diy solar

diy solar

Newbie looking at setting up solar for home possible off grid use.

Danjwilko

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Joined
May 22, 2022
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41
Hi guys been a while, now I'm uk based and with the second almost doubling of electric prices in less than a year really we can no longer put off getting solar.

We use (going off the latest bil)l 2600kw per annum, current forecast for this year is 2300kw so we've cut it a little converted all bulbs to Led and switch all appliances off TVs, tv boxes, computers and studio equipment.

Previously the usage per annum of 2600kw cost around 2 years ago was £360, were now paying £900 and with my latest quote for October £2300 (co worker has gone from around £3k to £13k).

Ive done the energy audit and ive got to say it was a mare as the loads on some of our items fluctuate massively ( dishwasher, cooker, washing machine, tumble dryer, pc's and studio equipment ).

Any way the results:
Full load wattage: 10569.29
Full load Whr: 6929.29

We literally have a American style fridge freezer, router and switch running all day, oil heating in the evening and cooker for possibly 30-40 mins daily, the rest of the appliances are 2-3 times a week (tumble dryer sparingly). Going off the smart meter we average 4kw usage on days without washing/dishwasher usage 6kw on wash days.

Does the energy audit sound about right or have I cocked something up?

If it looks oldish what am I looking at realistically? assuming a 48v system and a inertor that is capable of the full load wattage?
Since putting back into the grid is no longer paid by elec companies would it be worth going completely off grid? If so what size battery array would I be needing? we have a lot of wind here too due to open fields so adding in a couple of 1000w wind turbines isn't an issue.

All help and input is appreciated.
 
2600kWh/365days = 7.1kWh/day, which is somewhat more than what I myself am consuming. With just lights, TV, a computer, and the refrigerator running, I find myself consuming ~3.5kWh a day. 7X that much on irrigation days, powering the submerged well-pump.

So, 7kWh sounds about right. The cooker you mention, that's an electric stovetop? Anything related to either heating or cooling is going to be a BIG item to power via solar. The first think about replacing that with something gas powered. I have a little tabletop propane stove that I powered with a 20 liter barbeque tank. It lasts weeks with regular usage.

Winter weather is what is going to get you. 7kWh in sunny summer weather is easy. Maybe 1500W of panels is all you need for summer. Winter though, or cloudy weather in general is going to be far tougher. Assuming you only get only 10% output on a rainy day in winter that means ~9000W of panels. I say that because I have 4500W of solar, and I can make ~3.5kWh on a cloudy/rainy day.

Battery-wise, You could inch by with golf-carts at 48V. Assume 250Ah X 48V X 50% usage = 6000Wh. Maybe two days of autonomy if you shift into serious conservation mode. With L-16 sized batteries, twice as long. So, for winter, it's all going to depend on how many watts you can scratch out with however many panels you can put up?
 
2600kWh/365days = 7.1kWh/day, which is somewhat more than what I myself am consuming. With just lights, TV, a computer, and the refrigerator running, I find myself consuming ~3.5kWh a day. 7X that much on irrigation days, powering the submerged well-pump.

So, 7kWh sounds about right. The cooker you mention, that's an electric stovetop? Anything related to either heating or cooling is going to be a BIG item to power via solar. The first think about replacing that with something gas powered. I have a little tabletop propane stove that I powered with a 20 liter barbeque tank. It lasts weeks with regular usage.

Winter weather is what is going to get you. 7kWh in sunny summer weather is easy. Maybe 1500W of panels is all you need for summer. Winter though, or cloudy weather in general is going to be far tougher. Assuming you only get only 10% output on a rainy day in winter that means ~9000W of panels. I say that because I have 4500W of solar, and I can make ~3.5kWh on a cloudy/rainy day.

Battery-wise, You could inch by with golf-carts at 48V. Assume 250Ah X 48V X 50% usage = 6000Wh. Maybe two days of autonomy if you shift into serious conservation mode. With L-16 sized batteries, twice as long. So, for winter, it's all going to depend on how many watts you can scratch out with however many panels you can put up?
Ah that's ok then, were a family of 4 and have oil central heating (not going back to storage heaters ever) as mentioned I changed the bulbs in the house to all led brought the consumption down a ton, the living room, landing and kitchen lights on in winter was close to a 1kw by itself combination of 40w and 60w bulbs.

