An air conditioning system powered by natural gas engines is said to be providing low carbon cooling and heating at Scunthorpe General Hospital. The system uses seven Sanyo gas-powered heat pump (GHP) chillers to supply chilled water to air handling units serving a suite of operating theatres.
It replaced two aging Trane chillers based on hermetic scroll compressors running on R22. The internally located, ducted air-cooled machines, each originally rated at 165kW, had been installed in 1991.
Consultant Pick Everard evaluated several possible replacement options including a traditional electric chiller and turbo-based technology.
Jeff Fleming, who headed the project for Pick Everard, said: 'A key issue at the site was that there was no headroom on the electricity supply. Cooling loads had grown since the original chillers were installed, and replacing with a larger conventional electric chiller would have required a big investment in additional power supply.
'The Sanyo gas-engine driven heat pumps supplied by Oceanair (UK) Ltd not only provided a way round the power problem, they are a highly energy efficient solution. Our studies showed that, in terms of life-time costs, energy consumption and carbon emissions, they come out well ahead of comparable electric systems.'
A further benefit of the Sanyo units, he says, is their low noise, 'which makes them ideal for use in hospitals'.
Minimising liability
The seven GHP units, each with an output of 56kW, were chosen to minimise the hospital's liability under carbon reduction legislation. They are claimed to be resilient compared with a single large chiller.
'If one unit is out of action, there is capacity to provide continuity of service. In the case of a conventional chiller installation, breakdown can cause disruption and affect cooling to the building, says Sanyo.'
The power advantages of the GHP units extend to a much lower start-up current than standard electric chillers. As the process mirrors ignition in a modern vehicle engine, a few dozen Amps are all that are required for start-up rather than several hundred Amps for an electric chiller.
In winter, the heat pump cycle is reversed, providing heating to operating theatres. Each chiller produces an additional 18kW of waste heat that can be harnessed for use in generating hot water for the hospital's domestic supply.
Each of the R410A chillers has its own separate refrigerant-to-water heat exchanger within the building, eliminating the presence of water on the roof and overcoming the need for trace heating, anti-freeze and water treatment chemicals.
Engines require servicing every 10,500 hours, which equates to between two and three years.
For more information visit:
http://sanyo.com/aircon