Energy Efficiency determination, classification & labelling of water chillers

Roundtable on climate & ozone-friendly technologies in refrigeration & air-conditioning =======================================================================

11. May 2011. Belgrade Page 1

ANNUAL MEETING OF THE REGIONAL OZONE NETWORK FOR EUROPE & CENTRAL ASIA

BELGRADE, SERBIA, 10-13 MAY 2011

Energy Efficiency Determination, Classification and Labelling for Water Chillers and Heat Pumps

Dipl.-Ing. Slobodan Pejković Filter Frigo d.o.o.

Serbia – 11050 Belgrade [email protected]

Abstract

Energy efficiency of water chillers and heat pumps is one of the most important disputable issues in the field of HVAC&R. It is disputable due to the fact that neither domestic (Serbian) nor European legislation deals with the problem of energy saving with water chillers and heat pumps with more than 12 kW cooling capacity, even though these units are known to be huge electricity consumers.

By the implementation of the Directive 2002/96/EC on energy efficiency labelling and EN 14511 standard in the European Union, a large step has been made in increasing energy efficiency of air conditioning units and heat pumps with cooling capacity equal to or lower than 12 kW. This Directive does not included equipment of higher cooling capacity, and therefore, in February 2005, EUROVENT (European Association of Air Handling and Refrigeration Equipment Manufacturers) made a classification of such equipment in order to initiate the manufacture of more energy efficient equipment. The aim is to somehow slow down the increase of electricity demands, and thus reduce CO2 emission.

As the implementation of the Kyoto Protocol is a priority issue in Europe and worldwide, the European Union (EU) is planning to reduce CO2 emission by 8% in the period from 2008. to 2012. This is a powerful motive for improving energy efficiency of water chillers and heat pumps. Lower electricity consumption means lower electricity generation demands, which results in reduction of CO2 emission.

This paper deals with water chillers and heat pumps with electrically-driven cooling compressors, and explains how this problem is considered in Europe and worldwide.

Keywords: energy efficiency; coefficient of performance; water chiller; heat pump



Introduction

Change of weather conditions caused by global warming has resulted in significant increase in number of water chillers sold in Europe (Figure 1).

Figure 1: Chillers sales evolution in EU

The figure shows that the biggest increase has been in the number of sold devices with air-cooled condensers, which are also the biggest consumers of electricity in the cooling hardware.

In order to limit increase in electricity consumption with increased number of sold devices, one had to influence increase of energy efficiency, which has been achieved by implementing Directive 2002/96/EC for Devices of Cooling Capacity up to 12 kW.

Figure 2: Evolution of energy efficiency level

Figure 2 shows that this evolution is especially prominent since 2004. for room air conditioners. In the European Union buyers choose devices with high energy efficiency.



Determining and Defining Energy Efficiency Ratio (EER, COP, SEER, HSPF, IPLV, IEER, ESEER, ESCOP) There are several ways of expressing energy efficiency ratios which are defined differently in different parts of the world.

Let’s quote examples from U.S.A. In part 431, paragraph 92 e-CFR (Electronic Code of Federal Regulations) defines:

COP – Coefficient of Performance is a ratio between the total cooling capacity and net absorbed power of electricity consumer, expressed in the in identical units of measurement, and therefore the value is unitless.

COP = Φh / Φw

Where: Φh - total cooling capacity [Btu/h] Φw = 3.412 Pw - equivalent of absorbed power [Btu/h] Pw – absorbed power [W]

EER – Energy Efficiency Ratio is a ratio between the total cooling capacity and net absorbed power of electricity consumer, expressed in Btu/Wh.

EER = Φh / Pw

Where: Φh - total cooling capacity [Btu/h] Pw – absorbed power [W] Ratio between COP and EER is 3.412 and it represents a conversion ratio of Btu/h and W. The American COP and EER represent the same value, only expressed in different units. Besides that, they determine those ratios for cooling or for heating. For example COPcooling means ratio between total cooling capacity and net absorbed power, while COPheating represents a ratio between the produced heating effect of an heat pump and the net absorbed power. The same applies also for EER. This method of presenting seems little confusing for users, and especially for those from Europe, who place different meaning on ratios with the same marks, COP and EER respectively. SEER, HSPF and IPLV have been defined in much clearer, and therefore also in more important way. SEER - Seasonal Energy Efficiency Ratio is used to define the average annual cooling efficiency of an water chiller or heat pump system and represents a ratio between total cooling energy exchanged in the evaporator during the year – seasonal use of water chiller or heat pump in the cooling period, expressed in Btu, in relation to the total absorbed energy used in the same period, expressed in Wh. SEER is an average value of EERcooling during the year, at different external air temperatures, and therefore in different device operating regimes. Bigger SEER value means device with higher energy efficiency. SEER value is always little bigger than EER, for some 0.5 to 1 Btu/Wh.



