Newbe

Greetings from Gina in SC,

The mission in British Guyana (South America) wants me to set them up with solar systems in each of their buildings. This is a boarding school with about 4 buildings. And there is a new school down the river that also wants solar power. Someone brought a single solar panel, battery, etc a couple years ago and they love it - just not enough power. They spend a lot of money each night to run a diesel generator for a couple hours.

I have not bought anything yet. I plan to make my own solar panels to save money as well as putting them together on site. I am reading everything I can so I buy the right things. I purchased "earth4energy" web book. I found some solar supplies at Northern Tool near my work. I am looking at solar cells from "plastecs.com".

I plan to make a couple panels at home and hook this up before I head to South America so I know what I'm doing. I have been studying sizes and brands of batteries, controllers, inverter, meter. Wow.

I can use all the advise you are willing to give. vjmjacko@charter.net

Gina

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Re: Newbe

    Gina,

    Your heart is in the right place--but make sure you work out the costs and understand the needs, in detail, of your friends in British Guyana...

    First, unless there is something really special in your needs (such as setting up a local solar panel mfg. site with proper supplies and processes)--I would humbly suggest that building your own panels (over a few watts) is not cost effective, will not generate as much power as you think, and will probably fail in a short time (months or a couple years).

    Regarding Earth4Energy--I don't have any of their products, but I would suggest that you verify everything you read in their book with real world numbers before you spend any money trying to replicate their "projects". You might take a look at this two threads:

    Earth4Energy - DIY Panels
    Scam Alerts

    Again, I have no product or contact with Earth4Energy--just no confidence in what they promote even comes close to their claims. As a home science project--go for it.

    Off-Grid Solar power is expensive--no matter how you cut it... You are going to pay $3-$5+ per watt for good solar panels (20-25 year guarantee). And $10+ per watt for smaller solar panels with a few year warranty--such as those on plastics.com...

    Bare cells from Plastics.com, you are looking at:
    Brand New Cell only 1000 left sold in lots of 50 and 100 only
    .55 Volt at 2.3 AMPS 3x6 inch approximately 1.5 Watts
    $2.70 each $10 shipping in US Look at Solar Cell page for sale items on Solar cells
    ALSO 62mmx125mm solar cell .55 volts at 1.5 amps $2.40 each
    $2.70/1.5watts = $1.80 per watt

    And you will probably be lucky if you get 50% of their rated output because you will not have the correct low iron glass and issues with trying to get everything clean and sealed against weather. Also, you will probably break/damage quite a few of the cells trying to solder and mount them--some of the newer cells are almost paper thin (silicon is not cheap--get more cells per lb of silicon) and very easy to break (or very difficult not to break).

    Plus, good solar panels are made with tempered glass--both stronger against hail/windblown derbies and if broken--will shatter into small, safe, "pebbles".

    Lastly, I would suggest understanding their current requirements... A "small" diesel generator can output 5kWatts or more---that is 10kWatt*hours (assuming 2 hour run-time--if operating at full load)... A similar solar system would cost somewhere in the neighborhood of $15,000 to $30,000 to replace the genset.

    It is possible that the generator is over-sized for their needs (generators typically use almost as much fuel at 0-50% load vs running at 50% load). The may reduce their fuel use dramatically by installing a properly sized generator. And, if they need small amounts of power during the day / off-peak hours -- people have made "hybrid" power systems. Install a battery bank to manage the small loads during the day, and run the genset for lots of power during the night, and charging the batteries for use the next day. That way, the genset spends most if its time generating power at its most efficient loading/fuel use.

    Anyway--there is a lot to consider here--and I will stop typing for now.

    If you can supply more information on the power needs of the facilities--hopefully we can help with some suggestions one how best to proceed.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Newbe

    Step One: FIGURE OUT WHAT YOUR POWER REQUIREMENTS ARE!

    There's no sense shopping for anything until you know how many kilowatt/hours per day you're going to need to supply.
    If they currently use a generator than obviously you're after 120/240 VAC and will need an inverter. Don't size it according to the generator's output, as it probably produces considerably more than is necessary. To size it properly you need to know what the maximum current usage at any one time will be. From that you can determine how many amp/hrs of batteries you'll need (times at least 2, so they don't get drawn past 50% discharge). The battery rating will tell you how much you need in panels to provide a charge rate of 5-10% and what sort of controller to get to handle it (inevitably an MPPT type).
    Keep in mind you have to factor in the inefficiencies in panel output, line loss, et cetera. Also know in advance that this stuff is expensive: an inverter set-up will cost anywhere from $8,000 to $25,000 easily.

