Measuring AC energy flow direction

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  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    Re: Measuring AC energy flow direction

    Final: with opportunity load connection. Will explain if someone might be interested.
    Attachment not found.
  • nigelhnigelh Registered Users Posts: 1
    Re: Measuring AC energy flow direction
    igor1960 wrote: »
    Final: with opportunity load connection. Will explain if someone might be interested.
    Attachment not found.

    My first post here and am very interested in this thread - I'm living in North Cyprus where we are just starting to use solar energy. The electric supply company are still getting to grips with "net metering".
    Please, Igor1960, could you give an explanation of your "final" circuit with "opportunity load connection" - what does that mean, to a layman ?
    Thanks
    nigelh
  • iPadawaniPadawan Registered Users Posts: 1
    Re: Measuring AC energy flow direction
    igor1960 wrote: »
    Final: with opportunity load connection. Will explain if someone might be interested.

    Hi,
    I like this. Thanks.
    Any explanation is welcome.
    Why not let fet's do the job or opto couplers with triac's instead of relays?

    Actualy,
    I was thinking to use three+ hall sensors, 1 at the GTI, 1 just behind the meter ( grid ) and 1 just behind each fuse to know the use for each fuse network.


    GTI
    0
    /fuse/
    devices in network
    | (node)
    |
    Inverter
  • BB.BB. Super Moderators, Administrators Posts: 29,980 admin
    Re: Measuring AC energy flow direction

    Welcome to the forum iPadawan.

    You are talking about a circuit to do the actual switching--But that is, technically, not the problem.

    The issues are:

    1) how to measure power flow in real time (possibly down to the fraction of a cycle)
    2) what does the power company (and government) think is "legal" (fractional cycle power selling, averaged over 15 minutes, etc.)
    3) once you got #1 and #2 defined--then look at the actual switching. Which, depending on the answer to #2 may not be really possible to implement without energy storage/power management.

    The utilities are not really interested in answering #2 into a simple/easy to implement solution. The utilities do not like competition from any others (home owners, co-generation plants, etc.).

    In California--The "legal answer" is that I am not even allowed to put solar panels on my home, charge a battery bank, and run my home loads from such a system (and eventually disconnect from the grid). From a "safety/power network point of view", I am doing nothing to their network--Why do they care? The reason they care is that the company has "made 30-40 year investments in infrasturcture/generation capacity/fuel contracts/etc." based on the fact that there are 100 houses in the neighborhood. If 50 of them put in off grid solar, then the costs of these long term contracts would be leveled onto remaining homes. If I go "off grid" power/co-generation/etc... The state of California requires me to pay the utility back for these "stranded costs".

    The fact I have GT Solar power system on my home is a temporary grant of immunity which will change over the next 10-20+ years--And will certainly not be the same as it is today (in the customer's favor).

    The utility has every reason to make the definition/requirements for #2 to be as complex and obscure as possible to prevent competition.

    In reality, there is no technical reason (in almost all cases) why a utility simply does not let a customer install a properly designed/permitted GT power system with a bi-direction meter--As long as the market/distribution system penetration by GT solar is small (less than 1% of local grid capacity). Over ~10%, there are real technical issues that would require active control/feedback from the utility/network engineers directly to prevent network instability issues.

    For small number of GT systems--This is simply how a monopoly prevents competition. Install an off grid solar power system on my home--I can get hit with very high charges for the privileged of going off grid. Trying to go GT Solar, start throwing a whole bunch of real and imagined requirements at the customer and let them try to figure out how to get around it--And if they do get around it, throw in some more regulations to prevent it.

    Leave a house empty for 10 years and have near zero power bill--No network stranding charges. Stop paying my power bill, the utility disconnects my power--No stranding charges.

    Tell the utility to pull the meter from my empty home--City may "red tag" my home (make illegal to live in) until my power is reconnected. Go completely off grid (no utility power), city may red tag my home too.

    This happens with other utilities too--A family when 100% recycling/generating no wastes--Stopped garbage collection--City attempted to red tag home (garbage company got law written). A woman disconnected from city water (used well/trucked in water) and city sued for sewer charges (sewer charges were paid via water bill).

    While it can be very interesting on how to create a "switch" that can meet the "do not sell power" to the utility--Without detail specifications/requirements, the actual design will probably be affected by rules implemented by the utility.

    Stephendv recently posted about a couple of companies that have created products that prevent selling power to the grid for GT power systems (GT power is illegal in Spain). It would be interesting to see how they solved the the issue.
    stephendv wrote: »
    There are commercially available devices that will match consumption with PV production. They all use a resistance heater of some sort, e.g. hot water heater and control the power being sent to it so that it matches your excess PV production. Here are some links:

    - http://revosolar.com/solar-shop/es/accesorios-/188-inhibidor-inyectar-en-la-red.html
    - http://www.immersun.co.uk/
    - http://www.coolpowerproducts.com/uk/index.html

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Measuring AC energy flow direction
    BB. wrote: »
    I am not even allowed to put solar panels on my home, charge a battery bank, and run my home loads from such a system

    Where do they draw the line? What about solar powered calculator or wristwatch? What about solar landscape lighting? What about solar powered electric fence chargers? What about a solar freezer (with or without battery)?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 29,980 admin
    Re: Measuring AC energy flow direction

    OK--vtMaps--Force me to look it up :p:

    http://www.pge.com/tariffs/tm2/pdf/ELEC_SCHEDS_E-1.pdf (Residential Flat Rate billing)
    SOLAR GENERATION FACILITIES EXEMPTION: Customers who utilize
    solar generating facilities which are less than or equal to one megawatt to
    serve load and who do not sell power or make more than incidental export
    of power into PG&E’s power grid and who have not elected service under
    Schedule NEM, will be exempt from paying the otherwise applicable
    standby reservation charges.

    It looks like they have changed to to 1 MWatt now--Used to be 10 kWatt in times past (when GT solar was first introduced--as I recall). Note that this is for solar only--No co-generation/generator/etc. alternative sources are exempt.

    Anyway--It appears that it is possible to leave the grid in California for a practical size home... Maybe. If/when it starts happening, I expect more noise.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonrjonr Solar Expert Posts: 1,360 ✭✭✭✭
    Re: Measuring AC energy flow direction
    BB. wrote: »
    2) what does the power company (and government) think is "legal" (fractional cycle power selling, averaged over 15 minutes, etc.)

    Any utility that charges for "true power" (most of them) allows one to legally sell back some power within a cycle. That's what reactive power does - it takes power from the line and then puts it back. And the meter doesn't charge you for what you return.

    I am available for custom hardware/firmware development

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