On-grid, not net-metered; how to control RE first, then grid when needed?

rickeolis

I'm running a 500 watt system right now, but want to go to a 3000w PV setup using PV\batteries while staying on the grid.
How can I design this to make use of 100% of my PV made energy primarily, and then when demand gets high (as in water heater coming on, etc.), that it will allow for the grid to feed me this as needed?
Net metering doesn't impress me right now.
I would think this would keep me from being able to use a Xantrex GT type of inverter, so I'm thinking an Outback grid style... :-)

Roderick

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Can you say a little more about what your goals are? Did you want to be able to run when the grid is down?

It will also help to clarify what it is that you don't like about net metering, then the forum can address that. It would seem that net metering only helps financially, but maybe I don't understand the details of your plans.

mike95490

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

rickeolis wrote:

I'm running a 500 watt system right now, but want to go to a 3000w PV setup using PV\batteries while staying on the grid.

Do you have an intertie agreement with your power company? If not, and they see something odd, like your meter going backwards, and not enough profit, they will disconnect you. Just a heads up.

rickeolis

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

  I do eventually want to go off-grid, but not for a while. I have a type of meter that will not go backwards, but I know at some point the utility is going to ask why I'm not using much of theirs.
I want to build a system that I can add to as time goes by so I think the first step is getting an inverter/controller system that will work from my current 500 watts until I get up to my desired 3000. Then as time goes by I can keep adding more panels (probably 167w Sharps). I already am working on getting several more of the Trojan T-105's that I'm using now too.
My beef with net-metering is that here I only get a credit, and I would rather put the extra watts into my own system rather than let this company profit from me.
Yes, it would be nice to stay on during an outage, but what I'm doing right now works just as well with two complete separate systems, one being the old grid system and now my new one which at the moment only really covers the lights in the house, but I have seen a smaller electric bill from it!
Also when you decide to do net-metering, you can run into huge costs getting inspected and cleared as well as signing agreements and all, (F-that.)
The only reason I don't want to get off of the utility is for any unseen future needs.
Anyway, I guess the best way to start is to know what to buy ahead of time, so this is why I’m writing-

-Rick-

crewzer

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Rick,

You might want to consider OutBack Power’s “off-grid” FX inverters and their Mate controller. All FX inverters require batteries to operate; you just have to decide what size bank will suit your particular needs. The off-grid (or back-up) inverters can’t feed the grid, but they can be connected to the grid or a generator to allow AC pass-through and/or charge your batteries.

The Mate enables some features you may find especially interesting. One is “HBX Mode”, which allows the inverter to run off the batteries until it reaches a low battery voltage set point. It then switches the loads to an AC power source (i.e., the grid) and can also charge the batteries until they reach a set high voltage point. This feature can be used in conjunction with other battery charging sources such as solar.

Another feature is called “Grid-Use Mode”. This in intended for synchronizing inverter use to your utility’s time-of-use (TOU) schedule, and it allows you to use cheap power during low TOU rates and run from batteries during high TOU rates.

The inverters can be also be stacked to add more power to a single 120 V line or to create a 120/240 VAC configuration.

Info on the inverters and the Mate is available over on Outback’s website: www.outbackpower.com

HTH,
Jim / crewzer

Roderick

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

I'm not sure where you're located, but if the local utility has one sell rate and one buy rate, then I understand.  On the other hand, if you're in a place like California, the sell and buy rates are identical, so there's no harm in going to net metering from that standpoint.  If you generate less than your house uses, the energy goes into your house, anyway, and if you generate more, it goes into the utility.  If you maintain two separate systems, I'm not sure where excess energy would go - batteries, if not fully charged, but otherwise, it would be wasted.

Again, I can't speak for your location, but the permit for me to do things all legal was about $200, and the interconnect agreement was free (okay, there was postage involved for mailing, etc.).  I hate to spend $200 as much as the next guy, but that was very small in comparision to 3000 watts of panels, which ran $13-14,000 before rebates, if memory serves.  As for the inspection stuff, I failed the first time, spent $65 to fix it, then passed.  No extra inspection charge.  It probably varies by jurisdiction.

Finally, to get some rebates, I needed inspector sign-off, so that might be a consideration.  The rebates were well worth the trouble, paying for about 40% of the project cost.

