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Energy waste during non-operational hours is easily avoided, so why is it so common? A four-step process to the most cost-effective energy savings.

Jon Thompson

Head of Product Innovation

July 14, 2020

This is the first of a series of blog posts on the most effective forms of energy analysis that can be used to identify energy-saving opportunities. Energy data is an underused resource in building optimisation, as businesses often rush to invest large amounts of money in projects with long and unpredictable ROIs. Proper analysis of a building’s energy data can uncover a vast amount of opportunity to improve efficiency at often very little cost.

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Energy use in unoccupied buildings is one of the most significant and easily avoided forms of waste. We continue to focus our efforts on shiny new technology when energy is being wasted behind closed doors.

We spend most of our time in buildings, almost 100% during the winter months. But we often forget that our buildings are empty or unoccupied the majority of the time. You would, therefore, expect that energy use would reflect this, but you couldn’t be further from the truth.

I’ve heard this period of time referred to in many different ways; non-operational, silent hours, out of hours, quiet hours, overnight etc. I may use them interchangeably but I am always referring to the time when a building is not in use, is almost completely empty of people and should, therefore, be using much less energy than during peak operation.

During operational hours you have a multitude of factors to balance to ensure a comfortable and healthy space that can change hour by hour. When the building is closed, it should simply be a case of turning everything off that doesn’t need to be on. In reality, this is more difficult than it sounds.

Without a doubt, the biggest culprit is the Heating Ventilation and Air Conditioning (HVAC) system. Not only is it commonly the most significant energy user, but it’s also invisible. It’s very difficult to leave the lights on overnight without noticing. Plus your parents have been telling you to turn them off when you leave a room since you were 7. But with HVAC, it’s far less obvious. The building is a reasonable temperature when you leave and again when you come back the next morning. The illusion of a building with no lights on creates a false sense of security.

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Why do we continue to spend money on new technology for leaky buildings?

Implementing energy conservation measures at a building that is wasting energy overnight is like trying to fix a leaking bucket by adding more water. At first, we must focus on eliminating all sources of unnecessary waste.

The challenge is that it requires more thought and a better understanding of building performance than it does to sign off the installation of £80k worth of solar panels or LEDs. The upside is that it’s usually extremely low cost, if not free. At most you’re going to need to repair or upgrade basic controls equipment or invest time in educating staff on the importance of an effective shutdown.

I can’t tell you the number of times I’ve been asked to quantify the financial benefit of an energy-saving measure for a site wasting a considerable amount of energy overnight. An absolute classic I’ve seen time and time again is when the firm who carry out the install override the time clocks to work overnight. Several months later, when I’m asked to measure the savings, the increased overnight load has neatly cancelled out any energy savings resulting in a return on investment of zero.

Why is so much energy wasted unnecessarily?

I believe there are two causes of wasted energy in buildings. Accidental waste which occurs unconsciously and results from poor control over main building services. And deliberate waste, which is usually a side-effect of priorities being consciously placed elsewhere.

Accidental or Unconscious Waste

Insufficient or non-existent control over major building services is the most common reason for energy waste in buildings. As humans, we are over-reliant on technology to control our buildings. Even a sophisticated Building Management System (BMS) will you let you down if you rely too heavily on its ability to run main building services effectively.

Actuators break, time schedules are overridden and equipment is even accidentally disconnected from the system so will run continuously. A common approach is to ‘engineer out’ the need for humans, which makes sense, but with no active monitoring or visibility is a recipe for disaster.

Poorly configured time schedules are also a serious problem. One size fits all schedules are programmed by the engineer who installed the system with no knowledge of how the building will be used. When the building is commissioned and handed over, the schedules seem to do the job so that’s how they stay. “If it ain’t broke don’t fix it!”

In smaller buildings, the main challenge is managing equipment without central control. You’ll often find restaurant managers attempting to program 8 independent split AC units made by as many different manufacturers. The responsibility to make sure everything is switched off usually falls on the last staff member to leave the building. But this usually comes second to closing down as quickly as possible after a long shift.

The ‘control fallacy’ is a term I use to describe the irrational approach many building managers take when discussing non-operational waste. There is a strong assumption that when a building is unoccupied, it will not use any excess energy. But this only happens with extremely tight control procedures and relentless monitoring. I’ve had countless discussions with building managers who are adamant that their building is not using energy out of hours. Without the data to back it up, they have based their argument on the disbelief that anybody would be heating or cooling an empty building, especially them.

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Deliberate or Conscious Waste

The role of a facilities manager is to make sure their building functions well enough for the people who occupy it to do whatever it is they need to do. At the most basic level, this involves making sure the lighting is sufficient, the temperature is comfortable, the space is clean and the air is reasonably fresh. Energy efficiency has progressively become a bigger part of a facilities managers role as businesses have started to understand the benefits. But let’s get something straight; When an FM receives 46 emails before 11am about the temperature being too hot or too cold, energy efficiency goes out the window.

We’ve all become far too sensitive to temperature in buildings. A 1°C change is enough to cause chaos in an office environment. You either have half the occupants complaining they’re too hot or the other half complaining they’re too cold. A change either way usually results in an uproar.

The FM faces a seemingly impossible task. So instead of balancing comfort with energy efficiency, they run the building to maintain comfort at costs. This is why you often see air handling units running for extended hours or even all night. To avoid complaints, the facilities manager sets schedules far in excess of what is necessary with no idea how much the additional energy is costing their employer and the environment.

The problem is that energy efficiency is seen as an alternative to occupant comfort and well-being, which is simply not the case. It is vital to find a balance between the two. To meet the requirements for comfort and well being whilst using as little energy as possible.

Data changes everything

As I mentioned earlier, you can’t ‘see’ a heating or cooling system working. It’s very difficult to tell if a fan coil unit is operating when it’s 5 feet above your head, let alone it’s heating or cooling. The only way to determine exactly what is running overnight and how much energy is being wasted is by analysing a building’s energy data.

Fortunately, most commercial buildings now have AMR (Automatic Meter Reading) meters that provide electricity and gas consumption data at half-hourly intervals. Data at this granularity allows analysts to split the operational usage from non-operational usage, compare the two and observe how it changes day to day and over longer periods of time.

Of course, submetering data or a feed from the BMS is excellent when determining what equipment is running at what time. But main meter data is more than sufficient for analysing the extent of the problem and where more granular data is needed.

As an energy analyst looking at a new portfolio of buildings, the first thing I’d do is run some tests on non-operational usage. I’d consistently find savings of at least 5-10% due to poor control out of hours.

Through an analysis of half-hourly energy data, it’s possible to determine an achieved level of non-operational usage. Observing how far a site deviates from this level over the course of a year will indicate how tightly it is controlled. Additionally, how this value changes across your portfolio can be very insightful.

A four-step process to the most cost-effective energy savings you’ll ever make!

Step 1 - Find your achievable base load

Step 2 - Estimate your optimum base load

Step 3 - Calculate wasted energy in the context of each base load

Step 4 - Communicate your findings

I’ll be diving deeper into each of the steps next week. Stay tuned to find out how you can use this approach to uncover energy-saving opportunities for your business!

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