In this blog, Alan Chapman talks us through an energy project on his home.
His LinkedIn profile is here: https://www.linkedin.com/in/alan-chapman-7314385a/
Front Solar panels were completed on Friday 27 February 2015 at 12.15pm & were up & generating from this time via the installed dual string Samil inverter & registered for FIT payments the beginning of March.
We are not South facing, but south-east & are affected by the shadows created by the surrounding trees & the front protruding roof which was why I went the duel string route to allow for better generation while some of the panels were in shade allowing the others to fully produce without paying for micro inverters & the additional cost.
My wife would not allow for a conventional installation of roof mounted panels so instead I found a company who would install them in the roof, this was at reduced cost as they were trialling this system out.
After a short while I was aware of the need to monitor production & try to maximise our usage so invested in the Owl Intuition system that would also allow me to expand its capabilities as the need arises.
It felt great to be able to start to run household appliances for free by seeing when we had available spare electricity above our background standard usage.
We spent the first year trying to use a holiday mini Kettle that was just 800w took ages to boil but meant we could still boil a kettle in lower level generation & any excess would go to the grid, or be used by the washing machine or tumble dryer etc.
The following year I decided we needed to increase how long we could generate power for as just after lunch the sun was to the side of the house & then diagonal to the rear roof before it went down behind the trees.
So I tried to find out how much more capacity I could add to my registered system only to find out that in April 2016 extensions were disallowed so I would not benefit from any form of subsidy!
I was gutted, but after a bit of internet trawling found a lot of solar installation companies were selling off stock before stopping doing installations as they had stopped almost overnight did a deal to have 2kw installed to the rear of my house facing north-west & was reliably told I was wasting my money due to this & the trees surrounding me.
So had a very cheap system installed in April 2016 & what a difference this made to how long we could produce electricity for although our output was not huge it was steady for a longer period before dropping off to zero very quickly.
But it was almost impossible to get more than about 40% usage even being careful so I needed to find something else to make a bigger benefit when I found out about Iboost.
This can divert excess generation back to other devices like a hot water tank, but the problem I had was we had a combi to feed our house with hot water & it was in the cold garage with no insulation.
So time to insulate the garage loft & put up a ceiling to reduce the heat loss & save the losses of heat from the combi pipework running through the cold garage to the house.
Next I found a used Iboost which I set up in the garage to an extension lead to charge cordless devices to try it out & it worked well.
Then I hit the jackpot on E-bay & found a used thermal store (the same one I had seen on line that had an indirect coil that could be used to pre-heat the water going into my combi that could accept water at upto 60’c.
So after a phone call to the seller about the tanks condition bought it £75 & went to collect it, bigger than I thought but just went into the car & came with a thermostatic mixing valve that would limit the water outlet temperature to 55’c
So next it was time to get it set up & tested before spending any money on having a plumber install it if it could leak or just not work.
All good & both Iboost & thermal store working & limiting the water outlet temperature as it should, just hard work getting my plumber to agree to fit it, & what a good job he did.
Excuse the additional items on top of the tank but I use it for drying things out as it gets quite warm for now.
So from April 2016 we were able to meet all of our hot water needs from diverted excess generation diverted to this solar store & monitor the tank temperature via the previously installed Owl Intuition monitoring with just the addition of a tank sensor & sender.
Producing useful information on performance as below.
So now we are seeing no gas usage until towards the end of September when central heating is firing up to keep the house up to temperature & occasionally add a little heat to the hot water if its not hot enough.
Just a note regarding the potential risks of Legionella, all risks have been eliminated by the way the thermal store operates, the actual stored water is specially treated to prevent bacterial growth & is totally separate from the water which is feed to the combi which only remains in the thermal store for a short duration & if it is not 55’c the combi will heat the water until it is!
So generation has increased from around 3200kw in the first year to 4200kw in the year after installing the additional rear system & although the peak has not really gone up the length of time we produce has increased allowing us to be able to cook tea on some occasions!
I have realised that we still needed to add additional methods of making use of what we are producing so looked into adding a battery system to further our self-sufficiency, but after going to various shows was still concerned if it would ever be worthwhile.
So October 2017 decided on a system which was independent of both solar systems & ordered a Sofar Solar inverter & 4.8kw in the form of 2 batteries & had it installed to see what it could do for us.
