Feed-In-Tariff, configuration to maximize sell but not buy

caribbeandan
caribbeandan Registered Users Posts: 8 ✭
in Solar Beginners Corner #1
Greeting everyone,

I live in the Caribbean and 1 for 1 grid tie systems seem to be rapidly coming to and end or at a bare minimum is to be replaced with a Feed-In-Tariff type system by our local government. Too much instability on the grid they say. Less and less people are paying utility bills.

Electricity costs 51.2 cents a Kwh where I live 2nd or 3rd highest in the world. Feed-In-Tariff would allow me to sell power at 17 to 26 cents a kwh but if I need any from the public utility it remains at the 51.2 cents costs. Feed-In-Tariff requires a minimum of 10Kw of panels to participate and basically is a contract for a specified period of time to get paid a specified rate.

I currently use about 22KW to 34Kw a day. Most of the power is used at night. Yesterday I ran the dishwasher (with heat dry), electric dryer, electric water heater, electric water pump and some ceiling fans and a plasma tv for 2 hours at night to see the most wattage used in a 2hr time frame. Basically, everything running at once… about 8 to 9khw. Normally I don't run everything at once and don't use the heat dry feature on the dishwasher but I just wanted to see the maximum potential load. I realize somethings like the electric dryer and the water pump spike as much as 3 times there amperage but for a short period of time.

If I could do just grid tie with 1 to 1 power exchange I am able to get by with 8,400watts panels and 482Ahm battery to keep grid tie working even during power outages during the day with an outback 8048a inverter and a couple midnight classic chargers.

Instead, given the current Feed-In-Tariff rules I would need to use 10KW of panels whether I need them or not and possibly a large cheap battery bank (used forklift battery) if I don't want to buy power at this insanely high rate.

I have found reconditioned forklift batteries (92% capacity) at 48V 1384ah or the lowest 48V forklift batter at 804ah. It appears that if I go with a 1384ah battery I am going to need 3 classic midnight chargers. I think the preferred charge rate for the battery is at 39.5amps. It’s a model 24-85-21 battery. I’m told forklift batteries want anywhere from 10 – 20% total ah for charging and it gets worse with the age of the battery.

One formula I saw on this forum suggested I take 10080 (panel size)/ 48 = 210 X 4 = 840 Amp @ 48 volt size.

I would like to swap out some of these high draw appliances but on the other hand I understand its best to draw forklift batteries down at least 50-80% for efficiency. Apparently it’s best to use aggressively and charge often.

So I want to use batteries to run these high draw appliances at night, because everyone is at work during the day. I want be able to discharge 50% at night possibly even sell battery power if necessary back to the grid during the night.

Charge the batteries, power minimal load during the day and sell excess power to the grid.

Perhaps as I collect more money I can replace the high draw appliances and sell even more battery power to the public utility or simply save the money for the eventual needs to replace pv electronics and batteries.

One company has set up 5MW of panels to sell power to the public utility at 19 cents a Kw but they are selling and not using an power.

It’s a puzzle I’m try to arrange the pieces around the 10KW minimum array size needed to get at least some type of compensation from the public utility rather than go completely off-grid. Thanks in advance for your attention and providing this forum for discussion.

CaribbeanDan
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Feed-In-Tariff, configuration to maximize sell but not buy

    Welcome to the forum Dan.

    Sounds like they want to stop solar installs there. Paying 1/2 what it costs ought to do that.

    You're up against it. As expensive as your utility power is you need to find some great bargains in order to make off-grid power feasible. It's generally about $1 per kW hour.

    So if you base your system of usage of 22 kW hours per day and store all the energy you get the need for a fairly large battery bank around 1000 Amp hours @ 48 Volts as a minimum. Then you'd want to produce around 100 Amps peak current to charge it and that will take about 6.2 kW of array to do, plus two charge controllers.

    In other words your numbers don't look too far off the beam.

    If you have to plan around a minimum 10kW array: expect about 160 Amps of current and enough battery to handle it, about 1600 Amp hours @ 48 Volts.

    Alternative (and I don't know how this would fly): have some of the array feeding your battery-based system for nighttime use and the rest feeding the home/grid directly through a standard grid-tie inverter. Less battery, perhaps less charge controller, meets the array size, supplies plenty of daylight power with minimal sell-back, gives you nighttime battery power to avoid buying electric, and the only downside is the complexity of dual system and need for two inverters instead of one. Possible?
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  • caribbeandan
    caribbeandan Registered Users Posts: 8 ✭
    #3
    Re: Feed-In-Tariff, configuration to maximize sell but not buy

    Makes sense to sell directly to the utility company rather than from battery to utility for best return.

