Help thinking through solar and battery options

mmmmikey

Hi Nick.

I'm on an Economy 7 tarriff, paying about 5p / kWh off peak and 20p / kWh peak. I'm just about to have a smart meter installed, at which point my FIT export payments will be metered, and at this point I'll get about 5p / kWh for export - i.e. much the same as I pay off peak. This means there's no advantage to me in storing electricty for use during the off peak period - I might as well sell any surplus when it's generated and buy anything I need off peak as I need it.

So the battery is only wothrwhile to me if I use the power during the peak period. Without the battery, I use ca. 1000 kWh / year of peak rate electricity and the 4 kWh battery is big enough to deliver this. It's worth remembering that you can potentially get more than 4 kWh per day from this as any discharge during the day when the cloud goes behind the sun is quickly recharged when the sun comes out again.

Having said all that, this logic may not be relevant for many people, and the economics of the bigger system are probably more favourable for most.

On a topical note following yesterday's power cuts, worth noting that the PowerVault is one of the few battery systems that has frequency response built in, which is why EDF are offering the grid services contract. The idea is that when power generators fail and the frequency drops (which is what happened yesterday) the battery switches in almost instaneously to help rectify the problem. It is this functionality that makes grid services so valuable to generators like EDF.

If you shop around, you'll see that you do pay a premium for the PowerVault solution but I was happy to do that because of the long term potential of grid services and frequency response. The quality of PowerVault's service was unknown to me when I made the purchase, but if I'd known how good it was that would have been another good reason to take the plunge.

Hope this helps, Mike

Solarchaser

I'd suggest looking at rec twinpeak panels.
Though I believe the highest is 300w, which is what I have.
They are built with the contacts in the middle and a built in diode specifically to deal with shading issues, they are essentially two half panels rather than the normal full panel.

I cant compare them to the mini panel solution, but they would work out somewhat cheaper.

As an aside, that seems awfully expensive imo, those panel prices seem more in line with 2013 than recent days where the prices have reduced somewhat.

Though that's based on what I see north of hadrian's wall

Nick6659

Thanks Mike - what you’re doing makes sense. I’m in for an interesting chat with EDF/Powervault consultant. If the stored electricity in the battery can be called for in circumstances such as yesterday with the frequency response built into the battery (don’t really understand that by the way,) then it underlines my main concern with the grid services idea - who has first call on the battery, me or EDF? Cheers Nick