Danfoss variable-speed drives, installed at Chester Zoo by JBC Controls, have brought about annual energy savings worth thousands of pounds — and a payback period of less than a year
With more than 7000 animals from across over 400 species attracting 1.3 million visitors a year, Chester Zoo, run by The North of England Zoological Society (NEZC), is currently implementing its Energy Management Plan to deliver energy conservation and efficiency. The aim is to reduce environmental impact and control costs.
As part of the plan, JBC Controls, in conjunction with Danfoss Drives, has installed variable-speed drives in three of the animal enclosures — Elephants of the Asian Forest, Spirit of the Jaguar and the penguins. Existing systems were upgraded in order to save energy and increase efficiency.
"All drives have been retrofitted adjacent to the plant they control: as the plant is existing we have had to rewire the fans' supplies to comply with the current EMC directive and standards set out by Danfoss," said JBC Controls Sales Director Glyn Berry. "The beauty of the drives being in IP55 enclosures was that there was no need to provide additional protective enclosures."
Chester Zoo has been working on projects with JBC Controls for the last five years. This combination of applications is the largest single energy-saving project undertaken to date and is likely to be the most rewarding, according to the statistical data gathered since the addition of the VSDs, achieving benefits of a financial nature in terms of reduced running costs while improving animal welfare.
Of the three enclosures affected by this latest project, the greatest success has been realised in in the elephant house. Optimisation of controls via the installation in August 2008 of an outside air temperature sensor to the BMS (building management system) controls enables determination of the modes of operation between the summer and winter setting based on ambient air temperature. This optimisation, the installation of the Danfoss drives and a demand-matched ventilation strategy has resulted in energy savings of up to 78 per cent being recorded: 55 per cent of the savings are directly attributable to the drives, which were installed at the end of July 2008. The forecast 'cube law' savings have been realised in this application — ie a reduction in speed of 20 per cent has reduced energy consumption by more than 50 per cent. The ability to control speed has eliminated motor start/stop noise that could potentially disturb the elephants, which was an unforeseen benefit for animal management purposes.
Water flow savings
In the penguin enclosure, the water filtration plant (illustrated above) has three 18.5kW drives (two duty and one standby, all installed in February 2008), which control water circulation to the pool area and automatically reduce the flow of water to 70 per cent at night. Improvements have not been as dramatic as those recorded in the elephant house, but the positive effect was evident immediately after installation of the drives. The average energy savings per month to date of 40 per cent in this area are directly attributable to the drives. The total cost of electricity in 2008 was £29,000 and the estimated penguin plant electricity bill at the end of 2009 is £17,000 based on year-to-date consumption figures, which represents a potential cost saving of £12,000.
Payback has been clear to see: the cost of installing and commissioning the drives was around £10,000 — within 12 months Chester Zoo may profit from a greater return on its investment than projected — while two more unexpected benefits are reduced noise in the plant room, together with improved water quality due to the more effective use of continuous ultra-violet light.
In the jaguar enclosure, two drives (one 11kW and one 7.5kW) control the surrounding fresh air in a similar manner to the elephant area via a BMS. The ventilation system is enabled by heating or cooling demand from room temperature sensors. In addition, should the system be off and the CO2 level increase, the system is enabled automatically.
Demand-matching control strategy
Installing VSDs has enabled the zoo to optimise efficiency by adopting a demand-matching control strategy, which is fundamental to the reduction in energy consumption on the associated HVAC equipment in both the elephant house and the jaguar enclosure.
Previously motors had to run 24 hours a day at one speed. Now, for the first time, the zoo is able to match the speed of the motor (or the pump, in the case of the penguins) to the demand of the system, switch the AHU off if heat, cold or a change in air quality is not required. Ventilation and seasonal demands can now be met easily, with no adverse effect on environmental conditions.
Ray Morrison, the zoo's Maintenance Manager for ten years, explains how environmental performance is equally as important as financial performance: "At Chester Zoo we adopt the principle of triple accounting; our performance is measured by how well we perform financially, environmentally and in terms of corporate social responsibility. Every £1 saved is £1 that can be reinvested in animal welfare and conservation projects worldwide, such as supporting Asian elephants in their natural habitat in the wild."
As part of Chester Zoo's compliance with Environmental Management Standard ISO 14001 — which was awarded to the Zoo in 2004 — its Environmental Policy statement says: "To achieve such improvements in environmental performance, the Zoo has set, and will maintain, review and revise, environmental objects and targets with the aim of continually improving our environmental performance".
Chester Zoo was the first zoo in the UK and the first major zoo in Europe to gain accreditation and use this international management standard to demonstrate and improve its environmental credentials. This commitment was once again recognised in 2006 when Chester Zoo received the Queens Award for Enterprise in the category of Sustainable Development.