The cooker is a electric one, we haven't got a gas line hence the oil heating, I can look into gas I know my father in law was complaining about the increase in prices of the bottles literally last week.

Solar panels wise I was looking at used but have just seen Renogy 175w panels for £124 normal price £175 considering buying up as many as budget will allow (minus inverter and batteries). Not many sellers have large panels in all out of stock.

Ive also got a chap I bumped into selling 2 280w panels sun tech ones but no idea how much he wants for them yet, apparently new and lot over from an install pretty sure they are 39.2v open circuit where as the Renogy ones are 22.9v.
 
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Expat here.
Just to put this into perspective between your part of the UK and my part of the USA, Florida.
I used 11,327kWh last year at a cost of $1346.
I wish I could persuade my family over there to switch to solar electricity but more of their energy bill comes from gas heat and hot water.

Buy the best PV panels you can find, way more output for the same size.
 
I think I'd want to check with somebody local about the sun situation. I'd be afraid that I could invest all that money and find that between the northern location, winter insolation, and overcast weather there'd be no sun. And depending on your location you might even have snow and ice to clear off your panels.
If you look around your neighbourhood do you see much solar in the UK?
 
I saw far more of it in the UK than I do in Florida !!!!
Got to agree, most of the local bungalows and large houses have them.
We actually live around 2 miles from a huge solar farm- they also compliment the solar with 2 large turbine.
With the recent increases and the two expected (October 80% and January, let alone the one in April they are now on about) they or anybody with solar are going to be laughing.

Price cap has gone from £1971- £3549
(October expected), January circa £5600, and then April around £7700 according to latest research. Looking grim.

So my electric has already doubled, expecting an 80% increase, call it another 57%(approx rounding) increase topped off with 37% increase.
Quick maths to compare cost going off the forecast.
Current yearly cost £900 80%- £1620.
£1620 57% - £2543.
£2543 37% - £3484 for 2600kw of usage.
Which is insane when we used to pay circa £440-50 one year ago.
 
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Just as an update, found a local company selling Ja solar 380w panels so going to order 4, just need to sort the inverter, (not sure if to go all in one or separate components) and at least one 100ah battery for now and see how things go.

I’ve measured up for a ground based platform with the possibility of utilising 3 south facing roofs in the future pending inspection (old building).

Now just need to sort out cable routing.
 
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Four will be fine for summer. With maybe 5 sunhours per day in June, you are going to make 7.5kWh of power. In the winter though, expect to see 150W coming off your array. Twelve of those would make you 3.5kWh/day in winter in the rain.

Lots to sort out besides just cabling. Looking on the web, that panel appears to put out ~9.5A at 39.8Vmp with a Voc of 48.05V. First, you need a charge controller that can handle ≥150V. You want to wire your panels in series, but you can't have the series voltage so high it fries the electronics.

Most AiO units have a max Voc starting at 145V, so you can wire two of the 380s in series for ~80Vmp. The Voc will be 96V, which will easily go above 100V on a cool, not even frosty morning. If you want all four in series, you need a controller that can handle 250V. Wiring the panels 2S2P will work for most 150V+ units.

The inverter should be scaled to the loads you want to run on it. Keep in mind that most appliances running on an electric motor will have a starting surge 3-4X the running wattage. Most high frequency (HF) AiO units have little or no meaningful starting surge capacity, so pay careful attention to that. Transformer based units have far higher surge capacity. Look at EVO, Magnum, Outback, and Schneider for quality low frequency (LF) inverters.

Pay attention to the background watt consumption with the inverter just being left on. A general rule of thumb is the lower the background consumption, the higher the quality of the unit. Another number is the THD, total harmonic distortion. So, shop for starting surge, background consumption, and THD was evaluation items.
 
Four will be fine for summer. With maybe 5 sunhours per day in June, you are going to make 7.5kWh of power. In the winter though, expect to see 150W coming off your array. Twelve of those would make you 3.5kWh/day in winter in the rain.

