Mimicking solar panels from an AC supply

[Beelbeebub]

Bit of an odd question :

 

Is anybody aware of a device that takes an AC 240v input and outputs a DC supply in a manner so it can be plugged into a hybrid inverter and the inverter think it's connected to a PV string?

 

Ideally the device would be able to be controlled so the power delivered to the inverter could be varied in real time. 

[JohnMo]

No sorry no idea. But you don't need PV connected to a hybrid inverter for it to function with a battery.

[Beelbeebub]

I'm trying to work out a way for a number of flats to share a single panel array.

 

My thinking is a single large array and 3ph inverter provide a 240v supply and then each flat can have a standard hybrid inverter and battery pack fed by what it thinks is it's own PV array, but is actually this hypothetical device taking power from the actual array supply (that is totally separated from the mains).

[SteamyTea]

Why not just wire in an off grid system and then run separate DC cables to small inverters in each flat.

If too much much power is drawn the small inverters should shut down.

 

But would it not be easier to wire in a grid tied to the main feed and then just sub meter the PV contribution to each flat.

[Nickfromwales]

Do you do all inclusive rental or do they pay for their own electricity via unique electricity meters?

[Beelbeebub]

34 minutes ago, SteamyTea said:

Why not just wire in an off grid system and then run separate DC cables to small inverters in each flat.

If too much much power is drawn the small inverters should shut down.

 

But would it not be easier to wire in a grid tied to the main feed and then just sub meter the PV contribution to each flat.

I don't think supplying each flat with a submeter PV would work.

 

The connection from the PV would have to be after their meter, otherwise I could supply elec and their energy supplier would get paid! 😁

 

But that would mean each flat would be interconnected after the meter. If flat A drew power it would flow through the meters of Flat A, B, C etc. There would be no way to untangle who used what.

 

I could wire each flat to it's own string but then have to run DC to each flat, there there are issues of a particular panel fails that flat loses it's PV, whilst if I share across one big array I can just disconnect the affected string and the system runs at a reduced capacity 

 

Which is why I thought about distributing the PV power as DC through the solar input. 

 

It should isolate each system and prevent "cross feeding" and allow flexibility for each flat to use more than it's share if nobody else is using it. 

[Beelbeebub]

4 minutes ago, Nickfromwales said:

Do you do all inclusive rental or do they pay for their own electricity via unique electricity meters?

They all pay individually with whatever supplier they pick.

 

I'm looking to provide some PV as a benefit, as you would new carpets or the like. It also helps with the EPC ratings. It might be that providing solar is the cheapest and easiest way to get a C (it used to be switching to gas) 

 

So the generated elec would be provided free and unmetered to reduce their bills. Obviously some days would be better than others and some usage patterns would be more cost effective than others but that's on the tenants. 

[JohnMo]

Think you are just making life hard for your self.

 

Give them a rent holiday, be cheaper for you and possibly more appreciated by them.

[SteamyTea]

Got to go on a car journey for the next hour or so, do a little sketch of what you want and I can ponder it.

 

I think you can claim a SEG payment that is unaffected by the main supplier (could with FiT) and to a different person.

That way it would just be wired in after the individual meters but before the consumer/into units.

Any generation will find it way to the nearest load.

[Dillsue]

1 hour ago, Beelbeebub said:

They all pay individually with whatever supplier they pick.

So are they all on their own DNO meter and have their own MPAN? How many flats are there?

[Alan Ambrose]

That's a slightly tricky / non-standard problem. Give us some more info, so we're not playing 20 questions. How big is the potential array? How many flats? Animal, vegetable or mineral etc?

[Nickfromwales]

I’ve quoted jobs like these loads of times, and you just have (for eg) 6 flats, do 2-3 panels (or more, depending on roof and budget) per flat, and have 6 systems.

 

Anything else would be impossible / impractical and hugely cost prohibitive.

 

1 MPAN = 1 PV system, one goes down, 5 stay online.

 

Who’s going to monitor & maintain?

 

Most landlord systems connect to the landlord meter that serves fire alarms and communal / external lighting etc (anything not billed to the tenants).

 

SIMPLIFY!!

[Beelbeebub]

3 hours ago, JohnMo said:

Think you are just making life hard for your self.

 

Give them a rent holiday, be cheaper for you and possibly more appreciated by them.

Did that already but there is ultimately a limit to how long that can go on for as the running costs don't stop. 

 

The driving force is to get the EPC rating up. Reducing tenantt's utility bills is a nice side effect. 

[Beelbeebub]

So 17 flats in a 5 story building so the roof space is limited. The roof is also very old, very complex and not at all suitible for fitting PV to. 

 

The main option for panels is a pair of vertical arrays on the south side, where there are two large external chimney stacks - all the other vertical faces have windows, pipework etc on.  There is also the matter of planning (aonb and conservation area) so it may be no panels are possible at all.

 

Thereis alsoo two east facing balconies that could potentially have "balconysolar" style mounting on the balustrade . 

 

The problem is the flats near where the panels are don't need the EPC boost as much. 

 

It seems unfair to fit panels next to someone's flat and them not benefit from them, so I'd like to spread the benefits about a bit.

 

Separate systems as mentioned by NickFromWales is a possibility but my worry is we could end up with a flat not using much of it's generating capacity, whilst the flat next door could use more capacity. Sort of like individual car ownership vs car pooling.

 

A chunk of this depends on the upcoming EPC regs (due soon IIRC) currently (mains powered demand shifting) batteries are more or less ignored despite the potential impact on bills.It maybe fitting batteries gives me a big jump. Or not, who knows. 

 

At the mo I am just kicking about ideas. 

[DamonHD]

May be relevant: https://midsummerwholesale.co.uk/buy/solshare

[Temp]

21 hours ago, DamonHD said:

May be relevant: https://midsummerwholesale.co.uk/buy/solshare

 

That looks cool..

 

Quote:..

 

The SolShare unit is placed between the inverter and the main switchboard. Receiving one three-phase AC input from the inverter and outputting up to 15 single-phase or 5 three-phase AC outputs (or a combination of both). Outputs are wired on the load side of each unit’s meter, at the building’s common main switchboard.

[JohnMo]

2 hours ago, Temp said:

SolShare

Only £7500 for the basic unit.

[Beelbeebub]

 . Thanks for the solshare link. 

 

I've looked into it, and it is definitely a possibility.

 

My two concerns are

 

1. It only does 15 flats per unit and I have 17! So two units or possibly 2 flats having their own standalone setup. 

 

2. It seems quite "smart" and cloud enabled etc.  I'm wary of stuff that requires a subscription - what happens if the company goes bust or is bought out and the new owner (or even the orginal owners) decide to jack up the prices or "enhance" your package by making it worse (hello Netflix)?

 

Hence my wondering if there was a relatively simple sub £500 device that could allow for distribution of a single array between multiple flats via the already existing DC panel input. 

 

I was thinking of something along the lines of a current limiting 240v (or maybe 110v) power supply. The MPPT function would simply ramp up the current until it hit the limit which would be the maximum power point. If I wanted to reduce the power delivered to a given flat the current limit would reduce. 

 

The goal would be a system not reliant on external Internet connections etc. 

 

 

[SteamyTea]

What size (kW_p) PV system are you thinking of installing?

When divided by 17 flats, and accounting for utilisation (50%), is it going to be a useful saving.

 

[Temp]

Many power supplies that have a current limit can't be used in current limiting mode continuously or they overheat and shut down further.