Newstips Bulletin Special Reports from 2015
As trends go, the Internet of Things is slow to grow & remains for the moment largely an enthusiast niche. Much of their enthusiasm seems based on the idea that your home or office can be a “fun” peripheral for a smart phone. Others hesitate, concerned that a “Russian hacker” bogeyman can find ways to turn that control to his advantage & against yours. In practice, the category has yet to identify non-trivial, non-frivolous, necessary work that can't be done without it. The architecture has more potential than participants in the category present. Its controller-connected sensors & actuators in many ways parallels electronics in today's cars. Sensors already on the market can detect temperature, humidity, fire, smoke, CO, whether or not a person is present & often more. Actuators that are switches or sockets (as opposed to those that simply attach to & through those) can turn lights on & off, move shades up or down, turn water on or off, trigger audible alarms & so on. Controllers have decent abilities but today, no truly intuitive user interaction. If we abandon the idea of remotely controlling such a system & protect it behind a firewall on an intranet, could it be more useful than the examples that vendors present? Simple things like ringing a doorbell because somebody's at the door, whether or not they push a button… like integrating online weather forecasts with local sensor data to control the scheduling of plant or lawn irrigation… like comparing window glass temperatures inside & outside with sun-angle tables & glare detection to control blinds & fans… in other words, giving these systems real jobs to do with real purpose… these approaches make an IoT worth considering as a productive product category.
In high-end audio, more purchases fail to happen as a result of one single element than for any other reason. They call it WAF (for wife approval factor; we prefer spousal approval factor); if the word ugly comes out of the spouse the gear doesn't stay in the house. Beyond HiFi some of that influence is slowing adoption of home control systems because of the white plastic blocks & blobs that appear at or near windows, switches & outlets (for example) & the control elements mounted on tables or walls. Major established brands (Honeywell & Lutron are good examples) are doing more to integrate local communications over Z Wave, Zigbee or WiFi, for example, as an intelligent way to avoid décor disapproval. The first few generations of CFL then LED light bulbs also faced aesthetic challenges; consumers at large are hard-pressed to say why they don't choose these except as “I just don't like them”. Innovators tend to be more sensitive to engineering concerns than to aesthetics so it's often the case that a pioneering product will fail to become a marketing success because a competitor was able to make the same functionality come true more attractively; that's just the ugly truth of it.
There's a wee bit of bait & switch in residential generators using “unbundled” pricing tricks like those cell & cable companies use; consider that a disclosure. In the past, when we priced generators for whole-house backups (not selective, which can needs special wiring), it cost $15,000-20,000 to reasonably back up a typical home with a 200A utility feed. Doing that today seems to cost $4,000 though it's really closer to $7,500 & may approach $10,000. Here are some of the extras: pad creation, mechanical installation, gas line extension & connection, electrical rewiring, manual or automatic transfer switch, starter battery & authorized-dealer certification. Natural gas & liquid propane are the usual fuels (with some dual-fuel options) so paying for & installing an LP tank may add to that. Liquid propane has a greater energy density than natural gas so any given generator delivers more power using LP than with natural gas; they're advertised using the LP power output rating. There are other fudge factors, too; for example one product rated 20KW on LP is rated 18KW on natural gas while also being rated for, respectively, 83 & 75 Amps; note that for 120 Volts these translate to 10KW & 9KW respectively. In more direct terms, it's a 75-Amp backup on a 200-Amp utility feed. The smallest generator able to actually produce 200 Amps is called a 48KW model; it's a lot larger (in part because it uses a water-cooled, not air-cooled engine so it needs a radiator, a little quieter & costs $11 thousand more. In a sizable all-electric house that could be a requirement if you intend for everything to be turned on & running all the time. With a little self-control over how many big power-user appliances you allow to run at one time during a blackout a smaller system may fit. There's also some shifting underfoot in that more efficient appliances now available can further reduce electrical usage, as can a more aggressive intermix of gas appliances. If power reliability at an address is likely to be low enough to create opportunities for blackouts, an appropriate generator can make it a considerably smaller inconvenience.
