I sized my system for 16 panels with 2 Classics and a MagnaSine 4448. Immediately on finishing the system I saw how exactly the panels lined up with my skylights and added 6 panels which currently provide DC hot water. The system works but it can be better.
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Problem 1: The 20-gallon hot water system is OK for me for 3 seasons but not so great in the winter or with guests here in vacationland. I don't expect to get the rated Vmp 97.8 and Imp 18.7, but what I get now is 108V at 11A. That's under 1200 W from maybe 1800 W.
Problem 2: The MagnaSine dims the lights when any appliance starts. 'Fridge, water pump, etc. IDK if this is unavoidable or if other inverters are able to react more quickly to large loads starting up.
Complications: The inverter is not really large enough for a larger AC water heater. There is no space for wiring or breakers to add a third Classic to charge battery with the lowest 6 panels. Even removing all the boxes to the left of the Classics, it just won't work. I COULD put a Classic elsewhere and have breakers for 1 function spread around 2 places but I'd rather not.
Misc questions:
Does anyone use a hybrid water heater or heat-pump water heater in a cool basement? Temperature is about 7C or 45F now and it's not even cold outside. The basement walls are R14 insulated blocks with about 30 cm or 1' of wall above grade. The biggest air intakes for the whole house are in the basement which will soon be very cold air.
Has anyone run a spectrum analyzer around the MNSSR rapid shutdown devices? My roof is currently RF quiet and I'd like it to stay that way. I assume that the large currents are all DC and these include small receivers. How wrong am I? Is the data or trigger on DC wires or is it broadcast RF?
The One looks like a great option. The 3 MPPT circuits are a good match to my 3 rows of panels. I won't buy it because it relies on the cloud.
The Barcelona would work but I suspect it would be less efficient. I'd have to combine the top 2 rows into one circuit at Voc 324. The shading in winter works up from the bottom rows so this will be less efficient than now. I can change the bottom row from Voc 121.5 to Voc 243.
Any other ideas or recommendations?
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Solar DC hot water:
You may recognize the prewired system to the left in the pic. I will explain the column on the right. All wires that might carry unregulated solar DC are 10 AWG in orange NM. Wires in yellow NM carry only 120V AC.
The yellow NM to the top of the water heater powers the thermostat in the water heater.
The thermostat turns on and off power to the yellow NM from the lower box on the water heater. This yellow NM controls a DC contactor in the box with a clear front cover. The DC comes through the Midnite breaker box on top.
The contactor provides DC to the right outlet where the plug on the orange NM is currently plugged in.
For hot water when there's no sun, I can move the plug to the outlet on the left and turn on the 1-hour timer above it. This will provide 120V AC from the yellow wire coming up from the thermostat. This way I can use battery or generator for hot water.
It works. Really. I have reliable power all the time and hot water most of the time. The heat here is a wood-fired cookstove so there's a 3-gallon pot on the stove for 6 months.
But it could be better and I want a larger water heater.
Thanks.
Dave
I quickly read your post and didn't take in all the details right now .
But you asked if any one had a hybrid hot water system. I built one , and another system that could heat hot water but was on a space heater.
I don't have any experience with heat pump water heaters but they are probably good.
My hot water heating is a bit limited in the winter since my water heater is outside so I have to drain it after use so it won't freeze up. I have gotten it so that is a fairly easy task.
One system uses direct pv to bottom heating element. I put a smaller water heater on top with an AC heating element and circulate water to it. That way I can have two heating elements without filling bigger hot water tank all the way .
The second system which is not to hot water heater but could be - is bypassing pv around the controller using a contactor .
I have videos about these . Take note that I used an igbt on first system to handle the pv voltage but since have replaced it with a dc contactor like shown in the other video. There is no need for an igbt if you aren't going to pwm it .
https://youtu.be/s7trVpHLts4
https://youtu.be/1Vjfv_GMH94
Larry
Thanks for your response.
I don't think that optimizing the DC hot water is the best way to get more hot water. While hybrid heat-pump/resistance water heaters need much more power, they use less energy for the same or more hot water.
I formerly had 2 flat-panel water heaters, a heat exchanger, and large tank. I am happy to not deal with anti-freeze, plumbing, bleeding, etc., any more. That system also worked OK, but PV hot water is much less hassle.
Adding the lower 6 panels to a charge controller for the batteries would increase that array by 37%. I would then have more AC electricity for hot water. This requires a larger inverter.
I might look at optimizing DC hot water but only after I thoroughly explore enlarging the available AC power and energy.
Thanks,
Dave
Dave,
The way I looked at it , the direct DC to hot water heater can be more efficient. You are not loosing the efficiency in the controller and inverter. Of course if you have those devices in a space you were wanting to heat anyway - then that is not any efficiency loss ( other than the wear and tear on the devices).
The other way I looked at it for my system, is that if the batteries are full without any loads, then that pv isn't doing much so I may as well use it to heat.
I looked at your original post again.
I think you want a larger volume of hot water. Using a hot water heatpump is probably your best option since it is supposed to heat more water for the same amount of power used in resistance heating.
There probably aren't any other options for electricity . The other solar option is to use collectors to directly heat hot water , use a large tank to over heat that water if possible to act like a battery, and then mix it with water to get the right temperature. Or if you reheat it later if the water is not as cold as it originally is from source, then you save a lot of energy there too and get engergy from your hot water battery bank.
Larry
just a thought I have considered, add another small hot water heater as a preheat before the existing one. Use that as your dump load.