Illumra Green Systems

2010-07-23T15:34:00.000-07:00

The energy harvesting bandwagon continues. It's good to see so many new applications for harvesting the energy in the world around us and saving just a few more batteries from the landfill. These replacements for AA and AAA batteries from Epson caught my attention. Mechanical energy harvesting at it's simplest. Just give your remote control a good shake before you press the buttons...

Energy balance in energy harvesting applications

2010-06-09T08:44:00.001-07:00

A friend of mine contributed to this article, which, while rather EnOcean-specific, still gives a very good overview of the whole general concept of energy-harvesting wireless sensors.

It might give you a little insight into the complexity of making a sensor that, instead of just using very small amounts of energy from a battery, must make do with the even smaller energy available from a small solar cell inside a building.

Been really busy...

2010-05-06T13:31:00.000-07:00

Haven't gotten around to posting lately, because I've been tied up putting together new projects, editing wedding videos for my brother, and much more. Didn't want to miss the chance to link to some press that's going out on one of the products I've been busy working on. It's fun to make things that save energy. It's even more fun to make stuff that runs on microamps of current, and therefore can operate practically forever with just a small solar cell.

I think some of the other case designs I (and others) came up with would have looked cooler, but I'm glad we went with the one we did, because it's simple, clean, and unobtrusive. It's still battery-free wireless, even though it provides a battery backup option. With a good quality lithium cell in it, the battery would probably last 20 years, though I obviously haven't tested it for that long.

200 lumen per Watt Efficacy barrier broken

2010-02-06T18:24:00.000-08:00

This is great news:

Cree has demonstrated 208 lumens per watt efficacy (luminous efficiency) in a laboratory LED. I can hardly wait to see these in full production. Still a long way to go for low-cost volume manufacturing, but it's nice to see such great progress in the last few years.

From 70 to 90% energy savings for walkway lighting

2010-02-03T08:12:00.000-08:00

I don't have all the details yet, but the information I received from a systems integrator in Canada indicates a big improvement in energy savings by using a wireless control network. The integrator installed new lights along a walkway at (or near) one of the Olympic venues there, and by using LED fixtures (not sure what type of light was replaced, probably some type of HID) they saved 70% or so on energy consumption. I suspect that, in terms of total light emitted, the new fixtures don't put out as much light overall, but they only put light exactly where it's needed. If I'm guessing correctly, this will also reduce wasted light spilling into the sky ("light pollution").

The kicker is when they added some new controls that I worked on. The lights were all powered by a single wiring circuit under ground. The whole circuit is controlled by a single light sensor or timer, so all the lights come on at one time and stay on all night long. The LED dimmer we provided behaves differently, however, and always turns on to 50% brightness (25% energy usage because the eye perceives brightness on "square root of energy" curve). The integrator put motion detectors on each light pole and connected them to our controller. With the additional energy saved when nobody is around, I'm told the energy savings (compared to the original lights) went up to over 90%. That's a lot of kWh each year.

Here's where it gets interesting: we set up all the controllers to self-associate into a pseudo-mesh network. Instead of each motion detector turning it's own light up to 100% when people walk by, the message is automatically repeated along the string of poles, turning all the lights up. After 5 minutes (with no motion at any pole) the lights all dim back down slowly.

It's a little departure from the way we usually build wireless control systems. Typically we want each dimmer to respond to just a few battery-free wireless control switches or maybe one or two solar-powered occupancy sensors. In this case, however, it needs to be more of a free-for-all, where any control point can stimulate a response from all other participants in the system.

Greenbuild Tradeshow - Phoenix

2009-11-11T05:41:00.000-08:00

If you're in Phoenix this week, come by the Greenbuild trade show at the convention center. I'll be in the EnOcean booth with the Illumra guys all day Wednesday helping to show the sustainable energy harvesting wireless technologies. While not every installation makes sense for wireless equipment, many do, saving time, wiring, minimizing out-of-service time for hotels, commercial and/or residential energy management systems.

It looks like it's going to be a very busy show this year, with a lot of great events. I'd love to stay an extra day and walk the show floor, as there are many amazing products being shown.

When less (energy) is more

2009-11-03T13:17:00.000-08:00

Here's one risk to upgrading your lighting to higher efficiency fluorescent (or CFL, or LED): People don't worry as much about turning off the lights any more. See this blog posting for a comment from an actual user of a Cree LED fixture - "I don’t worry about turning them off all the time." I think it's a lot like the "sugar-free" syndrome. If you get a "sugar-free" or "low-calorie" food, I think people tend to eat more of it.
I think automated control systems help keep unused loads off any time they are not needed, but I'm rather biased, since that's what I design.