    Ok how about this split:
    24 panels at 280watts each = 6720 Kw tied to 8048A outback inverter with 1072Ah battery
    12 panels at 280watts each = 3360 Kw tied to separate grid tie micro-inverters to utility no battery

    3360 X 4hrs = 13,440 13.4 X .26 cents = $3.48 energy sold per day X 365 = $1,270.20 total per year. Maybe a little extra overflow from the Outback inverter to add to the mix.

    Are the micro inverters that much better than a single grid tie inverter? What would be the least expensive option for the 12 panels? How would you do the split? Any recommendations on the grid tie only inverter(s). The smaller inverter would have to be set to sell only. Can both large and small inverters sell at the same time or does one system have to be truly off-grid with no tie to utility company?

    As far as forklift batteries go these are the specs and new prices…Used is about 40% to 50% discount.
    http://gbindustrialbattery.com/Forklift_Battery_Sizes_and_Specifications_Zone15.html Seems like the 48V batteries only come in 804, 928, 1072, 1182, 1206, 1340 & 1608 Ah configuration.

    I have read many of your posts throughout the forums. Thank you so much for sharing your expertise.

    Dan
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  • ButchDeal
    ButchDeal Solar Expert Posts: 35 ✭
    #4
    Re: Feed-In-Tariff, configuration to maximize sell but not buy
    caribbeandan wrote: »
    Makes sense to sell directly to the utility company rather than from battery to utility for best return.

    Ok how about this split:
    24 panels at 280watts each = 6720 Kw tied to 8048A outback inverter with 1072Ah battery
    12 panels at 280watts each = 3360 Kw tied to separate grid tie micro-inverters to utility no battery

    3360 X 4hrs = 13,440 13.4 X .26 cents = $3.48 energy sold per day X 365 = $1,270.20 total per year. Maybe a little extra overflow from the Outback inverter to add to the mix.

    Are the micro inverters that much better than a single grid tie inverter? What would be the least expensive option for the 12 panels? How would you do the split? Any recommendations on the grid tie only inverter(s). The smaller inverter would have to be set to sell only. Can both large and small inverters sell at the same time or does one system have to be truly off-grid with no tie to utility company?

    As far as forklift batteries go these are the specs and new prices…Used is about 40% to 50% discount.
    http://gbindustrialbattery.com/Forklift_Battery_Sizes_and_Specifications_Zone15.html Seems like the 48V batteries only come in 804, 928, 1072, 1182, 1206, 1340 & 1608 Ah configuration.

    I have read many of your posts throughout the forums. Thank you so much for sharing your expertise.

    Dan

    I would put it all on the outback system, but configure the outback for GRIDZero configuration.
    The outback will feed in as well since it is bimodal but in GRIDZero it will try NOT to feed in and to use the battery as needed.
    The MATEIII will program the battery charger for the AH and type of the battery.
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #5
    Re: Feed-In-Tariff, configuration to maximize sell but not buy

    Have you seen the Rules and Regulations to the FIT program ?? I saw a discussion where some have a distribution scheme where they install a second meter and they take all the power you produce and then meter it back at retail rates. Seems with a 10 KW minimum, they want you to be a producer and not so much a user.
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  • caribbeandan
    caribbeandan Registered Users Posts: 8 ✭
    #6
    Re: Feed-In-Tariff, configuration to maximize sell but not buy
    Blackcherry04 wrote: »
    Have you seen the Rules and Regulations to the FIT program ?? I saw a discussion where some have a distribution scheme where they install a second meter and they take all the power you produce and then meter it back at retail rates. Seems with a 10 KW minimum, they want you to be a producer and not so much a user.

    I had a permit pending for normal grid tie with a 8.4Kw system and small battery bank placed on hold along with many others when the local government thought we hit the quota mark of 10MW for the Island. 3 months earlier they said we were far from this quota. Meanwhile the Governor signed Act No. 7586, Bill No 30-004 to implement Feed-In-Tariff.

    As things stand, no standard grid tie or fee in tariff agreements are being processed, everything remains on hold. Something as simple as adding up all the permits to see where things stand is taking weeks. Our utility company is owned by the local government. Historically the local government has been delinquent paying its electric bills for public schools, hospitals and other buildings. Approximately 1/15 off our Islands electrical use is unaccounted for...

    quote regarding the FEE-IN-Tariff
    "A Feed-in Tariff system operating pursuant to this subchapter must be greater
    than 10kw and smaller than 500kw of installed capacity, to allow as many entities as practicable
    to receive the benefits afforded by the FIT Program.

    Power purchase agreements must be offered on a first-come, first-served basis
    until owner customer generators within each island have reached the aggregate capacity for that
    island."

