Comment: How to save energy in buildings?

Gary Walton, chairman of JPW Group, explains how energy was saved in a 27-storey building in Dubai

Gary Walton, chairman of JPW Group.
Vlad Barinov
Gary Walton, chairman of JPW Group.

The use of energy and cost is as always at the forefront of every building operator’s mind. 
The starting point of reducing energy usage does not necessarily require the investment of many millions of dirhams.  Payback can be less than two years, which is a period that most building owners and operators would find acceptable.
JPW Group completed work in January 2018 on a 27-storey tower building in Dubai Media City. 
The energy bills, to date, have reduced from 19% in January to 27% in June. This is a comparison against the last four years of average DEWA bills.  To date, the impact of the works has resulted in an electrical saving of 760,000kWhs.
This was achieved by re-commissioning the MEP systems and BMS to operate in a controlled manner, as they were originally designed.
This meant replacing an AHU that had come to the end of its service life, frame leaking air, unit leaking water, and heat wheel that has catastrophically failed.  The replacement has been designed to provide air volumes compliant with the current codes and standards, and has the capability to provide variable air volumes to maintain CO2 levels to comply with the Dubai design codes.
The unit also has new technology fans with EC (DC) motors, which are up to 30% more efficient that conventional motor drives; these are also inherently speed controllable which assists with volume control. These fans, although more expensive to purchase, have been sealed for life bearings, have no belts that are maintenance free and are more efficient, as mentioned above.
Chilled water pumps are now accurately controlled and the number of operational chillers are always at a minimum speed to provide the level of cooling required.
Many of the technologies mentioned above are still not being included in the design of many buildings today. The calibration of temperature and humidity sensors is also crucial to the control of the systems.
The works included systems for heat (cool) reclaim and the ability to provide heating for humidity control without using high cost direct electric heating.
The payback period for these works are calculated at 16 months. The savings to date has been impressive, from 19% to 26% in less than the previous four years electricity bills; directly comparing this average to this year.
Lighting and lifts were not modified within the scope of the works, and the cost savings for the operation of the air conditioning system is almost 45%.
The basis of these works has been an understanding of the requirements of the system that make up the air conditioning system.
Aside from the replacement of the AHU, the other works included:
• Re-commissioning of the chilled water system and its flows and control pressure.
• Re-commissioning of the fresh air supply system and its distribution to the building.
• Commissioning of the chilled water primary and secondary pumps and the speed control, based on system pressure, control valve operation and required flow rates.
• Control of the operation of the chillers and commissioning of the sequence control.
• Setting back of night time operation of the chillers and pumps.
• Commissioning of the AHU heat reclaim system, reheat system and the modification to the supply temperature set points.
• Changes to the standard operating procedures of the BMS system, to optimise the use of energy.  This was carried out in close conjunction with the BMS provider.
• Recalibration of sensors.  Many sensors were providing false information to the BMS system, causing the incorrect operation of the system and affecting the sequencing of chillers, pumps and fans.
The stated savings have been achieved by undertaking an integration of the MEP systems which were not carried out at the completion of the original project, some 10 years ago. 
The approach to save operating costs has been based on a sound understanding of the operational requirements of the systems and the requirements of integration between all of the elements of the systems.
The outcome of these works is that the client will save in the amount of 1,000,000AED per year, with a 16 month payback, and the equipment that had reached the end of its service life will be replaced.

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