The Holey Story Part I -> Dreaming Of Football In The Boonies

The Holey Story begins....

We were out in the boonies…far out in the boonies….and Paul was daydreaming

“I have a dream” gushed Paul “a dream of football”

“ooooookay” I responded, trying my best to sound supportive. Clearly we’d been spending too much time out here and Paul was going nuts…but I thought it safest to humor him at this point.

“No, no, no”, he answered excitedly (and with a bit of crazy eye in his expression, I thought). “You don’t understand”. “My dream is to watch 3 football games in one day while boondocking and using the internet without draining the batteries…and I think we can do it” he chirped, skipping happily around the RV

Paul putters around tilting panels out in the AZ desert

Several things fell into place in my noggin at once. The fact that it was football season (that would be American Football for my European friends -> where they carry the ball, believe it or not), the fact that Paul had been doing covert solar calculations for several days, and the fact that he’d been grumbling about needing more Amps. At least he wasn’t going crazy…in the normal sense I mean.

As a fellow geek I was immediately interested. Not in the football, mind you, but in the concept of the usage plan. Paul explained that he wanted to watch 3 football games in a day (so, TV/satellite on) plus have the internet on all day (because knowing me well, he knew I would need something to do), plus normal boondocking usage….all fully supported by our solar system…and with the least extra expense. Now, that was an interesting problem, from a geek point of view.

It's a question of Amps, my dear Watson...

In order to fully understand the scale of this dream I’m going to throw some numbers at you. Those of you of technical persuasion will no doubt be gripped with excited interest at this point. For the rest of you, go ahead and skip to the bottom-bottom line at the end, and spend the rest of your day blissfully math-free until tomorrow’s post.

In numbers terms Paul’s dream was about a management of Amps that needed to follow the universal and oft-quoted rule of “what goes in must come out”. In this case our generation (from solar) would have to match what was going out (to usage). Ideally we wanted to end the day with fully charged batteries too, but that was what we in the business call a “stretch goal”.

The Generation Model

Panel tilting is very exciting stuff!

Our system has 600Watts of Solar Power. Using solar flux models (see our post on panel tilting HERE and the model HERE), Paul calculated the approx. solar generation we would expect in January in the SW desert with 45-degree tilt of the panels.

Approx. solar  flux in SW in Jan at 45-degrees tilt = 5.95 kWhours/m²
Our measured solar surface (6 total panels) = 6 x 0.78 = 4.68 m²
So, total expected generation on a sunny day = 5.95 x 4.68 = 27.85 kWhours

Our panels/system are ~10% effecient (this is very typical of solar systems in general. Panels only really convert ~10% of incoming flux)
So actual generation = 2.785 kWhours = 2,785 Watt Hours
This translates into ~232 Amp Hours (divide the above by 12V)

Bottom Line = We expect to generate ~232 Amps Hours of solar energy from our panels on a good, sunny day. Lots and lots of assumptions in here, but it’s a decent, simple start.

The Usage Model

Here’s where we get into the really fun stuff. We calculated our potential usage model, and backed it up with measurements done at night with our Xantrex LinkLITE monitor (LOVE that thing).

(i) Our Inverter is a Magnum ME2012
(ii) For TV/satellite we have Direct TV, a satellite dish on our roof and a Sharp Aquos 32-inch LCD TV
(iii) For internet we use a Verizon modem, MBR1000 Router, Wilson RV Antenna and Wilson amplifier (see our full set-up HERE).
(iv) We have 2 computers which each run ~3 Amps
(v) This is a “fudge factor” which includes anything else we might want to do during the day (e.g. run lights, a bit of microwave, a few hours of furnace etc.)

Bottom Line = In this usage model we expect to use ~360 Amp Hours in a full day (24 hours)

The Bottom-Bottom Line

If you put it all together this is what you get

Total Solar Generation in one day = 232 Amp Hours
Total Usage in one day = 360 Amp Hours
Total Drain on the Batteries = 232-360 = -128 Amp Hours

In search of Amps....

