Upgrading AHU fan delivers surplus air flow

Upgrading AHU’s with plug fans using EC motor technology, reduced Heathrow’s energy consumption by 30-60 per cent.

AHU (air handling unit) is an application being utilised to circulate air to all directions, and is connected to any HVAC’s central unit. Air handling unit is a large metal box that conditions the air, which helps in creating a perfect atmosphere. Blower/fan, heating and/or cooling elements, filters, humidifier, mixing chamber, heat recovery device, controls, vibration isolators are some of the components that make an AHU.

With more than 80 million passengers in 2018, Heathrow Airport serves more passengers than any other airport in Europe. One of Heathrow’s goals is to operate a ZERO carbon airport infrastructure by 2050. With an ambitious goal for reducing carbon impact calls for serious energy-saving initiatives, Munters has performed AHU fan upgrades with 15 GWh savings per year.

Operating four huge passenger terminals, covering almost 600,000 m², the amount of energy used for creating a comfortable indoor climate for passengers, shopkeepers and employees is massive. Energy Project Manager, Andy Dobbs, is responsible for energy saving projects related to all HVAC installations in the terminals.

Since 2016 Andy Dobbs has been working with Munters’ climate control specialists on an extensive energy-saving upgrade of air handling equipment in the terminals.

Fan upgrade saves 15 GWh/year
By replacing older and often belt-driven, AHU exhaust and process fans with smaller, more energy efficient and maintenance free EC fans in a fan wall configuration, Heathrow has been able to reduce energy consumption on these AHUs by 30-60 per cent. In total, Munters have upgraded more than 150 AHUs, resulting in the installation of, approximately, 500 EC fans.

Energy savings on these projects amount to an impressive total of 15 GWh which equals to the annual energy consumption of no less than 3,400 households (based on UK average).

Munters and EC plug fans
Energy efficiency has become an integral part of building services design, maintenance and upgrade. Many organisations overlook air handling units (AHU’s) while looking to save energy.

Upgrading AHU’s with plug fans using EC motor technology can realise significant savings in energy, maintenance and more. Munters has developed a fan wall configuration concept that is pre-designed and eases the on-site installation.

Overnight upgradation
A fan upgrade, typically consisting of a fan wall with 3-6 EC fans, can be performed in one single night shift. For Heathrow that means that the upgrade work itself will have no negative impact on the daily operation, just as passengers and partners in the airport will not be affected.

AHUs of very different sizes and age have been upgraded, the smallest with an airflow of 5,000 m³/h, the biggest being a plant consisting of four huge AHUs in Terminal 5 (T5), each supplying 230,000 m³/h.

Huge project with short ROI
A break-down of bearings in one of the AHU axial fans initiated the T5 upgrade project. To replace the big fan would be an almost impossible task, given that fact that the AHUs are situated five storey down, with complicated and limited access.

Based on data loggings and thorough energy calculations, Munters were able to predict energy savings that would grant a return on investment (RoI) at only 2.4 years. The limited and restricted access on top of the logistic challenges in working in a plant room five stories down, implied a lot of extra work on removing old waste etc. Facts, that consequently lead to a RoI of the total project slightly below three years, though still being very attractive to Heathrow.

Comprehending to Heathrow’s needs
The upgrade project was led by Munters’ Project Manager Chris Stead, who was involved in thorough planning. Heathrow’s concern of passengers comfort was of the highest importance, and Chris Stead worked out a detailed plan on how to take out one of the existing fans at a time, in a way that would maintain a sufficient airflow during the upgrade process, not compromising passengers comfort.

After the successful completion of the project, continuous data logging has verified the calculations, and in total the T5 project saves Heathrow no less than 1.5 GWh per year. The four impressively big fan walls, in total providing an air flow at 920,000 m³/h, might very well be the biggest fan wall in the World so far.