Cheap grid-tie inverter?

towel401 · 17-02-2009 2:47am #1

I been looking around but most of them cost over 350e for a 300w one. and all the ones i see require some oddball voltage that a similar powered wind turbine won't supply. of course i could get a DC converter or build one but that reduces efficiency again, meaning the whole thing isn't worth it. anyone know where to get a decent, cheap and cheerful one?

would photovoltaic solar panels be worth the trouble of installing anyway? it seems they will take a ridiculously long time to pay off especially here in ireland.

the cost of the grid tie inverter seems to make the whole thing not worth it but i don't feel like messing around with na$ty lead acid batteries either

quentingargan · 18-02-2009 1:29am

Hi, First the usual declaration of interest - I am working on a domestic wind turbine and sell grid tie inverters both as part of the turbine and separately...

A proper grid-tie inverter needs to be compliant with EN50438 in Ireland and/or G83 in other countries. They are a fairly sophisticated device with programmable islanding time, limits to voltages, phases etc. They must synchronise perfectly with the incoming grid before locking on, and cut off within 0.5 seconds in a power cut to prevent electrocution of line workers. You really shouldn't connect anything onto the grid that doesn't meet these standards (and you won't get an EN50438 one for €350 as far as I know..)

If you have a 300 watt turbine or PV, your best bet is probably batteries, and a small inverter that you can buy for €30 - run one or two of your lighting circuits from this and forget grid tie. If the battery goes low, the inverter will cut out and a relay can ensure that this circuit clicks back to the mains with barely a flicker.

I'm afraid grid tie is only really financially worthwhile if you are using solar PVs above about 1kw or wind turbines in the 2Kw range.

To my mind, solar PVs have a very long payback at present, but they will probably fall dramatically in price over the next year or two as nanosolar and other thin-film producers get their production on stream. At present, the price of panels ex-China is about €2.60 per watt. Nanosolar are promising prices of US$1. That would make solar PVs more interesting...:rolleyes:

riccol1966 · 17-12-2009 11:17am

sorry, updating an old thread I know ---

anyway I'm attempting to find out about Mastervolt Soladin grid-tie inverters. They are frequently used in the UK, priced appx £350 or thereabouts, and are G83 compliant. I think the dublin based allied solar used to sell these for the Irish market, but I cannot find out about them anymore, and it looks like they have replaced their old website information. I wonder do there have different phase settings etc for the Irish grid as opposed to the UK grid. And by the way you simply plug them into a wall socket, no electrician required to wire them in, so costs are kept to a minimum!

As usual info is hard to come by and they don’t seem to have taken off here. Perhaps Mastervolt themselves may have further info on availability, but these would, in theory, work with solar panels and give you a relatively cheap start point for e.g. 300-800W of panels.

quentingargan · 17-12-2009 5:34pm

riccol1966 wrote: »

sorry, updating an old thread I know ---

anyway I'm attempting to find out about Mastervolt Soladin grid-tie inverters. They are frequently used in the UK, priced appx £350 or thereabouts, and are G83 compliant.

Alas, ESB does not accept G83 and insists that all grid tie inverters conform to EN50438. Worse still, there are two "National Variations" to EN50438 that must also be met and fully tested - Ireland has its unique standard in relation to both frequency range and voltage range.

None of the low-cost inverter manufacturers have bothered to make these changes. It is also very unlikely that a plug-in inverter would be acceptable. There are requirements that there is a minimal voltage drop between the inverter and the incoming mains, and I don't think this could be guaranteed over a ring-main circuit.

So even if you find this inverter, ESB won't connect it for buying surplus electricity. If you hook it up without consent, besides breaking the regs, you won't get paid for electricity exported.

riccol1966 · 17-12-2009 6:54pm

Quentin, just to clarify (here's an excerpt from elsewhere, I am assuming it is right ?)