Now, that’s the number we wanted to be zero, ideally, and clearly we were WELL over. We have 440 Amp Hours of AGM batteries (=220 usable amp hours if you don’t go below 50% discharge, which should always be your goal with deep-cycle batteries) so we can handle the load, but it’s not where the dream wanted us to be. Clearly this needed some creative geek-thought, especially if we didn’t want to pay out the wazoo to get it done.

Coming Next -> The Final Chapter. How we solved the elusive 128 Amp Hour Gap….

RV Solar Part IV – Panel Tilting & Winter Solar Optimization

Paul and Alex go a-panel tilting

It’s been almost a year since we made the leap to solar on “the beast”. For those of you who missed the chair-gripping series I’ve got the whole exciting detail of how we decided what to buy and install in Part I (discovery), Part II (equipment) and Part III (installation). Since that time we’ve been geeking out and enjoying our panels through extensive dry-camping travels from FL to CA. I’m happy to say our panels have served us perfectly. On good sunny days we’re usually fully recharged on the batteries by noon plus the panels easily keep-up with our daytime power usage even if we’re on the internet all day. There’s honestly not much we’d change.

But there’s always an opportunity to geek out a little more. As days grow long and the sun sits lower in the sky we’ve started to think about winter solar optimization. Now solar panels actually like cooler temps (their output increases at lower temps), but they have a problem with angle which opens up all kinds of fun thoughts and experiments on tilting. And opportunities to blog, of course. So, here we go:

1/ Why Tilt Your Panels?

In winter the sun stays closer to the horizon

If you remember my lessons from last year, getting the best out of your solar system is all about minimizing loss. The same lesson applies to tilting too. The power density of a solar panel is always at its’ maximum when the solar panel is exactly perpendicular (at 90-degrees) to the sun. The further you get away from perpendicular the more power you lose and so the less power output you get. Since sun angle varies by both latitude and time of day that means your power output is varying all the time. So, how do you know what to do?

Well, in summer the sun will get pretty high in the sky and stays there for quite a few hours (as an example, here in Palm Springs it gets to ~70-degrees elevation) so your panel output will be pretty darn good even if they’re flat. However in winter everything changes -> the sun stays closer to the horizon (here it only rises to ~30-degrees) and your power output plummets. Sunearthtools.com has a really geeky cool page that’ll give you the exact angle of the sun any time of year for any direction and spot (just plug in your location):

Solar Diagram for Palm Springs, CA from Sunearthtools.com. The top line shows the sun angle in mid-summer, the bottom line for mid-winter.

How much of a deal is this, power-wise? In Palm Springs in summer you really don’t lose anything by keeping the panels flat whereas in winter you’ll lose more than 50% of your power output if you keep them flat. It’s HUGE!! To demonstrate this here’s another cool tool that’ll calculate daily flux (= an approximation of the total amount of energy hitting your panels) based on location, time of year and tilt.

2/ How Do You Tilt?

Our home-made tilt bars

The fanciest type of tilting systems are “sun trackers” that exactly track the sun all day long, but these are not exactly practical on a free-wheelin’ RV roof. Some RVers keep their panels mobile and just bring ‘em out to tilt/track the sun manually whenever they need them. With 6 heavy panels to lug around that wasn’t an option we wanted on our “beast” so it made a lot more sense for us to permanently attach the panels and look for other tilting options.

Our solution was to get the AM Solar mounts (highly recommend them, even if you aren’t going w/ AM Solar for the rest of their gear), and then add-on home-made tilting bars. Some basic 1/4″ aluminum stock from Home Depot cut to whatever length you want with holes drilled in (you can even drill multiple holes to have multiple tilt options). Combine with screw/nuts and you’re good to go!

3/ What’s The Best Tilting Angle?

