Variable-speed drives achieve rapid payback at Chester Zoo

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JBC Controls has installed Danfoss variable-speed drives at Chester Zoo, resulting in energy savings worth thousands of pounds per year and a payback period of less than one year.

The North of England Zoological Society (NEZS) runs Chester Zoo, which has 1.3million visitors each year and cares for over 7000 animals from over 400 different species.

JBC Controls, in conjunction with Danfoss Drives, has installed variable-speed drives in three of the animal enclosures: Spirit of the Jaguar, Elephants of the Asian Forest and the penguins. Existing systems were upgraded in order to save energy and increase efficiency. As Glyn Berry, Sales Director of JBC Controls, explains: "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. The beauty of the drives being in IP55 enclosures was that there was no need to provide additional protective enclosures."

JBC Controls and Chester Zoo have a longstanding relationship, having been working on projects together 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.

The area where the greatest success has been realised is 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 filtration

The water filtration plant in the penguin enclosure 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 were not 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 is clear to see: the cost of installing and commissioning the drives was around £10,000, meaning that within 12 months Chester Zoo may profit from a greater return on its investment than projected. 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.

The jaguar enclosure has two drives (one 11kW and one 7.5kW) controlling 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, who has been Maintenance Manager at Chester Zoo for 10 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 coveted Queens Award for Enterprise in the category of Sustainable Development.

Chester Zoo is currently implementing its Energy Management Plan, aimed at delivering energy conservation and efficiency by developing operational and technological excellence in order to reduce environmental impact and control costs. Energy usage is constantly monitored using data loggers in various high-consumption buildings to identify opportunities for renewable technologies. The buildings environmental assessment method BREEAM has also been adopted in relation to the Zoo's capital development programme. A long-term plan is to become carbon-neutral, aiming for a 10 per cent reduction in energy consumption, which is a significant saving across the complex 110 acre site. The purchase and installation of Danfoss VSDs via JBC Controls is seen by all parties as a major step towards continual global environmental compliance and best practice, with an estimated £3000 reduction in monthly energy costs at Chester Zoo. This long-term investment supports the Zoo's proven track record in demonstrating its significant contribution to the protection of animals and reinforces its dedication to sustainability.

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