SolarEdge ot Not?

[dpmiller]

If you exported that much, how much electric did you *use*?

[pdf27]

2 hours ago, dpmiller said:

If you exported that much, how much electric did you *use*?

Roof-integrated PV is surprisingly cheap. A ~10kW system would generate about 1100 kWh in April on my planned roof, and cost about £6k upfront in parts to generate 9300 kWh/year. Even at 5p/kWh that's £450 in export tariff a year, so £600 is a pretty reasonable guess for what it's worth in income/savings. Given that the cost is in the region of £100/m² and nice tiles are likely to cost at least £50/m², then a PV system which exports a lot starts to look very attractive for most self-builds.

[joth]

4 hours ago, dpmiller said:

If you exported that much, how much electric did you *use*?

Total consumption was 603kW, of which 288 was self consumption of PV.

PV total generation was 900kWh, of which 612 was exported.

(So exported about double what we imported)

 

April was only our second full month living in the house so not yet put a lot of effort put into implementing energy time-shifting (I only just built the immersion controller yesterday! Previously I was using a dumb timer switch) but I'm not sure we'll make a major dent on this as a good chunk of the remaining consumption is cooking and background load. 

 

 

 

Edited May 9, 2021 by joth

[SteamyTea]

26 minutes ago, joth said:

Total consumption was 603kW,

Obligatory kWh.

Unless you meant your mean power consumption.

[joth]

1 hour ago, SteamyTea said:

Obligatory kWh.

Unless you meant your mean power consumption.

kWh indeed, have a ?

[Fly100]

For Ref I have a 6kw System. In April :-

 

Produced 577 kWh

Self Consumption 480 kWh

Exported 97 kWh

 

I have an immersion diverter that uses spare generated Electricity to heat DHW. I ran the boiler once that month for DHW. We time washing and dishwasher running to solar production too.

 

May :-

 

 

Produced 913 kWh

Self Consumption 655 kWh

Exported 258 kWh

 

Boiler run 0 times for DHW

 

 

 

Edited June 8, 2021 by Fly100

[Johnnyt]

Those are very intersting stats Fly 100

I've taken a major plunge on our build, currently at first fix electrics stage but have opted for :

 

Solar edge  10020 kWp system

3900 kW SSE

4080 kW West

2040 kW East

10 kWh  LG battery

2 x 3 kW immersions feeding Telford 500l UVC

 

Priority to load, battery, top immersion the bottom immersion all be fed by 6kw inverter with intergrated EV charging (future use) need to buy appropriate lead when EV obtained.

SE have said although marginally over the 155% oversize limit, given the orientations, the tolerances are ok.

Due to move in 27 August, so shoud get some decent production this year.

 

Hoping to be grid free from March to October., will post the stats when up and running.

ROI very distant but something I wanted.

 

JT

 

 

 

[SteamyTea]

4 minutes ago, Johnnyt said:

Priority to load, battery, top immersion the bottom immersion

Have you tried to compare the losses of the battery and water storage?

[Johnnyt]

The battery is said to have a  DC round trip efficency of 95% and the HW diverters 97%

I imagine it will be a case of close monitoring, the UVC loses 2.8 kWh standing 24 hour loss at I guess 60C

Given the volume of DHW I was hoping to crank the temp down or mabe run the top immersion at say 60C and the lower, 2/3 down at 48C

[SteamyTea]

3 minutes ago, Johnnyt said:

I imagine it will be a case of close monitoring

Will be interesting to see a years worth of data, nothing much matter this time of year when there is excess, excess.

 

I was surprised how quick my E7 200 lt cylinder settled out, with the bottom being close to the supply temperature and the top pretty stable, even with usage during the day.

Posted up the image on other threads of the temperatures.

[joth]

9 hours ago, Johnnyt said:

The battery is said to have a  DC round trip efficency of 95% and the HW diverters 97%

More important is standing losses. The battery should be negligible over a diurnal storage pattern, but the hot water cylinder is not, especially as the loses get worse the more full (i.e. hotter) it is.

 

Topping up the battery before DHW is intuitively a no brainer for several reasons:

Assuming optimizing to minimise energy costs rather than simply ensuring every Joule is usefully employed somewhere, the battery storage is far more valuable as it can be used for all import-reducing uses including creating hot water if necessary (even, via a much more efficient heat pump?) but the reverse is not true of hot water storage, that's a one trick pony

Factor in the much higher capital cost of a battery and a goal of getting ROI, it needs to be in use every hour it be can to ever pay for itself.

Add to that an aspiration of grid independence, and you need the battery as full as possible all the time as insurance against grid outages.

Part of the justification for a battery is the freedom from having to analyse usage patterns: just use electricity as you wish and the battery will do the hard work to avoid import.

 

And finally as mentioned, typical household DHW usage patterns (mornings and later evenings) favour topping DHW last thing in the afternoon as it reduces the time the energy is stored for, and hence the standing losses from it. 

 

 

 

Edited June 9, 2021 by joth