Help on panel sizing and number

Re: Help on panel sizing and number

I know I said I would shut up,, but one more suggestion. Since you are committed to the honda to fill the bulk tank, then installing a 12 or 24 vdc shurflo from the gravity tank to the pressure tank would be a very simple solution. Since you are not lifting water thse little pumps will pump ~ 5gpm into a P-tank quite nicely.

My neighbour has a similar system,, a 2000 gallon bulk tank that he fills once a week, and then has demand pumps at each cabin. They work flawlessly with little energy draw, certainly way less than a jet pump.

Once again, shutting up now!

T

Re: Help on panel sizing and number

Since your largest single load, (the hair dryer) is ~ 1500 watts, an inverter in the 2 kw range would be about right. In a 24 vdc configuration your options get more limited. the Magnums get very big at 24 vdc:

http://www.solar-electric.com/maenms4040wa.html

http://www.solar-electric.com/sa15wa12vosi1.html

http://www.solar-electric.com/exxp1224vo20.html

If you go back to 12 vdc your options are better.

http://www.solar-electric.com/maenms2020wa.html

Your 620 ah of battery (24vdc) will yield 7 kwh at 50% DoD, 3.5 kwh at 25% Dod.

2000 watts of panel will generate ~ 4 kwh/day on average, useable out the inverter.

By your calcs you are going to use ~ 1.5 kwh/day. Change the pump system and you might drop that by ~ 500wh/day, making ~ 1kwh/day.



Tony

Re: Help on panel sizing and number

Keep it simple,,

Take your one day calc,, and call it 2.1 kwh.

For no sun days, multiply that number by the number of days you wish to go with no sun, I would suggest 2 or possibly three, making a total of 4.2-6.3kwh.

To draw a 24 volt battery no more than 50%, you would need a battery in the 350-525 ah range (24 vdc).

To re-charge that (5-13% of AH capacity) you would need panel capacity of say 25 amps, or ~ 600 watts, plus 25% loss or ~ 750 watts of PV. That same 750 watts of PV should deliver ~ 1.5 kwh/day. Now you would have little chance of ever getting "caught up" if you indeed do consume 1.5 kw/day with this system and you let your batteries go to 50%, so a system that would give you 2 days with no sun, and then have enough capacity to recharge that loss, AND power today's loads you would need to double that to ~ 1.5 kw of Panel. Personally, I don't like to draw my batteries down more than ~ 15% per day or ~ 30% before recharging them to 100% for longer battery life.

The answers to most of your questions are not hard and fast, and indeed predicated on how often/how much you are willing to run the genny, how far down you are willing to draw your batteries, and how quickly you are wanting to restore them to 100% charge.
A compromise on one set of parameters requires a change on the other(s).

One thing that is unclear to me, why are you calculating a 600 wh daily load just to standby an inverter? Having an inverter run at that (in) efficiency doesn't seem to make sense,,, that is over 50% of your total loads. What am I missing?

Tony

Re: Help on panel sizing and number

You cannot run a 1/2 hp well pump off a 12V inverter.

My 1/2 hp pump draws a solid 1,000 watts running, and I would expect starting surge to be 3-10 x that.

a 5000W surge for 5 seconds, would be 416 A from the batteries, and the voltage droop from that, would likely shut the inverter off after 3 seconds. Inverter and pump resets and run through the loop again.

Better idea would be haul in a couple more 40 gallon pressure tanks, to get charged by the pump, and cut it's cycle time down to 2x a day. Maybe put a tank in the attic for a little bit of gravity feed for hand washing and such, and let it fill from the pump.
You might get pump time down to 1x a day, with clever management, and you could run the microwave and battery charger after the pump shuts off, and just plan on a 15-30 minute runtime on the genset daily.

Re: Help on panel sizing and number

Robert, No worries, we are all here to help and once in a while we come up with a good idea!

How about this as an idea. Let's start from scratch, with no investment in any hardware or wiring scheme? Let's start with the loading doing it two ways,, once with using the existing pump configuration and once considering a different pumping system.

That way we can start with a clean slate, and not have to make compromises due to hardware assumptions. (For example, 600 wh of inverter standby that consumes more than 50% of all other loads is something we should be able to work around).