One way or another, workspace productivity gets watered down when you have to wait before the morning shower is warm enough to enter; either you're getting up a few minutes earlier & sacrificing rest or you're arriving a few minutes later & sacrificing work; either also adds stress. That got us looking at newer tech to get hot water there faster without major penalties on the energy bills. The investigation brought in a double focus: tank versus tankless & unidirectional versus recirculating systems. Classic water heaters maintain multiple tens of gallons of water at a deliverable hot temperature by constantly reheating contents as they cool over time. Most in older homes only flow outward though some larger homes may incorporate recirculation pumps or down-line booster heaters; these come at increased energy costs. Tankless heaters from brands like Rinnai & Navien are more thermodynamically sophisticated. Heat exchangers (working like a cars radiator or a CPU cooler in reverse) run water through parallel pipettes embedded in metal housings that help optimize the heat transfer into the water from electric or flame sources for very rapid response. That's better for efficiency than keeping a tankful hot but the bigger tricks follow. A small feed back into the heater from the far end of the hot water run means occasional bursts of pumping can help the water waiting in the feed pipes stay warm; that's a lot less water than in a tank. Economy modes let the water in the pipes get a bit cooler for times when, for example, distant guest rooms are not in use or the time of day makes the need to shower unlikely. With any tank or tankless water heater in any kind of installation, the biggest trick for quick shower readiness is to put the water heater close by.
We spoke with Gary Gordon, a New York based professional architectural lighting designer whose book we reviewed several weeks ago, about how the newer technologies, personal preferences & other factors impact design plans. To be fair, his overriding rule is that lighting design always starts with the space, never with the technology. We stipulated that & asked, if a space calls for it, how would he see deploying edge-lit lighting panels (with a shape & geometry similar to foam-core board but with the brightness of light bulbs & beyond across their surface. He responded that most use of edge-lit panels so far has been under counters or under shelves; he could see it being embedded in a ceiling but the “tone” might feel commercial or industrial; that they are too bright to be placed within a direct line of sight; but that an angled strip at the top of a wall near the crown of the ceiling might make sense. He was very specific that edge-lit panels would not be ready for significant deployment until they were available with higher CRI (color rendering index) values. We asked about daylight color temperatures for kitchens & bathrooms where applying makeup or preparing food could be misled into bad results under amber-tinted warm white lighting; he said that people tend to be uncomfortable with actual daylight color temperatures & recommended a compromise between daylight & warm white.
Most home control software exists in the form of apps modeled after remote controls or alarm system interfaces (so & so a trigger results in such & such response); the more sophisticated alternatives are still relatively primitive. One shortcoming is in tracking changes; where the rate of change or degree of change of a temperature may be significant even if the temperature itself never reaches a trigger (for example) there is nothing built in to remember last readings or to derive a synthesized value like rate of change. Twin switches (for example, photoelectric beam breaks or driveway hoses) should be able to tell the direction of travel, not just the presence of something, but that also is unnecessarily difficult to accomplish. An overnight rain read by soil moisture sensors at 4am as enough for the day cannot be because such decisions do not endure past the next time the sensor is read. As a programming language, even VBA offers a layered if-then-else structure, local & global variables & more elements of decision finesse that we would expect of a mostly autonomous home or workspace control system.
A sensor-rich environment quickly emerges as a necessity for autonomous home control & in all the various protocol tribes, sensor designs tend to be straightforward. There may be more than one sensor in a package (temperature, humidity & illumination may, for example co-reside) that also contains a power source, a small controller & a communications link. These are what engineers call “slap-together” product designs, combining common elements in easy, common ways, often with a priority on reduced power consumption for extended battery runtime. It seems that thinking about it stopped there. It would be very simple to add (at only trivial component or power costs) data on the rate of change, direction of change & degree of change of the reading. You may note that this is parallel to our report last time on the inability of contemporary control software to derive this data. Smarter sensors can provide significant new information even to less sophisticated controllers. This primitive distributed processing approach also puts the calculations of the additional readings into endpoint firmware, making the ultimate reliability of the system less dependent on user programming competence.
There's a recognized “new toy” effect among youngsters where a new toy will be immersively enjoyed at first then retired to essential obscurity & rarely if ever played with again. Our contacts in the lighting industry tell us that they see a similar pattern with the specialty bulbs they build for people to control through smart phone apps. Initially, users install the bulbs & their gateways & use those apps to change the glow but before long it becomes too much of a nuisance to get the handset, load the app & use it instead of just hitting the wall switch. Like many new technologies that end up being application-driven, the absence of an obvious & accessible application for controllable lighting is thwarting any productive ongoing use. As better control system implementations emerge & involve more sensors, the lighting pros expect renewed engagement with these controllable lights. One often-cited scenario is making a light smart enough that if you wake up in the middle of the night to go to the bathroom the lights won't turn on at full & blinding brightness.
