Tag Archives: photovoltaic

Solar Module Placement

Hello again!

I just got some really great questions about the off-grid systems that the COMET will have, and I thought it would be a good time to share some of these infographics and design concepts I’ve been working on.

Where do you put three 185-watt solar modules on a 16 foot trailer with limited surface area?

Here are some of my ideas:

 

And how do you maximize solar collection when you are parked, and minimize drag when you are driving? See below:

 

 

I’ll post some of my rainwater collection system graphics later, which will explain how that whole thing works!

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All-DC Solar Power System in The COMET

Here’s a follow up to the last post, where I talked about how to calculate your (kilo)watt usage and shared my own table showing what electricity-using appliances I will have. Here’s why that “AC or DC” column is important.

These are the actual modules that I have. 3 x 185W modules. Thanks Cotuit Solar!

I want to design a PV system for The COMET that is DC-only, and has no AC inverter (which turns the DC power from the panels into the AC power that comes out of your wall sockets). The reason is because of the nature of inverters for PV systems: inverters are the single most expensive component of a PV system. They also are the point at which 20% of efficiency from what the panels are actually producing gets lost. That means it takes 20% of the energy you are producing with your panels to power the inverter. That’s a lot of lost energy, especially in a small system! So I am devising a unique system that requires no inverter.

Here is a diagram of how the system will look. Modules, charge controller, battery bank, then DC load or outlets.

In order to do this, I need to convert ALL of my electricity-using appliances to run on DC power (see previous post for details, but basically everything in The COMET runs on DC anyway, except the laptop computer, which I will buy an DC power adapter for ($20 as opposed to $2000 for an inverter). It isn’t unusual for camper and RV appliances to be wired for DC and use only DC, so that’s another reason this conversion will be feasible. I’ll also need to make sure everything is running at 12V – meaning I will need a 12 V battery system.

DC plug

I have seen some grid-tied systems that use this principle to power what DC appliances they have (check out this Instructable as an example). For example, charging all of your fans, lights, cell phones, ipods, and basically other electronics with car chargers, with power from the panels using no inverter (and maybe even no battery if you only want to access the free power during the day). However, my system will be very unique in that it is off-grid and completely DC. I’ll have wall outlets like everyone else – they’ll just be DC and look like the ones in your car!

Small 150W inverter for just-in-case AC scenarios.

The one thing I am worried about with this system is not having the flexibility to use anything with an AC plug. Who knows what will come up, there may be a day when I need to test something or use an AC plug to power something. Of course, I can only plan so much. For this scenario, I will have a small car inverter (probably somewhere around 300 W) that can plug into the DC wall outlets when I need it (or maybe it’s mounted in the wall somewhere, but I see it as being more of an emergency use kind of thing).

I’m still working out the kinks, but this entirely DC system will save me a lot of money and be much more efficient than an inverter system. I’ll keep you updated as I experiment with this concept!

 

Totally unrelated, but I just wanted to point out how awesome the Habitat for Humanity ReStore is. I went to the one in Worcester on Saturday, because I was driving by, and they happened to have a few click panels of cork flooring. I picked them up for a $1 and will hopefully be able to use them in the bathroom!

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Mobile Solar Electricity with PV

Hey everyone! Happy Monday!

So as you may know all last week I was in Vermont attending an intensive photovoltaic design/installation class (at the Yestermorrow Design/Buidl School – check it out here). By the end of the week, I realized it would be very difficult to sum up everything I learned, so I think I’ll just get into it little by little. There are so many factors and variables when designing a PV solar electric system for your (tiny) house or mobile house. Weight and stability came up a lot, as well as mobility concerns with roof mounted systems.

For today, I thought it would be fun to introduce you to some of the stuff we covered in the course with an activity you can do yourself. It’s really enlightening and will definitely surprise you if you’ve never really thought about how much energy you use.

For this it’s helpful to know that Volts x Amps = Watts. It’s also really helpful to have a Kill-A-Watt meter around, so that you can plug in your electronics and see how much power they use.

Here’s a Kill-A-Watt meter like the one I used.

Also, note that my calculations are in Watts, because I am dealing with mostly smaller electronics and appliances, but usually if you were sizing a whole house system or something larger you would use kilowatts.

*Efficiency first! Make sure you consider your efficiency before sizing a PV system. Consider phantom loads, insulation, and other factors to see how you could use less in the first place! For example, I am choosing not to have an electrical pump (my faucet will have a hand or foot pump which creates water pressure, and my solar shower will be gravity fed). Because I am going off-grid in a small space, I really have to be careful about where I use electricity.

Basically, we are calculating how many watt-hours we use in a day in order to be able to accurately size an off-grid solar PV system. Finding out how much energy you use in day is really cool, and I feel like it immediately makes you think more about what you use and when. I made a chart with the headings Appliance, Watts, Hours/Day, and wH/Day in order to break down my energy usage. From this I could figure out how much energy I use in a typical day. My chart is pretty simple, and I only have a couple of power-using appliances. The stove and heater in The COMET run on propane (PV cannot efficiently produce heat with electricity). Like I said, no electrical pumps for water. All of my lights will be LEDs to cut down on watts (which is generally an expensive endeavor – to replace all of your lights with LEDs – but I only have about 4 wall sockets so it’ll be affordable and worth it in the energy-usage long run!). Also, I overestimated in some cases just to be safe.

