macafrican

The Atess Bypass Cabinet says and I quote: “This module is only needed when connected DG and grid at the same time” and in regard the status lights “only when the system is connected with DG and grid simultaneously are there three indicators”. The bypass does have two contactors but it is so bad at the switching that surges blew PCB in chillers and aircons and also some power supplies. To add insult to injury, the Atess system would not allow solar to run with gennie and we had to force this outside Atess. And then for the incredibly stupid part of their smartgrid : when gennie is connected, the PCS does not dynamically change the charge rate so as to throw everything it can at battery (subject to my max charge rate of 300kW). So if gennie happy place is 325kW, solar is doing 175kW and loads are 250kW it will not throw 250kW at the battery. You have to set generator max (so mine say 350kW), and set charge under gennie to 50kW then you have up to 300kW loads and if your loads momentarily spike over 300kW the Atess system opens generator contactor in bypass cabinet! If loads dropped and you could be taking 150kW from generator to battery, it doesn’t. It would take me 6 hours of gennie doodling along to get back 300kWh into battery :[ That is beyond stupid. They had the nerve to suggest I replace my generator with an 800kW gennie so that I can run max at 650 and set charge limit at 300kW. The way we will do it is generator connects via fast breaker to the load bars. When instructed, the new controller starts gennie and nudges voltage and frequency to sync with what the bypass cabinet is passing to loadbars. When gennie and bypass are in sync, the controller closes the fast breaker and runs the generator at fixed 300kW or so through governor on the Scania and gennie and bypass will stay locked in sync until gennie stops. During this time, if grid is not down, we are still taking throttled say 75kW from grid. If loads are 330, the bypass still supplies 30. If loads drop to 200, then bypass cabinet sees negative load of 100. That 100 + the 75 from grid and say 125 from solar is then passed into battery bank, until battery reaches 75% which is when controller removes the generator. Some people panic about back-feed : it is impossible while the battery has 150kWh space and is charging at 300kW. Some people panic about negative load. In many factories and farms with their solar remote from their LV Distribution room, the grid tied inverters are connected to the house loads 100’s of meters away, and in sunny quiet periods, “load” is often negative. It is not a problem, that negative load flows back in same way that a site’s surplus solar flows back to council as negative site. The important thing to have is that a signal immediately shuts gennie if the PCS goes down.

NO!! If you have more than 4.6kVA per phase exporting to the grid, you are entirely in breach of NR097:2:2023. In summary, small scale embedded generation on a shared low voltage feeder must not, for technical reasons, exceed 4.6kVA per phase. Those rules go back a decade. what I have seen allowed: if your council says it is 4.6kVA at dc level, they are wrong, the regulation refers to AC export not DC generated. So you can argue that 5.5 solar is 4.6 ac. if your council is progressive, they will allow you to install a lot of solar as long as your inverter is limited to export no more than 13.8kVA three phase and at unity. what some people do is split their AC into a public db and a private db. Nobody has any say over how much solar you install that sees a private db with loads that see that private db. You can then still do the 4.6 per phase on your public db and many guys put the battery bank shared as that counts as pure isolation between the private and public board. You will be fine if the inverters on private db can not in any way export AC to grid. this will also be a trick when tariffs get rebooted. So you do the split and downgrade your public db to the smallest available in your council residential tariff, thereby paying for say a 20A public connection even if you have 150A private db with very big solar. You leave a 20A charger on the public board that only gets activated when you really need grid.

Abd7: I can post some pix, but it is basically just a bunch of cabinets and a lot of cabling. Is there any particular aspect you want to see the details of?