We need a fundamental shift in lighting

2009-10-21T07:36:00.000-07:00

The title of this post may not mean what you think it means. At first, you may think I mean "we need to change all lights to LEDs," but in fact, it's really "we have to completely change how we build light fixtures before we can change all lights to LEDs."
The US Department of Energy has a contest going to award $10 million to the company that builds a 60-W lightbulb replacement using LEDs. There are several important stipulations that make this tricky, including dimmability using standard phase-cut wall dimmers, efficacy (luminous efficiency), color temperature and so on. Philips has produced the first entry, and certainly others are on the way.
The problem with this whole concept (while valid) is that everyone still seems to think that a lightbulb should look like the screw-in Edison base incandescent bulb. CFLs are the same way -- trying to fit a new technology into an old socket. Because of this, many CFL bulbs don't last very long because they get too hot in standard fixtures.
What we need to do is redesign the fixtures from the ground up. LEDs produce light and heat, and the heat they produce must be removed or the LED will fail quickly. The 20,000 hour (or longer) life of an LED presupposes that the LED is kept reasonably cool. Here's where the fundamental shift needs to happen.
Light bulbs, as a concept, need to be completely changed. Most luminaries (fixtures) are designed to take light from a point source (a light bulb) and spread that light evenly over a certain area. One notable exception is the linear fluorescent fixture. It takes light from a linear (long line) source and spreads it out. Take the same concept and apply it to LEDs, and we will be getting somewhere. Spread the LEDs out across the entire surface of the fixture, and the heat will be spread out and the light can still be focused nicely into the living/work space.
The "bulbs" can be individually replaced and certainly don't have to be replaced all at once. When one or two LEDs fail, the fixture can keep working (wire the LEDs in parallel, not series).
To make it even more fun, mount each LED on a metal-based circuit board (they are used a lot in high-power electronics) and include a small permanent magnet at each LED mounting location in the fixture, and now the LED elements are held in place magnetically. The electrical contacts can just be spring metal, and no real connector is required.
Part of the reason I'm posting this idea, rather than patenting it and keeping it to myself, is that now it can't be patented, because this is "prior art." I'd like many manufacturers to take the idea, build compatible fixtures and LED elements, and sell them to everyone.
If we want to accelerate the LED lighting revolution, I believe that a completely new paradigm is required.

Open Source Software Conference October 2009

2009-09-15T22:14:00.001-07:00

I'm presenting two classes at the Utah Open Source Conference this year. I've had some ties to that group (and other open-source projects) for quite some time now. The cost is quite low, and as far as training goes, there are some great presentations on everything from virtual machines to advanced image editing with GIMP.

If you can make it, I highly recommend it. I'll be talking about securing your data over the internet with OpenVPN and filtering your home or office web traffic with Dansguardian and transparent proxying. There are some big names in the open source community presenting as well, including one guy who literally wrote the book on open-source telephony.

Nice to see more solid data on LED efficacy

2009-09-08T23:49:00.001-07:00

Interesting blog post on one of the industry publication websites. They have some nice data on efficacy (power to light conversion efficiency) of several white LEDs used in light fixtures. Remember the efficiency numbers stated don't include power loss in the power conversion circuitry (in fluorescents, this circuitry is called the ballast) nor the losses due to the optical system (lenses, reflectors, etc). It's interesting anyway.

Zigbee, EnOcean, and Energy Harvesting

2009-08-31T07:11:00.000-07:00

I won't take a lot of space for this one, as interest in this topic is probably narrower than what I usually discuss. This article about Zigbee vs. EnOcean in energy harvesting sensors for building management and energy savings presents some interesting points. Interestingly enough, illumra makes systems with both technologies, and even uses them together in a hybrid (or bridged) configuration. We use Zigbee for the backhaul, and EnOcean for the energy harvesting controls. As always, a disclaimer - I do work for/with illumra, so I'm not a completely objective third party relating to those products.

Expensive LEDs - why?

2009-08-12T10:05:00.000-07:00

One contributing factor to the high cost of LEDs - they have to be kept relatively cool to preserve their long lifetimes. This means the "bulbs" require expensive metal heat sinks and ways to get the heat from the LED into the heat sink. There are lots of great innovations in this area, but it still adds a lot of cost.
A separate but related issue is that the efficacy (luminous efficiency) of the LED drops off when you turn the brightness up. There's a great article in the latest edition of the IEEE Spectrum magazine that starts from a nice high-level overview, then digs down to some very technical information.
What it boils down to is, we can have very bright LED lights, but they'll be less efficient than they could be, or very efficient LED lights, but they will be less bright (or more costly, assuming we just put more LEDs in each bulb/fixture).
Engineering is always about making the right tradeoffs - there's a lot of research going into LEDs right now, and over time we'll see the benefits.

What did you do today?

2009-07-15T20:27:00.000-07:00

I recently helped pour some concrete as part of a project with some extended family members, quite a change from the usual comfortable office environment where I do embedded control system development work. It's fun to do something different once in a while, it gives you a different perspective on things.