Here’s my chart!

So you can see that I only have a few electricity-using appliances. The other thing to consider here, especially for me because I spend a good amount of time on the road (and even more once the I live in The COMET camper) is that I often charge my phone and other things in the car. Anything with a USB port usually gets re-charged on the road.

I hope this is useful in helping you figure out how much energy you use. For some of your appliances, you will be able to see how many watts it uses on a spec sheet or by looking it up online. For others, it’s just easier to plug it into the Kill-A-Watt. And if you have the voltage and amperage of an appliance, you can figure out the watts by multiplying V x A. The total watt-hours/day ( that 790) will be integral to figuring out how much PV you need for an off-grid system. I will go into that later!

At this point, the DC column at the end of the chart may not make sense, but I will do another post later about why that column is so important! I am figuring out a way to have a much more efficient PV system than most, and I think you will find it interesting to think about! So stay tuned for that later on.

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Photovoltaic Installation at Yestermorrow School

The last 5 days I have been in a very intense class learning the ropes of PV installation. We’ve done sizing of a system (I haven’t done this much math since high school!), flash-mounted roof mounts, and we’ve wired up our solar panels. Based on my calculations, I think I have way more than enough PV power with the three panels I recently got from Cotuit Solar.

Tomorrow is the last day, when we finally plug the panels into the combiner box (then charge controller, then AC breaker, then batteries, then inverter – whew!) and see how it all fits together. This class has been super enlightening and I can’t wait to share what I’ve learned. The Yestermorrow Design/Build School offers a learning experience like no other. It is really amazing here. Every person I meet is either building a tiny house (or has built one) or is working on an Airstream retrofit/renovation or already lives in an Airstream. My kind of people!

Anyway, this is all I have to show you for now, more later!

And here’s the tiny house that’s currently in the parking lot outside!

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Yestermorrow Design/Build School – first workshop this week!

I realized that I hadn’t written a post about the Yestermorrow Design/Build School in Vermont, and that I should introduce you all to the place since I have my first class there this coming Sunday. Yestermorrow School is a design/build school that focuses on hands-on teaching and sustainable building practices. They offer workshops that range from 2 days to 4 weeks (and they have a sustainable building semester program with UMass Amherst). Topics range from Green building materials, woodworking, and tiny house building workshops, to architectural design and drawing courses and stained glass making workshops. I found out about them last year and when I read their “Philosophy” statement I was SO HAPPY to find a place that shared my values exactly. All last semester I had been talking about closing the gap between designers and builders, and wasn’t really getting any support in doing that. So I left my college for some time to attend Yestermorrow for the next year, through their Sustainable Design/Build Certificate program. Basically with the certificate program (and they offer certificates in other subjects too)  you choose a handful of week-long, 3-week long, and weekend workshops from a long list of amazing classes. I chose the certificate over the semester program because of the flexibility and that way I could work on The COMET at the same time. I’ve heard the workshops are really intense and totally awesome, and that a 3 week workshop feels like an entire semester. I’m about to find out!

Anyway, here’s their philosophy you you know what I mean:

“Yestermorrow’s courses are specifically designed to demystify the designing and building processes using hands-on, experiential learning to teach students the art and wisdom of good design and the skill and savvy of enduring craftsmanship as a single, integrated process.

This creative process offers students unique insight into the oftentimes disparate worlds of the architect and the builder. Architects are routinely trained without any building experience that might inform their designs, and builders are trained to execute without a sense of the overarching purpose or design of the project.

Combining design and building offers numerous advantages and promotes the creation of intentional and inspired buildings and communities that enhance our world. From the professional design/builder to the do-it-yourself design/build homeowner, every designer should know how to build and every builder should know how to design. This philosophy sets Yestermorrow apart from other educational institutions.”

There you have it. I was in love!

Anyway, this coming Sunday I go up to VT for my first workshop – a 5-day intensive called “Solar Electric Design and Installation”. Just in time, too, because I just bought 3 solar panels! I specifically chose workshops that would help me with the skills associated with designing/building/making the COMET. Once I take this workshop, I’ll be able to install my own photovoltaic system, and show you all how I did it step by step!

Also, if you haven’t seen it already, you should check out this video of the tiny house that the Semester program just built/finished. It is gorgeous!! (see it here: http://www.youtube.com/watch?v=j5mD3iwOb2w)

I encourage you to check out the Yestermorrow website and browse through their courses to get an idea of how awesome the place is. When you attend a class there, you can either stay in the main building, stay in a cabin, or just camp out. I’m really excited! Hopefully at some point I’ll be able to stay in the COMET when I’m up there!

 

Also, on the topic of workshops, I just signed up for the recently announced Tumbleweed Tiny House building workshop in Boston on May 19th and 20th, with Jay Schafer and fellow Massachusetts tiny house guy Deek Diedricksen. I’m really looking forward to it. Personally, I think the Tumbleweed houses are a little too traditional for my style (what can I say – I like recycling junk and using used materials!), but I’m looking forward to building one! Is anyone else planning on going to the Boston Tumbleweed workshop?

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