Questions on grid connect

[charlieblair]

Hi all,

I've been having a proper think about buying a turbine for grid connect on my Dad's farm in S E Scotland. I have a few questions - maybe some of you guys have already done the sums so can save me some time:

For a average wind speed area (good exposed site) what is going to be my best sized turbine? - 2KW (potentially >1), 5KW or 10KW?

  The lower plateau speed of the 2KW suggests it might be better than the 5KW (where do the power curves on the web page come from by the way?)

What power price can you expect from utilities? I understand they're introducing a compulsory net metering regulation. Is this true?

Roughly what payback will this give? (very rough only - how about everyone gives their best guess on assumed average yearh yield)

What unit are the NOABL figures? The site shows about 8.3 at 10m

Cabling. How much would it cost (hardware and labour) per metre? This obviously effects siting.




Any advice much appreciated.

All the best

Charlie

[Ivan]

Hi Charlie,

I can't really advise, as we have not had the different turbines on the same site to test the relative performance. You can get an idea of the relative performances from the graphs on the website. Remember that if the wind speed doubles you get 8x the amount of power, so to a certain extent you cannot compare sites or estimate performance on the basis of average wind speeds. A site that has constant 8m/s wind, can produce 4 times less power than a  a site that spends half its time at 0m/s and half its time at 16m/s (assuming the wind turbine does not furl out of the wind below this speed) .....but both sites have the same average speed.

If you shop around you can get 10-11p/kWh from the utility companies - but some may offer you as low as 2-3p (ironically, these tend to be the specialist  ones selling 'green' electricity)

[Ted]

For a average wind speed area (good exposed site) what is going to be my best sized turbine? - 2KW (potentially >1), 5KW or 10KW?

Decide how talll a mast you can put in as well. The taller the better but this will very likely have an impact on your ability to get planning permission though.

What power price can you expect from utilities? I understand they're introducing a compulsory net metering regulation. Is this true?

No net metering yet. Government are talking about it as a possibility only. Don't bank on it.

What unit are the NOABL figures? The site shows about 8.3 at 10m

The NOABL windspeed figures are in meters per second (m/s)

Cabling. How much would it cost (hardware and labour) per metre? This obviously effects siting.

Depends on cable size (mm2) which in turn depends on voltages and the % transmission loss you are happy with, the total length you need and the sort of terrain/soil conditions.  Big cable (16mm2 SWA - armoured for underground) is about £2.50/m if bought in a big drum (500m). Look at an online catalogue (Screwfix) for other prices. Labour will be a digger + driver for maybe a day - say £250 maybe plus a delivery and collection charge.

[martin]

8.3m!!!!!!!!!! - bung in several, as large as you can get, on as tall a pole as you can get consent for!
That's fast payback territory!

[martin]

having done a few back of the fag packet sums - you could talk about 3-4 years payback! - get several!

[charlieblair]

Thanks Guys. And for the enthusiasm martin .       

Could the power from a 5KW turbine (or maybe larger) be routed through a house's grid connection? (it is a holiday cottage, rarely used, so most would be exported. And no constant baseload). Or could it (particularly if I add more than one turbine) be connected straight into the 11KV line for export? - an end line.

Ted: much appreciated. I guess if I'm looking for payback asap then hopefuly a long term gain I need big cable (but don't worry; I'm not ONLY doing it for money - it's a learning curve for me too. I am a renewable energy consultant working on policy/macro economic stuff and feel the definite need for more technical experience).   The high wind site is actually fairly near to the grid point so no problem there.
The lower wind site would need longer cabling - could I just feed a smaller turbine into the house (there's a considerable base load - my Mum has two freezers and a fridge) without bothering with synching with the national grid etc? In which case what extra kit would I need on top of what's provided with the Navitron 1KW or 500W turbine?

Finally. Is there any way of measuring the output from a grid connected turbine. I want to measure and log windspeed for a year or so after this first turbine goes up with a view to a larger (perhaps decomissioned) installation - could I just use output (if I can log it) as a proxy, or do I still need to get a anemometer and all the associated data logging kit?

Many thanks

Charlie

ps one last unrelated qu: I'm designing a house from scratch for a very specific site (planning permission unlikely, so probably just to keep myself occupied). As such I can get the solar gain and S facing roofs right. For solar thermal, would a 10m (say) expanse of S facing roof be better than 2x5m at say 20o off South (so that some tubes are getting maximum exposure morning and afternoon). Also, I know 35o is meant to be best angle for PV in the UK - is solar thermal the same? (I guess you might want to optimise them for winter gain, not summer, and therefore provide more angle??)

[Ted]

I have a 6kW Proven going through 2 x 3kW SMA Windy Boy inverters into my grid connection so 5kW is no problem although it is up to your local DNO to approve at their discretion as the limit between G83 and G59 Regs is 16Amps per phase. You can't connect direct into the 11kV line - it needs to go out there via the metering and transformer (you'd be into big-boy generation territory otherwise with the need for network impact surveys and licences/exemptions, etc).

without bothering with synching with the national grid etc? In which case what extra kit would I need on top of what's provided with the Navitron 1KW or 500W turbine?

To run these appliances 'off-grid' you'd need a battery setup with regulator and inverter. And the wiring in the house would have to be altered to keep them separate from the rest of the mains.

