Reducing energy costs and pollution emissions involves many areas within an industrial facility. My studies have found key (or common) areas where low cost practical projects can be implemented. Combined, these projects provide savings exceeding 10% of the annual energy spend with an average payback of less than one year.
Preface: Metering is an area that many industrial facilities fall very short on. Everyone has heard the saying: “You can’t control what you can’t measure.” I’ve added an additional one: “Measured data is of little use without qualified analysis.”
I am just completing a detailed study of a large plant located in Novy Jicin, Czech Republic. This plant has more than 30 buildings, 4 large manufacturing halls, a central heating boiler plant, and miles of steam and compressed air distribution lines. Without metering, this project would have taken months of measurements and even then there would be many estimations. A few years ago the plant had installed metering to measure the energy into each of the main production halls and to the air compressors and gas boilers. They had hourly data available that could be trended, compared to weather, and analyzed against production levels. With this information and a week of on-site assessments, we were able to identify and define more than $1.4 million of energy-saving projects totaling 15% of their total energy spend.
In this article I would like to describe what I believe are some key metering devices and measurements that each facility should have to effectively manage their energy usage.
The Big Picture
Starting with the big picture there should be an organized data table of the monthly energy usage, cost, production measures, and weather data. This simple table below has proven to be a very useful way to organize this data. It allows you to look at year over year month to month comparisons and to see a lot of data on one page. Production measures can be anything from direct labor hours, parts produced, pounds produced, or $ sales. Some plants use a more detailed level by using $ sales minus the cost of material or in other terms the value add.
The second level of metering and one of the most important to begin the detailed analysis necessary to identify projects and to validate the results is interval data. Interval data for electricity would be 15 or 30 minute electric demand or energy measurements. Most often this is available directly from the utility company. In some cases you would need to pay a monthly cost for using the service and the electric company may need to install a different type of meter. You may also have to provide a telephone line to the meter. I have found this to be the most valuable tool to-date in identifying, quantifying, and verifying project results. The data is most useful if it can be read by a computer in almost real time. Our memories are not always so good so if you are looking at one month old data it may be difficult to remember exactly what event caused the change on the graph.
If you cannot get the data from the utility company I have found a supplier who makes a relatively low cost solution that allows you to collect interval data from the electric meter, and then even add additional data measures which are then sent to a computer for real time monitoring. (www.kwhtools.com)
Here is a graph from interval data that I’ve collected from a factory. I’ve taken the data and color-coded it to show the different tariff rates. The color red represents the highest cost electricity and therefore is the area we begin analyzing to determine how to reduce the use during this period. Production levels are overlaid with the interval data. This measurement is an excellent management tool for Monday morning staff meetings. Targets are set in relations to production levels and then the targets are reviewed during the meeting to make corrections or set new targets.
The next level of measurement is for plants that use a significant amount of natural gas. Many gas suppliers are now able to provide interval data, sometimes hourly but most often daily. Using gas interval data along with daily weather data a very useful correlation can be developed. It can be quickly determined how sensitive the facility is to outside temperature changes by noting changes in the gas usage. Plants with large exhaust systems or rapid air changes will see gas usage rise very quickly when the temperature drops.
If your facility has multiple buildings of a significant size then besides having interval metering for electric and gas at the main entrance meter the same should be set up for each of the other main buildings. This is referred to as sub-metering.
Sub-metering with Data Loggers
There are many ways to sub-meter. I will focus on a low cost method that I have been using for the last 10 years with great success. I have been using small data logging devices called Hobos and have distributed thousands of these devices in plants around the world. (Refer to www.microdaq.com)
The small data logger (Hobo) can measure light, relative humidity, temperature, and also one additional probe such as a current transformer. For around $250 USD I can measure four different items either separately or at the same time. It seems every month new items are being developed that can work with this data logger. I like having one device, with one program that I can use.
My primary use of these devices has been to measure electric current. I use the data logger along with a current transformer to measure one phase of a motor or heating circuit. The batteries in the data loggers last for about a year so I install the units and take the readings monthly or more often if I am studying a piece of equipment. The data loggers can take inputs form 4-20 mA signals, pulse signals, and 0-5 Volts allowing for a good variety of potential inputs.
Items to sub-meter on a continuous basis: Main energy using buildings (electric and gas) , air compressors, chillers, large steam or hot water boilers.
I use data loggers to analyze individual machines as well as sets of similar machines. Nearly half of all the savings that have been identified by attendees of my workshops have been identified and quantified by these data loggers.
I’ve found a new device for measuring compressed air flow to a piece of equipment using the data logger to graph the data over time. Recently this device has help avoid buying the wrong sized air compressor for a production line. We installed the device on an operating line and monitored the flow for a full week. From the data we were able to determine the correct amount of air that was needed. Since this device was easy to install and remove, we are now performing a similar test at another plant.
Another measurement device I have recently began using is a thermal imaging camera. I had no idea what I was missing out on until I begun using this device. The price has come down significantly and with this $3,000 camera (reference: www.extech.com) I been able to enhance plant audits and maybe more importantly provide stronger evidence to plant management on their need to change. It is very hard to argue against a picture that shows cold air coming into a negative pressure building, an exhaust fan left on when the heating system is running, or heating units blasting away in a warehouse with the door open and no one in the area. This device provides a method to quickly scan a large area and identify motors that are left running and hot water heating systems that are not fully isolated.
I’ve recently put together a tool-box of containing a set of useful measurement devices for analyzing a plant. The box includes 21 data loggers with current transformers, 3 data loggers with occupancy sensors, 4 simple data loggers that measure when a motor is on or off, a hand held light meter, and the thermal imaging camera. I found a great shipping box that protects all of the items even in with the rough airline baggage handling. (Reference: www.techtoolsupply.com) Some clients have been renting the box but are now wanting their own box and they are sharing it among their other plants. It cost about $8,500 for the total set but has become an invaluable tool for metering, identifying, and quantifying energy cost reduction projects.
In summary: In this article I did not delve into calculations for savings but focused primarily on useful tools I have found to enhance the projects that were discussed in previous issues and will be discussed in future issues. My suggestion is not to wait until you can get an approval for a plant wide integrated metering system. Begin with the basic measures described above and enhance it with some portable metering. Identify and implement good measurable energy projects, show the savings, and use this to support projects for a more automated system.
Thomas Mort is the Chief Operating Officer of Mission Point Energy.