Solar for dummies

[cody]

The more I think about solar for the bus for Q the more corn fused I get, thinking about that brings up the question of why can't I do the same to help offset the power use at the anti-KOA, there i could set up a couple of wind turbines and some solar to help feed juice to batteries that would use an inverter to feed the breaker box.  So far I think I understand all that, my next question is the REA, (local electric supplier) is required to buy any excess power you produce and that would probably happen during unoccupied times, how can a person regulate that power being backfed into the system and how to backfeed it safely so linemen during power outages don't get fried.  Also, how is that power calculated, when they talk about 400 watts I realize that is the amount the panel could produce under ideal curcumstances, so how does a person calculate that over a 24 hour period or a 30 day period, the idea of the power company buying excess power is easy to understand, the meter runs backwards lol and at the end of the month if the meter has run forward more than it moved forward then I owe, if the meter is lower than it was, they owe lol. When a panel is rated at 400 watts is that 400 watts per hour or what? If I'm asking dumb questions, please don't tell me I'm dumb cause I think I'm kinda a smart guy, maybe I'm too dumb to know how smart I'm not lol, expiring minds want to know.

[belfert]

Enough solar or wind to supply power for the average house is going to be five digits easily unless you are a master at finding cheap used stuff.  A grid tie inverter presumably monitors the incoming utility power and cuts off power to the utility if there is no incoming power.  I am certain they have it figured out.  People who are really serious about solar either spend a ton of money or they use very little electricity by conserving and converting as much as possible to run on DC power direct from the panels.

Your electric utility may buy electricity from you at full retail today, but that will change as more and more people sell them power.  They don't buy power from a coal or nuclear plant at full retail so why would they pay you full retail?

I'm looking at geothermal as the way to save on energy.  If I can ever sell this house my next one will have geothermal.  I spend more on natural gas than on electricity.

[cody]

By statute the power companies in michigan are required to buy the excess electricity, at what rate I don't know, I would assume they pay wholesale for it.  I don't figure to completely replace the commercial power with solar or wind, only to suppliment it, the rates charged by REA are at a horrendous rate, it wasn't uncommon to see a bill of 100 to 150 a month when we wern't even there.  I have a dusk to dawn light thats the old mercury vapor type and rated at 180 watts, that light would burn all night and go off in the morning, with just that and the refrigerator plugged in, my bill would be in excess of 100 a month, REA doesn't generate any power, they buy and resell all the power they distribute and they do know how to turn a profit lol, I've been looking at everything from the small 400 watt 12 volt wind turbines to the larger ones that sell for 4K, I'm also trying to find the old crank up style tv towers that looked like a truss and went up 30 feet or so to plant the wind turbines on.  The Skanee house is already oriented to the south for maximum exposure to the winter sun so thats a big help, I've had solar heat panels on it back in the 80's but over time they wern't maintained and failed.  I know solar and wind will work up here because a lot of the remote hunting camps that are too far off the grid use it now.  My intention is to suppliment the existing system not to replace it, replacing it would be a killer money wise, things like the 220 for the well would be tough.  One thing I would imagine I would have to get is a cut off device that would sence the electricity being down and would kill the backfeed automatically to make it safe for linemen working on the lines in the event of a power outage.

[TomC]

With mobile use, the simplest is to have solar panels on the roof running through a voltage regulator charging your batteries.  Then just run your 120vac needs through the inverter.  I don't believe campgrounds are setup to be feeding electricity back into the system-that's just plainly getting to complicated. Most campgrounds frown on mechanical wind generators because of their noise and eye sore factor.
Whatever system you use on the bus keep it simple!  I don't have anything automatic.  That keeps me in control, and assures that (for instance) an automatic transfer switch won't hang me up if I'm dry camping.  Good Luck, TomC

[NewbeeMC9]

Cody,

The trace 4024 can handle grid tie and selling back for you, you do have to be set up with the power company to do that.  I'm not sure about the newer ones.    HTH


400 watts for one hour would be   400 watt-hrs or .4 kw-hrs      around here 1 kw-hr is 12 or 13 cents

at .4 kw-hr it would take 2.5 hrs to make 12 cents.         roughly speaking

[cody]

Tom, I'm talking about stationary use at one of my houses, the house is on 13 acres and I'm trying to offset the electrical costs there, I'm also setting up several rv sites for friends that come over on the property, the goal of the sites is to provide a spot for friends, I call it the anti-KOA cause if there is a rule the KOA feels is mandatory, I'm going to have a rule against the rule lol. I'm more interested in offsetting the electrical usage as much as possible to bring the cost down, the cost from REA is .47 now, 12 cents would be a giveaway price up here. 

