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bar and restaurant ventilation systems. The three air handling units each have supply and extract fans with a consumption of 202,000 kWh. Achieving 25 per cent saving results in a saving of 51,000 kWh a year. Installation of variable speed drives on the three
supply and three extract fans has budget costs at £3,500 per fan of £21,000. Payback: 4.2 years. Lighting: the hotel has already put in place an
programme to replace the existing lighting in areas such as corridors and toilets with LEDs. Installation of a lighting control system would enable effective control by hotel staff including presence detection and time scheduling. Energy use by lighting was assessed at 52,000 kWh, with average operating hours of 6,800 hours a year. With presence detection and time scheduling as above a saving of 20 per cent is assessed giving annual savings of 104,000 kWh. Budget costs for these selected areas, excluding the main en-suite rooms which comprise half the floor area, are assessed at £40,000. The simple payback period is 3.9 years. Staff engagement: this is an exercise to engage
occupants with the objective of operating efficiently and hence saving running costs and reducing CO2 emissions. Payback: Six months. The key changes include: • Introducing a series of presentations to staff on energy awareness matters.
• Obtaining posters and stickers (for example from the Carbon Trust) and displaying them in appropriate and prominent positions around the site;
Top: The chiller system. Bottom: Variable speed pump control panel.
Services Installations in the hotel
CHP
A combined heat and power (CHP) unit provides low temperature hot water (LTHW) heating water from engine cooling water and waste gas flue heat exchangers. The CHP system is connected in series with three gas-fired boilers acting as lead boiler followed by the gas fired boilers when heating duty demands. The CHP system has an excess heat exchanger which rejects heat when the CHP system is running and thermal demand load of the building is less than the CHP system thermal output.
Chilled water
A central chilled water system is served by a dry-cooled chiller with two independent circuits comprising integral compressor, evaporator, and condenser. Chilled water pumps circulate primary chilled water to various circuits in the building. The chiller has a dedicated dry air cooler for heat rejection together with condenser water pumps.
Air conditioning
Air-conditioning is provided by a water loop heat pump system of the Versatemp type, comprising heat exchangers, circulating pumps, dry air coolers and Versatemp terminal units located throughout
the building. Versatemp units incorporate a hermetically sealed reverse cycle heat pump which either provides heating or cooling as necessary to the space in which they are installed. The Versatemp units are connected to common flow and return pipe work circuit; each unit will either reject hot water to the circuit or take cooling water from the circuit depending on the load requirement of the space in which they are installed.
Ventilation
Ventilation is provided by air-handling units serving several areas of the hotel. The building management system (BMS) enables the ventilation plant to operate at various times. The foyer air-handling system has free cooling recirculation and is typical of systems in the conference facility, restaurant and bar. Staff dining has a once-through system without recirculation. The swimming pool ventilation system includes recirculation and detects the return air humidity and also carbon dioxide concentration which indicates occupancy levels.
Domestic hot water
Domestic HW is provided by a plate heat exchangers served by primary LTHW from the heating system.
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CIBSE Journal June 2010
www.cibsejournal.com
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