Power shares

[Snoopy]

I wrote my own (system); I have solar panels and a small battery from Enphase, and developed an app on a wall mounted tablet that communicates via WiFi every 2 seconds with the inverter to get some of the information (how much comes in/goes out of the house, how much the panels produce), and also with a micro computer with clamp over the battery cable to see the flow to/from the battery. I also ask my retailer (Flick) every 5 minutes what the current variable power price is (changes every half an hour), and with that I can produce an up to date picture, something that should really be provided by each solar system. I can immediately see when a cloud blocks the sun, when my partner switches the airco on, etc, plus how much approx I have spent on the day so far. And the system also automatically decides when it is a good time to switch my spa on, avoiding the morning and evening peak hours. I also write every minute a record to a remote database for long term reporting. All in all a nice hobby project, but it did take me quite some time to develop.

"Love it! Now package it all up nice and neat and find a market for it ".

Not that easy unfortunately. I had to break the password of an encrypted communication before I got the data from the inverter - could be changed anytime! But I do love it that at a glance I can see big red bars (consuming) or green bars (producing) that give a visual indication of the current state. And it does save some money too, especially with Flick paying me for my solar excess at the market rate, so some (usually summer days) I am actually earning a bit from my investment.

Bart, that is amazing what you have done. A couple of questions. I had a look at the 'Enphase' website. The 'basic battery' there is pretty small at 1.2kWh. At $2,900 it doesn't sound that cheap either for the capacity you get.

https://www.hiteksolar.co.nz/product...ery-1-2kwh-new

That would only store enough energy to run a 2kW fan heater for half an hour. I take it your 'small' Enphase battery set up is bigger than that?

I find it quite extraordinary that your power use data is encrypted by your supply network. I mean, they have a monopoly, right? There is no-one going to build an alternative network to supply power to you. All alternative retailers you may choose will have access to whatever power consumption information they need if they ask. So surely network power use should be public domain knowledge?

I have so far resisted going solar myself because of the mis-match between when the peak energy is generated and when it is used. My thinking has swung more towards a small vertical access home windmill coupled with a battery. They aren't very efficient in windmill terms. But they are quiet and relatively cheap. And of course wind energy is 'free' so absolute efficiency is not the most important thing. Did you ever consider a small 'home windmill' for yourself?

SNOOPY

[RTM]

Solar water heating is worth considering. Not as fashionable these days.
Last year we installed a SolaHart system. So far really good, very pleased. Just gotta hope it lasts now.

[Snoopy]

Solar water heating is worth considering. Not as fashionable these days.
Last year we installed a SolaHart system. So far really good, very pleased. Just gotta hope it lasts now.

The big advantage of solar water heating is that your 'battery' (hot water cylinder) is relatively cheap. When I had to replace by hot water cylinder a few years ago, I actually bought one with the connections that means it is solar water heater compatible, should I choose to go that way. But in reality I don't use that much hot water which is why I haven't proceeded. That and the fact that battery storage is becoming relatively cheaper. So the signs were pointing to it being better for me - and the power supply companies (to keep this thread on topic) - to have an arrangement where I could store 'cooking power' and 'space heating power' generated 'off peak' so that I could then use it at 'power peak' time. I reckon the marginal cost to supply me energy deeply off peak must be close to the spot wholesale energy price. I know the lines companies and Transpower do not agree. But I think they are wrong. If I (and enough like me) could help even out the country's energy consumption by pulling all daily consumption power in off peak, there would be less thermal stress in the system as the wires and switches and transformers had less energy fluctuation to deal with. That and the fact that the lines system could be sized for a peak load that is smaller. As it stands, Transpower and my lines company together seem intent on charging me 20c per unit, regardless of how much power I pull down over their lines and when. That means 'off peak' power discounts theoretically max out at around 25-30% (actual discounts are rather less). I believe that if the network providers came to the party, then the off peak power price discount could, and should, be much greater than 25-30%. Bigger off peak discounts should make home battery storage economic, even to those customers without solar panels or a windmill on their roofs.

SNOOPY

[Bart]

Bart, that is amazing what you have done. A couple of questions. I had a look at the 'Enphase' website. The 'basic battery' there is pretty small at 1.2kWh. At $2,900 it doesn't sound that cheap either for the capacity you get.
SNOOPY

sorry, maybe I was not clear. The communication to the inverter is envrypted, the power supplier does not give live data, but with 48 hour delay I can get half hour values from them. The inverter sends the data to enlighten, where you can see the summarised data with about half an hour delay. It seems you can get some better stuff, but have to pay for it - yes, to see your own data!
As far as the Enphase batteries are concerned, yes, they are small, and I have only 2 of them (bought at a time the did cost me about $2,400 each). Apart from being small a major drawback is that they can only charge/discharge at a rate of about 270 Watt, so when the sun shines and I do have excess power it still takes nearly 5 hours to fully charge them. I do charge them at night when the prices are a bit lower, but the times of near zero cost in the middle of the night have well and truly gone. Here is a snapshot of the current situation - my panels are producing 3,123 Watt, 2,466 of that goes to the house (air conditioning running to heat the house, a freezer was just opened, and some hydroponics pumps are running), 537 go to the batteries that are 47% full, and I'm exporting a meagre 119 Watt. Total cost for the day $1.51 so far for 6.388 kWh imported and 2.451 kWh exported.
Finally a small windmill, yes, I have thought about that, but there are limits to what you are allowed in town, and from what I hear it is not cost effective, and would have to be separate from my Enphase system.