As seen by most people, RFID is a close-range proximity technology where a touch-free credit card or an employee ID tag has to be brought right up to a reader, but at UHF frequencies, RFID can work from tens of feet away, as in E-Z Pass. RFID tags can be associated with cars, with pets & with people as part of the sensory network of home control & automation. When your car comes into the driveway, your garage door can open & lights turn on for safe passage to the house. When you come to the door your RFID tag can get the deadbolt to unlock. The RFID industry is only just beginning to become aware of its nascent opportunity market in home control; that's probably for the best since controllers & their software are, so far, not quite ready to recognize RFID recognition; for the moment, it's pioneering turf.
Odds are that the white on any screen you're looking at right now is due to LED edge lighting, where whole areas light up because LEDs at their edges have their light dispersed through a thin pattern of micro-lenses in a thin, usually inflexible sheet. The technology is new & early products had less than wonderful white quality (CRI) so you will tend to see these lights today mostly deployed under shelves or behind countertop patterns. Their light intensity tends to be natively strong; most panels never run at full brightness & designers avoid putting them at eye level. A cousin of the edge-lit panel, the LED bar light, is something like the lights at the edge with the panel removed, replaced by a rod of glass or plastic & may include diffusion or optical effect treatments along its length. An LED bar light placed at the crown of a ceiling with its light directed upward provides a way to cast widespread soft lighting into a room. While most edge-lit panels or rods are built to order, some do appear in home lighting product retailers.
The Dewar flask, the vacuum bottle & the Thermos bottle are early examples of ways in which thermal isolation helped contents limit their heat exchange with the outside environment; hot things stayed hot & cold things cold much longer with them than absent their help. Insulation has also been a major factor in energy conservation in home appliances & home infrastructure items like water pipes or water heaters. Insulation may be added during manufacturing or as an on-site retrofit; is it worth it? The economies of insulation strongly depend on the costs of various forms of energy sources at the root of the initial temperature changes created by or carried by these items. For new construction, for example, the payback of insulation costs may happen as soon as 18 months or as long as 15 years, so the economics ride with the intent of continued occupancy. What's true for heat ducts or plumbing pipes may also prove true for workspace gear where, for example, heat from equipment adjacent to a user may trigger a need or desire to adjust an entire room's temperature. While it's unwise to contain heat within equipment cases, it could certainly prove expeditious to find ways to direct it away from users by selective insulation & engineered airflow.
Early technologies seem to engender brute-force solutions, as we saw in the early chargers that use power regardless of the charge status of the gear they feed. There's an even more familiar, more enduring example that you touch every day: hot water. The more the temperature of the water in the hot pipe is above what you want at the tap the more unnecessary energy you use putting it there in a mix with cold water. The biggest challenges are in tank-based hot water systems which have to keep water hot enough to kill microorganisms; we know of no tanks that address this by preheating the incoming supply to a higher temperature than the tank itself maintains. Tankless systems are demand-driven & only heat incoming cold water when a tap turns on to create the outflow that draws the inflow & in so doing, triggers the heater; natural or LP gas or electric models are all available, some including lifetime replacement elements & some cost less than $200/year to run. For any new construction either indoor or outdoor models are easy to accommodate & either one is much more efficient than the traditional brute-force approach of maintaining a too-high temperature for tens of gallons in a tank. The idea of trimming back on overkill may also apply to lights you put on dimmers, the number of burners you light on the grill & how many of the PC peripherals you only occasionally use are nonetheless turned on all the time. We'll have a related hot water update in 2 weeks.
The lighting industry speaks about three phases for LED lighting. The first phase, happening now, is the socket phase, centered on lamps that fit into existing sockets that were designed for earlier technologies, like screw-in bulbs or fluorescent tubes. When 60Weq bulb prices recently dropped below $5, retailers report to us that consumer purchasing skyrocketed. There's still some distance between these sticker-un-shocked adopters & the era of socket saturation (when there will be few sockets left to fill). The second phase of LED lighting, the fixture phase, is well underway for commercial, industrial & infrastructure lighting, especially with replacements for troffers, downlights & street lighting. In this phase there are no bulbs or sockets, simply LED emitters wired into installable fixtures with life expectancies of decades. A very few socket-less LED fixture are available to consumers or residential applications. The third phase, more evident for now in vendor demonstrations than in actual implementation, is the full integration phase where rather than attaching to walls or ceilings, lighting becomes a part of them. While technological advances continue, there are few unmet technology hurdles.
