Energy efficiency Hotel case study
Key conclusions of the study
Combined heat and power (CHP) unit can generate electricity on site and subsequently reduce the imported grid electricity and therefore the carbon emissions; this has been achieved with 972,000 kWh of electricity from the CHP.
The CHP system includes a heat dump to the atmosphere but it is unlikely that CHP operation is cost-effective when heat is being dumped. The CHP can operate at part load but it seems to be operated at full load. The heat dump is not effective and elevated return temperatures to the CHP can cause lock-out.
Alexandros Balaskas checks the combined heat and power unit.
• Allocating responsibility to a single manager; • Forming an energy working group (‘green team’); • Making further use of installed AMR supply meters, subsequently assisted by sub-meters, to enable performance monitoring of individual floors and to identify potential new areas for savings;
• Developing and implementing energy monitoring and targeting procedures;
• Starting to publicise energy efficiency actions and their achievements; and
• Regularly reviewing and updating the action plan as appropriate. Savings assessment: the three operational measures
– the staff engagement initiative, BMS schedule and operation review, and metering and half-hourly data review procedures – are assessed to save 12 per cent of energy consumption. The energy to be achieved by all three measures together and the occupant engagement alone (without BMS scheduling or metering feedback) is expected to save two per cent of electricity use, providing 47,000 kWh of electricity savings. No gas savings are attributed to this measure because these are associated with improved boiler control and scheduling, which is not in the control of the occupant.
Longer-term measures
As well as the above improvements, some extra changes are suggested that would have a longer-term impact: Voltage optimisation: This can achieve savings of five to 15 per cent depending on a number of features including the type of load connected within the building, how far away it is from the point of generation, and so on. A detailed feasibility study would need to be carried out to ensure voltage optimisation is cost effective.
Review of power factor correction: Power factor
correction equipment is installed but is reportedly not always achieving better than 91 per cent. This needs to be reviewed along with the supply tariff implications of poor power factor/high reactive power at present and in the foreseeable future. The Marriott Hotel Energy Group is working actively towards its main objective to become ‘greener’. Measures that Power Efficiency proposed refer to the time of the survey; however, the group had already progressed measures including:
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Adjustment of night operation strategy (fans and pumps) can lead to energy savings of 186,000 kWh of electricity and 350,000 kWh of gas, which represents 10 per cent of energy consumption.
Lighting average use in the hotel, currently 47.3 kWh/ sq m, is close to the Good Practice Benchmarks (40 kWh/sq m) for hotels; however it can be lowered by replacing the existing lighting in bedrooms (33 W tubes) with a more efficient type.
Versatemp system operation is quite efficient as the gas consumption is relatively low due to the simultaneous heating and cooling around the building. The energy consumed by the versatemp units represent a 60 per cent fraction of the total refrigeration consumption, which can break down into 365,000 kWh/year for heating and 243,000 kWh for cooling respectively.
The hotel in London achieved consumption figures close to the GP benchmarks for hotels – despite being a 24/7 building – due to Versatemp air conditioning.
The hotel’s energy consumption figure, without the operation of the CHP system, would be about 14 per cent better than the typical practice benchmark, and gas being 59m per cent better than typical practice.
• Installation of variable speed drives in areas such as the foyer and the restaurant;
• Lighting in areas like corridors has been replaced with LEDs; and
• The Marriott group has established a bonus-related programme that aims to improve the environmental awareness of hotel staff. l
For the full survey report, go to the digital version of the June 2010 CIBSE Journal at
www.cibsejournal.com To obtain a copy of CIBSE’s TM22: Energy Assessment and
Reporting Methodology, visit
www.cibse.org/bookshop
John Field and Alexandros Balaskas work for Power
Efficency.
www.powerefficiency.co.uk
June 2010 CIBSE Journal
43
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