Steve: I am not a sparky but I’ll try answer. Max load is typically in summer is about 320 kVA but I would say average year-round weekday load 9AM is about 240. According to all 4 people that answered tender and according to Atess system documentation, the Bypass Cabinet can do Generator parallel to Grid. It may sound like stupid thing but in our business case we would want to run capped grid plus solar plus generator concurrent. Either way, despite two contactors in Bypass Cabinet, Atess cannot run gennie and grid concurrent. So for that part of problem I am taking it away from Atess. I disagree that you cannot run grid and gennie parallel, thousands of sites do that all over the world every day. With a new controller and fast breaker my gennie will run sync mode with the output port of Bypass Cabinet, in effect my loads largely disappear and at times are negative. There is no ATS in this setup. Loads can peak around 320 and the 420 gennie seems happy at 300 so I’ll run it sync mode fixed governed 300 until SOC hits 75% There was an option to go Gennie:Rectifier:Battery but $$$$$$$$. Side-benefit is if entire Atess is FUBAR it will take a minute to be able to run loads off gennie alone. Simplest for me is in that disaster I open Output port on Bypass Cabinet, change gennie from Sync Governed to Load Following, start gennie and close the CB to load busbars. I could automate for that scenario but besides cost I prefer manual method. maybe a step back explains why we work like this. My council charges R415/kVA for highest 30min grid demand in month. I use smartgrid to cap grid at say 100. If it was a bad week in terms of loadshed and solar it literally pays me to run 300 on gennie for 5 or 6 times a month an hour than lift my grid cap. Gennie for me is about R1000/ph so 20h is R20k. Lifting grid cap to 300 is R80k. I never understood power factor but despite the promise that Atess will sort the PF that my grid presents to grid, it is cr4p at that. When inverter was charging or discharging hard, my PF at grid MV level was around as low as 0.64. So my 80kVA inverter cap presents as 120kVA on my invoice!! I reinstated my old and very large Power Factor correction and now I stay 0.98 to 1.00. Whatever is happening I don’t know, but if there is a fight then my cupboard size capacitors win the fight against the Atess bible size capacitors very fast.

I’ll presume you mean 30kW solar not 30kWh inverters. You then assumedly also must be commercial on MV connection, else whomever connected your 15 never mind the 30kW on a shared LV connection is in big trouble and so are you if anything goes wrong!

They cannot charge a user with solar a different tariff than a user without. (They can levy an admin fee for reverse billing but that is tiny or zero if you paid for the smart meter). What they will do is design the tariff that both users are on, in a way that the user without solar is not in effect subsidizing the user with solar. The laws and regulations require tariffs that are non-discriminatory and cost reflective. I have taken council to Nersa and won, though it took two years.

There are places where that is in place by way of wheeling. So Acme buys energy from SolaRus and basically council charges a toll fee for using its reticulation. Putting in place new reticulation would be insanely inefficient. Where that gets hairy is whether the wheeling is firm or not = whether council charges NMD and Demand fees on Acme’s full 2MW connection or the half that SolarUs is not providing.

It is inevitable that end-user tariffs will change to reflect realities. You’re naive if you expect that you can connect solar, over-generate in the day and draw at night and only pay the for the net kWh consumed in a month. The grid is not your loss-less and free battery and I won’t subsidize your model. There are idiots with solar and storage that after evening loadshedding run their loads from grid AND recharge their batteries at 1C, in effect presenting double the kVA load on the rest of the country. Stuff that! By FAR the bulk of power and energy is delivered under Time of Use tariffs whether that be to metro or council or large Eskom direct customers. That involves a NMD fee per kVA, a monthly peak demand fee per kVA, peak/standard/offpeak kWh fees and half a dozen other minor charges. A few small towns are not on Megaflex. I’ve done large solar since 2013 and my town was a bit silly at the beginning, giving us 1:1 credits. I say silly because that ignores that they have the cost of reticulation and maintenance. That party ended and they went stupid the other direction by slashing kWh (to 115c/kWh) so that solar is compared to that not 275c/kWh and because they know there will be a half hour somewhere in the month that the sun don’t shine, they smacked R415/kVA peak demand. My response was adding more solar and more storage and grid shaving because I’d be stupid not to. So now have 425kW solar and 600kWh battery on one of my transformers, will do the others this year. A fair system imposes a fixed fee based on the size of connection you want available (they reserve and pay for that NMD with Eskom), a variable fee based on that month actual peak kVA (they also pay Eskom for that) and then a Time of Use tariff for kWh. The fastest way we get people to swap power demand out of peak periods (when the country is paying for R8/kWh peaking diesel and implementing loadshedding) is that peak period energy costs R5/kWh and off-peak costs R1/kWh. Maybe in a year or two my council pays me to inject 200kVA in peak periods. I can program that and then recharge between 11PM and 4AM. If they deducted 100kVA from my demand fees for the 200kVA that I wheel to them plus they pay me half their Megaflex peak cost per kWh, they score and I score. Smarter tariffs need not be bad for consumers, it can also open up benefits.

