54 IKZ-EnErgy 8/9/2015

Energy-Saving Cooling with HeatAir-conditioning and cooling is becoming increasingly important

The cooling of overheated rooms is becoming increasingly important. This frequently only succeeds in existing buildings by using compression chillers with a corresponding energy consumption. A new and interesting alternative is a new absorption chiller. They are much smaller and lighter than those that are currently available in the market, can be retrofitted and with their thermal refrige-ration generation using the non-toxic substance combination of lithium bromide and water, they are more environmentally friendly than previous chillers

The cooling of buildings and rooms is also becoming increasingly important for us in Central Europe. Not only the climate change that brings us hotter summer says and frequent heatwaves in summer, cause us to perspire, but also the modern trans-lucent constructions with large amounts of glass. Especially the technical progress with modern computer centres, telephone systems, server rooms, production halls and much more, increase the internal heat load.

Cooling is therefore becoming increa-singly important – on the one hand for oc-cupational safety reasons and on the other, as a result of the knowledge that air-con-ditioning results in increased produc- tivity. The cooling and air-conditioning of rooms makes a substantial contribution to the physical comfort of people – whether at home, at work, in hospitals, hotels, a con-ference room, everywhere in everyday life.

Cooling requirement in germanyGermany has a a lot of catching up to

do when it comes to cooling, when compa-red with other countries. This is because in the past, natural ventilation with cool outside air, especially during cool nights, sufficed for the cooling of a building for a long time. The changes stated above, espe-cially the higher internal loads resulting from technical building equipment, the fa-cade design and the occupation density in modern buildings, have resulted however in this no longer sufficing. In a study com-missioned by the German Federal Envi-ronmental Agency, it was estimated that the cooling requirement shall increase by 25 % for residential buildings and by 50 % for non-residential buildings over the next 20  years, whereby the cooling require-ment for non-residential buildings shall be around 100 times higher than for resi-dential buildings. Therefore, a considera-ble increase in CO2 emissions is also to be attributed to the cooling of buildings in the

future, should the chilling systems that are available in the market not change.

Energy savings when coolingIn order to achieve the reduction in CO2

emissions that is being aimed at, more and more attention is to be paid to energy sa-ving. It is a known fact that compression chillers that account for the largest share of chillers, consume enormous amounts of power and that mainly at peak load times. Neither is this environmentally friendly, nor is it inexpensive.

This is why absorption chillers are a very good alternative. They consume a ne-gligible amount of power, can be operated using a refrigerant that does not contain CO2 (water), and produce cold on a heat ba-sis. The favourites here are machines that can be operated using excess heat. This is especially interesting in summer, when there is excessive heat from waste combu-stion plants and CHP units, in addition to

district heating and solar heat, but this is not required. Existing cogeneration capaci-ties can be put to better use and the power plants can be operated more profitably as long as purchasers of the resulting heat can be found. Excess heat that exists through- out the year, known as process heat, the utilisation of which can be of special in-terest to industrial companies does not have an excessive temperature, however. Chilling systems that can use the heat at a low temperature level, are therefore es-pecially in demand. Such a machine is the new absorption chiller from the company Baelz. In this, the cold is generated by the non-toxic substance combination of lithi-um bromide and water. The problem of the gaseous refrigerant in compression chillers that is damaging to the health and the en-vironment is no longer a problem. Another advantage of the absorption chiller is that they differ from compression chillers, in that they practically run silently.

Die Absorptionskälteanlagen „Biene“ und „Hummel“.