If you’ve made it this far and manage to remember what we talked about in #1, then you know that what we’re looking for is to get your panels as close as possible to 90-degrees to the sun. The cool sunearthtools.com link will tell you what angle the sun gets to in your area, and some simple geometry will give you the optimal tilt angle:

At our current latitude and time of year we’re talking around 60 degrees tilt at noontime for best results. Now, obviously the sun moves diagonally across the sky during the day and rises/sets somewhat southerly in winter so that number doesn’t stay constant and the real (max. total energy) formula is a rather more complicated (the cool tool shows that). But if you face your RV East-West and tilt panels facing due south more or less at the 90-degree noon-spot you’ll get pretty darn close to getting the best out of the sun.

4/ Beware the Shadow Monster

See ma...NO panel shadows!

Tilting is just like everything in solar. You’ve got to make sure you avoid ALL shadows. Together with Marvin we were very particular when we installed our panels last year to make sure they had NO shadows from anything on the roof whether tilted or not, even with long winter shadows. I’ve seen shading models that show just 3% shading of a solar array can lead to a 25% decline in efficiency, with 10% shade producing up to 50% decline! The losses are dramatic and could mean the difference between a system that works and one that doesn’t. Even panels that have special “bypass diodes” (meant to help the shade problem) will suffer voltage loss for each cell shaded. Don’t be caught by the shadow monster!

5/ And Our Results Were….?

We conducted our little tilting experiment out in Owl Canyon BLM. Our tilt-bars only go to ~45-degrees so we knew we wouldn’t get optimal output, but we expected a pretty significant boost. Mid-morning with panels flat our 600W system was putting out ~20Amps. With the tilt we hit ~30 Amps, a 40% improvement. As the day wore on our boost got even better with the MPPT charger kicking up output to a stunning peak of~45 Amps at around noon (MPPT really shines with higher-voltage panels in colder temps). Coooool!

We plan to do even more detailed tracking experiments later this the winter and will undoubtedly share these exciting results with our readers, but for now this is a good start. There is also much more geekiness that can be done with solar so don’t expect to see the last of this sunny series.

Taking Care of Bits & Bobs…

So, we’ve been in Albuquerque for the past few days stocking up ravenously on food and pet supplies, meeting friends, eating out, planning our summer stops in Colorado (we’re spending practically all of July in the SW forests…oh yeah!) and basically just taking care, as the English would say, of various bits and bobs.

As things go, this got me thinking about other bits and bobs. So, although we’ve barely made Spring, I thought I would take the chance to update on a few items of which I’m sure you’ve been bursting with curiosity to know. Thus, with my mind psychically melded to yours, here we go:

Our solar is cranking

1/ Our Solar is Cranking – As our regular readers will know we installed 600 Watts of solar panels over winter and I promised an update. I’m happy to say it’s rockin’ and rollin’. On good sunny days our MPPT controller cranks out over 35 Amps (a nice boost) and we’re usually fully recharged before noon. During the day the system easily keeps up with our biggest usage and will happily chug along, maintaining the batteries at float even if we run TV and internet all day. We haven’t used the generator once since we started dry-camping and have no regrets or complaints.

2/ We’re Doing Fabulously on our Flip-Flop Barometer – Thanks to skill, guile or perhaps pure, dumb luck we’ve been tracking superbly well on our flip-flop barometer. The cold weather has lingered longer than expected in the North, which means our Southern route has been balmy and perfect for that 24-hour flip-flop wearing goal. So far we’ve managed to stay clear of the truly freezing and doing somewhat decently at not getting too uncomfortably hot (although we did blow through the 90′s in Texas). We’ve extended our New Mexico stay for exactly that reason, and hope to continue our perfect sockless “hot streak” through the summer. :)

Dog and beach heaven at Cape St. Blas, FL

3/ We’ve Become Doggie-Trend Spotters - It might be my superb animal instincts, but we were definitely onto something when we raved about The Forgotten Coast in Florida. Cape St. Blas just ranked one of top 10 Dog beaches for 2011 in the US and if it were up to me I’d put it in #1. In fact all the beaches we’ve raved about on the blog in the past year (Hunting Island, Cape St. Blas, Fort de Soto) are on this list. So, although we may be  out of touch most of the time in the boonies, we remain on the cutting edge of blog-breaking doggie news. You heard it here first!

