Alternative to microinverters

[Electrodynamic]

Siwastaja

So did I understand correctly - for you, value of sell-to-grid is 640 / 4000 = 16 cents/kWh, and value of self-use is, as always, equivalent to buying price, that is 22 cents/kWh. So "having to sell" would lose 27% of the value compared to self-use.

This doesn't sound bad to me at all, just understandable and fair. Say you are a nuclear plant or a coal power operator. It's not like you get paid for the final customer price either; there is value added in the chain, producer always gets less.

It doesn't sound bad at all and I have designed and tested some island mode micro grids which could never touch 16 cents/kWh. One kilowatt equals 1.34 HP, so it's similar to running a 3hp genset at 70% power 24/7. I'm also testing a new CHP (combined heat and power) unit this winter and I would be very lucky to break even with maintenance and fuel versus power production. Of course, the bonus of CHP is that even if we break even on fuel vs power we still get the heat for free which is nice for cold climates like Canada.

For perspective, the average off peak pool/producer price here in the last 24 hours was $20/MW or 2 cents per kWh. One kWh is equivalent to the average person on a peddle bike generator peddling flat out for 5 hours. So to an Engineer designing micro power generation systems 2 cents per kWh sounds like a miracle. At $0.02/kWh the payback period for a $1000 1kW grid tie solar setup would be 33 years. However the solar panels are losing 1% efficiency per year so the real payback period would exceed 40 years.

So I think it's important to understand no residential system is ever going to compete with power generation on an industrial scale. The only real benefit of a solar power system is independence, security and power production at the point of use or off grid.

[nctnico]

So I think it's important to understand no residential system is ever going to compete with power generation on an industrial scale. The only real benefit of a solar power system is independence, security and power production at the point of use or off grid.

I think you have a good point here. The way I start to see it is that residential solar is more like a temporary 'thing' to get more renewable energy while waiting for nuclear and large scale solar + hydrogen to catch up. Home (battery) storage is already at a point it won't make any sense real soon because many companies are building large scale batteries nowadays and hydrogen based storage is around the corner. There is no way to compete with that as an individual home owner.

[Marco]

That depends on how much monopoly rent they can get away with charging. They can get so greedy home hydrogen storage could become cheaper.

[Someone]

One kWh is equivalent to the average person on a peddle bike generator peddling flat out for 5 hours.

Oh dear, not that one again:
https://www.eevblog.com/forum/chat/a-possible-way-to-keep-your-fridge-cold-in-long-term-blackouts/msg4245910/#msg4245910
Average person wouldn't even get 1/3rd of that.

[thm_w]

One kWh is equivalent to the average person on a peddle bike generator peddling flat out for 5 hours.

Oh dear, not that one again:
https://www.eevblog.com/forum/chat/a-possible-way-to-keep-your-fridge-cold-in-long-term-blackouts/msg4245910/#msg4245910
Average person wouldn't even get 1/3rd of that.

Flat out means as fast or as hard as possible, maximum effort.
Its implied that you can't maintain maximum effort for more than 30-60s.

[Someone]

One kWh is equivalent to the average person on a peddle bike generator peddling flat out for 5 hours.

Oh dear, not that one again:
https://www.eevblog.com/forum/chat/a-possible-way-to-keep-your-fridge-cold-in-long-term-blackouts/msg4245910/#msg4245910Average person wouldn't even get 1/3rd of that.

Flat out means as fast or as hard as possible, maximum effort.
Its implied that you can't maintain maximum effort for more than 30-60s.

When neither of those data points lie at an intersection or asymptote, how could it be implied?

average person flat out > 200W, nothing adds up.

[tszaboo]

So I think it's important to understand no residential system is ever going to compete with power generation on an industrial scale. The only real benefit of a solar power system is independence, security and power production at the point of use or off grid.

I think you have a good point here. The way I start to see it is that residential solar is more like a temporary 'thing' to get more renewable energy while waiting for nuclear and large scale solar + hydrogen to catch up. Home (battery) storage is already at a point it won't make any sense real soon because many companies are building large scale batteries nowadays and hydrogen based storage is around the corner. There is no way to compete with that as an individual home owner.

I genuinely have no idea why suddenly home energy storage is being viewed as a green alternative, on a global scale, as a solution.
Dave's installation is a prime example, he barely uses a few dozen percent per day, once. It's not efficient usage of batteries.
The same batteries used in a device on utility scale could be sized to charge and discharge several times in a day and serve several households.

