Following completion of benchmarking and in advance of conducting a Decarbonisation Options Assessment, it may be appropriate to consider additional data collection and/or deployment of sub-metering. There may be differing levels of data availability and quality between building(s) and it is advantageous to have half hourly energy consumption data available, which offers the following benefits:
> A more accurate baseline than may be currently available which can be used as a comparison after anything has been installed
> An opportunity to improve operational performance through the identification of anomalies including excessive consumption
> Data which will help the design and optimisation of the Decarbonisation Options (see section 7.14)
> Verification of any savings that are achieved (see section 7.20)
To improve the quality of data provided on sites and buildings, sub-metering is a common solution - this can be either the installation of new sub-metering or the enhancement of existing sub-metering. The sooner that good metering is installed/enhanced, the longer the period of data available and therefore the better the quality of the site baseline data. This is particularly important in large, complex sites, buildings with multiple occupants and/or buildings which rely on manual meter readings. Consideration should be given the internet enabled, smart electric meters suitable for commercial and industrial applications. These systems can be deployed as a primary meter, submeter or used for other electric metering applications such as energy usage tracking, demand reduction, power factor correction, etc. Besides tracking peak demand (kW) and energy consumption (kWh), advanced meters integrate many important features and provide enhanced functionality such as automatic outbound reporting using 100% open protocols.
In addition to primary and submetering, temporary or mobile monitoring of energy could be used to compliment the quality of building baseline data or to monitor energy consumption on a temporary basis e.g. in a specific area of use, on-site individual circuits or equipment supplies. Temporary metering allows easy metering of large three-phase plug-in equipment such as refrigeration units, catering equipment. Also, temporary or portable meters can be used to quantify the effect of implementing energy saving initiatives.
Traditionally sub-metering has been on electricity meters however with a need to move away from fossil fuels it is now more important to ensure that sub-metering covers both electricity and heat use. This can be done through the metering of the fossil fuel used or the heat being distributed across the building(s). Sub-meters should be incorporated into a BMS system (either new or existing) where possible.
Sub-metering can also outline the energy performance of different zones within a building and/or different energy systems (such as heating, cooling, hot water, lighting, specialist equipment, lifts and small power). This can be used to evaluate areas of higher/lower energy efficiency and prioritise areas of focus for the Decarbonisation Options Assessment.
Guidance on metering, monitoring and reporting frameworks can be found in the following standards and the relevant links can be found in Appendix 4.
> CIBSE TM39: Building energy metering (currently in revision), which promotes best practice in the design of energy metering and sub-metering in non-domestic buildings
> CIBSE TM63: Operational performance: building performance modelling and calibration for evaluation of energy in-use
> CIBSE TM22: Energy assessment and reporting methodology, which provides a method for assessing the energy performance of an occupied building based on metered energy use and a 'bottom up' assessment of the installed plant and equipment present in the building