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Old 8th September 2022, 03:01 PM
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Conan_the_Librarian Conan_the_Librarian is offline
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Default Home Generation Part 2

Long Post, sorry!

Given the cost of electricity, even with the capped Cap, now that I am on a variable tarrif, living in the countryside and no mains gas I'm moving forward with my microgeneration projects.
I already have 2 X PV arrays on my roof; both monitored in real time and I have been logging loads for the last couple of years. Western power has limited me to a maximum of 4Kw of PV based on the ability of the transformer on a pole near the house which supply's our little hamlet. While it's a bit of a shortsighted restriction as it's based on the 38 customers who share the transformer, it's one I can't get around. Reasoning failed! The fact that 32 of the customers live in park homes that aren't allowed PV or wind generators as a T&C of their leases and 4 of the houses are surrounded by trees or don't have a roof suitable then the last two who both have PV are still limited to 4Kw systems.

The house resting rate (night time) is, on average, 500 watts (low 320w to high 655w). When we've been out on a sunny day, the maximum the PV has ever exported is 3.25Kw. However, we still only generate 35% of the power we use and export 27% of the power generated, at 4.5 per kWh that is mildly annoying me!
Adding batteries isn't economical on the PV because we don't generate enough in winter to keep them topped up.

That's were the stream that runs through our garden comes in. Having done the maths over the last year the water throughput says a minimum of 300w in the summer and 1Kw in the winter. I have a turbine and waterwheel design and a generator capable of 1.5Kw. I've identified a charge controller and battery system with 9.6Kwh capacity but I'm stuck on how to get that capacity to the house and not out onto the grid.

A grid tie inverter would run at maximum based on the output from the batteries. That's ok when the house is demanding that load, but when it isn't, like the PV it will push it's full capacity out to the grid. With a 4.5Kw inverter that would flatten the batteries in a little over 2 hours. More in the winter if 1Kw is being generated but still a downward curve.

What I'm after is something to tell the inverter what the household load is and to only supply that much. Still being attached to the grid, if we exceed the inverters maximum the power is supplied by the grid.

Anyone any idea how to do this please?
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1997 4.2 A8SQ - the Projekt. 12 years and ongoing!
1997 4.2 A8SQ - Ming Blue. Restoration sat waiting; saved from the Scrapyard
2003 C5 Allroad 4.2Q - Cobolt Blue. Towing car. Laid up awaiting replacement cats and Torque Converter.
2015 Q3QS SLine - Daytona Grey. Lots of extras! Long Haired Admirals cutter.

Previously
2003 C5 A6 1.9TDI FWD - Loaner from D2 Doctor Lifex
1997 S8 - Ming Blue. Loaned out and written off. I loved that car. My first engine swap after cambelt failure.
1996 4.2 A8SQ - Ming Blue. 178k on a cambelt! Trader's 8. Delivered to A8Parts at Lifex.
2003 2.8 A8SQ - powder blueish. Fill in for a while. Sold on.
1998 1.8T A4 Avant FWD. Ming Blue (there's a theme here), PEX for the 97 S8.
And a list of non VAG going back 40 years before I saw the light.

Last edited by Conan_the_Librarian; 8th September 2022 at 03:11 PM.
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Old 8th September 2022, 04:47 PM
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All gibberish to me, but is an 'export limiter' what you're after? The following link seems to be asking your same question... possibly, maybe.

https://support.solarquotes.com.au/h...-limiter-work-
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My DIY jobs - Fan Jet Windscreen Washers, Retrofitted Electric Side Blinds
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Old 8th September 2022, 05:02 PM
ainarssems ainarssems is offline
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You should be able to get permission for more power but they can ask you to limit export power to the grid. Most modern inverters have this option. I am not being paid for export as I installed it myself and they only offer to pay if MCS certified. So I have set mine to 500w max export even when they had no objections for me connecting 4.8kW panels/5kW inverter without limitations. Only thing was that it needs to be commissioned within 3 months from granting permit or they may allocate capacity to somebody else and then if they have no spare capacity later then I would need to limit it to 16A/3.68kW

There are some hybrid inverters with dual input solar+wind or hydro and even some with battery attached to it as well.

