Positive steps to reducing energy use in existing buildings

Schneider Electric, energy efficiency
Understanding how power is used in buildings is the key to existing buildings reducing their energy consumption by 30% by 2020 to meet Government targets for reducing carbon emissions.

Every building that exists today needs to reduce its energy consumption by 30% by 2020 to meet the Government target of reducing energy consumption by 20%. David Lewis suggests how.

Up to half the carbon-dioxide emissions attributable to commercial buildings are from electricity consumption. As equipment such as air-conditioning and ventilation systems increase in use, this consumption will rise. With new construction accounting for a small proportion of building stock, every building that exists today needs to reduce its energy consumption by 30% by 2020 — at the rate of one in 10 every years — to reach the target to reduce consumption by 20% by 2020.

The refurbishment of stock and improving energy management is vital in meeting targets. So let us go back to the fundamentals of building design to discover where savings can be made.

With the debate about climate change continuing to rage, the issue of the UK’s use of fossil fuels remains, which is why action still needs to be taken to lower energy consumption. In many businesses, the explosion of information technology has led to a massive increase in electrical consumption, which has been coupled with the growth of air conditioning systems.

The prolific rise of new industries such as data centres has also contributed to a dramatic rise in power usage. It would be hard to imagine life without energy, but that does not mean consumption cannot be controlled.

However, reducing energy consumption is not just about making sure the latest energy-saving technologies are used in new developments. With the number of new builds diminishing because of the current economic climate, building designers must focus on helping businesses improve the energy performance of existing facilities.

Going back to the fundamentals of how a building is used will allow users to fix the basics and improve energy efficiency. This begins with organisations encouraging simple behavioural changes like switching off lights or IT equipment when not required.

From this point, is it possible to install simple solutions that can be gradually built up over time into a more comprehensive, integrated system. A good place to start is with straightforward controls for core areas of energy use.

Lighting alone can account for up to 40% of a typical commercial enterprise’s electricity consumption. In retrofit applications, control command devices are effective at lowering energy usage.

Voltage-regulation systems can operate lighting in external parking areas for office blocks or loading bays, achieving a 30% energy reduction. The system allows the operating voltage of the lighting to be reduced whilst maintaining appropriate lighting levels. This method of operation also results in longer lamp life, which can save significant amounts of money on the maintenance of commercial properties.

After installing low-energy lamps, achieving the most energy-efficient lighting solution means optimising lighting based on the three parameters of time, light level and occupancy.

Time-delay switches are ideal for less-frequented areas of a building or those where entry and egress are at different points. Solutions are electronic and fully programmable to whatever time setting is required — from as little as two minutes or as much as two hours.

Occupancy sensing, commonly known as presence detectors or PIRs, will detect the presence or absence of people within the parameters of the sensor and turn lights on and off accordingly. This solution is most suited to areas where occupancy is unpredictable, such as meeting rooms and private offices. For spaces where use is much more regulated and predictable, scheduled lighting controls can be used to turn lights on and off at set times.

Going beyond just switching lights on and off, a daylight-harvesting control reduces power to the lights or turns them off completely, depending on the level of natural light. Photo-sensors linked to dimmer devices will vary the lighting output and provide an ideal solution for premises that have numerous offices and meeting rooms with many windows, or, even, a modern, glass-fronted building where the space is not always used and the quality of natural light varies.

It is important to recognise the benefits of command control components in other areas as well as lighting. These controls can also be used to manage heating, ventilation and air conditioning — leading to a complete building-management programme.

As part of the basics of building design, it is also important to consider passive energy-reduction measures to better utilise energy. This means looking at the power consumption of different technologies and installations, from busbar trunking to electrical devices such as circuit breakers, contactors and low-loss transformers.

Power-quality issues can seriously affect a site’s power factor and its efficiency. Active harmonic filters (AHFs) provide the simplest and most effective means to mitigate harmonics, reduce process-related voltage fluctuations and improve equipment operating life and system capacity. AHFs inject harmonic and reactive current to limit harmonic distortion, improving displacement power factor for the electrical distribution system.

Power-factor correction (PFC) also gives significant cost savings, with an excellent return on investment. The quantity of electric motors, induction heaters and fluorescent lighting installed in buildings has increased, reducing the power factor and the efficiency of the power supply. Using PFC lowers the current drawn from the electricity supply, decreasing reactive power charging, consumption and CO2 emissions — thereby creating a greater supply capacity through more efficient energy use.

In all commercial buildings it is important to understand how power is used and what technologies are available to manage and save energy. While infrastructure systems can help manage an entire building, there are also advanced controls that can help fix the basics, contributing to maximising the efficiency of existing building stock.

David Lewis is energy-efficiency specialist with Schneider Electric.


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