Energy conservation is an important topic these days.  For one thing, energy sources are become more and more expensive.  People also have environmental concerns – for example, how much is the use of fossil fuels contributing to global warming, and what effects will that have on the earth?

Sometimes public service messages oversimplify the situation with messages like “don't drive, take the bus”, and “don't turn your thermostat so high (or low).”  In the real world, there is always a trade off, and the simple solutions don't work in all situations.  The bus is not a convenient mode for buying groceries.  And here in the Southwest, turning the thermostat up too far can make your home practically unlivable – not to mention being bad for your computers. Luckily for us, life is not really a zero-sum game.  Information technology provides one of the most painless approaches we can take to solve these problems.

Technology, in the form of a computer-aided design system, can help us design new devices.  Sensors and mathematical analysis can help us find identify the causes of pollution as well as potential new energy sources.  But I'd like to focus on just one way that technological innovation can help – by making everyday devices smarter.  These days, with the low cost of integrated circuits, this often involves designing in, or “embedding” electronic controls.

Embedded systems technology can help in several ways: The right software can aid in energy conservation, by enabling the automatic shutoff of electrically-powered devices when they're idle. This can be done even without switching them off completely.  Embedded controls can optimize performance of a device according to demand; slowing the clock rate or lowering the voltage can save power.  These power-saving features are built right in to many IC's, such as Freescale's XEC. (www.freescale.com/files/32bit/doc/white_paper/XTMENRGYCNSVWP.pdf)

In homes, energy-saving devices include load controllers and setback thermostats.  Load controllers take advantage of demand-based electrical rates that many utilities use to encourage power savings at times of peak demand.  Of course, the homeowner could turn off appliances or set the thermostat back manually.  But automating them makes conserving energy not only more convenient but more effective, since these devices, unlike humans, are not prone to forgetting.

Digital sensors, which also utilize embedded processors, allow people to monitor their energy usage and take steps to correct wasteful activities.  (Example:  the Kill-A-Watt electric monitoring meter from Convenient Gadgets, www.cgets.com)

Another important way embedded systems can help is by enabling alternative energy and storage solutions.  Most green power sources are not as simple as they seem.  For example, photo-voltaic solar cells are relatively expensive per watt of power they produce, so to be cost-effective they must be utilized very efficiently.  The power output of a solar cell follows a smooth curve, with the highest and lowest current loads being relatively inefficient.  Only in the middle of the curve (the maximum power point) can the output be optimized.  If electronics are used to adjust voltage and current levels, we can get higher power outputs over a much wider area of the curve.  Although many solar panels are fixed in their orientation, some kinds of solar panels actively track the sun; software can help them do this.

Wind turbines are another technology that can be made more effective with embedded controls.  Turbine blades are typically designed for the average speed of prevailing winds.  When an area experiences high winds, turbines may spin too fast, damaging the system.  Software can be used to adjust the pitch of turbine blades to make them effective over a range of wind speeds, and to turn them out of the the wind the speed becomes too high.

Alternate energy isn't useful unless it can be stored and distributed. In many places, utility companies are required to “buy back” excess power generated by solar cells.  This means that there must be circuits that can switch the devices on and off the line, depending on whether they are producing excess power.   These devices also need to be sensitive to power outages.  If the utility grid's power goes down, the device must be taken off the power lines; otherwise it could create a hazardous situation for utility company maintenance personnel.

Modern appliances use AC  power, but solar panels produce DC.   To convert from one to another requires an inverter.  Inexpensive inverters, used for camping and vehicle-based power, are actually pretty simple devices that use silicon controlled rectifiers (basically, these are high-power solid-state switches) to produce an output similar to the alternating current from the power company.  But for serious alternate energy production, there are more expensive inverters with built-in intelligence.  High-end inverters produce a good quality sine wave (the smooth up-and-down curve you may recall from high school geometry), which is better for computers and sensitive equipment than the rough approximation produced by cheap inverters.  Quality inverters may have remote control panels, and can provide programmable control for charging of storage batteries, to help maximize your system's performance.  (From Solar Power 101: Inverters, by Jeffrey Yago, www.backwoodshome.com/articles2/yago89.html)

Energy conversion is also a problem in electric cars.  Electronics controls are needed to provide a way to control the speed of the electric motors.  One of the most efficient ways to do that is by varying the effective voltage to the motor.  This approach uses an SCR (solid state rectifier) to pulse the battery power to the motor on and off.  When these voltage pulses are smoothed out by an output filter, this provides an infinitely variable speed control.  This has the advantage of providing maximum torque over a wide range of speeds.  (See http://www.sdp-si.com/D220/PDF/D220T151.pdf

Yet another area where technological improvements are needed is in energy storage.  Until fuel cell technology is made cheaper, smaller, and safer, we must depend on batteries.  Batteries need to be better utilized, so they are more efficient and last longer. A smart charging system can help prevent overcharging, and achieve the best performance for each battery, regardless of its capacity or battery voltage. (http://www.benning.de/index.php?view=FileDownloadController&fid=94

Energy conservation is indeed a  timely issue.  As oil prices rise, and people become more environmentally conscious, it will only become more important.  Innovations in electronic controls and embedded designs are one of the technologies that will help make the renewable energy revolution a reality.

References:

The following are some relevant links in the fields of conservation and renewable energy:

Technology innovations alternative energy http://www.energy.gatech.edu/presentations.html

Funding for renewable energy, from Red Herring's Energy Focus (2005), http://www.redherring.com/NewslettersHome.aspx

Some information on power regulation for wind turbines: http://www.windpower.org/en/tour/wtrb/powerreg.htm

On tying inverters into the power grid: http://www.nooutage.com/inverter1.htm#Utility%20Protective%20Features