EN 50438:
Parameter Disconnect setting Clearance time
Over voltage 230V + 10% 0.5 seconds
Under voltage 230V -10% 0.5 seconds
Over frequency 50 Hz + 1% 0.5 seconds
Under frequency 50 Hz - 4% 0.5 seconds

G83:
Parameter Disconnect setting Clearance time
Over voltage 264V 1.5 seconds
Under voltage 207V 1.5 seconds
Over frequency 50.5 Hz 0.5 seconds
Under frequency 47 Hz 0.5 seconds

So what we're taking about here is basically the difference in disconnect time between the two specs. G83 = 1.5secs for voltage, EN50438 = .5 secs for voltage. So if I understand this correct, the G83 inverter itself, outputting 230V @ 50Hz, will be in total harmony with the Irish power in my house, is that right?

That’s how I see it, and the only difference is the disconnect timings which mean that the G83 model cannot be used for exporting electricity. However, if there is no intention to export, but simply consume the power from a PV array when the sun shines, then I is'nt it quite feasible to have a G83 supplied inverter in an Irish house, plugged in to the mains, and powering the house via the ring main when the sun shines. Bearing in mind it has islanding protection built in, to G83 standard, does this allow it to be used in this manner? I’m sure there are a number of people in the country already doing this … what do you think ?

quentingargan · 17-12-2009 7:54pm

Yes - those figures are correct according to an ESB document "Conditions Governing the Connection and Operation of Micro-generation" published in Sept 2006. You are also looking at different voltages (230 + 10% is 253V instead of 264 in G83) and frequency (48hz as against 47hz).

Is your house, or the local network going to blow up if you plug in a PV with the G83 standards? Nope. As far as I know, ESB has already permitted a number of installations in the past to go ahead with G83. However, I think with the new feed-in tariff they may have decided to throw a strop. You can't help wondering why we need a National Variations to EN50438, but maybe someone on Boards with more knowledge can give us a reason why Ireland has to have a unique code (other than someone being pernickety)

Also by the way, the G83 re-connection time is 3 minutes, whereas EN allows you to set the system live after just 20 seconds - one of the few advantages with the hassle of getting inverters re-programmed and certified is that installing and testing we don't have to hang around for as long.

You could go ahead with a G83 inverter I suppose, but if your PV array is of a reasonable size, and the house is unoccupied during the day, the chances are that you will be missing out on a fairly substantial feed-in tariff and giving electricity FOC to the ESB. There is a company with a device which ensures that dump loads cut in and you never actually export power, but this is almost as expensive as an EN inverter, and then the electricity can only really be dumped as heat, which you may not want during the summer, and which can be bought using oil etc. for just 7c per KwHr, whereas the feed-in tariff would be paying you 19c.

If you PM me, I can give you a phone number for Fergus from Allied. He may have some of those inverters around. Q

Jim Martin · 22-12-2009 11:20am

Is this any help?

http://www.futurenergy.co.uk/turbine.html

Mahatma coat · 22-12-2009 12:09pm

anyone know anything about Solar POWER inverters, most of the rhreads about solar are solar heatin, I need a new solar invertor for the bush gaff as the current ststem aint cuttin the mustard fir weldin and stuff, Have a few M2 of cell and a shedload a batteries, need new invertorythingyrecomendation, any ideas?

quentingargan · 23-12-2009 2:04am

Mahatma coat wrote: »

anyone know anything about Solar POWER inverters, most of the rhreads about solar are solar heatin, I need a new solar invertor for the bush gaff as the current ststem aint cuttin the mustard fir weldin and stuff, Have a few M2 of cell and a shedload a batteries, need new invertorythingyrecomendation, any ideas?

I use a Trace inverter. I've a bank of forklift batteries and the Trace converts the 24V to pure sine wave 230V AC at up to 4.5kw. However, I have heard quite a few people recommending the Outback range of inverters, from a company founded by a few engineers who quite Trace and set up in a new shed "outback". Q

14-07-2010 8:22pm

Hi, Has anyone sourced a 2kw grid tie inverter, just wondering what the cheapest solution is to hook into the grid.

Thanks

Cheap grid-tie inverter?

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