Energy Efficiency in Electrical Installations
Ensuring that an installation is safe enough to allow satisfactory operations and has sufficient capacity for existing needs has typically been enough for most installations. Some installations, with safety critical operations, may also have considered resilience to avoid single points of failure and provide system continuity. This means that, until relatively recently, the traditional model of an electrical installation design hierarchy would have been:
Energy efficiency updates the hierarchy of design, and that affects the operation of electrical installations. The traditional design hierarchy will change to this:
There is a change of emphasis to incorporate energy efficiency into electrical installation designs as a prerequisite, not just as an aspiration.
Future electrical installation designs will still need the required level of safety and capacity; they will also require the lowest possible electrical consumption.
An energy efficient electrical installation:
- has less environmental impact generally;
- reduces energy losses and lowers energy costs;
- uses energy when it is required and potentially at a lower tariff;
- may have less reactive maintenance due to heat loss; and
- optimises system performance throughout its life cycle.
Designers should consider these factors:
- the efficient placement of the electrical intake;
- the efficiency of the electrical distribution wiring system;
- the type of controls to avoid wasteful use of loads;
- how and where to provide energy measurement;
- how and what type of loads can be switched off without affecting user safety, function or comfort;
- energy management of electrical systems; and
- the impact of maintenance on the efficiency of electrical systems;
The first design requirement is to stress the importance of understanding the energy profile of both the passive and the active measures taken within the building:
- active: measures for the optimisation of electrical energy produced, supplied, flowing and consumed.
- passive: measures for the choice of parameters of electrical equipment to improve overall electrical energy efficiency of the electrical installation while not affecting the initial construction parameters.
The second design requirement is to reduce energy losses within the electrical installation by two principal methods:
- the location of any energy source (conventional high voltage (HV) or low voltage (LV) intake, local generation, and switchboard) should be optimised where possible.
- the reduction of losses within the installation wiring system is important. Some design criteria will be understood in terms of voltage drops, maintaining power quality and improving power factors. Other considerations in terms of harmonics, typically caused by end user appliances, can cause operational inefficiencies. The issue of harmonics caused by new equipment on older electrical distribution infrastructure is an increasing cause for concern.
Many new installations seek accreditation from BRE’s BREEAM assessment method, Leadership in Energy and Environmental Design (LEED) or similar benchmarks. The IEC standard is a design framework for a more energy efficient electrical installation.
The client’s design brief should stipulate the required level of energy efficiency measures (EM) to be applied to an electrical installation in 13 categories. The design also influences the operational activities of the electrical installation after commissioning. Three categories specify the required energy efficiency performance levels (EEPL).
EM and EEPL summarise the electrical installation efficiency classes (EIEC). Rated from 0 to 4, these classes can be monitored, checked and improved on over time. Continuous systems of plan (by efficiency measures), do (through efficiency performance levels) and check (using installation efficiency classes) provide the basis to act on improvements in electrical efficiency overall.
Most legislative initiatives on energy efficiency relate to new buildings. However, IEC 60364-8-1 recognises that the replacement of existing building stock is relatively low at around 2 % to 5 % per annum and it states that it should be applied to existing as well as new building stock. Applying a standard retrospectively is always difficult, but the standard states: “it is in the refurbishment of existing buildings that significant overall improvements in energy efficiency can be achieved.”
Other topics addressed by IEC 60364-8-1 include:
- electrical energy supply types;
- the operation of controls to improve energy efficiency input to a system;
- load inertia and the effects both on users’ needs and on efficient operations;
- the operation of controls to monitor consumption and inform users;
- design of barycentres;
- load types and how to improve efficiency at the design stage; and
- installation maintenance.
The standard is quite clear that safety remains important. Any measures taken to make an electrical installation more efficient must not compromise the safety of any occupants, property or livestock.
All topics are explained in full in the Designer’s Guide to Energy Efficient Electrical Installations, which is now available to order.