It's still really dry out there

4/ It’s Still Really Dry in the entire SW – Our fire evacuation in the Davis Mountains, TX was just one of many fires that have been sweeping the entire SW this spring. Texas has had one of its worst wildfire season in years and New Mexico is also struggling with dry and windy conditions. While we were in the Gila Forest there were 3 active fires burning, and several National Forests in the Southern New Mexico area have been closed. Let’s hope we get some rain soon.

5/ Trailer Food is the Future  – We loved the food carts in Austin, TX and it turns out we’re not the only ones. Food trucks are fast becoming a US-wide trend and are out-stripping growth of regular restaurants. This trend is HOT and I predict it’ll keep going. Who doesn’t want access to innovative, inexpensive, gourmet food in a casual setting? Several cities now hold food truck festivals and food truck reviews, and they are proving serious competition to stix and brix restaurants.

The 'ol crack is still there

6/ Our “No Way I Can fix That” Windshield Crack is Holding – They say the story of the fish always gets longer in the retelling, and although our windshield story might have evolved creatively the crack, amazingly has not. It was 20″ when we got it and it’s still 20″, almost one year later. Kudos to Safelite and Montie from Wyoming. We still remember you.

7/ You Blog Readers are the Best - I’m a sentimental kinda gal, and although it’s a bit on the mushy side I have to say I love y’all for following the blog. You’re the reason I’m inspired to photograph and write each day and keep up with the posts.  Thanks to you we’ve surpassed 81,000 views and going strong. So, I thank you warmly for the support and invite each and every one of you for a chat and a drink anytime we’re close. Don’t be shy now!

That’s it folks. We’ll be wrapping up our time and heading back out into the boonies soon, but in the meantime rest assured we’ll be enjoying our stint in civilization to the fullest.

RV Solar Part III – The Installation

Marvelous Marvin

So, we come at last to the final installment of our story, and appropriately so on the last day of the year. It’s the last hurrah, the chocolate treat, the final ray of sunshine on the panels…you get the drift. Having decided on our equipment and specs we needed to make the very critical choice of whether to do it ourselves or get help. We’re relatively handy, but not exactly overly-confident and the idea of drilling a hole in our RV roof was enough to send me into a mild panic. So, for our personal sanity we decided help was needed and as it so happens AM Solar knew a good installer (himself a full-timer) who was travelling through Florida while we were here.

And that’s how we met Marvin.

Now, I’m not one to beat about the bush so I’ll just come right out and say it -> Marvin was marvelous. Not only is he a very nice and down-to-earth guy, but he knows solar and the final workmanship was beautiful. So, I’m very happy he came along and am equally happy to recommend him to others (his website and blog is here: http://precisionrvmobile.com/ and he’s travelling West from FL through TX and onto Yuma, where he’ll land sometime in March 2011).

Marvin spent around a day and a half doing the installation itself and a few extra hours chatting and going over questions with us.  Since we didn’t do the install ourselves, I won’t go into all the nitty gritty, but I’ll point out some key points that made the installation work:

• Careful Placement of the Panels:
  

  Marvin and Paul placing the solar panels on the roof

  The panels were placed on the roof so as to ensure there were *no* shadows from any of the existing structures up there (e.g. aircon, antennas). Also, they were placed so that they can be tilted with *no* shadows. Both these things are critical to make sure you get all the power you can out of those babies. Remember even a teeny amount of shadow can kill your power by huge amounts.

• Short, Efficient Wiring: 
  

  General Overview of our Installation. We were able to get nicely short wire runs.

