Newbie drowning in information needs help planning

MichaelTMichaelT Registered Users Posts: 5 ✭✭
Hello to all and thanks for letting me into your forum.

I live in the UK and the sun and the wind where I live is sporadic at best. I do not intend for the self generation of power to run my home completely but to supplement the power I currently buy from the grid and reduce the monthly bill.
My usage of the generated power needs to be 24VDC (for my project work) and surplus power run into the house at 240VAC.

I am currently drowning in information and my lack of knowledge of hybrid generation is hindering my progress.
What I am hoping to have is a wind generator and solar panel going into a hybrid controller to charge a 24V battery bank with a grid tied inverter from the battery bank going into the house.
It looks fine on paper, but my lack of knowledge does not enable me to know where and what size fuses and switches need to be in the system.

The items I am considering to start with are:
1 off Longi 320W Solar panel
1 off 400W Wind Generator
1 off 20A Hybrid controller (wind & solar inputs)
1 off GTI 600w MPPT (DC11-32V to AC230V Pure Sine Wave Inverter) Grid Tie inverter
2 off 12V 120AH Leisure Battery (SuperBatt DT120)

I have put all the specifications I know below.
Also I do not expect the maximum from the wind turbine or the Solar panels rated output to be anywhere close to its rated values, but this is really a 'starter' project for me to learn from.

Many thanks in advance for your comments and advice.
MichaelT

Wind generator
Rated Power:400W
Rated Voltage:DC27-54V
Battery Voltage:DC12/24V
Start-up Wind Speed:2.5M/S
Rated Wind Speed:10.5M/S
Number of Blades:3
Material of Wind Leaf:Carbon Fiber Composite
Rotor Diameter:1.2m(4')
Rated Speed:800r/min[RPM]
Tower Diameter:>80 mm(3.2")
Tower Height:4.5m-10m(15-33')
Battery Capacity:200AH-400AH
Packing Dimension:687*365*210mm(27"x14.4"x8.3")
Life Span:15 years

Hybrid controller (FWS03/06-12/24)
Battery Rated Voltage:DC12V/24V
Rated Turbine Power:400W/800W
Brake Voltage:14.5V/29V
Turbine Recovery voltage:13.2V/26.4V
Rated panel Power:500W/1000W
Largest Discharging Current:20A
Battery overcharging Protection:16.5V/33V(Turn off Load Output)
Battery Discharging Protection :10.7V/21.4V(Turn off Load Output)
Battery Discharge Recovery Protection:12V/25V(Recover Load Output)
Static Power:15mA

Solar panel (LR6-60HPH-320m)
Peak power Wp: 320W
Voltage at peak power: Vmp:33.9
max open circuit voltage Voc:40.9
current at peak power: 9.43A
max short circuit current Isc:10.02
weight: 16.8 kg
dimensions: 1672 x 991 x 35mm
Product warranty: 12 years
Warranty on output: 25 years

Grid tie inverter
Rated Power : 600W
Solar Panels : ≥600W
DC Input Range : 11-32VDC
MPPT Voltage : 15-22VDC
AC Output : 120V(90-140V) or 230V(190-260V) 50Hz/60Hz(Auto control)
Frequency : 48Hz-62Hz
THD : <5%
Power Factor : >97.5%
Stand-by Power : <1 W
Certification : CE RoHS

Comments

  • BB.BB. Super Moderators, Administrators Posts: 31,464 admin
    Welcome to the forum Michael,

    It sounds like you are trying to do a bunch of different projects at once... Sort of like jumping into the ocean to learn to swim.

    Can we backup a bit and first talk about your power needs/expectation from the system... I like to do a "balanced" system design. First the loads, which define the battery bank. The loads + battery bank (AH and voltage) define the charging system (current, array size, turbine, etc.).

    Once you have the basics--You can start looking at hardware to support those needs.

    If you are purely "off grid"--You can pretty much do what you want. In most places, if you connect to the AC mains and plan on feeding energy (Net Metered power) back to the utility--Then you have a whole bunch of laws/regulations/requirements.

    At least in the USA, it usually does not make much economic sense to go through the GT Solar requirements with a small system... Typically a 3,000-10,000 Watt (guess) array and GT inverter gives you a chance to save money.

    For solar--You need sun. Using London UK, there is not a lot of sun--And very little in winter (and array should not have any shade during 9am-3pm or so):


    London
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 38° angle from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    1.27
     
    2.04
     
    2.76
     
    3.67
     
    4.17
     
    4.20
     
    Jul Aug Sep Oct Nov Dec
    4.25
     
    4.16
     
    3.26
     
    2.41
     
    1.53
     
    1.05
     
    From October through March is not a lot of sun...

