View Full Version : Grid tie/No feed
August 29th, 2008, 3:43 PDT
Hello to all you guys
I have a question that might be silly but I just can't resist asking.
Is there a configuration of connecting a wind turbine to the grid but avoid feeding any current back to it?
August 29th, 2008, 7:46 PDT
Not that I can think of...
1. A wind turbine needs a steady 100% load to prevent over-speed (unless it is shut down mechanically and/or has a diversion load operating). For a variable output, it would need a variable diversion load attached to the AC Mains to operate correctly.
2. You would need a device like the power meter for your home to measure the "direction" of power flow before it went out of your utility lines (or two devices--one that measured your whole house load, and a second measuring the inverter's output--the difference used to control the loads/inverter output per your requirements). It would control the diversion/opportunity load (and/or turbine/solar generator/inverter output) per your requirements.
It is not that it can't be done--but is a level of complexity that has not been required by anyone--The only reason I could think of needing something like this would be for a utility that did not want a home to "feed the grid" (only a very few utilities actually have physical limitations where they cannot take back-feed--like a few areas of downtown San Francisco, CA) or if you had a generator (or AC coupled system--the system where a grid tie inverter back-feeds a standard off-grid inverter and actually charges the battery bank) that could not take back feed (or in the AC coupled system's case--needed to prevent the batteries being overcharged--but there are other ways to sense/limit battery over-charge/turn off inverter output/add diversion loads).
August 29th, 2008, 8:12 PDT
Thank you for your prompt response.
My problem is that I want to avoid the procedure involved connecting my turbine to the grid officially. On the other hand I would like to avoid buying batteries as the cost will increase significantly. Where I live the average annual wind speed is greater than 7m/s and it is a shame not to take advantage of that energy.
August 29th, 2008, 9:10 PDT
I am not sure that this would be a "legal" out for connecting Grid Tied inverters to the utility. Certainly it would be less obvious to the utility if the meter did not turn backwards between readings--but given that you have a 10-30+ meter tower in your yard with a wind turbine on top--would sort of give it away that you have something new going on...
Are you in Greece? In the US--we have enough people, neighbors, tax collectors, "legal beagles" (lawyers), and such to ensure that there is a good chance of being nailed for an illegal connection.
You could certainly "turn off" / divert the wind turbine's output on the day when your meter is read--and/or look at the meter and watch for it going "negative" the month before--and turn on some load/heater to get it back "positive".
But--in our case here, there is a chance that the utility would come by anyway and "ask questions" when our bill dropped by 80% and everyone else's remained the same.
Another way of trying to deal with the issue--is go with a "green" campaign to convince your utility/newspaper/town council/green party to let you fund a "project" to test Wind and Grid Tied (utility interactive) Inverter on your property... You can become a celebrity and possibly even get some free stuff (a Euro qualified GT Inverter, cement for your tower, etc.) too because of newspaper articles.
As always, research the wind turbine you want to install--they are not all created equal. Also, tall towers/free of blocking (buildings, trees, etc.) help a lot too.
August 29th, 2008, 15:02 PDT
you are talking of going guerilla which generally isn't a good idea. even if you do this with safety in mind at the very minimum the utility may think you are stealing the electricity. when they investigate they will find that you aren't stealing, but you have an unauthorized feeding of power to the grid.
September 1st, 2008, 3:00 PDT
Bill and Neil thank you for your replies.
My purpose is not to act as a guerilla.
In case I am feeding electricity to the grid that makes me energy producer. Then I have to issue receipts and so on. In that case, being a self employed I have to pay contributions of about 2000 euros a year…Do the maths and you will see my point (I just want to put up a 2.5Kw turbine).
And yes I am from Greece where most of laws and regulations are nonsense.
This is the reason I want to connect my turbine to the grid (no batteries) but avoid selling to the grid.
I was thinking of using a transfer switch with a small battery bank but....
September 1st, 2008, 7:25 PDT
In the US--even if you never turn your meter "backwards" (generating power out to the grid)--they still would make anyone installing a Grid Tied inverter follow the rules (and get permits/approvals) because it still has the capability of generating power to the grid and is a safety hazard if not a UL approved device.
At this point--the only other way for you to do this and meet the requirements of the law would be to install a good quality inverter and battery bank. There are inverters from Outback and Xantrex (and others, I am sure) that can be programmed to use battery power to supply the AC loads when the batteries are charged--and switch back to grid when the batteries are discharged (and, also recharge the batteries from the grid--if you want).
Unfortunately, adding batteries to your system drops your efficiency by 40% or so (battery charger, battery, inverter losses) and adds costs (battery purchase and replacements every 5-10 years). All this can double or triple your costs vs a pure Grid Tied system.
