Power regeneration system generates power, instead of heat

Case study: Briggs & Stratton’s first-of-its-kind power regeneration system cuts costs in reliability lab. Global small engine maker captures wasted energy, expects to save $50,000 per year, and modernizes data collection and control system.


Regen control cabinet at Briggs & Stratton: The power regeneration cabinet and workstation. Courtesy: Rockwell AutomationLawn mower and small engine parts manufacturer Briggs & Stratton was spending over $1 million in fuel costs alone to run engine endurance tests in its labs. To cut costs and realize the power wasted in heat from existing dynamometers, Briggs & Stratton worked with an automation vendor to develop a new power regeneration system. The new system helped Briggs & Stratton win two honors for sustainability, and the 556,000 kWh expected output could power 48 homes each year.

Daily, around the clock, the buzz of small engines fills the reliability laboratory inside Briggs & Stratton’s main plant near Milwaukee, Wis. Employees monitor the prototype and modified engines to meet the exacting standards set by one of the largest producers of lawn mowers, snowblowers, and other outdoor power equipment.

“Our task is to flush out failures in the lab, and prove the durability and safety of the design before it’s sold to a customer,” explained Ray Matuszak, test engineering manager, Briggs & Stratton. “Continuous, consistent, and accurate measurement of test time and operating characteristics are vital to establishing the engine’s long-term reliability.”

In February 2011, Matuszak and his team began gleaning this critical information from fully automated test stands that also provide a first-of-its-kind benefit—regenerating power for the plant. These innovative technologies helped Briggs & Stratton’s reliability lab become one of the most advanced in the industry, and quickly earned the company awards for environmental sustainability.

But overcoming the many challenges associated with the project took four years of effort and ingenuity.

Challenge-huge fuel costs

The reliability lab’s endless endurance tests are costly. Briggs & Stratton was spending nearly $1 million in fuel cost alone to run engine endurance tests in the labs.

Briggs & Stratton engineers realized they could lower operating costs if they could capture power that’s wasted in heat from the existing dynamometers. Their goal was to harness that energy and convert it into electricity for the plant’s consumption.

The problem was this type of power regeneration system didn’t exist. And the cost of creating it, engineers worried, might be too high to justify the investment.

Besides, the reliability lab needed other advanced technology to meet its core goals. First on the list: an automated supervisory control and data acquisition system with customized visualization and historical tracking capabilities.

At the time, clipboard-carrying technicians manually monitored each engine during its life span in the lab, recording load, various operating temperatures and other key metrics. This labor-intensive, information-gathering system was prone to inconsistencies and human error.

Energy-focused solution

As engineers from both companies began brainstorming the custom requirements for the project, they also focused on ways to achieve the best return on investment. One potential opportunity: a “Focus on Energy” grant from Wisconsin, which—like many states—had begun offering incentives to boost the use of clean, renewable power.

The engineers worked to compete for the state funding in 2008 and again in 2009. On their third try, they won a grant to pay half the cost of a pilot project.

The combined engineering team spent the next several months collaborating closely on keeping the captured electricity within the plant while maintaining a smooth and safe connection with the external power grid. Automation engineers worked with the local utility company, We Energies, to accommodate both power flows.

On the data-acquisition side, the biggest hurdle was establishing what information needed to be captured by the automated system, and what controls and safeguards would be included in the system. Then there were the discussions about control details, how engine operating characteristics should be displayed, along with understandable terms and data system custom features.

“For technicians accustomed to recording information on a clipboard, an interactive touchscreen presented a major mind shift,” said Richard Feustel, corporate energy services manager, Briggs & Stratton.

The automation vendor “walked a roomful of us through hours of whiteboarding, explaining options on how to enter, acquire, and share data. Everybody who would be affected by the conversion had an opportunity to contribute to the planning, so we got exactly what we wanted. That also made the later transition in the lab easier, because our folks had been part of the design process,” Feustel said.

In February 2011, the pilot program went online with 12 test stands designed for use with various engine types and horsepower limits. Each test stand is run by an alternating current (ac) motor using a variable frequency drive (VFD). The drives run at fixed speeds to start a gasoline engine. Once the gasoline engine is up to speed, the motor and drive load the engine to a torque level based on the engine horsepower rating. Alternatively, the system is capable of controlling complex duty cycles with varying loads and speeds as defined by the operator.

