By bridging the division between communications and computing, Apple’s iPhone has taken the mobile technology world by storm. It’s a cell phone, but much more, offering PC-like functionality in a handheld package. So what does it have to offer solar enthusiasts and RE installers? A lot.
Already On Board
The iPhone has taken smart phones to a level never before seen. For installers and solar geeks, this single device can replace a day-pack full of instruments and reference books. While it may look identical to the older 3G, the latest-generation 3GS features:
Then, there are the apps, third-party-developed software based on the iPhone’s software development kits—tools, templates, and examples for building software for the iPhone operating system.
Most apps that can be used for solar assessment use the iPhone’s built-in sensors to perform their feats. These sensors include a sensitive accelerometer that detects position and movement, global positioning sensor (GPS), light sensor, proximity sensor, and a camera.
Sounds sophisticated—and potentially expensive. But downloaded from Apple’s iTunes store, more than 90% of the apps are less than $10 and thousands are free. As an added bonus, the iPhone—offered in 8-, 16-, and 32-gigabyte memory options—has terrific storage capacity for apps (and other files and media). It also will synchronize to your Macintosh or Windows contacts, notes, and calendar, in addition to your iTunes library, and allows you to check e-mail and browse the Web using your cell phone signal (or 3G or wireless Internet access), making working on the fly a snap.
Sun Tracker ($14.99) For solar installers and DIYers, this is the “must-have” app that incorporates every sensor and nearly every feature of the phone to provide accurate site assessments and reporting. Start by naming your site and then the GPS plugs in the latitude, longitude, elevation, and heading. Next, set the array azimuth and tilt (or, if you are working with a tracking array, select from single or dual-axis tracking). Pick the closest weather station from the drop-down menu. You may optionally enter a per-kWh cost of energy, and the model of PV module and inverter you’re using, from a built-in database with a wide variety of module and inverter manufacturers and models. Everything you need is loaded into the iPhone—no network connection is necessary to complete a site assessment, so you’re good to go even in remote locations. Sun Tracker will also run on the iPod Touch.
Here’s how it works. After setup, you scan the skyline. Press the scan icon to launch the heads-up display. Wait for the start tone and then simply trace the skyline using the cross hairs. (With a 3G, you must first set the “start” and “stop” points and then perform a smooth scan at a constant rate—with a bit of practice, it yields very good results.) As you trace the skyline, Sun Tracker records the elevation and heading of any obstructions.
When complete, you end up with a sun plot for your location, showing that day’s sun path compared to winter and summer solstice sun paths. A scan can be completed in about 10 seconds, so you can quickly evaluate a number of potential locations and easily choose the best one. You can also animate the sun’s arc over your scan for different months to see variations in the site’s solar exposure over the seasons.
Sun Tracker software also allows you to superimpose a panoramic photo of the site (see AutoStich and AutoPan below) on your scan with the ability to edit the photo size to get a good fit. This is generally only needed for presentations; the trace should be your guide, rather than the photo.
Once you settle on the array location, running the Analysis feature—which takes about 30 seconds—produces a graph showing the percentage of solar energy captured per square meter per month, the percentage of shade derating per month, and percentage of available sun hours for each month.
You now have the option to produce a two-page presentation report with your company name, logo, presenter, and customer names. These documents can be e-mailed right from the phone back to the office and/or customer.
Another nice feature of this app is the heads-up display. Just launch the camera and hold the phone up to the skyline or roofline: the display shows exactly what is behind it, allowing you to read azimuth and altitude angles as you move the cross hairs around your field of view. This also works on the 3G for scans and elevation. But only the 3GS will also display heading to site along a building’s eave and instantly get a calculation of the roof pitch and orientation azimuth at a glance—with your boots on the ground!
Sun Tracker is a remarkable tool that rivals all the competition—and at a much lower cost. It has the capabilities required by professionals, but its ease of use and price puts it in reach of the solar enthusiast. One minor limitation is that it can be awkward to position yourself at array level to perform the scan on a rooftop, but by lying on your side, you can get within 12 to 18 inches.