How are home consumers supposed to use their battery effectively? You are charged full price to charge it, and fraction of it to discharge it. Taxed both ways. Meanwhile on utility level you are charged for spot price, which might be negative.
It seems to be there is this brief window in this few years, that home battery makes sense, because once utility scale will catch up it's over. And why wouldn't they, there is money to be made on the market. Battery prices drop, new technologies like Na-Ion batteries are going to cost 1/3rd of current systems. And then there are the open cycle batteries that are more like a fuel cell, that are impossible to do at home, and infinitely scalable otherwise.

I mean if you can make some money in this brief period, good, go for it.
But to set it up as a policy, big advertisement campaigns, and greenwashing? 

[Siwastaja]

I genuinely have no idea why suddenly home energy storage is being viewed as a green alternative, on a global scale, as a solution.
Dave's installation is a prime example, he barely uses a few dozen percent per day, once. It's not efficient usage of batteries.
The same batteries used in a device on utility scale could be sized to charge and discharge several times in a day and serve several households.

I wholeheartedly agree. 99% of home battery installs are probably crippled like this, running small DoD% and small number of cycles per day. In Finland for example they sit 3 months disabled, during which the need for grid load balancing within the day is very real, and you can also get some very real money out of it.

But no, expensive high tech sits unused in most homes.

This is also exactly why our control box gets sold and installed... but it's still niche. We have surprisingly few competitors and most of the batteries are sold without any smart control, just for PV timeshift.

I mean, even with smart controls it is very hard to have batteries make financial sense. So our first simple algorithm reduced the payback time from 100 years to 50 years, and we are hoping the next better algorithm I'm working on gets that in range of 20-30 years. Then if we are able to sell our customers into reserve markets of frequency markets, it might be able to almost make financial sense, but...

As I always say, there are better low-hanging fruits. Like controlling EV charging and electric heating/hot water on/off based on those same market mechanisms one controls battery with. You can't export (sell to grid) but financially sane sell events are pretty rare anyway and make a small, maybe single-digit % of total. Juggling the timing of "self-use of PV" vs. "import" vs. "self-use of imported" is equally possible with aforementioned simple loads (even just relay control), you don't need a 5000-10000 EUR battery to do that.

[Zucca]

https://www.victronenergy.com/live/ess:start

(last feature https://www.victronenergy.com/live/drafts:dynamic_ess)

I installed it in my home since Jan 2024. I could not find any solar company here in US which understood what I wanted, so I hired the first one who did the monkey job to put the solar panel up and bring the wires down.
I wired up the system myself basically.

Battery: 42Kwh, 48V (LiFePO4 cells, bought directly from china)
Inverters power: 16KWh (40KWh peak)
Solar peak power: 14KWh

Inverters take 48VDC and feed the home.
Solar panels goes to MPPTs (only DC to DC) and generate the 48VDC which feed the inverters and the excess power goes to the battery (first Kirkoff law at 48VDC bus bars).

If batteries are full, MPPTs reduce output to match the power needed by the inverters (happens 3 times a month, in average). If batteries are <10%SOC the system switch to grid automagically.
I am a happy camper.

Goals achieved:
- No bent over and sell energy for cheap (50%-60% $ loss each KWh) to (greedy) power companies
- Grid is my emergency generator, 0dBa! and religiously maintained for me for only 12.5$/month (base price my contract)
- More independence from the grid and outside world, 42Kwh UPS for the entire home, best case.
- No extra costs for bidirectional meter installation (both one time at installation and increase monthly base price) [which piss me immensely off, for the power companies the bidirectional meter activation is just a mouse click]
- No more arguing about safely interconnect my system to the grid
- I can put as many solar panels I want, and the power company can't say anything and/or deny the interconnect (for them I still am a strange passive customer, who pulls 0KWh from the grid for long times  )

I use the batteries 10-100 %SoC.

Don't know about the green solution, it could be.
I just did it because it made sense in my head, and ROI is about 10-15years.

I can only suggest Victron systems, they are a joy to work with and very very reliable. Worth every penny.

uinverters? They make sense only in partial shade conditions, otherwise in my planet they are just a quick and dirty solution to generate solar powers.

PS: I will never trust a power electronic device which is cooking at high temp on the roof everyday. No matter how good the design is, it is just simply not the smartest idea IMHO.