Finally. Is there any way of measuring the output from a grid connected turbine. I want to measure and log windspeed for a year or so after this first turbine goes up with a view to a larger (perhaps decomissioned) installation - could I just use output (if I can log it) as a proxy

You should have a generation meter installed anyway. This will measure the output from your turbine/inverter. You could just take a daily reading from this and log it. To automate this will require more kit (I have a SMA Sunny Boy Control Light hooked up to a PC - this can log readings every 15 minutes if desired). It is only a rough proxy for wind speed as there will be low winds that do not produce any output that you will miss and the highest wind speeds will max out your turbine. The actual speeds will depend on the start-up speed of the turbine and the settings in the inverter.  Useful wind logging also needs a higher resolution - say a reading every 5 minutes at least (it's amazing just how variable the wind is on a day when you think it is a steady breeze).  Wireless data logging anemometers are available for a few hundred pounds.

[charlieblair]

Is it not possible to keep the mains connection and just add a generator that never generates above the baseload so never exports (or dumps if it does go above baseload)? You can probably tell that I am not an electrical engineer    
Doesn't the windsave connection work something like that?

C

[chaso]

There are various ways you can do this.

But the most important thing is your wind, it is not constant so when it is blowing you need something to store it or keep a load on it so the turbine won't over spin.

That is why batteries are a common store to use. So if you go off grid you would most likely run an inverter from batteries to get your mains voltage.

The other way is to use your local electricity board 'the grid' as your battery! by using a grid tie inverter. This will enable you to do away with batteries as your grid is doing that job. So when the wind blows it is reducing your the amount of electricity you would use from the grid so reducing your overall cost of electricity.

If you really have a lot of constant wind, you could always get a meter installed so you can get paid for any excess electricity, but this costs and you have to really make sure its worth it.

The important thing to remember is if there is a power cut the grid tie inverter has to stop outputting electricity to the grid so it does not fry anyone who is repairing it.
So in this instant really if you do get a power cut then you could always use a Bio-diesel generator as your backup rather than complicate this with batteries.

What Windsave seem to have is a grid tie inverter just like all the others. So when there is a power cut it has to stop. Although I'm still not convinced you would make any electricity with a Windsave.

[Ted]

Is it not possible to keep the mains connection and just add a generator that never generates above the baseload so never exports (or dumps if it does go above baseload)? You can probably tell that I am not an electrical engineer    
Doesn't the windsave connection work something like that?

C

But at a high enough time resolution (i.e seconds rather than hours) many times of the day your baseload is probably zero. Fridges/freezers etc don't draw power all of the time and your 24/7 stuff (VCR and clock/radios) consume pretty small amounts anyway (if they don't then change them!). Your turbine will export if it is generating at these times.

The Windsave exports to the grid if its output is higher (!) than your consumption level (as any grid-tied system would).

[charlieblair]

The other way is to use your local electricity board 'the grid' as your battery! by using a grid tie inverter. This will enable you to do away with batteries as your grid is doing that job. So when the wind blows it is reducing your the amount of electricity you would use from the grid so reducing your overall cost of electricity.

That's exactly what I meant. So that installation costs are kept as low as possible and the only re-pay is the opportunity saving on electricity not inported from the grid.   Presumably I could think about an export meter at a later date (if the buy-back price increases, or if I add more wind/PV/CHP later on).

Roughly what additional costs would you be talking to do this, on top of the basic Navitron turbine price?   Grid-tie invertors seem to be expensive right? The cabling I guess. Anything else?     
And is there any way of setting an immersion heater to switch on when the turbine is generating > baseload? (I don't want to be giving those unhelpful DNOs free electricity if I can help it - I guess what you need is one of those Dynamic demand control systems (there's a link on here somewhere) so that fridges etc and other non-constant electrical goods can synch inteligently with the generator. Damned if i begin to know how to set up the sensors and electronics though. )

[Roger Willott]

I have bought a 5kw from Ivan but as yet we are still putting my scrap tower together as my morals said I shouldn't import steel from China. I have also modified their design which now has a hand winch and copied a turbine locally which has a ginpole. Equally, Ivan has said that he supplies galvanised steel wire ropes, not stainless, which I shall use. Regarding the electric cable, dont forget that the regs specify amoured underground, but it may be acceptable to have conduit. Equally, with the 5kw I have it has metres of fles attatched to it I measured it and from memory it was 47 metres.
Roger Willott

[charlieblair]

Thanks Roger. A hand winch definitely sounds like a good idea - I'm in Fiji right now and lots of the turbines out here (on huge poles) have winches for the cyclones. I figure a winch would be good for argueing that the turbine's non-permanent.

What's FLE?

[Roger Willott]

fle thats technical and means I didn't finish the word off!!
FLEX! It has 47 metres of flex connected to the generator and the ends away from the generator have connectors with labels on them for connecting to the control box. The trouble is that it seems to be intended to be used with a battery bank and I want to grid connect it. That is the least of my worries as the tower is still in its component parts.

Good luck.

[Roger Willott]

Have read earlier in this section and you say that you are damned if you can work the electrics out. This download is very helpful.

Web:www.est.org.uk/bestpractice
Energy Efficiency Best Practice in Housing
CE72 if there is a choice.

Roger W