Solar panels to Inverter. Where to run the cables ?

Brian99_2

15 kw sounds like a damn big installation (EDIT I see now you had kWh units, not kW)

For average 2kW system, inverter wastes about 180 watts of heat.

In a few years, when a million people have it, that is 180 megawatts of heat leaking from inverters !!

So now is the time to start planning to use it. For most of the year it would be welcome in the cooler Northern side of the house.

zeupater

Brian99 wrote: »

15 kw sounds like a damn big installation ? Most houses will be 4kW max.

For average 2kW system, inverter wastes about 180 watts of heat.

In a few years, when a million people have it, that is 180 megawatts of heat leaking from inverters !!

So now is the time to start planning to use it. For most of the year it would be welcome in the cooler Northern side of the house.

Hi

A 4kWp system will likely produce 15kWh to 25kWh in a day in the height of summer .... in the depth of winter the same system will likely produce between 2kWh and 4kWh in a day ....

Another way of looking at it is that the 2kWp system you mention is likely to produce somewhere around 1800kWh of electricity in a year so the 9% figure you used would result in 162kWh of heat, of which around 70% will be in the six months of the year when heating isn't required .... this means that about 50kWh of heat would be available over the entire winter .... that's around 275Wh/day (50/182), or around a 25W (275/11) contribution to heating during daylight hours, not much more than an energy saving lightbulb, or the equivalent of a quarter of what the average adult provides whilst sleeping ....

What I'm attempting to convey is that placing the inverter somewhere just to make use of the heat in the winter will not make much difference, remember, even the rough figures above are based on a 6 month heating season ... on days where heat is most required the inverter could be contributing absolutely nothing, but in the summer when you're attempting to keep cool in the North facing rooms you'll have a little more heat to contend with ....

Anyway, have a look at the specifications of most good inverters and you'll probably find that you could at least half the 7% to 9% inefficiency which you are basing the calculations on, so it's likely that, during the winter, the inverters in one million homes would only be averaging 1/15th of the heatloss you calculated, or 1/8th of the heat contribution of an adult body over the same winter daylight hours .... The real issue is to keep the inverter cool, place it where it's not likely to be damaged and where any transformer hum is unlikely to annoy you ...

HTH
Z

Brian99_2

Zeupater...Ooops, now I see your kWh not kW.

I've been seeing confusion in brochures and news items for years... now I've sinned myself LOL

You seem to live in a warmish climate ? Here in Aberdeen, its cool on the North side even on summer days, and its definitely cold there in Spring and Autumn. (I dont use masses of gas)

So I plan to have the inverter in the house (not loft) and towards the North. But the hum I need to ask about (for SunnyBoy).

The heat produced could warm a cupboard, useful for drying small things (OK musnt get too damp).

Brian99_2

"but in the summer when you're attempting to keep cool in the North facing rooms you'll have a little more heat to contend with ...."

In Aberdeen, those will be about 5 days in June... the other 360 days we'll benefit !!!

zeupater

Brian99 wrote: »

...In Aberdeen, those will be about 5 days in June... the other 360 days we'll benefit !!!

.... I han't realised that you were so close to the Arctic Circle ...

Regarding inverter hum ... if you're having an inverter with a transformer, which the SB1200 is, they can get quite noisy when working hard, if it's a transformerless one there will be far less noise ... but then again you wouldn't want one of those because they're more efficient and wouldn't help warm your house as much

HTH
Z

Brian99_2

Today I have almost zeroed in on an arrangement...

SunnyBoy in a large cupboard, in North facing bedroom. Easy to see, not too warm, (hums only during daytime).

From a real installer friend, I now hear that OUTSIDE cables have regulations... are expensive, with extra armouring.

BEHIND the plasterboard is also very tedious, messy, and fraught with regulations.

So I guess nearly everyone will be putting up with trunking through rooms (though one guy here said he has outside cable.)

Thanks for the excellent discussions here, we are all more prepared

Yut_Man

My cables are run outside the house in trunking.

Brian99_2

My installer doesnt recommend cabling outside. It seems much simpler on my house; but maybe there is more expense with tougher protection.

Brian99_2

YutMan.... Is your outside trunking made of plastic? or metal ?

I'm puzzled that my installer put me off ouside cables.

Maybe it's expensive; or maybe he's minimising the outside jobs up ladders in a Scottish winter!!

Yut_Man

Plastic. It not ideal im sure inside would be much nicer but it was such a easy run using the outside wall. Im sure its down to the location of the invertor, meter outside wall etc.