When doing an energy audit, you always want to find the quick payback projects. Often- these are the simplest ones, such as eliminating a waste stream or other ideas that require no upfront capital. But how do you find these?
A Useful Search Tool
One tool that can give you a “hint” regarding what types of opportunities typically exist in your facility is the IAC Database, which has data from 16,000 different energy assessments, collected over decades via universities across the USA. The Industrial Assessment Center database contains over 124,000 recommendations, which are organized (and can be sorted) by payback period, implementation rate and other metrics. The database documents the progress of a highly successful Department of Energy program that is primarily intended for manufacturing facilities, but I have found it useful in hospitals, universities and other clients with similar buildings. Figure 1 gives you a screenshot of the search engine, which can be found here: http://iac.rutgers.edu/database/
Let me give you an example of how to use this tool. Lets say you were doing an audit of a facility that had a steam system and a compressed air system. Within the database, you could look at all the energy saving recommendations relating to those two systems and see the economic paybacks, organized by payback period, savings, geographic state, etc.. So, lets assume you choose a recommendation such as “reducing compressed air pressure” (which has an Assessment Recommendation Code = 2.4231). As Figure 2 shows, this recommendation usually yields a payback less than one year and approximately a 50% implementation rate.
It might require 15 minutes for you to explore the website and learn how to use the tool, but it would be worth doing. If you look at the data from thousands of facilities from 1994 through 2014, fixing leaks (steam or compressed air) offer the quickest paybacks (usually less than 6 months). Fixing compressed air leaks also has an 84% implementation rate, which indicates how many IAC program clients actually implemented recommendations made by the universities. This is measured by a follow-up survey, conducted 6 months after the energy audit.
Using the IAC database, you could do research on many recommendations and get a basic understanding of their feasibility. If you are a manufacturer, you could request an energy audit if an IAC is located near you. Locations are listed here: http://energy.gov/eere/amo/locations-industrial-assessment-centers In any event, the IAC database can be used as a “pre-screening” tool, before you do the on-site audit.
Common Sense is not that “common”
When I do energy audits, as a “bell weather” indicator, I ask the facility manager to tell me about their “leak repair program”. If the facility manager has air compressors or boilers, yet doesn’t have a leak repair program (with inspections about every 6 months or less), then usually I will find an improvement opportunity. It is not fair to say that “common sense is not that common”, because anyone can be easily overwhelmed within today’s digital information flow rate. However, fixing leaks is analogous to stopping bleeding in an emergency room… it is important. To get this on the “radar screen” of a facility manager and occupants, we simply have to communicate that leaks represent bleeding dollars (profits), and that can mean potentially lost salary raises or even jobs. When occupants take the “bleeding” seriously- onsite staff will direct you to where the leaks are happening. If you need tools, an ultrasonic leak detector with headphones can help… and it wouldn’t surprise me if someone develops an “APP” to do that someday.
Estimating Savings from Leaks
Once you find the leak and “estimate” its size, then you can use a variety of charts to approximate the savings. It is OK to be a little conservative (maybe guarantee only 80% of the savings projection) because the paybacks will still be very short. Below are some commonly used charts (so commonly used, I could not find a reference source… but they have been applied for many years with few complaints). Additional charts and software are available online and you may want to visit http://www.compressedairchallenge.org if you want to research further.
The Compressed Air Leak chart below expresses “savings” in kWh, so the average efficiency of the compressor is already factored in.
If you found a 1/8 in air leak at 100 psig, then the annual savings (@ $0.10/kWh) from plugging the leak would be:
=$2,310 per year
Even if it takes $200 to repair the leak, then the payback would be $200/$2,310 = less than .1 years!
Figure 3. Compressed Air Leak Costs (at 8760 operating hours per year)
Steam Leak Savings Example:
The Steam Chart below shows the energy lost at the point of the leak, so to determine savings, you must incorporate the efficiency of the combustion to determine the amount of energy required to “make up” for the losses. Because the efficiency of combustion is always less than 100%, it takes more energy to “make up” for steam losses. Beyond the savings indicated below, there would also be water, sewer and chemical treatment savings from leak repairs.
Assuming you had a boiler that was 80% efficient, if you found a 1/4 inch steam leak at 110 psia, then the annual savings (@ $5/MMBtu) from plugging the leak would be:
=[(2,000 MMBtu/year)/(.8)] * [($5/MMBtu)]
=[2,500 MMBtu per year is what Boiler would need to “make up”] * [($5/MMBtu)]
=$12,500 per year.
Even if it takes $500 to repair the leak, then the payback would be $500/$12,500 = less than .05 years!
Perhaps these quick survey tools will be helpful for your next energy audit… and remember to always ask about compressed air and steam leaks.
Eric A. Woodroof, Ph.D., is the Chairman of the Board for the Certified Carbon Reduction Manager (CRM) program and he has been a board member of the Certified Energy Manager (CEM) Program since 1999. His clients include government agencies, airports, utilities, cities, universities and foreign governments. Private clients include IBM, Pepsi, GM, Verizon, Hertz, Visteon, JP Morgan-Chase, and Lockheed Martin. In August 2014, he was named to the Association of Energy Engineers (AEE) Energy Managers Hall of Fame.