So now I have a solar PV system how do I make the most of it???

Exiled_Tyke

tunnel wrote: »

Got my new Aldi kettle today.
For the record, 8 out of 10 cuppas today were completely covered by my own generation and yet had it been the "big 3kW" kettle ALL of those cuppas would have left me needing to BUY electric.

great stuff. A good day for it. Best day of the year for me and I was out for all the daylight hours so a lot of exporting done.

Exiled_Tyke

ASavvyBuyer wrote: »

“ ...(and doesn't have a reasonable payback period, nor is very green)....
”
I don't understand that statement - can you expand?

Yes, found that an interesting comment. Can't quite see why using a fossil fuel (gas) to heat water is greener than using the power from the solar panels.

For us the payback time worked out at about 2 years.

Conservative estimate of about 4kw a day for about 200 days a year to provide all the hot water we needed from March till September. We already had a less than 1.5kw element in the base of the tank. Switching device cost £30 from REUK, plus added a 2kw dimmer in the circuit to adjust power for poor days and was easy to fit into existing immersion heater circuit.
Therefore, with gas at about 2p/kw and at best 80% efficient, 10p/day for 200 days = £20. So diverting pays for itself in a couple of years.
Realise that not everyone would already have the lower wattage element or same setup, but what we have works for us.

OK the argument I read (I thought somewhere on this forum) as being one reason for governments not supporting these diverting devices is that it is kinder to the environment for you to export your electricity thus saving usage of fossil fuels to make electricity for your neighbours. If the consequence is that you instead use gas to heat your hotter then this is far more efficient use of the gas than using it or other fossil fuels to make the electricity which you neighbours will now need from you using up the spare electricity.

Now if we could all get to be paid for export (rather than the notional 50%) and at something closer to price we buy at then there would be no incentive to use the electricity in this way, we'd be better off and the environment would benefit.

Hope that all makes sense.

Exiled_Tyke

ASavvyBuyer wrote: »

“
For us the payback time worked out at about 2 years.

Conservative estimate of about 4kw a day for about 200 days a year to provide all the hot water we needed from March till September. We already had a less than 1.5kw element in the base of the tank. Switching device cost £30 from REUK, plus added a 2kw dimmer in the circuit to adjust power for poor days and was easy to fit into existing immersion heater circuit.
Therefore, with gas at about 2p/kw and at best 80% efficient, 10p/day for 200 days = £20. So diverting pays for itself in a couple of years.
Realise that not everyone would already have the lower wattage element or same setup, but what we have works for us.

Now that is a clever set up and sounds quite cost effective. The dimmer in particular is the clever bit I like the most.

[Deleted User]

Exiled_Tyke wrote: »

Now if we could all get to be paid for export (rather than the notional 50%) and at something closer to price we buy at then there would be no incentive to use the electricity in this way, we'd be better off and the environment would benefit.

Hope that all makes sense.

Original FIT rate here


The export payment for me is so low, 1.72p [50% of 3.44p], that using a diverter will always be worthwhile. No gas here so heated by electric one way or another... [ASHP].


Cheers

Martyn1981

Exiled_Tyke wrote: »

OK the argument I read (I thought somewhere on this forum) as being one reason for governments not supporting these diverting devices is that it is kinder to the environment for you to export your electricity thus saving usage of fossil fuels to make electricity for your neighbours. If the consequence is that you instead use gas to heat your hotter then this is far more efficient use of the gas than using it or other fossil fuels to make the electricity which you neighbours will now need from you using up the spare electricity.

Now if we could all get to be paid for export (rather than the notional 50%) and at something closer to price we buy at then there would be no incentive to use the electricity in this way, we'd be better off and the environment would benefit.

Hope that all makes sense.

Yep, I think that's roughly the argument, and it can get contentious. In the summer months heating the water via leccy might be twice as efficient as gas, assuming the boiler is cold, losses in the pipes (heat loss from boiler and pipes no longer a benefit) etc, so 1kWh of leccy does the job of 2kWh of gas.

However in the heating months, the efficiency difference won't be as high, as waste heat is now beneficial, and the boiler is hopefully a little more efficient.

This compares to the grid having to replace the 'lost' leccy export, which will most likely be done through increased gas generation, which is probably 40% to 50% efficient, so requiring 2 to 2.5kWh of gas to be burned and also transmission losses of the leccy (5% to 10%).

