Down to the wire: Understanding

electrical considerations

The transmission wiring isn’t the only wire in

your system. Small wind-electric system wiring

is different from ordinary home wiring, and even

electricians get puzzled sometimes. The biggest

difference is that there are multiple sources of

electrical energy in the system, working at mul-

tiple voltages and frequencies or even with DC,

which has no frequency.

Every circuit in the system needs to be designed

with a view to the maximum voltage and the

maximum amperage (current) that may arise

in that circuit. In some cases, these are easy

numbers to find — for example, a 48-volt bat-

tery system probably won’t greatly exceed 60

volts DC. But the maximum amperage that a

wind turbine will generate can be a lot harder to

establish, so you may need to leave a bit more

headroom in some cases. The rating of a piece

of wire, a diode, a fuse, or even a connection in

the circuit has to meet or exceed that rated volt-

age or current for that circuit. A higher rating is

always good, and in many cases it’s prudent to

add a factor of safety to the rating. Such factors

are enshrined in the code for many situations.

And in most cases, a higher rating will add to

the efficiency and reliability of the system.

Wiring also affects efficiency. For example, the

wires need to be thick enough to prevent wast-

ing energy, even if that waste is only a gentle

warmth in a very long wire. It’s important to

look at the voltage drop in long wire runs, espe-

cially at low voltages where this voltage drop

becomes a significant percentage of the circuit

voltage. If you lose 10 percent of the voltage,

then you lose 10 percent of the energy that the

wires transmit. Where the amperage is likely to

be very high (such as between a 12-volt battery

and an inverter), you should keep the wires as

short as possible and choose the thickest you

can afford.

If you do any of your own wiring, take care to

read the equipment manuals carefully. They’ve

been written specifically to help with the idio-

syncratic problems of small wind-electric sys-

tems. They often give detailed guidance on wire

sizing and on safe installation.

And by all means, ask electricians to help

you with the wiring of your renewable energy

system. They’ll make a tidy job. But don’t nec-

essarily expect them to have all the answers,

even when they sound confident. Ask for a

design document that shows how the various

wire sizes and fuses were chosen. Ask for clear

instructions on how to shut the system down

and isolate parts of repair or maintenance. A

carefully planned system is likely to be reliable

and safe in operation.