Solmetric, the company that brought us the SunEye digital site analysis tool, recently acquired Sun Tracker and will begin marketing the app under its own brand, SolmetricIPV. Users who purchased Sun Tracker will be able to continue accessing updates.
Sun Seeker ($2.99, 3GS only) An assessment tool that spans several applications, Sun Seeker allows you to quickly check building overhangs and sunlight penetration into a structure, as well as site a solar window. The opening screen displays a grid of the sky, with latitude and longitude readings; the sun’s current position and daily path; winter and summer solstice curves; sunrise and sunset times; real-time solar azimuth and elevation; shadow ratio (sweet!); and sun-path length. A summary screen reports that day’s Sun Details.
The third screen is a three-dimensional heads-up display that superimposes the sun’s path and solstices on the real-time image, along with the elevation and azimuth of what the cross hairs are pointing at. This allows you to instantly see the relationship between the target object and the sun’s paths. You can also trace the sun’s path on its curve line and see what objects will cast a shadow—and where you need to move to avoid it. You can capture the screen to your iPhone album or e-mail it directly from within the program. You can also easily display the sun path for any day you select. A real bargain for what it does.
AutoStitch Panorama ($2.99) While this isn’t dedicated solar software, AutoStitch is a useful partner. It allows you to take a series of photos and stitch them together, enabling 360-degree panoramic images. The accuracy of this software is remarkable—it’s less distorting then anything I’ve seen at any price for a computer! A panoramic image can be imported into Sun Tracker and overlaid on the skyline scan.
AutoPan ($1.99) Created by Sun Tracker’s developer, this tool automatically snaps photos at optimal intervals, using the phone’s compass as you scan across the landscape to set up the perfect panorama in AutoStitch. Tip: Keep the Elevation at 30° as you pan—this minimizes stitching distortion and puts the bottom of the screen at 0°. Well worth the two bucks.
MotionX GPS ($2.99) Far ahead of most handheld GPS units, MotionX GPS integrates with Google Maps. With the 3GS, the maps even rotate as you do, so the map is always facing your view. Perfect for figuring out your coordinates when you’re trying to track down that property in the boonies or find your way around congested city streets. It taps into satellite data and can lock onto a satellite just about anywhere on Earth. If the satellite signal is blocked, it switches to cellular tower triangulation to help you find out just where you are.
iConvertIt ($1.99) An affordable unit converter, this program contains 19 categories, each with the units you are most likely to need. For example, use this to convert from square meters to square feet, or Btu to kWh, etc. Simple and fast, using the classic iPhone “roller bar.” It does a reverse convert with one keystroke.
Equivalence ($2.99) A step beyond iConvertIt into the more esoteric and scientific conversions and units. Aimed at electrical and mechanical engineers, it can cope with mass, magnetic fields, and flux and insulation, just for starters.
TiltMeter Pro ($0.99) Perhaps my most-used app, TiltMeter Pro contains several levels in one program: a bulls-eye level, digital angle level, and a virtual bubble level. Each one can be set to display in degrees, pitch (x:12, x:14), percent, and radians. After careful calibration, accuracy is spot-on. Plus, it can log and e-mail readings. Handy features include a reading lock at a key press and an auto-lock, which waits for a stable reading (for you to quit moving) and then locks the display. Terrific for measuring in out-of-sight places, like under an eave where you cannot see the display (it is accurate only on the side of the iPhone that does not have the volume key). You can also set a reference point to see how far off the mark you are. Perfect for level, plumb, roof and array pitch—even for hanging a picture frame straight!
Ecalcs ($3.99) An often-used tool on my iPhone, Ecalcs does the calculations for Ohm’s law, horsepower, voltage, current, kVA, kW, transformers, voltage drop, and wire size. Each of these categories contains a good depth of detail and many factors to consider—far too many to list here. If you do any level of electrical work, this app will be helpful.