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Developmental goals of the new absorption chiller

The manufacturing and further deve-lopment of the “BS Nova“ absorption chil-ler (sold through the company Baelz) in close cooperation with the Technical Uni-versity (TU) Berlin, that in cooperation with the AGFW, (Energieeffizienzverband für Wärme, Kälte und KWK e.V.) energy efficiency association for heating, cooling and CHPs), the BTGA (Bundesindustriever-band Technische Gebäudeausrüstung e.V.) federal industrial association for building equipment and the TU Dresden, together with the ZAE Bayern (Bayerisches Zentrum für angewandte Energieforschung) Bava-rian Centre for applied energy research, the systems were installed in 15 instal-lations throughout Germany during a demonstration project, commencing with the conception of a chiller for an average power requirement of approx. 50 kW and a slightly larger one with around 160 kW. The system was to be as small as possi-ble, so that it is suitable for retrofitting in an existing building. The weight and door passability of the system was also to be taken into account. This average power range almost did not exist on the market in the past.

The new systemThe result is a compact system with a

comparatively low weight (Chart 1), that does not cause any difficulties during transportation. The substantially small amount of refrigerant and solvents in com-parison to other chillers, reduces not only the weight, but also the costs. The system is available in two different sizes, the “bee” and the “bumble-bee”. The names refer to the colour and the different sizes. The par-tially modular design provides for a power range of approx. 50 – 320 kW due to the new development of the absorption chiller with 50 or 160 kW. The concept of expan-ding the “Bee” and “Bumble-bee” concept with a 500 kW system (“Hornet”), is cur-rently being looked into.

results of the research phase25 systems are being subjected to

field tests over a period of many years. They shall be observed exactly and the results shall be recorded. It has been shown that when using absorption chillers in district heating networks, strongly varying volume flows are to be taken into account within a temperature range of 55°C – 100°C. The modern absorption chillers are able to utilise

these very different requirements. A very beneficial property of the new absorpti-on chillers is their load-dependent opera-tion both under the most diverse tempera-tures and the most diverse volume flows. A reduction to the volume flow can be bene-ficial for the return flow temperature in the distance heating network. The tempe-rature differences in the drive circuit of “bee“ and “bumble-bee“ can be selected large and cold water temperatures of max. 5°C can be achieved. The cooling per-formance in proportion to the consumed energy (COP) resulted in very good values of up to 0.8 in the field test.

When integrating “bee” and “bumble-bee” in existing network structures, but es-pecially when carrying out renewal work and in new constructions, the chillers not only serve as an air-conditioning system, but they can also serve as a heat pump, whereby they can make useful heat of up to 60°C available.

The recooling temperatures that were previously subjected to an upper limit of 35°C – 40°C in this technology, can be increased to approx. 50°C by reducing thermal bridges and optimising the heat exchangers. This in turn, enables dry

recooling plants, which is a considerable advantage when compared with the pre-vious chillers: • comparatively lower power range of 50

or 160 kW respectively, • thermal process efficiency, COP of 0.8, • high drive temperature difference of

>40 K, • or low drive temperatures starting at

55°C are possible, • process design for a dry recooling, • use as a heat pump for heating systems

up to 60°C, • fast reaction, 25% to 100% power

<10 minutes, • door passability, <0.86 m x 1.52 m x

1.9 m (bee), • efficient system regulation for min. ope-

rating/energy costs.

Installation in the practiceA current example of the use of a Baelz

absorption chiller is its use by the Stadt-werke public utilities company in Gießen. A system with an average power range is required here, whereas those that are stan-dard in the market have a range of between 300 and 500 kW, they being correspon- dingly large and heavy. It would not have

Maßzeichnungen der größeren AKA „Hummel“.

56 IKZ-EnErgy 8/9/2015

been possible to integrate them in the existing building placed heavy demands on the recooling and were also too expensive. There had not been any suitable chillers in the market, merely from foreign suppliers, with whom one had not made any good experience in Gießen however.