  Marvin did a lovely job of running lines from panels to the combiner box at the back of our roof. From that point it was a direct shot through the roof, down along our our back closet and into the floor to our back left storage bin where he installed the solar controller. The short & direct wiring job was the very reason we were able to stay within our voltage drop goals. Remember that the longer the wire, the more your loss and minimizing loss is what it’s all about

• Controller Located Close to the Batteries:
  

  Marvin installs the solar controller in the bin right next to our battery bank.

  Our solar controller is in the bin directly adjacent to our batteries which is as close as you can get without being in the same room. This very close placement was what allowed us to meet less than 1% voltage drop between the charger and the batteries….another critical loss point. Marvin routed all the wires through the bin wall and sealed the hole to make sure the battery compartment was kept isolated.  

• Attention to Details: Marvin did a very nice job of routing wires carefully, sheathing everything, sealing holes, tying up loose ends and so forth. The final job was very clean and workmanship nicely done.

The final panel placement. The slight shadow on the left is mine and the ones in the back from the trees.

To finish off our install project, the day after Marvin was gone and for a few days after we diligently measured voltage loss across the system. So far, so good. Everything indicates that we’re meeting our goals of 2% voltage drop from our panels to our controller and 1% drop from controller to batteries. 

Did we do everything perfectly? Probably not. Does our system rock? We certainly think so! We’ve been in partially shaded sites (for part of the day) so we haven’t pushed the system to it’s max yet or run the full amperage through the wires so there’s always room for more measurement and improvements. That’ll be a project for 2011 and we’ll let you know how it goes.

In the meantime I wish everyone a Happy New Year and a fulfilling and joyfull start to 2011. See ya’ all next year!

RV Solar Part I – The Discovery Process

Harnessing the sun is a beautiful thing

It’s a cold winter day here in S.FL we’re generating power from the sun. As a self-confessed geek I find this outstandingly cool and for the past 5 days we’ve been glued like little kids in front of the solar charger display, oohing and aahing over the power coming in. We’re now ready to hit the road and live “off the grid” in the best of ways, but it took us a fair few months to get to this point. So, these next few days I’m going to take you aspiring solar RVers on our journey so that you too may one day enjoy the fruits of the sun. We’ll start with the discovery process, then the equipment and end in grand style with the installation. So, here we go…..

Why Go Solar?
First things first, solar (for most people) is not exactly a cost-saver. Everyone likes to think it is, but given the price tag (anywhere from $1500 to $6000, depending on number of panels, equipment and installation) the return can take a good few years to make sense financially. If you use mainly private campgrounds or just do the rare day of dry-camping, the good ‘ol generator will do just fine. If, however, you like to go “off the beaten track” on a regular basis solar can be a definite bonus. We like a lot of spots that don’t offer electricity, and we love the idea of being self-sufficient and not having to run the generator. And, of course…it’s just so very cool….

How Many Panels Do I Need?
The first question most people start with, is how many panels do I need? Panels are expensive and you can’t expect to generate enough solar power cover everything (e.g. aircon’s are too big a power draw for regular solar use). The best way to estimate how many to get is to calculate your average usage (in amp hours) versus the average power you can expect to get from your panels (in amp hours). A very approximate rule of thumb is to target ~1oo Watts of solar for every 100 amp hours of battery capacity, but it’s best to do an individual assesment. Most RVers want to be able to use their computers, lights, appliances and maybe TV/satellite, but individual needs vary (by alot). Also, panels are usually rated for sun hitting directly on the panel at 25˚C, so actual power output will almost always be lower than their “optimum” rating. .  I won’t go through the individual calculations, but I’ll let you know (later) what we decided to do and I can direct you to Jack Mayer’s page for good examples on how to calculate your own needs.