Conduit Fill Calculator ($2.99) Based on the 2008 NEC, Conduit Fill Calculator helps you figure proper conduit size and fill factors. The database contains 50 conductors and 12 types of conduit. You can mix conductor types and sizes and get quick field sizing.
Wire Size ($2.99) Also taking a page from 2008 NEC (specifically, table 310.16), Wire Size calculates current and wire size from AWG 18 to 2,000 kcmil, taking into consideration voltage drop, ambient temperature correction, and number of wires in a raceway. It’s easy to use and fast.
Decibel Meter ($1.99) Accurate and fast, with optional displays and peak capture, Decibel Meter is useful for figuring out sound mitigation effects on gensets and general decibel measurement needs. My trusted ±2 db meter and the Decibel Meter were within 1 to 2 db of each other when I measured the constant sound from my bench grinder, and the app is much faster in capture. It’s hard enough to find a db meter with this many features, not to mention at this price!
Flashlight & myLite (Free) Shed a little light on the situation with a flashlight app. These programs fill your iPhone’s screen with bright white light (or, if you’re in a festive mood, pick from a selection of colored screens). Plus, the price is hard to beat. About as bright as a single LED flashlight.
Brushes ($4.99) Although there are numerous drawing apps that are much cheaper, if not free, Brushes is a powerful drawing tool. I use it in the field to make sketches or notes with a sweep of my finger. Plus, your Van Goghs can be e-mailed.
Graphing Calculator ($0.99) Does about anything you need in a graphing calculator. It’s worth the buck even for simple math, if for nothing but keeping running totals on-screen.
Spell Check ($0.99) A spell-checker and dictionary, with pronunciation. Its vast database does not require an Internet connection.
Air Sharing ($4.99) A major shortcoming of the iPhone is its poor ability to import documents from your computer and then read various file types. That leaves you e-mailing the doc to yourself and then crossing your fingers that the phone can open it. Air Sharing makes this a hassle of the past. Connect via Wi-Fi to your computer (Mac or PC) and simply drag and drop files. Air Sharing allows you to organize them and offers a reader for most formats.
A user-friendly interface that’s packed with apps is sure to be a crowd-pleaser, but the iPhone isn’t without its downsides. Currently, AT&T is the only available cell service provider for iPhones, leaving no other options or competition. Outside urban locations, where cell towers are fewer and farther between, getting a good connection may be an issue.
The iPhone’s big screen is a beauty, but combined with its powerful processor and typical heavy use of apps, the battery is typically drained in less than three days. You may find that an external backup battery is useful. (However, many external batteries also integrate the battery into a case, although this can interfere with using the level and angle tools.) Prices range widely, but the best values I’ve found are the Griffin TuneJuice ($30) and LuckyPacks’s I-UP 5400 ($60). The TuneJuice, which uses four AAA batteries, will add about 60% to 70% to the phone’s typical run time, more if you carry extra batteries with you. With its 5,400 mAh, sealed lithium-ion battery, the I-UP will increase the phone’s run time or completely recharge it six to seven times. However, beware: Many external battery packs for the 3G will not work on the 3GS. Be sure to choose the right backup battery for your model.
When it comes to software, there’s only one real hitch: The app costs listed are volatile. There are frequent sales, intro prices, and inflation. However, most app developers aren’t yet charging for upgrades. So if you get introductory pricing, you can end up saving money on future expanded and improved releases. Plus, most developers listen carefully to user feedback and massage their products accordingly. The applications and memory are what make the iPhone so powerful. The least-used feature on mine? Making phone calls.
Jeff Oldham is the owner of Regenerative SOLutions and a solar contractor, with more than 30 years experience in RE and sustainable development. He lives off-grid with solar and micro-hydro. His work is 60% off-grid and 40% grid-connected, with about half of it international, primarily in Latin America.