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Post in 'The Green Room' started by BrotherBart, Aug 9, 2010.
He's a good writer. I couldn't put the book down.
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I want to go just far enough off the grid to not have to pay any utilities. I have no illusion's that I will be self sustaining,
I like what this guy has done. Its grid tie only, but I think there are inverters that let you grid tie and have battery if you ever want to cut the cord completely or for emergencies.
I was able to take a tour of his house last week. He has brought a lot of technologies together. The result is that his heating demand is low enough that a good portion is done through solar. What the solar can't do he makes up with a geothermal heat-pump. The ultimate is that he makes enough electricity to run the heat pump and everything else.
Our home will be grid-tied in a couple weeks. We'll not be independent, but putting money in the bank during our long photo-period summers.
I considered battery backup, but it's expensive, maintenance intensive and the batteries have a very finite lifespan of 5-7 years. However, if building from scratch, you can do a lot to reduce heating, lighting and water loads by designing wisely and choosing appliances and systems carefully.
Xantrex has just come out with a high voltage charge controller, I havent seen any details but it may be the answer to grid tie folks who eventually want to switch to battery backup. Most standalone systesm are usually 24 to 48 volts which means large diameter wiring and switchgear rated for high amps. Due to the costs of wire and the voltage drop through the wires, the location of the panels is usually close to the battery bank so pole mouted arrays arent used as often. Grid Tie systems usually use higher voltage strings in the 300 to 400 volt range, the wires and swtiches are a lot smaller and the voltage drop though the lines is a lot lower so panels can be mounted remotely which potentially allows a better site for the panels. Previously, once a system was wired for grid tie, it would be an expensive proposition to rewire for standalone unless the system was designed for this to begin with.
I suspect that there would be a demand for a system with a small battery bank that could be switched from Gird tie to standalone in an emergency. Outback make a commercial system but it is limited to 48 volts which still requires big wires and most likely would require reworking a system that was designed as a grid tie only system. The trade off with a high voltage battery bank is that all the batteries are in series, so if one goes out the whole string may be useless.
A bucket of water (1-3 gallons) dumped into the toilet bowl will flush a toilet just fine. No need to pipe water to a 2nd floor, etc. We live close to a lake, have a gravity feed septic system, and in an emergency can get all the water needed for toilets from the lake. Also a a generator that powers the well pump, with a large pressure tank, for potable water needs, and wood stove which is 24/7 during heating season to heat the house. We also maintain ordinarily a good stock of canned and dried foods. Not "off the grid," but during a pretty long emergency we will be OK. The big issue is long term food supply.
I have a hard time imagining the advantages of a grid-tied system unless you're in a predominantly sunny part of the country where you might have the chance of a payback (or the State and Federal incentives offer a bulk of the expense in rebates.) On average, electric rates in the USA are relatively inexpensive, and with the use of energy efficient appliances, lighting, and generally the same low-consumptive approach you would take in an off-grid system use and expense would be low. Compare that to the initial expense of the grid-tied system and replacement expense over the life of the system, and unless you're really pumping juice back into the grid at a decent payback rate which would reduce the monthly rate you'll continue to pay for electric use (and "other fees") it seems like your expense would be high in the long run.
I'm sure that factors like proximity to the grid and local buy back rates and policies would make a difference. We would have paid more to run a grid line in here than to set up our system, and the buy back rates are pretty low (so is the amount of sunny days!) But we've spent 19k on our system and that seems like a healthy amount to invest for monthly electric bills. That amount is also initial expense and doesn't project what we may spend in replacing an inverter, charge controller, or panels.
In some places you can bank energy in the grid on sunny days and draw out later like a battery system, and only use actual batteries for backup situations. That reduces battery cost, space, etc.
Is that an equal exchange? Whatever you put into the grid you can effectively draw out with no expense other than your line fees etc.?
I've been reading up a bit on solar - both from a grid-tied and as a backup solution. There is a forum full of folks as 'dedicated' to the craft as the folks here are to burning wood.