How do you get water hot? Water heaters with tanks aren't the only option. Tankless (on-demand) systems enjoy a clear energy benefit, though there are trade-offs in both pricing & deliverables. If a system is to always meet a home's peak demands for hot water, it's the sustained flow (not peak flow) rating of an on-demand system that comes into play. Any open-loop (like at your grandma's house) system always has to push cooled water through the pipes before the hot water reaches any given faucet. In a closed-loop system (with return pipes & constant cycling of water through them to keep it hotter at turn-on at any faucet) the gallons of water held in the pipes are in their own way a tank, suffering the same inefficiencies. You can get tankless systems that use electricity or gas & that mount indoors or out (in climates where freezing the water in the lines isn't a factor). For high-demand scenarios (multiple showers plus dish & clothes washing at the same time), condensing systems preheat groundwater by routing it past the flue before sending it to the heat exchanger, making efficient use of what would otherwise be waste heat. As we prepare our editorial project house, we plan to incorporate a gas-fueled outside-mounted condensing on-demand water heater; we'll discuss maintenance concerns in future coverage. Note that TCO (total cost of ownership) applies to longer terms than the 3-5 year occupancy of many homes.
In weather, a micro station is a single monitoring point intended only to report the current conditions at its own location. It may know the current temperature, humidity, air pressure, etc. but it has no awareness of weather patterns. Weather patterns as seen by satellite, for example, or as aggregated from multiple radars or other monitoring platforms is a very good indicator of what's probably ahead. The closest hybrid we know is the AccuWeather MinuteCast which is precise down to a single address & embeds 120 entries of what to expect each minute for the next 2 hours. In a home automation context, micro weather data is useful for determining any immediate conditions to which a system should respond but it is not useful for determining how it might prepare for what's coming. Sudden storms are a dramatic example of the impact of macro weather events; less dramatic but also relevant are decisions about whether to water lawns & gardens based on the likelihood of rain, or to take advantage of a fireplace rather than adjusting thermostats, or to run attic vent fans rather than increasing air conditioning.
Some police dash cams today can perform limited OCR to recognize license plates; we learned that now, real-time OCR processing for standard IP video has become a test bench reality. This may address some challenges for both home automation & home security. A driveway camera able to read a license plate can securely automate the opening of a selected garage door for that specific vehicle. It could identify various delivery trucks (UPS, FedEx, Post Office, DHL, a personal laundry, utilities, etc.) or, if unknown, log both text data & a video stream while securing doors & notifying occupants. It would also let you send a bar or QR graphic to an expected visitor's phone that would, for a proscribed period, let them into an empty garage space or the house itself; it wouldn't be hard to forward video to the homeowner to authenticate that the person using the code is the person who should use the code.
Ceiling fans may cool people (evaporative “wind chill” effect) but they can't cool rooms; their effects on air motion within a room, however, can easily impact the control a thermostat exerts on an HVAC system. Thermostats get mounted on walls where people can see & adjust them but in many rooms, they are well below ceiling heights so they sense temperatures lower than the true average temperature of the room. One of the jobs of a ceiling fan is heat destratification, stirring the air so heating doesn't end up impacting only taller heights & cooling doesn't get compromised by the effects of volumes of warmer air above. Intelligent control over fan speed & direction (recent research suggests not changing direction in winter) requires temperature & humidity sensors at several locations within the room & at several heights between floor & ceiling as well as an occupancy sensor.
One leading reason for hot water heater service calls is scaling, which got us exploring many water treatment options with the experts at Kinetico. We specifically asked how to reach a sweet spot for maximum longevity with minimum maintenance on the water treatment products; their first answer is that every well is different & from block to block, city systems may vary. There are 3 types of pre-filtration using different cartridge filters (sediment/particulate traps, carbon filters to reduce chlorine & filters to remove ferrous & ferric iron); larger filter housings to hold more cartridges can reduce how often they need changing. If there's any significant microorganism presence, UV countermeasures are available. Next, while descaling-only solutions exist, they tend to be expensive & require frequent attention. The more common ion exchange softener removes magnesium & calcium but requires occasional salt pellet refills; we learned that it's wrong to put more than 1-2 bags in at a time because more encourages hardening that reduces efficiency. Electric timers (Kinetico systems use water-driven flow metering instead) are the most likely point of failure in these systems. Beyond washing laundry or dishes or ourselves, many people add additional purification for drinking & cooking through point-of-use filters; the ones from Kinetico use reverse osmosis & may last 10-15 years if their membranes are replaces at 500 gallons or 1 year.