Lots to sort out besides just cabling. Looking on the web, that panel appears to put out ~9.5A at 39.8Vmp with a Voc of 48.05V. First, you need a charge controller that can handle ≥150V. You want to wire your panels in series, but you can't have the series voltage so high it fries the electronics.

Most AiO units have a max Voc starting at 145V, so you can wire two of the 380s in series for ~80Vmp. The Voc will be 96V, which will easily go above 100V on a cool, not even frosty morning. If you want all four in series, you need a controller that can handle 250V. Wiring the panels 2S2P will work for most 150V+ units.

The inverter should be scaled to the loads you want to run on it. Keep in mind that most appliances running on an electric motor will have a starting surge 3-4X the running wattage. Most high frequency (HF) AiO units have little or no meaningful starting surge capacity, so pay careful attention to that. Transformer based units have far higher surge capacity. Look at EVO, Magnum, Outback, and Schneider for quality low frequency (LF) inverters.

Pay attention to the background watt consumption with the inverter just being left on. A general rule of thumb is the lower the background consumption, the higher the quality of the unit. Another number is the THD, total harmonic distortion. So, shop for starting surge, background consumption, and THD was evaluation items.
Appreciate the info as always, I will be expanding once stock/funding allows, as I was budgeting for the inverter/charge controller, cabling and ancillaries first, then expanding the system.

The solar panel model is the JAM60S20 380/MR Mono premium Half-cell black short frame QC4, figures are:
~8.78A at 32.72Vmp, Voc of 39.14.

Charge controller wise I was looking at the victron 150/35 originally then the 250/85 but seemed expensive as an option. would the 250/85 suffice for all 12 or would I need multiple?

The chap who was going to sell me his panels has a 4kw system and used a growatt 3600 and seemed to highly recommend them, again my only comparison so far is a Victron (seem to be the main brand in the uk) which was circa £1600 for a 6000va 48v system which I didn't think was too bad.
Il have a look into the other brands mentioned
Cheers again.
 
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The solar panel model is the JAM60S20 380/MR Mono premium Half-cell black short frame QC4, figures are:
~8.78A at 32.72Vmp, Voc of 39.14.

Charge controller wise I was looking at the viltron 150/35 originally then the 250/85 but seemed expensive as an option. would the 250/85 suffice for all 12 or would I need multiple?
Simple math problems. The second controller, the 250/85 is a better choice for you. 85 means it's output can go as high as 85A. Assuming your 48V battery starts charging at ~50V, then 85A X 50V = 4250W of panels. If you apply an 85% derating, like I usually do, that becomes 4250W/85%= 5000W. So, under normal routine use, you could wire together as many as 5000W of panels.

250 means the highest incoming voltage the unit can ever tolerate is 250Voc. REMEMBER that the voltage goes up as the temperature goes down. A series string at just 223V at room temp is likely to pass 250V right around freezing (0C).

Let's say you bought 16 of the panels mentioned above. You could wire 4 parallel strings of 4 panels each (written as 4S4P). Four in series would give you 131Vmp at 8.78A. Four in parallel would give you ~35A at 131V, or ~4600W. The controller transforms the high raw solar voltage to ~78 charging amps. (4600W/50Vcharging) X 85% = 78A. That is less than the 85A limit of your controller, so that works.

Suppose instead you bought 18 panels and you tried to wire them 6S3P? 39.14Voc X 6 panels = 234.8Voc, but at freezing, the number will raise up to 234.8Voc X 1.12 = 263V, so that would fry your controller.

Suppose instead you bought 20 panels but wired them 5S4P. You'd get 39.14V X 5 panels = 195.7Voc, and at freezing that would go up to 195.7V X 1.12 = 219V. Voltage still looks OK. The amperage though would be 8.78A X 4 strings = 35.1A at 195.7V. That comes out to be 6873W. (6873W/50Vcharging) X 85% = 116A, significantly higher than what your controller can handle. It might not fry it, but any amps over the 85A limit just get clipped off and disappear.

With the lesser capacity 150/35 unit, most likely you can only use 6 of the above panels, in a 3S2P configuration. Maybe eight but you would have to wire them 2S4P to keep them below the Voc limit. You might point some strings SE and other SW to better utilize the higher amps coming in.
 
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