On Paper it could store 4.8kw but the batteries can only discharge at 2.5kw per hour & only go down to 15% before they shut down & the system goes into sleep mode until I have excess generation that can start being stored back into the batteries.
What I was unaware of is just how much additional benefit there was even during the day while I was generating as if a large device say kettle 2,5kw was switched on & I was only generating 1kw then the 1.5kw would come from the batteries, so even in the day they could still assist.
So moving into this year in April after realising I could still charge the batteries & heat the thermal store I was still producing more than I could at times use, so as the Battery system was modular decided to buy an additional battery & hopefully store enough electricity to run from the sun going down until it was producing the next day.
So now at 7.2kw I was able to charge at a higher rate now 3kw & also discharge at the same & also even in April go 24 hours without the batteries running out of charge, result!
However you cannot always stay totally off grid for electricity as on occasions (we have an induction hob & electric oven) use more than we are producing via solar panels & battery output & this has to come from the grid.
But as of today we are on day 72 of not exhausting the batteries (not all in a row but since June 1st)
I will be able to supply further data as required regarding performance & from the first of January this year until today 68% of our electricity consumption has been from Solar generation & I still am able to provide all of our hot water needs from the thermal store.
Our electricity consumption for April was 113kw vs 198.4kw last year & for May just 22.8kw vs 176kw last year & for June this year just 8kw vs 166.9kw & this month to date used just 2kw.
We have a background consumption of 150w at its lowest & around 400w at highest we have a large fridge freezer & cctv system on 24 hours a day & also a septic tank with air pump running constantly & the house consumption varies between 8kw on a best day to 28kw on a heavy day & I am hoping to get our grid import below 2000kw for the year from April this year to April next year, this would be a further reduction of 1000kw with all of the batteries installed & still produce our hot water.
I have also 2 years ago changed to a kettle that can be set to switch off at 90’c which saves electricity! We only boil water for babies bottles, drinks are fine at 90’c. Quite a lot of additional energy is required to actually boil water compared to just heating it to 90’c.
Alan Chapman, July 2018
Today 26th August we have now achieved 108 days of not exhausting the batteries & although the days are getting shorter & the sun is slightly lower am hopeful we can get a fee more days.
Maybe even get to a third of a year, but batteries are certainly the way forward & I am still tempted to add a further battery to the system.
But if I did it would be knowing that they would not be of much use for most of the year but would further reduce our grid consumption on odd dull days if they were charged from the previous day.
July utility bill for me was just £7.49 for gas & electric including a standing charge of £6.99.
Cost for the last 12 months to heat with gas & power our electricity hungry lifestyle 4 bedroom detached house £127.
This is after taking into account my FIT payments!
But as the third battery was only installed in April & the 2 battery install was only the end of October last year anticipate that my cost should be sub £100 once we reach April 2019.
Very nice, I really do need to find some way to use my exported energy after reading this.
Storage update 2020
This just about brings things upto date on my system, although I have added a further 2 panels on my shed roof that help offset the loss on the change over from roof to roof .
Battery Storage, true costs from my experience & existing set up.
Pylontech plus batteries are listed as good for 6000 cycles based on not charging too fast or drawing off too much power.
As my set up limits the charge & discharge rate al below the requirements & that I am only using 80% of the total capacity have based my costs on achieving 6500 cycles without it making a noticable difference in storage capacity.
Cost for my inverter & 5 Batteries at trade £4400, I have not included the £200 for the cabinet as it is not a consumable!
So 6500 cycles X 10.2 KWH usable capacity 66300 kwh this is my estimate & I anticipate that the batteries will still be functioning long beyond this!
So the cost per KWH of storage for me is £4400/ 66300 so 6.63 p per KWH
So using my batteries in the winter as a method of saving money still works for me buying electricity at 5p at night with the cost of storage in true terms is 11.63 P per KWH which is still less than my 14p daytime rate.
But it does for some confirm that Octopus Agile would work out best if your able to juggle your storage & usage to make the most of the tariff.
I am still happy for me that I am on the GO tariff as I am still running dishwasher & washer dryer during the 5P per kwh time slot.
Since doing all my calculations I now estimate that in the winter quarter I will charge the batteries for 90 days & I will potentially charge & discharge from solar pv 250 full cycles, so max 340 per year.
This should give me at least 19 years of storage & I still anticipate that the batteries will still be functioning.
Before anyone jumps in I appreciate that the battery inverter will need replacement within this timeline, but the costs & capabilities are getting better every 2-3 years.