[tszaboo]

Goals achieved:
- No bent over and sell energy for cheap to (greedy) power companies
- Grid is my emergency generator, 0dBa and religiously maintained for me for only 12.5$/month (base price my contract)
- More independence from the grid and outside world, 42Kwh UPS for the entire home, best case.
- No extra costs for bidirectional meter installation (both one time at installation and increase monthly base price) [which piss me immensely off, for the power companies the bidirectional meter activation is just a mouse click]
- No more arguing about safely interconnect my system to the grid
- I can put at many solar panels I want, and the power company can't say anything and/or deny the interconnect (for them I still am a strange passive customer, who pulls 0KWh from the grid for long times  )

The situation is very different in different parts of the world.
- I  pay 3x the connection cost as you, 26 EUR/month.
- We had 3 power outage that were longer than 1 minute since my meter was installed, which is IDK 10 years now? 2 was scheduled in advance. 99.9999% reliability easily.
- Bidirectional meter installed by default.
- My solar system was accepted after I paid 50 EUR for the installer to take care of the paperwork, cause laziness. I could have done it for free probably.

And here is the bottom line: Why do you have to install a home battery? Because grid is unreliable and bureaucracy is bad.
Both of which should be solved with pitchforks and torches, not with a battery.

[Zucca]

And here is the bottom line: Why do you have to install a home battery? Because grid is unreliable and bureaucracy is bad.

and third because my power companies interconnect rules/conditions were a joke and basically my solar panels would have made just more profit for them....
The above make my blood pressure peaks high every time I think about it. Some power companies are using the solar panels horse just to increase profit, and milking the cows customers even more. Every day.

EDIT: Ah I forgot to mention that in a regular solar system, if the grid goes off the solar panels needs to be turned off as well for safety. 
No thanks, I wanna use the energy the sun is giving me. Especially when the grid goes bananas.

[Electrodynamic]

tszaboo

I genuinely have no idea why suddenly home energy storage is being viewed as a green alternative, on a global scale, as a solution.
Dave's installation is a prime example, he barely uses a few dozen percent per day, once. It's not efficient usage of batteries.
The same batteries used in a device on utility scale could be sized to charge and discharge several times in a day and serve several households.

The smart grid solves this problem and there are already companies that provide grid management solutions. In effect, one company manages tens of thousands of individual producers like Dave's installation over the internet. All the installations combined could produce hundreds of MW of power or more in minutes and is considered a utility scale producer the same as any other. The only difference is that this smart utility system is decentralized.

In fact, I heard some people were making $200 a day using there EV and house battery to store power off peak and export it during peak hours. For example, yesterday I saw the pool price for power here change from $0.5/MW to $125/MW during the day. In some extreme cases the pool prices changed by $1000/MW in a matter of hours. So the grid is anything but stable and there is lots of money to be made using battery storage.

[nctnico]

tszaboo

I genuinely have no idea why suddenly home energy storage is being viewed as a green alternative, on a global scale, as a solution.
Dave's installation is a prime example, he barely uses a few dozen percent per day, once. It's not efficient usage of batteries.
The same batteries used in a device on utility scale could be sized to charge and discharge several times in a day and serve several households.

The smart grid solves this problem and there are already companies that provide grid management solutions. In effect, one company manages tens of thousands of individual producers like Dave's installation over the internet. All the installations combined could produce hundreds of MW of power or more in minutes and is considered a utility scale producer the same as any other. The only difference is that this smart utility system is decentralized.

In fact, I heard some people were making $200 a day using there EV and house battery to store power off peak and export it during peak hours. For example, yesterday I saw the pool price for power here change from $0.5/MW to $125/MW during the day. In some extreme cases the pool prices changed by $1000/MW in a matter of hours. So the grid is anything but stable and there is lots of money to be made using battery storage.

This may be the case right now but if there is a profit to be made, this will attract big investors going for large scale solutions. In the end a decentralized solution will be more expensive and thus it will be killed by large scale competition doing storage or hydrogen conversion. IOW: the situation where prices fluctuate a lot won't last forever. 5 to 10 years at most. Also consider net congestion. Last week there was an article in the news saying that grid operators don't like home batteries to charge when prices are low and discharge when prices are high because this results in extra strain on the grid at times where the grid is already under maximum load. So even if you could control charging / discharging home batteries centrally, this likely won't be price driven but used to lower the load on the grid. Maybe this could result in some paypack but likely not enough to make a battery worthwhile. Also keep in mind that a central control system needs to be maintained and operated. Likely the company doing the central control is the only one making money. 'Mine the miners'; the only people getting rich from mining are the ones selling the mining equipment.

[darkspr1te]

Power, that has become a tradable commodity in the streets now , Where i live in Zambia, Lusaka(capitol) we 'might' get 3 hrs pf power per 3 days now, sometimes a afternoon, we charge power banks for each other and hand them around like handshakes almost.

Right now de-centralized power systems is keeping this country going in some ways. You see people carrying 'solar generator power packs' to work where they hope they can tap into company power somehow for taking home to try and keep food cold. Peltier fridges and micro fridges(bldc compressor type) have popped  all over the place.

