Marcos Buenijo wrote:Very nice bus conversion.
I highly recommend you get access to grid power first (mainly because $1000 will not go far in purchasing an off grid solar system). After you have this available, then you may consider a solar system. This is particularly important since you will be running an a/c system. Even a small a/c unit will consume electricity at a high rate.
I suggest using the opportunity of living in the bus to take meticulous data on energy usage. This will require the use of meters to carefully measure the actual KWh consumption, along with measuring and recording the usage of individual appliances (especially a/c). With respect to using the a/c unit, I suggest emphasizing good insulation, adding a thermal mass of some form, and to operate the unit on a timer. The idea is to operate the a/c unit only during the day when a solar array is likely to be producing. When you finally get the solar system, then the practice of using a timer on the a/c will be a great deal more efficient at making use of the electricity provided, and it will be a lot less stressful on the battery system. I don't know much about cob construction, but perhaps this will provide a good thermal mass. You will require a fairly large array to support an a/c unit, but this will be good for the battery system when a/c is not required by ensuring a float charge takes place often and by minimizing discharge on the battery. Make sure to check out the thread "Efficient Air Conditioning" for a discussion of split ductless a/c systems and how they are so efficient. http://www.permies.com/t/27465//Efficient-Air-Conditioning . In your case, however, there is a good argument for sticking with a small window unit.
Jeremy Moore wrote:Thank you both for your help. Marcos, we did insulate the bus in multiple layers, floor, walls, ceiling, and we painted the roof with a reflective paint, but at the end of the day, it's still essentially a tin can with lots of windows. We have considered removing some of the windows, but it's really just another project on a list that is growing by the week. I am all for hooking off grid power myself, but my wife is another matter. The thing is, we made this move to live in a more self sufficient, sustainable matter, and thus far we both feel like we've done a lot more talking about beliefs we claim to possess but are, in fact, not practicing. I hate to put it in terms of principle, but at this point, it is a lot about principle and having to pull power off our folks' house (another red mark in the self-sustaining column). With this all in mind, we are extremely open to alternative ways of conducting ourselves, including air conditioning. I don't know for sure how we'd simply "do without" a/c. As I said, we're located in AL and it pretty much stays in the low to high 90's for nearly 4 months. It simply gets too hot in the bus to remain comfortable. I guess my next question should be, what is the realistic cost of an adequate off-grid system that would do what we need? I have done a good deal of research and the prices vary wildly. it seems like If I have a good resource, one can assemble a good system for a reasonable amount of money. IF so, where's a good source for cheap/good qualitiy components (if there is such a place)?
Brian Knight wrote:I have to question the desire to strive for off-grid solar installations. The reasons for being off-grid are obvious but I feel the need to remind or inform others of the two main reasons for staying grid-tied:
1. Grid tied is usually much more affordable. This goes for upfront costs and long term maintenance.
2. Its better for the environment and society. Battery production has some nasty consequences but its the contribution to the grid during peak demand hours that really helps the environment and society. A grid-tied PV system contributes clean energy to the surrounding neighbors which exponentially reduces the waste of electricity that is lost during grid transport and conversion. Peak demand production is the main driver for building new fossil fuel plants.
Off-grid makes the most sense in remote locations with no infrastructure. If the infrastructure is nearby then off-grid is turning its back on society and ignoring the convenience of the grid as a battery which should have less environmental (and monetary) consequences than using deep cycle batteries and fossil fuel generators for backup.
William Trachte wrote:The final deal-breaker is the batteries. Spending $8-10K on a battery bank that, even if you do everything right, will end up a biohazard somewhere in ten years, is not a value proposition we chose to entertain. And then you get to buy some more. I'm not sure I'd count on reports of 20 or 30 years of use: speaking to a rep from Trojan, we were assured that how they are kept and used greatly effects life. Being a Yankee, I can well believe that AC is not really optional thereabouts, and that kind of demand just might spell doom for a battery.
John Elliott wrote:Small fridge -- 1 KW-hr per day
Small freezer -- 1 KW-hr per day
Here is a page that can help you figure the size and cost on solar panels.
Tony Masterson wrote:Does it matter what type of voltage the freezer uses due convertor efficiency? 110v AC or say 12v DC.
What about gas powered freezers like this one: http://www.alibaba.com/product-gs/1393713880/Gas_power_chest_freezer.html
Not promoting it in any way but it runs on 12v, 110v, 220v and gas.
Is a natural gas freezer worth investigating or is it utterly inefficient?