Application Notes: Cutting Costs With Energy Auditing
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"Using energy efficiently is cool again," says Paul Twite, referring to the current high cost of energy. Twite is a power quality engineer, a Level II certified thermographer and a co-owner of 24-7 Power, an electrical consulting and engineering service company in the business of helping other companies discover and fix their energy inefficiencies. 24-7 Power is also a full service manufacturers' representative for many of the instruments Twite uses in energy audits.

Twite uses a three-step approach to help a company lower its energy bills. With the right tools and knowledge, your company can follow the same process using your own personnel. Here's how it works:

Step 1: Energy accounting

Reviewing utility bills reveals what your utility is charging for the electricity they say you used, but it will also reveal any utility demand charges and/or power factor penalties assessed. Any and all of these charges require follow-up monitoring to confirm that the utility's metering is accurate, that you are getting what you're paying for and that you are not paying excessive penalties. "Utility meters have been known to drift out of calibration or malfunction over time, so we feel it's good to double check the utility as a regular part of the energy auditing process," Twite reports.

Scanning electrical, mechanical and HVAC systems and building envelope using thermal imagers can reveal overloaded or imbalanced circuits, loose connections, overheating motors on HVAC equipment, malfunctioning steam traps, and a host of other conditions that might signal an inefficient use of energy.

Monitoring for power consumption, power quality and power factor can be used to follow up on issues or unusual anomalies identified by the use of a thermal imager. The appropriate meter can also identify harmonics and other internally caused power interruptions that may affect machine performance. Additionally, the right tool can measure peak demand and power factor, which are the focus of what follows.

Step 2: Analysis and identifying problems

Step 3: Proposing and prioritizing solutions

"In Step 3, I'm trying to figure out different strategies to lower the energy bills," Twite says. "To be effective in this step you (or your auditor) have to have an engineering background or at least have been in the energy business for a while. You need to understand how everything affects your energy costs."

Step 3, then, is proposing and prioritizing ways to lower your energy bills. There are at least three kinds of things that might be done to achieve that goal: 1) adjust processes, 2) repair faulty equipment and 3) replace inefficient systems and equipment. Once the action items for improvement are identified, then traditional return on investment (ROI) calculations can be used to help prioritize them. In what follows, some typical payback periods are included. Most come from Paul Twite's years of experience helping companies cut their energy bills.

Adjusting processes is often the most expedient way to eliminate demand charges and power factor penalties. Maybe process controls can be set to disallow those three large process pumps mentioned earlier from all kicking on at the same time. Or maybe there are electric water heaters that tend to run during peak demand periods, but you have enough water-heating capacity to allow you to push the water heating until after 10:00 p.m., when electric rates are lower. The calculations you did using energy bills and the confirmation of their correctness using a power quality analyzer will provide the data required for calculating the ROI for such strategies.

Repairing faulty equipment should follow from listing the problems that thermography uncovered in the electrical distribution system. Such problems might include loose or corroded connections, phase imbalance or worn insulation. Similarly, misaligned sheaves might be revealed by overheating. Laser alignment equipment can help fix that problem. In some cases, a motor bearing that is starved for lubrication can cause the motor to run hotter and use more energy. In that case, simple lubrication can significantly cut temperatures and full load current.

Replacing inefficient systems and equipment goes far beyond peak shaving. Often, following an audit, Twite recommends replacing an old HID or other inefficient lighting system with a new, high-efficiency compact or linear fluorescent system. He points out that the U.S. Department of Energy lists the two biggest energy consumers in most plants as the HVAC and lighting systems. "Upgrading to an energy-efficient lighting system can offer the easiest and quickest payback," he says. "In many cases, it's usually less than a year, especially if your utility company participates in the form of rebates."

Looking for rebates paid by utilities for the installation of energy efficient equipment and systems is something every company should do. Twite notes that to build a new coal-fired generating plant can take 12 to 14 years. One of the simplest ways that large, power-generating utilities can continue to run pofitably is to lower demand by encouraging companies to cut energy consumption by using equipment that is more efficient. Twite notes that not all rebate programs are the same and recommends that you check with your utility to see what is available.

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