We recently(the school I own)  went fully solar at great cost (small system 5kw/5kva/5kv but central africa is costly shipping) and our excess is dumped into power banks and SG that our staff bring. We had many experimental small system in the past and donated them to the staff as we upgraded, The full solar i mention is going from simple 12v to full victron+victron mppt/freedom won bat/home assistant log+control done by a pro. We use wifi switches to control pumps/sockets/water heaters so the system wont allow run away's like a tap left open or your next door neighbor tapping into your bore hole pump power.

In our case we have such a power deficit that companies that invest in solar for own use and excess to the grid only help us, as a country we did not considered growth of finance and how it affected power usage (more tv's, more massive adverts signs 24/7 , more bribed politicians owning large empty houses with full security lights :-P )  , the wise early on adopted solar early and while it's a lot cheaper now many were able to sell/pass on usable equipment when they upgraded.
While this wont sort out the bad management of our countries power it will to some value relief to the suffering on the local population, 

Foot note, i cannot full blame the power managers as we do have a 7 year cycle on our rains and it shift up and down a bit and we are currently in that poor rain period so dams are dry dry dry.

darkspr1te

[Siwastaja]

The smart grid solves this problem and there are already companies that provide grid management solutions. In effect, one company manages tens of thousands of individual producers like Dave's installation over the internet. All the installations combined could produce hundreds of MW of power or more in minutes and is considered a utility scale producer the same as any other.

I mean, a week ago we commanded 100 of our customers to export to grid during high energy price situation and supplied 500kW to the grid. It's already something. With current sales rates we are having several MW to control within a month or two. This is already something that can be used to enter the grid stabilization market place(s). Or, just enable customers to get money from spot price markets, like we did a week ago. Or, combine both: sometimes the aims are contradictory but often synergetic. It's just an optimization problem.

In the end a decentralized solution will be more expensive and thus it will be killed by large scale competition

You are of course right about being more expensive (per kW and kWh). But remember though that unless we talk about North Korea or something, the world is not a centrally planned engineered-to-be-optimum solution. Nothing is "killed". At the time, both cost-effective large installations and very cost ineffective distributed batteries are installed. Because people are easy to talk into buying this kind of battery. Many households have loose money at their disposal, or want to do something. It's not about finding most cost-effective solution, but people buying what they want.

Many people buy expensive wrist watches that cost thousands or tens of thousands and offer absolutely no technical benefit over a $100 watch for the purpose of timekeeping. Not to even talk about jewelry. And even poor people buy this kind of crap using loan money.

Home batteries are not optimal*, but they are reality. Apparently they are super easy to sell to people. Go figure. A year ago I would have not imagined I would be working in home battery optimization, but here we are.

*) especially when underutilized without smart controls

[Marco]

Last week there was an article in the news saying that grid operators don't like home batteries to charge when prices are low and discharge when prices are high because this results in extra strain on the grid at times where the grid is already under maximum load.

If dynamic prices were sufficiently local that would be impossible. If reverse currents on the high voltage grids would cause problems, the dynamic local feed in price could go as close to 0 as needed to reduce the feed in ... in the extreme it could make the load on the high voltage grid zero, how does making it zero add to the load?

Even now, what they probably mean is "we want to make all that profit, or at least hand it to friends".

[Siwastaja]

Last week there was an article in the news saying that grid operators don't like home batteries to charge when prices are low and discharge when prices are high because this results in extra strain on the grid at times where the grid is already under maximum load.

This is a ridiculous generalization: obviously it's the polar opposite: prices are high because there is lot of use and lack of production. These batteries act as production. When loads and production are distributed and coincide at the same time, it reduces the peak currents on the grid, on all levels.

It seems you don't simply understand how production 180degrees out of phase from consumption cancels out the currents. This is how everything already works in grid.

Literally this is what grid operators want and they pay to companies like us to do this.

As usual, your argument concentrates on some possibly real but pretty specific edge case and generalizes it. Such edge case could be, for example, everyone in one neighborhood, where houses are heated using gas etc. so consumption is low and local distribution network weak, getting into the train of home batteries all at once; basically trying to "manage" the whole grid through that last mile of distribution. Then again, all that happens is local voltage rises and these inverters stop exporting, so it hurts primarily those who jumped into the train.

[Siwastaja]

If reverse currents on the high voltage grids would cause problems

There is no concept of reverse currents on AC grid. When you add production somewhere, the AC current is just 180 degrees out of phase from consumption, cancelling out and reducing current towards zero. If somewhere production exceeds consumption then the current starts to rise again. You would need to have zero consumption and as much production as worst case consumption ever is, to exceed normal design currents. Current is not a problem.

