11-Day Energy Audit Reveals Long-Term Savings Opportunities

Hello, Champions of Net Zero!

In an age where energy efficiency is paramount, especially for institutions like schools operating on tight budgets, the significance of power and energy loggers (PELs) cannot be overstated. These devices not only track energy usage but also illuminate inefficiencies and pave the way for substantial cost savings. Yet, the real question remains: how do they perform in everyday scenarios? Julian Grant, the General Manager at Chauvin Arnoux UK, offers us a glimpse into the practical insights gained during an extensive 11-day energy monitoring session at a secondary school in Kent.

For most organisations, managing finances wisely is crucial, but schools often face some of the strictest budget constraints. With energy bills consuming a significant portion of their financial resources, it becomes imperative to maximise every pound spent. This critical need for efficiency is why we partnered with a secondary school catering to 700 students to conduct a comprehensive energy audit. Our mission? To unearth opportunities for enhancing efficiency and reducing costs.

The school’s governing body was eager to implement changes, and we opted to install a Chauvin Arnoux three-phase power and energy logger at the school’s main incoming supply. This advanced device would provide us with the necessary data to pinpoint areas where improvements could be made.

Designed with flexibility in mind, this innovative data logger features adaptable current transformers, clamp-on connections, and a magnetic base for swift and straightforward mounting. Thanks to its thoughtful design, the logger was installed with minimal disruption to the school’s daily activities and was left operational for eleven days, capturing data across both school days and weekends.

The results were both enlightening and actionable. Among the most significant findings was a considerable imbalance in phase currents, as illustrated in the accompanying data visualisation. The peak current on one phase reached a staggering 219.2 A, compared to 172.8 A on the second phase and 150.3 A on the third. This disparity underscores an issue with the school’s predominantly single-phase loads being unevenly distributed across the phases, which is undesirable. Such imbalances can escalate current levels in the neutral conductor, leading to excessive heating. Moreover, current imbalance may induce local voltage inconsistencies at various points in the installation, potentially compromising the efficient operation of three-phase loads, such as motors.

In addition to the phase imbalance, we also detected high levels of harmonics in the supply system. The data revealed particularly elevated levels of the third and fifth harmonics, a finding that aligns with the increasing prevalence of ‘electronic’ loads in contemporary educational settings. Devices such as personal computers, office equipment, and LED lighting are known to contribute to the third harmonics, while uninterruptible power supplies (UPSs) and servers frequently generate fifth harmonics. It’s essential to note that while harmonics are common, they can pose risks, including unexpected heating in neutral conductors and interference with the proper functioning of sensitive electronic equipment.

Perhaps the most surprising revelation from our monitoring was the out-of-hours energy consumption. As anticipated, peak current usage coincided with regular school hours when the building was occupied. However, what stood out was that, even during evenings and weekends when the school was closed, approximately 30 A per phase continued to be drawn. While some of this consumption is attributable to essential services such as emergency lighting, the overall figure was unexpectedly high.

The school took the initiative to investigate this out-of-hours usage and discovered that portable electric space heaters, employed to supplement a poorly performing HVAC system in specific areas of the school, were often left running overnight and over weekends. This scenario exemplifies a classic zero-cost energy-saving opportunity. The solution? A simple yet effective nudge for teachers to be more conscientious about switching off heaters at the end of the school day.

During the monitoring period, we also evaluated the power factor, which remained robust throughout, showing little scope for further enhancement. This is likely due to the school having few inductive loads, balanced out by capacitive loads such as LED lighting. However, it’s vital to remember that in other environments, including different educational institutions, the circumstances could vary significantly. This highlights the importance of carefully monitoring power factor results during any energy audit.

This data logging exercise yielded actionable insights that promise considerable benefits moving forward. The immediate step of turning off portable heaters outside of school hours has already been implemented, although it is a temporary measure. In the long term, the school anticipates far greater energy savings through the upgrading of its HVAC system. The objective is to enhance overall efficiency to a level where portable heaters are rendered unnecessary. There may also be other superfluous out-of-hours energy draws, such as lights and computers left operational when no one is present. The school can further explore straightforward solutions, like installing occupancy sensors for lighting and timed switches to ensure computers power down automatically at the end of the day.

Addressing the high levels of harmonics is another critical step. Understanding the individual sources of these harmonics and implementing filters where necessary will result in cleaner energy supplies, reduced cable heating, and prolonged equipment lifespan.

Finally, the school should consider redistributing single-phase loads across the power system to achieve a better balance between phases. This adjustment would mitigate heating in neutral conductors and facilitate the efficient operation of any three-phase loads in the system.

The monitoring of power quality and usage at this Kent school proved to be a straightforward, low-cost endeavour that had no adverse impact on day-to-day operations. What it provided, however, was a wealth of invaluable insights that will empower the school to utilise electricity more efficiently and reduce its energy expenditures. So, to address the initial inquiry: Are power and energy loggers beneficial in real-world settings? The answer is a resounding yes. They are an incredibly effective tool for identifying energy-saving opportunities and enhancing overall efficiency.

Stay tuned for more insightful updates and practical solutions as we continue our journey towards a sustainable future!