Small Solar or Wind system for van, boat, bender etc

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  • I would like to start a discussion about building various decentralised energy systems so people who have limited knowledge can make informed choices and get themselves off grid.


    So this first thread is for the smallest, most basic proper off grid system. I am not thinking of small hand held solar devices that can recharge some AA batteries or a mobile phone. I am thinking a a fully useful system that can be fitted to a boat, a van, a bender or small shack that doesn't really use a massive amount of electricity.


    So let's discuss a system that could power a handful of low power LED lights, charge a phone, power a laptop for a couple of hours a day in the UK climate.


    What panel would you need. What charge controller, what batteries and cabling would you need.


    When we have discussed this for a while I will post another thread on a bigger system and so on.


    So, what do we need to buy and what do we need to know to get ourselves off grid in the most basic of ways?

  • If you are new to all this, how do you work out either how big a system you need to meet your demand or what you can get away with using with the system you have.


    How do you work out how much your laptop will use an hour or how much LED lights are using?


    Paul

  • Do your calculations. If you are consuming more than what you store in your battery bank, you may need to expand your battery capacity. Below is a calculation table where the data of electrical home devices are given as an example.


    [TABLE='width: 80%']

    [tr]


    [td]

    Appliance

    [/td]


    [td]

    Power Draw (W)

    [/td]


    [td]

    Daily Usage (h)

    [/td]


    [td]

    Energy Consumption (Wh)

    [/td]


    [/tr]


    [tr]


    [td]

    1x TV Set

    [/td]


    [td]

    150 W

    [/td]


    [td]

    2 h

    [/td]


    [td]

    150 x 2 = 300 Wh

    [/td]


    [/tr]


    [tr]


    [td]

    3x Compact Fl. Lights

    [/td]


    [td]

    20 W x 3 = 60 W

    [/td]


    [td]

    4 h

    [/td]


    [td]

    60 x 4 = 240 Wh

    [/td]


    [/tr]


    [tr]


    [td]

    1x Laptop

    [/td]


    [td]

    60 W

    [/td]


    [td]

    3 h

    [/td]


    [td]

    60 x 3 = 180 Wh

    [/td]


    [/tr]


    [tr]


    [td]

    1x GPS

    [/td]


    [td]

    15 W

    [/td]


    [td]

    6 h

    [/td]


    [td]

    15 x 6 = 90 Wh

    [/td]


    [/tr]


    [tr]


    [td]

    TOTAL

    [/td]


    [td][/td]


    [td][/td]


    [td]

    810 Wh

    [/td]


    [/tr]


    [/TABLE]


    A 12 V, 98Ah battery would store 1176 Wh of energy. If you buy two of them and connect them in parallel (app. 2350 Wh), you would have at least 3 days of autonomy in your system even if you never charge your batteries. However, you should only install a system that would charge the batteries during the day/whilst using it.


    Here is an easy-to-use calculator - http://www.photonicuniverse.co…o-choose/12V-solar-panel/ for laptops and other stuff.

  • But surely you don't want to run your batteries down too far each time. You may only want to run them down 20% of their capacity so does that mean that you want at least 5 times the battery power that you expect to use on any day?


    Paul

  • We live in France where the average insolation is equivalent to the dark orange part of the UK map above.


    Our first solar panels were cheapo amorphous silicon panels. We had four which produced about 40 watts on a sunny day. We used a good tractor battery (Which lasted about a year) and a Steca controller which we still use daily, more than 20 years later.



    That gave us one inside and one outside light (Inefficient 12v car bulbs) and we ran a car radio with a cassette player. It was fab. :) As we didn't use the outside light much in the winter, we got by OK without buying candles or petrol for lamps and reduced the stress of burning down our wee wooden cabin.


    When we built our house we stayed off-grid and our first system was a four 75watt solar panels and two little Rutland 910 wind generators, plus the same Steca controller and after some experimentation we used six 100 ah batteries.



    We wired the house with thick 4mm cables, going down to 2.5 mm for lighting. I bought a laptop and connected to internet (Before broadband - imagine !) in 12v using a car DC reducer and the system ran all the lights (about 12) - mostly fluo and some leds (We hardly ever used more than three at a time) and we splashed out and bought a new car stereo with a ten cd loader. In 15 years we've replaced the batteries once and we've only ran out of leccy once. We're very frugal and watch the battery levels and power consumption around the winter solstice unless there's plenty of wind.