The term SEER is generally applied to devices with cooling capacity less than 65000 Btu/h (19 kW). The most efficient cooling devices have value of SEER=13.

HSPF - Heating Seasonal Performance Factor is used to signify the seasonal heating efficiency of heat pumps and represents a ratio between heating energy exchanged in the condenser during the annual – seasonal use of heat pump in the heating period, expressed in Btu, in relation to the total absorbed energy used in the same period, expressed in Wh. HSPF is an average value of EERheating

during the year at different external air temperatures, and therefore also in different device operating regimes.

The term HSPF is generally applied to heat pumps of cooling capacity up to 65000 Btu/h (19 kW). The most efficient heat pumps have value of HSPF=10.

IPLV - Integrated Partial Load Value

The term IPLV is used to signify the cooling efficiency related to a typical (hypothetical) season rather than a single rated condition. The IPLV is calculated by determining the weighted average efficiency at part-load capacities specified by an accepted standard. It is also important to note that IPLVs are typically calculated using the same condensing temperature for each part-load condition and IPLVs do not include cycling or load/unload losses. The units of IPLV are not consistent in the literature; therefore, it is important to confirm which units are implied when the term IPLV is used. ASHRAE Standard 90.1 (using ARI reference standards) uses the term IPLV to report seasonal cooling efficiencies for both seasonal COPs (unitless) and seasonal EERs (Btu/Wh), depending on the equipment capacity category. The most chillers manufacturers report seasonal efficiencies for large chillers as IPLV using units of kW/ton (1 cooling ton=3.517 kW).

IPLV = 1 / [kW/ton]

Where:

A = EER at 100% of load C = EER at 50% of load

B = EER at 75% of load D = EER at 25% of load

The term IPLV is generally applied to devices with cooling capacity exceeding 65000 Btu/h (19 kW).

As of January 1, 2010 parametar IPLV was renamed from Integrated Partial Load Value to Integrated Energy Efficiency Ratio (IEER). IPLV will not longer be cited or referenced. IEER – How is determined

IEER is a weighted average of the unit’s efficiency at four load points - 100%, 75%, 50% and 25% of full cooling capacity

IEER = 0.020 • A + 0.617 • B + 0.238 • C + 0.125 • D

Where:

A = EER at 100% net capacity at AHRI standard rating conditions B = EER at 75% net capacity and reduced ambient (81.5ºF for air-cooled) C = EER at 50% net capacity and reduced ambient (68ºF for air-cooled) D = EER at 25% net capacity and reduced ambient (65ºF for air-cooled)



In the same electronic code of U.S. Federal Regulations in part 431, paragraph 97 minimum cooling efficiency levels have been quoted for cooling devices and heat pumps of standard size, produced after January 1st, 1994 but before 30th September 2012. Manufacturers are thus obliged to achieve minimum energy efficiency levels, as quoted in Tables 1 and 2.

That means that the legal regulations have eliminated from use cooling devices with low energy efficiency.

Serbian legislation does not have such regulations.