    Wind is even more location/site specific... And while turbines are relatively cheap--Adding the costs of a tower (ideally 10+ meters high, and above any nearby obstructions such as trees/building/etc.). Turbines need to be installed in "clean/non-turbulent wind". If there is any upwind obstructions causing turbulence, there is little useful energy to harvest.

    Wind turbines really do no generate much power below ~12 mph / 19 kph... And tend to max out at 25 mph / 40 kph. Pretty windy/miserable conditions. If you are in the middle of a residential area (buildings/trees/etc. everywhere), wind power is pretty much out of the question.

    It sounds like you are starting with a small battery powered system... I would suggest just starting with your battery bank, and an off grid solar charger+array. And a small AC inverter (if you need AC power from the battery bank).

    Just to give you some quick numbers for a "conservative" solar power system:
    • Battery Bank:
    • 120 AH * 24 volts = 2,880 WH of storage
    • 2,800 WH of storage * 25% discharge per day (two days of storage) = 720 WH per day
    • 120 AH * 25% = 30 AH @ 24 volts
    • 720 WH per day * 0.85 AC inverter eff = 612 WH of 230 VAC energy per day
    • 612 WH per day / 5 hours per day load (example) = 122.4 Watt average @ 230 VAC load
    The solar array design... Two calculations. One based on battery AH capacity and 5% to 13% rate of charge. 10%+ suggested for full time off grid/minimum optimum charging:
    • 120 AH * 29.0 volts charging * 1/0.77 panel+controller derating * 0.10 full time off grid rate of charge = 452 Watt array nominal charging rate
    And sizing the array based on your daily loads and average sun... Say you want the power during winter:
    • 612 WH of AC power per day * 1/0.52 off grid AC system eff * 1/1.05 hours of sun per day average (Dec) = 1,121 Watt array December "break even"
    With a 120 AH @ 24 VDC battery bank, I would suggest the maximum AC inverter would be in the range of:
    • 120 AH * 500 Watt * 1/100 AH battery capacity = ~600 Watt max AC inverter for a lead acid battery bank
    None of the above is written in stone--Just some starting points to help size the system and understand the energy capabilities and assumptions that I can see from here.

    Your thoughts?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MichaelTMichaelT Registered Users Posts: 5 ✭✭
    Hi Bill,
    You have hit it on the head
    It sounds like you are starting with a small battery powered system... I would suggest just starting with your battery bank, and an off grid solar charger+array. And a small AC inverter (if you need AC power from the battery bank).
    Completely right.

    Currently I work with 24VDC for a lot of projects and reduce this to 12VDC when needed. This for me works ok and will continue.

    So I thought 'why not use solar', and the idea was born. Reducing from 48VDC to 24VDC and 12VDC seemed an unnecesary step, and boosting 12VDC to 24VDC seemed pointless. So the 24VDC base was settled.

    Solar is unreliable, evenings, night, early morning = no power, hence 2 x 12VDC batteries and sealed batteries, because I do not want perpetual maintenance.

    As I understand it (which may be wrong) batteries do not like being fully discharged so only 20% of the Ah rating can be used without killing the battery, So with a 120Ah battery there is only 24Ah usable, 6 hours @ 4A, which is about the maximum I would use at any one time.

    Then came the problem of possible overcharging the battery so I needed a controller, and I thought, why not feed 'unwanted/unused' power into the house, so onward to the Grid tied inverter. This does not need to be certified in the UK, providing it can have total isolation and you advise the electricity supplier that you will be 'micro generating'. A Grid tied inverter stops supplying power to the grid if there is a power outage.

    Then came, 'if I am feeding power back into the house using unwanted solar, why not use wind as well'. In the UK the cost difference between a solar controller and a Hybrid wind & solar controller is pennies.

    As I live on the top of a hill near the coast (450 ft above sea level), a 12 MPH wind here would be considered  a flat calm day. But even if the wind only blew for 10% of the time, its free energy.

    Regarding the size of the Solar panel, as I am unused to the power generated from this system, and the general opinion of 'you will only get about half of its rated wattage for only a few hours in a day' I picked the single 320W panel expecting to get only 480W in a day. Yes this is just a guess.

