OT solar panels

[alan_m]

On this group I've often seen posts about solar panels and how much money they have made or saved the person(s) fitting them - possibly due to excessive FITs payments. The money saving expert pages has an article on what may be the current situation.

A few points....

Break even = 24 years if electricity prices fall by 40% Break even = 17 years with current electricity charges Break even = 13 years if electricity prices rise by 40%

These figures are assuming none of the previous high FITs payments and only feeding back into the grid at 3p to 7p per kWh (variable).

These days, with a new installation, the biggest savings will be for those who use all of the generated electricity themselves which may benefit more those who are at home during the day. BUT can a household actually use all the electricity generated on a long, clear sky summer's day?

They mention "savings on your bill" from the suppliers but for me there are no savings until you break even on the installation costs. However, going green is not necessarily about saving money!

[Theo]

It depends on your usage pattern. If you have storage, like a house battery or an EV, probably. If you don't, it really depends what loads you can run while generating. Diverting it into your hot water tank is a bit of a copout, but better than nothing.

Any of these are much better than the export tariffs.

On my todo list is a single garage roof replacement. It'll take 4 panels, mounted on eg these buckets (no fixing to the roof, just ballast):

Cost for parts about £1200-1500 for a 1.6kW system, uncomplicated DIY install (no scaffolding etc). If it displaces current power usage, payback is within 3-5 years.

A separate paper quote for an installed system from 'Solar Together' group buying scheme:

10 panels facing west + inverter + shading optimiser (£400) + extra scaffolding for complicated roof (£400) = £4978. (it says estimated generation is 2732kWh pa, but not the kWp of the array. Most panels are 330-400W per panel these days)

Theo

[Fredxx]

Yea, right. Your usage pattern must be different from mine. If you only use your EV when everyone is tucked up and asleep then you may have a good idea.

[Fredxx]

Yes you did, you said you could charge your car using solar, I can assure you that can only happen in daylight.

[Paul]

My brother-in-law has a lot of panels and no battery, and this is made possible by the local power company. They have a generous FIT. The payback is almost attractive. He is "extreme rural".

If you have a FIT, then you don't need batteries. The FIT is all you really care about. You don't give a "green damn" if the FIT is generous.

If you don't have a FIT, then it's a matter of "do I need a moderate number of batteries, or a lot of batteries?". Seeing as using the lekky yourself is better than giving it away for 3p.

And as soon as the word "battery" appears on the spreadsheet, the project is dead dead dead.

You cannot fully recharge a 100kWh BEV in one day, using a roof full of solar panels. A home battery only need store a day of output from the panels, so you can transfer the charge to the BEV (at night) and get some benefit from it. You would use Lithium Cobalt (5000 charge cycles) or Lithium Iron Phosphate (7000 charge cycles), rather than lead-acid which has fewer charge cycles.

Solar Panels ----- 20kWh transfer ----> 100kWh BEV, refill battery at night

You don't fill the 20kWh battery full. You fill it to 80% or 16kWh, to extend the lifespan.

It might take six days of solar, to fill the BEV from empty to full (especially so in winter). And in winter, the Lithium battery has to be stored in an insulated area so it stays above 0C. You can't just leave the battery solution in the woods. Only lead-acid batteries can be left in the woods, and they suck from a spreadsheet costing perspective.

Where ever the Lithium batteries are located, the buildings should not be "particularly flammable". If you know what I mean. Ask an insurance company what they think about BEV fire risk (as a "policy adder").

Paul