The Outback system with both battery and grid-tie struck me as a poor value, but I suppose it depends on individual needs.

rickeolis

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Hey, thanks Crewzer! This is what I wanted. I have been on the Outback website many times, but haven't looked at the 'Mate' specs much.
I do use our utility's TOU configuration, and the off-peak rate is actually quite cheap, so we've been working on trying not to use heavy amperage items during the on-peak. This sounds like the one to go with, I'll check into it.
Thanks again-

-Rick-

Roderick-When I first got into PV, I thought I wanted to do net-metering, until I actually visited a local full system dealer. After finding out about the lame state ($only when bought as a whole system at a pre-approved vendor $$$) and fed ($2000.00 total ever) rebates when buying $32,000.00 worth of their products and another $10,000 in labor just to save $90.00 per month on my electric, I decided to do the whole on my own a little at a time.
I did get a fancy copy of the contract that my local utility sent me as well- about what they require for me to go net-metered, that only reassured my desire to go it alone!
Additionally, if the utlity buys back only at wholesale prices but they sell at retail, THEY profit off of my production, and they will NEVER give me a check for money. No thanks...
Thanks though for the feedback!

crewzer

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

8-)

Frank

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Our Xantrex SW4024 was used to power a bunch of stuff. It has a LBX mode (low-battery-transfer) where you can program a cutoff voltage, after which it will switch to the grid and recharge the batteries. (Sound familiar? Outback guys started at Trace!) FWIW we're now grid-tied: it saves battery cycles and the batteries are always full for those time (like the last 3 days) when we lost power due to high winds.

BB.

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

You really need to figure out the Grid Tied Net Metering with your utility (still don't know where you live)... Like Roderick says, in California the advantage is pretty much all to the customer.

I pay a minimum of about $5.50 per month (includes a few tens of kWatts of minimum charge), and the rest goes into the bank for a 1 year cycle. The state and utility really don't want you to put more solar PV in than you will use--so they want the balance near zero.

For me, I put in more so that when electric Hybrids or decent around town electric cars are available (for reasonable prices) or some spot air-conditioning for those few weeks a year of hot weather around here, I will already have the extra capacity installed (I had about $250 of credit last year)...

If you are really trying to save money, go with solar hot water/space heating first. The return on investment is really much better (although, there is probably a lot more maintenance required).

I even looked into a grid tie / battery backed system--and for the little bit my power is out, it was just cheaper all the way around to buy a Honda eu2000i generator and store gasoline--plus I had a portable generator for emergencies.

-Bill

mike95490

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

rickeolis wrote:

I'm running a 500 watt system right now, but want to go to a 3000w PV setup using PV\batteries while staying on the grid.
How can I design this to make use of 100% of my PV made energy primarily, and then when demand gets high (as in water heater coming on, etc.), that it will allow for the grid to feed me this as needed?

The batteries will cost you about 20% or more, in charging losses. It may shift your usage a bit, but you will loose power when sun comes up, and you have to recharge low batteries. So you run an extra hour after sundown, but you don't generate till 1:30 after sunrise. Charging, inverter, ohmic losses all affect your total engery production.

rickeolis

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Man, now you guys have me considering net-metering again...
Initially I had it all planned out with a Xantrex GT-3.0 and a set of Kyocera GT-130's, until I went to the dealer to have an estimate done. They quickly went from my idea of about $15K to around $35K as I walked out.
I guess it's harder to GROW into a net-metered system, as it would be to start small with a battery based setup.
Well, at least with the Outback, I could go either route in the end, and have a backup when the power is out.

Roderick

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Ouch! If your state has "sell at wholesale, buy at retail," then yes, I wouldn't go for it, either.

I will say that doing it yourself does not disqualify us for the state rebate where I live - the rebate is just 15% less, that's all. Again, my condolences if your state is "pro install or no rebate."

