Sheesh... you really want me to go deeper into the technicalities?!

There is a European-wide specification Requirement for Generators (RfG)

It applies across Europe because we share access to the grid operating at 50Hz.
(Ignore voltages; it's only the frequency component which underpins network stability)

Our EREC G98, G99 and G100 regulations are based on that RfG.

We may not make requirements that are less stringent than RfG, but there are situations where we might need to have a tighter specification.
The Balcony Solar kits come into those variations between G98 and the RfG.

1: Let's note that there's little to prevent a flat owner installing more than one Balcony Kit.
They won't 'know' about each other because there's no mechanism to hand-shake between them.

A qualified installer would know that such an arrangement requires a G99 Application to the DNO.
But a householder is unlikely to understand that regulation or why it exists.

2: EREC G98 is an Annex 1 Document of the Distribution Code and therefore the document is afforded legal weight.

An installation that does not comply with the prescribed requirements of G98 may be disconnected by the DNO due to concerns of interference / safety.

The installation would also have to comply in full with BS EN 7671 (the Wiring Regulations).
Only qualified electricians may work on installations that fall within the scope of the Wiring Regulations.

3: When a device exports to the grid, it does so by raising the voltage.
That causes current to flow from the device, and towards the grid.

In the UK, the grid voltage limits are defined by an Act of Parliament: The Electricity Safety, Quality and Continuity Regulations 2002

Section 27 states:

27.3b defines the single-phase domestic supply to be between 216 - 253v AC.

If a Generation Device senses that the grid voltage falls outside of that range, then it must cease generating (remove itself from the grid).
It may not reconnect until it detects that the mains voltage has fallen back within the supply envelope.

Even then there must be a random delay (typically 1 minute) before it attempts to export again.

Unless the Device has been tested for G98 compliance, then no one knows whether it will correctly perform that voltage stabilisation requirement.

That leaves open the possibility that an engineer working at a local substation could still be electrocuted after it has been isolated from the 11kV supply.

4: All generation devices, especially those which create the 50Hz sine-wave using electronics, will also create harmonics of 50Hz and radio-frequency interference (RFI).

This is much less of an issue for turbines which synchronise to 50Hz using mechanical rotation.

Any device seeking G98 approval must be tested to ensure:

• that the RFI falls below a stated threshold
• that the voltage stabilisation/detection circuitry will still safely disconnect the device from the grid, even if there is RFI and harmonics present

5: Rooftop solar panels cannot be touched by hand whilst in normal operation.

For that reason, most installations 'float' and are not tied to earth.

However, the inverter to which they are connected must still provide adequate surge-protection which is measured with respect to Earth.

A Balcony-mounted (or ground-mounted) solar array can be touched.
The (micro-)inverter itself must be earthed on its mains output,
but it must also provide an earth for the metal casing, the aluminium frame of the panels, and any metal comprising the balcony rail.

The quality of the earth path must be such that a fault-current causes the safety-trip/RCBO to open the contacts within the specified time-frame.

That's an additional problem if the same earth is being used by surge-suppression devices.

G98 testing will check to ensure that the trip opens fast enough when a pre-defined fault current passes through the earthed metalwork.

Since these Balcony Solar kits are not G98 certified, it is unknown whether they will 'fail safe' under the relevant fault conditions.

Is that adequate and detailed enough?

Or do you want me to add more?

@transparent So much drama...  😂

They are not for exporting to the grid. And I have just been told this: 

"They must be hardwired by an electrician (not plugged in to a 3 pin socket)  and the DNO must be notified. They are not usually a problem."

So not quite plug-and-play in the UK but still not complicated for property owners. 

"To get paid for exporting you need an MCS-certified installation which certainly won't be worth it for a small system. And is not what they are designed for anyway." 

-0-

So it certainly is a far cheaper way to have a small battery and solar system but until they have a different way of connecting they will not be able to be used by tenants in the UK.

It is far cheaper to pay an electrician for small scale balcony or garage roof solar & battery system than pay an installer for a full-scale MCS-registered roof system

It really is that simple it turns out.

