Potential for savings
Although a uniform breakdown is impossible to give, owing to the very different economic, climatic and other conditions globally, data show that the commercial sector accounts for 20 % to 40 % of the energy used in industrialized countries. Buildings, such as offices and retail outlets, represent the lion’s share of the energy consumption in this sector. Therefore, the potential for very significant reductions in energy consumption is considerable, and ZEBs (zero-energy buildings) will play a major role in achieving these savings.
Buildings, commercial, industrial or residential, are ensembles of countless different and complex elements and systems. Achieving zero net energy consumption and carbon emission of buildings means adopting a systems approach, which requires dealing with all the parts together and looking at both cutting consumption and producing energy. This systems perspective and energy efficiency are at the centre of the IEC’s White Paper “Coping with the energy challenge”. The IEC is working on International Standards for most systems used in ZEBs.
Heating, cooling and ventilation represent major shares of the energy consumption of commercial buildings. Heating is mainly provided by fossil fuels (gas or diesel fuel), cooling and ventilation by electric energy. In the US (United States), for instance, heating makes up 38 % of the total site energy consumption, of which less than 2 % comes from electric power. As for cooling, ventilation and refrigeration, they make up some 20 % of the total site energy used. The respective shares could vary elsewhere, but heating, cooling and ventilation would still be major energy consumers.
Cutting the energy required to heat, cool and ventilate buildings can be achieved in great part through passive measures, such as proper insulation of the building envelope (walls, windows, roof and floors) and other measures, such as orientation or design (balconies or blinds providing shade).
But active measures, such as the installation of programmable thermostats and of heat pumps, must be taken to cut significantly the use of fossil fuels or the overall electric energy consumption to heat or cool buildings. IEC SC (Subcommittee) 61D: Appliances for air-conditioning for household and similar purposes, prepares International Standards for electrical heat pumps, air conditioners and dehumidifiers.
Lighting represents around 40 % of total site electric energy used in the commercial sector. This includes office and storage space, site and external lighting. Cutting electricity consumption for lighting is thus essential. At a time of relatively cheap energy, little attention was paid to sensible use of lighting in the commercial sector; unoccupied office or storage space was often constantly lit.
Nowadays, timers and sensors contribute to cutting the electricity needed for lighting commercial buildings, switching off or on lights as required. IEC TC 47: Semiconductor devices, prepares International Standards for integrated circuits and sensors, among many other devices and systems.
The consumption of electricity for lighting can be cut significantly also by replacing incandescent lamps with more efficient lights such as fluorescent, compact fluorescent or LED (light-emitting diodes) lights. IEC TC 34: Lamps and related equipment, and its SCs, prepare International Standards for all types of lamps and luminaires.
By definition ZEBs must produce energy to achieve zero net energy consumption and zero carbon emission. The current emphasis placed on renewable sources of energy and significant advances in technologies offer many possibilities for achieving these objectives in commercial buildings.
Tapping renewable energies
Converting solar radiation into electricity using PV (photovoltaic) installations is emerging more and more as a cost-effective solution for stand-alone or grid-connected applications. Solar panels are proving increasingly popular for the commercial sector for these economic reasons and also often, in no small measure, to project a "Green" corporate image. IEC TC 82: Solar photovoltaic energy systems, which prepares International Standards for systems of PV conversion of solar energy into electrical energy, is involved in all PV aspects. Its scope extends constantly to include new PV technologies.
Crystalline silicon PV modules are still the dominant type, but thin-film PV modules have improved considerably. Thanks to nanotechnology and new materials they can now be printed or even sprayed directly onto a variety of surfaces and fully integrated into windows. These solar windows, known as PVGUs (photovoltaic glass units), help offset and even exceed a building’s energy use.
Harnessing wind power for use in commercial building is generally less developed than using solar power, but solar-wind hybrid solutions are being developed. IEC TC 88: Wind turbines, prepares International Standards for wind turbines that convert wind energy into electrical energy.
Storing and feeding back energy
Producing energy on commercial sites is a major benefit, but being able to store it and to make it available to other users via the grid are important issues too.
The energy produced by ZEBs comes mainly from renewables, which are intermittent sources. It is therefore important to store the excess energy generated at peak time to use it when needed. Batteries play an important role in this task and the work of IEC TC 21: Secondary cells and batteries, which prepares product standards for all secondary cells and batteries, is essential in this domain.
Feeding back excess electric energy into grids if it is produced is another possible benefit.
A long-term perspective
All the technologies needed to build ZEBs exist, yet buildings are, by definition, made to last. This means that many commercial buildings, built when energy – electric energy in particular - was cheap, are not energy-efficient. Bringing all of them to ZEBs standards will take some time, but measures can be taken also to cut significantly the energy consumption of commercial buildings through refurbishment and installation of new systems.