[mikelutestanski]

Hello:    Most states allow the power company to set the rates for buybacks and they will not let the meter run backwards. They will furnish another meter in the same line and you  might be paid the wholesale rate less a discount for the amount that you send back. in other words because you are a very small power company your power is worth less.   Go figure.
    Anyway I did some searching and you can do the same to find out what your state will allow the power company to do . 
    Part of your success will depend on the public utilities commission and how well the power companies have smoozed with its members.
      The sad part of it all is that companies are people now albeit giant people and they have the right to gouge you as much as possible  .   The AMerican way..
      I do not know what is the best way for you in your situation.  Here in florida  the sun is usually offers the most bang for the buck but it has its drawbacks also.
    Regards and happy bussin    mike

[cody]

MIke, I've already printed the regs out as far as the state goes and as usual, they are clear as mud,  I've talked to the power company and they hung up on me, each time I call the lady says the private generation of electricity is illegal and if I continue to attempt to do it, they will see to it that I am procuted and sent to prison so information from the power company hasn't been all that helpful lol.

[Lin]

Cody,

$.47 per kwh is very expensive.  Are you sure about that?  Here, there is a tiered system.  The first 900 kwh are .12.  The next tier is .14 and so on up to tier 5, which is .30.  At .47, a large home solar or wind system would probably be cost effective.  I used about 35 kwh per day in December.  At .47/kwh, home production would save over $500/month!  A 10kwh wind system would cost me about $35,000 here after state rebates.  At .47/kwh, it would give me another pension.

If you need more information for your state, speak to those that sell/install the equipement.  Their figures will be on the rosy side, but they can be gushers of information.

[Sean]

... I'm talking about stationary use at one of my houses, the house is on 13 acres and I'm trying to offset the electrical costs there, ... I'm more interested in offsetting the electrical usage as much as possible to bring the cost down, the cost from REA is .47 now, 12 cents would be a giveaway price up here.

The general rule of thumb is that it takes about 20-25 years to pay back a solar electric system in the southern US, and this number increases the further north you go (incident solar radiation decreases dramatically above 40° or so north latitude).

That "rule of thumb" is based on an average cost per kWh of electricity in the US of about $0.12, give or take.  If your electricity is significantly more costly than that, your payback may be sooner.

Most fixed solar installations rely on the grid to be the buffer, rather than battery banks.  Most serious solar grid-tie inverters today don't even have a provision for battery connection; they tie directly to the photovoltaic panels.  When the grid goes down, your power is out, even if it's sunny, because the inverters shut down when the grid does (long story).

The Xantrex (Trace) SW series is an example of a grid-tie inverter that does use a battery bank and can tide you over through outages.  However, this adds significantly to the cost of the system; you don't figure payback on this part of the system in terms of energy dollars saved, but rather in the costs saved by avoiding commercial outages.  Costs of these systems on a whole-house basis are well into six figures, and annual maintenance goes up dramatically over battery-less systems.

All of the above pay-back discussion assumes grid-tie and selling excess power to the utility at retail rates, something that many states mandate by law for residential (but not commercial) accounts.  If the utility does not buy power, or you don't invest in a grid-tie system, payback on a solar system will be much longer, because you must store every watt you don't use, and you must buy at retail any watts you need when your system is maxed out.

Lastly, "off-grid" systems are never more cost-effective than buying power from the grid when a grid connection already exists.  These systems become cost-effective in remote locations where the customer would have to pay the utility to run power over a long distance or harsh terrain to reach the structure; usually, this is several miles.

I'm not telling you not to do this; just that you should understand you'll need to be ready to invest dozens (or hundreds) of thousands of dollars into a system that will not pay itself off for two or more decades.  You either need to really want to be a long-term investor in this sort of technology, or have a burning desire to save the planet even though it will cost you up front.

-Sean
http://OurOdyssey.BlogSpot.com

[belfert]

I'm not up on every power company, but I have heard a lot will pay retail for generated power.  Some are forced to do so by state regulators.  It is widely believed the practice of being paid retail rates for power will end as more people sell power to the utilities.

I find it hard to believe that one could not generate their own power legally.  It would seem to almost be cheaper to have your own generator than to pay 47 cents a KW.  Fuel only to run a 16 KW generator I figure around 20 cents a KW or less.  A private high school locally has their own power plant even though they could easily just buy power.  20 years ago they didn't even have a connection to the grid at all.  No backup if their power plant went down.