I hope this isn't an intrusion, but I'd be curious as to where you're located (which state or country).

rickeolis

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Guys, I'm in New Mexico, and not on PNM, (who by the way does have a great RE rebate\allowances program) because I'm out of their covered area.
When I went to a solar vendor, the person there told me how I could re-coop nearly 50% of my investment with rebates and allowances, and then I mentioned who my electric service supplier was and he literally said (quietly) "Oh crap", from there the conversation was basically, him showing me what they have for sale, and thanking me for dropping by.
I went to one other dealer who was straight up with me and said that on average, in the place I live that I would need to invest in about $42,000 total parts and labor to break even on my bill and that I'd only see $2000.00 fed rebate, and about $2700.00 state, period, ever.
That is based on my current consumption of around 750KW a month.
Since losing interest in going that route, I'm simply building a solar array slowly but surely on my on, and so far it's already showing promise.
It's just the fact that when I get my tax return this coming spring that I want to spend most of it on a larger system that will some day cover the home's needs.
Two things I plan on is getting a Sundanzer fridge and freezer, and switching my electric water heater to a tank-less LP unit.
I've already replaced ALL my lights to the small fluorescents and my current PV system runs those in the evenings.
Thanks-

BB.

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Conservation is the first way to go... Get a kill-a-watt meter and/or the whole house meter talked about in another thread here. Put all of your electronic equipment with wall-warts and standby losses on power strips to shut them off.

Regarding your power use--750 kWatt*hours is probably what you intended to type.

If you have lots of sun, solar hot water and solar heating would be a good starting point. Look at this at the same time you are looking to install a tankless water heater. There are some tankless water heaters that are designed to work with solar hot water, and others that will not work well (normally a tankless heater assumes that there is a minimum temperature rise of the cold water--with pre-warmed solar hot water, they cannot throttle the flame back far enough to warm the last few degrees). Other systems use the electric hot water tanks to store the solar heated water and as a backup heat source on cloudy days.

There is a fridge thread here too and I would suggest that you either get a good energy star rated fridge, and if you really want to save money on power, convert a chest freezer to a fridge. Regarding the SunDanzers and other manufacturers of high efficiency fridge/freeze, check the energy star ratings--for many models/manufacturers, there is almost no difference in energy usage (or, at most, only a few dollars a month in savings) vs the 100's to 1,000's of dollars in premium prices that these vendors are demanding--and unless you are on off-grid power, it is very unlikely that you will save enough in power costs to offset the high purchase prices.

-Bill

rickeolis

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Hi Bill, I've read your posts here and on 3 other forums, I appreciate your input a lot.
Megawatts, wow! Fixed, thanks.
I have switched my large TV and Bose system to a power strip, and did the same for my computer and LCD monitor too.
I know I need a KillaWatt to begin looking at my usage for sure. I'm getting one very soon, thanks!
Well, my fridge\freezer combo had an EnergyStar tag on it when bought claiming about $721.00 a year in electric costs, are you saying that if I were to buy a new 8cf fridge and another 8cf freezer, that my yearly expenses would not change all that much? I'll try to find more info on that, I appreciate the info.
Winter heating is a real problem for me, so I have been looking into solutions. I've insulated more, and am using window coverings (double pane, and plastic film) in the winter, but the furnace is still on a lot. Are you impressed by any of the 3' X 12' air-to-air heating panel systems (or similar)? The quotes I've seen on water-based systems are outrageous, but I'm still looking.
Anyone else? Thanks-

crewzer

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

I'm with Bill on this -- especially the fridge suggestion. For example, take a look at the Sears Kenmore #67182:

20.6 cu. ft. (15.3 fridge + 5.3 freezer)
432 kWh/yr energy use (based on 90 F test standard)
Today's price: $550.

HTH,
Jim / crewzer

rickeolis

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

I guess a "killawatt" read would help answer the Fridge issue rather quickly for me. Thanks much, that was news for sure. i thought the Sundanzers were extremely efficient.
Do you guys know the actual difference in Outback's Inverters called "Off Grid”, and the “Off-Grid Export" style? I read the spec's on both but can't see a difference. :?

crewzer

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

The export inverters are 230 VAC @ 50 Hz out.

BB.

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Rick,

I think you have miss-read the energy star tag... $721 per year is probably 721 kWhs per year... At $0.10 per kWhr that is $72.10 per year estimated running price or ~$6 per month (60 kWhrs / month). Frost free models consume more energy--but after years of having frost free, then getting a non-frost free freezer--I am not sure that saving the power was worth having to defrost my freezer twice a year was worth it to me.