What I've picked up there is that trying to build a grid-tie system with backup batteries makes about as much sense as keeping a stand of oak trees growing near your house to burn in an emergency in case you run out of wood next winter. Basically it comes down to economics. YES you CAN do it, but the cost of the batteries and maintenance on them is so high that you are far better simply getting a small generator to supply power for the few times you need it.
IF you do not have a power grid available, then you have to store your solar power and it may be justified to do the whole battery storage routine. In this case you will need to seriously manage/minimize your power budget or have a lot of money available to spend. Your cost/KWh over the life of the system will end up being on the order of 50c or more though which is higher than grid costs - but may be far better than hauling in fuel for a generator in a remote location not served by utilities.
However if you can do grid-tie, then it is best to treat the grid as your "cheap battery" and push surplus power there when you don't need it, draw it back when you need it. You avoid all sorts of losses and costs this way.
Another way to think of it is this: Would you consider buying/building a whole house battery backup system now that fed off the grid to charge? If not, then why would you consider building one that charges off the solar array?
depends on where you are. the one I heard about- you could bank it up at 1:1 for some # of months. If unused after that they buy it at some rate (probably not what they sell at). This would be a great deal. The line fees etc are still the killah.
I'm not very up on solar power systems yet.
My understanding is that for a grid tie system it won't work at all when the power goes out even though the sun is shining. For the battery/grid tie system if you had a very small battery bank could you at least use the sun during the day? That way you would only have to use the generator at night.
I agree that using the grid as your battery makes more sense and is more efficient, I just like having options
I have to say that the whole issue of battery back-up is a lot less foreboding than one might think. If the house is set up to be very efficient (which really should be a large part of any discussion regarding solar, wind or water power and any level of energy independence) the demand on the batteries is greatly reduced, and if sized properly the bank will meet needs and last many years. We're in Upstate NY where a solar array in the front yard can sometimes seem ridiculously optimistic, yet we run the whole house off the system easily relying much on the batteries. Our batteries are over six years in use and show little or no sign of reduction in their capabilities. Every 60 days I take about 20 minutes to water them and, quite importantly, we never let them get below a 60% charge. I suspect that many of the horror stories regarding batteries come from the same folks that never change the oil in their cars. I've heard plenty of stories of folks letting their batteries go nearly dry which pretty much means a complete bank replacement or an extremely small storage capacity. My installer at the time of my installation had been using the same battery bank for over 20 years.
That said, it would be hard not to tie to the grid if I could get a line in here for the cost of a battery bank and be able to take out what I put in for a reasonable fee. I don't NY is there yet.
That would be a great deal -hard to not take. If the line fees add up to the lifetime of a battery bank I'd maybe jump at it. One of the benefits of the bank though is that while we're in an area of frequent power outages, we've never had one in our 6+ years on the bank. A small advantage, but one you can appreciate when your neighbors are without electricity and you're humming along.
That goes for any form of heating.
You need a smaller area of woodland to heat an energy efficient house than one with loads of heat leaking out.
The time you save processing wood is time you can use growing your own fruit and veg, which helps the food area if you are going off grid in all possible directions.
It used to be reckoned here that an acre of land would be enough to feed a family of four for a year.
Personally, I'm a bit sceptical about it as a couple of years ago I did an experiment whereby I grew a square yard of wheat and was barely able to make a loaf of bread in the Autumn.
I went back on the grid for bread after that ;-)
We might be able to make it based on that formula if we could eat snow! Got to hone my farming skills.
That is correct. We have some very sunny late summers and fall. It also depends on the structure of the incentives. Our electricity costs 10-11 cents/kwh. For our WA state made system we will be getting 54 cents/kwh + 10 cents/kwh net metering for a total of 64 cents/kwh. There are some other incentives including no sales tax + 30% fed tax credit. Bottom line shows we should come in at roughly 8%/yr ROI which has the system paying for itself in 11 yrs. That is better than any guaranteed investment we could find. And the value of our property has increased with panels that should be doing quite well for several decades.