You are not the first person who has brought that to my attention and I appreciate it. I will try harder to remember.... and perhaps fix the post now to boot.
Thank you.
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Why are you a "solar fanatic" then? Thanks for your opinions anyways.
I send you bright sunny skies devoid of all doom and gloom.
Best wishes.Leave a comment:
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I didn't mean that solar hot water was "hard" in the sense that it was difficult to put a solar heater into one. I meant that it was hard make it pay off. I don't know where you got the figure of 16000 watts for a hot water heater. Is that the size of your heater? Here is a 50 gallon that takes 4500w. (http://www.whirlpoolwaterheaters.com.../es50r123-45d/)
Turning electricity into heat is not rocket science. Wattage is power and almost all of it turns into heat. It also does not take much energy to keep an insulated water tank hot if water is not used. So, lets say you take a 200w heater element and replace the 4500w element. 4500/200 = 22.5, and so it will take your heater element 22.5 times longer to heat your water. Putting a timer on the hot water heater will not save you money, at least not what you can measure. When I put a hot water heater in my cabin, I called the manufacturer, and asked them about adding extra insulation for a winter climate. They said, not necessary, it was already insulated enough and that it would cost me $30 per year to keep the water hot if I did not use any. The cost is in heating the cold water that fills your tank to replace what you have used. There is one way I think a timer could save you money. If you have a TOU (Time of Use) electric rate plan, you could heat your water at night at the lowest rate. I may actually do that myself, as my baseline allotment will cost me 1 cent per kWh if I change my plan.
Lets assume this web site is correct and it takes 0.0002931 Kwh to raise 1 pound of water 1°F (http://waterheatertimer.org/Kwh-temp.html)
Lets start with a 50 gallon hot water tank and fill it up with water at room temperature, 77F. How many kilowatt hrs to heat the water to 102? 50 gallons of water at 8 pounds per gallons = 400 pounds.
0.0002931 Kwh X 400 lbs X 25 = 2.93 kWh
At 11 cents / kWh that will cost 32 cents.
With a 4500w heater it will take less than an hour to heat. With a 200w heater it will take 15 hours to heat. But you don't have 15 hours of solar. You have 4.5 hours but with some shade. If that is summer, winter is probably 2-3 at best. So it takes days to heat that tank. How many people in your family and how long are your showers?
The average American shower uses 17 gallons. That is about 1kW. 1000 / 200 = 5 hours to heat that water back with your 200w element. That is one shower. If your utility rate is 11 cents / kWH that is what your shower cost you.
Have you figured out how much solar you need to reheat the water for one shower? If I remember correctly you have 408w of panels and are talking about adding 2 more for about 600w. I estimate that those 6 panels might cost from $100 to $150 each. Lets say you get 3 hours of sun a day, that is 1.8 kW which at 11 cents / kWh is about 20 cents of power per day. You don't quite get two showers with that capacity. And you are using up all of your solar capacity to take 1.8 showers per day. You batteries die because you don't have any capacity to charge them.
Now lets say that you paid $1.5 per 100w for your small panels to get 600w. That is $900. Have not added the rest of your solar system, the charge controllers, wiring, breakers, panels, etc.
1.8 kWh X 30 days X 12 months X 10 years = 6480 kWh lifetime. $900 / 6480 kWH = 13.8 cents / kWH for just the cost of your panels. You can play with the numbers with your own estimates of panel life, life of electronics, replacement of heating elements, etc. I also doubt that in 10 years you will have these same panels because as you expand your system there will be better technology and cheaper panels. You could reduce your panel cost with larger grid-tie size panels.
Next topic, cost of powering from your battery. Lets say you get even more panels so you can charge your batteries and take 1.8 showers per day. AGM batteries are not cheap and they don't get the best cycles per lifetime.
100 AH X 1/2 (%DOD) X 1000 cycles X 24v = 1200 kWh for the lifetime of your batteries (you will replace them every 2.73 years, if you take perfect care of them). $300 / 1200 kWh = 25 cents per kWh. I estimated that Costco batteries at $84 ea and 1220 cycles are about 11 cents / kWh.
This figure needs to be further "nuanced" with inverter inefficiency, charge controller inefficiency, etc. Also add the cost / kWh of your panels and electronics, etc. Pretty soon your "free" energy is costing your upwards of 50 cents / kWh and higher, and that is if you don't have any battery failures or need to replace any electronics.
