SunDave
Solar Enthusiast
Hmm. Complication is the friend of cheats and swindlers. Not honest people so much. A simple rate adjustment for high demand times would suffice, but be too simple apparently.
Ive had solar for a year and now the utility company charges a demand fee... not cool.
- Thread starter vwaudiguy
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vwaudiguy
New Member
I'm going to quote that in my next correspondence with the power company.
wattmatters
Solar Wizard
Oh, it's done after "extensive consultation".
But yes, you are right. If the aim really is to dissuade consumption during peak periods, then the simpler the price signal, the more effective it is likely to be.
OzSolar
Whatever you did, that's what you planned.
That is great!!
I know most of us solar folks might not like it but it would sure simplify things if the connection fee (metering charge, etc) was upped to $50 and included something like the first 250 kWh and 10 kW of demand.
Those are almost random numbers but the point is that it would be tremendously simpler for everyone to figure out thier bills and the utilities might stop trying to heap random fees on solar customers. It wouldn't be a great deal today but I'm thinking of a future where they've got so many fees for solar customers that the only way you save save any money is to go completely off grid.
wattmatters
Solar Wizard
I'd already initiated a change of retailer last week but I just got notice from my current one of a rate change taking effect a bit over a week from now.
The daily supply charge they want is A$2.80/day (A$1,020/year)! That's just a supply fee, no energy. The distribution company (poles & wires) charges them $1.26/day.
The new retail plan I'm moving to is charging $1.45/day.
That's what we pay for our minimum bill roughly $30/mo USD to remain connected to the grid.
To be fair here, most of the bizarre charges and details on our bill (SDG+E) comes because laws have been passed that require those items to be listed for "ratepayer transparency."
Scrutinizing the fancy new appearance of this month's bill with info-bubbles and multi-color graphs, one can discover in the much smaller print on the back that the Demand Charge per kW has jumped 30x from $0.10 to $3.00.
First thoughts are that some contactors with an NC dry contact switch section as a quick and dirty workaround. For example: if the dryer element is ON, the water heater element cannot turn ON. Additional loads could be added and arranged in a most to least important hierarchy. Control wiring and contactor switching noise would be a downside.
First thoughts are that some contactors with an NC dry contact switch section as a quick and dirty workaround. For example: if the dryer element is ON, the water heater element cannot turn ON. Additional loads could be added and arranged in a most to least important hierarchy. Control wiring and contactor switching noise would be a downside.
BackyardBandit
New Member
I believe this is the problem some companies are trying to solve with smart home management panels and load control panels.
Hedges
I See Electromagnetic Fields!
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A dimmer circuit (Triac switched on part way through the half cycle) could vary dryer, water heater, etc. wattage to clip peaks and fill in valleys.
This would be OK for the individual, not OK for everybody on the grid.
Depending on the tie window used for Demand Charge, on for a few cycles and off for a few cycles with SSR (aim for zero crossings) would accomplish the same and could be distributed over all customers with random timing, presenting a cleaner load.
As home batteries proliferate, they can accomplish same at much greater cost and complexity. Yet could be cheaper and simpler to deploy.
Well, maybe not. Interrupting water heater can be done at breaker panel.
Do you actually need fast recovery by water heater (is it small, and you have several teenagers)? If not, just feed it 120V, reducing its draw by 75%. If it is on less than 12 hours per day, add a diode in series for additional 50%. Or put on a timer to run during a low time in the night.
Add a diode in series with refrigerator defrost element. Turn off icemaker.
But this demand charge is just a game, or a money grab, when applied to regular non-PV customers. PV customers are a special case, not a fair-weather friend to the utility, they only ask for power during poor weather, or in the evening when sun goes down. But for non-PV customers, their loads may peak at times because that is how thermostats work, but distributed at random in time, they are not a problem.
Only time of use, not demand, is actually beneficial for application to typical consumers.
Best thing we can do is observe how government and utilities stick it to the (little) man, and game the system. Let them finance the grid with Demand Charges and the like, while we sidestep to avoid it just as we did for years with GT PV.
This would be OK for the individual, not OK for everybody on the grid.
Depending on the tie window used for Demand Charge, on for a few cycles and off for a few cycles with SSR (aim for zero crossings) would accomplish the same and could be distributed over all customers with random timing, presenting a cleaner load.
As home batteries proliferate, they can accomplish same at much greater cost and complexity. Yet could be cheaper and simpler to deploy.
Well, maybe not. Interrupting water heater can be done at breaker panel.
Do you actually need fast recovery by water heater (is it small, and you have several teenagers)? If not, just feed it 120V, reducing its draw by 75%. If it is on less than 12 hours per day, add a diode in series for additional 50%. Or put on a timer to run during a low time in the night.
Add a diode in series with refrigerator defrost element. Turn off icemaker.