Personally, I don't think it's a big issue either way. The various diversion devices are great practice (and R&D) for the future for diversion and better use of renewable generation. Also, there's a small chance that a cheap diverter will push the economics of PV from negative to positive. In that scenario, it might seem wrong to divert high grade (PV) leccy for water heating, but without it, the leccy wouldn't exist, so a net benefit.

Another long term issue is that hopefully the carbon value of our leccy will begin to fall, so reducing domestic gas emissions will become beneficial, though I appreciate, so long as gas is used to meet fluctuations in grid demand, not storage of renewable generation), the issue may be mute.

Mart.

Martyn1981

Thinking about this further, and perhaps taking it to the extreme, but a great use of a diverter would be for battery storage, that then feeds an ASHP. If timed right, hopefully this would run at a COP of 3 or 4 in the evening and morning (when outside temps are a little higher than the night).

In this scenario, 1kWh of leccy could replace about 5kWh of gas (80% efficient boiler). But I appreciate there would be battery system losses, and only a small amount of value in the UK, though I do have a reasonable amount of export at this time of year, and a need for heating morning and evening.

This is more of a ponder, so may be full of holes, but looking towards the future for diverters?

Mart.

shavy65

zeupater wrote: »

Hi

Safety point from from a previous discussion to be aware of .....

HTH
Z

Thanks for the info Zeup. I`m going to leave things as they are though, the set up has been like this for nearly 2 years now and it`s fine. Maybe the numbers equate to different temperatures on my stat as the hot water doesn`t seem to be overly hot.

Cheers

shavy65

Exiled_Tyke wrote: »

Now that is a clever set up and sounds quite cost effective. The dimmer in particular is the clever bit I like the most.

Just wanted to add something here. I`ve had my set up now for about 2 and a half years and I`ve never seen anyone mention the same type of diverter that I have, a Solic 200, it always seems to be the immersun and iBoost everyone goes for.
Anyway, my Solic works away just fine and arguably even more efficiently than any of the competitors. I can`t remember the exact figures, but I seem to recall the advantage of the Solic is that it will divert anything as low as 25 Watts(?) where the other 2 are only able to divert much higher minimum amounts (I think).
This obviously results in less being exported and more being diverted. This is especially effective during duller days, or days when usage is high and generation is only slightly more.
As far as I can see the only downside is there is no digital display, instead there are 3 LEDs which show when diverting, powering on etc.
Anyway, just thought I`d add this in as it might give any potential diverter buyers something else to consider.

Cheers

[Deleted User]

shavy65 wrote: »

Just wanted to add something here. I`ve had my set up now for about 2 and a half years and I`ve never seen anyone mention the same type of diverter that I have, a Solic 200, it always seems to be the immersun and iBoost everyone goes for.
Anyway, my Solic works away just fine and arguably even more efficiently than any of the competitors. I can`t remember the exact figures, but I seem to recall the advantage of the Solic is that it will divert anything as low as 25 Watts(?) where the other 2 are only able to divert much higher minimum amounts (I think).
This obviously results in less being exported and more being diverted. This is especially effective during duller days, or days when usage is high and generation is only slightly more.
As far as I can see the only downside is there is no digital display, instead there are 3 LEDs which show when diverting, powering on etc.
Anyway, just thought I`d add this in as it might give any potential diverter buyers something else to consider.

Cheers

Yeah looking at my SolarImmersion III it starts diverting after a 50w surplus. When I bought it the iBoost did not exist and was less than half of the cost of the immersun. Indeed had i bought the Immersun it would be out of warranty and still not paid for it's self. No good in our not so sunnt climes.

pinnks

I am with Mart on the issue of heating water in the summer. As I have said elsewhere on here, I have compared old gas records with current ones and can say that on average I need about 6kWh of gas in the summer when the boiler is cold etc etc as Mart describes to do the same as 2kWh of leccy.

I also know that I am saving about £80 of gas over the summer, plus a contribution during the "heating months" months, so expect my immerSUN to repay itself over 3 to 4 years.

As for which is environmentally more sound, I again agree with Mart's thrust but am sure that debate will rumble on for years...

I too have thought about using diverter technology to charge batteries. It would not be as efficient as DC charging bt seems like a good idea for retrofitting existing systems once battery prices come down