Table 1. §431.97— Minimum Cooling Efficiency Levels

Product Category Cooling capacity

Sub-category

Efficiency level1

Products manufactured

until October 29,

2003

Products manufactured on and afterOctober 29,

2003

Small Commercial Packaged Air

Conditioning and Heating Equipment

Air Cooled, 3 Phase

<65,000 Btu/h

Split SystemSingle

Package

SEER = 10.0 SEER = 9.7

SEER = 10.0 SEER = 9.7

Water Cooled, Evaporatively

Cooled, and Water-Source

<17,000 Btu/h

AC HP

EER = 9.3 EER = 9.3

EER = 12.1 EER = 11.2

≥65,000 Btu/h and <135,000

Btu/h

AC HP

EER = 10.5 EER = 10.5

EER = 11.5 EER = 12.0

Large Commercial Packaged Air

Conditioning and Heating Equipment

Air Cooled

≥135,000 Btu/h and <240,000

Btu/h

All EER = 8.5 EER = 8.5

Water-Cooled and Evaporatively

Cooled

≥135,000 Btu/h and <240,000

Btu/h

All EER = 9.6 EER = 9.6

1For equipment rated according to the ARI standards, all EER values must be rated at 95°F outdoor dry-bulb temperature for air-cooled products and evaporatively cooled products and at 85°F entering water temperature for water-cooled products. For water-source heat pumps rated according to the ISO standard, EER must be rated at 30°C (86°F) entering water temperature.



Table 2. §431.97—Minimum Heating Efficiency Levels

Product Category Cooling capacity

Sub-category

Efficiency level1 Products

manufactured until

October 29, 2003

Products manufactured on and after

October 29, 2003

Small Commercial

Packaged Air Conditioning and

Heating Equipment

Air Cooled, 3 Phase

<65,000 Btu/h

Split System Single

Package

HSPF = 6.8 HSPF = 6.6

HSPF = 6.8 HSPF = 6.6

Water-Source

<135,000 Btu/h

Split System

and Single Package

COP = 3.8 COP = 4.2

Air Cooled

≥65,000 Btu/h and <135,000

Btu/h

All COP = 3.0 COP = 3.0

Large Commercial

Packaged Air Conditioning and

Heating Equipment

Air Cooled

≥135,000 Btu/h and <240,000

Btu/h

Split System

and Single Package

COP = 2.9 COP = 2.9

Packaged Terminal Heat

Pumps All All All

COP = 1.3 + (0.16 × the applicable minimum cooling EER prescribed in Table 1—Minimum Cooling Efficiency Levels)

COP = 1.3 + (0.16 × the applicable minimum cooling EER prescribed in Table 1—Minimum Cooling Efficiency Levels).

1For units tested by ARI standards, all COP values must be rated at 47°F outdoor dry-bulb temperature for air-cooled products, and at 70°F entering water temperature for water-source heat pumps. For heat pumps tested by the ISO Standard 13256–1, the COP values must be obtained at the rating point with 20°C (68°F) entering water temperature.

Table 3 quotes minimum energy efficiency levels that must be achieved in Hong Kong, according to the „Code of Practice for Energy Efficiency of Air Conditioning Installations“ - 2007.

Table 3. Minimum Cooling Efficiency Levels for Water Chillers COPcooling

Capacity Range [kW]

< 500 500 to 1000 > 1000

Chillers Water Cooled

With scroll compressors

4 4.5 5.2

With screw compressors

4.6 4.6 5.5

Chillers Air Cooled

With scrollcompressors

2.7

With screwcompressors

2.9



Table 4 shows data for EER, COP and IPLV, determined according to ARI standards for devices manufactured in the U.S.A.

Table 4. Technical Data for Water Chillers; Air Cooled

European Union Standards are clearer than the U.S. ones, but they didn’t cover devices with more than 12 kW cooling capacity.

According to the European Standard EN14511-1:2007 (D) EER and COP have been defined in the following way:

EER – Energy Efficiency Ratio (Cooling Efficiency Level) is a ratio between the total cooling capacity and absorbed power of electricity consumer (total power input), expressed in the in identical units of measurement, and therefore the value is unitless.

COP – Coefficient of Performance (Heating Efficiency Level) is a ratio between power of heating exchanged in the condenser in relation to the absorbed power of electricity consumers, expressed in the same measuring units Wat / Wat.

When determining absorbed power all electricity consumers are taken into consideration, as follows: compressor drive engine, electrical panel, fans and pumps necessary for transport of fluids for heat exchange, which must overcome internal resistances during flow of fluids through the heat exchangers.

Testing methods and procedures used for determining energy efficiency have been described in the European standard EN14511-3:2007 (D).



Standard conditions at which testing is performed for determining energy efficiency have been described in the European standard EN14511-2:2007 (D).

