Tag Archives: solar energy

Cheap Green RV Living Resource

Good Morning!

I have been a big fan of the website cheaprvliving.com for a long time now. It is full of really useful information from Vandwellers and Fulltimers who have been living the alternative, mobile lifestyle for a long time, in everything from minivans to school buses. I really appreciate the no-frills attitude of the site and the vans/RVs/camper conversions that they feature. They have simple ideas about simple living.

I just recently discovered that cheaprvliving.com launched a sister site, called Cheap GREEN RV Living, and it’s all about how to live more sustainably in a camper, bus, converted van, or car. There are lots of ideas for off-grid alternative energy systems, boondocking tips and tricks, and how to respect the planet while living more freely. Some of the articles on CheapGreenRVLiving.com talk about how to pare down your possessions, some talk about the logistics of using the toilet, and others give detailed step by step instructions for installing a PV system on your van’s roof. My favorite page is the product reviews page. This guy is super honest and has actually used all of the products he reviews, so I found this article really useful.

Anyway, check out both sites if you haven’t already, you won’t be disappointed!

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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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