We had a lot of solar from early but that did not solve the problems of (1) solar throttle in loadshed (2) tariffs that target solar because council knows there will be THAT damned period of high loads, low solar. My council in 2024/25 year is R508/kVA. Hit 300 loads even once that month, over R150k hit. The site generates about 75% of its consumption, so our kWh net from grid is small. We asked 5 people to tender and most came up with Atess and variety of batteries. We went 500kW Atess plus 600kWh IES battery bank. 500kW leaves headroom for growth in peak demand that is around 330kVA. The kit sits in nice solid rooms with thick walls and concrete slab for roof. Battery room can take about another 400kWh. Another room has the PCS and isolation transformer. Bypass Cabinet sits in LV Distribution room which was where grid and solar were. Beware : the 500kW Atess bypass cabinet has 1250A breakers, so your cables to PCS+Transformer have to be big. One business goal was seamless avoid generator, which is working well. Have not needed gennie since end of September when we were running R80k a month in diesel. The primary business goal was capping grid. We now cap grid at under 100kW, which saves us say 225 kVA peak or over R100k a month. If council reverts us to Time Of Use tariff, we can change rules to run off battery in peak tariff periods of day. The project is big and complex and we had our challenges in terms of Promise meets Reality. The only way to get acceptable power quality was reinstating the very large Power Factor Correction we had before smartgrid. They said they’d handle it, but just looking at their capacitors versus what we had, is like a can of Red Bull compared to a Heineken keg. Since then, power quality solved and PF measured at council MV level at full load is over .98. We had to tap dance outside system to make solar (SolarEdge not Atess) work like it should and can. If loadshed is after 10AM in sunny months, we don’t touch battery and in fact have to throttle solar if battery is over 95% Today it rained all day so little solar even from the 425 on that network. We kept grid cap in place and dropped battery to about 70% so despite nerves, it worked. Last remaining tap dance is a rational way to integrate generator. The Atess approach is pathetic, they may as well tell you to put an ATS between bypass cabinet and house loads. Looking at two routes, will update how that goes.

Mine are factory-size but try Breezair, pretty sure they have a residential size indirect evaporative cooling system

Have you looked at indirect evaporative cooling? They don’t add humidity, use low amount of energy and you could do a unit that has its splitter in roof space and octopus legs to pump fresh cooler air via bedroom ceilings. If I could redo my house I would go that route as I really hate sleeping with aircon and evaporative air is new fresh clean cooler air.

I am 9 months into a fairly large Atess system (500kW battery inverter plus 600kWh battery and 625kW solar). We had some issues of reality vs promises but solved most of these outside the system - eg power factor correction you will want to keep your old PFC as Atess is terrible at it. Main hurdle that now remains is Atess generator integration. our primary paybacks are (1) capping grid as we have extortionate peak kVA fees so to save R100k (per month) by avoiding the few times a month when loads are 300+ and solar is small, we cap grid at 80-100; And (2) not running diesel - have not since September even stage 6; and then (3) increasing solar self-consumption by only exporting if battery 100%. We’ll later get smarter and cap grid even more in advance of most days we export midday, but first want to walk before dancing. Any event, the scenario exists where it pays me to run the Scania gennie for a couple of hours when battery is low, to avoid extra R100k a month in peak demand fees. the standard Atess approach to generator integration is terrible. Manual says can run grid and gennie parallel : that is an admitted lie, it cannot. The contactors they use to switch grid and generator also cause huge spikes at begin and at end. Plan was run gennie from 25% battery SOC to 75% SOC and then cut gennie. Unbelievably, while generator runs, Atess cannot dynamically change battery charge rate based on gennie plus solar minus house loads. We also have to trick solar to run with gennie, from outside of system as Atess cannot. so two options. Expensive route is Gennie:Rectifier:Battery, probably run Gennie at fixed output of 200/250kW to keep new cables and rectifier investment to a sane number. Other route is with the right controller, sync the gennie to the house loadbars being supplied through bypass cabinet, again running Scania fixed output say 350kW. So this way Atess does not even know about gennie, it just suddenly sees very reduced house loads (or potentially negative house loads), but for rest it continues taking throttled grid, fullspeed solar and throws any excess at battery. Risk here is we MUST cut gennie immediately if inverter goes off. Fast CB is there for that. has anybody done something similar and can share war stories please?