Mechanical engineer Steven Mantine provides a few quick and easy steps to immediate energy savings without the hefty price tag.
Nowadays we always try to reduce and optimise the energy consumption of HVAC systems. It is an easy win for everyone because HVAC systems consume the most energy of all the equipment at your facility.
By upgrading to a newer, smarter system we could reduce consumption significantly but in the age of COVID-19 budgets are tight. A shiny, new HVAC system may not be a priority but savings always are so let’s take the cheap and easy eco route.
The first step is getting an understanding of current energy use throughout the day. Create your own energy consumption graph to get an understanding of usage.
Analysing the graph will highlight the load point during the day.
By understanding the graph, we can identify a few simple methods to save energy.
One of the most commonly effective and simple ways to save energy is the use of off-timers. An off-timer at the end of the working day prevents units being left on to operate overnight when they are not required. We can do it even smarter.
In some of the projects I have dealt with in some of the offices that had a dynamic behaviour (changing from occupied to unoccupied on a rapid basis), from a specific time in the afternoon (for example 1 PM) the unit would get an “off” signal.
If the users are still in the office and wish to operate the unit, they can do it from their local RC. If they left earlier for a meeting outside, that would save us energy. After a certain hour, we will turn all the units off and prohibit the local operation to verify the system will stay off after the working day.
Some of the newer systems have a timer optimisation feature embedded in them,nevertheless, even if we don’t have this feature, we can save energy with a little trial & error. For example, often there is a peak at the beginning of the day as most of the indoor units start working at once and demand for cooling is high. In relation to our electric program with our supplier this peak might be at a very high rate we would like to avoid.
The way to overcome it is to gradually start the system before the working day starts. This way the heat load is low, and it will be easier and cheaper to achieve the desired temperature at the desired time. How much earlier varies between projects which is why trial and error is necessary.
There are times when energy is wasted by providing HVAC support in unoccupied spaces this may be due to forgetting to turn off or underestimating absence time.
Connecting an IR sensor that turns off the unit after 15 minutes will save you money. In research conducted by the Bavarian Environment Agency, they concluded that this single method can result in savings as high as 30 per cent compared to regular use.
As we need to reduce the night load some of the systems has a Setback function. This function will keep the conditions in the building in specific areas, creating boundaries. The system will remain off as long as the temperature stays between the boundaries we set. Once the boundaries are crossed, the system will re-set itself to stay within the boundaries that have been set.
For example, in the summertime, we can decide that the max temp in the building should not exceed 28 degrees. As long as the temperature inside the building stays below 28 degrees the system will stay dormant, once the temperature goes above 28 the system will take steps to stabilise the cooling in that specific area.
Peak cut control
Depending on your program, high load during the day can come with at great cost. Peak cut control enables you to limit energy consumption to a specific value, e.g. 70 per cent from the regular max energy consumption for a certain time.
By using this method some energy companies even provide incentives. We can apply this principle by increasing the water target temperature in chillers. By doing this, the trade-off may be improved occupant comfort.
Indoor unit control
To complete peak cut control, we might want to change the indoor unit’s settings to deal with the capacity drop. There are few methods available. One option is to increase fan speed. In some of the systems with this embedded function, the system can cycle the capacity between the indoor units and compensate for comfort and lack of capacity.
Even with little means, we can apply simple methods to deliver big energy savings. It is also important to use the system properly by shutting doors and windows, shading high solar radiation areas and shutting the unit when leaving the room.
It is also important to ensure equipment is well maintained as faulty pumps, inaccurate thermistors and poor insulation can be costly.
A side note, some of the newer systems have more advanced features that can produce even greater energy savings without compromising comfort. If you have a modern system, it is worth finding out what energy saving features are built-in to the system.