So I expect to be able to absorb the cost against the unit price of electricity continuing to rise increasing the savings.
Latest update as of 25th June we now have a 12000BTU Air Conditioner to heat & cool ( high efficiency) or Orangery & a further 2 solar panels on the opposite side of the shed roof.
All of which are only in sun at certain times of the day so I have a relay unit to swap the panels depending on output & or a light sensor that can trigger the relays, this allows production to continue until later in the day.
The Air conditioning is powerful enough to also heat & cool to an extent our dining room, lounge & kitchen & have already proved a good investment & consume less than 1kw in use of solar energy, so even in winter it will be a useful alternative to using an electric 2.2kw heater to quickly warm up the room, now it should on occasions be done for free.
I am sure in both the late autumn early winter it can keep me warm while working from home in there, & the same in the spring.
I am hopeful that with the extra production from my shed most of the running consumption will be covered by solar as my consumption will now be higher for electricity but be less reliant on gas running the underfloor heating.
So my carbon consumption will be lower still.
Have now bought the last piece of the carbon neatral life, with the purchase aof a Kia E niro 4.
This can be charged from my solar panels at 7kwh rate using my existing 12kw battery system to iron out much of changeable weather.
Or I can go trickle charging with a 13a charging lead at around 2kwh rate to just daily make up any small trip uses poping to the shops or visiting close by family.
I have not bought any special charging systems but I do have a pod point charger which I am told may well be updated via new software to allow smart charging or VTG charging.
So I do have to keep an eye on the weather & can remotly stop the car charging via an UVO app.
Outside of the decent weather I can make good use of charging up via Octopus GO tarriff which can fully charge my car for around £3.50 & should allow me to travel about 250 miles.
Fantastic blog, a must read for people looking at batteries, sadly as an installer we are legally prohibited from making such projections, people need to read this, huge fan of Sofar/pylon. First system I was willing to sell in Uk.
Thank you
Very interesting read. Thank you. I see a few parallels between your system and ours, although ours is at an earlier stage if evolution.
We too have an E/W rig with (for now) 2x 2.34KWp capacity with 3.5kWh of storage (this will be doubled this month I hope if I can churn out enough rebuilt jukebox valve amps…). I plan to switch from Bulb Vari-Fair to Octopus Go as soon as Bulb have updated our SMETS2 meter on ECOES.
I hope to place 2x JA Solar 460wp south facing modules on my shed roof (with Tigo optimisers) tied to the E facing string. Another 2x or 3x west facing 460wp modules tird to my west facing string should be added in the spring. These will on paper overload the inverter 3kWp/string DC input but I will monitor the real power generation per string and maybe bypass a module or two if needed in the spring/summer months.
We are also having a combination boiler installed under the Welsh Government NEST scheme. However, I believe in ‘n+1’ redundancy and will be installing a back up indirectly heated tank similar to yours to replace our ageing copper indirectly heated/immersion heated tank. This should run from excess PV energy generated.
So Alan, if you have any practical advice it will be very much appreciated!
Good luck and well done so far!
Martin Rimmer.
Martin, re summer overload, once you have monitored who you get on & if you find that on sunny days are producing too much you could always wire a bypass contractor rated for 1.5 times the max current & voltage of the string, to link out the panel or panels making sure that you do not short out the panels being taken out of the string.
Or use a manual high voltage DC switch again over rated for duty that can be turned to do the same as above.
You should not switch the panels under any load & ideally plan the day before or operate it seasonally to give you your diversity.
Or think of using more than one inverter & making one have grid limiting so it does all the hard work for you.
Obviously everything should be installed to current regulations & meet all DNO approvals current at the time of installation.
If anyone who has read this & is looking for an excellent energy supplier then feel free to use my link that will get you £50 off your first bill & I will also get £50 credit.
share.octopus.energy/mint-lion-117
I don’t understand the ‘bypass’ discussion. You cannot ‘overload’ an inverter with power. When it reaches either its design power limit or the instantaneous demand, it will automatically reduce the current (hence power) it accepts from the array, however many panels there are in the array. Voltage overload is different, but your inverter MUST be rated for the maximum possible (ie no-load) voltage anyway, so this can never happen.
Rocky, sorry this is a late reply, but the bypass is for people who just want additional generation during the winter months to be more self sufficient, that do not see the point in sending additional generation to the grid when it is not likely to be needed.
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