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Energy savings in building air-conditioning systems

Highly-efficient energy recovery system EcoCond+ thanks to the use of reversible heat pump technology

The challenge when it comes to sustainability:

Modern architecture is increasingly influenced by the central theme of sustainability. Organisations, such as the U.S. Green Building Council in America or the Deutsche Gesellschaft für Nachhaltiges Bauen (German association for sustainable building), are developing new standards for the building life cycle.

Increasing requirements for thermal insulation and the airtightness of building shells change the room climate conditions in buildings as well. Before this background, air handling systems with energy recovery (WRG systems) are becoming increasingly important, in particular when it comes to a reduction of the energy needs for building air-conditioning.

Apart from the specified minimum values by the regulations and standards, the selection and planning of a suitable energy recovery system also depends on the space potential for its installation. For air handling systems with spatially separated inlet/exhaust air systems, the run-around coil system (KVS) is often used due to the lack of alternatives, for example. This energy recovery system transfers sensible amounts of heat indirectly between the inlet and exhaust air flows with the aid of a hydraulic pump system.

The double heat transfer results in heat losses within the system. The heat transfer efficiency in a standard run-around coil system is only < 60% as an average, for example. In the past, an optimisation of the heat transfer efficiency up to 75% as a maximum (so-called high-efficiency run-around coil systems) based on larger heat transfer areas in combination with an increase of the mass flow rate in the pump system.

However, the optimisation potentials of this principle are limited because the overall energy efficiency of the air handling system cannot be further increased. The reason for this is an increase of pressure losses that affect to a large extent the power consumption of the pumps in the energy recovery system.

The intial situation:

For a further optimisation of room climate and energy efficiency, it is inevitable that even more efficient energy recovery systems will be developed. However, their use may not be considered isolated, but rather always as an overall system with the air handling installation.

Based on the experience gathered, BerlinerLuft. Klimatechnik GmbH has developed an energy recovery system with optimised total energy efficiency and improved heat transfer efficiency resulting in a permanent reduction of the primary energy needs of an air handling system.

The solution:

The new EcoCond+ energy recovery system is based on the general principle of a run-around coil system combined with a reversible heat pump integrated in the hydraulic pump circuit. This system equipment includes a highly efficient refrigerant compressor unit (COP ~ 5), an electronically controlled expansion valve and two plate-type heat exchangers that extract heat from the pump circuit (cooling) or add heat to it (heating) depending on the operating mode of the air handling system. This additionally generated heat input or heat extraction by the heat pump causes an increase of the temperature difference on the multi-leaf heat exchangers in the air flow. This increases the heat transfer efficiency while the mass flow rate in the pump circuit and the heat transfer area remain unchanged.

Conclusion: EcoCond+ sustainably increases the heat transfer efficiency by up to 85% (depending on the outside temperature) without being compelled to increase the pressure loss in the energy recovery system.

The sustainable strengths:

At an outside temperature of -12°C, the new EcoCond+ system increases the heat transfer efficiency by up to 31% compared to a conventional high-efficiency run-around coil system (H-KVS). In spite of the additional energy needed to drive the heat pump equipment, the primary energy consumption is also reduced and the operating costs of the air handling system can be cut by 35%. That is why the energy recovery system (WRG) will pay for itself already after approx. 1.5 years.

What is unique is: Unlike all other energy recovery systems, the heat transfer efficiency of the EcoCond+ increases with rising outside temperatures.

Further strengths:

  •  Eco-friendly and resource saving equipment
  • Reduction of generation systems for inlet air after-treatment (heating, cooling) and thereby the reduction of supply systems for pumped warm and cold water.
  • Energy recovery unit as a compact and space-saving system including all hydraulic and refrigeration components and measuring & control equipment, ready for connection to the air handling system

The developers:

Enrico Stieler, Measuring & control and software development

Dipl.Ing (BA) Stefan Neupetsch, Engineering and project processing

Brief company profile:

Name: BerlinerLuft. Klimatechnik GmbH -  ein Unternehmen der BerlinerLuft. Unternehmensgruppe
Hauptsitz: Bexbach
Gründungsjahr: 2001
Mitarbeiter: 86l
Lösungen:  Lüftungs- und Klimazentralgeräte, Luftreinhaltungstechnik, Hygiene- und Kompaktklimageräte, Geräte mit integrierter Kälte- MSR Technik
Internationalität:  Deutschland, Austria, Polen, Brasilien, Mexico