As I considered the permanence of the concrete we poured, worked, and finished that day, I realized that there is also a lot of permanence in my day-to-day work. While the constant flow of new products, new features, and new customers makes for interesting work, with new challenges, I realized that the firmware and hardware I (and my colleagues) develop (and the company sells) will be running continuously for many years. Will it run as long as the concrete lasts? Probably not in a device sold today -- after all, the microcontrollers that run the code only have a memory life of 100 years or so, and probably won't be around that long, on average. However, the same code I write today will probably be programmed, in one form or another, into devices over the next 20 or more years. Over the lifespan of the controller, it could save many millions of kWh of energy (and of course, lots of money and energy-related emissions). That's something to be proud of, I think.

So what did I do today? A lot more that you might think, just looking at the code.

Efficacy (luminous efficiency) is getting there...

2009-05-07T14:21:00.000-07:00

At last, a production LED that approaches the efficacy of good fluorescents (100 lumens per watt).

I saw this announced at the Lightfair tradeshow this week. I expect to post more on other subjects later. Now admittedly, this doesn't include power loss in the power supply (ballast), but we're getting there. I'll be interested in how the light radiates and how much they cost as well, because that will make or break it in the long term.

Biggest Barrier to LED lighting

2009-05-02T10:19:00.000-07:00

Okay, there are several barriers, and it could be easily argued that there are more serious ones than this. I believe the biggest problem with LED lights will be shortened life to to overheating in standard fixtures (I believe short CFL life is most often caused by overheating, and I'm not convinced that Energy Star or other standards address this). Most fixtures that have been designed for edison-base incandescent bulbs are not designed to remove the heat from the fixture or bulb. Instead, the fixture is designed to withstand the heat (ever see a label on a light fixture that requires 105 C rated wiring?). Some of the worst offenders, as far as keeping the heat in, are recessed lights that are rated for insulation contact. This means that the fiberglass (or blown-in) insulation can completely cover the light fixture inside the ceiling. We did some testing with Illumra wireless relays in the ceiling box and found that even with a 40 or 60 watt incandescent bulb, the wiring box could reach 80 or 90 degrees C.

Okay, enough background, why is this such a big deal for LED lights? Put simply, like any electronic device, LEDs do not like to be hot. It shortens their life a lot. For the physics behind this (if you care) the Arrhenius equation gives you some idea - doubling the temperature doesn't just cut it's life in half, it cuts it much shorter. You see, most light fixtures have been designed to take light from a (fairly focused) point source, the filament in the bulb, and diffuse it evenly over a space. Putting lots of LEDs at one point concentrates the heat, making it harder to keep the LEDs cool. Spreading out the LEDs is a good solution, but then the fixture isn't designed to take light from many points and distribute it.

I've seen a number of LED lights in a fluorescent tube form factor, but with most (or all?), the LEDs radiate only out one side of the bulb, defeating the reflectors in the fixture, preventing the light from shining where it should. In an office environment, you would probably get very uneven lighting with this solution (until they start mounting the LEDs 360 degrees around the tube).

The real solution is to design the fixture from the start with LEDs in mind. This will require a "ballast" (really a power supply) that provides a constant current to run the LED string, along with either failed LED bypass or failed LED indication (if each LED is removable). I suggest that, if a standard small form plug-in LED module included a small parallel LED with a large value resistor, then when that LED fails (open) the small cheap LED would illuminate to show which module(s) need to be replaced. Otherwise we'll be in the same situation as with a string of holiday string lights, when one bulb is slightly loose, the whole string fails to light. The whole string should be driven with a constant current (for most even illumination). Typical drive currents are 350 mA, and if the correct number are arranged in series, the voltage of the string could be set not far below the voltage provided by a rectified AC line voltage, which will help with efficiency (using a switching constant-current power supply with AC line power factor correction is even better - see my earlier posts about that).

More to the point of overheating, spreading the LEDs around a large surface helps solve the problem. Imagine a standard office ceiling fixture with 4 T8 fluorescent tubes. Remove the tubes, then cover the surface of the internal reflector with LEDs. The heat is spread out, the whole string can be in series, and when one cartridge fails, the small red LED shows you which one to replace. This solves most (if not all) of the issues with LED lights. Old fixtures could even be retrofitted with this solution without requiring complete replacement of the fixture. With a more expensive "ballast," dimming could be supported for daylighting or load shedding. As I've mentioned before, however, phase-cut dimming is not a good idea. Either powerline-based data communication or wireless control (insert shameless plug for Illumra products here-remember I work for them :-) is the only good option for dimming the lights. The extra cost (in the bulb/ballast/fixture) to support phase cut dimming (just so you can use your old "standard" wall box dimmer) is not worth it.

