Energy efficiency and electrical installations

Jake Green, Scolmore’s Technical Engagement Manager, provides some insight into the integration of electricity generation, energy efficiency management systems and energy storage into a prosuming whole.

The ever-rising cost of energy has become a significant factor in the drive to improve energy efficiency. Whilst data gathered by the Government in England and Wales highlights that since 2005 there has been a downward trend in the usage of gas and electricity in all properties irrespective of their age, present price trends are on a rapid upward curve.

The current prosuming technologies (PV, generators etc.) provide an opportunity to integrate both electricity generation, energy efficiency management systems and energy storage into a prosuming whole enabling a more varied means of supplying and using electricity. It may transpire that a new Chapter 81 will be introduced into Amendment 3 of BS 7671 whenever that happens in the future.

The introduction of Chapter 82 into Amendment 2 of BS 7671 has provided additional guidance for the integration of energy efficiency/energy management into the operation of electrical installations.

This article very briefly considers some of the guidance provided by the informative Appendix 17 (Energy Efficiency) detailed in BS 7671 and the Harmonised Document published by BSI, Low-voltage electrical installations Part 8-1: Functional aspects – Energy efficiency (IEC 60364-8-1: 2019) and discusses some of the factors that should be considered when considering energy efficiency and energy management.

Legislation

In all parts of the UK there are specific requirements detailed in the associated building regulations for energy efficiency. In England reference should be made to Part L and the associated guidance found in Approved Documents L1 and L2; in Scotland reference should be made to the Building Regulations Technical Handbooks (Domestic and non-domestic).

Reference should always be made to the legislation and guidance issued by the various parts of the government in the UK.

Appendix 17

The purpose of Appendix 17 is to ‘…provide additional recommendations for the design and erection of electrical installations, including installations having local production and storage of energy, for optimising the overall efficient use of electricity.’ Whether human behaviour has a greater impact on energy usage than any energy management system, controls will play a significant role in any design considerations (clause 17.2).

It is the case that little thought is given for ‘…optimising the overall efficient use of electricity’ when an electrical installation is being designed. For example, cable sizes are determined based upon the design current of the circuits, the rating of the protective device(s), and various rating factors. The selected cable is designed to limit the rise in temperature during current-carrying conditions to a safe level within the limitations of the cable. Currently there is no regulatory imperative for the designer to take account of any energy efficiency factors.

A proposed Chapter 81 based on the current Harmonised Document (HD) would require the designer to factor into any calculation the efficient use of electrical energy. Clause 17.11 (Appendix 17) suggests that the design of an electrical installation should consider energy efficiency at every stage, including the impact of different load demands, usage etc. One implication of this is that distribution boards will need to enable the segregation of circuits supplying each zone or mesh as defined.

It will be necessary for the user to be able to monitor the electrical installation (clause 17.12) and, therefore, the measurement of total consumption in kWh for every hour of each day should be logged and stored for a minimum of one year and be accessible to the user.

However, a simplistic approach to energy efficiency might fail to consider, for example, embodied energy – that is the ‘unconsidered’ energy demands in the production of more/larger boards/cables and the like. The designer should not, therefore, simply increase cable sizes to limit voltage drop, or create meshes and zones thinking that these alone will necessarily reduce energy usage.

Design considerations

When considering the availability of electrical energy, the designer and user will have to consider, as a minimum, the following (clause 17.2):

- Selection of energy efficient appliances

- Assignment of load priority for use as an input of the load optimisation process – including any load shedding

- The intended use of the installation in providing an energy efficient design, and

- The provision of a manual override facility enabling the user to take control from any automatic functions.

The design requirements detailed in clause 17.3 are:

- Load energy profile

- Availability of local generation, such as PV, wind, generator and the like

- Reduction of energy losses in the electrical installation

- The tariff structure

- Arrangement of circuits

- The nature of the customer demand.

For the design of any energy management system the user specification is critical and to that end, prior consultations must be made to ensure that the energy efficiency management system (EEMS) is correctly set up. Furthermore, the user must have the final decision over whether or not to operate a service at optimal or nominal values, or not to operate for a period of time should the need arise; for example, where someone is ill and a room requires additional heating or when a company receives an urgent order that must be completed (clause 17.2 Note).

Data gathering

What is clear is the need for good data gathering. Such data will include the presence of people, temperature, air quality, daylight, operating time and cost of energy (clause 8.3.1.1 BS EN 60364-8-1). The means of gathering data will vary according to the need. Table 1 in BS EN 60364-8-1: 2019 provides guidance on measurement applications.

Measurement applications

Usual device name

Complementary explanations

Billing

Revenue/electricity/utility meter

Energy metering for billing applications

Energy usage analysis

Power/energy meter

Energy cost and usage analysis

Power monitoring

Power/energy meter

Demand side power quality analysis and energy cost and usage analysis

Energy estimation

Energy estimator

Devices for giving information needed to correctly operate the energy management system.

Without this data, the effectiveness of the EEMS will be limited. Clause 17.8 of Appendix 17 states, ‘Measurement is a key parameter to determine the efficiency of the installation giving the user an awareness of energy consumption.’

The EEMS should be designed in such a way that there is no reduction in the available supply or in the safe operation of any part of the installation.

Conclusion

This article has only been able to touch upon a few important elements and likely to have raised more questions than provided answers for the reader. Such questions might include:

- What is the likely direction of travel for monitoring all electrical energy usage within an electrical installation?

- What support is available to train designers of electrical installations in energy management systems?

- What are the likely payback times for the additional measurement systems?

- What consideration has been given to embodied energy?

It is clear that there is enormous scope for energy monitoring systems, data logging systems and training support for electrical designers as they begin to consider energy efficiency as part of the norm when designing electrical installations.




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