Off Grid Power Generation....

[Dave Edwards]

First off, I'm NOT an electrician!
I live & work in a coop which already has a hydro scheme. We generate around 10kW at best and we don't feed it into the grid. We use the power to heat water and supply isolated circuits.

We are looking into upscaling our hydro to generate 30kW. We know we can feed this directly into the grid to get FIT's but we want to make sure we make the right decisions about how we use this power.

I understand the average household demand is around 15kW. We probably do use a fair bit more than average, so most of the time 30kW might be OK.

Many of us feel that we'd like this power to be available to US when there are grid outages, which we OFTEN get in winter.

I've read some stuff about 'islanding' and 'intentional islanding' and I'd assume that in the last 10 to 20 years with the great increase in wind turbines and other renewable generation, that there must be a lot of advancement in what is possible now?

Is there any way we could have a set-up where we feed all our hydro output into the grid, but when there is a grid power outage, switch gear allows us to become and island supplying our own power until the grid comes back on line? 

So far, I've heard this either isn't possible, or would be too difficult to achieve? 

I'm happy to accept that, but does anyone know WHY it's so difficult?

I'm well aware there are many avenues, like energy storage and separate/duel circuitry. But my main question is if we feed into the grid and the grid goes offline, do we HAVE to go offline too, or can we supply ourselves until the grid returns.

 

[Manator]

Hi Dave,

if the grid is down, its down. you will not be able to get anything from it. If you generate your own then you could use that, providing that it is set up correctly. For long term only storage of energy solves your problem. The stored energy is pretty basic and would only cover emergency features for a limited time.

Vast improvements in both photovoltaic and wind turbines have given us more opportunities to harvest free energy, at an initial cost of course.

The best advise I can give is to research all options.

 

[SPECIAL LOCATION]

 Now I don't do PV stuff...

But from my limited understanding is this problem to do with the synching up of the locally generated AC and the grid supplied AC.?

e.g

normally the turbine/PV generated electricity has to synch up the the existing grid supplied waveform...

But if grid power is down and you were running locally generated power....

when the grid came back on it could be out of synch with generated AC wave??

Or am I barking up the wrong tree...

Or have I had tooo many...

Guinness   Guinness   Guinness

 

[steptoe]

well, from my understanding its a safety situation,

if you are generating onto the grid and the grid goes down, for whatever reason,

you are still trying to feed into the grid,

now, what happens to the poor chap from the electric board that has been sent to fix the bad joint in the road?

he has switched off the power at his end, but he doesnt know you are still sending 230v down the cable from your end,,,,,,

bad day explode

 

[SPECIAL LOCATION]

well, from my understanding its a safety situation,

if you are generating onto the grid and the grid goes down, for whatever reason,

you are still trying to feed into the grid,

now, what happens to the poor chap from the electric board that has been sent to fix the bad joint in the road?

he has switched off the power at his end, but he doesnt know you are still sending 230v down the cable from your end,,,,,,

bad day explode

:Salute

Thinking further.....

Spose you'd also be trying to supply all the houses off your transformer as well if you are feeding into a dead grid ?????

Guinness

 

[SLIPSHOD & SLAPDASH]

I generally dont do this type of stuff. On a recent job we did (in my unusual job thread in the pictures section) we fitted a contactor box which was witnessed by the DNO and then sealed by them.  Their power holds this in (on) so if the grid goes down this disconnects the various house systems from the grid. Its doubled up incase one 'sticks'. Its this box

 

[SLIPSHOD & SLAPDASH]

As i say, this is not my normal thing but i see it no different to a generator change over switch, either auto or manual.

 

[steptoe]

slips,

I'd think with agreement from the DNO, as you have had, then thats a perfectly acceptable situation/solution, cost may be an issue though,

I'd bet DNO charged for that.

 

[SLIPSHOD & SLAPDASH]

 cost may be an issue though,

I'd bet DNO charged for that.

I bet they did. There were suits down all the time nosing around as this was the first time anyone in their area also had battery reserve with the generation. Even the local MP came and visited on 'official business' to check out the greenness. Anyhow, i need my beauty sleep so goodnight.

 

[Dave Edwards]

Slipshod, I don't have permission to look at your jpeg

But I think what you're suggesting is what I was envisaging.

Also I think 'Special Location' might be correct in that it's when the grid comes back online that the main problem(s) occur,
Our generator and the grid would nee to be in phase with each other for us to start feeding back into the grid.

