu

+ Ebu+ Qbu

bu

Qnet

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W3

Principle of the calculation method

ambient dry bulb temperature [°C]

OP2

OP1

Upper ambient temperature for heating

BU

OP3

design outdoortemperature

Balance point temperature

HP

HP

HP

W2

W1

Design indoor temperature

Domestic hot water

Combination of different operation modes by weighting with the respective energy fractions

Approach: Daily tapping profile Hot water energy

dependent on bin time

Back-up energy of domestic hot water mode is determined by temperature level (operation limit heat pump)

Evaluation of heat pump characterstic based on DHW-testing

W4OP4

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Extension to combined systems

Alternate combined operating systems (heat pump switched):

Calculation of space heating and domestic hot water part

Superposition of single operation modes with weighting of energy fractions

Result from testing:characteristic does not change significantly

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Extension to combined systems

Simultaneous combined operating systems (heat extraction):

Characteristic in simultaneous operation changes significantly!

Three operation modes have to be considered: Single space heating (e.g. winter operation, DHW storage entirely loaded) Single domestic hot water (e.g. summer operation) Simultaneous space heating and domestic hot water (SH and DHW demand)

Fraction of operation in each operation mode by evaluating the running time

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Extension to combined systems

Running time t: produced heat/output capacity Maximum running time in combined operation

If tSH > tDHW

=> tcombi = tDHW => DHW operation limiting factor for simultaneous operation

If tDHW > tSH

=> tcombi = tSH => SH operation limiting factor for simultaneous operation

Either space heating (intermediate season) or DHW (winter) could be the limiting factor for combined operation

Maximum value may not be reached due to control effects and not necessarily simultaneous load requirement

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Overall seasonal performance factor

As in the alternate case

the overall seasonal performance of simultaneous operation is calculated

Weighting of the performance factors of the operation modes

SPF =Qh

Qh

SPFh

+ QDHW

SPFDHW

QDHW

SPFcombi

Qcombi++

with the respective energy fraction

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Assumptions/Simplifications

Main impact on space heating is outside temperature

Effects of intermittent heating included in the calculation of energy requirement (EN ISO 13790)

defrosting considered in the heat pump characteristic (e.g. EN 14511)

Domestic hot water requirement constant over the year (daily consumption)

Control effect cannot entirely be described but is reflected by standard situations

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Calculation steps

Determination of energy requirement per bin

Determination of fraction by back-up energy (bivalent operation)

Interpolation of output capacity and COP for source and sink temperature

Correction for part load operation

Evaluation of running time in different operation modes

Calculation of auxiliary energy

Calculation of generator losses (recoverable/recovered)

Calculation of total energy input, system seasonal performance

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Input data

Data of the site Meteorological data (i.e. hourly values of the outside temperature,

irradiation) Source temperature (e.g. outside air, ground, ground water etc.)

Energy Requirements Space heating energy requirement Domestic hot water energy requirement

Heat pump Type of the heat pump (e.g. brine-to-water, outside-air-to-water etc.) Heat pump characteristic (standard testing, e.g. EN 14511, ASHRAE 116 etc.) Operation limits

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Input data

System design Controller settings (heating characteristic curve, upper temperature

limit for heating) Balance point (input or based on design heat load)

System components characteristics Installed storages (heating buffer, domestic hot water) Back-up generators (electrical, fossil) Domestic hot water operation (independent/alternate/combined) Nominal power of auxiliaries (pumps, fans, control…)

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Thank you for your attention!