How to power computers from solar panels?

The garden office has got one entirely unused feature — a large roof! What better place to mount solar panels for an off-grid power supply …

These Sharp PV modules (ND-R245-A6) [PDF datasheet] are manufactured in Wrexham and (although pricing is very opaque) appear to cost around £250 per module. I would need three or four. Each module produces a peak of 30V, 8A (= 240W) although in reality I’d guess the voltage would vary wildly from 0-30V.

Inverters, the part which normally converts the DC and highly variable power from the modules to mains AC voltage, are expensive, costing likely as much or more than the panels themselves. As this is an “off-grid” installation, this is useless. It would seem to be better to use the power to charge car batteries.

The car batteries provide the smoothed 12 V supply which would be used to run servers and lighting.

So there seem to be two problems in the way: (1) How to charge the batteries. I think I need something like this? (2) How to power servers directly off 12V …

Update

As always, it becomes much clearer once you have the key search term, and the word in this case is caravan. Apparently people who own caravans, static caravans, narrow boats and so on are in precisely this situation, and there are special purpose charge controllers used for this (made by Steca, amongst others).

Here and here [both PDF] are two excellent starter guides for the self-builder.

Now all I need to do is to size my requirements and work out how to power a server off a 12 or 24V supply.

Garden office now mostly done

Outside:

Inside:

As you can see, I’m by nature an untidy person. Still it’d be nice for suggestions about what can be done about those cables!

Garden office – undercoat done

Inside there’s a ring for sockets and a lighting circuit. The windows and doors are pre-made double-glazed units.

Garden office – roof going on

Garden office – construction starts

The cabin has a double wall which will contain insulation. Shown here is the ring main for the four sets of sockets around the room.

Garden office – constructing the base

Also (not shown) they dug a trench down the side of the garden for electrics and network cables. We’re going to run some hefty armoured cable, plus two or three cat 7 network cables, covered with bricks and warning tape, at a depth of 18″ (mandated by building regulations).

Garden office

As some readers might know, I work from home, and have worked from home for about 12 years. However I’ve never had a proper dedicated office, just a corner of a second bedroom or a bit of space on a sofa. That’s about to change.

Tomorrow, work starts on constructing a real office in my garden.

Work already started (for me) about a month ago, when I took down a shed and jack-hammered a patio to bits:

Shifting the whole lot into two skips:

Resulting in this empty, mostly flat space (about 20′ wide and 16′ deep, damn you council for chopping that tree down at the back …):

To be continued …