Two unrelated notes:

One, I've been adding new features recently to the firmware in many of the Illumra dimmers and load controllers. From day one, we've always tried to select default operating modes that are the most convenient for the users of the products. At the same time, while they save energy as much as possible, we don't want their operation to be intrusive. For example, if a receiver is set up to turn off the lights when the space has been unoccupied for a while, for a time, after the lights turn off, if occupancy is detected, they turn back on. However, California Title 24 (which includes regulations updated in 2005 for how these devices must operate) doesn't allow automatic turn-on when you enter a room. We're making Title 24 compliance the standard operating mode for our receivers, even though it's potentially more intrusive (meaning you must turn on the lights manually when you first enter the room). It's been a tough decision, but since an automatic-on mode is available, we'll still support modes that require less intervention. Perhaps if you are ever irritated by a light that could turn on automatically, but doesn't, you can remember that you may be saving a little more energy (and money) that way.

Two, while I won't be there personally, if you're in New York next week, drop by our booth at the Lightfair tradeshow. Illumra products will be shown in one part of the EnOcean Alliance booth, as well as integrated into a number of products under various brand names throughout the show.

Luminous Efficiency of LEDs vs. CFL

2009-04-17T07:11:00.000-07:00

There is a lot of misinformation about the efficiency of LED lighting. Much of the information out there is not about what LEDs can do today, but rather what they are working toward. In the end, what we all care about, when trying to save energy, is Luminous Efficacy, which is the efficiency of the conversion of electricity into usable light. It's specified in Lumens per Watt.

A good quality fluorescent bulb with an electronic ballast provides on the order of 100 lumens per watt. If it's a dimmable fluorescent, that number can go down quite a bit when dimmed to low levels (down, you ask? Yes, there is a fixed amount of power to run the ballast that doesn't change with dim level, which isn't converted into light). A compact fluorescent is usually in the 50 to 80 lumens per watt, I understand. Only the most exotic prototypes in a lab environment an beat this with LED sources. Most of them are well below what a compact fluorescent can do.

Of course we all want a better light source, so enormous amounts of money (both private and public) is being poured into LED research. I'm sure, in time, the efficacy will improve. I found this nice article about the fundamental sources of heat produced in LEDs, which gives a good outline of where the waste energy is going, but it stops short of giving efficacy numbers. The biggest challenge today, I think, is thermal management. If the LEDs are run at too high a temperature, they will not live up to their promise of long life. CFLs suffer the same problem, and in the wrong kind of fixture they only last a few months instead of the many years they are capable of.

The best way to save energy, now and always, is to turn off lighting that is not needed. While I still train my children to turn off the lights when they are not in the room, they still forget often enough, and the motion detectors I've set up take care of the rest.

CFL power quality

2009-04-08T14:38:00.000-07:00

Long-term (assuming that CFL bulbs become a substantial percentage of the load on our power grid) the cheap power supplies that are built in most compact fluorescent bulbs will create power quality problems. See this article for some details.

While I agree that it's a problem, having designed power supplies like them, I would assert that it's already been a problem historically, and perhaps is presently, too. The harmonic content generated when a rectifier sits directly on the AC power line, connected to capacitors on the DC side, is pretty nasty. Perhaps counter-intuitively for those of you with an electronics background, the noise becomes worse if you use more capacitance after the rectifier. Think of it this way: a larger capacitor doesn't droop as much between power cycles, so the recharge occurs over a smaller piece of the power line cycle, making a shorter (but higher-amplitude) spike of current. During the remaining power cycle, little or no current is drawn.

While this doesn't represent the traditional inductive or capacitive load (a simple phase lead or lag of current) it's a power quality problem. Capacitor banks on the utility distribution lines will not solve the problem. In the end, the power supplies at the end of the service line must be improved.

As an example of this problem, see this image below of the AC waveform at my house. Compared to a pure sine wave, the peak is significantly clipped. I believe it's due to non-power-factor-corrected power supplies that are in use throughout my neighborhood (and I think the same is true of most parts of the power grid).

Sustainability and why dimming your lights may not save...

2009-03-18T11:45:00.000-07:00

I ran across a series of interesting articles on "sustainability" today. I'm trying to figure out if people are finally joining the sustainability movement because it's becoming more mainstream, or if they really think it's a good idea. Perhaps the higher cost of energy (recently) has been pushing people to save money. Maybe the economic downturn is hitting people so they're trying to save money everywhere they can.

In any case, the ILLUMRA philosophy still applies: saving energy (for any reason) by automating and controlling devices that use energy. Decades ago it only mattered that the lights worked, the cost of operating them was small in comparison with the light bulb itself (or so everyone assumed). Of course most of the products sold by ILLUMRA (the company, as opposed to this, the blog) involve energy harvesting in one way or another, which ultimately saves wiring, batteries, or both.

In any case, here are links to the articles:
Survey: Americans favor Sustainable Engineering and Manufacturing
Energy cost savings through load shedding (and load balancing)

The power factor issue in the second item will be, I believe, a bigger issue in the future. I've been recently working over ideas for large-scale (building-wide) LED lighting systems. It's critical that the power supplies (ballasts) for the LED lights include power factor correction, and therefore act as "nice" loads on the grid. This will avoid the kinds of noise-induced power quality issues that often occur in large manufacturing environments. Years ago, power supplies in all PCs were not power factor corrected, and contributed to power quality problems (including neutral heating) in office buildings. If someone goes a "too-cheap" route when converting their lighting, they could create as many problems as they solve.