    In the UK, you'd have to increase the number of panels depending on where you live but we lived with that system for about four years until I became addicted to the internet. :D


    I've more photos and info about off-grid stuff in this album : https://www.flickr.com/photos/…py/sets/72057594066748877

  • Thanks for this thread and to all contributors. I am looking at experimenting soon setting up a small solar setup with a view to learning about it for a bigger setup for my long term project. This is exactly the sort of information I need, thanks for asking the questions aman. This will help me and I'm sure a lot of others.


    I am unbelievably ignorant on the whole topic, especially the electrical side of it. I plan on making my own panel from cheap solar cells, seems the most cost effective way still.

  • Adam,


    Experimenting with a small system is the best way to learn before making expensive mistakes. I have a few little solar systems (Caravans etc.) here - I can take photos to show you anything you're unsure about - just let us know if you need help. :)


    Irene

  • A question for the experts.


    You work out your average daily usage and you buy your batteries based of that figure. You build a battery bank 5 times the capacity you use per day so you do not run your batteries down below 80% to protect your batteries and to have a decent amount of surplus for occasions when you have less sunshine.


    Is this correct so far?


    If it is correct. Do you size your solar array based on your daily usage figures plus a health surplus or does the size of the array correspond with the size of the battery bank?


    paul

  • The array determines the amount of energy you will have to store in the batteries. It must be able to charge the batteries fully, say once every ten days. (Winter too :D) If it doesn't, you need more panels or fewer batteries or something else to charge your batteries in winter.


    This is important, because a good controller will need to allow the battery charge to increase from it's normal voltage of around 13.8v (A full battery when the sun is shining.) to around 14.2v for an equalisation charge. This is programmed by the controller to happen about once a month and your batteries need this charge to keep them in good condition. This charge usually lasts around two hours.


    Steca features.JPG
    Source : http://www.brightgreenenergy.c…-pr-solar-controllers.asp


    The voltage levels I've given can change slightly depending on the kind of batteries you have - Gel, AGM etc. and a good controller can be regulated by you to correspond with your battery type and perform in the appropriate way. Once you've set the controls, it's all automatic.


    A cheap controller won't handle certain types of batteries or perform any fancy stuff but it should stop your battery/s from going under 11.5 - the danger level for some batteries. I think it's worth spending a wee bit more on a good controller to keep your battery (If it's a good one or if you've a few) in good condition.


    Irene

  • Also, in my experience, it's better to have too many solar panels than too few. Your batteries will happier and when you have excess energy you can charge your and your pals' 'phones, laptop, hand tools etc. ready for a rainy day.


    People who live in vans, benders, cabins and so on tend to be closer to the vagaries of the weather and you know your batteries are full because it's been sunny all morning (And you check your controller regularly :angel:) so you can pump up the volume of your speakers all afternoon if you like !


    Try to always think of saving energy and using excess energy. Buy things which consume very little energy. I've two reconditioned 8 year old Lenovo 15" laptops (I like to be always have spares) my main one has a three year old battery and when it's been raining for a few days, I can turn the power consumption down when I need to. For example, tonight I'm using under 20 watts to type this. Here's a screenshot :


    lenovo wattage.JPG

  • So if you were building your first proper solar system to run lights, intermittent water pump, couple of hours of telly on a small 10 inch 12 volt telly or a couple of hours on the laptop What size panel, battery, cotroller and cables would we need.


    i am trying to get a definitive answer for building a small solar system. the sort of thing that we might build to teach us all about how the system work. once we have this information in black and white we can move on to a slightly bigger system and so on


    paul

  • There is no definitive simple answer Paul.


    You can find calculators online.


    The issue is voltage drop when cables have too high an amp draw through them for their length, all copper and ali cables have voltage drop however short they are. The longer they are the bigger they should be to the point where ideal cable diameters on larger 12 home systems can be pretty high.


    If the solar or wind array is a long way from its point of use one cheap way is to make the system a 24 volt or even 48 volt and drop the voltage down close to the point of use. Amps = watts/volts, and amps are the main limiting factor. This is the same way the national grid works, up the voltage massively to transport the electricity around.


    The lower the voltage and higher the watts used, the larger the cable needed, most of us are limited by budget rather than space. Sometimes it is cheaper to just buy an extra solar panel and battery than to up the wiring size to the ideal, copper cables are not in the slightest bit cheap.


