Improve Chiller Efficiency at your Central Plant
Chiller Optimization is a lot like what Mark Twain had to say about the weather: "Everyone talks about the weather, but no one does anything about it". However, unlike the weather, something can be done to improve chiller efficiency at your central plant and Progressive Engineering is the one to do it. Progressive has the latest in digital instrumentation
such as ultrasonic flow meters
, programmable data loggers
, recording kW meters
and temperature and humidity sensors
. Our collection of test equipment
is the envy of any large engineering or balancing firm and one that Mark Twain would certainly be proud of.
Chiller Efficiency Problem - Bad Assumptions
It's interesting, even alarming, how much money is spent replacing chillers in the name of energy savings using calculations based on nothing more than assumptions. And who provides the assumptions? The chiller salesman, of course! Not surprisingly a lot of building owners and managers are skeptical of these favorable pay-backs projections. And who knows, there could be a lot of lost energy saving opportunities. On the other hand there are sure to be a lot of happy chiller salesmen.
Most energy savings calculations are based on simple linear projections. For example if you have a chiller operating at .7kW/ton (again a big assumption) and are to replace it with one at .5kW/ton, the energy savings is assumed to be the increase in efficiency times the capacity and hours of operation. However all these assumptions are as wrong as they are simple. For example chiller and cooling tower efficiency, unlike a boiler or pump, is higher at part load. There is such a thing as average load and average efficiency, but that doesn't happen at peak conditions. Therefore you can't tell what the savings are without knowing the part load performance of all the equipment and taking into consideration the number of hours spent at each part load condition.
Chiller Efficiency Solution - Chiller Testing
Progressive uses portable ultrasonic flow meters, kW meters, and temperature sensors to measure everything you need to know about a chiller's operating efficiency. Information is transmitted to a data logger and tracked over a wide range of operating conditions to develop a chiller's performance profile - and the ever elusive, "efficiency curve". Armed with this information, accurate projections can be made and energy savings calculated. Progressive measures and records the following nine points for every chiller we test:
- Chiller Electrical Power (kW)
- Chilled Water Flow (gpm)
- Chilled Water Return Temperature (F)
- Chilled Water Supply Temperature (F)
- Condenser Water Flow (gpm)
- Condenser Water Return Temperature (F)
- Condenser Water Supply Temperature (F)
- Outside Air Dry-Bulb
- Outside Air Humidity
Chiller Plant Optimization Problem - Doing the Best with What You Have
Operating a central plant can be tricky. There are often dissimilar chiller or pump sizes and a hundred different possible operating procedures. For example if you have three equal size chillers is it better to run two at 100% or three at 67%. And what about condenser water temperature? - Is it better to activate that third tower cell to lower condenser water temperatures and save energy at the chillers or would the tower fans consume more energy than would be saved?
Of all the chilled water plants I have ever seen, only one had an optimization routine. Most operators use procedures inherited from the original design sequence, or one modified to meet some particular concern having nothing to do with energy conservation. All this is to say nothing about modifications made to the original system without reevaluating the affects they would have on the equipment or procedures.
Chiller Plant Optimization Solution - Good Information for Good Procedures
Chiller optimization is more than simple chiller efficiency; it's identifying the part load performance for each piece of equipment and determining how these pieces best fit together to save energy. Once this has been determined an operational sequence can be formulated to minimize energy consumption.
Progressive has the means to take the guesswork out of chiller optimization. We will track the operating conditions of your central plant equipment and measure every parameter necessary to calculate individual chiller and central plant efficiency. Why spend money on a new chiller until you know for certain you are getting the most out of the one you have.
Chiller Replacement Problem - Conditions Have Changed and You Have to Adapt
Replacing a chiller is an expensive proposition and shouldn't be entered into lightly. The first, and most important question often goes unanswered: How do you know you need a new chiller? Progressive has seen several instances where a chiller was replaced at great cost when other options were not explored. If you don't know what your current operating efficiency is, how can you tell how much improvement to expect?
In fact, depending on the efficiency curve and hours of operation spent at each part load, it's possible to upgrade equipment and save nothing. All this is to say nothing about equipment sizing or part-load operational procedures that can affect total plant performance.
Chiller Replacement Solution - Good Information for the Right Decisions
When it comes to chiller sizing and replacement, the easiest, and most often employed, is to simply add a chiller -and not surprisingly the simple answer offered by any contractor offering a "design/build solution. It is amazing how willing some owners and operators are to take the recommendation of a contractor - a contractor offering a quarter million dollar solution who has a vested interest in your taking the most expensive option.
There are many options that probably don't receive the consideration they deserve. Progressive has a methodical approach to chiller selection that consists of the following:
- Retro-commission the entire central plant - meaning, test the chillers and make whatever modifications necessary to get the maximum capacity from each piece of equipment.
- Reevaluate the load and plant capacity to insure additional capacity is needed.
- Determine optimal operating procedures to establish how much additional capacity needed.
- Consider alternatives such as re-tubing or re-shelling an existing chiller. Select a chiller that best accommodates the operational strategies mentioned in step three.
You can have the best central plant with the right sequence for a hundred different conditions and it will not perform as intended unless the control system knows what it's doing. For example: A program may see a chiller a fully loaded because it has a ten-degree drop - but if that chiller only has 75% of its design flow it's really not fully loaded. The bottom line is that it's all about control - and control is really about two things: 1) Properly measure system variables, & 2) Have the right operating sequence. At Progressive Engineering & Design we know controls. We have the equipment and experience to improve chiller efficiency and get the most from your central plant.