One reason this is so important: Dimmable fluorescents are a nice way to introduce some energy savings (and load-shed capacity) to a building. However, if you use ballasts that support phase-cut dimming on their line inputs (as opposed to 0-10V low voltage control dimming) then the effective power factor will degrade. If a whole office building used this technique to load-shed during a high-demand time-of-day, the net effect may actually increase the electric bill of the facility (because of the power factor and demand charges outlined in the second article above). It's important that while phase-cut dimming is a nice feature on a dimmable ballast (fluorescent or LED) it's not a good way to control a large number of ballasts. A 0-10V solution (wired or wireless) is the best way to go.

Energy Harvesting - not ready for prime time?

2009-02-27T06:12:00.000-08:00

Nice brief summary article relating to energy harvesting technologies:

http://www.greensupplyline.com/214301888

I've got mixed feelings about his assertion that energy harvesting isn't ready for "prime time" yet, though. While I will agree that it's not close to being a technology that fits every application yet, there are certainly some nice niches that fit well.

For example, there are a lot of buildings that can be retrofitted with energy saving lighting controls (California's Title 24 regulation in particular) but the installation cost is high in order to route wiring for occupancy sensors in the room (or even worse, installing a sensor on every fixture). In this case, a wireless, battery-free, energy harvesting motion detector (other manufacturers with the same concept: 1, 2) is a perfect fit. While the equipment cost is higher than that of a wired system, the installation cost is much lower, possibly less expensive overall, but certainly competitive. The sensor harvests solar energy, stores it (enough to run for two days or so in darkness) and operates the occupancy sensor and the radio transmitter.

In contrast, and ultrasonic sensor uses thousands of times more energy, so to make an energy harvesting vacancy sensor (or occupancy sensor) would require a very large solar panel, enough to make it impractical. So much energy is required, in fact, that it would make a lot of sense to turn the sensor off when the lights are off (unless automatic on is required -- CA Title 24 doesn't allow for that) or at least reduce it's operating duty cycle.

On a related note, there is a movement to revive magnetic coupling to charge cell phones, laptops, and the like. Inductive power coupling is nothing new, it's been around for years. I have a waterproof cordless phone that charges without any electrical contacts, I understand that many electric toothbrushes recharge the same way. In much the same way that Apple made touchscreens new and exciting with the iPod Touch and the iPhone, companies are going to revive magnetic coupling so you can put your laptop on a special pad on (or embedded in) a table or desk and charge without a cord.

While it's convenient, the relatively low efficiency of this power transfer method runs counter to some of the goals of the green movement. On the upside, however, the stray fields from these devices may provide a new mechanism for energy harvesters. Adding a small magnetic pickup coil to an energy harvesting device may, in the future, provide sufficient energy to run these sensors without the need for a solar cell, mechanical, or thermal harvester.

LED vs. CFL vs. Incandescent

2009-02-09T15:36:00.000-08:00

This article I read on edn.com, while it contains nothing I haven't read elsewhere, is a nice summary of the whole migration toward LED lighting. I hope to see LED lights that approach the efficacy (efficiency in terms of lumens per watt) of a good fluorescent light (around 100 lumens per watt). One named in the article was getting closer (about 80) and I've heard of laboratory tests of prototypes that are in the neighborhood of 150 (yes!).

I still want to see an intelligent way to retrofit existing dimming bulbs with dimmable CFL and LED fixtures. I think a bidirectional communication protocol between the bulb and the dimmer might be a way to do it, perhaps over the existing power line. The problem with that method is the extra cost, complexity, and reliability of adding that hardware to the bulbs and the dimmers. A dimmer would probably need to detect the connected load, and either use traditional dimming (for regular bulbs) or leave the power fully on and communicate the dim level, letting the ballast at the load control the brightness.

Perhaps the communication can occur by doing phase cutting, much like regular dimming, but use a 95% brightness level for one digital level (zero or one) and 100% brightness for the other value, and use, in effect, a serial data stream over the power line.

Long term, however, low or medium voltage DC power to the lighting loads, with digital control at the point of load, would be more efficient and have fewer points of failure than the current methods.

Just a few random thoughts. I hope to come up with a more coherent post in the near future. It's been a very busy few weeks, so I haven't been able to write a more organized, thoughful post than this.

Electric Cars for Commuting

2009-01-15T21:59:00.000-08:00

While I doubt I'll be able to afford one until long after they become available, I'm anxiously awaiting the release of some (almost) pure electric cars. The Chevy (GM) Volt is of particular interest, as it seems to be one of the front runners at this point. It seems that the battery technology is the real weak point at the moment.

