off grid installations

[SolarRoofSols]

We have nothing booked in at the moment, so using the time to research off grid inverters as I have been talking to someone who wants to be 100% self sufficient for all energy consumption.

Has anyone planned anything like this before and can you offer any advice on how to scope out such a project??

 

[Eco Deal]

You will need to calculate how much each item uses in wattage within the house to calculate system size and battery sizes etc

 

[nowty]

I too am thinking myself of such a thing as I have got more places to put more panels but cannot install any more grid connected PV power.

I have read a fair bit over the past couple of weeks and have already designed several different blueprints.

What I have discovered is that whilst it is possible to generate all yourelectricity during the summer months (April to Sept), it is nigh on impossible to do it in winter without wind generators and /or backup generator. In winter you are getting 4 or 5 times less energy so you would need to ridiculously oversize the system. Also really heavy electrical loads such as washing machine,cooker, etc will probably overload the inverter and batteries.

So I have decided I would just run my background loaditems, internet stuff, telephone, gas boiler, computer, sky box and fridges. Ihave calculated and measured that all this uses about 5 or 6 units every dayand is pretty much constant day to day. From April to Sept 2.5kw of PV shouldgive an average of 7 units per day. In winter the system would be switched backto the grid.

I am proposing to use the Sunny Island system with 2.5kw of PV feeding into it on the AC side using a standard Sunny Boy grid tie inverter set to off grid mode. I would be having a bank of 24v 1000Ah deep cycle batteries.The batteries would hold 3 days of power down to the max 80% discharge but shouldnot normally go below 30% to 50% most days.

Financially, eh ????, not really worth it. But for the eccentric techy type bods like myself, priceless. It would also offer a degree of electricity independence in case power cuts became the norm in the future.

I believe that FIT payments would also be eligible on sucha system (if MCS) but still probably not financially worth it, but it might at least pay for the battery replacements every 5 years or so.

 

[MorganPVI]

12 x 2v 1000ah wet acid batteries will cost £600 per year to buy and replace (every 5 years) - cost price not retail! Sadly this make the whole scheme uneconomic. You also cannot yet connect an island / backup to the grid, but when you can if you take electric usage into account you may break even if you can squeeze an extra year or two from the batteries. If your focused enough to only discharge to 80% then it may pay for it's self under a 21p fit.

 

[nowty]

I fully understand its not economic, its a techy thing and a way of using more Solar PV. I hadalready heard that the sunny island cannot yet (legally) be connected to thegrid but I was simply going to switch my loads back to a grid circuit inwinter, thus the sunny island would still be separate from the grid.

 

[jupestar]

http://products.ikube.it/iKube_Relazione_Tecnica.pdf

saw this in Bolzano last year, loved the concept, even thought of buying one just to show off but the price was too high...

 

[Glen Powell]

I have done a few island systems for customers because they had no electrical lines whatsoever in the depths of wales (yes there are still people out there).

It is suprising how little energy they used due to the lifestyle they lead.

One spec job was changing all the lighting for LED, rain water harvesting using DC Pump, micro wind turbine 1.5kwp, 3kwp panels with backup of a generator.

The house was installed with a wood gasification boiler which heated water and space, with solar water heating water in summer time. The generator kicks in about 3% of the time over the year when both the wind turbine and the panels cannot produce due to snow or ice.

There is definately scope for island systems in the UK where electricity is not easily accessible but would be a major benefit for tourism, agriculture or holiday retreats.

 

[Adam W]

If it is the cost of batteries which is prohibiting this can the energy be stored elsewhere, for example some kind of small scale pumped storage hydropower system, or lifting a weight up a disused chimney?

 

[liquidity]

The formula for potential energy is m x g x h where m is the mass, g is 9.8 and h is the height the item is raised. 100 litres of water raised 10m would generate 9800w of energy assuming a 100% efficient hydroplant. Might not work well in the winter as ice doesn't flow very well.

The nice thing about batteries is that their output is pretty much self regulating - much harder to do with most other stored energy methods.

 

[SibertSolar]

We've been working with a client who has got around the whole non-G83 issue with sunny Backup, very interesting way of making it work for his customers.