The Stadtwerke Gießen opted for the Baelz absorption chiller as a result of its relative small size and the diverse technical bene-fits of this chiller (charts 2 and 3). It can for example, be driven at especially low hot water tempe-ratures. The Stadtwerke needed a new chiller for an office buil-ding, two computer centres and a telephone system. The previous cooling with drinking water over plate heat exchanges no longer sufficed. A total of 68 kW were to be cooled. In order to ensure an adequate capacity for peak loads, they opted for a “bumble-bee“ that can also provide power of between 75 and 100 kW. This means that more than a quar-ter of the capacity exists as a re-serve for peak loads. Another in-teresting factor in addition to the low power range, was the very good COP factor of 0.73, that none of the other systems was able to achieve (partial load at approx. 30%). The heat that was generated by the CHPs and was then used to drive the absorption chiller, is provided by the district heating network. The hot water inlet and outlet normally has a tempera-ture of 80°C/60°C. A dry recoo-ler cools the residual heat from the absorption chiller in summer and in winter, it cools the corre-sponding rooms after the absorp-tion chiller has been deactivated. In winter, the outside air is cooled using a plate heat exchanger. An additional important aspect that speaks for the Baelz absorption chiller is its rapid reaction time. In the event of a sudden tempe-rature increase occurring, the chiller is able to reach between 25% and 100% of its power in less than 10 minutes. This means that an increase in the room tempe-rature, when the sun is shining

through a south-facing window, can be cooled down again in the shortest amount of time.

Increased comfort and health protection

The thermal cooling generation using absorption chillers serves our comfort and to protect our health, and that with techno-logy that is more environmentally friend-ly and with a greater energetic efficiency. The utilisation of excess heat of a medium temperature that often occurs in summer, results in heat from renewable energies sources such as solar heat, being utilisa-ble during this period. The purchasing of district heating in the summer contributes to a much more economical operation of po-wer stations when it comes to generating power. With their comparatively low po-wer range and low weight, the bee and the bumble-bee can be integrated in existing buildings. It is also possible to transport the cool air into the corresponding rooms by means of existing heat distribution sys-tems and the absorption chiller can also run as a heat pump. The fact that the ab-sorption chillers from Baelz can be run at temperatures as low as 55°C, makes them especially interesting.

When compared with compression chil-lers, that consume high amounts of electri-cal energy, resulting in them being an addi-tional CO2 load in summer, the absorption chillers require only a negligible amount of electricity. This prevents a further sprea-ding of the compression chillers. ■

KOnTAKT

W. Bälz & Sohn GmbH & Co.74076 HeilbronnTel. 07131 15000Fax 07131 150021mail@baelz.dewww.baelz.de

Tabelle 1: Dimensionen von „Biene“ und „Hummel“.

Tabelle 3: Nennbetriebsdaten der „Hummel“.

Biene HummelLänge [m] 1,75 1,95

Breite [m] 0,68 0,86

Höhe [m] 1,59 2,05

Transportgewicht leer [t] 0,65 1,75

Tabelle 2: Technische Daten der „Hummel“.

Nennbetriebsdaten Einheit WertKälteleistung kW 160

Heizleistung kW 219

Wärmeabfuhr kW 394

COP   0,8

Kaltwasser

 Eintrittstemperatur 0 C  21

 Austrittstemperatur 0 C  16

 Volumenstrom m³/h  27,7

 Druckverlust bar   0,27

 Max. Druck bar   6

Warmwasser

 Eintrittstemperatur 0 C  90

 Austrittstemperatur 0 C  72

 Volumenstrom m³/h   9,7

 Druckverlust bar   0,36

 Max. Druck bar  16

Kühlwasser

 Eintrittstemperatur 0 C  30

 Austrittstemperatur 0 C  38

 Volumenstrom m³/h  46,1

 Druckverlust bar   0,34

 Max. Druck bar   6

Technische Daten Einheit WertLänge m    1,95

Breite m    0,86

Höhe m    2,05

Transportgewicht kg 1750

Füllung

 Lösung @54 % kg  120

 Wasser kg   40

Betriebsgewicht kg 1910

Elektrische Anschlüsse

 Spannung/Frequenz V/Hz 230/50

 Leistungsaufnahme w Max. 300