EKG For Refrigeration Shows 10% Energy Savings
Trusted data from the physical world.
Refrigerators and HVAC are one of the biggest consumers of electricity in commercial and residential settings. Yet they are often one of the most neglected pieces of equipment, operating thanklessly until they fail and wasting money in the meantime.
Studies indicate that regular maintenance of a refrigeration system can deliver energy savings of 10-15% and extend service lives by up to 20%. But knowing when specific equipment requires maintenance and the impact of that maintenance is often a guessing game because there is a lack of supporting data.
What is needed is a more intelligent measurement system that can cost effectively analyze sensor data in real time and deliver timely knowledge about the health of a specific piece of equipment.
EKG for refrigeration
In this project we use low cost sensors connected to real-time analytics in the cloud to measure key parameters within a consumer refrigeration system and to compute a simple health indicator that can be used to direct maintenance resources.
We started with the basic premise that some data is better than no data and that by monitoring the heartbeat of the refrigeration system we could derive useful knowledge. Measuring how hard the compressor is working to hold a temperature is an indicator of system efficiency: the harder it works for given ambient condition, the less healthy it is. Knowing this single fact can support fundamental decisions about where to apply precious maintenance resources.
'Heart rate' reduced by 11% after cleaning
The condenser is the part of the refrigeration system where heat collected from the load (the goods in the refrigerator) is transfered to the ambient air. It relies upon forced air flow to move cool air in over the coils and warm air out. If that air flow is restricted then the transfer of heat is restricted - much like a down jacket keeps you warm by obstructing the flow of warm air from your body.
Not surprisingly then one of the first items on any routine maintenance schedule is to clean the condenser coils.
By cleaning the coils with a vacuum cleaner we saw an immediate 11% improvement in the overal efficiency of the system. The compressor had to work 11% less to remove the same amount of heat from the system. That result is consistent with the third party studies mentioned earlier.
Measuring and analyzing the data
We used four digital temperature sensors fitted at strategic points within the refrigeration system and connected to a Zymbit data acquisition module that transmits data securely to a timeseries database in the Zymbit cloud. Data was analysed continuously using an application specific algorithm developed in numPy to compute a health indicator.
Real time data charts made it easy to review the historical performance of the system. In addition the system can be configured to automatically detect anomalies and to trigger notifications and other actions.
Whats the payback ?
For a typical restaurant kitchen with a walk in refrigerator, walk in freezer and four refrigerators, the payback period for a machine health service can be as low as 12 months.