I have Fox ESS all in one solar/battery, it did come with meter and a CT clamp and you can use either to see energy flow. I used CT clamp on the incoming mains cable and inverter can see how much energy is flowing from or to grid. When the battery is not full it will try to keep import/export at 0, use whatever is needed for the house and use excess solar to charge batteries. When the battery is full it will send excess power to the grid and export can be limited to whatever I want from 0-6000W. If there is not enough or no solar generation it will use battery to supply house but will keep export close to 0, it will not drain battery supplying grid. It has also option to set 2 charging periods per 24h from grid. At the moment 90%
I use is from solar and I hardly export anything, if I have surplus solar I just use it to charge car so I am probably using 85-90% of what I generate.When the days get shorter and darker I will not generate enough from solar so will switch on charging from 00:30-04:30 with Octopus Go at 7.5p/kWh and then use it from battery during day instead of using grid at 40p or whatever it will be now.
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Old 8th September 2022, 09:29 PM
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Is there any point in exporting to the grid? Especially if doing so limits your options while they pay almost nothing for your power. I'm awaiting installation of a PV/Battery system. First call on the PV power is the house, then hot water and then battery
Once I've had a chance to see how things are panning out I intend installing some electric heating, either underfloor or wall mounted. And for the future, and electric car.
Ainars idea of buying cheep off peek power to top up the battery for use during the day is also a great way to go.
This is what we're awaiting installation of:
12 x JA Solar 395W solar panels (4.74KW solar array )
1 x GIV 5.0KW hybrid inverter
1 x GIV 9.5KW battery storage unit
1 x Iboost hot water controller
2 x Tigo power optimisers for the extra panels.
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Old 8th September 2022, 11:13 PM
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Thanks for the replies peeps. Looks like I need an export limiter to stop the batteries being drained. Set it to zero or a nominal figure and during the day it will provide the difference between what the house needs and what the PV is supplying. When there is no sun it can provide upto the 5Kw rating and if more is needed when there is no sun, the grid supplies the rest. If the PV is supplying more than is needed then the export limiter sets the hydro inverter to zero and the charge controller uses the dump load to protect the batteries from over charge and the generator from damage. At night on low load it allows the hydro inverter to supply only what the house needs. This way I don't breech the export limit of 4Kw. I think!
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Conan (the Librarian)

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Currently,
2000 S8, Merlin Purple, Leather Pack 1, Winter Pack 1, SPAX adjustable suspension, AP Racing 6 pot front caliper, 385mm fully floating disks, EBC Yellow Stuff Pads, Black Diamond grooved rear disks and predetor pads, D2 Doctors Brake Block.
1997 4.2 A8SQ - the Projekt. 12 years and ongoing!
1997 4.2 A8SQ - Ming Blue. Restoration sat waiting; saved from the Scrapyard
2003 C5 Allroad 4.2Q - Cobolt Blue. Towing car. Laid up awaiting replacement cats and Torque Converter.
2015 Q3QS SLine - Daytona Grey. Lots of extras! Long Haired Admirals cutter.

Previously
2003 C5 A6 1.9TDI FWD - Loaner from D2 Doctor Lifex
1997 S8 - Ming Blue. Loaned out and written off. I loved that car. My first engine swap after cambelt failure.
1996 4.2 A8SQ - Ming Blue. 178k on a cambelt! Trader's 8. Delivered to A8Parts at Lifex.
2003 2.8 A8SQ - powder blueish. Fill in for a while. Sold on.
1998 1.8T A4 Avant FWD. Ming Blue (there's a theme here), PEX for the 97 S8.
And a list of non VAG going back 40 years before I saw the light.
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Old 9th September 2022, 09:42 AM
ainarssems ainarssems is offline
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Quote:
Is there any point in exporting to the grid?
Not really with prices ranging from 1.5-4.5p for fixed tariffs, if you say export 2000kWh per year it's 30-90 per year. The payments are unlikely to increase much as the generation is at the wrong time. Solar max output is in the middle of day 10am to 2pm but max consumption is 5-7pm. And on sunny days everybody with solar panels is producing power at the same time so there is excessive power at that time and for large industrial producers National Grid can request to to reduce production, switch it off or ask them to pay for exporting. There might be some viable options in the future if you have battery storage and Smart export tariff and you can export on demand when required. At the moment I think it only works with Octopus and Tesla Powerwall but at the current prices I think battery wear and reduced life from extra charge/discharge cycles are still not worth it.
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Old 9th September 2022, 10:58 AM
ainarssems ainarssems is offline
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Quote:
Originally Posted by Conan_the_Librarian View Post
Thanks for the replies peeps. Looks like I need an export limiter to stop the batteries being drained. Set it to zero or a nominal figure and during the day it will provide the difference between what the house needs and what the PV is supplying. When there is no sun it can provide upto the 5Kw rating and if more is needed when there is no sun, the grid supplies the rest. If the PV is supplying more than is needed then the export limiter sets the hydro inverter to zero and the charge controller uses the dump load to protect the batteries from over charge and the generator from damage. At night on low load it allows the hydro inverter to supply only what the house needs. This way I don't breech the export limit of 4Kw. I think!
Normally the export limiter is not a separate device but the function built into inverter you just need to connect measuring device (meter or CT clamp) attached to your mains cable from grid or meter tails that provides data to inverter. It just reduces generation amount when it reaches export limit. Other option would be power diverter which would send extra power to something like a heater in which case inverter will still be working at full power and diverter just dumping extra generation in the heater. If you can see all your stats for import, export and grid consumption then you must already have suitable measuring device in place. And most modern inverters have setting for limitation.