This was what I needed to know. I guess to be renewables solution for tenants someone needs to invent a different connection system. 

@lucia I suppose ‘A different connection system’ could be based around a small battery (2-4 kWh’s ish) that is charged from the balcony panels and has one or two domestic appliances plugged into it. Maybe a refrigerator and / or other low demand circuit and when there is insufficient power left in the battery, the grid is used to charge it up to a ‘top-up’ level to tide the appliance demand over until some solar energy comes along. Regards, Toodles.

@toodles But the inverter still needs to be hard wired in. That's the electrical connection that makes it impossible for the tenants of rental properties which is the fabulous gap in the renewables tech market that they plug (sorry 🔌😁) in mainland Europe. 

The early starters with these systems have had European Investment Bank support for exactly this reason. The EU has been pushing for renewables developments for the rental sector for a while whereas Britain mostly ignores it. 

But hopefully, someone will get their thinking cap on. 🤞🏻

@lucia There are ‘stand alone’ units such as those used for camping etc. I think the likes of Ecoflow make units that can also plug into the mains to charge the battery - but I may be wrong as I have not researched this at all! Regards, Toodles.

Posted by: @lucia

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They are not for exporting to the grid.

They are 'exporting to the grid' within the EREC definition.

There is no current sensor to prevent electricity from the micro-inverters from being exported when the amount of solar generation exceeds the load imposed by the flat.

If the flat occupants go away on holiday and only keep the power on for a fridge/freezer, then the Balcony Solar system will export.

Posted by: @lucia

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I have just been told this: 

"They must be hardwired by an electrician (not plugged in to a 3 pin socket)  and the DNO must be notified. They are not usually a problem."

And what do you think will happen when the member of staff in your local DNO Connections Team tries to enter the Balcony Micro-inverter into the DNOs system as a G98 device?

There will be no matching device on the ENA database, so they'll respond to the installer with the requirement that the unit gets disconnected.

On the screen in front of me I have the text of the advice given by the senior engineer for National Grid who writes and maintains the standards:
"We would have to seek to instruct the customer to disconnect the equipment as the equipment is deemed to be non compliant with the standards for parallel generation."

That is written by the 'boss' of the guy you've spoken to today.

Generation devices which are not pre-certified to G98 may not be installed in the UK.

It matters not whether they are hard-wired and have the required lockable isolator and dedicated bi-directional RCBO.

The two criteria which differ between G98 and European RfG are these

• Limited Frequency Sensitive Mode (Over frequency)
• Constant active power output

I’m very interested in these for my dad who lives in Germany. They have updated the regs such that you now can attach 200wp of panels, I.e. four panels. You can still only export 800w maximum. Given the price of panels it makes sense to oversize. Here is the system I’m looking at, seems semi reasonable and dead easy to install. Of course still more expensive then the sum of its parts. 
https://www.ankersolix.com/de/products/b5143-new?s_3=B5507415&s_2=A17C13Z1&s_1=B5609341&ref=naviMenu_pps

The German grid topology is different to ours in GB.

The majority of domestic premises have a 3-phase supply.

You would expect their regulations to differ.
Aberations from an 'iffy' small-scale generation asset will have less adverse effect on generation devices in neighbouring properties.

To install these the simple way on a balcony, flat garage roof or in a garden - apart from the physical fixings you need to:

a) have equipment that is on the 'approved' list 

b) have all the electrics hard-wired in and installed by a certified electrician - this includes Section 712 of BS 7671 - regs that are about isolating etc.,. This is to pass building control rules for electrical work to get the necessary paperwork sign off. The spark will deal with all this (as did the spark for my heat pump who installed a brand new CU alongside my 'normal' CU). What this entails/costs will depend on your electrics. 

c) Fill out a G98 form part A - IF this is a single new installation that fulfils all the other requirements - ie everything above AND you don't already have solar and it is below a certain size. You do not have to notify the DNO in advance provided everything is as above. 

d) Get the G98 signed off by the electrician and/or suitable person.

They do not have to be MCS registered if you do not wish to 'sell' electricity or claim grants. 