Going back to your post #30,

Eco Lights (3) 16W x3 = 48W 35 1680
Water Pump 1104 W ** 1 1104
TV 200 W 14 2800
Stereo 50 14 700
Hand mixer 300 1 300
Vacuum 1440 1 1440
Hair Dryer 1500 1 1500
Drill Charger 80 1 80
Misc Chargers*** 120 8 960

Let's look at this line by line.

Lights 16*3=48watts 8 hours/day=384 wh/day 2600/week (I think your lighting is too small.
TV 200*14=2800 (Consider a new flat screen that only draws less than 50 watts)
Stereo 50*14=700
Mixer 300*1=300
Vacuum 1440*1=1440
Hair dryer 1500*1= 1500
Drill 80*1= 80
Misc chargers 120*8= 960
Total weekly load without pump 10,380 wh, 10.4 kwh
Average daily load 1,485 wh,or lets say 1.5 kwh/day

Now if you install a smaller 12 or 24 vdc pump that draws say 200 watts for 1 hour a day, that would add another 200 wh/day, so lets say 1.7 kwh average daily load.

Now, lets look at your largest load (again, assuming you change the pump system) The hair dryer or vacuum. In this case you would then need, to drive these items an inverter in the 2 kw range. The standby load draw of a 2 kw Magnum is ~ 25 watts. The Xantrex 1800 inverter will power those loads with only a 1.5 watt standby load.

So the obvious choice would be the Xantrex on first look.

So now lets look at the battery configuration. To deliver ~ 1.7 kwh day would be ~ 150 ah/day @ 12 vdc. A 900 ah battery would be drawn ~ 16% delivering 150 ah (12 vdc) Halve the battery bank and your daily draw would be ~ 32%,, two days, 62%.

So to charge a 900 ah battery bank, you would need a minimum 5% current or ~ 45 amps of panel. Ideally you would double that for a 10% charge rate. To get 45 amps into 12 vdc you would need ~ 650 watts (12v*45 amps + 20%) to start, 1300 watts would deliver ~90 amps.

So keeping it at 12 vdc keeps the hardware costs down. The panel requirements would be the same if you went with 24 vdc. Most people would prefer 24 vdc, I personally like 12 because of the available 12 volt hardware. (Samelex makes a 24 vdc inverter but I don't know what the idle draw is.)

I really think you have to get rid of the 1/2 hp if you are going to get this down to a manageable size and budget. As several people have mentioned running a 1/2 hp pump off a small inverter is really a non starter. The price of a replacement is more than offset by the reduction in system cost. While I am on that subject, there are several other conservation measures to consider that will pay for themselves with smaller system costs. For example, buying a new TV for ~$200 will reduce energy consumption by over 75%, reducing the 400 wh/day to under 100 wh. The same can be said of the stereo. Losing 200 wh/day from the loads, reduces the system size by ~10%. (Both batteries and PV.)

One other comment I would make, which comes as advice that is not asked for, I would buy a Honda EU 2000 generator and off load the two big draw items, (the hair dryer and vacuum) to the generator. That way, you could down size the inverter to a Suresine 300 to cover all the other loads. Then by time shifting the small charging loads to times of good sun, you could down size the system further. The Honda generator run an hour a week for other things will burn ~ 1/4 of gas every two hours, so it would burn a gallon a month! You are going to need a significant charger for times of no sun anyway so a genny is going to be in the equation anyway.

As a side note, we live in a very small cabin in far northern Ontario. We have 400 watts of panel, 450 ah of battery. Daily we use ~ 5-600 wh of power for everything. We don't have a TV, but we have two lap tops, sat modem, wireless internet router etc. We almost never have to run a generator to charge. We fire it up for the vacuum and for power tools.

So in your case, at ~1.5 kwh/day you could simply double our system and be in fine shape. I guess that is all for now. What really needs to be addressed is the pump issue, as it is the driver of much of the problem getting this system to work. As I said before, (and I said I was going to shut up!) if it were me, I would install a shurflo 9300 in the lake on pex tubing, with a drain at the lake shore, plumbed directly into the P-tank and be done with it. It would get rid of the standing bulk tank, get rid of the need to run the honda pump and would deliver all the water you would ever need for a family of two, drawing ~ 50 wh/day, with no load on the inverter, no up sizing of the inverter, no complicated plumbing etc.

I know that you are sort of stuck on the cost of a replacement pump, but in fact it will save way more than it costs.