    Regards
    MichaelT
  • BB.BB. Super Moderators, Administrators Posts: 31,464 admin
    Lead Acid batteries have their own design "issues"...
    • There are 3 or 4x of Lead Acid designs... SLI (starting, lights, ignition)--Typically discharge to 85% state of charge. There are deep cycle batteries (golf cart, traction, deep cycle--Which for solar are generally cycled down to 75% or 50% state of charge... Forklift usage down to 20% state of charge, but you need to recharge right away). And Marine/Leisure batteries--Which may be "in between" deep cycle and SLI. There are also "float service" batteries... Mostly sit for years (or decades in a telephone office), and are cycled only 10-500 times in their entire life.
    • Lead Acid flooded cell--You check the electrolyte levels once a month or so (add distilled water when needed). And sealed (cannot check water levels--Avoid over charging or they can vent and lose electrolyte.
    • And in the sealed type--there are VRLA (valve regulated lead acid), AGM (absorb glass matt), and GEL ("jellied electrolyte")... The AGM are typically (deep cycle type) are used in solar systems. GEL is a bit "iffy".
    Lead acid batteries have three states of "charging" (more or less):
    • Bulk--As much current as the charge controller can output (typically around 10%-13% but can be higher or lower).
    • Absorb--Battery under charge reaches "charging set point" of around 29.5 volts (see battery manual) and "held" for X hours... For 75% SoC, held for ~2 hours. For 50% state of charge or lower, held at absorb for around 6 hours.
    • Float--Around 27.2 volts where the charger supplies just enough current to keep the battery charged.
    • EQ--Equalize or Corrective charging... Lead Acid 2 volt cells self discharge--And sometimes a couple cells self discharge faster than others--So once a month (or when needed), the battery is "over charged" at around 5% to 2.5% rate of charge for an hour (or more if needed). The full charge cells just gas (and generate heat), and the lower charge series connected cells are brought up to 100% SoC.
    Why talk about this? As you can see, a 50% discharged battery will take (at 10% rate of charge) around 5 hours of charging + ~6 hours of absorb or ~11 hours Under Charge to refill complete. In winter/less sunny areas, there is simply not enough hours of sun in the sky to charge a 50% discharged lead acid battery--It takes several days, or longer to do that... That is why for a battery system that is used every day, suggest 25% discharge... Roughly 2.5 hours charging (10% rate of charge) and 2 hours of absorb for ~4.5 hours Under Charge. If you are not daily using--You can cycle deeper and recharge at 5% (say couple days a week, or weekend system) and let the battery recharge during non-use days.

    There is also the time of use... If you are using power during the day--Solar panel may keep up with usage... If you use at night (such as cabin) and charge during the day--That is what we normally design for here.

    And there is the pretty wide voltage range of a deep cycle battery bank. Nominally, from 10.5 volts (21.0 volts for 24 volt bank) to near 15.0 volts (charging--Or ~30 volts) to ~16+ volts (32 volts) during EQ cycling (or if you are in a freezing climate, lead acid batteries are charged at a higher voltage)...

    So, many times, if you are looking at a 24 VDC device with a 10%+/- input range--The 21.6 to 26.4 volt input range does not map well with a deep cycle battery bank of 21.0 to 32+ VDC of the battery bus... Many times, you may have to use a buck/boost switching power supply/voltage regulator to hold to the requirements of your DUT (device under test).

    Regarding solar panels... They are current sources (not voltage sources like a battery bank). They roughly output Vmp at 25C and can drop Vmp (voltage maximum power) down to ~80% of Vmp on hot/sunny/windless days (in hot climates). You need to "match" the solar panels/solar array for the battery bank voltage and type of charge controller (PWM--Pulse Width Modulated; MPPT--Maximum Power Point Tracking).

    And the Vmp of solar panels are "all over the map" these days... In the olden days, Vmp~17.5 to 19.0 volts or so for charging a 12 volt battery bank with a PWM type charge controller. Your 24 volt bank would need a Vmp-array of ~35-38 volts with a PWM controller to "reliably" recharge a 24 volt battery bank. However, many of the larger format solar panels that are labeled "24 volt" are really Vmp~30 volts; or Vmp~36 volts; or even Vmp>>40 volts.

    Many of these panels are made for Grid Tied AC inverters... Which take 10 or so of these panels in series--So the issue of Vmp=30 or 36 or 40+ volts do not really cause an issue (GT Inverters have MPPT type solar input--Which match the IV curve of the panels to the IV curve of the "load").

    For 24 volt system--If you get the cheap and plentiful Vmp~30 volt panels--One panel is not enough to charge a 24 volt battery bank... And two in series on a "cheap" PWM controller wastes almost 1/2 of the solar panel's Wattage. You can put two panels in series for a MPPT controller (need to match controller specifications)--And they will work very well--However MPPT controllers are more expensive (and usually have more bells and whistles).

