Improving Data Center Energy Efficiency: Monitoring Based Commissioning

Welcome to this weeks post in the commissioning series.

Monitoring Based Commissioning refers to the approach that involves: Energy/Building Management solutions, Retro commissioning, and continuous commissioning and measurement based savings using the metered and monitored data.

Being able to couple monitored data with a commissioning plan provides us with a few advantages. First, we are able to do benchmarking at the beginning of a project so we can have data to reference when a plan is complete to provide a "before and after" comparison. Second, it can help identify patterns in usage, optimum performance, and when changes occur that deviate from the plan. Lastly, data can be used to prove whether a proposed change had a positive or negative effect on a given system.

At the beginning of any commissioning plan you will need to gather data to provide a current usage of a system under normal operating conditions. That is benchmarking. Normally in the beginning of a commissioning plan there are no permanently installed devices that give this data. External and independent manual meters can be used for whatever device is appropriate. By this time in the commissioning plan there should be permanently installed meters and sensors that you can go to and see real-time data. Those meters and sensors will hopefully be feeding a BAS, DCIM, or some other software that will aggregate that data and organize it for easy viewing. Like we talked about last week, the speed and convenience of having that data in one location is extremely valuable!

Any good management software will show real-time demand data and organize it over time to show consumption. With that historical data we can analyze trends to differentiate between normal operation, a possible fault, changes to settings, new equipment installs, etc. In a perfect world everyone would be aware of all these dynamic changes, but the energy manager may not know what has happened elsewhere. Sometimes energy managers will just know that a deviation has occurred and then they have to find out why and then make a decision of what to do.

Planning out what impact a project will have is necessary to get executive "buy in" on a project. If you were to make a claim that switching out all the fixed speed fan motors in all the CRAC units with EC fans will net a 10% energy savings you have to know at least two things. The consumption of the fixed speed motor fans before and the consumption after the EC fan install. Metering at the individual unit on a shared panel or having a dedicated mechanical panel will provide that data. This data can be used to prove or disprove that your plan met expectations. Something popular right now in the industry is the raising of the intake temperatures at the equipment intake to the ASHRAE recommended 80 degrees. With the appropriate metering on the power consumption of all the HVAC units and the data from the temperature sensors themselves we are able to raise the overall temperature and use the data collected to see if we gained a positive or negative effect on energy consumption.

In summary, combining monitoring with a retro commissioning plan will get the systems back at optimum efficiency. Using that same data you can develop a continuous plan to maintain close to that optimum efficiency over the life of the entire life of the facility.