The regeneration system captures the power output of the gasoline engines and creates electricity with that power. All 12 ac motors and drives convert to a common direct current (dc) bus supply. The dc bus supply then converts the dc to ac, and synchronizes to the ac line, where all the power is directed back to the internal grid—reducing the need for electricity from the outside utility.

Six local enclosures provide two functions: local control of the drives for setup and up to six thermocouples per engine. Data used to monitor engine health and diagnose potential failures—including test run-time, multiple temperatures, alternator voltage, and engine speed and torque—goes to a programmable automation controller (PAC) via an Ethernet network.

With human-machine interface software, engineers and technicians can view critical, real-time information on engine load, speed, temperature, test-run time, oil-use rates, and other critical variables on any industrial computer in the lab. Historian software automatically captures that real-time data for analysis using Microsoft Excel, and technicians can identify any trending for use by reliability engineers.

Briggs & Stratton also invested in industrial energy management software, a comprehensive Web-based application that logs and analyzes energy-use data within one plant or from multiple, related sites. The energy management team at Briggs & Stratton uses the software to gather information about electrical, gas, and steam usage from power monitoring devices installed around the Milwaukee campus. Energy managers can access that information in the industrial energy management software and create reports about energy-use trends to share with the various departments in the plant. This information helps identify top-priority power issues.

It made perfect sense to invest the energy management software “so we could benchmark our power use and track our savings,” Feustel said. “Before, the only information we had about our energy use came in our electrical bills.”


Briggs & Stratton engines are tested and regenerate electricity for use within the plant via regeneration stations. Courtesy: Rockwell AutomationBriggs & Stratton quickly achieved a range of benefits, some expected and others that pleasantly surprised the company.

The reliability lab is on track to generate as much as 556,000 kWh annually—equal to the amount needed to power 48 homes every year. That captured electricity is fed back to the plant’s internal grid, which the company hopes will save an estimated $50,000 a year.

Another environmental plus: the electricity generated by the 12 test stands alone reduces the plant’s greenhouse gases by 442 tons annually.

The regeneration project was a major reason Briggs & Stratton received two prestigious honors for sustainability in 2011. The Environmental Innovation Award from the Wisconsin Manufacturers and Commerce, and the Galaxy Star of Energy Efficiency Award from the Alliance to Save Energy were presented in Washington, D.C., to Briggs & Stratton’s Chairman, President and CEO Todd Teske by Wisconsin U.S. Senator Herb Kohl.

In accepting the Environmental Innovation Award, Briggs & Stratton thanked its automation vendor for its role in creating the regeneration system.

Matuszak acknowledges the importance of the regeneration system itself, but contends the new automated data-acquisition and control capabilities are equally valuable.

“Certainly without the payback derived from power regeneration, this project would not have gone forward,” Matuszak said. “But automated data acquisition and control has a lot of positive effects on the bottom line. The most important benefit is improved test fidelity—we have streamlined data collection versus the crude traditional methods. We can tell instantly when an engine is not operating normally or when a test is set up incorrectly. The new system also increases productivity and efficiency by freeing technicians for other tasks.” Feustel and Matuszak agreed they’d like to eventually expand the project, but first they must harvest all the insights from the initial phase.

“The variety and volume of information is outstanding,” Feustel said. “We’re still learning how to best utilize the data we’re getting from the 12 test stands.” However, Briggs & Stratton is quickly expanding its use of industrial energy management software, and its ability to track, analyze, and visualize energy-use data from multiple locations. The company has installed a dozen power monitors in its Milwaukee facility that feed information into the software. Soon, Briggs & Stratton plans to put five monitors in its plant in Murray, Ky., and within five years expects to place them in the company’s 10 other manufacturing facilities worldwide.

“With the Web-based system, we can view other plants’ metrics and track our energy usage and spending across the enterprise,” Feustel explained. “Adding onto this global dashboard...is so easy, it simplifies the process of becoming even more sustainable.”

Return on investment details

Project cost: $216,800

Project savings: $48,031/year (533,678 kWh regenerated from expected engine testing at $0.088/kWh)

Simple payback: 4.5 yr (2.0 years with FoE Grant)

Focus on Energy Grant: $118,600

Completion date: 02/28/2011

Award: The building received the Wisconsin Green Building Alliance Sustainability and Energy Efficiency (SE2) Award Special Citation.

- Information from Rockwell Automation, edited by Mark T. Hoske, content manager CFE Media, Control Engineering, Plant Engineering, and Consulting-Specifying Engineer, mhoske@cfemedia.com

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