The Basics of Solar = Minimizing Loss
Solar is basically about trying to convert sun power into real power. All this sounds good and dandy, but very basic problem with this whole idea is that it’s an inefficient process….in fact a really inefficient process….and everything you do along the way (adding wires, routing through machines etc.) causes you to lose some of the original power you generated. Just to give you an example, solar panels themselves are only about 15% efficient (so, of the power coming in from the sun, only ~15% gets converted, even less if the sun isn’t directly on the panels or it gets too hot or bits of shade are present etc. etc.). Then you add a wire onto that panel and you lose a bit more (wires have resistance and the longer and thinner the wire the more resistance it has == more power loss). Then you put that wire into a charger (== more loss) , then more wires, then finally into your battery. So, every step of the way you’re losing power, kind of like trying to put water through a hose with a bunch of holes in it. It’s a fact of life with solar so in order to do it right you’ve got to do everything you can to **minimize** loss. If you start off by understanding that basic concept you’ll save yourself a lot of tears and head-banging later on.

So, How Do I Minimize Loss?
Once you start reading up about solar you’ll find a lot of info (much of it conflicting) on how to do it. I’m not going to go through all the details, but what I am going to do is give you a few key basics and route you to a couple of sites that will teach you the rest. Here’s the top tips we gleamed from all our research:

1. Buy Good Quality Panels & Go Higher Voltage if You Can - You want quality panels that have a long-term warranty, and if you can go with a higher voltage. The reason is to minimize loss. You can run 24V two times longer than 12V on the same wire for the same loss. It’s the very reason industrial power-lines run at such high voltages (often 110kV or above) = higher voltage means less loss over distance.
2. Beware of Shade - You might not think you need to worry about a little bit of shade on your panels. After all, the rest of it is getting sun, right? As it turns out even a teeny bit of shade can cut power output by huge amounts, and putting one square of your panel in shade can sometimes lock out power altogether. So, beware of any shade from roof elements (aircon, antennas etc.) when you install.
3. Use Thick Wires - One of the most important decisions you can make in your solar installation is using the right size wires. Wires are the pipes that route whatever power you get from your panels to your batteries. They’re often the single biggest loss point in any solar system and they’re often the single biggest mistake people make. Thicker wires will carry more power for longer distance with less loss, while thin wires can cause you to lose so much voltage that your batteries never get fully charged. The “standard” size wire (usually #10) that you get with a 12V solar system will typically be too small. You want to minimize loss to 2% or ideally 1% which means thicker wires (e.g. #6 or #4), especially for the parts of your system carrying the largest current. Higher voltage panels give you extra leeway, but you still need to think about proper size. Use tables or calculators or graphs to help calculate what size wire you need.
4. Get a Good Controller - The controller’s job is to convert whatever power you’re getting from your panels to usable power for your batteries. Typical deep-cycle RV batteries have 3-stage charging profiles, and they are sensitive to temperature. So, you want a controller that allows adjustable multi-stage, temperature-controlled charging. If you’re using higher-voltage panels you will also need a controller that can handle the higher incoming voltage.
5. Locate the Controller Close to the Batteries - The further your charger is away from your batteries, the more voltage you loose. You want it as close as possible (but not in the same bin) as your batteries.
6. Use the Right Charging Profile for your Batteries - When setting your controller, look at the battery manufacturer’s specs to determine the right charging profile for your batteries. Many flooded cell batteries require a higher charging voltage (typically 14.8V) than what the controller manufacturer recommends (often 14.4V). Go with the battery specs.
7. Consider AGM Batteries - If you can afford the switch AGM batteries have a much lower internal resistence than flooded cell batteries which means less loss getting power into the cells and a much faster charge time.

Those are the big basics. There is a lot more, as well as details pertaining to mounts, wire connections and such, but for those I’ll direct you to the experts:

• Jack Mayers Site – Lots of good, detailed info here on Solar including using higher-voltage panels.
• Handybob’s Site - He’s very opinionated (no doubt), but there’s lots of good info hiding here. Take time to look through the text and pictures.
• AltE Site - This is a commercial site, but they have plenty of detailed articles written in plain English explaining how solar power works.
• AM Solar – Another commercial site with some easy education articles.

Next, we’ll reveal our choice in equipment….stay tuned….