From their site:
"All the technology for the car is here today, except for the battery pack. It will use lithium-ion (li-ion) technology. Current hybrids use nickel-metal hydride (NiMh), which carry much less energy per unit weight. The li-ion cell technology exists but putting it into tested and safe packs is what will take some time. There are companies working with GM and trying to get these Li-ion batteries and their packs ready for automotive use."

It's fascinating the different energy storage technologies that have been tried. I recall a city bus that used a large flywheel to recover energy (using regenerative braking) and store it to start the bus back up after each stop. Certainly NiMh batteries see a lot of use in hybrids today, but aren't ideal. Supercapacitors have pretty decent energy storage capacity, but unfortunately petroleum based fuels carry about 100 times the energy (per kg of mass - about 12 kWh vs. 0.12 kWh for Lithium Ion batteries).

Fundamentally, hydrogen is a nice way to store energy, but because it doesn't exist in nature (most of the hydrogen on earth exists in the form of water, H2O) we can only create hydrogen "fuel" by using another energy source to break down water (or some other source of hydrogen, like natural gas). I have only looked briefly at this site, but it seems to have a decent rundown of the requirements to create some amazing solar projects in the southwestern USA.

I'm sure there's some great research going on to find more efficient (and cost-effective) ways to convert solar and other energy forms into hydrogen, because solar (on it's own) isn't a solution to our energy problems. The reason for this is simple: the sun sets at night and peak demand occurs late in the afternoon and into the early evening. For the same reason that electric cars have limited range, we can't store enough energy (with current technology) to keep everything running overnight. If a highly efficient solar-to-hydrogen conversion system can be developed, then storage becomes much easier.

Daylight Saving - Does it really save energy?

2008-12-11T23:19:00.000-08:00

For a more thorough analysis of this subject, there are some studies currently underway and other useful info around the web, but I'm not sure if they make this point well enough. Try this link or Google "daylight saving energy" for more info.

Based on some of the information about peak electrical demand in California (see my other posts about some data that came out of UC-Davis) I'm not convinced that daylight saving actually saves energy as much as it used to. When previous studies were done, central air conditioning was not nearly as common as it is today (many of the studies date back to the 1970s). I believe that central air is a large contributor to the peak demand when people return home from work in the afternoon, even more so when they use a programmable thermostat to set the temperature higher while they are at work. Without a programmable thermostat, the overall energy usage is much higher, because the A/C unit runs more during the day. However, a programmable thermostat changes the setpoint around the time you get home, effectively turning on the A/C for an extended period right at that time, increasing demand a lot, even though the overall usage throughout the day is lower.

Daylight saving effectively gets everyone home from work one hour earlier (as far as where the sun is in the sky) and therefore closer to the hottest part of the day. At this point, more energy is needed to cool the home to a comfortable temperature, while if people returned home an hour later (without daylight saving) the house wouldn't be as hot because the sun is lower in the sky. Of course the evening lighting load will be greater, because the sun goes down, but certainly that's a smaller load (overall) than the A/C unit.

This is an idea that may sound completely backward, but consider it for a moment. Assume for a moment that it is true that programmable thermostats cause most A/C units in California to turn on at about the same time each summer afternoon (within an hour or two of each other) and then they run for an extended period of time to cool the buildings. Now what if, instead of using demand response controls to disable some of those A/C units to reduce peak demand, you instead use a demand response control to turn some of those A/C units on earlier, cooling some of the homes earlier than others, so they won't need it later when all the other units kick on. It's the exact opposite of a typical demand response system, but in terms of reducing peak demand, it may be exactly the right thing to do.

I really think that new studies will show that daylight saving is no longer helping our energy usage (especially on the basis of peak demand) as much as it used to (if at all).

Hotel room Energy Savings

2008-12-02T21:29:00.000-08:00

There seems to be a lot of interest in saving energy in hotel rooms and timeshare resorts lately. After hearing what some of these places spend on electricity (hundreds of thousands of dollars per year) it's no wonder. I think there's a lot of energy to be saved there, given how often people leave the A/C running full blast even when they leave the room for the whole day.

Whether it's a standard window air conditioner like you'd pick up at Home Depot, or a PTAC (packaged terminal air conditioner, I think) unit, they use a lot of power. When running, they're probably 2 kW at a minimum, and if you're out of the hotel room most of the day, that's a lot of kWh. I understand that in Europe, a lot of hotels have occupancy (presence or absence) sensors in the rooms or "key card switches" at the entry of the rooms to enable the power in the room. It seems that there aren't any cost-effective technologies to detect the presence of a non-moving person in a room, so when people go to sleep at night an occupancy detector isn't an ideal solution.

The key card switch seems to be pretty popular, however. When you enter your hotel room, using a magnetic stripe key, there is a slot near the entry door to "store" the card. When you insert the card into the slot, a switch is activated to enable the power and A/C in the room. In a new hotel, it's pretty easy to wire for this, though the extra wiring may be expensive. In a retrofit, however, a wireless device like the illumra key card switch is really slick - just sitck it on the wall, and it sends radio messages to the receiver installed in the PTAC (at a minimum) and on the lights and television, too.

