Wind turbines, solar panels, battery management

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A plea! If you really want to invest in residential renewable energy, but don't feel confident enough to do it yourself, then please be aware of the pitfalls associated with the renewable energy bandwagon and choose your installer carefully. There are MANY courses out there, some requiring just a few short days of training, but they don't always give you the mix of complementary skills that are required - structural engineer, roofer, electrician, etc. And beware governments bearing Feed In Tariffs. The small print usually has a clause of type "reserve the right to withdraw....economic conditions". We realise this is a complex and controversial subject, but our take-home message when it comes to residential renewable energy is: go for it, but be careful! We are happy to help you out with either a basic information / Q&A day, so you can feel more confident when arranging your own installation, or with detailed in depth DIY courses on solar and wind energy, and offgrid energy management, if you are planning your own adventure!

"Wind [and Sun] energy themselves are free, but converting them to useable electricity is no free lunch", in Hugh Piggott's words. Firstly, consider saving electricity by investing in serious home insulation, better heating controls, energy-saving lights and more modern efficient household appliances. Burn wood to heat your house. Average efficiency of a wood-burning stove is 85% compared with about 15% for an open fire. Ensure that your TV, computer, etc, are not on standby but actually turned off. You can easily save a lot of money with basic energy conservation measures that help reduce your environmental footprint.

Once you have minimised your electricity consumption, then it is possible to plan for your needs by using solar, wind and maybe hydro power. But keep your expectations realistic. Even 25m2 of solar panels will only provide 10-15% of the electricity required for the average family of four, so think more on the level of feeding a couple of storage heaters, lights and a bit of under-floor heating, rather than 2 hot baths a day and a dozen radiators!

A fact which may surprise you... Energy produced by the main supplier EDF is still relatively cheap compared to your initial investment in renewable energy! And if your renewable energy producing equipment is installed commercially, it will likely be 10 to 20 years before your investment is returned. And another fact not generally understood is that the giant commercial wind turbines may take longer, due to the materials and energy used to create them in the first place. i.e. concrete and steel foundations, service equipment and roads, metals and other materials used in manufacturing and maintenance over an estimated 20 year life. The "break-even" point is around 5 to 6 kW, after which the infrastructure becomes unmanageable for an individual. Our 11m high, 4m diameter 3kW wind turbines are near the upper limit of this.



 The below is a very good synopsis that discusses renewable energy for the normal domestic household.

John Tulloch, Flinders island, Australia, (‘Oztules’ on good World Renewable Energy Forums)

Totally Off Grid With Solar?

There are a few installations down here now that came in around the $15000 dollar mark.

They use 10kw of solar, home brew inverter, home brew solar controller, and 35kwh battery banks.

They have no other form of power except they do have generator change over if necessary.

So far that has never been required but for one exception... out on one of the islands parks and wildlife had a rat eradication team over in the worst sort of solar weeks we have ever seen 10 days of heavy rain... and 15 people... this was a bit much, and the genny ( 5hp with modified car alternator) ran for a day..... thats it... power was rationed after that as the 15 city folk had no idea of conservation, and left the shearing shed lights on all night (600w for 14 hrs before the sun comes up), 15 ;lots of phones and ipads, and coffee urn all day and night etc... it was not a fair go really...

Apart form that event, there has been no generator support that I know of on the other sites.

As a rough rule of thumb at 40 degrees south, if you normally use 15kwh/day then use 15kw of solar panels.... if that includes hot water, maybe a few more.

If you don't go silly on the very dark days, ( not just overcast, but dark) you should only use the gennt for maintenance starts.. just to see if it still starts.

I find that 10kw will generate about 8-10 amps in truly terrible light ( 48v system), and more than you can choke on when it is light cloud or sun.... thats 400-500w.

If the heavy cloud brightens up even a little bit, your suddenly up in the 20-40 amp and more but still 8/8 cloud and pretty heavy... 8/8 cloud of single layer, and your back up in the 40-80 amps range... so it takes a miserable day to pull you down.

If you go up to the 15kw arrays, your making more than normal quiescent current no matter what the weather is, and should get 6-7kwh at the very worst... you can live with this as a generality... ie fridges, freezers, lighting and most other stuff except for heating and cooling and hot water.

With the cost of solar panels now, particularly second hand 250 watt panels, that 15kw array is cheap as nuts.... probably in the $7000 range, which leaves $6000 for batteries... and thats too much really, and a few thousand for inverter and controller and fixing materials.

Lets be clear, there is no need for a monster battery or an expensive battery, better to use golf cart ones that will last 5 years, and replace them every 5 years.

6x220ah american batteries can be found for $200, so a 24 battery bank will only be $5000 ( you will probably get more years than that as they will rarely be discharged beyond 25%... and that should give 3000 cycles)

Stylish expensive cells ( whilst I like them very much) are not necessary to produce a better system.

Panels are key and the only thing that is critical, charge controllers are of little interest if you make your own, and mppt is next to useless for this setup... simple 150amp pwm will do fine... maybe $100, inverter around the $300 if using aerosharps or inspires.... point the panels any where you have access too. N, S, E ,W.... east is particularly useful to get the recharge going early, so a 3-4 kw looking east is a good thing, a few kw west, the rest can be almost flat... just enough to self clean, pointing any place.

It really is cheap to go off grid if you ignore the experts, and their fancy add on's.

You only need expensive add ons ( auto generator support and fancy software in your inverter) if your system is inadequate to start with, and now that can be solved with panels..... and you can build 2 of everything for next to nothing so redundancy is a given.

The world has changed simply because power is easy to get now panels are cheap.

Thats my 2 cents worth, and it is working on installations down here.

Inverters are now only about $100 to build the electronics now, so I have plenty of spare change over units now. ( oddly, non have failed yet... I felt sure the island ones would as they are the hardest to get to... but no..)

When the name brands fail ( and they do), it has taken weeks for the owners over here to get back on line.... no fault of the australian manufacturers/agents, but remoteness is everything, and real inverters are not trivial to transport off island and back... could build half a dozen for just the cost of freight alone if we use air freight.

All kinds of things become irrelevant, such as cooling for panels.. we don't want any, so you can clamp directly to the roof if you want, as ventilation is a waste of effort.. we actually want attenuation when it gets hot... coz that means the suns out, and we have probably 7 times the power we actually want then... some losses would be more than welcome. Line loss is a good thing now for the same reason.. when there is lots of current, there is actually way way too much, so losses are irrelevant too, and when the light is poor, the losses will be tiny/non-existent.

Mppt is useless for the same reason, may help when the light is poor, but that will be very rare for the complicated electronics that that brings, and the thousands of dollars that will add to the system.. for what? (15kw of mppt is not cheap... 15kw of pwm is a hundred bucks or so)

But I am the village idiot after all, and am a bit different in my views too.

I will do a thing on the solar controller soon ( Time??? ), and a thing on how to modify the 39 dollar 350w 48v pwm power supplies ( led lighting they use them for) to use as battery chargers. They should work off the shelf, but they don't have adequate o/current protection, so last night I fixed up the three that I blew up testing them( they lasted 10 seconds), and added current control.... now it is a proper tough charging alternative... ie a 40 amp charger for 48v system (38 up to 58v) is now $240 dollars and free shipping.... so you can set the current and the voltage ( I would set for 56... and leave it) Thats 6 units in parallel... and you can keep paralleling them..

...........oztules   29 September 2016 at 9:45pm"

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