Finally, I said you probably won't be able to use much of what you have already purchased if you expand to power what you have outlined. That is because you have almost outgrown your 24v system already. You will need 48v if you want to run an entire household with hot water heater, washing machine/dryer in addition to all your other appliances. That means different batteries, different panels, different charge controllers, different inverter, etc.
Check my calcs. I do make mistakes, especially when in a hurry. I am also not doing this to discourage you. I am likely going to add batteries and solar to my generator backup because I want the experience and also for backup purposes. But it does not hurt to go into this with ones eyes open.Leave a comment:
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I think you did not look at the video I posted about lower voltage hot water heating elements to change out for your electric hot water heater
Here are some other videos on the DC water heater element item which uses less wattage for solar.
See also https://www.youtube.com/watch?v=6QaBJ7uwoBM
and https://www.youtube.com/watch?v=iGCMwsDYmAw **
They sell 200 watt-600 watt dc heating elements for $35.00 that you can replace your 16000 watt ac elements in your hot water heater. They are intended to run your hot water heater at much lower wattage off of a solar panel and not to be wired back to the grid. Right now though, I am testing the idea of turning off the circuit for my hot water heater right after I take my shower and turn it on ONLY 2 hours before I take my shower. So the hot water heater will be off 22 hours of the day and only on 2 hours/day from now on. If it works out for me, I will get a timer for my hot water heater to turn it on and off for me automatically at those times. Added to this, one could exchange your regular shower head that gives 10 gallons/ hour to one of the new shower heads that only shoots 1 or so gallon/hour under pressure. I will also wrap it in 3" hot water heater blanket to make it keep the water warm inside longer with the heater turned off all day.
Here is another set up to run a regular electric hot water heater directly off of 300 watts of solar panels
This guy sells a device called a solar hybrid hot water controller on ebay that runs a dryer plug to a shut off and then to solar panel wiring. It can be used to plug in either your hot water heater or a clothes dryer to your solar panels. See his website listed in the description box of the video.
As for the refrigerator, I think I may ultimately downgrade to this refrigerator which uses 75 watts and can also be run off of solar. Maybe i will find something a little bigger than this one.
WAIT HERE IS A STYLISH REFRIGERATOR THAT ONLY USES 30 WATTS!!! Kenmore Chill
The batteries were about 150 each.
PS So in essence, the 2 additional panels I just ordered totally 272 watts could be a start in powering a smaller refrigerator and the 200 watt water heater elements. I will try to get one more which would make a total of 408 extra to handle a 30 watt refrigerator and a 200 watt hot
water heating element just long enough to take a daily shower. The water in the tank stayed hot all night long though I cut it off at 2 or 3pm, it is still hot now at 7am the next day! the water runs cold for about 20 seconds but after that it gets hot ! I will turn it on again for maybe just ONE hour today, take a shower and then turn it right back off for 23 hours. I will do this for a month and see how it changes my electric bill.Leave a comment:
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I have some bad news for you. In my estimation you will not be able to use much of what you currently have purchased for the loads you just added to your description. The electric hot water heater is really hard with solar, and I hope your dryer is not electric, is it?
In addition you say "pay off". The bad news here is that you will never make off-grid "pay off" for what you have listed if you have grid power at this location. Solar with battery will cost much more than the most expensive POCO electricity. The price of the batteries alone will kill you. How much did you spend for your 24v 100 AH of AGM batteries? You will probably get at best 1000 cycles from them at 50% DOD, and that is if you do everything right.Leave a comment:
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What AWG wire are you using all the DC that connects to your 1500w inverter? Remember that this would be 63 Amps. Look at this chart -> https://www.bluesea.com/resources/1437Leave a comment:
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I have more loads like microwave, refrigerator,hot water heater, washer/dryer, but I was offering the minimum I would like the system to at least accomplish. Ideally I would like to run as much of all of that as possible. I don't want to limit myself to just a few lights, tv and a computer ultimately since I've already spent too much money to just get that amount of pay off. I already have all the panels etc except the last 2 which are on the way.Leave a comment:
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My design specification is to size the inverter to meet the needs of the load. Your load is 224w. If I had a system with those loads, I would probably get something like a 300w inverter. The best way to plan is to start with the loads, not buy panels, batteries and inverter first. The goal should be to run the necessary loads as efficiently, economically and safely as possible. At least that would be my goal.Leave a comment:
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I already have 2 gauge battery cables with 5/16 lugs. I have 60' of 10 awg cable that came with my panels although I am only running 10' from the roof. I have two 3 branch M3c connectors to join the 3 panels in parallel. I have a 25' roll of 4 awg cable just in case but I see no reason to use that. My charge controller, in line fuses and have screws to tighten on the tip of an exposed wire and everything else has 5/16 lugs to go between the charge controller and the batteries.