I've intentionally stayed away from discussing specific illumra products in this blog, rather focusing on energy savings, green solutions, and other general topics. I'll generally keep to this policy, only occasionally linking to illumra.com, because the energy problems we face are much bigger than any product or company can hope to fix on their own. (See the "full disclosure" in my first post - I work for a company making energy saving products, so I'm at least a little biased.) Everyone has something to contribute to the solution, and I expect to cover a lot of them. Even within the battery free wireless space there are a lot of players, and if you want to see some of them, take a look at the EnOcean Alliance for more information. There are a lot of very cool products out there, but a little due diligence is important before installing any new technology. Analysis, even a quick back-of-the-envelope calculation or even a very rough "guestimate" should be used to justify any energy saving measure.

As an example of this, one of the features some people have requested for hotel key card switch control is the use of a window sensor to disable the A/C when the window is open. This is nothing new, it's used in a few places in Europe I know of. However, the incremental cost of adding the window sensor may (or may not) result in a significant return on investment compared to just using the hotel key switch alone. After all, if only one or two windows are opened regularly in a 1000-room hotel, even if the A/C is running, the cost savings of having the A/C turn off automatically (when the window opens) may be pretty small. On the other hand, if you're in a tropical area near the beach and people open windows regularly, the cost of the extra sensor may be paid off very quickly.

In the end, a lot of little changes will add up to a big change over time. I've been more careful to shut down my computers or put them to sleep when not in use, and noticed a few dollars difference in my last electric bill. Not much, I admit, but maybe I can find a few more places in the house to use compact fluorescents. Once the dimmable ones aren't prohibitively expensive, I may be able to try them in a few more fixtures, too. I'm glad I live in a dry climate, as my evaporative air conditioner ("swamp cooler") is a lot less expensive to operate than central air would be.

Demand Response Systems to help the power grid

2008-11-27T22:47:00.000-08:00

I recently read that California is stepping up (or planning to increase) their billing rates for electrical usage during peak hours. There's a fascinating graph (from a study done by UC Davis) showing the amount of power consumed by residential and commercial customers during a typical day. The sum of the two graphs actually looks pretty sinusoidal, with peak demand occurring between 4pm and 7pm. The peak of the commercial/industrial graph is a little sooner, the residential one is a bit later.

In many parts of the country, consumers receive a credit on their utility bill if they install a remote-controlled shutoff device to their air conditioner. Given that the A/C unit on most homes is the largest electrical load in use (particularly during the daytime) it is a good candidate for saving electricity and reducing peak demand on the electrical grid.

There's a downside to this method of demand reduction (not just the fact that your house will get a bit warmer for a while) as it defers, rather than eliminates, the electrical demand. Once the utility allows the A/C unit to turn back on, it will then operate for a longer time to bring the temperature of the house back down. In the end, you only shift the demand, you don't eliminate it.

A better (but more complex) solution
A better method would be to raise the temperature setpoint a few degrees for several hours, assuming that the outdoor temperature will begin dropping, reducing the cooling load later. If discomfort of someone in the residence is an issue, it seems that reversing the logic might actually serve the purpose better: a few hours in advance of peak demand, commanding a longer cooling cycle (to pre-cool the house a few degrees) would reduce the demand that will occur later in the day. Unfortunately, this doesn't prevent the electrical usage, it again shifts it. However, shifting it earlier, rather than later, may be a better solution.

Another study by UC Davis (and supported by others) indicates that decreasing the level of lighting by 15% is imperceptible to people in a building. While that is probably true, I don't think the answer is as simple as dimming the lights. I haven't made measurements to be sure, but I suspect that decreasing the level of a dimmable fluorescent light by 15% results in a power savings less than 15% (probably 5 to 10) so the lighting efficacy is reduced. (Efficacy is the efficiency of a light source in terms of light produced per watt of power consumed - usually specified in lumens/Watt.) Even if a reduced light level is perceived, dimming the lights in a building is certainly preferable to a rolling blackout.

Dimming incandescent bulbs to save energy has another side effect (in most cases). Incandescent dimming is usually accomplished by chopping off part of the electrical power waveform. In other words, the power is turned off for a fraction of every power line cycle. This phase-cut method of dimming places a nasty load (along with lots of electrical harmonics) on the power grid. Dimming a large percentage of a building load in this manner would probably cause power quality problems.

Load Shedding on-demand
Demand response - an action taken by a customer of an electric utility in response to a request by the utility during a period of high demand - is likely to become more important to protect the integrity of the power grid in certain areas. A demand response that eliminates, rather than defers, power consumption is more useful than simply shutting off A/C units for a while. Some critical technologies to make this possible: building-wide lighting and HVAC control systems, dimmable fluorescent ballasts, per-fixture control when dimmable ballasts are not an option (allowing a subset of light fixtures to be turned off), and communication methods to get the demand message from the utility to the fixtures.