If you have permission to connect 4kW it does not mean that you can install more when you feel like and just limit export to 4kW or less. You still need to apply for connecting more equipment each time you connect anything extra highlighting any proposals how you will limit the export. Usually it is just a wiring diagram showing metering device connected to inverter and if it's TYPE tested inverter just giving them the inverter make and model and stating that it will be configured in inverter settings. Do you know what inverter you have?

Quote:
Reasoning failed! The fact that 32 of the customers live in park homes that aren't allowed PV or wind generators as a T&C of their leases and 4 of the houses are surrounded by trees or don't have a roof suitable then the last two who both have PV are still limited to 4Kw systems.
There is a bit more to this than just a number of houses and how many have or will have panels. The transformer is 3 phase and and if all 3 houses are connected to the same phase or even 2 to 1 phase and 1 to another phase it may cause phase imbalance with voltage going above maximum specs on the phase that receives most of generation. If it just happen that each of the houses were on different phase then there would be no reason for a low limit so it all depends on individual circumstances.

With DC charger and 3/4 different systems you might have some issues with them talking to each other and working nicely together and not yoyoing up and down trying trying to adjust. Ideally you would need some kind of central control unit that makes decisions and sends instructions to each device, this could be local or cloud based but it might be difficult if they are not from the same manufacturer. When I was 1st looking Victron range looked promising with local gateway that you can connect all your controllers to. At the end for simplicity and tidier installation I went with single unit hybrid solar/battery inverter, charger and battery enclosure and batteries.
This is what I got but the demand has gone up since and it's harder to get them now with either out of stock or long waiting times and price has gone up by about 20% as well https://www.itstechnologies.shop/col...ttery-98-d-o-d the picture on this link shows older model but they shipped the latest version which you can see here https://www.fox-ess.com/all-in-one/

I think what I would do is connect hydro permanently to mains without any limitation as it cannot exceed your limit. If your solar inverter support limitation use meter or CT clamp to measure incoming/outgoing from grid and set limit to 4kW or less.
Then use AC coupled battery storage with meter or CT clamp and it will take care of itself, when it will see export and battery not full it will adjust battery charge power automatically to keep export close to 0. If the battery is full and stops charging the power will go to grid if the inverter sees that you are getting close to export limit it will reduce generation. When it will see import and battery not below discharge limit it will generate electricity to keep your import close to 0. It will always try to keep import/export as low as possible. with AC storage you don't need your devices to talk to each other you just need import/export data from meter or CT clamp.

If your current inverter does not support limitation you could either replace inverter with the one that does and get AC coupled storage or replace it with hybrid solar/battery inverter with integrated charger. With the AC coupled charger or hybrid inverter/charger you also have option to charge the battery from grid during night when electricity is cheaper and then use during day when it is more expensive but you will probably not need it if you are looking to generate 1000W+ hydro in winter

Instead of limiting what inverter generates you could chose to divert extra generation to heating but in winter when you need heating most you are unlikely to have much excess generation and if you are just going to heat water during summer I am not sure it's worth it. I just chose to charge car with excess power. It may involve a bit of planning ahead for example if I see good weather ahead but will not be at home at the time I may chose to charge car from the battery and then let the battery recharge when sun comes out.
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