Can we talk about a BASIC UNIVERSAL simple PV kit for preppers.

[Skvez]

So lets look at a small system

Radio (listening) 12V 0.1A 2 hours a day = 2.4Wh/day
LED lights 3W 3 hours a day = 9 Wh/day
Rechargeable batteries, say one set of 4 each day. 1.5V, 2.5Ah, 4 batteries = 15Wh but charging is probably only about 50% efficient so 30Wh/day
Kindle is tiny say 1Wh/day (daily average given that you probably only charge it every couple of weeks)
Typical self discharge of a 110Ah battery 2Wh/day
Total daily needs: 44.4Wh

My 100W solar panel under test for 2011 produced an average of 93Wh/day but before you think "Great I only need 50W of solar panel" you need to consider that between November and January it produced an average of only 14Wh/day suggesting you need closer to 300W of solar to get through the winter (or a lot of battery to get you through the winter months).

[Nemesis]

Just a quick question regarding panels. Are they future proof in the respect of you being able to add more panels as the price falls over the next few years or does the technology also change meaning that the older and newer ones have to run on separate systems ? Put another way, would a panel you bought 10 years ago still work with a modern setup ?

At the moment I only have the freeplay type ones for charging small devices, but will look at solar in the new place

Good question already in both the amazon build and the build comparison I made for TOF there is a problem, although I made the suggestion to TOF that the 10A regulator is not enough and she should consider paying more for a higher one in this case I said 30A.

What we need to know is the watt panel to regulator math, which is:


5 amp = 60 watt 10 amp = 120 watt, 30amp = 360 watts.

Regulators can be chain linked, anyway maybe Skev can correct this math, and explain chain linking of regulators, he knows more about this stuff, and I have to burn in come fire cement now, so bit busy right now.

I would advise having a few spare regulators, for solar preps.

But yes you can add panels to the build years later, just as above your need to chain regulators depending on total panel watts.
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[Skean Dhude]

It is electricity it is generating and they can be added together. Just need an interface and a way to store it. The regulators should do that fine.

[Nemesis]

The regulators should do that fine.

As long as you know how to join them and there max limit.

[Skvez]

In order for the regulator to know the state of the battery, every so often it stops charging briefly and reads the Voltage of the battery.
If you have multiple regulators feeding the same battery bank what can happen is regulator A stops charging and reads the battery but sees the PV Voltage from regulator B rather than the actual state of the battery and believes that the battery is fully charged and stops charging.
I'd advise you oversize your regulator, you can add more panels and more batteries but I don't advise trying to feed multiple regulators into the same battery bank.
Of course you can get multiple regulators to feed multiple (separate) battery banks. That gives you redundancy and we preppers do like redundancy. It a little more awkward when it comes to loading as you need to distribute (or switch) your loads between your two or more battery banks.

[Lightspeed]

So lets look at a small system

Radio (listening) 12V 0.1A 2 hours a day = 2.4Wh/day
LED lights 3W 3 hours a day = 9 Wh/day
Rechargeable batteries, say one set of 4 each day. 1.5V, 2.5Ah, 4 batteries = 15Wh but charging is probably only about 50% efficient so 30Wh/day
Kindle is tiny say 1Wh/day (daily average given that you probably only charge it every couple of weeks)
Typical self discharge of a 110Ah battery 2Wh/day
Total daily needs: 44.4Wh

My 100W solar panel under test for 2011 produced an average of 93Wh/day but before you think "Great I only need 50W of solar panel" you need to consider that between November and January it produced an average of only 14Wh/day suggesting you need closer to 300W of solar to get through the winter (or a lot of battery to get you through the winter months).

Excellent analysis and real life based advice.

Thanks Skves, this was very useful.

[Skvez]

I just realised I forgot to include the losses we experience because charging the lead-acid battery isn't 100% efficient.
It's hard to put a value on this as some of our loads are applied during the day when they can run directly from the solar cell with no (little) efficiency loss.
Lets take a guestimate of 70%
So our 44.4Wh/day of load needs ~63Wh/day of solar

[Nemesis]

[Skean Dhude]

Based on what I have read I'm a bit puzzled as to how the panels added to people houses are priced in the tens of thousands. I can understand a cost involved in connecting to the grib but for everything else it seems to me someone is raking in a load of cash.

Does anyone know what is involved in connecting an existing panel of panels to the grid?

[NorthernRaider]

Grid connection, it has to be planned and costed, most have to connect to the 11,000 volt lines and the grid can chage a lot on the local or inteligent grids, then profit, liability insurance, scaffolding, VAT, staff costs, maintenence charges etc.

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Forgot structural survey to ensure the roof can take both the weight and the loading from wind trying to lift the panels