    But you must know your power requirements first.
  • Moe
    Moe Solar Expert Posts: 60 ✭✭
    Re: Newbe

    From what I read of Guyana, there is both split 120/240 and 230 single phase, as well as both 50 and 60 cycle power. The absolute first information you need is what the power at the mission is in volts and frequency. The inverter and battery charger selected are dependent on this. The existing generator will be needed to top off the batteries when solar gets behind.

    As said above, you need to know what the power requirements are. For example if there are 4 rooms in each of the 4 buildings and each room burns a 60 watt bulb for 2 hours each night, you need 4 x 4 x 60 = 960 watts of power x 2 hours = 1,920 watt-hours of cumulative energy each night.

    You need to conserve first. If the hypothetical 60 watt incandescent bulb in each room is replaced with a 13 watt compact fluorescent, you've just cut the cost of your required solar system by 75%, not to mention the savings of bulb replacement down the road. When you're looking at a $10,000+ system, that $7,500+ savings is REAL money!

    Hopefully, BB and the others have convinced you manufacturing your own solar panels is a really bad idea, and uneconomical in the long run.
  • System2
    System2 Posts: 6,290 admin
    Re: Newbe

    Greetings again from Gina in SC

    Thanks to each of you that offered your advice for setting up the mission in British Guyana with solar power.

    Kimbia Academy(Davis Indians) is 70 miles through the bush from Georgetown, Guyana and about 9 hours via Berbice River/boat. There is no formal power for quite a distance. They are using a 10k diesel generator but would like to use it for backup only and go with solar power. (The diesel is expensive and they don't charge the kids tuition-just food as it is run on donations) The house that has the one solar panel has regular outlets but one plugin goes to the generator and the other to the solar panel system. They have plenty of sunshine. I can buy a deep cycle battery in Georgetown, Guyana for $150-they didn't seem to know much about the battery. I need to bring an inverter (they recommended a 700 watt) and the regulator (don't know the size) with me. I'm a little confused about the panel boxes. Apparently the science building has a panel box but not sure what I will find in the other buildings. I would like to keep my costs to $1,000 or so per setup.


    I plan to go down with one setup at a time and learn as I go. They would like solar power for 5 buildings - each a separate setup. The classroom is the biggest with 12 lights (new 16w bulbs). There are also 4 labtop computers and 1 regular computer. There are 2 TVs set up with power point and DVD. These don't need all run at the same time.

    There are 2 dorms -both the same size with 7 lights and 3 labtops and 1 harddrive computer.

    The kitchen has 7 lights. They use wood to cook and bake with but I would think a couple outlets for kitchen appliances would be nice.

    The science building has 7 lights and they hope to move the computer room in there someday with 4 labtops and 1 harddrive.

    I will need ?roof mounts, wire, inverter, and regulator (is that the same as a charge controller?). ??? I'm having second thoughts about making the solar panels and will price already made panels. I will keep watching this site for your advice. Many thanks. Gina
  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Re: Newbe

    First thing... If the buildings are close enough you can run a power line from a central power site--then I would do this with a central solar generator... Basically, your usage, if you average all of your loads together and take it from a central source, will be more efficient than 5 different collection points... If one building needs to use more one day (PC and projector), it cannot "borrow" from the other four buildings that may use less that day. Also, typically, large panels, large batteries, and large inverter(s) are, many times, more cost effective than a bunch of smaller installations. Down side is that you end up buying a bunch of expensive stuff all at once.

    I would only go with "distributed" solar if the power usage is really low (maybe less than 100 watt*hours of load). You could do this with a 50-100watt panels, single charge controller, and a smallish battery.