We earlier covered the difference between micro-weather (reported from on-site monitors) & macro-weather (derived from areal resources including satellites & radar, so able to indicate what's coming). In exploring weather information API options to being external data into home automation we consulted relevant sources within AccuWeather where their MinuteCast service is location-specific, down to a single street address or latitude/longitude to 2 decimal places. In discussing the processing that a home control system would have to do with source data after gathering it we learned of their plans to enrich the API interface; the change will provide more distilled, better-nuanced data based on them performing the analysis of the source data. So, for example, an API call could return a value that reflects either significant anticipated rainfall or an extended hot, dry spell, useful to a lawn irrigation controller. Anticipating temperature changes could allow HVAC & ceiling fan controls to make less abrupt, gentler shifts to help avoid the energy & comfort costs of more abrupt transitions.
Credit very “Green” builder Don Cerra for this idea. Well water comes out of the ground tens of degrees cooler than interior or even protected (non-freezing) areas like crawl spaces. With a tankless hot water heater, a warmer starting temperature for its water supply means it can reach its target temperature at a considerable energy savings. By installing a buffer tank in a protected crawl space & looping it into the supply line to a tankless water heater, two benefits ensue: the no-longer-colder water supply reduces hot water costs while the additional thermal mass of the tank helps normalize its immediate environs for some marginal annual improvement (given that cooling is more expensive than heating) in HVAC energy costs.
Where Zigbee & Z-Wave dominated new home automation products earlier in the year we now see an increasing number of significant new products choosing Bluetooth Smart Mesh as their local wireless protocol. In a BT Smart Mesh network, adding nodes both adds range & speeds responses. Endpoints can accept & store commands that continue to govern their operations until those commands are altered, so there's some independence from constant connection to a controller. Long operating periods using relatively tiny batteries are also a factor, as is interoperability with many handsets & tablets, simplifying app development. Hacking into home automation products using BT Smart Mesh becomes quite difficult given the zero to scant time they connect to IP networks for any purpose, an inherent security & privacy advantages over competing protocols. Also, the chips needed to build BT Smart hardware promise generally higher availability than those used with the home control protocol alternatives. Bluetooth has come a long way since headsets
Without regard to which technology is invoked to the purpose, the ability for a home control system to have precise & constantly updated location information about specific people, pets or many kinds of movable property can be a huge benefit to creating autonomous residences. Selectively moderating heating, cooling & lighting, for example, can both reduce energy consumption & extend the period before maintenance or upkeep or replacement are again necessary. A firm awareness of who is & who isn't within the domicile can help a system secure door locks, recognize intruders & respond more appropriately when emergencies arise. Knowing which car is entering or leaving a driveway & when a driver's car door swings open or closed can automate the operation of garage doors, connected garage door locks, lights or family status updates. Locating pets indoors or out becomes easier. Tracking dangerous items like guns or valuable items like passports or strongboxes also means a more immediate ability to respond, especially when the locator for the person allowed to move these things is noted as absent. We expect non-intrusive precise position location on this level to become more widely available & affordable during 2016.
When is a room empty of occupants? Commercial buildings have long used vacancy as a trigger for lighting controls, often with a combination of PIR & ultrasonic sensors that aren't always right. Hotel systems primarily use PIR & when they sense a vacancy, turn off the TV set, turn off the lights & relax the HVAC settings but those sensors can sometimes be fooled by somebody in a bed or a chair, relatively motionless & dressed in a way that masks body heat. Beyond inconveniences, a false positive vacancy (meaning there really is somebody still there) in some circumstances can lead to unnecessary danger when first responders aren't alerted to the location of somebody needing rescue. Upcoming technologies read pressure patterns on a floor, patterns in derived video (including deliberately lowered-resolution or defocused images that disallow direct privacy intrusions) & volumetric (x/y/z-axis) PIR to sense occupancy.