[cody]

I made the mistake of having the power shut off because we wern't going to use the house for a period of time, now, becuase I asked about solar they are requiring me to post a 5 million dollar bond with them to protect their lineman before I can get the power restored, just having a generator on grounds, which I do, is reason enough for them to require the bond.  I know of at least 4 camps that are powered by solar or wind with generators as back up, they are not using  a lot of panels but are enough to do what they want and nobody I know of is paying the hundreds of thousands of dollars to do it.  I just can't believe that I can't run a few light bulbs and a tv and refrigerator off a cheaper system, I'm looking into the legality of them requiring the bond and haven't gotten any legal opinion on it yet but the electric company is playing hard ball, being the only source of power in this area it's hard to go against them if they make a decree, so far I've found out that they are not regulated by the state power commission because they are privately owned and they own everything themselves, including the wires and light poles.  If they were a public utility it would be different.

[Sean]

Sorry, missed answering these:

... how can a person regulate that power being backfed into the system and how to backfeed it safely so linemen during power outages don't get fried.

The phenomenon you are describing is known as "islanding" and the law requires all grid-tie alternative energy systems to incorporate an "anti-islanding" feature.  IOTW, this feature will be built-in to the inverter you use.  Such inverters are known in industry parlance as "Non-islanding utility-interactive inverters" and common examples are Sunny Boy and Xantrex.  The Xantrex/Trace SW4024 that I use in my bus is a Non-islanding Utility Interactive model and I could set it to send power back into the grid, except that it would be illegal for me to do so.  All such installations must be inspected and approved by the utility and sometimes state regulators as well.

 Also, how is that power calculated, when they talk about 400 watts I realize that is the amount the panel could produce under ideal circumstances, so how does a person calculate that over a 24 hour period or a 30 day period

The "ratings" you see on solar panels are maximum output in bright sunlight at right-angles to the incident rays and at about 40° latitude.  In real life, photovoltaic panels never put out this amount of power.

There are rules of thumb for calculating output over time, however you are best advised to use tables specific to your region (which account for incident sunlight and number of sunny days per year).

An upper limit is generally to assume the average output of a panel is half the nameplate rating for eight hours on a sunny day.  So a 400-watt panel properly mounted and angled would give you an average of 1600 watt-hours or 1.6 kWh (200 watts times eight hours) for every sunny day you have.  If your region has, say, 240 sunny days per year, that's an average of 20 each month, for an average of 32 kWh a month for that 400-watt panel.  At your claimed electric rate, that panel would save you an average of $15 per month on your electric bill.  Since a typical price for such a panel would be around $3,000, it would take nearly 17 years just to pay back the panel alone, not counting all the other costs such as inverters, mounting hardware, maintenance, cables, etc. etc..  Also note that 15-20 years is the average life of a photovoltaic panel (and their output decreases steadily over that time), so you'd be replacing this panel just a year or two after it paid itself off.  And remember, I said upper limit -- in your far-north location, the numbers are probably worse.

FWIW, whole-house systems require ten times that number of panels.

-Sean
http://OurOdyssey.BlogSpot.com

[Sean]

I find it hard to believe that one could not generate their own power legally.

Generating your own power with photovoltaic panels is legal everywhere (although some building codes may require the panels to be hidden from view).

There's a difference, though, between generating it and selling it back to the utility.  Backfeeding the grid is definitely not permitted everywhere; this varies widely by state and PUC.  Many states encourage it, but it is by no means universal.

Utility-interactive inverters such as the Trace SW series can always be used to offset utility power on the consumption side.  You just can't enable the sell-back feature without approval from the utility.

-Sean
http://OurOdyssey.BlogSpot.com

[Sean]

...  I just can't believe that I can't run a few light bulbs and a tv and refrigerator off a cheaper system ...

You can.  But it will still take decades to pay back.  You are much better off reducing your bill by changing your consumption.  Replacing incandescents with fluorescents, or fluorescents with LEDs, will have a much more immediate payback (years instead of decades).  Same goes for replacing CRTs with LCDs, resistive heaters with heat pumps, single-pane windows with thermal glass, etc. etc.

Again, if you are not already connected to the grid, such as those hunting camps you mentioned, the economics change dramatically.

-Sean
http://OurOdyssey.BlogSpot.com
(with apologies to everyone for four separate posts in a row)