Behind the semantics of 'green,' 'low power,' and 'energy efficient'

While many electronics companies want to label their products as green, it's a hard claim using my working definition.

By Don Dingee

The terms “green,” “energy efficient,” and “low power” are flying everywhere right now, and amid all the marketing hype, sometimes the lines between them get blurred. Even our various titles here at OpenSystems Publishing have different views on this, because it all depends on where you stand in the supply chain and which direction you look. Here’s my quick take on the differences and why and how I cover the “energy-efficient” angle in Industrial Embedded Systems.

My working definitions

Green is a complete life-cycle term: a product takes little energy and resources during design and manufacturing, consumes little energy and leaves a small environmental footprint during its use, and retires gracefully with little to no adverse environmental impact at the end of its service period. Green takes more than just the electronics into account, focusing on issues like hazardous materials, disposal and recycling, emissions, and more.

Low power is just that: a product consumes little electronic power, perhaps even running off a portable power source such as a battery or fuel cell. This is more of the angle that several of our sister publications - notably, Embedded Computing Design, Military Embedded Systems, and PC/104 and Small Form Factors - take in their coverage. A user would like a product to consume as little power as possible to get as much battery life as possible, and designers need to manage the power availability, power consumption, and the heat generated internally to keep the product running.

Just because an electronic system is energy efficient doesn't mean it's entirely green. Case in point: North America's largest solar photovoltaic system at Nellis Air Force Base in Nevada. While expected to cut carbon dioxide emissions by 24,000 tons annually supplying 25 percent of the base's power, the array has transformed the landscape in a big way - only a wide open swath of desert could support solar on this scale.

Figure 1: Just because an electronic system is energy efficient doesn't mean it's entirely green. Case in point: North America's largest solar photovoltaic system at Nellis Air Force Base in Nevada. While expected to cut carbon dioxide emissions by 24,000 tons annually supplying 25 percent of the base's power, the array has transformed the landscape in a big way - only a wide open swath of desert could support solar on this scale.


Energy efficient implies both a design strategy and a managed use strategy to reduce the amount of electrical power that systems, not necessarily just a single product, consume. These systems can be relatively small, like a smart motor, or huge, such as the U.S. electricity grid. Energy efficient also encompasses better use of fossil fuels by implementing electronics technology to transform the exploration, capture, refining, and combustion processes. It also suggests the idea of electronics enhancing alternative energy generation.

Now for the hype

While many electronics companies want to label their products as green, it's a hard claim using my working definition. For instance, a product might be super in terms of energy consumption during use, but during production it consumes huge amounts of energy to make it. Or a product might use "Unobtainment" in some way to deliver a breakthrough in energy consumption, but later Unobtainment is discovered to pose a huge environmental threat when disposed or even just when used in the neighborhood. I look for a lot of proof where green is involved.

Low power is much simpler to prove, and the first test is to hang a watt meter on the product to tell me how much power it consumes. However, I get a lot of claims on low-power products that are really energy efficient but far from low power.

That's exactly why I draw the 15 W Thermal Design Point (TDP) line in PC/104 and Small Form Factors when I talk about low-power processors. A much higher dissipating multi core processor may indeed be a breakthrough and model of energy efficiency, but if it sears my finger when I touch it or requires hurricane force winds or liquid nitrogen to keep cool enough to run, it's failed my second low-power test. A product like this might be energy efficient compared to predecessors or contemporaries, but it's not low power.

Energy efficient up and down the chain

So that partly explains why my interest lies in energy efficiency, but there's a bit more to the picture when viewing it with the Industrial Embedded Systems lens. Looking at the electricity supply chain provides greater enlightenment.

Silicon level

Obviously, one way to get to an energy-efficient product is to use the lowest-power processor and peripherals a designer can find. But there are other breakthroughs here, like the advances in LED light sources or LCD displays, and better ways to control them that are also of interest.
Device level

This is where low power and energy efficient start to diverge in industrial contexts. For example, in a smart motor, the motor itself might not be low power, but the electronics package driving it efficiently might save a lot of power in use. Strategies like energy harvesting also come into play here - maybe there's a piezoelectric device, solar cell, or other technology at work.

Industrial network level

I spend a great deal of time looking at and talking about device networks - connections of devices tied together on a wired or wireless network. This is why I'm interested in technologies like ZigBee, LonWorks, 6LoPAN, IEEE 802.15.4, and a long list of other industrial protocols. Learning how devices work together to gather and share data and control some process can help save energy.

Grid level

Grids tie networks of industrial devices found in homes, buildings, and production facilities to networks of energy producers like electrical power plants and alternative energy sources and help manage the bigger picture. This is where things like smart metering, smart grid management software, and related items are involved.

Producer level

All the way at the other end, conventional and alternative technologies that produce and deliver electricity more efficiently are also of interest. Getting on the grid and delivering electricity reliably require more than just spinning a turbine, and the scale runs from small to very large.
In this issue

With all that in mind, that's why and how coverage like this E-letter issue on Design for Energy Efficiency (DfEE) comes together. We get a look at an innovative small motor technology, a view on FPGAs saving energy while controlling motors and displays, a touch on the green side examining how graphical system design helps subject matter experts get to bigger goals in energy production and use, and an example of how wireless sensor networks are saving money and lives.