EWChillerPlant
  Chiller Plant Optimization

EWChillerPlant is the first in a series of EnergyWitness™ optimization modules. When optimizing a chiller plant you need to work towards a goal—something you can measure and verify. Of course, that goal is to reduce energy consumption and operate at the lowest cost, but always maintain space comfort. EWChillerPlant provides hourly operating costs for the chiller plant, each sub-system, and each component—updated every 15 minutes. You can see exactly how well your plant operates on a cost basis, and immediately see the impact of control changes or other maintenance work.


Operators can move through time (1), and see data for each system and the entire plant (2). Bypass flow (3), energy rates (4), and weather data (5) are shown. A tab (6) switches the view to show the underlying models. Gauges show total cost in $/hr and $/ton-hr (7).

Chiller Plant Cost Speedometer

The first of two views of the chiller cost data is the cost speedometer. It provides a summary report of the hourly cost of operations for the whole plant and each major sub-system (chiller, cooling tower, etc.). The system recalculates each cost every 15 minutes based on the plant's operational data for that interval.

The speedometer also supplies unit-based measurements (kW/ton, $/ton-hour) that provide additional at-a-glance information. For example, two identical chillers running at very different costs/ton may point to an issue that needs attention, or, if running gas and electric chillers you can instantly see which is more cost effective on a per-ton basis.

The Cost Model

Each facility's plant is different, and so EWChillerPlant is configured for each installation. IDS works with each client to build the model in Excel using a template. This ensures the model is a complete and accurate representation of the plant. The models account for every piece of equipment from chillers and cooling towers down to fans and pumps.

Models include a series of engineering calculations, such as chiller efficiency, evaporator BTUs, condenser BTUs, motor brake horsepower, motor energy, steam energy, make-up water BTUs, and more. The cost calculations are then based on the client's utility rates, taking into account on/off peak rates and changing fuel prices. Each calculation not only drives the speedometer, but is saved as historical trend data.

Historical Cost Trends (and other calculations)

Powering the snapshot view of the speedometer is a complete set of trends. Each value displayed in the speedometer report, every equation in the underlying Excel models, and a few other calculations made along the way, are all stored in EWDataWarehouse, providing historical trend data for all the engineering formulas and operating costs.


Cooling tons output shown at 15 minute intervals for each chiller. In this case, chiller 1 (green line) is well below its rated capacity.

The cost/ton calculation shows, in this case, chiller 1 (gas, light blue) costs about 35% as much to operate as chillers 2, 3, & 4 (electric, dotted) during peak hours.

You view and interact with these trends in EWViewer, just like any other data points. Combine them with any other data from the warehouse. Move through time. Easily see daily/weekly/monthly patterns. Use them within your diagnostics and monitoring efforts. That's actionable information! And once you do take action, you'll begin to see at the next 15 minute interval how you've affected efficiency and cost. That's right, immediate feedback on how control changes, maintenance, etc. affects operating cost.


Speedometer tab showing systems that make up the plant, and property box showing equipment details for the item selected in the data tree (a York gas chiller).

A data tree tab is devoted to the speedometer calculations. Each site will be unique based on the equipment configuration and building automation system(s). In the example on the right you can see folders for each chiller, cooling tower, secondary pumping system, and the total plant. Available trend calculations within each include items such as pump brake horsepower, efficiencies, flows, tons output, cooling tower fan kW, cooling tower makeup water, and of course, costs.

Hourly operating cost data exists at three levels—the chiller plant total cost, a total for each system within the plant, and finally at the component level. For Chiller 1 you can see hourly costs for the chiller engine, chilled water pump, and condenser water pump in addition to the total for that chiller..

The Power to Optimize

It's a whole new way to monitor, manage, and optimize your chiller plant. Engineers don't have to spend hours or days collecting the underlying data and running spreadsheet calculations (although if you do have some favorites we don't cover, you can drop the data into Excel and go to town or add your Excel models to EnergyWitness through its plug-in architecture).

EWChillerPlant calculations often make smaller problems readily apparent, for example, a production balance equation that generates impossible numbers likely indicates sensor problems that might have gone unnoticed looking at the point data (we've seen clients put projects on hold until they could service all the sensors that needed to be fixed or recalibrated).

All the data and tools are there for diagnosing issues by drilling down through the underlying calculations and individual points to find the root cause of the inefficiencies. Some people would call this data mining or business intelligence. We call it results.

Show Me How I can Optimize My Chiller Plant

Want to see what it looks like to know exactly how efficiently your chiller plant runs, and just how much it costs to run? Give us a call at 617-744-1091, or send an e-mail to info@intdatsys.com to arrange a demo.

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