Look at the Energy Star web site--they have listing for older appliances and a check sheet on whether or not to change out older appliances. 721 kWhrs per year is not bad for a large fridge/freezer, but you can get below that pretty easily with newer models (20+cuft range). But, it might not be worth the money to save 721-432= 289 kWhrs (or $29 per year, or $4 per month)...

http://www.energystar.gov/

To be honest, the SunDanzer's look to be no more efficient than a good Energy Star Fridge from Sears today (I think that is what I concluded in Fridge thread)...

Also, look at the cost per cu.ft. of cooling in a fridge/freezer. Basically, volume is a cube (to the 3rd power) and surface area is to the square (to the 2nd power)... So, as your freezer gets larger, the volume of food stored goes up faster than the surface area (a 1 foot cube has 6 square feet, a 2 foot cube has 10 square feet, so for double the volume, you have a bit more than 50% more surface insulation--where you get heat loss)... Basically, one large fridge will, usually, be more efficient than a smaller fridge plus a bar fridge for overflow.... Check the kWhr tags--the small fridges (few cu.ft.) use almost the same amount of power as the larger 17 cu.ft. models.

I have not installed any solar hot water/hot air at my home--just solar PV with Grid Tie... And that was because of the great rebates and my fear that the State of California was going to jack up my rates by 2-3x because of their screwed up Public Utilities Regulatory Commission (remember ENRON and our blackouts from 5-6 years ago)... In general, a solar hot water system, while expensive (plus maintenance costs) seems high, it still appears to be only 1/10 to 1/4 the cost of a solar PV Grid Tie system to offset the same amount of costs (costs of electricity vs natural gas/propane). Also, since the panels are much more efficient at capturing heat (rather than converting electricity), you don't need nearly as big of panels for heat capture.

You can probably build your own solar hot-air panels, and while you can build the solar hot water and do your own piping and pump design/installation--it will depend on your skills and how professional a system you want. If you have lots of winter sun, it is probably worth looking into solar thermal systems more.

-Bill

crewzer

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

I haven't had a chance to crunch Sundanzer's numbers in a while. One easy calculation, though, is that it would appear to take one Sundanzer 5 cu. ft freezer plus two of their 8 cu ft fridges to roughly equal the Sears 67182 capacity. You'd also have to use Sundanzer's 90 F energy number's to somewhat normalize the energy use comparison.

To be fair, however, you'd have to factor in the inverter's efficiency for running the AC fridge.

Here's another Sears fridge with good specs:

Model #64242
21.7 cu. ft. (15.2 fridge + 6.5 freezer)
448 kWh/yr
$620

HTH,
Jim / crewzer

rickeolis

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

BB, you must be right, I just recall that number in a big font on the sticker, it's probably the kwh's, not cost. I'll check it again this weekend.
I'm really glad you pointed that out though. My fridge combo is only about 4 years old my wife usually keeps it pretty well loaded so the efficiency should be good. Like I said though, the only real way to tell is with the 'killawatt'. Man, that $2000.00 saved can go into more panels!! Where do I send a check?!?

I did put together a 3' x 4' panel and tested it in a smaller RV I have. The air coming out on a 70 degree day measured at about 95 degrees and felt very warm to the touch, but did little to heat up the RV, even after about 3 weeks in place. It was mounted on the roof pointing south and up at about a 30-degree slant with insulated 6" hoses running in and out. I used a 15-watt solar panel to run a 4" computer fan motor for flow and I felt the air as far as a foot away. I talked this over with some guys on another board and they said that since I was only using glass from an old window and too small of a panel that the efficiency was too low.
While talking to a vendor that sells these, he was saying that one of his 3'x12' panels should heat an average living room on a cold (40 degree) day just fine. His sell for around $750.00 carry out. I'm kicking it around...

BB.

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Crunching the numbers for Sundanzer and Sears (2 fridges + 1 freezer vs 1 fridge/freezer). Data from:

http://www.sundanzer.com/PDF/SunDanzerDCPowered.pdf

[DCF165 0.441 kWh/day + 2*DCR225 0.198 kWhr/day ] * 365.25 d/yr = 306 kWhr/year

448kWhr/yr - 306kWhr/yr = 142 kWhrs/year saved or $14.20 per year or $1.83 per month saved electricity ($0.10 / kWhr)

$974 + 2*$1074 = $3,122 (MSRP)

$3,122 - $700 (sears ~ MSRP) = $2,422 difference between SD and Sears

$2,422/$14.20 per year = 170 years payback at $0.10 per kWhr.