I see a formula online that says to use an inverter that is 1.2 -1.5x the solar panel array. Some say you can do 3x the solar panel watts. So since my solar panels are now 408 watts and I have ordered two more which will ultimately total 680 watts. 1.5x 680watts solar panels will call for a 1020 watt inverter. http://www.solarpowerworldonline.com...m-performance/ So it seems like something was off in the calculations that I'd need a 200 watt inverter.Leave a comment:
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I added up all the loads you defined and they came to 224w. When sizing a solar system it is very difficult to grow it later and keep everything balanced. If you plan on running more than the 224w, then it would be good to carefully calculate that. On the other hand, there are advantages to a smaller quality inverter. You can afford a UL listed inverter from a quality manufacturer with a good reputation. Most of the time, the smaller inverters consume less power with no load.I do have a Square D 60 amp 2-Space 4-Circuit Outdoor Main Lugs Load Center with Non-Metasllic Enclosure and Neutral
a SQU QO15 15 AMP Circuit breaker
200A Square ANL Fuse Holder with 200A Fuse
Blue Sea Systems m-Series Mini On-Off Battery Switch with Knob- Red
Inline Fuse Holder
I plan to use this schematic roughly
since the system has roughly the same numbers as my system.
Thanks for that. I have watched videos on youtube about how to wire the circuit breaker box. I think I put the positive wire from the solar panel on to the bottom of the circuit breaker, but I am a little sketchy on the wiring of the rest of the circuit breaker box. Also, I still did not get a ground kit off of amazon yet. I may leave off the circuit breaker until after I test the main parts of the system. I do know an electrician so I may just have him to do the circuit breaker box and the fuses once I've tested the bones of the system (panels, charge controller, batteries, inverter). I do feel very comfortable wiring the panels in parallel to the charge controller. And I have already tested the inverter on the batteries in series with a load plugged into the inverter. That part worked great, so I only have to get on the roof and put the 3 panels in parallel now and then later have the electrician over for the fuses and circuit box. Thank you so much for all your information. You've helped me with the formula for figuring out systems and so much more.
About the inverter being a fire risk, do you say that because a 1500 watt inverter generates a lot of heat or because you fear I may plug too many things into it?
I did read your comment on the matter:
"1) Your inverter is too big for your battery bank. A rule of thumb is Inverter Watts / AH <= 2. Your number is 15. Here is why: Your 1500w inverter can draw 63 AH @ 24v from your 100 AH 24v battery bank. If you take your battery down to 50%, it will take only 37 minutes. The potential discharge rate on your battery may be too high for even your sealed batteries, check the technical manual for that manufacturer."
And I am trying to work through what that means exactly. I imagine you're saying I need more batteries after i get more panels and a bigger charge controller to go with this size inverter
Also another question, about your formula inverter watts/ ah <=2.... if I use say 7 or 8 of these 100 amp batteries , i would then have 700 or 800 ah and that would be a 2 to 1 ratio that is needed? Or do I actually have to switch to a tiny 200 watt inverter? It really seems that a 200 watt inverter would be so small it would make it a waste of money to buy all this equipment imo
There is the danger that you or someone else will power more than the 224w you have listed, and that is a danger to your smaller batteries. How will you wire and terminate your equipment? 1500w / 24v = 63 amps. Look at some guidelines for how big your wires need to be to be used with 63 amps for the distance you are wiring. It will cost much more for bigger wires, but if you don't use them, someone could draw that much current and start a fire. In fact it is possible that a malfunction in a load could cause that sort of draw, isn't it? Then the full potential of that large inverter could overheat your batteries or wiring and start a fire.
I am not an electrician, so I really would not want to advise you on these sorts of details. But I am aware of some of the guidelines which raise red flags for safety.
Read this sticky -> http://www.solarpaneltalk.com/showth...ConsiderationsLeave a comment:
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I do have a Square D 60 amp 2-Space 4-Circuit Outdoor Main Lugs Load Center with Non-Metasllic Enclosure and Neutral
a SQU QO15 15 AMP Circuit breaker
200A Square ANL Fuse Holder with 200A Fuse
Blue Sea Systems m-Series Mini On-Off Battery Switch with Knob- Red
Inline Fuse Holder
I plan to use this schematic roughly
since the system has roughly the same numbers as my system.