    When you total up your loads--you are talking about a relatively large amount of power... As an example (numbers are sort of made-up, but close enough to at least scale your solution):

    Class Room:
    12*16watts*8hours=192 watts, 1,536 watt*hours (lights)
    4*40watt*8hours=160 watts, 1,280 watt*hours (laptops)
    1*250watt*8hours=250 watts, 2,000 watt*hours (desktop)
    2*160watt*2hours=360 watts, 720 watt*hours (TV's)
    2*4watt*2hours=80 watts, 160 watt*hours (dvd players)
    ===========================================
    1,042 watts (if everything on at once), 5,696 watt*hours per day

    dorm 1
    7*16watt*4hours=112 watts, 448 watt*hours
    3*40watt*8hours=120 watts, 960 watt*hours (laptops)
    1*250watt*8hours=250 watts, 2,000 watt*hours (desktop)
    ============================================
    482 watts peak, 3,400 watt*hours

    dorm 2
    7*16watt*4hours=112 watts, 448 watt*hours
    3*40watt*8hours=120 watts, 960 watt*hours (laptops)
    1*250watt*8hours=250 watts, 2,000 watt*hours (desktop)
    ============================================
    482 watts peak, 3,400 watt*hours

    kitchen
    7*16watt*4hours=112 watts, 448 watt*hours
    appliances is a big ????... Right now, is small system
    ===================================
    112 watts, 448 watt*hours--small system if no appliances

    Science
    7*16watt*4hours=112 watts, 448 watt*hours
    4*40watt*8hours=160 watts, 1,280 watt*hours (laptops)
    1*250watt*8hours=250 watts, 2,000 watt*hours (desktop)
    ============================================
    522 watts, 3,728 Watt*hours per day...

    Personally, if you are trying to do something quickly and be helpful--I would attempt to address the needs of the kitchen first... It is small, and relatively a known quantity (at least from 8,000 miles away).

    You would need a smallish (say 300 watt) true sine wave inverter (you could use a modified sine wave inverter--but for a permanent installation--TSW should be more reliable and trouble free for things plugged in). Might use a 24 volt input inverter--to size for solar charge controller requirements (further down post)

    And you could get away with a 12 volt battery, assume 85% efficient inverter running at 12 volts:

    112watts*1/85%eff/12v=11 amps from battery or ~5.5 amps from a 24 volt battery (use 24 volts for rest of post)

    Battery size... Assume lead acid, 50% maximum discharge, and 3 days of "no sun" (gives good battery life)...:

    448 Watt*Hours * (1/0.85 inv eff) * (1/24v) * 3 days * (1/50%) = 137 amp*hour of 24 volt battery bank (at 20 hour rating)

    But, if you use a 24 volt battery bank (2x12volt or 4x6 volt), then you can use 137AH/2=two 69 amp 12 volt batteries in series, or four 35 amp*hour 6 volt batteries in series, etc...

    Minimum panel size... Assume an average of 4 hours of sun per day (from solar isolation charts like this) and assume at least 3 hours of sun during bad weather season (whenever that is)...:

    448 watt*hours * (1/3 hours sun per day) * (1/0.80 batt eff) * (1/0.85 inv eff) * (1/0.77 solar pnl eff)=285 watts of solar panel required.

    1 solar charge controller--if you get solar panels with Vmp>24 volts, you can use this very nice MPPT Solar Charge Controller:

    wind-sun_2031_1362431Morningstar SunSaver MPPT Solar Charge Controller
    The worlds most efficient small solar charge controller
    Regular price: $278.00
    Sale price: $233.75

    You can read through our host's online store for inverter, solar panels, and fuses/breakers, wiring and such...

    Mounting the solar panel nees full sun all day long, winter/summer (near equator--not as big of deal as north/south latitudes.

    Panels can be mounted on ground, or on roof--which ever is more secure (against wind/storms, people, animals, etc.).

    Solar panels will cost you around $5 per watt (plus very expensive shipping)--close to $1,500 or more... wiring, batteries, fuse/breaker, switch to turn inverter on/off won't cost that much more...

    And, I would highly suggest a battery monitor--both to properly monitor the batteries (so they don't get under charged and damaged/short life).

