Triac Phase Controller

[Baldbloke]

First of all hi!

I tried to introduce myself in the other forum but it then said I needed 10 posts before being allowed!

I'm not an electrician but have a great deal of electrical questions to ask. Some of the electricians up here in Moray Scotland just start scratching their heads when it gets a bit more complex than fitting a few plugs.

I'm fairly interested in renewables and have a small farm 20KW wind turbine and a 60KW biomass log boiler. Both are up and running, and as my turbine is below 40KW the exported units are estimated and paid at a low rate of 50% of 4.77 Pence/unit. There is nothing to stop me using all the available power rather than exporting into the grid at all. What I'm wanting to do, but cannot yet find anyone with the expertise, is to use some sort of triac phase controller to divert any excess power from the turbine to power an immersion in the 4000 ltr buffer tank that the biomass boiler currently heats. I realise that one immersion might not fully heat this large tank but anything to save some wood and labour would be great.

I buried one heavy duty armoured cable in preparation which I have been told (due to the size of the cable and the distance it runs) will safely allow a 30 amp draw on a single phase. Although there are two phases used by the turbine the other phase is used to run the house and out buildings, so I really just have the one spare phase to play with.

My questions are:

Is it possible?

Where can I buy a suitable triac phase controller?

How big an immersion heater would be safe to link up allowing for a maximum of the 30amp draw?

Where would I get the information to wire it all up (not me, but an electrician)?

Am I being daft and should I just get it wired up without the complication of the phase controller and have an isolation switch for when the wind isn't blowing?

All answers greatly appreciated!

 

[ProDave]

Hi and welcome to the forum. I'n not far from you in Ross-Shire.

What you want can probably be done with off the shelf stuff, with a bit of adaptation.

Basically you have a 20KW presumably 3 phase generator, so let's simplify things and treat it as three 6.6Kw generators. You will seee why the simplification in a minute.

A 6.6KW wind turbine is not a million miles from a 4KW solar array.

For the domestic market you can buy Solar PV dump controllers, probably the best well known is the immersun.  This monitors your import / export, and dumps excess power to a standard 3KW immersion heater.

I'm thinking three of these, each one monitoring one phase of your supply and each one connected to it's own 3KW heater. That would be able to dump up to 9KW of excess power to your tank.

Anything larger and you are probably into bespoke design, unless of course someone knows of a larger off the shelf unit.

What cable did you bury? to make this work you would probably want 6 core (plus earth) as you would need to connect three heaters each from a different phase, so 3 completely separate cables would be much better.

 

[Baldbloke]

Hi and welcome to the forum. I'n not far from you in Ross-Shire.

What you want can probably be done with off the shelf stuff, with a bit of adaptation.

Basically you have a 20KW presumably 3 phase generator, so let's simplify things and treat it as three 6.6Kw generators. You will seee why the simplification in a minute.

A 6.6KW wind turbine is not a million miles from a 4KW solar array.

For the domestic market you can buy Solar PV dump controllers, probably the best well known is the immersun.  This monitors your import / export, and dumps excess power to a standard 3KW immersion heater.

I'm thinking three of these, each one monitoring one phase of your supply and each one connected to it's own 3KW heater. That would be able to dump up to 9KW of excess power to your tank.

Anything larger and you are probably into bespoke design, unless of course someone knows of a larger off the shelf unit.

What cable did you bury? to make this work you would probably want 6 core (plus earth) as you would need to connect three heaters each from a different phase, so 3 completely separate cables would be much better.

Hi ProDave,

Thank you very much for your response.

You are correct that the turbine produces a three phase output, however from there it looks a little more complicated. From my inverter shed where there are four 6000w inverters, and a windbox the power is fed back from there to the consumer units via the two available phases. The house and outbuildings power is taken from one of these phases. The other phase/consumer unit was put in when the turbine was installed and is as yet not tapped into (for importing power, except for the small draw to operate the slew motor in the turbine), but as I type this is being wired up to power that large shed. This sheds power usage (on the single phase) is going to be very low as it's main use will be as a store, and I was hoping to use this for powering an immersion. I appreciate that two phases for this would be much better, but the wiring at the consumer units is a little busy to fit in additional tails.

The buried wiring up to the shed is armoured 25mm, and it's run length is 90 metres. From the shed being presently wired to the shed where the buffer tank is would be an additional 50 metres.

3 of the 3kW units would work - or use 6 of them

I have never used Immersion but have used Solar iBoost (wireless) and they are very good

http://www.solariboost.co.uk

The other way would be a couple of correct CT's and a DC and AC inverter - The AC inverter to do the brains work of calculating any excess energy and the 3 phase DC controller to fire a 30kW three phase immersion heater wired in single phase for the DC controller.

 Thanks too Canoeboy for your response.

I'm a little uncertain where the connections would be taken. I presume that one would take it from the turbine output (en route to the consumer units)? I'd be concerned that Interfering with the windbox and its workings to access the three phase output from the turbine might knacker the programs for the turbine. The nearest transformer down the road that supplies us with power is only a split phase and I believe that the windbox converts the three phase output into split phase to suit the grid connection.

From what I think you are both suggesting is that I'm going to have to bury a shorter 50m set of cables from the inverter shed directly to the buffer tank capturing both phases to power these immersions, rather than using the single phase 25mm SWA that goes up to my new shed that would have a total run of 140metres if I continued it down to the shed where the buffer tank lives.

In case this limits the potential power output, I do know that the SWA cable I buried from the inverter shed back to the consumer board in the house is only 20mm as that is what the turbine people said was required for my turbine to export power to the grid and house. 

 

[Baldbloke]

Further to your advice, I've just sent mail to Immersun as it looks like they might have this situation covered.

Will keep you up to date on progress!

Thanks both, and any further suggestions very gratefully recieved.