Going off grid

I realised that it was a bit pointless checking how much current the panel was producing after dark, and since I have a RaspberryPi doing the work (via an Arduino) which is connected to the battery, it is likely using more energy processing all those reads/writes needlessly.

I had tried using a simple cronjob to control when the solar sensing service should start and stop, but wasn't happy that in these short days, it was going on far too long.

So, @davea and I did a little hacking on the script with PyEphem and python-crontab, and the result is quite pleasing; as of this morning the script figures out when it should stop and next start, on startup, writes the times to the crontab and then goes about its business. At end of civil twilight (sunset), the service is stopped, and will be started again in the morning at start of civil twilight (sunrise).

NB: this post is from ages ago, forgot about it sitting in drafts!

I can buy parts on ebay, but when it comes to wiring, I’m clueless.

#renewables #solar #GoingOffGrid

Fortunately I know a man who does have a clue. So, here’s a quick what’s-what, and some top-tips. Disclaimer: this is in no way expert advice (from me); Anything relayed on this blog should be treated as amateur comment.

The first, perhaps obvious point, to note is that the panel is producing electricity. Therefore, you should treat the cable connectors as live.

When wiring the panel up, it is important to do components in the correct order. In our case, this is what we did:

Always put both pairs of connectors on the cut, stripped wire-ends before connecting them to any components on either end.

Put short lengths of wire on the 6 (3 pairs) of connectors on the charge controller, so that you can quickly connect/disconnect the entire system should you need to.

Always put the covered (i.e. female/’boot’) connector on the end of the wire that would be carrying power - i.e. on the end of the wire that goes to the battery, to the panel and from the load output of the charge controller. This will help prevent you accidentally touching two sides of a circuit together. The exposed connectors therefore go on the charge controller inputs for the panel and battery, and on any devices that you will connect to the load output of the charge controller.

Connect the battery to the charge controller. This is so that the controller has somewhere to dump power when it gets connected.

Cut the wires that connect the panel to the charge controller before connecting them to the panel. This might sound stupid, but one could easily attach the in-place panel to a coil of wire, run the coil to the charge controller and then clip the wire where needed - clipping across the positive and negative wire while connected to the panel would make a circuit and could damage you or the panel!

Attach the panel to the charge controller next.

Finally attach any load to the charge controller (see next post!)

I finally got all the bits I need to go #offgrid. Well, mostly...

In this post I'll document all the (basic) equipment, and rough costs.

First of all a big thanks to Chris Elsmore for his help, advice and various electrical parts!

The solar panel

I went for a 100W solar panel, made by a British company called 'Biard'. The hope was that it was made in the country, and so had a reduced footprint (there is nothing on it that says 'Made in China', but I have yet to contact the company and ask).

It measures 1.2m by 0.5m, is really thin (though the edging adds about 3cm) and weighs 8kg.

I got it on Trueshopping's ebay listing, and it cost £119.00.

The battery

It's crucial to get the right battery - a regular car battery won't cope well with the variable charging and 'deep cycling' (being run down a long way, then charged). I could have done a bit better here, as the battery I ended up getting is OK for starting cars too (and thus not optimal for deep-cycling) -- I'm not totally sure how all this works out yet, but basically, 'leisure' batteries are good, car batteries are bad. Higher AH (Ampere-hours) rating is better, in case of long periods of overcast days!

Mine was a Numax 110AH from Starterbatteries (on ebay). It came down from Glasgow, which I only realised after ordering, so not the most carbon efficient purchase ever!

I'll write more about this in the future, but it's worth noting that lead-acid batteries might seem fairly awful, but lead being lead, is highly recoverable (and desirable to do so, because it's worth a lot), so they are quite recyclable. It also came with a 3 year guarantee.

The battery, with postage, cost £84.04.

Voltage Regulator

I picked up a Victron BlueSolar 5A charge controller from Alternative Energy Store on ebay for £28.59. It's pretty basic, but terribly important. It prevents the battery from over-charging, cutting off the power from the panel if it becomes full, and does some clever stuff when a load is being drawn (e.g. by an attached charging device).

Connectors, etc.

Chris supplied the 12V electric cable, and connector ends. He already had a cable crimp too, so cost here was nothing. An idea of prices, though:

Cable = £20.85

Connectors = £2.39

Crimp = £3.09

The panel came with MC4 (waterproof) connectors on the leads, so I bought another set from ebay to connect the 12V wires to the charge controller. They cost £2.38.

Cost

Total (actual) cost: £234.01

With cables/connectors/crimp: £260.34

So it cost a reasonable amount, but the panel should last for at least a decade, with good care, and the battery is recyclable (and can probably be sold for scrap). I expect the voltage regulator should continue working if well cared for.

My first full day logging the current output of my #solar panel.

#GoingOffGrid

A few patches of cloud and sub-optimal positioning leave a few gaps here, but hey, it's working! :-)

Step 1: out with the old (inefficient), in with the new (efficient)!

I guess this is the first and most simple way to improve energy efficiency. Simply changing these light bulbs makes a huge difference. There are 12 here, and together their power ratings add up to 680W. The replacements add up to about 100W, so already a great reduction in energy usage. Of course, careful use of the lighting will also help. One day all rooms will have smart lighting that knows when you're about to enter and have made your exit (but probably not in my flat, sadly)!

OK! After a bit of Nanode failure, @elsmorian has put together a simple Arduino sketch that pushes data to Cosm ("The Internet of things").

#emfcamp solar geeks - the storage. This is @elsmorian's choice of storage.

It's a 12V deep cycle lead battery, with a capacity of 95Ah (ampere hours) from www.tayna.co.uk. To explain the capacity, briefly (much for my own sake of memory!) - the voltage output is constant at 12V (pretty much, anyway- it's a bit more when fully charged and a bit less when near empty): so, this could (theoretically) put out 1 amp for 95 hours.

And what the heck does that mean?

It means it could power a MacBook pro for 19 hours.

MBP draws about 60watts.

Amps * volts = watts, so:

60 (watts) / 12 (volts) = 5 (amps).

So the MBP draws 5 amps.

95 (amp hours) / 5 (amps) = 19 (hours).