Last mile voltage however might be: because sometimes parts of grid have more than desirable resistance, causing voltages to drop below minimum acceptable during max consumption situation, grid companies compensate by switching to higher transformer taps, so that no-load voltage exceeds nominal voltage. Without production, no-load voltage is maximum too, so as long as it doesn't exceed the maximum it's all fine. But this creates asymmetry between maximum consumption vs. maximum production, which must be managed by either improving the local distribution network, or denying excessively large PV and/or battery installations.

[nctnico]

Last week there was an article in the news saying that grid operators don't like home batteries to charge when prices are low and discharge when prices are high because this results in extra strain on the grid at times where the grid is already under maximum load.

This is a ridiculous generalization: obviously it's the polar opposite: prices are high because there is lot of use and lack of production. These batteries act as production. When loads and production are distributed and coincide at the same time, it reduces the peak currents on the grid, on all levels.

Sorry, but this is what the article says and it comes straight from the horse's mouth (a grid operator) so don't shoot the messenger. What you don't seem to realise  well enough is that electricity needs to be transported from point A to point B. If you have production at point A and storage at point B, then there needs to be enough transport capacity between both points in order for storage to be actually usefull. Unfortunately, the transport capacity is lacking in some places. You need to see this as a 3 dimensional problem. Production, consumption / storage AND transport capacity.

[Marco]

There is no concept of reverse currents on AC grid. When you add production somewhere, the AC current is just 180 degrees out of phase from consumption, cancelling out and reducing current towards zero. If somewhere production exceeds consumption then the current starts to rise again. You would need to have zero consumption and as much production as worst case consumption ever is, to exceed normal design currents. Current is not a problem.

Over here the majority of consumption is in a small heavily industrialized western part of the country, the Randstad. This also has most traditional generation and distribution. The population however is much more evenly distributed and with it PV. So now PV power is trying to make its way to the consumption in the Randstad on a grid never really designed for that kind of flow.

[Siwastaja]

Sorry, but this is what the article says and it comes straight from the horse's mouth (a grid operator) so don't shoot the messenger.

I know the drill, it's nctnico nctnicoing again: some yellow mainstream media article about about a technical issue first misinterpreted by the popularizing journalist possibly with political agenda then further misinterpreted by nctnico with more political agenda.

You are not a messenger, you are making claims. You might be treated as a messenger if you gave a reference to the article you are talking about so that we professionals working on this field could check what it actually says, instead of how you (possibly mis-)interpreted it.

What you don't seem to realise  well enough is that electricity needs to be transported from point A to point B. If you have production at point A and storage at point B, then there needs to be enough transport capacity between both points in order for storage to be actually usefull. Unfortunately, the transport capacity is lacking in some places. You need to see this as a 3 dimensional problem. Production, consumption / storage AND transport capacity.

Unless there is a massively serious mismatch between production and consumption, production and consumption cancel each other out, making it easier for given transport capacity to handle. But sure, as I said, there are going to be edge cases. Your claims are not valid generalizations. You are not describing a problem, you are describing a solution. Batteries are to grid what medicine is to illness: a cure, a solution; but in some edge cases the cure itself is worse than the illness, and this is perfectly normal. Yet the generalization that medicines are bad or grid companies do not like batteries are definitely incorrect, and I can say it with very good confidence even without reading your mystery source.

[Siwastaja]

There is no concept of reverse currents on AC grid. When you add production somewhere, the AC current is just 180 degrees out of phase from consumption, cancelling out and reducing current towards zero. If somewhere production exceeds consumption then the current starts to rise again. You would need to have zero consumption and as much production as worst case consumption ever is, to exceed normal design currents. Current is not a problem.

Over here the majority of consumption is in a small heavily industrialized western part of the country, the Randstad. This also has most traditional generation and distribution. The population however is much more evenly distributed and with it PV. So now PV power is trying to make its way to the consumption in the Randstad on a grid never really designed for that kind of flow.

Yeah, thanks for clearing this up; my point was that the issue is not as much the direction of the power flow, but the magnitude of it. Let me guess that the population outside of the heavily industrialized western part mostly heats their home and hot water (maybe even cook?) using natural gas, and still drive mostly fossil fuel vehicles, and air conditioning still being considered a luxury item of a kind. Therefore, pretty low consumption. If this is the case and the grid is designed for this, it is not a good idea to install overly large PV systems or use batteries to either charge or discharge from/to grid at full power.