    Dan
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #7
    Re: Feed-In-Tariff, configuration to maximize sell but not buy

    If you have to have a 10Kw system then on good days (you guys get long great sun I would think) you should create about 50-60kWh. If you use 22 kWh strictly off the grid and sell the 50-60 kWh to the grid even at half price you should be net zero anyway with a grid tie setup. I know it will be some split of the consumption, but just as a the extreme example.

    Upside:
    1. No batteries to maintain and replace
    2. highly available grid tie inverters.
    3. you get paid or use every watt produced, off grid doesn't work that way.

    All this assumes the utility is pretty reliable.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #8
    Re: Feed-In-Tariff, configuration to maximize sell but not buy

    I am a big believer in conservation--And I would do as much as I could before I started down the Solar Power road.

    For example:
    caribbeandan wrote: »
    I currently use about 22KW to 34Kw a day. Most of the power is used at night.

    Yesterday I ran the dishwasher (with heat dry) electric dryer

    These are going to be your choice. Both are heavy users of power. For the dishwashers, many now include energy savings modes (use less heating).

    For the electric drier--You might see if you can get an "extractor"--Basically a very high speed spinning drum to drive out more water. Can get much more water out of heavy materials and reduce drying time. However, they can stretch fine clothes (lots of centrifugal force).

    We do not see many of these in the US--Perhaps you can find more options (European) around your place:

    http://www.laundry-alternative.com/product/Spin-Dryer
    electric water heater

    Heat pump water heaters (basically reverse refrigerators or A/C system). 2-3 as efficient as a regular resistance type water heater. "Waste" is cold/dry air--Perhaps "free" A/C and dehumidification is useful in your area?

    If you already have an A/C system that is use a lot--There are "desuperheater" devices (freon to water) heat exchangers that dump the "waste" heat from the A/C system into your hot water tank.
    electric water pump

    Depending on the water pump and application (well, cistern, etc.)--Some of the newer pumps can be much more efficient than older/cheaper pumps (2x?). New controllers (VFD--Variable Frequency Drives) can be used with some pumps to slow them down if they are "over sized" for the application (larger than needed water/well pump).
    and some ceiling fans

    There are now more energy efficient fans (and variable speed--slower fan, use less energy)--But some of the prices seem a bit on the scary side for a new fan.
    and a plasma tv for 2 hours at night to see the most wattage used in a 2hr time frame.

    New LED TVs (at least in the US), use 1/2 to 1/4 the power of a typical Plasma TV.
    Basically, everything running at once… about 8 to 9khw. Normally I don't run everything at once and don't use the heat dry feature on the dishwasher but I just wanted to see the maximum potential load. I realize somethings like the electric dryer and the water pump spike as much as 3 times there amperage but for a short period of time.

    Measuring your loads--Always a very good place to start. Spending a $1,000 to save $5 per month may not make any sense (i.e., new dishwasher to save money, but using "ECO Dry" may get you 80% of the savings with zero additional investment.

    Another point--If you use A/C--Dumping less heat into the home (more efficient TV, laptop computer, LED lighting, more efficient fans, more efficient refrigerator, etc.) saves you having to pay to move the heat out of the home via A/C.

    More insulation (attic), even shading by landscaping can help too. On my home, placing solar panels on the roof dramatically reduced our attic temperatures too.

    However--It depends on your home--In our area, we have a very temperate climate and the older homes (like mine) originally had zero insulation and leaky walls/single pane windows. We do not have A/C--And with the better insulation and low E double insulated windows--Made our homes much more liveable. And, of course, reduced our (mild) winter heating bills too. Now the issue of no water and dead landscaping (drought--Another issue).

    New homes have quite a bit better insulation.

    In the end, energy usage is a highly personal set of choices. What worked for me, may not be applicable to you...

    However, pretend your power bill went up to $2 per kWH (possible what your off grid solar power costs could be--All in price, installation, maintenance, battery replacement every X years, new inverters/charge controllers every 10+ years, etc.)... What would you change in your home if the power bill went up 4x over night?

    In the end, conservation is usually a better first investment for your money than going with a Solar Off Grid/Hybrid/Battery power system.

    -Bill "my two cents" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • caribbeandan
    caribbeandan Registered Users Posts: 8 ✭
    #9
    Re: Feed-In-Tariff, configuration to maximize sell but not buy

    Some very good advice BB... little by little our family has been whittling away at our electrical use within the last year. My example was more of a what / if situation. I was trying to calculate the most current that could be drawn at once while the sun was down and how best to utilize 10Kw minimally required size of array by local government under Feed-in-tariff.

    A year ago 34KW a month was at the high mark within the last 3 to 4 months 22-24 kw is more often observed. Sometimes the dishwasher is just used to hold dishes that have been washed an allowed to air dry. I put up a couple clothing lines to air dry some of the clothes. Plasma TV is a personal choice….Black levels are so much better on plasma then on a LED TV. However, TV is off most of the time and people are watching the same satellite signal / internet streams on tablets most of the time.