EUROVENT as European Committee of Air Handling and Refrigeration Equipment Manufacturers exists for more than 10 years and counts more than 180 manufacturers. In order to support implementation of the Energy Performance Building Directive (EPBD) which requires calculation of building energy performance and regular inspection of central air conditioners and chillers with more than 12 kW cooling capacity, EUROVENT developed a European Seasonal Energy Efficiency Ratio - ESEER (Seasonal Cooling Efficiency Level), index based on ARI approach to determine the Integrated Part Load Value.

This index presents energy efficiency of water chillers in more realistic terms, because time period during the annual operating season in which the chiller works under full load is shorter. Therefore the manufacturers try to develop devices that would be more efficient during reduced load conditions. Chillers with the same cooling index EER, do not need to have the same ESEER. The chiller with bigger ESEER is more energy efficient.

ESEER is a weighed formula enabling to take into account the variation of EER with the load rate and the variation of air or water inlet condenser temperature.

ESEER = 0.03 • A + 0.33 • B + 0.41 • C + 0.23 • D

Where:

A = EER at 100% of load C = EER at 50% of load

B = EER at 75% of load D = EER at 25% of load

In water chillers with air cooled condenser ratios are determined for different load at different air temperatures when entering the condenser. For minimal load (25%) air temperature of 20ºC is adopted, and for maximum (100%) 35ºC temperature.

In water chillers with water cooled condenser ratios are determined for different loads at different water temperatures when entering the condenser. For minimum load (25%) water temperature of 18ºC is adopted, and for maximum (100%) 30ºC temperature.

All those ratios for devices with more than 12 kW cooling capacity do not have the importance of »directive« or of a »standard« and their implementation is on voluntary basis.

As there is no European or ISO standard for part load testing conditions, EUROVENT standard, 6-C003-2006 has been amended including testing procedure for part load conditions. Table 5 shows data for EER and ESEER determined according to EUROVENT rules. Comparison of data from this table and data from Table 4 pertaining to U.S. devices is not purposeful, because they do not pertain to the same working conditions.



In the following conditions: (1) condenser air intake temperature 35°C; chilled water temperature 7°C; temperature differential at the evaporator 5 K. (2) condenser (evaporator) air intake temperature 7°C D.B. - 6°C W.B.-; water temperature 40/45°C. Table 5. Technical Data for Water Chillers; Air Cooled



Table 6. Technical Data for Water Chillers; Freecooling Air Cooled

In the following conditions: (1) condenser air intake temperature 30°C; chilled water temperature 15/10°C - 30% ethylene glycol. (2) Water: 15/10°C – 30% ethylene glycol. Table 6 shows data for EER at a lower air temperature and higher water temperatures. These conditions are not good to compare different devices, but are realistic for water chillers with indirect free cooling.



Figure 3: EXAMPLE OF OUTPUT SOFWARE FOR THE ESTIMATION OF ENERGY SAVING

Figure 3 shows that large savings can be achieved with indirect free cooling in winter working conditions.

NEWS in Seasonal Energy Efficiency EUROVENT is involved in a study for the development of the European Seasonal Coefficient of Performance – ESCOP (Seasonal Heating Efficiency Level).

Some AC engineer proposes a new index of the seasonal energy efficiency for chillers, CSE (Chiller Seasonal Efficiency). This index has an advantage in that it is adaptable to multiple-chiller systems by setting six rating points to consider the difference in the EER due to the entering condenser water temperature as well as the part load.

Using the CSE index, the advantage of a chiller with variable-speed turbo compressors is presented.

Rooftop manufacturers asked the European Committee for Standardization to consider free cooling in the calculation of the seasonal efficiencies in order to represent the energy savings such a system brings along.

VDMA (Verband Deutscher Maschinen und Anlagenbau - German Engineering Federation) was founded the working group “Energy Efficiency of Refrigerating Systems”. This working group is an integration of industry, science, craft, user, associations and politics.

The working group developed basic principles for energy efficient components and systems in refrigerating technology and prepares recommendations for politics and legislation

The working group “Energy Efficiency of Refrigerating Systems” developed a model offering a simple evaluation of the refrigerating load and published it in a “VDMA-Einheitsblatt”. They introduced new coefficients. One of them is - Efficiency of use of cold η ETA(Qo).

