Intelligent Switching Devices, based on Renewable Energy power generation

lazza
lazza Solar Expert Posts: 336 ✭✭✭
in Advanced Solar Electric Technical Forum #1
HI Forum

We're currently looking at ways to give signals to consumption equipment to manage the renewable energy production optimally.

As I have mentioned in other posts, Spain does not currently have compensation in place for net metering, and we dont really want to rely on spanish politicians/administrators for our future business plan (however reliable, honest and competent they may be ... ahem).

Hence there are 2 particular cases that we wish to investigate:

a) A device that recognises when the PV grid-tie inverter is supplying more energy than is being consumed within a home (and hence is injecting into the grid)... this would link to a relay transfer switch that would switch on a resistence heater in a water tank. The idea is to use the excess energy to do useful work in the home and not be a gift to our beloved electricity companies. This device would need to recognise ENERGY FLOW DIRECTION.

b) A device that recognises the power being generated by the PV grid-tie inverter.... and once it surpasses a certain level, for example 500W... it gives a signal to a relay transfer switch to turn on the water pump (for example). The idea for this is to use renewables for irrigation and only irrigate when there is sufficient renewable energy

I do know that off-grid inverters often have "virtual swiches" with progammable criteria that can do such intelligent switching... however, this requires a more complex and expensive system with batteries...

So my question is: Does anyone know of any such intelligent devices that could be connected? does anyone know how to invent one?

Many thanks
Larry
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Comments

  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #2
    Re: Intelligent Switching Devices, based on Renewable Energy power generation

    As far as commercial products, the only one I'm aware of is the EMMA: http://www.coolpowerproducts.com/uk/index.html ...and I think it's quite expensive.

    This should be DIYable if you're comfortable with programming either an Arduino (www.arduino.cc) or a PC (Java, .NET visual basic.). Essentially you'd need a microcontroller with 2 AC current sensors + how ever many relays you want to switch, and the software to make the decisions.
    Arduino would be the cheapest route, but the software side is more restrictive.
    Or you could go for a more software friendly route with http://www.phidgets.com/, but it'll be more expensive.

    If you want to get someone to build an Arduino based unit for you, you could try these guys based in Zaragoza: http://www.cooking-hacks.com/
    BTW, if you decide to commercialise this system there is a HUGE market in the UK because of the way the FITs are structured (cheaper to use solar power than feed it back into the grid).
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #3
    Re: Intelligent Switching Devices, based on Renewable Energy power generation

    You could also use something like a TED and get the data via web calls every 30 sec or so to make the decisions on driving a controller board. Simple perl scripting could be used to make the needed calculation. You my want to have some timers to keep spikes in the data from flapping the controller. You could even get magnitude data nd trigger progressive relays to increase the loads.
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  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    #4
    Re: Intelligent Switching Devices, based on Renewable Energy power generation

    Thanks for the replies. I guess it could be quite simple to program an arduino to recognise levels of power production, but as for actual Direction of Energy flow... that may be alot trickier.. anyone know?
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #5
    Re: Intelligent Switching Devices, based on Renewable Energy power generation
    lazza wrote: »
    Thanks for the replies. I guess it could be quite simple to program an arduino to recognise levels of power production, but as for actual Direction of Energy flow... that may be alot trickier.. anyone know?

    TED has direction data, using an ardunio to access the data should be simple.
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  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    #6
    Re: Intelligent Switching Devices, based on Renewable Energy power generation

    Ok, well next question.. what's a TED? :)
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #7
    Re: Intelligent Switching Devices, based on Renewable Energy power generation

    This is T.E.D.

    Note that there are (at least) two different models. The less expensive version which cannot measure the direction of current flow (and should not be used for net metering), and a second that can (as I understand).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #8
    Re: Intelligent Switching Devices, based on Renewable Energy power generation

    Couldn't you deduce the direction just by locating the 2 current sensors in the right place? (I may be off-base here), but if you had 1 sensor (A) between the inverter and the main distribution box, and another sensor (b) between the distribution box and the consumers- then isn't that enough to know whether you're exporting? A - B would give you the current you're exporting surely.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,631 admin
    #9
    Re: Intelligent Switching Devices, based on Renewable Energy power generation

    Yes, that can work (it is still an estimate, but pretty accurate--The GT inverters still consume a little bit of power at night).

    However, most people do not have a sub panel for all of their loads (measure measure load current there), and a second current sense transformer on the GT inverter circuit.

    Most people just have a single main panel. And all of the current is summed onto the bus bars (loads and GT inverter output). So it is not possible to have a "clean" Loads-GT=net positive or negative energy usage.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #10
    Re: Intelligent Switching Devices, based on Renewable Energy power generation

    A TED 5000 has the ability to dump one second data via its internal web server on a per CT basis in csv format. That data can be accessed by any web connected device using utilities like curl or wget. Most scripting languages like perl also have libraries you can use to access http type data. It would be a simple matter to control a relay board from these results using a state engine coding.

    Edit actually TED does pretty good job on a single panel setup by summing the grid tie against the mains CT hookup to come up with a net usage number. A negative value denotes pushing into the grid.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #11
    Re: Intelligent Switching Devices, based on Renewable Energy power generation

    Just got this: http://www.sma.de/en/products/monitoring-systems/sunny-home-manager/optimizing-energy-home-management.html in the mail. Looks very promising for your kind of application. ...now to find out whether it will work my off-grid setup :)
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  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    #12
    Re: Intelligent Switching Devices, based on Renewable Energy power generation

    Very interesting, the big question.. how much does it cost? :)

    I was thinking of programming the arduino to give signals to radio controlled sockets in any case. We seem to be having a drop in installations for the next month or two.. so maybe we can use the time to investigate this solution

    Please do keep me posted with any other ideas

    Larry
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