Thanks for that. I have watched videos on youtube about how to wire the circuit breaker box. I think I put the positive wire from the solar panel on to the bottom of the circuit breaker, but I am a little sketchy on the wiring of the rest of the circuit breaker box. Also, I still did not get a ground kit off of amazon yet. I may leave off the circuit breaker until after I test the main parts of the system. I do know an electrician so I may just have him to do the circuit breaker box and the fuses once I've tested the bones of the system (panels, charge controller, batteries, inverter). I do feel very comfortable wiring the panels in parallel to the charge controller. And I have already tested the inverter on the batteries in series with a load plugged into the inverter. That part worked great, so I only have to get on the roof and put the 3 panels in parallel now and then later have the electrician over for the fuses and circuit box. Thank you so much for all your information. You've helped me with the formula for figuring out systems and so much more.
About the inverter being a fire risk, do you say that because a 1500 watt inverter generates a lot of heat or because you fear I may plug too many things into it?
I did read your comment on the matter:
"1) Your inverter is too big for your battery bank. A rule of thumb is Inverter Watts / AH <= 2. Your number is 15. Here is why: Your 1500w inverter can draw 63 AH @ 24v from your 100 AH 24v battery bank. If you take your battery down to 50%, it will take only 37 minutes. The potential discharge rate on your battery may be too high for even your sealed batteries, check the technical manual for that manufacturer."
And I am trying to work through what that means exactly. I imagine you're saying I need more batteries after i get more panels and a bigger charge controller to go with this size inverter
Also another question, about your formula inverter watts/ ah <=2.... if I use say 7 or 8 of these 100 amp batteries , i would then have 700 or 800 ah and that would be a 2 to 1 ratio that is needed? Or do I actually have to switch to a tiny 200 watt inverter? It really seems that a 200 watt inverter would be so small it would make it a waste of money to buy all this equipment imoLeave a comment:
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Conservation should be the first thing you do, as it will save much later. On water heating, electric resistant heating is very expensive with solar. I would think at the equator you could use a different solar method to heat your water directly.
The AC/DC refrigerators are designed to take much less power and are a good choice if you can live with the smaller sizes. I would also encourage you to get the technical user manuals for all your equipment and learn them well. The details and safety features are indispensable. Check your system against what the battery manufacturer says about charging their batteries and the same goes with the solar panels and charge controllers, etc. Pay attention to fusing and wire size recommendations in your equipment.
If you have time, stick around and read the older and new posts on the subject. Compare different approaches from different people and make sure you know what you are doing before you start.Leave a comment:
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This is a wonderful breakdown for me I am very indebted to you. I will print this off and review it. You are teaching me a great deal by taking the time to show me this example. I highly appreciate it. Thank you so muchHere is how you would calculate you needs:
125w tv X 4 hours +
38w dish hopper X 4 hours +
6w modem X 6 hours +
45w laptop X 6 hours +
10 watt LED X 12 hours
===============
500 +
152 +
36 +
270 +
120 =
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1078 wh / day
If you take your 200AH battery down to 50% that leaves 100AH
1078 wh / 12v battery = 89 AH / day
But there is an inefficiency in the following:
Your inverter will be 80-90% efficient so
89 X 1/.8 =112 AH
Your big inverter also consumes power, the specs should show self-consume wattage.
You are a bit over 50% but not too bad.
Your panels and charge controller will need to supply:
112 AH X 1/ 0.86 panel inefficiency X 1 / .95 charge controller inefficiency = 137 AH
137 AH X 12v = 1972 Wh
From before your panels put out 408w
1972 /408 = 4.8 hours
You say you have a marginal 4.5 hours but there is shade. Does that reduce the 4.5? You will need
5 hours to bulk charge + 2-4 hours for absorb.
You are light on charging, and don't forget your huge inverter is potentially a fire hazard.
Check my calcs
So if I purchase 2 more of these panels and the higher capacity mppt charge controller, I should be able to absorb more energy to be safer.
The next project I am thinking about is to change the heating elements in my hot water heater to Missouri Wind and solar 200 watt heating elements instead of the 12,000 watt (i think) elements, put a timer on the hot water heater so it only comes on for a short time in the morning for a shower and then shuts off for the whole day. I figure the water heated up in the tank will be luke warm by the end of the day. https://www.youtube.com/watch?v=iGCMwsDYmAw I may even switch over to one of those tiny refrigerators instead.
What do you think about these ideas? Maybe I will be able to cut consumption significantly if I do these things.Leave a comment:
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