    When we talk about Hours of Sun per day... That is 1,000 Watts/sq meter of full noontime sun... That "1 hour" of sun in december is spread out over a 1/2 dozen hours of sun arcing across the sky--So, you are right that the output current of the solar panel (at ~Vmp) starts out a zero, peaks to near rated value (may be 50% of rated value on a December/hazy day) and back down to zero....

    There are other types of batteries. The LiFePO4 (lithium Iron Phosphate) batteries are very popular for solar power systems--Lightweight, can charge very quickly (no absorb cycle, and higher charging current). However they are expensive and usually need a battery monitor system (BMS) to keep the cells in the operating voltage range (Li Ion batteries have very short life if over charged or over discharged).

    Anyway... A little more information. And some of the issues that we see.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MichaelTMichaelT Registered Users Posts: 5 ✭✭
    Many thanks for your outstanding information Bill, but it brings me back to my original problem - drowning in information.

    A lot of companies would like to sell me their own wind generator & solar panels with a controller and battery bank for anything between £350 to £1400 depending on the number of solar panels. With outputs of 600W to 1400W Eco-worthy for example but when I spoke to them, they sounded less informed about their own products than my cat.
    It did not inspire confidence at all.
    The simplest was 2 100W panels and a 400W turbine and a hybrid controller. Then the number of panels and quantity of batteries increased with the price.
    (https://www.ebay.co.uk/itm/1400W-1000W-600W-Hybrid-System-Kit-400W-Wind-Generators-100W-Mono-Solar-Panel/124284077044?hash=item1cefe883f4:g:-fEAAOSwm8FfH~5b)

    With that pre-bought package I could just add a Grid tie inverter and an isolation switch to it and use any excess power in the house without any problems.

    I could even buy an off the shelf 500W plug-in solar system that contains its own micro-inverters and plug it straight into the house.
    (https://www.pluginsolar.co.uk/?product=plug-in-solar-duo-500w-ground-mount-kit-2)

    My apologies if I am seeming a but dense, but I have taken this 'eco-worthy designed package' removed the 2 x 100W panels and put a 320W panel in its place to maybe get a little extra power for using half the roof space and changed the batteries from 20Ah to 120Ah.

    My thoughts were to 'see' what the system produced, total cost £575 which included the Grid tie inverter, is to all practical aspects, pocket money.

    Throwing £4000 to £15000 for a monstrous professionally installed system for something which I did not understand and may not do what I want,  is just not going to happen.
    Similarly, me going out and buying 10 panels (£880) and fitting them to the roof with all the commercially produced boxes (cost unknown) in the appropriate places is not going to happen either.
    ----------------------
    Having read a veritable mountain of often conflicting information on 60/120 vs 72/144 cells, Bifacial or single, poly vs mono, bypass diodes, blocking diodes, wet vs dry, Li vs Pb, float/absorb/charge, overvoltage/undervoltage, slip rings, brushless, single vs double ball race mounting bearings, etc etc etc.

    In my ignorance I thought that by putting the specifications of what I was considering to purchase as an embryo system would guide me to put the fusing and switches in the correct place and the correct size and maybe to change a component to something better.

    If it works and produces power, fine and good. If it doesn't, at least I have learnt from it and know what not to do.

    Regards
    MichaelT

  • BB.BB. Super Moderators, Administrators Posts: 31,464 admin
    Michael,

    Part of the confusion (for me) is that you have different requirements and expectations... Lets look at Grid Tied solar first.

    I know zero about electricity billing for you... But from what little I could quickly find... Average electric bill is around 8-10 kWH per day. And an average of something like a £105 bill per month. And around £0.15 per kWH.

    I don't know if the £105 per month bill is energy usage + service charge--Or if there is a natural gas component too.

    Anyway: £0.15/kWH * 10 kWH per day * 30 days per month = £45 per month electrical "energy" part of the bill (£60 per month connection fees?)

    If you have a 320 Watt solar panel, mounted at 38 degrees from vertical--December is 1.05 hours per day of sun, and July is 4.25 hours of sun per day. The typical monthly harvest would be worth:
    • 0.320 kWatt * 0.77 panel+controller deratings * 1.05 hours of sun per day * 30 days * £0.15 / kWH = £1.16 per average December
    • 0.320 kWatt * 0.77 panel+controller deratings * 4.25 hours of sun per day * 30 days * £0.15 / kWH = £4.71 per average July
    Anyway--A guess at your power £ savings from a 320 Watt solar GT system...