Cost of Ownership vs Electricity kWhr Costs:

Assume 15 year life and price delta of $2,422:

SD Price + x$/kWhr * SDkWhrs/yr * 15 years = Sears + x$/kWhr * SrKWhr/year * 15 years

SD Price - Sears = x$/kWhr * (SrkWhr * 15 - SDkWhrs/year * 15)

SD Price - Sears/[(SrkWhr - SDkWhrs)*15]=x$/kWhr (price point where kWhr price equals purchase price of the two products)

$2,422 / [(142 kWhrs/year * 15 years)] = $1.137 / kWhrs would be the break even point cost savings point (assuming 15 year service life) between the three Sundanzer units vs 1 $700 Sears refrigerator--more than $1.14/kWhr, buy the Sundazers; less than $1.14/kWhr, buy the Sears (if I got the algebra right).

-Bill

crewzer

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Bill,

Nicely done! Now, let's see, when you factor in the cost of money over 170 years... :evil: :roll:

Regards,
Jim / crewzer

rickeolis

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

"ENERGY STAR qualified refrigerator models use at least 15% less energy than required by current federal standards and 40% less energy than the conventional models sold in 2001." 8-)

Bill, I got this from your link to the EnergyStar website, that and other interesting things I just read about make it quite an interesting website to browse!
Man, dishwashers really suck down the watts too.

System2

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

It sure sounds like I am in a similar boat to the topic of this thread. The state here has no incentives that can be applied, as it is only a tax break, and being on social security does not put one into a tax bracket that benefits. The net metering law that was finally passed is worded such that it only applies to 3 of the utilities in the state. The utilities in this area are not any of those. TVA does offer a "Generations Partner" program that is extremely one-sided. You must sign a 10 year contract with TVA, giving them complete control over your system, including maintenance, which you must pay for. In return, you get paid a fixed rate per KW/hr for what you generate, and you buy all of your power at retail. The slightly inflated wholesale sell rate is fixed, while the higher buy rate is not, and continues to climb. You are not allowed to use any of the generated power from your system, as it's not your system to use any more, until the 10 year contract period is over. Such a deal! No thanks.

"Net metering? Sure we do that! Isn't that where you pay your bills online over the net?" That was the response from my local utility when I stopped by to ask. When I tried to explain, eyes glazed over and I was told I needed to talk to the owner, who was out of town. I was told to come back on friday. So back I went on friday, and had a short meeting with the owner. At least he had heard of net metering, but his interpretation was similar to that of TVA, where the customer has a wholesale sell meter, and a retail buy meter. He said that was a fiscal nightmare to manage. I tried explaining net metering to him in detail, gave him some information, and encouraged him to consider it. I explained that a single meter can perform the function. His first concern, and well founded, is that they only recently (in utility terms, really about 5 years ago) upgraded their entire customer base to remote reporting meters. These meters report rotation, so every revolution of the meter is reported back to the central computer. The meter will report the same, regardless of direction of spin, so power generation will count the same as power consumption. They do not send out meter readers anymore, despite still charging us the $25/mo rural meter fee that was added to cover the cost of reading rural meters. He also raised concern that their buy contract with TVA prohibited purchase of generated power elsewhere. I don't feel that net metering is a power purchase, but he is not so sure. I did explain generation credit vs consumption being balanced by the meter as a net use or net generation over time, and that net generation credit could be reset to zero at certain intervals with no actual money changing hands. Only time will tell I guess.

For now, I have a standalone PV power system that charges a 500 AH @ nominal 48 VDC battery bank through an MX-60. I use the sinewave inverters in a pair of APC SmartUPS 2200XLNET UPS units to generate power to run most of my home and shop. I make use of the built in load switching to switch between grid power and generated power. It's quite simple really, as I just have the UPS units fed from a breaker in a sub-panel. If I am running totally on grid power for any reason, such as at nights or during extended cloudy weather, a grid power failure automatically forces the switch to battery backup. I normally switch the breaker off during the day to force my system to run on PV power most of the day, and switch it back on to use the grid later in the day when PV power begins to fall off. This allows the batteries to get topped off again before the PV output drops to zero. I was using the Aux output of the MX-60 to control a contactor that switched on/off power into the UPSs, but found that using the float detection through the MX-60 just did not utilize as much PV power during the day as I wanted to use.

