Mostly 12v system, but...

[Medianige]

Ah - irradience. Where we are we will get in excess of 1900KwH/m2 per year...

[Naptown]

Ah - irradience. Where we are we will get in excess of 1900KwH/m2 per year...

But you design a system for the two worst months of the year when off grid.
So say Dec Jan what is the insolation per day?
Also plug the washer into a kill a watt and see what it actually uses for a few varying cycles.

[Medianige]

Jan, 2.48
Nov, 2.50
Dec, 2.09

Panels pointed due south.

[Naptown]

OK so based on the newest info of 2.09 KW sm/d
3500 x1.5 /2.09 = a 2.5 KW array or 10 250W modules.
Probably not what you wanted to hear but what it will take to work.
battery bank will also need to be increased to account for max charge rates on the batteries.

Think load reduction.

[Medianige]

No problems - just means no coffee machine... She'll just have to use the percolator on the stove!

So... If we go with 750w of panels, 3x 250w wired in series (?), and connect these to say, 4x 12v, 110aH batteries (also in series), what capacity would that give me? If I assume a washing machine of 1000w using 5amps for the shortest cycle of 35 minutes and assume no more than 3 times a week (perhaps only two), would we be close to being OK? Would I use too much power from the batteries?

I think the battery bank becomes 48v and 440aH, is this right? The washing machine will use just over .5kw at 220v, but how much amperage will it use? This will be our highest consuming appliance.

(I can't believe I actually studied physics and now, 35 years later, I can't get my head around the calculations anymore! sheesh.)

[Sunking]

So... If we go with 750w of panels, 3x 250w wired in series (?), and connect these to say, 4x 12v, 110aH batteries (also in series), what capacity would that give me?

Well put some pencil and paper to it.

If it take 2500 watt of panels to produce 3500 watt hours in a day and you decrease the panel wattage to 750 watts is 30% of 3500 right. .3 x 3500 watt hours = 1050 watt hours. You have to shave a lot more than a coffee maker. Try everything but a few lights and your computer is about all you can run with a 750 watt panel system in your area.

[Medianige]

I'm missing something here - or not explaining something properly.

I have a friend 2 miles away who has 2x 230w and 1x 240w panels; 12x 2v (880aH) batteries. She runs a fridge freezer (about 6hrs/day, on a timer, 3hrs in am, 3 in the pm), lights, computer and TV (satellite), plus a washing machine once a week - she goes to float usually around 1.30pm (in winter, earlier in summer). Very occasionally she uses a genny for the freezer (or to top up the batteries if there is a lot of snowfall). Careful husbandry of appliances is needed though, she only turns the PC on when she needs it, etc.

Another friend a bit further away has 2x 160w panels and they are more careful but again they run computer, lights, and a fridge. I don't know what their battery bank is, though.

All I would like is enough power to run a washing machine (the peak appliance) for 30 minutes or so, 2x/3x a week. The rest of the time, the 'mains' system will only run the satellite TV (not often) and perhaps be used to charge the Macbook. So I don't understand why, the other 3-4 days, I won't have enough sun-time to charge the batteries.

I know I'm a bit dim, sorry.

[Naptown]

You need to do a very accurate and thorough assessment of your power requirements. A generator and charger are must have items. Budget for them. Try living in your current home on the power you plan to produce. You will see a major lifestyle change. We can't change the amount of usable sunlight a day you will get in a particular location, The physics of photovoltaic generation or the physics of battery charging or discharging. The only variables we can work with is the daily load, amount of PV required and capacity of the batteries to store the energy. Well there are some tweaks but those are the main considerations. The daily load is the most variable and the only one that you have some control over.

[Mike90250]

battery suggestion - 6v, 200ah golf cart batteries. 8 of them wired in series = 48V. They will be a good learning set, should last you 2-5 years.

A good charge rate for them is 20A @ 50V from a MPPT controller. That would need a 1,200 watt PV array.

And you will have to switch off the power cord for the Sat Dish when you are not watching, they generally draw 40 watts - over a 24 hour day, that's huge = 960 watt hours, nearly as much as a fridge would consume !

BUT - don't spend any money yet, there are still way too many unknowns left hanging.

As to what your friends and neighbors are using, they are doing remarkably well, with their small systems.

And for running the washer, do it on a sunny afternoon, and let it run off the solar panels, then you gain about 30% efficiency of not having to recharge batteries, the inverters in running right off the PV array.

[Medianige]

Thanks. I'm currently unemployed and my last bill (2 boys + me: electric shower, 9kw; George foreman-type grill; halogen oven, 1200w; washing machine, tv, MacBook, router, iPads/iPods, cfl lights and fridge-freezer, ps3) was 1.31Mgw for the year. I generally watch tv through iPad or Mac

In spain, we already have freeloaders for the iPads etc., and can also charge SLR cameras through the car. Here I already switch things off (except router/fridge/freesat box), or not even ON, when I can. I barely use lights at all.

When in Spain, we'll shower, cook from butane (v cheap, 10-12$/month), and the cave will have a cold store (about 4c) so the key thing for my partner is a washing machine. For some reason she doesn't want me to wash her clothes in the shower!!!

Thanks for the battery info, Mike.

As far as the dc system goes, I guess that'll be ok?

[Sunking]

Thanks. I'm currently unemployed and my last bill (2 boys + me: electric shower, 9kw; George foreman-type grill; halogen oven, 1200w; washing machine, tv, MacBook, router, iPads/iPods, cfl lights and fridge-freezer, ps3) was 1.31Mgw for the year. I generally watch tv through iPad or Mac

OK that works out to 1.31 Mwh / 365 days = 3600 wh/day.