You are not going to have anything to sell with such a tiny system anyway and paying for the MCS paperwork on top of all the above makes it pointless as a low cost microsystem. If you need/want MCS it can be signed off by an umbrella organisation exactly the same as heat pumps. Obviously you would need to know this before you start. 

Indeed, I believe City & Guilds are now training and accrediting solar installation electricians. 

d) The G98 part A needs to be sent to your DNO within 28 days. 

You can get an 'approved' (see point A above) bifacial 800w inverter/panels kit with (compulsory for sign off) 'rapid shutdown' for around £400 complete with software for monitoring and remote management.  A spark is going to add his invoice to this obviously. 

You can add a battery too but that's not my interest here.

As I said, unlike mainland Europe, the UK regulations mean it is a fixed home owner installation and not a portable tenant installation (Europe uses powerline tech to do this).

But even done the UK way it still makes a non-rooftop micro system quite a bit cheaper than a full rooftop solar. You could run your fridge freezers or whatever, charge a battery or heat a water tank for quite a bit of the year. 

Hopefully, as renewables become more embedded within society, more, lower cost technology will be designed along with the relevant regulations to accommodate the home rental market. Pure economics mean it is a sizeable market and we are not going to achieve any sensible level of decarbonisation without it. 

@transparent – I don’t think this was addressed earlier, and my understanding of electricity is fairly basic, but I’m curious: is it possible for these plug-and-play balcony solar units to export excess energy back into the grid if they generate more than the household’s base load? I understand the export wouldn’t be metered, but technically, could it happen via a standard plug connection?

Yes @editor - they are export devices at heart.

The only reason they wouldn't export to the grid is because you've already used all their output within the home.

If the micro-inverters don't correctly fulfill the G98 specification then they can adversely affect other generation from neighbouring properties.
For example here's a couple of photos taken 2-mins apart showing the output from an inverter with an integral display:

The second photo shouldn't be possible.
If the inverter believes that its export has pushed the mains voltage above 253v, then it should've disconnected itself from the grid.

Another inverter in a nearby house on the same phase should 'see' this 253.9v and remove itself from the grid.

It produces a "cascade effect" whereby multiple generation devices in the area all stop exporting within a couple of mains cycles (40 milliseconds).

Connecting to the grid any device which isn't G98 tested and certified can far-reaching effects across the local area.
The householder with the "out of spec" device will probably remain oblivious to this because their own inverter is still exporting.

Anything we do needs to be "grid friendly".

Posted by: @editor

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@transparent – I don’t think this was addressed earlier, and my understanding of electricity is fairly basic, but I’m curious: is it possible for these plug-and-play balcony solar units to export excess energy back into the grid if they generate more than the household’s base load? I understand the export wouldn’t be metered, but technically, could it happen via a standard plug connection?

They are not 'plug and play' in the UK. As I have spent multiple posts trying to explain the last couple of days... 😩 😂

They are hard-wired in a very specific way into a CU (on the demand-side - in a separate CU because it needs to be on a spur with loads of other esoteric sparkie gubbins, apparently - eye glazing stuff for me 😁). This is why the accredited electrician is fundamental. 

The kit on the approved list (which is set up by ENA Connect Direct -  funded by the seven UK Distribution Network Operators) is kit with all the required bits for uk regs.  The site was set up fairly recently I'm told, precisely to simplify things and make it all transparent. It's loads better imo than the clunky MCS site.  [🤦🏻‍♀️]

If you sent anything to the grid you would be giving it away for free if you are not certificated by MCS. Lol... 

Germany's plug-and-play systems are permitted on that understanding - they are not allowed to sell to smart grids or platforms or even community installations and anything that goes to the grid is gone - it's a freebie for the supplier.  But their (real) plug-and-play solar uses Powerline tech. 

To be eligible for a G98 Part A application it is quite size-limited in terms of voltage and everything else. Plus you are not permitted any other previously installed solar. 

Thus to send anything to the grid from an 800w system your base load would have to be very small and anything 'leftover' would be even smaller. And of course, in the UK there's the little issue of..... sun. 🌞⛅️🌥️☁️🌧️