    Got a funny story about LED lights….The utility company’s power is so volatile that led lights were getting blown out left and right around the house. Imagine a flood light that has half the leds on and then only a quarter within less than a year’s time. Compact fluorescents seem to be able to handle the loads better for some reason. Local laws prevent you from suing for any electrical appliance losses due to the public utility. Microwaves, Refrigerators, Computer, TV all take on unusual loads from the utility company. The worst situation is when the power goes out and then comes back on /off for several pulses. I think the transformers/capacitors don’t get a chance to completely discharge and then gets blasts of power at high and low levels. UPS batteries and Surge/Spike protectors help but still devices manage to get killed.

    My best protection so far has been a device that allows current when it’s within a certain range to remain on and if it drops it remains off for 5 minutes no matter what before resuming the flow of power. Seems like going solar would at a minimum stabilize power, provide a manageable cost that does not grow as fast as our public utility rates and provides backup power when we get weekly/monthly power losses.

    I live in a residential area on a hill where sound seems to echo from miles below. When we are without power for days//weeks after a hurricane the generators drones on for hours on end and some neighbors without generator backup don’t like the sound they hear in their powerless house. Some I think even get agitated and perhaps hostile. Silent power from a battery bank is preferable to the noise and fumes from a neighbor’s diesel generator.

    The cost of electricity in my area almost doubled in 1 years’ time and the local government runs the utility company. Our local power is derived from diesel generators and thusly we pay 52 cents a Kw for power. The quota imposed on grid tie permits may have been exceeded within just 2 years of creating the limits. Feed-In-Tariff was an idea put into law two months ago to slow things down but the reality may be that no more grid-tie is permissible in America’s Paradise. Its now or never where I live.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #10
    Re: Feed-In-Tariff, configuration to maximize sell but not buy
    caribbeandan wrote: »
    A year ago 34KW a month was at the high mark within the last 3 to 4 months 22-24 kw is more often observed. Sometimes the dishwasher is just used to hold dishes that have been washed an allowed to air dry. I put up a couple clothing lines to air dry some of the clothes. Plasma TV is a personal choice….Black levels are so much better on plasma then on a LED TV. However, TV is off most of the time and people are watching the same satellite signal / internet streams on tablets most of the time.

    Yep, it is personal choice always. Depending on your climate (i.e., humidity levels)--Line drying/dehumidification may have their own issues.
    Got a funny story about LED lights….The utility company’s power is so volatile that led lights were getting blown out left and right around the house. Imagine a flood light that has half the leds on and then only a quarter within less than a year’s time. Compact fluorescents seem to be able to handle the loads better for some reason. Local laws prevent you from suing for any electrical appliance losses due to the public utility. Microwaves, Refrigerators, Computer, TV all take on unusual loads from the utility company. The worst situation is when the power goes out and then comes back on /off for several pulses. I think the transformers/capacitors don’t get a chance to completely discharge and then gets blasts of power at high and low levels. UPS batteries and Surge/Spike protectors help but still devices manage to get killed.

    Regarding LED Lamps--There are the original white LEDs that look like standard Tx LEDs... And then there are the LEDs that look like flat chips and are typically mounted to fairly heavy pieces of aluminum.

    In general, the Tx shaped LEDs have very poor thermal dissipation (plastic body, just a couple of thin leads out the bottom). That and the mfg. are pushing a lot of current through them to make them "bright"--Many will will only last ~100-500 hours before they fail (typically they look browned or blackend).

    The flat chip ones are typically better built and should last longer--But before you replace every lamp in your home--I would buy only one or two of any particular type and see how they work over 1+ years first.
    My best protection so far has been a device that allows current when it’s within a certain range to remain on and if it drops it remains off for 5 minutes no matter what before resuming the flow of power. Seems like going solar would at a minimum stabilize power, provide a manageable cost that does not grow as fast as our public utility rates and provides backup power when we get weekly/monthly power losses.

    It sounds like that is your best protection against Utility induced appliance failure (decades ago, our utility would not care if they "browned" us out--low voltage--After paying for replacing a bunch of refrigerators with fried compressor motors--They now have the equipment set up to turn off rather than brown out during partial failures.
    I live in a residential area on a hill where sound seems to echo from miles below. When we are without power for days//weeks after a hurricane the generators drones on for hours on end and some neighbors without generator backup don’t like the sound they hear in their powerless house. Some I think even get agitated and perhaps hostile. Silent power from a battery bank is preferable to the noise and fumes from a neighbor’s diesel generator.

    How will you hear that your system is quiet with all of the noise going on around you. :confused::cry:

    If you set up your system nicely--Perhaps you can eventually convert some of your neighbors--Win - Win situation.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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