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August 2017

The Challenge

The Plant Growth Facility (PGF) was identified as a priority building for the Energy and Carbon Reduction Project (ECRP) as it uses more electricity per square metre than any other building in the University’s estate.  Electricity costs are approximately £30,000 per month, despite the building being designed and built for reduced environmental impact.

The majority of building consumption is down to maintaining the specific conditions necessary for plant growth within 16 walk-in environmentally controlled plant growth chambers. Humidity, light intensity, temperature and composition of the air are all carefully regulated 24/7 and satisfying the cooling demand that this generates accounts for over 25% of the facility’s total electricity usage.

Despite being only 12 years old, the heavy loading on the chiller plant had made it increasingly unreliable and it struggled to control growth chambers’ temperatures during the summer months.

The Solution and the saving

ECRP came together with Estate Facilities to fund the replacement of the old chillers with new energy efficient units. The logistics of this project were significantly complicated by the fact that this is a 24 hour facility, with various environmental licences to adhere to, on a wider site that is open to the public.

The replacement of the chillers was phased, to keep the duration and frequency of any shutdowns to an absolute minimum.  During this phased replacement the opportunity was taken to alter and improve the refrigerant distribution which would further increase energy efficiency and extend the new chillers’ expected lifespan.

The project was completed in December 2016 with each new chiller being metered, with improved integration into the Building Management System. The system allows for more robust control and shows that significant electricity savings have been achieved, both on the baseload and during high demand conditions such as high summer temperatures.

Chiller plant consumption has reduced by 48%, a saving of over 350MWh of electricity per year compared to the previous system – which is equivalent to >120 tonnes CO2e or the energy use of 15 typical UK households!