Chiller efficiency case study

This chiller case study demonstrates that Energyst chillers and application design give energy efficiencies that are much better than theoretical figures often used.

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Content

• Introduction 
• Efficiency Ratios 
• Project Research Scope 
• Test Methodology Test Results
• Test reliability 
• Conclusion 
• Is this an oppertunity for you? 

Introduction

Energy efficiency for liquid chillers is key to the Total Cost of Ownership (TCO). Energy efficiency ratios are often used and unfortunately sometimes misused to evaluate and compare different chiller types and chiller manufacturers. The use of theoretical benchmarks need to be chosen carefully as there are many different industrial standards and in fact chiller performance varies at different operating conditions and real process circumstances.  Energyst design and build chillers to meet the lowest TCO under a wide range of operating conditions.

This chiller case study demonstrates that Energyst chillers and application design give energy efficiencies that are much better than theoretical figures often used.

Efficiency ratios

The most common European efficiency ratios for commercial and industrial branches are the Energy Efficiency Ration and the European Seasonal Energy Efficiency ration:

• Energy Efficiency ratio (EER)
  • Ratio of the cooling capacity to the total power input of the chiller (excl. liquid pump), under specified conditions by an independent institute like Eurovent.
  • The EER specified conditions do not often reflect real process conditions. During a longer period of time the actual operating conditions fluctuate.
  • Also generally known as Coefficient Of Performance (COP) 
• European Seasonal Energy Efficiency Ratio (ESEER)
  • Ratio that is a specified weighted formula taking into account the possible variations of EER with the (part) load rate and the variations of ambient air and liquid outlet temperatures.
  • Energyst’s opinion is that the ESEER ratio is the most realistic theoretical measure of energy efficiency.

Project research scope

Partnership means trust, honesty, integrity and transparency in relationship and in total cost of ownership (TCO) when it comes down to energy efficiency. Our approach on this project was to openly demonstrate actual energy efficiency to our customer.

• 3x EC750 chillers parallel connected to chilled water circuit customer. Equal flow rate over each chiller is provided by customer (internal pump not operational and in by-pass).
• Total required maximum cool load: 2 MW @ LWT +5°C and + 30°C ambient
• Production chilled water for batch process, improving product quality and increasing production volumes
• Project period: 14 months (March 2008 – May 2009)

Test methodology

During a fixed period of time in summer each identical chiller is monitored (24/7) and data logged with external power analyzer and standard monitoring system on chillers. Parameters:

• Fixed and equal flow for each chiller
• Chilled fluid specified (specific heat / density)
• Inlet temperature and outlet temperature per chiller
• Total power (kW) consumption per chiller (excl. internal pump)
• Chillers were maintained by Energyst technicians in optimal condition, including refrigerant circuit and clean condensers.

Test results

All monitored data was analyzed and EER calculations were made. To come to a realistic outcome, only the results during the hottest period during the day (11.00-19.00hr) were used with following results:

• Cool load per chiller varies between 485 kW and 899 kW
• Power consumption per chiller varies between 135 kW and 260 kW
• Average EER of 3.37 versus theoretical peak load EER of 2.76
• 22% improvement against theoretical value.

Test reliability

To ensure reliability we defined parameters as described above. Also a sufficient amount of measurements were taken which makes it possible to use the generally recognised Gauss-method:

• Measured data was analyzed conform the Gauss-method by our independent customer process specialist
• The lower average was proven statistically accurate

Conclusion

Understanding how chillers interact and work together in a process application is critical:

• Chillers rarely operate at full load for long periods in time
• In operation the Energyst EC750 has proven more efficient than theoretical figures.
• The design of the Energyst EC750 is adapted to give high efficiencies throughout the operating range.
• Energyst high efficiency design has been adapted to the full range of high performance chillers (EC500 – EC1000)

Thoroughly understanding a cooling application and the many factors contributing to chiller efficiency are key factors in engineering the best solution for a given application against the lowest TCO. Energyst technicians involved in designing, specifying and maintaining temperature control solutions ensure the most energy efficient operation of chillers.To compare chiller energy efficiencies in use the most realistic standard is ESEER by which the Energyst EC750 chiller demonstrates top quartile efficiency.

Is this an opportunity for you?

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