A typical Grid Tied system in the US will cost around $0.25 per kWhr (retail install, 25+ year life) and an off-grid (or hybrid grid-tie + off grid backup) will cost $1.00 per kWhr (prices are very approximate--based on retail cost for install+parts+permits, reasonably sunny area).
In the US, it took laws from the State and Federal governments to force utility companies to allow Grid Tied systems--and even then, the utilities only have to allow 0.5-1.0% of their customers to install Grid Tied systems. Pricing of power payments have also been set by law. And about the best is 1 year net metering (depends on state/utility exact billing requirements).
1 year net metering--basically, I have an "account" with the power company. I pay minimum connection fee (around $5 per month). If I generate more power than I use (say summer), I get paid the retail rate for electricty I generate and it is put into my account. In winter, when I use more power than I generate, I pull excess money from my account to pay my bill. At the end of 1 year, if I owe money (account balance negative), I pay the balance. If I have extra money (generated more than I use), the account is set back to zero (I loose the excess money).
For the consumer, this is a great deal. For the power company--they are subsidizing me via other utility customers/tax breaks.
Some utilities will charge you retail for power (say $0.10 per kWhr) and pay you wholesale for any power you generate (say $0.05 per kWhr). Not as good as deal for the customer--but probably more fair.
Unfortunately, I cannot think of any other way for your to harvest/store your power other than batteries/inverter system--unless you have some special needs (lots of water pumping) or circumstances (two ponds with 10 or 100's of meters of elevation difference where you can install a Hydro pump/generator)--where you can cost effectively install you wind turbine and harvest power.
September 2nd, 2008, 2:32 PDT
"""At this point--the only other way for you to do this and meet the requirements of the law would be to install a good quality inverter and battery bank. There are inverters from Outback and Xantrex (and others, I am sure) that can be programmed to use battery power to supply the AC loads when the batteries are charged--and switch back to grid when the batteries are discharged (and, also recharge the batteries from the grid--if you want"""
This seems to be the only way (unfortunatelly)... I was thinking of using a Victron Quatro inverter/charger with a relative small battery bank (??)a small pv array and a Samrey Mistral turbine.
Thank you for your feedback Bill I'll keep you updated with what i will eventually do...
September 2nd, 2008, 9:56 PDT
STA, is there a reason you can not just have an independent( stand alone) system , not grid tied that would power your house and not use grid power, therefore no meter issues?
September 2nd, 2008, 11:00 PDT
i dont see the point of building a stand alone system when the grid is on my doorstep. it is an unnecessary cost to spend money on batteries plus it's not so eco friendly anyway...
All i wanted was to take advantage of the high winds and avoid the need of issuing receipts (i will have to create a 'company')for selling insignificant amount of energy back to the grid. The money i will pay for contributions as self employed are far higher than what the power company will pay me back.
Thats why i was after a way of redirecting the excess produced energy before it will go to the grid.
Thanks for your comment
September 2nd, 2008, 11:07 PDT
OK , got it, bureaucracy stifles personal initiative by being set up (designed) for BIG business.
We have similar problems here with a new concept for Hydro generation called Run-of-River. Sold as a way for small projects to be developed on small watercourses, but in reality it has to be quite big before it will be considered...
September 2nd, 2008, 11:34 PDT
In the end, we usually recommend that everyone work on conservation first (appliances, insulation, double pane windows, disconnecting used loads like stereos, entertainment centers, cell phone chargers, etc.).
Conservation will generally provide a better return on your dollar (Euro) than any solar/wind system out there.
We have something in North America called a Kill-A-Watt (http://store.solar-electric.com/kiacpomome.html) meter which is a cheap and quick way to measure how much power over time (Watts*Hours or kWattHours) each of your appliances uses... Makes it very easy to figure out what is costing you the most money--and help you to decide what to do next (replace, fix, upgrade, use less, etc.).
Unfortunately, I don't know of a European version of the Kill-A-Watt (cheap/easy to use). I also have used old (surplus) electric utility meters (Euro equivalent (http://cgi.ebay.co.uk/ELECTRIC-METER-KILO-WATT-HOUR-230V-80-AMP-NEW_W0QQitemZ230278401355QQcmdZViewItem)) connected to an extension cord as an alternative to the kill-a-watt meter (for larger equipment and decades ago before the kill-a-watt meter existed). You should be able to the spinning disk and a stop watch to figure out your Watt usage (over a few minutes).
Also, if you have good sun--looking at installing a solar hot water heater for your home may make economic sense... Generally solar thermal systems are much less costly to install and can provide hot water and radiant heating (depending on your local climate conditions). Also, can be a good do-it-yourself project. Downside, higher maintenance than solar PV systems. Although, probably less costly maintenance vs Wind Turbines and Battery system costs.
Solar PV would be my next pick... Wind would sort of be last (many wind turbines are less than reliable, and wind is highly variable vs solar PV which is pretty predictable over time).
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