Poor Heating Controls - Real World Findings

Researchers at MIT estimate commercial buildings account for 20% of all the energy used and conclude that as much as 30% of that energy is wasted during normal day to day operation. Generally, in commercial buildings, energy expenditure is an outcome of business operation and the productivity of occupants is the desired outcome. Comfort and climate control are a key aspect of maintaining productivity in an office building, but what if you could maintain that comfort while reducing energy consumption by 20 or 30 percent?

Tracking energy and operational data within a building is the first step to identifying where to make improvements. With a data driven approach it is easy to make appropriate changes in operation of equipment and ensure no negative impacts occur as a result of these measures.

As a real world example to demonstrate this, take a look at the following scenarios discovered by OPNBuildings in heating systems over the years.

Worst

It is fair to say that the worst case scenario for energy wastage in heating systems is straightforward and one which should not really happen but from our experience these events can occur quite often and without anyone knowing for months on end.

In the below screenshot we can see that the boiler system has lost control and is in a constant state of running. The flow temperatures are at setpoint 24/7 and the return temperature is quite close to the flow indicating little to no demand for the system to be running. It is likely that the system was put into manual on and forgotten about.

Better

Continuing on from the above example significant savings can be made by taking a data driven approach. By getting systems back in control and then taking a measured approach building operators can assess appropriate startup times and shutdown times for heavy consuming boiler and chiller systems.

As an example, looking at the below profiles we can see that the start time of the boiler is at 4am in the morning, yet by looking at the indoor CO2 and temperature data we can also see that occupancy doesn’t start until 8am and temperatures are not significantly low around this time either. Therefore it would be reasonable to delay the start up time of the boiler system by a few hours to save on unnecessary heating during unoccupied times.

Furthermore, the heating here is in the summer months with outside temperatures relatively high so it would be worth exploring and implementing an optimised start and stop strategy as well as outside temperature holdoff control.

Best

However, the most impactful and transformative approach to heating and cooling system control is to take a demand driven approach. This can result in significant savings and a truly energy efficient control system. A simple implementation of demand driven heating is to make the operating schedule the secondary control factor, whilst demand for heat becomes the primary driver for heat generation. The level of demand is gauged by the heating signals across the building, such as valves on FCUs, AHUs and Rad circuits. Using these valves to create a heating load signal for the building as a whole can enable the boiler system to fire only when needed.

PS - Domestic Hot Water generation is one of the main reasons why boilers operate, most often inefficiently at low loads, throughout the warm summer months. Switching to electric heating is one approach to deal with this. A more fundamental approach is to assess your overall hot water load and identify where local electric heating can be used to satisfy demand, such as under sink heaters and electric showers. Thus moving away from the concept of large DHW storage and all the concerns with legionella that go with it.