Key concepts: Energy management in office buildings

Submitted by: Jonathan Ramayia, Wednesday, October 10, 2012

<p>Heating and cooling is one of the significant energy users (SEUs) in office buildings. Changes can be made to reduce the energy demand in a building (Image credit: <a href=''>serenethos / 123RF Stock Photo</a>).</p>

Heating and cooling is one of the significant energy users (SEUs) in office buildings. Changes can be made to reduce the energy demand in a building (Image credit: serenethos / 123RF Stock Photo).

Office buildings are large consumers of electricity. Because of this, more and more organisations are initiating energy management programmes in offices, where there is also an opportunity to create a level of awareness about responsible energy use amongst staff.  This article outlines some keys concepts that are worth understanding when attempting to implement energy management in office buildings.

Energy monitoring

Energy monitoring refers to the continuous near second-by-second monitoring of energy that generates data that allows managers to understand exactly how much electricity is being utilised at a given moment. Best practice shows that monitoring of energy is the first step to reducing energy consumption. Energy monitoring is also important because it provides a benchmark from which to assess the effectiveness of an energy intervention. Depending on the size of your building, there are several options available to you. The larger a building, generally the more complicated the monitoring system. If a building is already on the electricity time-of-use tariff, it should have an energy monitoring device or meter that records energy data at regular intervals. In this instance, it may not be necessary to purchase a new meter as electricity data is already being recorded. However, it will be necessary to establish a method of easily accessing the information generated by the meter.  For smaller offices and buildings, see our article on energy monitors available in South Africa.

Energy base load

The energy base load of a building refers to the minimum amount of power that is required to operate that building. This is usually during off peak times when there is little or no activity in a building. For a typical office building, the energy base load should be significantly lower than during non-base load periods, e.g. when the building has all its occupants present. By installing monitoring equipment, you would be able to determine your building’s base load. It is useful to know your base load because you would be able to pick up wasteful energy use during times when energy use should be at a minimum. Our article on calculating the energy base load of a building explains this concept further.

Figure 1: Example of energy consumption of office building as measured by a monitoring device. As noted, the base load of the building refers to those periods when the building is not in use, example during the hours of 17:00 and 23:00; 00:00 and 06:00

Energy audit

Energy audits can help in gaining understanding the energy performance of a building at a specific time. Energy audits involve reviewing all the energy users in a building at the current time and making recommendations on interventions to reduce energy use. After an energy audit is conducted on your building, you will be able to understand how energy is used by the various components. Audits may include advice on whether you are on the correct electricity tariff, as well as whether your appliances are functioning efficiently. There are a number of companies in South Africa who offer energy audit services. But it is also possible for non-professionals to undertake their own energy audit by identifying all energy users, determining the energy rating of these energy users and comparing the actual energy performance of a building with the expected performance.   

Significant Energy Users (SEUs)

Significant energy users or SEUs are the main energy consumers in a building. This will differ for each building but some of the more common SEUs in office buildings are HVAC and lighting. As these are the largest consumers of energy in a building, the biggest gains in energy efficiency will be made by focussing on SEUs. 

Energy interventions

Energy interventions can be developed together with higher levels of management and energy audit teams to best maximise the use of financial resources and to suit the particular conditions of the building. Not all interventions are costly; some interventions may involve simply utilising natural lighting whereas other might involve replacing an entire outdated HVAC system.

Behavioural changes

Some of the most important changes can be made by staff members themselves. For instance staff can simply switching off their computers when they leave the office. . More unconventional approaches might involve encouraging staff members to dress in climate-appropriate clothing e.g. sandals in summer. Sustainability champions and building managers are important role players in a successful energy efficiency staff campaign to promote the responsible use of energy in buildings.

Building Energy Management System (BEMS)

A building energy management system (BEMS) is an automated system that may be employed to ensure maximum efficiencies are obtained for components of a building. Usually, the HVAC (heating, ventilation and air-conditioning), lighting and all other electrical components can be set to switch off when the building is not in use. The BEMS may be also programmed to suit the specific energy needs of a building. The BEMS market is growing internationally but before installing a system ensure that the BEMS service provider provides a breakdown of the estimated savings that could be accrued as a result of installing the BEMS. BEMS are one of the most expensive building energy management interventions, and not affordable for every organisation. Other cheaper, interventions, may be just as effective in reducing the energy demand of a building and the BEMS is usually implemented if the above six points do not result in significant gains in energy efficiency.


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Jonathan Ramayia