[kiwico]

I believe that if the network providers came to the party, then the off peak power price discount could, and should, be much greater than 25-30%. Bigger off peak discounts should make home battery storage economic, even to those customers without solar panels or a windmill on their roofs.

SNOOPY

There are some big off peak discounts out there - we're on 14.5c off peak and 30.86c peak, both being low user. Every time someone knocks on the door trying to give me a deal on power our cheap off peak means they fail dismally.

On the other hand, it means solar isn't really a goer as the opportunity cost calculation has to complete with us heating our hot water so cheaply. But I am interested in battery technology as anything that moves our 50% peak use to off peak prices can't be bad.

[Bart]

There are some big off peak discounts out there - we're on 14.5c off peak and 30.86c peak, both being low user. Every time someone knocks on the door trying to give me a deal on power our cheap off peak means they fail dismally.

On the other hand, it means solar isn't really a goer as the opportunity cost calculation has to complete with us heating our hot water so cheaply. But I am interested in battery technology as anything that moves our 50% peak use to off peak prices can't be bad.

With Flick at the moment this is my cost structure:


a fixed component of 30 cents per day which consists of:
-15 cents for the meter
-15 cents for the network


and a variable component per kWh which consists of:
-12.723 / 23.323 cents during off-peak / peak hours (7-11, 17-21)
-market price (0-999 cents)


the first part of the variable component consists of
-0.580 cents for the meter,
-0.113 cents for the EIA levy
-4.080 cents for Flick administration
-7.950 / 18.550 cents for the network

the market price changes every half hour and I have seen the whole range - my monitor program sounds an alarm when it rises above 100 cents to draw our attention to that situation (once every 3 months?).

For the power I return to the grid I get the market price, and do not pay any the others costs (at the moment).

Unfortunately I can not instruct my battery to return power to the grid, could be worthwhile at times when the sun is shining and the market prices are high. With Enphase I also have to fix the night time hours I want the fill my battery; again would be worthwhile if I could decide to do so when the power prices are low.

[Bart]

I guess there could be a market for a battery with artificial intelligence - being aware of the varying power prices during the day - that could decide when to charge / discharge, the latter not only for consumption but also for export to the net. I don't think it is available though, and doubt with the current cost structures it would be cost effective.

[Bart]

Well I got that wrong. Without the need to inspect my own power box regularly, my brain told me the old metering device was still in there! I have just been out and checked. There is a single digital display with no spinning disk in sight! Up top of the plastic casing , visible through a transparent plastic window, the single digital display flashes numbers representing different sequential things it is measuring. The unit is branded:

Natural Gas Corporation EDMI Mk7 Atlas (Made in Singapore)

Down below the display window, the grey plastic body bulges out into what I can best describe as a 'paunch'. Big enough to hold some kind of transmitting device? Maybe. But it is all tied up with cable ties with the threat that anyone who disturbs them will be tracked down and killed. So I am not so keen to explore further! This means I am not as smart as I thought, and the meter is smarter than I thought. But I would still back myself against that meter in a game of tic tac toe. I still find it hard to believe that that innocent little plastic box is spying on my power use once an hour though. I must retire to the boudoir to check for any 'reds under the bed'!

SNOOPY

I tam sure my meter (marked Vector EDMI Atlas) sends half hourly usage data once a day via a cellular phone connection. It also has a pouch and a single digital display with changing numbers showing live data. Because it only transmits once a day I get that data from Flick one (and sometimes more than one) day later. Obviously there is (currently?) no way to access the data live, which is why with the install of my batteries they had to install clamps over the cables to measure the incoming / outgoing flow of electrons. I used to have a meter with a spinning disc, and even then my provider could give me hourly power usage, albeit at least two days delayed.

[Carpenterjoe]

https://www.stuff.co.nz/national/300...to-hydro-power

[LaserEyeKiwi]

I guess there could be a market for a battery with artificial intelligence - being aware of the varying power prices during the day - that could decide when to charge / discharge, the latter not only for consumption but also for export to the net. I don't think it is available though, and doubt with the current cost structures it would be cost effective.

on last weeks Tesla earnings call, Tesla announced that their auto-bidder system will be expanding to consumer Powerwalls, which will enable owners to put there batteries into a battery pool that takes advantage of high & low spot power pricing to buy & sell power for profit via an automated software solution. Not sure when it will roll out in New Zealand, but hopefully it is coming.