With this method, since I replaced my battery bank a couple of months ago, I have managed to shave $200/mo from our utility bill for the last 2 months. I watch battery bank voltage like a hawk to make sure that the batteries are not run down more than 10% DoD (90% SOC). I want to be sure that if a grid power failure were to occur, I have enough capacity to carry the house for 2 to 3 days of no sun and still not reach 50% DoD.

My primary load is an upright Sears Kenmore manual defrost freezer converted into a cooler through the use of a digital electronic temperature control. This maintains a steady 32.3F internal temperature throughout with a 20 watt "stirrer fan" inside that runs all the time. My kill-a-watt shows the total power consumption of that cooler and fan to be 1.44 KW/Hrs when averaged over a 24 hour period. I read the power for over a month to get an accurate account of power consumed. Secondary home loads are intermittent use of 2 TVs, a VCR, 2 DVD players, 2 SatTV receivers, CFL lighting throughout, 2 laptops, and a 4 camera, 2 monitor video security system. The primary security system monitor stays in stand-by mode (powers the cameras and parasitic loads, but the 90 watt sucking 17" monitor itself is powered down), and I added a 22" LCD slave display that consumes less power, 40 watts as measured by the kill-a-watt. The shop loads are flourescent lighting only when needed, a pair of 6.5 watt LED (white christmas lights) strings for ambient lighting, and a soldering station when needed. The shop equipment itself is on grid power unless grid power is down, as those can be huge power suckers when running. They get used very rarely though. Our big freezer is on grid power, with the option of switching to PV power during extended grid outages. We have a pair of 4 KW gensets, one is gasoline and the other propane. Our stove and furnace are propane as well, and I have a solar water heater unit in storage that has yet to be installed. We get freezing weather here, so I would have to go with a heat exchanger type system and circulate an antifreeze solution. For now our home has an electric water heater that is tied to the grid only of course. I intend to use that as the storage tank for the solar hot water when that time comes.

I too would like to maintain my batteries at float, and channel any additional power from the PVs to alleviate consumption. I feel that I am doing the best for my PV system investment, but would surely love to do better. Anyone have any advice on how I can economically improve my existing system to further reduce grid consumption that I have not already covered? Being on social security does not lend itself well to expensive options ;-)

Thanks in advance.
Bob

System2

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

"Net metering? Sure we do that! Isn't that where you pay your bills online over the net?" That was the response from my local utility when I stopped by to ask.

Hi Bob, I'm a certified card carrying solar moron so I don't have answers for you. The experts I am sure will chime in shortly. Just a comment about your interaction with the local power agency - what a shameful exchange (on their part). Did you happen to catch the recent special on TV about solar energy in Germany - they have very favorable policies regarding PV generation that should be (IMHO) adopted in the US.

Oh and a question - is that a photo of your PV panel with the snow on it?

BB.

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Bob,

Sorry to hear about the issues with net metering in Tennessee... However, I will be the first to admit that Net Metering does not make sense to a utility (buying and selling power at retail). It is just the law makers that have enforced this onto the utilities (and yes, Momma did not raise no dummy--I have 1 year Net Metering with Time Of Use billing).

Funny (Ha. Ha) how that $25 / month rural meter reading sticks on your bill... Might be interesting to see how the law was written. Might not be able to continue the charge.

Looking at TVA's bills--At least Al Gore's, it was around $0.07-$0.08 per kWhr. Our base rates here start at $0.11 per kWhr for flat residential and can rise to $0.50 a kWhr for peak time of use (and heavy power consumption--over about 900 kWhrs per month). With TOU and off-peak, I can get down to about $0.09 per kWhr. (but you have to be under 300 kWhrs/month to be at this rate).

One suggestion I would make, is to 1. use a smaller fan to mix the air--20 watts is too big and too much of a heat source--that is the same as leaving a 20 watt light bulb on in your fridge 24/7/365 (and using the compressor to remove that heat from the fridge)... And 2. connect the fan to only turn on when the compressor is running. Between those two suggestions, I would expect your "chest fridge" power consumption to drop by ~1/2.