    For low cost and good function:

    wind-sun_2032_3405420Trimetric TM2020 Battery Monitor System
    Shows state of charge and other information about deep cycle battery sytems
    Regular price: $179.00
    Sale price: $140.00

    The very nice family of Battery Monitor (plus programmable alarm if batteries are over drained):

    wind-sun_2030_577114Xantrex Battery Monitors & Accessories

    The above will give you a good idea of the basics and you can ask more questions as they arise.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Moe
    Moe Solar Expert Posts: 60 ✭✭
    Re: Newbe

    You sure got carried away with the requirements there BB! As it is, they're currently only running the generator "a couple hours a day." And should you recommend a pricey MPPT controller for this application, especially in a tropical environment?
  • System2
    System2 Posts: 6,290 admin
    Re: Newbe

    To Bill from Gina in SC

    THANKS FOR THE INFO. The missionaries running this school have apparently had something go out on their little one solar panel system and it knocked the system out for 2-4 weeks -until they could get to Georgetown to get parts and don't want everything to go down for weeks-so want independant systems. Sure would be cheaper to have the different buildings connected. Unsure about this. MANY THANKS. Gina
  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Re: Newbe
    Moe wrote: »
    You sure got carried away with the requirements there BB! As it is, they're currently only running the generator "a couple hours a day." And should you recommend a pricey MPPT controller for this application, especially in a tropical environment?

    Moe,

    As I said, just took a stab at their power requirements--I am not there, and I have no idea how much they really need or are currently using.

    I would suggest that Gina setup a spread sheet (along the lines of my earlier post) to begin understanding the needs and options (lights only at night, computers during the day, getting very low power computers/servers vs what may be there right now, use the generator when the loads are "high" (say evening computer classes, TV use, and kitchen tools) and use the battery/inverter system when/where the loads are low (lighting, radio) (may not even want solar panels at all for first installation--use genset to charge batteries for off peak usage).

    The reason for suggesting the "pricey MPPT controller" is because, for a small unit, it has very useful monitoring functions (that could be used to plan out the ability to generate power for the rest of the facility)--And, it gives many more useful options for solar panels (series or parallel of smaller or larger panels, and the ability to install the panels farther from the battery bank for better sun and less voltage drop and/or smaller/cheaper wire for the DC cables from the panels to the charge controller / battery bank). The higher voltage series can help over come the effects of high temperatures (which can depress Vmp of the panels to below that required properly equalize the batteries). And, depending on if they choose a 12 or 24 volt system, they can just throw a switch (and still have the higher voltage panels used efficiently). And, lastly, many times the higher voltage panels intended for Grid Tied Inverter operation (typically >100 watts) with non-standard panels that are not12/24 volt Vmp can be cheaper ($$$/watt) than the "appropriate" 12/24 volt panels.

    In the end, this is just a suggested starting point... If the appropriate panels are found, and can use a PWM controller (which cost ~$100 less) and the panels+charge controller+batteries can be mounted close together--I have no problem with that...

    Regarding one "large central system" vs smaller distributed system... The lower per watt capital costs of the larger system might allow you to "stock" some spares--and extra charge controller, an extra inverter, etc... It certainly will make debugging a lot easier (phone call: "its broken... What's broken? I don't know, the inverter won't turn on. How's the battery voltage? etc. vs Try replacement inverter--does it work?).

    You probably will want to include some basic stuff (like hydrometer and "water saver" battery caps to reduce mess/distilled water needs), a DMM (digital multimeter) for debugging/checking health, etc...

    A lot of the choices will depend on the ability of the locals to manage the installation and how much in the way of local resources/fabricators are available to build locally (mounting racks, local source for wire, UV/Outdoor rated wire to prevent "insulation failure" if in direct sun, source of distilled water, pride of ownership--will somebody "monitor power usage" and battery state of charge to insure that everything is used correctly.

    Notice, the small solar system that they loved--failed after a couple years and may not be able to be repaired using local suppliers (solar panel? Charge Controller? Inverter? Battery? --what failed? and are they sure they know what failed and why it may have failed?). Wonder what it was used for? (lighting, radios, etc.?)... Probably system is probably not large enough to power a fridge or laptop computer...

    If a large system is wired for central AC power--the genset would be the backup until the solar is repaired (as well as backup for charging batteries when no sun and/or heavy use).

    If multiple smaller systems are built--there can be a big advantage if all are built using the same components... Commonality of spare parts, less training/knowledge required to support multiple systems, etc. But would probably want some ability to bring AC power to charge batteries when needed (no sun, failed charge controler backup, etc.).

    A 10kW genset running a few hours a day supplies a lot of power with "cheap" infrastructure costs. Obviously, ongoing fuel costs are not cheap.

    I certainly don't know all of the answers--and did not aim for a minimally priced system at this point (shipping costs to B.G. may be more expensive than the components themselves).

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