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How do you measure energy efficiency?

Posted: 21 Aug 2008     Print Version  Bookmark and Share

Keywords:energy systems  energy consumption  green engineering  measurement 

Everyone talks about energy efficiency, but how do you measure it?

That question is becoming critical, as engineers look for more ways to reduce power consumption in a vast array of embedded and energy systems ranging from power plants to consumer devices. The goal is to reduce energy consumption by establishing a baseline for gauging progress and return-on-investment. The payoff will be reduced energy costs and carbon emissions, the latter being the likely chief cause of global climate change.

"It's about understanding where you are," said Joel Shapiro, group manager for industrial measurement and control with National Instruments' Green Engineering Group. "Measurement is a fundamental piece of green engineering."

Shapiro and others in the electronics industry argue that it will be technology, not government, that solves the world's energy problems.

Smaller companies, too, have targeted the measurement market. One approach is tracking the efficiency of often-expensive alternative energy systems like solar photovoltaics.

Solar Energy Technologies, a small operator out of Circle Pines, Minn., pitched its "EnergyTraker" system at the Midwest Renewable Energy Association's energy fair in June. Company executive John Alexander said the system is designed to squeeze as much electricity as possible from solar photovoltaic systems by measuring parameters such as daily energy production, ac and dc current and voltage, dc amps and watts generated by multiple solar arrays, and even daily reduction in greenhouse gases.

The company is initially targeting businesses, but Anderson showed up at the energy fair in neighbouring Wisconsin to promote EnergyTraker for residential use.

Measuring embedded

The ubiquity of embedded processors is another key measurement market segment. In the auto industry, for instance, measurement tools are increasingly used to gauge the performance of embedded controllers in order to optimise fuel efficiency.

The collection of measurement data also enables the design of more energy-efficient products, said National Instruments' Shapiro. The company, based in Austin, Texas, is promoting these "fix-it" designs for applications beyond automotive that include reducing energy consumption in everything from speciality steel mills that recycle steel to tracking mercury emissions at coal-fired power plants.

"Measurements are included in the control algorithms or designs [for these systems] in real time," Shapiro said. These real-time measurements can then be used to update algorithms on-the-fly so that, for example, "sampling rates [in a power plant smoke stack] are constantly adjusted to remain in proportion to the stack flow," Shapiro said.

The monitoring of mercury emissions has become a priority for utilities seeking to avoid paying environmental penalties assessed under new government air-pollution standards.

On the supply side, National Instruments has also applied its measurement technologies to evaluating the status on the electrical grid of wind farms, a growing source of alternative energy that frequently must be transmitted long distances along the power grid. Measurement systems help integrate wind farms into the power grid and "ride through" faulty sections so that wind turbines can remain online even when parts of the electrical grid go down during peak demand or a network failure.

On the demand side, National Instruments has been working with companies such as steel recycler Nucor Corp. to track and reduce electricity consumption in arc furnaces in which scrap steel is melted for use in making concrete-reinforcing rebar. Based on its initial hit-or-miss approach, the recycler found that it was wasting energy by overheating scrap. Overheating can ultimately weaken steel. The company also miffed its Ohio neighbours by causing brownouts during peak demand periods, resulting in penalties.

NuCor eventually added a real-time measurement system to calculate the precise temperature for melting scrap steel. The company ultimately reduced energy consumption while improving its product. Moreover, reduced energy consumption was crucial for NuCor, since Ohio has one of the highest energy-usage rates in the United States.

The aim of these partnerships, said Shapiro, is to get "measurement tools into the hands of domain experts like embedded designers" who can apply them to achieve energy savings. That approach, which is increasingly used in the development of low-power chips like FPGAs, is being scaled up for a range of green engineering applications on both sides of the energy equation.

While the market for measurement tools is growing fast, experts said measuring the market itself is difficult. Most agree that it is fast becoming a major part of the U.S. economy. Companies such as National Instruments, which for the last decade have devoted vast resources to measurement tools, also lack firm figures on the market's size. They do say that many engineering jobs are fundamentally changing as the emphasis on energy efficiency grows.

The same lack of data holds true in related industries like photovoltaics. According to Travis Bradford, founder of the Prometheus Institute for Sustainable Development, solar power company announcements about increasing capacity are hard to decipher "because there are few metrics available to determine what [a capacity announcement] means" for the rest of the industry.

But tools are emerging. Shapiro estimated that 40 per cent of the customers for National Instruments' primary measurement tool, LabView, use the graphical programming language for energy-efficiency applications.

The green engineer has become a fixture at most high-tech companies. It will be their task to prove the assertion that technology holds many of the answers to energy and climate conundrums. What they need now are the tools to do the job.

- George Leopold
EE Times

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