EHPA - European Heat Pump Association with its EHPA Norms & Standards Committee considers that COP does not exist in real-life. Ecodesign establishes the Efficiency Factor η (ETA).

It is expected that the results of these activities will be after the year 2012.



Classification of Water Chillers according to Cooling Efficiency Level (in Europe)

EUROVENT established classification for full load Energy Efficiency Ratio of each type of water chillers; see Table 7. Table 7. Chillers Energy Classification in Cooling Mode

Class EER Air Cooled Water Cooled Remote Condenser

A EER ≥ 3.1 EER ≥ 5.05 EER ≥ 3.55 B 2.9 ≤ EER < 3.1 4.65 ≤ EER < 5.05 3.4 ≤ EER < 3.55 C 2.7 ≤ EER < 2.9 4.25 ≤ EER < 4.65 3.25 ≤ EER < 3.4 D 2.5 ≤ EER < 2.7 3.85 ≤ EER < 4.25 3.1 ≤ EER < 3.25 E 2.3 ≤ EER < 2.5 3.45 ≤ EER < 3.85 2.95 ≤ EER < 3.1 F 2.1 ≤ EER < 2.3 3.05 ≤ EER < 3.45 2.8 ≤ EER < 2.95 G < 2.1 < 3.05 < 2.8

Table 7 presents values of EER for chillers with different types of condensers and for different classes. The basic goal of such classification is to eliminate from use chillers of class G, and to stimulate sales of top class ones.

All those ratios for chillers with more than 12 kW cooling capacity do not have the importance of »directive« or of a »standard« and their implementation is on voluntary basis.

Labelling of Water Chillers according to Cooling Efficiency Level (in Europe)

At present, the Energy Labelling Directive is restricted to household appliances. Indeed, the label is mandatory only for Room Air Conditioners with capacity equal to or lower than 12 kW. By applying Directive 2002/96/EC on labelling of devices according to Energy Efficiency, a great move has been made in increasing energy efficiency of air-conditioning devices and heat pumps with capacity equal to or lower than 12 kW.

This Directive prescribes mandatory labelling of energy efficiency class of a device. Method of labelling in the form of defined size sticker with data about energy efficiency class from A to G, enables the buyer to influence the energy saving himself, during selection and purchase of the device.

This method of labelling is not defined by standards or regulations for water chillers and heat pumps with more than 12 kW cooling capacity.



Conclusion

The Energy Performance Building Directive (EPBD) requires calculation of building energy performance and regular inspection of central air conditioners and chillers with more than 12 kW cooling capacity.

However, these measures only address the efficiency of the end-use equipment as determined under standard conditions at full load and will not realize many of the potential energy savings which are related to operating conditions at part load. To be really effective, energy efficiency options have to be defined not on the basis of nominal operating conditions but on a variety of part load conditions, which better reflect the central air conditioners operating modes that occur in real use.

Development of the European Seasonal Coefficient of Performance – ESCOP (Seasonal Heating Efficiency Level) must be finish.

Take in to account free cooling in the calculation of the seasonal efficiencies in order to represent the energy savings such a system brings along.

Consider the advantage of a multiple-chiller systems with variable-speed turbo compressors in the calculation of the energy savings.

As the implementation of the Kyoto Protocol is a priority issue in Europe and worldwide, the European Union is planning to reduce CO2 emission by 8% in the period from 2008. to 2012. This is a powerful motive for improving energy efficiency of water chillers and heat pumps. Lower electricity consumption means lower electricity generation demands, which results in reduction of CO2 emission.

Literature:

1. EN standard 14511: 2007 (D) 2. ARI standard 340/360 – 2007 3. IIR bulletin No. 2001 – 5 4. Energy Labeling Directive, 2002/96/EC and EN 14511 Standard for Room Air Conditioners,

Yamina Saheb, Andre Pierrot, Sulejman Bećirspahić 5. Effect of the Certification on Chillers Energy Efficiency,

Yamina Saheb, Sulejman Bećirspahić, Jerome Simon 6. Air-conditioning, air handling and refrigeration equipment: European-wide certification,

standards and European directives on energy efficiency, Sandrine Marinhas, Sylvain Courtey, Mohamed Ouhemmou, E. Melquiond and G. Robertsson Eurovent certification Company, France

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Energy Efficiency determination, classification & labelling of water chillers

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