    Also your appliances vary with allowable voltage drop, my 12volt LED lights will still give me usable light on 9 volts. So I just use small diameter reclaimed flex extension leads because voltage loss is not critical. The lights


    Older small 12 TVs are not that efficient compared to modern highly effecient LED ones, I was looking at one the other day, 48 watts for a 42" tv. Fairly voltage critical though I assume. maybe have a single high amp draw power point for TV and computers with large cables and the rest as good as you can afford to make it.

  • Google ohm's law before you start.
    Any thing less than 10watt is AA and slightly bigger.
    20 /50 watt is small, you can run the laptop for a few mins on a sunny day, more than enough LEDs. Tablets are ace for low power consumption.
    100watt + for laptop or tv. And then some.
    4/600 watt wind generators on eBay for just over £200.

  • Paul, can you do a plan of the space you live in and where the lights, TV, computer, solar batteries etc. will be. Also how far away is the water that needs to be pumped, how many watts is the pump and how high do you need to pump and why ? (There may be a better way to move or collect water.)


    Do you have a good place to put your panels - south facing on around a 30° slope (Please correct me if I'm way out for Cornwall folks.)


    Between us, we can design a system that'll work OK and help you to source the right materials.

  • Always go for a more powerful system than you'll need initially - your 'needs' will grow. Also beware some manufacturers claims, do the calculations carefully and look for system or item reviews before buying. Not like our local council.


    A few years back, under some 'alternative' funding system, a local council agreed to erect a wind generator for the toilet on our allotments. The suits sold them a system that was said to generate enough power to provide toilet lighting, hot-water heating, toilet fans, the whole bit. The council officers were delighted, even excited. They were not engineers. They believed the suits.


    One of our chaps on the allotments who is a retired electrical engineer went along to a meeting, and pointed out that the maximum output of their expensive system was only around 35w, perhaps 40w in a very strong gusting wind. This would be sufficient to power a cluster of LEDs, and not much else. He was not listened to; the council spent thousands on the system and its installation.


    Now we have a (quite reliable) wind generator that puts out 35w at maximum, mostly around 15 - 25w, and provides sufficient power for a cluster of LEDs to light the toilet, and a timed fan for about a couple of minutes. It is acting as a trickle charger to the storage battery, 1 - 2A at 12v.
    If they had done their research they could have bought a more powerful system at half the price.

  • Paul, can you do a plan of the space you live in and where the lights, TV, computer, solar batteries etc. will be. Also how far away is the water that needs to be pumped, how many watts is the pump and how high do you need to pump and why ? (There may be a better way to move or collect water.)


    Do you have a good place to put your panels - south facing on around a 30° slope (Please correct me if I'm way out for Cornwall folks.)


    Between us, we can design a system that'll work OK and help you to source the right materials.



    The point of this thread is to give information to people who may be new to solar to give them the basic building blocks so they can design their own system.


    I am not designing an actual system in this thread but a hypothetical system based on what I think a small van or bender might need.


    Water pumping would be from a tank under the sink to a tap at the sink


    Paul

  • Post by weijing3333 ().

    The post was deleted, no further information is available.
  • As anyone ever tried wind power on a van? I was pricing up a roof vent for the van, the kind that spins round and my mind wandered to thinking of a windturbine to charge a leisure battery while your driving.

  • Isn't that what your alternator is for?


    paul


    Sorry I meant charging a leisure battery or help in charging a leisure battery hooked up to electrics and chargers etc with maybe a solar set up, I thought about it when I saw a fridge van where they have a vent? On top and I was thinking if you put some fans in and hook it up to a battery, however no idea how much it would charge.

  • [quote='ollieollie','http://ukhippy.com/freakpower/forum/index.php?thread/&postID=1412577#post1412577']This has to be about the most basic and straight-forward system for any vehicle IMO.


    solar-power-setup-diagram.jpg


    n.b. For those of us in the UK, where it says 110v read 240


    this really helps me the diagram.
    i dont have a clue about any of it as its been 10 yrs since living in coach in the mid 80s, it was all basic then. ive been trying to get my head around what all these components do, and working out the best set up for my needs. i wish i found this forum months ago, ive been trying to ask advice on facebook, but waste of time there... I want to run enough juice to run a mains stereo most of the day, laptop, mobile, and few other small appliances. dont use cooker, mainly burner, and dont have proper fridge just a cooler 12v.
    i dont have loads of money to spend, but i reckon from looking on bimble its gonna cost me over 400 quid ? for everything, and thats doing it on the cheap ? plz tell me if im wrong. im slowly learning all this, but this is so helpful to me.
    much love & light
    mark