Hybrid Solar install questions

[IanP]

First Off can I apologize if this has been raised before and if so please point me to the answer.
This is my first adventure into Solar power and whilst I have read a lot about it, I am still unsure if my thoughts are practical.

I am embarking on a self build in Scotland and want to utilize as much solar power as possible.
The plot is quite rural but does have access to single phase grid power.

Ideally, It would be fantastic to be fully off grid, but given that I will have a ASHP and at least one EV point on top of the normal power usage of a 4 bed home (and its in Scotland ? ) I appreciate that it would need a very, very large array and many, many batteries! (quite like the idea of server rack batteries but they appear to be still hard to buy in UK).

As the feedback tariff is quite small and would be limited to a max of 3.68kw, then I was wondering if there is a way to generate more, use it directly/via battery, with the added ability to charge the battery from the grid when there is no sun.

I did have one thought of having 2 (duplicated) consumer units, one fed from grid and the other fed from solar/battery and then having the circuits coming out of these into a third consumer unit filled with changeover switches (break before make).
This would then give you (albeit manually), the ability to decide what circuit is supplied by grid and what from solar by setting the changeover switches as appropriate.

This would than allow you to power, for example, all the lighting circuits and downstairs ring main from Solar with all others from the grid.

If you then found the battery was coping or draining too quickly, you could add or remove circuits as needed to then balance the load to use as much of the solar as possible.

This may sound a bit crazy and not ‘Smart’ but does it sound feasible? or am I missing something such as a smart inverter that can limit (or even stop) the export, whilst using as much power as I can generate/store, take additional power from the grid when needed, allow the battery to charge from the grid when solar output is insufficient AND provide backup when the grid goes down?

I have tried to contact a few companies to discuss options but they must be very busy at the moment as they either don’t answer or try to arrange consultations in several weeks time!

The way I have tried to describe using change over switches, sounds a bit Heath Robinson and I can only feel that I’m not the first person wanting to generate more but limit the amount feed back to the grid so thinking that there must be hybrid charger/inverter’s out there that would fit the bill.

I am still at the planning stage of the build, but want to understand the best way to have the system set up.
Sorry for being vague on power needed, but just looking for some general guidance and help from other a lot more experienced than me.
Any thoughts would be gratefully received.

[SteamyTea]

5 minutes ago, IanP said:

I am still at the planning stage of the build, but want to understand the best way to have the system set up.

Roof design.

Get the angles optimised for winter, and have lots of usable area, with no obstructions.

All the rest is tinkering and the technology to do that will come along in due course.

Then look at how little energy you actually need, so don't have 20 6W LED downlighters in the kitchen.  Maybe a couple of 5W LED pendants will suffice.

A 3 minute shower uses a lot less DHW than a bath filled up to the brim (and I like that more than a shower).

So compromises are in order.

 

Get a washing line.

[ProDave]

With a normal 3.68kW PV system you will easily be able to self use all of it, very simply.  don't try and over complicate it.

 

The key to self usage is simple things like using the big appliances in the middle of the day, and a solar PV diverter to send excess power to the immersion heater to reduce hot water heating costs.

 

I manage to export so little that is is simply not worth claiming the pittance of the smart export payment.  And not claiming that means you don't need to bother with an MCS installer.

[TonyT]

Hi Ian,

 

no need to use change over switches now!

except possibly last resort running the house off a petrol/diesel generator.

 

 

Battery packs with hybrid inverters, oversize solar arrays all possible and easy to integrate into a new home.

 

maybe located in a garage or plant room due to the size.

https://camelot-forum.co.uk/phpBB3/viewtopic.php?f=14&t=708

 

[Christiano]

I don’t think it’s feasible to be off-grid for a normal home, especially with heat pump and EV. Unless you can get a lot of batteries.

 

We have 11kWp solar in Kent and on a grey day in the winter we can get less than 1kWh.

We typically generate 9mWh a year, export about half of it even with diversion to immersion. 

If you put too much solar in you may not be able to use it all (unless you divert to EV) so I wouldn’t go too large unless it gets cheaper the bigger you go.

 

I do like some of the thinking in the EV space about the car powering the home in the evening then charging in the wee small hours on cheap electric.

[Johnnyt]

SolarEdge offer 3.68kW inverter that can be 55% oversized in terms of the array.

That is approx 5.7 kWp

Excess generation, not being used for the load is not inverted and can be directed to their dc coupled energy bank battery, so far 10kWh if you can get hold of one.

You can divert ac to DHW if you prefer.

 

[saveasteading]

18 hours ago, Christiano said:

the car powering the home in the evening then charging in the wee small hours on cheap electric.

Car batteries, when replaced through being 'worn out' , get taken to big sheds which do exactly this and store power from power stations through the night.

 

Don't batteries 'wear out' in a predictable number of cycles? And they cost what....£5 to £10k?

 

I am guessing that a car battery is more expensive to replace  than one in a box in the plant room.

[Christiano]

True, and our battery is a PowerVault who sell normal batteries and and Eco option that uses Nissan Leaf batteries which are no longer good enough for the car but okay for home use.

[Col2021]

I'm watching this avidly, we are extending an existing cottage, the extension will have standing seam roof, cottage has slate. The cottage roof is probably OK but wife definitely doesn't want on roof so I'm thinking of solar slates. The slate roof might actually be ok and not need fixed so we might leave it for now anyway,  depending on costs. It looks like you can get pv for standing seam as well.

The house has mains gas (for now) but what would be the best way to integrate it all? One neighbour,  who doesn't have gas, uses solar to firstly heat the house then once that is at temp it heats a  water cylinder, then it charges the car.

I'm thinking we could do something like that but still have gas as a backup? We will also have a wood stove sk can that be integrated as well, maybe to heat water when it is on?

[SteamyTea]

Solar slates are the expensive, low performance option.

Much better off looking at traditional modules. There are a number of methods to have them fitted. 

As for trying to heat a house with them, that is going to be hard. Winter production is so much lower than than your space heating demand.

Heat domestic hot water is your best option. A dime cylinder is all that is needed.

Car charging may be useful, but there is generally a minimum load below which a BEV will not charge, so you may be importing electrical energy as well as using all the PV production. Depending of your electricity tariff, that could be expensive.

[Col2021]

Diesel car and gas it is then!

[SteamyTea]

5 hours ago, Col2021 said:

Diesel car and gas it is then!

I got half of that.