Commercial buildings provide increasingly automatic control over lighting (at a significant cost that's soon amortized by energy cost savings) but they don't do it blindly. Sensors determine ambient brightness, room occupancy/vacancy & sometimes more; controllers also take into account normal patterns of usage against the clock & the calendar. Residential lighting shows early signs of the same kinds of intelligence through sensors & schedules, but more from end-user DIY projects than by lighting system specialists. Homes have fewer lights, less opportunity (especially once converted to all-LED lighting) for savings through on-time reduction & more confusion. Should control be exerted over the switch or directly over the bulb? It's likely one answer to that will be in an autonomous fixture that can turn itself on & off as appropriate both as a result of its own sensors & from an awareness (both by reading other sensors & by getting, for example, away-date info from user calendars) of when it's smart to be on or off.
It's hard to imagine a circumstance that would lead to a PC needing a heater, but the need for cooling is omnipresent; the solutions include fins & fans plus coolant loops; if they're very clever, PC case designs can also help. Home HVAC systems are based on the same 3 elements plus refrigeration (using compressors & evaporation) for cooling plus, unlike the PC, a base need to also address heating. That need to exchange heating or cooling at different times & in opposite directions makes simple ventilation an iffy contributor but it does offer homes an option that's not much help for PCs: thermal isolation beyond simple insulation. A home gets the ongoing bake-oven effect of direct sun exposure; housing (wall, window & roof) choices can have enormous impact on how much or how little of that heat remains in the structure or is radiated into its interior. For internal sources (especially lighting), progress in PC designs demonstrates that improving efficiencies & reducing power consumption can significantly reduce how much heat needs to be exorcised.
Component-level compass sensors are all over smart phones so they're now readily available to consider for home automation applications, where there are many reasons for wanting to know the directional angle of things or when that angle is changing. Just about all open-door sensing to date is done with microswitches or leaf switches or 2-part magnetic sensors providing only a binary open or closed status. If a compass sensor is embedded (potentially out of sight in the top of a door or gate or double-hung window) it can provide information on both specific orientation & changes in that, even if changes don't result in being fully closed. Beyond windows, gates & doors, compass sensors can also report on where a wind vane points & perhaps even whether a visitor at the door is carrying a large mass of ferric metal.
Discomfort & stress can both hurt productivity; there's an under-reported source for both in the space between your roof & the sky. Traditional approaches cover the wooden roof with felt then add asphalt shingles; these may keep water out but they have little impact on thermal factors. Direct radiant heating from the sun doesn't end with the shingles; it finds thermal bypass conduction paths (highways of hot) along & through both the roofing boards & the trusses supporting them, then down into the structure; commonly, the underside of the sun-heated roof board re-radiates into the attic space. One way to foil the effect uses foil. Heat-shedding radiant barrier foil atop the roof boards & under the roofing can significantly reduce the degree to which radiant heat can become conducted heat. When the top layer is a raised ceramic-coated steel roofing material with an air gap beneath, there is additional rejection of IR heating, the conduction is transverse across the steel segments & an air gap between the back of the roofing & the foil beneath cancels the thermal bypass (breaking the conductive heating connection) inherent in direct-attach roof materials. We've seen cases of homes experiencing hot-month energy consumption reductions of more than 100 KWH, roughly 15%, through reduced HVAC demand. An estimated $100-150 annual power cost reduction may be the smaller part of savings when considering how relaxed HVAC demand translates into reduced HVAC repair & replacement costs over time. Also, selecting the right foil & roofing products can yield dramatically longer terms before their repair or replacement needs are likely to occur.
Now that days are again starting to get longer it's a good time to think about the angle of the sun, a factor that can impact the efficacy of solar power panels as well as of treated windows. It's possible to calculate the spherical angle (azimuth & elevation) of the sun (NOAA, for example, offers an Excel program to do so) based on latitude, longitude, date & time. That still leaves unaccounted variables, like atmospheric refraction (ray bending), optical occlusion or diffusion (cloud cover, fog or precipitation). The ever-changing incident angle of sunlight striking a flat surface (like a solar panel or a window) is compounded by being slightly different from point to point on that flat surface. Some automation systems depend on doing all the computational math of this approach while others instead rely on light sensors behind tubes or shutters that act as blinders. Integrated & MEMS sun position sensors are also in use for such applications as car air conditioning controls; we have not discovered any for residential HVAC or window systems.
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