    When you start adding batteries + charge controllers + etc... The losses do tend to cumulate. For example, the July energy harvest for GT vs a full off grid solar power system with an off grid AC inverter:
    • 320 Watt panel * 0.81 panel derating * 0.95 GT inverter eff * 4.25 average hours of sun = 1,046 WH per day July (1.046 kWH per day) from a full GT system
    • GT efficiencies combined = 0.81 panels * 0.95 GT inverter = 0.77 overall GT efficiency
    • 320 Watt panel * 0.81 panel derating * 0.95 charge controller derate * 0.80 flooded cell lead acid battery eff * 0.85 AC inverter eff = 712 WH per day off grid AC system July typical
    • Off GRid efficiency combined = 0.81 * 0.95 * 0.80 * 0.85 = 0.52 overall OG efficiency
    So--If you add a battery to a GT Inverter system--You lose about another 20% for FLA battery losses (and expenses of "cycling" a battery, float charging , etc.)...

    If your average amount of sun is ~2.9 hours per year (did a quick average of the above monthy numbers), then the yearly GT harvest would be:
    • 0.500 Watt GT kit * 0.77 average GT derating * 2.9 hours of sun * 365 days a year * £0.15 / kWH = £61.13 per year est. savings
    • £750 for kit (plus labor value?) / £61.13 yearly harvest = 12.3 years to "break even"
    GT system usually have little maintenance (you might need a new GT inverter every 10+ years)--And the cost of power seems to be increasing pretty quickly...

    I may be totally wrong about your billing rates and fees... But the math is there for your to do your own calculations with the correct numbers.
    4
    You can switch the 500 Watt array from GT to your battery charger when needed... Or just get an efficient "charger/float charger" that is mains powered too...

    There can be complexities with adding a GT inverter (or hybrid GT/OG inverter) to a battery system... Programing charging/GT harvest set points can be a bit confusing--And there is always the possibility of discharging the battery bank to "dead" (failure) if the charging/GT settings are not done correctly or if something "goes wrong".

    In the USA--Fully turnkey installed (and permitted) systems can be USD$5 / Watt installed (or $5,000 per kW of array) or less ($3 per watt??).

    For example, if your home uses (on average) 10 kWH per day or 300 kWH per month with 2.9 hours of average sun, the array/system would be something like:
    • 10 kWH per day * 1/0.77 GT inverter eff * 1/2.9 hours per day = 4.48 kW array
    • 4,480 Watt system * $5 per Watt installed = $22,400 installed (or less--guesstimate)
    You do run into billing/rate plan issues... There are yearly "true up" plans (you endeavor to have zero kWH bought/sold over 1 year period) and there are 1 month month true ups... The 1 year plan is good because you can bank "summer" excess harvest for use in the winter (little sun).

    The first system you install--lots of confusion about components and code/electrical requirements... The second system is much easier.  :smile:

    With wind--A "good system" probably does harvest around 10% to 15% of "rated" wind turbine power... But there are so many variables as to make even that a wild guess.
    • 400 Watt turbine * 24 hours per day * 365 days a year * 0.10 harvest factor = 350,400 WH per year = ~350 kWH per year
    • 350,400 WH per year / 365 days per year = 960 WH per day (guess)
    • 960 WH per day * 0.95 GT inverter eff = 912 WH per day (yearly average) feed to grid
    • 400 Watt solar array * 0.77 GT system eff * 2.9 hours of sun (year average) = 893 Watt*Hours per day GT harvest (daily average)
    Are the above wind turbine numbers accurate? I cannot say other than they are a best guess (assuming everything works correctly).

    We have had lots of people come by here and ask why their wind turbine is not generating power--And it is difficult for us to really "fix" the problem. Don't know if site/turbulence problems, wrong blades, tower too short, problems with electronics (charge controllers/GT inverters), etc. And have they done their maintenance greasing bearings, slip rings working, damage from weather, etc....

    Solar panel + racking + GT inverter --- Little to no maintenance. Wind turbine yearly (?) maintenance (take down, grease, paint, repair, check brakes/furling/etc.).

    Personally, I am not a fan of small wind.... If you ever wanted to build your own turbine--These are one of the DYI (do it yourself) projects that many times work better than off the shelf products.

    I have some links (now ~10 years old) that talk about turbines and what works and what does not.