At 1.44 kWhrs / day for a fridge--that is, roughly what a modern Energy Star 20+cuft frostless fridge with ice-maker would consume. With your setup, you should be 1/2-1/4 that amount of power (again, the fan, and possibly the digital temp controller are your 24/7/365 loads here--reducing them can help a lot).

Also, you home does not sound like it uses that much energy for you to save $200 per month... That is over 2000 kWhrs at $0.10 per kwatt*hour (don't know your rates)...

So, something is a bit off here. I can make lots of guesses here--that would all be wrong. So questions instead.

1. How big is your solar PV system (watts of panels)?

2. What is your power metering? Flat use, Time of Day, Rate(s)?

3. How many kWhrs (day or month) are you generating (via solar) and consuming (via grid)?

4. Do you have any large loads (well pumps, A/C, electric kitchen/hot water)? (large amounts of kWHrs, but not 24x7 usage)

5. Have you added up your "small loads" that run 24x7? (My entire home averages about 278 watts 24x7 or 200 kWhrs / month--if I keep on the kids to turn off lights). Adding several computers + cameras + recorders + Sat TV +... and you can be talking about 200 kWhrs per month... But if you have a 2,000 kWhr/month bill--saving a 100 kWhrs is small potatoes (it is a start--but not large in the grand scheme of things).

In any case, saving power can include placing everything on power strips (washer/drier/cell phone chargers, VCR's, HD TV Receiver, SAT TV Receivers/etc.) that takes more than a couple of watts when shut down.

For example, my washer / drier take ~9 watts when off--turns out that if I turn them off with a power strip, my average washer/drier kWhr/month usage drops by 1/2---because the 9w*24hr*30days/month=6.5kWhrs/month. Or, in my case, almost 4% of my total electric bill.

HD and SAT TV receivers typically draw quite a bit of power "turned off" to keep program guides up to date. My HD Receiver is warm to the touch when "turned off". Not a good thing when trying to save energy.

My 10 year old stereo/CD/Tape player took 44 watts on "standby"...That was about twice the power of my laptop when turned on. Putting the stereo on a power strip saved another 16% of my monthly power bill/usage.

Regarding using your batteries and inverters--sounds like a great way to make your own "net metering". I would suggest looking at your inverters to make sure that they are, relatively efficient. It is possible that when operating in Pass Through mode, you are still wasting quite a bit of power (UPS's are not generally optimized to save energy--replacing with an Outback, Xantrex, or other inverter may be a better move--although they will not be cheap).

Lastly, you could look at a battery monitor and see if one of them can be programed for your needs:

http://store.solar-electric.com/metersmonitors.html

The Xantrex "E-Meter" has an RS-232 option that you could program/operate with a low powered computer... Or maybe the generator contacts can be programed for what you want.

-Bill

crewzer

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Anyone have any advice on how I can economically improve my existing system to further reduce grid consumption that I have not already covered?

Bob,

Two quick suggestions, if I may. One might be to rig up a timer to run the "stirrer fan" part-time. For example, thirty minutes on and thirty minutes off would cut your energy use by 20 W x 24 hrs/day x 50% = 240 Wh/day... less, of course, the power required to run the timer.

Another idea would be look for opportunity loads to run while the MX60 controller is in Absorb and/or float mode(s). The controller typically "leaves" energy behind when it's operating in current-limit mode. For example, after the controller has been in absorb mode for ~30 minutes or so, you might find that you can operate your washing machine or a small vacuum cleaner without the controller dropping out of absorb mode. Similar options might be making a point of shifting some computer- and/or shop use to when the controller is in absorb and/or float mode.

Finally, the solar water heater should help. In the meantime, it might be worth checking into if your electric company offers water heater plans like these in my area:

http://www.dom.com/customer/pdf/nc/riderrlc.pdf
http://www.dom.com/customer/pdf/nc/sched01w.pdf

HTH,
Jim / crewzer

System2

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Jeff in Calif wrote:

"Net metering? Sure we do that! Isn't that where you pay your bills online over the net?" That was the response from my local utility when I stopped by to ask.

