Cultural landmark becomes an energy-saving icon
How can you go about reducing a building’s energy consumption by over 20%? For a start, take a look at what has been achieved at the Wales Millennium Centre in Cardiff.
Although only five years old, the Wales Millennium Centre in Cardiff, which was officially opened by Her Majesty Queen Elizabeth II in November 2004 — a mere 33 months after construction had begun — has justified its vision to be an internationally significant cultural landmark and centre for the performing arts. Energy-saving initiatives undertaken by the centre’s energy management team achieved a saving of 15% in 2009 compared to the benchmark year of 2006. A projected £65 000-plus of further savings will be realised from energy initiatives commenced within 2010.
Renowned for its inspiration, excellence and leadership, visitors come to the centre to enjoy the full gamut of entertainments and arts participation — from blockbuster West End musicals to modern music and stand-up comedy, from art exhibitions to free daily foyer performances.
The building comprises shops, bars and restaurants, and is home to the Welsh National Opera, National Dance Company Wales, Urdd Gobath Cymru, and other prominent Welsh cultural companies.
Not only is Wales Millennium Centre the hub of cultural life in Wales, but it has also become one of Europe’s most sustainable cultural buildings. Earlier this year the Centre achieved ISO 14001 and is recognised as an exemplar by the Carbon Trust and is on track to reach or exceed the 2010 target of 21% energy-use reduction compared to the benchmark year of 2006. Now thanks to a thorough air-conditioning inspection, culminating in an improvement project carried out by HVAC energy saving specialist Efficient Air, the Centre can again demonstrate best practice.
The project was managed by David Bonney, technical manager for maintenance at the centre, and Efficient Air’s energy assessor Eric Agbozo, a CIBSE-accredited energy assessor for complex air-conditioning. It was undertaken as an ‘Article 9’ air-conditioning inspection survey of the HVAC systems and controls in line with the EPBD (Energy Performance of Buildings Directive) using CIBSE’s TM44 methodology.
The accompanying survey covered the inspection of HVAC systems — capturing the performance and powers of fans and associated heating and cooling electrical loads. The results gave David Bonney and his team the necessary data to compare the site’s performance against industry standards and identify crucial energy savings, whilst maintaining their minimum performance requirements.
From the quick-win and low-cost energy-saving initiatives that were identified, Efficient Air calculated an energy reduction of 80 350 kWh a year. This equates to a cost saving in the region of £7254 per annum and a CO2 reduction of around 44.6 t.
The second part of the survey looked at capital-investment opportunities, which when implemented would yield an energy reduction of 644 800 kWh a year, equating to a cost saving in the region of £58 032 per annum and a CO2 reduction of around 355 t.
Implementing all the energy-saving opportunities outlined in the energy assessor’s report has the potential to improve the HVAC energy performance of the centre by 28.3%. This equates to energy saving of 725 150 kWh a year, with a cost saving of £62 286 and a CO2 reduction of 400 t. With a payback period of between 3.3 and 6.5 months, David Bonney had little difficulty in receiving authorisation to commence the work.
The first step in the process, and a pivotal aspect of Efficient Air’s proven methodology, is a thorough investigation of every aspect of the building’s structure, its operational characteristics and the HVAC services. The building has a total floor area of 32 3750 m2, with a conditioned floor area of 21 222 m2. The areas are conditioned by 37 AHUs with air delivery provided via 72 off 4-pipe fan-coil units (FCUs).
Primary heating medium for the building is via a low-temperature-hot-water (LTHW) system. Chilled water is provided by two chiller units with a combined cooling capacity of 2236 kW. In addition to the central equipment, there are dedicated LTHW and cooling systems serving AHUs and FCUs in the Dance House and the Urdd’s 150-bed accommodation centre. These are centrally controlled with localised over-ride.
Humidification is provided by electric steam humidifiers to the main auditorium and orchestral practice room. In the case of the main auditorium, humidification is required to maintain optimum condition for performers, musical equipments and the internal building fabric (which is mostly treated wood for acoustic purposes). All units are centrally controlled via the BMS, with appropriate set points to ensure optimum efficiency.
Within a short space of time, Efficient Air’s energy assessor was able to make some general observations. For instance, most air-handling units on this site are providing greater levels of airflow than recommended CIBSE guidelines, with significant savings achievable by recommending that airflow is reduced to the required level as indicated in the quick wins. This can be done either by reducing the motor speed on fans that already have variable-speed drives (VSD) or changing fan pulleys so that the fans will run at a lower speed.
The electrical energy required for ventilation fans and air-handling units plays an increasing role in the energy demand on buildings. The specific fan power (SFP) value (expressed in kW/m3/s) indicates the efficiency with which electricity is used by supply and extract air fans in a building to move air. Recent studies have shown that the electrical consumption of existing air-handling-unit fans can easily be reduced from 5 to 10 kW/m3/s to a modern recommended level of 2 and 2.5 kW/m3/s through better design and more efficient components.
Now for the detail
Eric Agbozo’s report goes into great detail on every recommended action, supported by all the relevant calculations. In that regard it is a blueprint for energy saving in a building of this type. Some key recommendations listed in his action plan are summarised below, which offer excellent energy-saving improvements and contribute towards the carbon reduction of the building.
1. Reduce airflow to the foyer area. A reduction in air volume to AHU serving the foyer area provided an energy reduction of 53 100 kWh a year and carbon dioxide reduction of 29.2 t a year with payback of less than a month. This was achieved via a fan speed ‘setback’ on the installed inverter.
2. Door air curtain review. The installation of an effectively sized electric air curtain over the door will maintain the required thermal barrier and minimise cold draughts into the concourse during Winter periods.
3. Energy efficient humidification installation. Currently humidification provision is via electric steam humidifiers which operate at peak electric tariffs during performances. It was recommended that consideration should be given to replacing electric humidifiers with other energy-efficient humidifiers.
4. Valve replacement. Detailed inspection of one of the air-handling units indicated that valves were letting-by. Measured temperature readings of 35 and 14°C were recorded even though both control valves indicated a closed position. Valve replacement will provide an annual energy reduction of 1500 kWh and carbon dioxide reduction of 8.3 t, with a payback period of less than 3 months
5. Inverter installation. Installing an inverter on the primary LTHW circuit will provide an annual energy reduction of 40 000 kWh and a carbon dioxide reduction of 22 t, with payback within seven months.
6. Cooling for critical areas. Cooling for business critical areas is via fan-coil units fed from the main chillers/ice bank. Recommendation was given to isolate the fan-coil units and install an independent (standalone) split system controlled via the BMS. This will ensure that the chillers are switched off during the Winter, resulting in an annual energy saving of 604 800 kWh and carbon-dioxide reduction of 333 t, with payback period of less than four months.
With all the measures outlined in the report now in place, Wales Millennium Centre can claim, alongside its growing cultural reputation, a new status as a model of energy efficiency. This achievement has not come about through rocket science, but by sensible, methodical and professional investigation creating an awareness of the value of quick low-cost wins and strategic capital investment. It has made a welcome and immediate impact on energy and carbon savings.