    Wind Power Links
    www.otherpower.com (good forum for DIY Wind Power)
    Hugh Piggott - Scoraig Wind Electric site for tons of info (from mike90045)
    Scoraig Wind "Recipe Book" for DYI Turbines (from Chris Olson... From his 4/11/2013 post)
    www.greenpowertalk.org (added from "russ"--Like here but more wind/less solar)
    Small windpower a scam ? Survey says SO
    Truth About Skystream & SWWP
    Windmax HY-2000 2kW Wind Turbine (apparently, some vendors don't sell spare parts--just new turbines. However, the owner, Edward has been very happy with its performance from 2010-2012--BB. 5/31/2012)

    The "small windpower a scam" is a link to an older study of small wind turbines and how well they worked (or did not) in "average wind" conditions.

    If you had any neighbors that have installed wind turbine(s), I would talk with them and see if they have monthly harvest numbers you can review.

    For example, here is a monthly harvest chart from a relatively good (and larger) Skystream system in a windy zone near Lake Erie/Ohio as I recall (note, there were many component and mechanical issues that resulted in lost harvest):

    The old "Jane Skystream" data got hosed again in the archive... A copy I recovered:

    It looks like the forum conversion lost Jane's monthly data (only long term, small wind, installation performance numbers I have heard). Very important historical information (In my humble opinion):


    JAN
    FEB
    MAR
    APR
    MAY
    JUN
    JUL
    AUG
    SEP
    OCT
    NOV
    DEC
    Total
    2007
    n/a
    n/a
    n/a
    n/a
    n/a
    n/a
    n/a
    n/a
    n/a
    175
    225
    0*
    400
    2008
    98*
    292
    308
    246
    228
    153
    9284
    97164
    2464722,480
    2009
    265348244371182869084250100194131*2,345
    2010
    101130










    * December, 2007 - Skystream shut down from software problem with cold and would not restart.

    * January, 2008 - Skystream down until the 27th. Produce 98kWh in the 5 days remaining in the month.

    * December, 2009 - Skystream shut down several times and would not restart on it's own, production very low for wind speeds.

    * January, 2010 - Production very low for wind speeds.

    * February, 2010 - Production very low for wind speeds.

    At least solar is much more predictable (if poor in winter/cloudy weather).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 31,464 admin
    Regarding: Having read a veritable mountain of often conflicting information on 60/120 vs 72/144 cells, Bifacial or single, poly vs mono, bypass diodes, blocking diodes, wet vs dry, Li vs Pb, float/absorb/charge, overvoltage/undervoltage, slip rings, brushless, single vs double ball race mounting bearings, etc etc etc.

    Regarding the number of cells... Each solar cell produces around Vmp~0.5 volts per cell (Voltage Maximum Power)... You put a bunch of cells in series to get the Vmp-array operating voltage (under standard test conditions).

    More or less, to charge a 24 volt battery bank, you need ~72 cells (for Vmp~36 volts) for charging a 24 volt battery bank with a PWM (simple on/off pulse width modulation) solar charge controller. This is the "most efficient" voltage matching... You can go higher Vmp-array with a PWM controller, but you gain little. The battery charges at ~29.5 volts nominal -- A higher voltage array adds "nothing" (power=Voltage*Current into the battery bank).

    In terms of electrical design--Running at higher voltages allows the use of smaller wiring/bus bars/etc. Saving the costs of expensive copper.

    So, for GT Solar systems--Low cost panels (higher voltage) and fewer components (few but large panels, fewer electrical connections, fewer bolts to hold the panels down, etc.).... Also remember that losses due to heat are Power=Current^2*R... So if you double the current with the same size wire (resistance), you have 4x more losses.

    More or less, look at the panel wattage and physical sizes you want. And you also have to look at their Vmp/Imp ratings for your solar array (again, a PWM controller needs around Vmp-array~36 volts... And a "typical" MPPT controller needs a Vmp-array of ~40-100 VDC (MPPT controllers can efficiently take high voltage/low current and down convert to low voltage/high current for the battery bank).

    You probably will have to make multiple paper designs to find the most cost effective design for your needs.

    Mono crystalline panels are more efficient--So you can have a slightly smaller physical array, or more harvest from a limited space for the array. Some people like the "solid" color of mono crystalline panels vs the "blue fractured" pattern of poly crystalline panels.

    Bypass diodes are installed inside most solar panels... The diodes will "bypass" ever 18 cells or so. This is because "dark cell" (shading) go "high resistance" and stop all current flow. The bypass does allow current to bypass shaded cells, and also prevent cell damage in high voltage arrays (dark cells are damaged by ~12 to 24 volts of "reverse voltage").