Hi Bob, I'm a certified card carrying solar moron so I don't have answers for you. The experts I am sure will chime in shortly. Just a comment about your interaction with the local power agency - what a shameful exchange (on their part).  Did you happen to catch the recent special on TV about solar energy in Germany - they have very favorable policies regarding PV generation that should be (IMHO) adopted in the US.

Oh and a question - is that a photo of your PV panel with the snow on it?

I don't watch much television, and when I do it's usually a DVD or some other movie. So no, I have not seen anything about Germany.

Yes, those are my panels covered with snow. They were tilted for winter, yet the snow sure did stick well ;-)

Forgot to add, that snow picture was taken from roof level.

System2

Re: On-grid, not net-metered; how to control RE first, then grid when needed?

Bill

Our utility is a membership co-op that buys power from TVA and distributes it to the members. They mark up the power, then add fees, adjustments, and taxes. Funny how they add a fuel adjustment charge when our power comes from the local hydroelectric facilities. Last time I did the calcs a few months ago, it worked out to about $0.31 per kWhr once all the extra charges were added in. Of course, the less you use, the more the apparent kWhr cost due to that $25/mo rural electric fee. This is flat rate.

I had shopped around to find a fan that had the desired shape of airflow, at the least power. The 20 watts is actually the power consumed when the compressor is off, so that includes the temperature control. I really don't want the milk to freeze, as this destroys the beneficial enzymes the same as pasteurization does. Without the stirring fan, there was a 5 F differential from the bottom to the top. I can connect the fan to the temperature control so that it is switched with the compressor. The compressor runs for about 1 minute out of every 10 minutes, so that should be often enough to keep it stirred. I will be adding more insulation to the milk cooler tomorrow, while it is shut off and empty, waiting for another load of milk. I'm going to wrap it head to toe with foil-foam-foil radiant barrier, all except for the compressor and condensor of course.

My primary array is 900 watts stc. My secondary array is 600 watts stc. The MX-60 has been reading between 9.5 to 10 kWhr a day at this time of the year.

In the 3 months prior to changing the battery bank, my utility bills showed that power consumption had climbed to nearly 1000 kWhr/mo. Maybe some of that was from the battery chargers in the UPSs trying to pump grid power charge into that old battery bank all night. It tipped me off that something was seriously wrong with the system.

Since the battery change, the next month (batteries changed during a billing cycle) utility bill showed power consumption had dropped to a bit over 600 kWhr, and the last 2 utility bills showed power consumption to be under 300 kWhr/mo.

We do have a lot of small loads, which are handled well by the PV system now that it is working properly again. I went through and measured them all with the kill-a-watt, doing away with some of the phantom loads. Some I can't practically get rid of due to family not wanting to go through switching power strips and reconfiguring everything that loses settings when power is turned off. We have the following grid powered 240 VAC electric power hogs - heat pump for summer, water heater, stacked washer/dryer, and a water pump. The 240 VAC loads I cannot power from the PV system as it is currently configured, as I just cannot afford to buy a new sinewave inverter large enough, nor do I feel that they would be a wise use of PV resources. The water pump would be the only 240 VAC item I might consider, but I already tried rewiring for 120 VAC and it won't even start on grid power that way. The 500' wire run was sized for 240 VAC and it would be very expensive to trench in a new power cable. The fridge and freezer are normally on grid but do have PV power option in the event of extended grid failure.

I'm not sure if this additional information is of any help but I sure hope so.



Jim

I will probably try switching the fan with the compressor and see how that works out. I would rather spend the extra power than to ruin a few hundred $ in milk. We can store 32 gallons in that cooler, a months supply of milk for our family, and other families in the area. This is why we maintain as close to freezing as possible, to allow the milk to remain viable.

I try to do exactly that, run as much as I can during the day while the sun is shining. If we were allowed net-metering, it would be so much easier, as I could just leave everything on the grid, and have a grid-tie inverter shove everything at the grid above and beyond what the batteries require. Because grid power is so unreliable here, there is no way I would go without a battery bank, so that would mean an Outback grid-tie inverter. It took the neighbors a while to get used to seeing our lights on at nights even when the grid is down. It still confuses the heck out of the utility line crews when they see our lights on while driving the streets looking for the downed power lines after storms. If it were not for that remote reporting meter, I would have probably gone "gorrilla" years ago ;-)

Thank you all
Bob