But this demand charge is just a game, or a money grab, when applied to regular non-PV customers. PV customers are a special case, not a fair-weather friend to the utility, they only ask for power during poor weather, or in the evening when sun goes down. But for non-PV customers, their loads may peak at times because that is how thermostats work, but distributed at random in time, they are not a problem.
Only time of use, not demand, is actually beneficial for application to typical consumers.
Best thing we can do is observe how government and utilities stick it to the (little) man, and game the system. Let them finance the grid with Demand Charges and the like, while we sidestep to avoid it just as we did for years with GT PV.
With a little digging, this is a problem I can implement a basic v.1 attempt with parts on hand.
240V NC relay coil, powered by the dryer element to interrupt the control signal to a water heater contactor.
Quietly tried the 120V water heater trick but didn't make it through household acceptance. I do think that a timer would make it harder to detect!
Hadn't thought about a defrost diode; might have to try that one!
240V NC relay coil, powered by the dryer element to interrupt the control signal to a water heater contactor.
Quietly tried the 120V water heater trick but didn't make it through household acceptance. I do think that a timer would make it harder to detect!
Hadn't thought about a defrost diode; might have to try that one!
Hedges
I See Electromagnetic Fields!
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Really! They used enough water to notice!
Consider tempering valve and higher temperature setting.
The one in my shower was nice for a decade, but eventually jammed up.
You could mount a tempering valve on outlet from water heater.
I haven't tried the diode (make sure it is sufficiently heatsinked).
Another way to get 50% would be wiring top and bottom elements in series. But separate elements with full power at top may be how it gives quicker partial recovery.
Rather than tapping into dryer, you may be able to implement that at electrical panel. Could control from multiple loads e.g. dryer and range.
You may need to post a sign on dryer asking it not be used during the time people are showering.
Consider tempering valve and higher temperature setting.
The one in my shower was nice for a decade, but eventually jammed up.
You could mount a tempering valve on outlet from water heater.
I haven't tried the diode (make sure it is sufficiently heatsinked).
Another way to get 50% would be wiring top and bottom elements in series. But separate elements with full power at top may be how it gives quicker partial recovery.
Rather than tapping into dryer, you may be able to implement that at electrical panel. Could control from multiple loads e.g. dryer and range.
You may need to post a sign on dryer asking it not be used during the time people are showering.
wheisenburg
Independent Solar Consultant
I looked into this. Generac make prioritized load shedding modules. They are simply wired inline with the appliance being controlled. Unfortunately it appears that the master controller that decides when load needs to be shed and how much is in the generator. There could also be some issues with doing load shed on some items like A/C compressors. A thermostat has some timing on it so that is will not turn a compressor back on for say 2 minutes after a power failure. This allows the pressure on the high side of the compressor to bleed down before the restart.
Sol Arc also has a load management module. This gets mounted near your panel. Then you route your wires through the controller and back to the main panel where they are spliced back to the original wire that goes to the load.
Unfortunately, they are still working on it. I am hearing from Sol Arc that it will be available in 3-4 quarter 2024.
You might be able to "Roll your own" load controller with some contactors, some sensors and a PLC (Programmable Logic Controller) device. A PLC allows you to wire up sensors like say current and voltage sensors. Then you can wire output devices like contactors on the output side. You need a 24 Volt DC power supply to run everything and a cabinet to put it all in. Once all the hardware is together, you have to program the PLC controller with the rules. Trying to implement the required logic with relays means rewiring every time a rule needs to change. These PLC devices are used for industrial and building automation.
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Yes, and not a small tank either!
That thought has been percolating . . .
Yes, they are separate and full power, and had wondered if might be possible as a way of reducing by a smaller fraction but hadn't tried it yet.
Let's just say I need an autonomous implementation.
I think DIY is in the name of the forum!
The Generac load shed module is intended to prevent overloading the generator by monitoring the frequency. Overload the generator and it will slow down thereby reducing frequency and tripping the load shed. That's not going to work on the grid.
Quattrohead
Solar Wizard
I tried a big old diode to cut the power in half on my dryer heating element but it really did not work well at all, the dryer buzzed like crazy and the whole electrical system was grumpy.
Quattrohead
Solar Wizard
Yes a couple of sets of contactors and you can make your own load shedding device. Sense power from the stove but do not turn that one on and off because it buggers the clock up, control the dryer and the water heater.
You could also look for or make your own low power elements for your dryer and there are lower power elements available for water heaters.
You could also look for or make your own low power elements for your dryer and there are lower power elements available for water heaters.
Where can one find info on how to set up the contactors?
Hedges
I See Electromagnetic Fields!
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Just dryer heating element buzzed? Standard approach for some hair dryers, I thought.
Was it an Inverter that was grumpy? (power quality affected, could make other parts of dryer noisy.)
I suggested it in the context of abusing the grid, "demand charges".
For inverter loads, many aren't nice and I want PFC.
Motorized Variac, or taps to a transformer, could adjust heating loads.
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