    Blocking diodes were used in older systems that did not have charge controllers... At night, a solar panel connected directly to a battery bank will slowly leak current backwards and discharge the battery bank over time. I believe blocking diodes were also use instead of fuses and paralleling strings of panels (fuses would blow if a panel was shorted--Blocking diodes prevented reverse current flow to shorts). Pretty much these days, blocking diodes are not used/needed.

    Wet vs Dry (charged lead acid batteries?). Many flooded cell lead acid batteries are shipped "dry charged". They will keep upwards of 18 months after manufacturing and are generally filled at the battery distribution point for sale/installation. Lead Acid batteries start self discharging/aging when filled (with ~1.265 or so specific gravity electrolyte).

    Li Ion vs Lead Acid... There are lots of variations in Li Ion chemistries... The high power Li Ion batteries tend to be much more picking regarding operating voltages and currents... If their specs are violated, the cells can split open and each catch fire (with some very toxic end products--As in very toxic/long term health/death stuff).

    The Li Ion cells we generally talk about here are LiFePO4 or similar... They are a reasonably light/compact/good performance battery--And while they can be easily damaged if over charge (too high of voltage, too high of current) or over discharged (too low of voltage per cell, too high of discharge current)--They generally fail "safely" (without fire).

    There are different charger control types for charging lead acid (and other) batteries... The typical solar power system has 4 modes:
    • Bulk: charging below 29.5 volts -- Maximum available charger current (generally 5% to 20% or so rate of charge... 5% of 100 AH battery is 5 amps charging).
    • Absorb: charge controller holds the battery at 29.5 volts for 2-6 hours (or other termination methods). Once battery is >90% state of charge, then absorb is terminated.
    • Float: "holding the battery" at ~27.2 volts once the battery is charged... Just high enough voltage to prevent self discharge. Just low enough to prevent "gassing" or other over charging damage to the battery cells
    • EQ: Equalize charging... Done once a month or so (typically). Selective over charging of battery to gas/bubble and mix the electrolyte and bring low cells to 100% State of charge. Typically charged at 30-32 volts for an hour or a few hours once a month. Mostly done to flooded cell batteries (not AGM, not GEL, etc.).
    Note: Always start with the battery manufacturer's recommendations--The above voltages are typical, but may not be right for your battery.

    Slip rings are typically used on wind turbines so that when the point different directions in the wind, the slip rings and brushes bring power from the Turbine Nacelle to the tower (around yaw bearings). There are other ways of bringing power down too....

    Wind turbines are "alternators". A rotor with a magnetic field rotates inside fixed coils of wire (stator) to generate AC power... Slip rings can be used to bring current to the rotor to generate a magnetic field (typical for car alternators). Or they can use permanent magnets for the magnetic fields (more efficient, no slip rings to wear out). Each has its pluses and minuses.

    Bearings--Well, that is the most complex machined part in a typical small wind turbine. Bearings need grease, and they are subjected to bending forces from the turbine blades, wind gusts, etc. The better the bearings, the longer the service life (at least one hopes).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,251 ✭✭✭✭✭
      if your utility is ok with you generating power, and it's simple to get the permission from the town and utility,
    I am in favor of just simple grid tied solar.   What you produce, you consume at the house, and extra power you don't use
    can either be "lost" or sold to the utility to unwind your meter - depending on the utility regulations

    If you are not off-grid and don't have a pressing need for power all the time, I would skip the batteries, their losses, and expense

    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • MichaelTMichaelT Registered Users Posts: 5 ✭✭

    Thank you Bill for your input and all the information and thank you Mike95490 who summed it up in one line.
    mike95490 said:
     
    If you are not off-grid and don't have a pressing need for power all the time, I would skip the batteries, their losses, and expense

    It does seem disproportional with the amount of 'use this instead of that', 'this needs to match that', 'this is better than that unless', and so on, to any possible benefits that I may or may not get from it.

    Solar and wind generation maybe good if you have bright sunshine (which I don't) for a specific amount of time per day, you have a constant and pre-recorded  amount of wind (which I don't have) and that you know the maximum amount of power that you are going to use (which I don't).

    So this idea of wind & solar power self generation with the items I previously listed to reduce utility costs is now scrapped.

    What I am going to do is just purchase a 500W off the shelf system that has Emphase Micro inverters and just plug it into the house and see what changes to the electricity utility bill it makes over the next year. If it reduces the bill, then great. If it doesn't, then ~shrugs~ I am out my pocket money for the next month, neither of which I am going to burst into tears over.

    Again many thanks for your help and the information that you have given me.

