Monday, August 22, 2011

Ask Matt

Welcome to our new semi-regular feature called Ask Matt! From time to time, faithful readers will pose a question on the blog that I as your humble narrator cannot answer. Matt, who has full permissions to post here on the blog tends to defer the writing to me, but I have asked him to answer some of the questions that have asked in comments.  


Our first question comes from fellow Tiny House blogger and enthusiast Andrew Odom
“I am anxious to hear what you do with the solar. What are you setting up? What is the budget? What will it run? Do tell, do tell.”
And Matt says:

We designed the solar for our cabin by first minimizing our needs - energy hogs like electric stoves, fridges, washer / dryer, air conditioning, water heaters, microwaves and such were ruled out. Our system provides lights, small fans, and plugs for small appliances. When we need to run construction tools or other items with large power needs, we use a portable generator. The generator can also recharge the batteries if we need it to.

When selecting the actual components, we took a two phase approach. The system we have now is phase 1. It is a small system consisting of a 60 watt solar array, a 7 amp charge controller, and a 2000 watt- modified sine wave inverter and (2) 60 Amp/hr batteries. I put that together for about $900. The inverter connects directly to the breaker box on our cabin and we use standard electrical fixtures and outlets. The weakness of this system is that the small solar array limits the amount of power we can generate and the small batteries limit the amount of power we can store. Since we are only at the cabin on weekends, this has not been a problem. The batteries are full when we get there and the system runs everything we need it to (lights, laptops, cell phones, battery chargers) for the weekend.


Next year we plan to spend more time in the cabin. When we outgrow the current system, we'll move to phase 2. To do that, we will upgrade the solar panels to (2) 240 watt mono crystalline solar panels, a 30 amp charge controller, and 3 115 Amp/hr batteries. Originally we had planned to upgrade the inverter to a pure sine wave inverter, but the modified sine wave inverter we currently use has worked perfectly, so there is no need to spend the extra money. Based on current prices, the upgrade will cost approximately $2200. The phase 2 system should provide enough power to meet our needs on an ongoing basis. In case it falls short due to long periods of cloudy weather or unexpectedly high usage, the generator will continue to provide backup power and charging capability.
Please, feel free to ask any questions about anything we are doing at any time and I promise to pass them on to Matt to answer and will publish the answers here. 

We'll be back up to the house this coming weekend to start some of the interior trim and finish work.

3 comments:

  1. Matt, is the generator gas or diesel? If diesel, can you convert it for use with waste oil (http://www.youtube.com/watch?v=CDu0lS5XMD0)

    If gas, how about methane or wood gas? (http://www.builditsolar.com/Projects/BioFuel/biofuels.htm#Methane)

    Also, as a third alternative, I've seen fresnel lenses used to heat a cast iron pipe, generating steam. Not sure if the pressure would be great enough to run any kind of decent generator motor. Of course there's always wind power, and there are a ton of videos on that...

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  2. Fresnel Lenses are great, but they have a very specific focal point and need to be perfectly perpendicular to the incoming rays. Using such a system for a steam generator would be interesting, but there are some significant technical issues in tracking and process to keep it running properly.

    While taken from a slightly different route, this is what experimental solar concentration tower generators are doing.

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  3. The generator is a Honda eu2000. We went with that because it is extremely quiet (we have great neighbors and although they are pretty far way we try to do everything we can not to bug them) and has a great built in inverter (just about the cleanest generator power I've seen on a portable unit). It can be retrofitted to use LP and / or natural gas...I'd bet it wouldn't be that big of a jump from there to methane or wood gas. We'll definitely be looking at alternative fuel options for both power generation and heating as we spend more time in the cabin. There are a lot of great approaches out there, and I'm looking forward to tinkering with a bunch of them.

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