Tony

Re: Help on panel sizing and number

I think you guys are on the right track. I ran a 3/4 hp centrifugal pump on my house boat for 10 years, keep up a large battery bank and inverter to run it. It pressurized a Toilet system for two jet toilets. It was a $1100.00 pump and over a weekend it would suck a 1000 amp hr bank down.

One day I trying to find a replacement as the pump was leaking. I started looking at the pumping curves. A centrifugal pump does great with no pressure, but as soon as the pressure rises + 40 psi , they drop off to almost nothing. I was trying to pressurize a bladder tank , but there was almost no flow going in the tank at 60 psi.

I found these pumps. They will go to 100 psi and still have 1.5gpm flow. At 5 + Gpm they are more that adequate for a house.

They are pulse modulated and run at a variable speed. The 12 v dc model is 10 amp. They are available in 120 v also.

http://www.aquatec.com/rvpump.htm

These are the ones I have.

http://www.rvupgradestore.com/Aquajet-RV-Variable-Speed-Water-Pump-p/aquajetrv.htm

Re: Help on panel sizing and number

icarus wrote: »

The aqua jets are very similar in design and function to the shurflos. What I like about the shurflos is that they and their parts are available nearly everywhere.

T

That is true, but I never found a Sureflo with 5 diaphragm chamber and 5.5 gpm of flow in this type pump, maybe I didn't look hard enough.

Re: Help on panel sizing and number

icarus wrote: »

Looks like a nice pump. I like the soft start feature. One issue with diaphragm pumps is the vibration. An easy solution is to install a loop on the inlet and out let. Cuts the noise by ~ 90%

T.

That is a nice tip to share, must come from long time experience. The new pumps with the variable speeds use a transducer rather than a analog switch create more vibration than the older ones unless you add the loop of flexible line.

It's really nice the way you'all share knowledge on this forum.

Re: Help on panel sizing and number

First, my apologies if I have made the situation more confusing in the quest of making it less. Second, I don't profess to be an expert on much of anything, especially when it comes to the technical details of electronics. That said, what I am reasonably good at is providing real world solutions to what might be vexing problems, sometimes with elegance often without.

The crux of the entire issue is the pump, both it's load demand in watt/hours but more importantly in it's peak demand on both batteries and inverters. Solve the water pumping issue, and all the others become easier both to calculate and to build.

As has been said before,, define the loads, and you can in a general way define the system components. Eliminating the pump (or modifying it) changes every other equation. The bottom line, off grid solar is an expensive way to generate power. If one chooses to go that way, that is the first thing that needs to be understood.

In your initial postings, you mentioned that your friends were running a generator ~ 6 hours a day, consuming lots of fuel. Far and away the cheapest alternative is to use a generator that is sized for the loads. For general lighting only, (all your loads except the hair dryer and pump if memory serves) a Honda Eu 1000 will run 6 hours a day a 25% load and burn ~1/4 of fuel,,~$1.25 at todays per litre price in Northern ON. for a purchase price of ~ $800. Use a Eu 2000 and one could run all the loads, and burn perhaps 1/2 again more fuel. As with all generators, they run more efficiently when closer to full loads than not. The beauty of the EU series is that they will dial down the engine speed (and the fuel use) as the load decreases. I suspect that your friends are using a fairly large full speed generator for all their loads, burning way more than would otherwise be needed. (Making much more noise as well).

A simple alternative would be get a battery bank to run the lighting, TV, Stereo etc at night, (to keep run time down, and noise down) Then during the day, run the genny for other loads (including the pump) while at the same time running a proper charger to recharge the previous nights draw. ( Or you could do the opposite, run the genny at night charging the battery, reducing the load, and use the battery during the day. You could then buy a small solar panel set up to keep the batteries topped up over the winter.

So, there is another alternative. I stand by my suggestion in my most previous post(s) about the system I would build if it were my place. Eliminating the big loads, and the loading and system requirements would pretty much mimic my own,, 400 watts of Panel, 450 ah of battteries, 300 watt inverter, 20 (or 40) amp charger, and a Honda Eu 1000 (or two for peak loads) and a Shurflo 9300.

Don't feel like you are being troublesome. Everyone here is willing to help, and if sometimes the advice seems contrary, it is usually because, as I said earlier, there is more than one way to solve the problem,, there is no one "right" answer.

Good luck and keep in touch,

Tony