Rooftop HVAC units are almost always one of the biggest energy consuming devices for any commercial and industrial (C&I) buildings. In fact, C&I buildings consume more than a third of the energy used in first-world countries, and HVAC units account for almost half of this energy. They are also one of the largest contributors to greenhouse gas emissions.
The fact is that rooftop units – or RTUs – hold enormous potential for dramatic reductions in both energy costs and carbon emissions. This potential has gone largely unrealized, however, because RTUs have long been one of the least intelligent of a building’s energy-consuming devices. Yes, there are smart thermostats and building management systems that definitely help, but only to a point because even with these energy efficiency tools in place, RTUs function in isolation, cycling on and off with no knowledge of how and when other units are operating. As a result, RTUs have remained largely untapped as an opportunity for smarter energy management and the accompanying energy savings.
The primary issue is that there is no system-wide coordination of HVAC loads, which leads to an excessive coincidence of loads that naturally occurs given the built-in over capacity of installed HVAC units. This over capacity is designed to help ensure occupant comfort and to accommodate growth in both people and equipment. Redundancy is also built-in so that if one HVAC fails, there is extra capacity from nearby RTUs to shoulder the burden.
Another issue is a lack of knowledge about the group as a whole. Conventional control systems govern cooling for each zone by monitoring their assigned zone and thus have no way of avoiding inevitable situations whereby the majority of RTUs will independently enable cooling at the same time. The implication is that while each HVAC operates independently in a reasonably efficient manner, conventional control systems do nothing to ensure that all HVACs operate as efficiently (and inexpensively) as possible as a group to minimize demand spikes.
If the runtimes of HVAC units could be intelligently shifted by a few minutes here and there and with group dynamics in mind, comfort could be maintained, peak demand could be lowered, and monthly energy bills could be reduced.
A new white paper from Encycle talks about how group control can be achieved leveraging the power of biomimicry. Mimicking communication of honey bees to achieve energy cost savings of 15-25%, this approach enables rooftop units to work intelligently together, replacing the randomness of coincidence wtih a system where controls ensure that only the minimally required load is allowed to run at any point in time and reducing maximum peaks over the course of each cooling month.