I've been experimenting with a dimmable (0-10 V controlled) fluorescent ballast, and I hope to have some efficiency vs. dim level information in the future. I've noticed a small shift in color temperature as the bulbs are dimmed, but nothing even close to the color shift that occurs when dimming incandescents.

Measure the payback time: Green Speedometer

2008-11-04T14:27:00.000-08:00

With the constant fluctuations of the price of energy in various forms, combined with fluctuations in the cost of renewable alternative sources of energy (for example, the price for 1 kW worth of solar panels) it's hard to keep track of how fast an installed system will pay for itself.

What I'd like to see is a web page that dynamically monitors these factors, and perhaps by entering your postal code it calculates your location (for an estimate of the number of sun days per year, the local electrical rate, and all other applicable factors) and creates a graph or even just a "speedometer" to show how long until the system is paid for.

Perhaps along with this, and estimate of the number of tons of CO2 that will be saved as well, though I'd prefer that the calculation include the impact of producing the solar cells (or whatever) in the calculation.

When "green" isn't

2008-10-17T11:56:00.000-07:00

I recently attended (and presented at) an open source conference. One of the presentations was fascinating, covering all kinds of automation devices for home lighting, security, and automation. The presentation is here:

http://2008.utosc.com/presentation/51/

He uses Control4 wall-mounted dimmers to control the lights throughout his house, and motion detectors dim the lights on (gently) when you walk into a room or down a hall. The part I found fascinating, however, is that if you try to use his system to save energy, there isn't too much to be saved, because each wall box dimmer consumes a few watts of power, even when off. With a house full of these, that could be over 100 watts of standby power, added to whatever the central controller requires (maybe a few hundred watts if it's a PC). This means that you're burning between 3 and 10 kWh every day just to run the automation systems. He specifically pointed this out during the presentation so we would not try to save energy by burning just as much energy.

Referring back to the system in my kitchen that I described in my first post, since I'm using older generation Watt Stoppers, only one of them is drawing power, and it provides the DC supply to the illumra room controller and the other relays. If all the Watt Stoppers were powered by 120VAC, there would be a lot more standby power being used. I think it's only 2 or 3 watts, so it would probably be a wash to swap it out for 120VAC powered illumra single-channel room controllers, as they draw about 1 watt each. If I had single switches rather than three in one spot, then the power savings of the single-channel illumra receivers would be more compelling, compared to watt stoppers and the 3-channel room controller. Maybe I'll try out a one-channel unit somewhere else in the house.

Introduction

2008-10-16T13:50:00.000-07:00

Green Solutions - Why should you care?

Full disclosure first: I work for a company making energy saving devices, so of course I'm interested in you saving energy, money, and everything else that goes along with it.

I'm writing this blog to share some of my thoughts on green technologies that I have purchased, designed, or thought about building. I'm sure I'll figure out some other interesting things to include later as well.
To answer the title question of this post, there are many angles to "green" technologies. A few of them, in intentionally random order, are:

You want to do your part to "save the planet."
You want to save money on your energy bills.
You want everyone else to know you're trying to save the planet.
You think it's cool to try out new things.
Energy independence sounds nice in case there's a disaster (solar panels on your roof?).
You don't think our way of life is sustainable (we'll run out of "stuff").

In future posts, I plan to discuss a lot of these points, but for now, I'm going to start with a few projects I have set up around my house.

First off, my three children are ages 9, 7, and 4, so while they're pretty well trained at turning off the lights, they forget to do so at least once a day. I decided to set up one of the devices I worked on at the office to try to save a little energy. It's a "room controller" from illumra. It connects to Watt Stopper power packs to control the lights in the room.

I use a wireless switch, mounted on the wall, to turn on the lights, and a motion detector mounted in the opposite corner of the room. The motion detector connects to another room controller, which transmits the status of the motion detector back to the main room controller. If no motion is detected in the room for 15 minutes, the lights turn off. If you move during the 15 second period after the lights turn off, they will come back on.

I bought a batch of Honeywell motion detectors off of ebay for a good price, but I had to set them to the highest sensitivity (and I installed the non-"pet-immune" lenses) so even small motion will be detected. If I were building a security system, I probably wouldn't want the occupancy detection to be so sensitive, because it would cause false alarms, but in "vacancy" detection, it's better to err on the side of falsely detecting someone in the room, rather than the other way around.

I haven't calculated the energy savings, but the main light fixtures in the kitchen (there are two) each have 4 fluorescent tubes (high-efficiency T8) with electronic ballasts. That's about 256 watts, I guess, so if the sensors turn off the lights for an extra 1 hour a day, that's about 1.8 kWh of savings per week, or about 21 cents a week in electrical savings. If the other can lights are on, and perhaps the ceiling fan, too, the savings could exceed that. If I used incandescents the savings would be higher, too. That's not a very compelling savings by itself, though, even with the longer lifetime of the bulbs factored in. I guess in a commercial building or a warehouse, the savings could be a lot more.