Latest developments in International Standards for energy efficiency
This replaces IEC 60364-8-1 Edition 1 published in 2014. In this article, we give a brief overview of some of the latest requirements at an international level, which may or may not be incorporated in BS 7671 in the future. The new standard includes a number of changes including changes to the definitions and to the energy efficiency assessment for electrical installations.
The worldwide need to reduce the consumption of energy means we have to consider how electrical installations can provide the required level of service and safety for the lowest electrical consumption.
In order to make improvements we need to be able to measure the amount of electrical energy consumed and monitor and control energy effectively. Energy measurement is essential for energy management. Therefore, the design of the electrical distribution system needs to be carried out in such a way that will allow the metering and control of the various electrical loads in an installation. Also, in order to have an energy efficient installation, losses in equipment need to be as low as possible. All these aspects are taken into account in the new standard.
Energy efficiency assessment for electrical installations
A new section 4.2 has been introduced which requires the assessment of electrical installations in accordance with Annex B of the standard.
Method to assess the energy efficiency of an electrical installation
The informative Annex B has been completely revised in the new standard. However the objective is still to provide an assessment of the energy efficiency of an electrical installation based on the relevant parameters influencing efficiency such as lighting, voltage drop, power factor correction, Motors and controls etc.
The method applies to both new and existing installations, in premises used for purposes including industrial, commercial, infrastructure and residential as the previous edition.
However, in this new edition the way in which the method is applied for residential premises differs in some ways from the way it is applied for other types of premises.
In this new the standard the energy efficiency of an electrical installation is rated into one of the following classes from the lower efficiency to the higher efficiency:
The electrical installation efficiency class is determined by adding together all the points obtained from the tables corresponding to each parameter. There are separate sets of Tables for residential compared to industrial, commercial installations and infrastructure.
Where a parameter is not assessed, then 0 points are given for that parameter.
The total number of points is then compared with the number of points given in Table B.1 to determine the electrical installation efficiency class which ranges from EE0 to EE5.
Input from loads, sensors and forecasts
Section 8.3 of the new standard covering inputs from loads, sensors and forecasts has been revised. Requirements concerning the measurement of electrical parameters has been extended as this is key to energy efficiency.
Lighting can represent a large percentage of energy consumption in buildings depending on the application. Solutions for lighting control could achieve significant savings on the electricity compared to a traditional installation (without automatic lighting controls).These systems should be flexible and designed for the comfort of the users. The solutions can range from very small and local controls such as occupancy sensors, up to sophisticated customised and centralised solutions that are part of complete building automation systems.
Lighting controls for residential buildings are easy-to-install devices which are able to detect the presence of people and only switch on lights when required. Lighting controls eliminate wasted energy and save energy simply by switching lights off when not required. Lighting controls for commercial, public and industrial buildings are again easy-to-install devices that are able to automatically switch off lights when no occupants are detected or there are suitable levels of natural light.
When considering the design and installation of lighting controls there are a number of important points to consider. First, it is important to take into account the type of space, how it is used and the amount of daylight available. The type and use of space will determine the type of sensor and therefore the control used.
Safety is also an important consideration. The operation of lighting controls should not endanger the occupants of the building. This may happen if a sensor switches off all the lighting in a space without daylight. It is therefore important that lighting controls are designed correctly to ensure the safety of occupants and save energy.
Commissioning should be included as an essential part of the installation of lighting controls. Commissioning could include calibrating photoelectric controls, checking that occupancy sensors are working and setting a suitable delay time for occupancy sensors.
Electric motors are used in a wide variety of applications in commercial and industrial installations. These include motors driving fans for ventilation and air-conditioning systems, motors driving pumps for refrigeration and chilling applications and air compressors.
Pumps and fans probably represent one of the largest applications for motor-driven power. The use of variable-speed drives (VSD) to adjust the speed of the pump or fan to deliver the required flow, could result in energy savings.
Power factor correction
A poor power-factor is undesirable for a number of reasons. Power-factor correction technology is used mainly on commercial and industrial installations to restore the power factor to as close to unity as is economically viable. Low power-factors can be caused by reactive power demand of inductive loads such as induction motors and fluorescent lights. A poor power-factor reduces the effective capacity of the electrical supply, since the more reactive power that is carried the less useful power can be carried, also causes losses at transformers, and can cause excessive voltage drops in the supply network and may reduce the life expectancy of electrical equipment.
For this reason electricity tariffs encourage the user to maintain a high power-factor (nearly unity) in their electrical installation by penalising a low power-factor. There are a number of ways in which power-factor correction can be provided. The most common way that this can be achieved is by the installation of power factor correction capacitors. These can be installed in bulk at the supply position or at the point of usage on motors, for example. Persons involved in this type of work are recommended to seek advice from specialists on the most economic system for a given installation.
On site renewable energy sources do not of themselves increase the efficiency to the electrical installation but reduce the overall utility network losses as the consumption of the building from the utility is reduced.
There are a wide range of microgeneration technologies including Solar photovoltaic (PV), wind turbines, Small scale hydro and Micro CHP (Combined heat and power). Microgeneration systems such as solar PV installations should always be carried out by a trained and experienced installer. For example, where the PV panels are roof-mounted the roof must be strong enough to take their weight, especially if the panel is placed on top of existing tiles. It is also important to note that there are mandatory requirements concerning the parallel connection of generators with the supply network.
Please note this article is only a brief overview of some of the latest requirements at international level, which may or may not be incorporated in BS 7671 in the future. For more information refer to IEC 60364-8-1 Edition 2.
Note: It is important to consult the Building Regulations when designing electrical installations. The Building Regulations deal with energy conservation issues such as energy-efficient lighting.