New Off-grid house

zoneblue

Re: New Off-grid house

Coot, in the last two weeks we have had 226mm of rain. Its done nothing but rain, its a spring thing where we are. (Its also what allows NZ to run its grid using 75% hydro.) I guess for some folk thats a whole years worth of rain, but is quite normal here, not out of the ordinary.

Yet, on only two days did we not float. Dawn rest voltage not below 24.6V those days. I cant tell you the exact SOC, but it was no where near my worry level.

Heres the blackbox daily agregates for that period:

date_created	classic	rev	firm	plife	durbulk	durabsb	durfloat	maxpout	maxiout	maxvbat	minvbat	ptoday	whtotal	whabsb	whfloat
16/09/2013	150	4	1370	371.1	3.3	1	7.1	1400	51.7	28.5	24.7	3.6	3790	645	1965
17/09/2013	150	4	1370	374.7	1.1	1	8.6	1391	50.8	28.5	25	0.4	3304	612	2308
18/09/2013	150	4	1370	375.1	1.2	0.5	9.2	953	34.8	28.5	25	0.1	3974	248	3431
19/09/2013	150	4	1370	375.2	3.7	0.5	4	650	23.4	28.5	24.7	0.3	1366	229	440
20/09/2013	150	4	1370	375.5	1.6	0.5	3.8	1111	39	28.4	24.7	2.1	1448	351	609
21/09/2013	150	4	1370	377.6	5.3	0	0	459	17.2	26.6	24.6	1.1	603	0	0
22/09/2013	150	4	1370	378.7	5.8	0.4	4.5	985	34.7	28.3	24.6	2.2	1098	211	643
23/09/2013	150	4	1370	380.9	1.5	0.3	9.8	665	23.6	28.3	25.1	1.5	756	132	923
24/09/2013	150	4	1370	382.4	3	0.1	7.9	460	16.2	28.3	24.9	1.8	903	58	1091
25/09/2013	150	4	1370	384.2	11.2	0	0	363	13.4	27	24.8	1	547	0	0
26/09/2013	150	4	1370	385.2	1.7	0.4	8.6	621	21.7	28.4	25	2.1	998	217	1321
27/09/2013	150	4	1370	387.3	3	0.9	7.4	1367	47.8	28.4	24.9	2.8	1433	916	972
28/09/2013	150	4	1370	390.1	3	1	7.1	1575	55.1	28.4	25	4.7	2358	1300	2763
29/09/2013	150	4	1370	394.8	2.5	0.3	9.3	758	26.6	28.4	24.9	1.5	735	169	933
30/09/2013	150	4	1370	396.3	1.9	0	0	325	12.3	26.4	24.8	0.1	88	0	0

Today is a case in point, been raining all day, controller just went to absorb, barest of shadow, still making 460W on 1800W array. Those days where the controller clicks in and out of sleep all day are very rare, maybe a few per year.
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SteveA

Re: New Off-grid house

being a real newb myself one of the things i've picked up on reading the forums is that if you want to live (kind of) like you are on grid (which based on your loads it seems you do) then having an inverter with generator support and implementing it properly will save you a lot of worrying about the worst case. Design your system based on nominal loading and if you want to do something above, the generator is there to kick on and support you.

ChrisOlsen has a very good thread and Youtube video on his implementation.

jtdiesel65

Re: New Off-grid house

The problem in VT is we get multiple 2 and sometimes 3 week stretches without usable sun. Last year was particularly bad. I ran the generator 51 hours from Oct 29 to Mar 30. The lowest it's ever been is 35 hrs. What that says is don't try to plan for a week of autonomy. The weather won't cut you a break every 7 days. You still are going to run the generator.

IMO, you've got to have enough battery to start your bigger loads and enough battery for a few days of autonomy. I'm in the buy more panel camp. I'm not sure it's really possible to buy enough panels such that you don't run the generator in winter, but the larger arrays will help minimize generator usage and drive daily loads without using battery in late fall and early spring. If you aren't using AC, there's almost no point in crunching numbers for summer. If you size for winter, you'll have all the juice you want in summer. What to do with extra summer juice is a common question. I put mine into AC and dehumidifiers.

I think the problem with generator support is the time it takes to fire up and warm up the generator (in winter especially). I don't see how it's practical. I can understand using for an oven
where you have an element, but it seems to me that the scenario would not be good for other types of electonics. I would think the big load would starve the other electronics in the house while waiting for generator power. In our older system, we had a washing machine that shut itself off every time the water pump came on. I've got to think generator support would lead to the same type of behavior. So for me, I would be hesitant to install a system that relied on generator support for peak loads.

From my experience, I would go with the most advanced equipment. 48v. Unless you have absoluely no use for split phase, get a split phase inverter. What is your well pump? Avoid 110v->230v transformers. The startup inrush current on them is huge (esp toroidal). Size your inverter for the loads you don't have yet. Nothing like having to buy a new inverter cause you want to add more loads. It would also seem to me that it would be better in terms of equipment lifetime to operate a larger inverter at some percent of capacity versus a smaller inverter at a large percent of capacity. I've noticed on my older sw4024, quality of juice dimishes as load approaches it's rating.

Maybe I missed it, but what do you have for heat and hot water?

IMO, the AC fridge is no brainer and you don't have to go the sun frost route these days. Our 20cuft kenmore w/ ice maker was rated for 1.2 KWH/day but was about 0.75KWH/day when we first got it. I'm certain it's more now after ~5 years, but it still has got to be around 1KWH. The thing with the gas fridge is it's a heat source in summer and produces moisture (heat+moisture=mildew). We had one. Frankly, I'd buy extra panels just so I could have an electric fridge.

tyagel

Re: New Off-grid house

It's a propane hot water heater and a 240v pump. I seem to have read that some pumps are better made for solar and also that we can potentially put in a larger pressure tank. Although how much hassle is it to change the pump in the well?

I've also wondered how efficient and expensive either a) pumping water up above our house (hill) and or b) heating that water with excess sunny days solar would be?

In any case I want to thank everyone for your very thoughtful replies. I'm probably going to have to start a new thread at some point with some specific install questions in the near future. Thanks again.

jcheil

Re: New Off-grid house

tyagel wrote: »

I've also wondered how efficient and expensive either a) pumping water up above our house (hill) and or b) heating that water with excess sunny days solar would be?

We have a 275 gallon water storage tank on the top of an 18' tower. About once a week, mid-day when I have excess power, I use the well pump to fill the tank. Then the rest of the week the water comes from the tower via gravity feed. I also have a small 12v sureflo pump to give me more pressure from the tank if I need it.

Now, we are in Florida so I don't have to worry about it freezing. If you had a good sized hill next to your house, then you could do the same thing by just placing the tank up on the hill. Maybe even bury it to prevent freezing if that is a concern.

jtdiesel65

Re: New Off-grid house

tyagel wrote: »

It's a propane hot water heater and a 240v pump. I seem to have read that some pumps are better made for solar and also that we can potentially put in a larger pressure tank. Although how much hassle is it to change the pump in the well?

I've also wondered how efficient and expensive either a) pumping water up above our house (hill) and or b) heating that water with excess sunny days solar would be?

In any case I want to thank everyone for your very thoughtful replies. I'm probably going to have to start a new thread at some point with some specific install questions in the near future. Thanks again.

We changed our well pump and replaced it with a grundfos slow start. It may have been $1500 with labor. You can change the pump to 110v or DC, but then you are limited to a certain depth and you'll need to upgrade the wire running to the pump. Usually it's just #10 wire for a 240v pump. IMO if you are getting a new inverter anyway, it makes sense to just get a split phase one.