In Control of Refrigeration
February 7, 2011
The need for energy efficiency and the desire for intelligent energy efficiency have created a hunger for data. This trend started 10 years ago (or more) in the building controls industry and is now being seen in the refrigeration controls sector.
Data, when properly aggregated and normalized, can create a knowledge base from which good decisions can be made. However, data for data’s sake is just like buying random numbers in a lottery.
So, let’s discuss why data is so desired in the industry today and what technological developments this desire for data is creating and driving.
SAVING ENERGYI think we would all agree that we are trying with great resolve to save energy. But most of the low-hanging fruit in our buildings has already been picked such as lighting retrofits and brick and mortar improvements like insulation, windows, and installation of control systems. So now we need to become more intelligent in order to get to the enticing fruit that is up higher in the tree. Data can be the ladder to that fruit.
By gathering data on our building’s (and building system’s) performance, we can identify hidden areas needing improvement. This drives the development of new algorithms in our refrigeration control systems. That refrigeration technician, who in the past was busy installing new valves and pressure regulators, is now working with things like:
• Baselining, benchmarking and reporting
• Continuous commissioning processes
• Fault detection and diagnosis.
Sure, we are still driving efficiency through mechanical and electrical devices also. There is a growing trend in North America towards the use of case controllers (an application specific device that controls the condensing unit, lighting, fans, compressors, defrost cycles, etc. in a refrigerated or frozen case) and electronic expansion valves. These devices definitely provide an energy savings, and the owner will justify the expense of these items through the calculation of a return on investment.
However, the desire for these devices is often as much about getting data and remote accessibility from the field bus as it is about efficiency. Having an Internet accessible digital controller on your refrigeration rack, as well as on each refrigerated case, has provided owners a new level of sophistication and keeps feeding the data addiction.
BASELINING, BENCHMARKINGSo, let’s answer the basic question first: What are the owners getting from this data? They are getting the power to make better decisions concerning their refrigeration systems and their energy expenditures. Data - once aggregated and normalized - becomes information. Information in the right hands can be very powerful. So, for example, Danfoss Food Retail can take the raw data and transform it into useable information (based on the customer’s needs) and place that information onto a dashboard application that is available on a secure website 24 hours a day, seven days a week. The dashboard application provides graphical representation of their refrigeration systems performance, so it is easy to digest and use.
CONTINUOUS PROCESSWith these advanced tools, we can sustain the energy savings that we achieve during retro-commissioning projects such as the Danfoss program called Continuous Commissioning Processes. Everyone likes to achieve 20-30 percent energy savings from a retro-commissioning of a supermarket, but it is even better to achieve 20-30 percent energy savings from a retro-commissioning project and then sustain that savings over the next 10 years. Continuous commissioning allows the sustainment of the savings by constantly monitoring and maintaining the system remotely.
As we learned in Chemistry 101, entropy occurs naturally. If you don’t explicitly maintain something, then chaos will degrade it. This rule applies to everything, not just chemicals.
The analysis of system faults and the resultant identification of root causes is another tool that can be deployed for the proper handling of data and information. Again, through web-based systems, the supplier of such systems can now act as a forensics team for customers and identify those anomalies that are wasting energy in their refrigeration systems.
This is done by applying advanced algorithms in controllers that utilize domain expertise in refrigeration and isolates clues to a coming problem. By recognizing these clues, determinations can be made and announce, or remotely fix, upcoming issues before they become a problem. This can save customers money by avoidance of emergency maintenance calls and by sustaining energy savings.
TECHNOLOGIESFrom a technology perspective, the ability to get to this data and utilize it appropriately requires some pretty cool technologies. One such technology from Danfoss Food Retail has been Industry Open Protocols. Customers are demanding the ability to pull data and information, and in this instance, data is available via XML attributes in controllers. This is in addition to the ability to provide web access to supervisory controllers.
One objective of new energy efficient and intelligent controls is to allow customers to succeed with their energy, sustainability, and compliance goals well into the future. Data and information are the keys to this success.
Publication date: 02/07/2011