    Kind regards to all
    MichaelT


  • BB.BB. Super Moderators, Administrators Posts: 31,464 admin
    Good luck Michael...

    The main things to be careful about are wind/snow/lightning...

    The panel(s) need to be securely mounted (don't want them being knocked or blown off the roof, leaking from mountings or causing ice dams on roof) and have at least some lightning/grounding protection if you are in a lightning prone area (don't want to bring lightning energy into your home/electrical system). (depending on your specific construction and weather conditions).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • solar_davesolar_dave Solar Expert Posts: 2,380 ✭✭✭✭
    MichaelT said:


    What I am going to do is just purchase a 500W off the shelf system that has Emphase Micro inverters and just plug it into the house and see what changes to the electricity utility bill it makes over the next year. If it reduces the bill, then great. If it doesn't, then ~shrugs~ I am out my pocket money for the next month, neither of which I am going to burst into tears over.



    Well If your hooking into the grid I suspect there are regulations for the attachment. Just plugging it in to an existing outlet is a dangerous proposition. I understand that the UK uses some type of ring wiring, please be aware that adding 500 watts to an exiting circuit may overload that wiring without proper fused protection (you can draw upto the breaker rating plus the 500 watts which might be over the wire carrying capacity). . Here in the US it is usually required to have a dedicated circuit in the breaker panel to take the solar energy and distribute it to the loads.
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,812 ✭✭✭✭✭
    Hey Dave ! Staying warm down there!

    I would add to your caution that if the OP has insurance on his home. What he does with this could run all the way up to a fire with insurance denying the claim. Probably will not happen but we have seen the YouTubes.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • solar_davesolar_dave Solar Expert Posts: 2,380 ✭✭✭✭
    Hey Dave ! Staying warm down there!

    I would add to your caution that if the OP has insurance on his home. What he does with this could run all the way up to a fire with insurance denying the claim. Probably will not happen but we have seen the YouTubes.
    Nice today, T-shirt weather, going to the mid 70's this week. Not seen a frost this year so far.

    Good catch on the insurance as well. One might also think that adding 500 watts is good, why not 1000 or 2000 ...
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,812 ✭✭✭✭✭
    Fires are nasty! Still running the Leaf's ?  Last few days on my google below.
    https://photos.app.goo.gl/5cb1FzLkAa22UGpB8
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • BB.BB. Super Moderators, Administrators Posts: 31,464 admin
    From Michael's link to the 500 Watt GT plug-in system (UK):

    https://www.pluginsolar.co.uk/?product=plug-in-solar-duo-500w-ground-mount-kit-2)

    Plug-In Solar is a Do It Yourself (DIY) Grid-Tied solar power system, which allows you to generate FREE electricity to power your appliances. Plug-In Solar kits include ALL the equipment you need to start saving money on your electricity bills, WITHOUT the need for government incentives.  No need for an EPC inspection, MCS Certification or The Smart Export Guarantee (SEG) Tariff.

    Installations under 800W are exempt from G98 commissioning, so you can simply install this kit without any DNO paperwork.  More details on this exemption can be found here: ENA G98 Regulations.

    Are Plug-In Solar kits easy to install?
    Installing a Plug-In Solar kit requires NO experience, and is a simple plug and play assembly. You don’t need to be a qualified electrician, just a ‘skilled person’ [1].  You can install your Plug-In Solar kit in the GARDEN, on the PATIOSHEDPERGOLAWORKSHOPGARAGESTABLE, BEACH HUT, SUMMER HOUSE, OFFICE or HOUSE roof. Anywhere with a mains grid connection. It’s up to you.

    So--It could be perfectly legal.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MichaelTMichaelT Registered Users Posts: 5 ✭✭
    Thanks Bill for reading my posts. That is why my original idea was 720W max.
    I have also notified the utility provider that I will be micro generating and they said the only reason that they need notifying is that the energy consumption would be less than normal for the property so they would be aware that it is not electricity theft.
    MichaelT

  • mike95490mike95490 Solar Expert Posts: 9,251 ✭✭✭✭✭
    MichaelT said:

    ......
    What I am going to do is just purchase a 500W off the shelf system that has Emphase Micro inverters and just plug it into the house and see what changes to the electricity utility bill it makes over the next year. If it reduces the bill, then great. If it doesn't, then ~shrugs~ I am out my pocket money for the next month, neither of which I am going to burst into tears over...................

    500W of PV x 4 hrs a day =2kwh  or about 50 cents.  Or $15 a month, under perfect conditions
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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