I guess I just thought those sorts of problems would have been overcome with the latest influx of generators & technology advances...

But maybe not! Apparently the words used when we suggested it were "Stand alone facility - This is very tricky with a 'split phase' connection and not recommended." 

That's why I'm attempting to find out why there is an assumption we'd HAVE to be a 'split phase' connection, and why that's so tricky and not recommended,

 

[SLIPSHOD & SLAPDASH]

Once again, not my expertise but i thought split phase was generally used on the end of long cable runs or remote locations when adding to an existing network. It gives a slightly higher voltage. I am sure someone will correct this if I am wrong

 

[Andy™]

yes, it does give  higher phase-phase voltage, but its normally used in rural areas because it only needs 2 cables, not 3

 

[Dave Edwards]

That would seem logical as we are in a rural area.
So am I gleaning correctly from all this that we MIGHT be able to feed our 30kW into the grid and have switch gear to make us an 'intentional island' when there is a grid outage, and switch us back when the grid is back on-line?

Is it just that it would be expensive to do?

 

[Sidewinder]

I have to agree with Canoe on this, (almost) anything is possible, it just depends on how much you are prepared to pay!  :slap

 

[SLIPSHOD & SLAPDASH]

Could this be the reason our customer paid approx £85k for a sub on their land.

 

[Sidewinder]

Possibly...

 

[Dave Edwards]

Sorry, getting a little confused by some of the 'lingo'

"SLIPSHOD & SLAPDASH" said "Could this be the reason our customer paid approx £85k for a sub on their land."

Does that mean 'substation generator'? 

"Canoeboy" we don't have any of the new equipment yet. If you read my original you'll see we already have a 10kW hydro generator but we're not attached to the grid at all with it.

We have permission to go ahead from the hydro side of things - meaning we've been given the go-ahead to use the water we need, and we've been given permission to feed into the grid, but we haven't a clue yet how that can/would hang together, so some of the answers to some of the questions here & elsewhere might greatly affect what sort of generator and electrical equipment we use.

It's a chicken & egg thing.

 

[SLIPSHOD & SLAPDASH]

An ongoing job of ours which started a few years ago (i did not know new members can not look at pictures posted ?)  the new house is about half a mile away from the public highway and that road is on the end of the village. The customer is very wealthy, did not want overhead cables so paid for the local DNO (which i think was EDF at the time) to bring a new underground cable in and fit a substaton next to the house. The existing overhead cable was only single phase and not large enough so would have had to have been upgraded anyhow. We dont really get involved with the generation side of things (although we fitted all thats shown in the pics, it was all overseen and commissioned by a French company), i am only now wondering if  the new substation  was also  to do with the concerns that you have.

 

[Dave Edwards]

SLIPSHOD, thanks, I can now see your pictures.

The message I got before said something like "You are not allowed to view files until you have at least 10 posts" It seems I've passed that threshold now!

I was talking a bit more today to our hydro engineer, he thinks one of the main problems with us having a standalone system is the metering aspect. 

As it stands, it seems the system we CAN fairly easily & cheaply set up allows us to feed all our output into the grid, but when the grid has an outage, our generator has to trip out and stop generating too.

The scheme we are intending to build is going to cost in the region of £100,000 and it seems a real shame that for that amount of money we could generate plenty of power, yet not be able to use it if/when there's a power cut!

This sharing of ideas is really useful, if only to help me begin to understand the problems involved. I appreciate peoples input.

I know there aren't any crystal clear and obvious answers. I'm attempting to gain more understanding so I can begin to see the potential options more clearly.

 

[binky]

you would also need inverter that isn't 'grid tied' becuse otherwise it won't work when mains fails. This may mean having an inverter that is grid tied for normal operation, and non-grid tied for running in grid failure conditions (though this could be achieved with your generator). I would suggest having a look at SMA website, as they manufacture a comprehensive range of inverters for On and Off grid situations. Normally with systems around 30kW, the G59 compliance is built into the inverter rather than utilising a separate G59 relay - it's cheaper! Using a G59 relay allows use of a non-grid tied inverter, but incurrs DNO costs. There is, however, increasing demand for off grid systems, so a quick call to their technical helpline may produce a more cost-effective solution to your problem. NB they have a UK office, but don't be put off if the phone number takes you to Germany, they speak very good English. Please report back any solution they recommend.