One family's solar story

[D_W]

For me it seems the point of going solar with a battery is to not have to buy electricity from the grid at all if possible.
It seems silly to generate electricity, sell it to the grid at a poor rate, only to have to buy it back again at a much higher rate.
The government's incentives for buy back rates have stopped now, my brother still gets a good rate as he signed up before it changed.
Of course in winter you will have to buy some with short days etc.

Ollie

Things must work differently there. They generally won't allow you to install and connect an array that's larger than your proven use here. Things may have changed due to EVs and maybe they allow an adjustment, but I'm not sure. Their objective is to make sure that you're not supplying power back to the grid as a generator.

So, what happens with the net metering is if you use a certain amount of Kwhr for a month, it doesn't matter when you use it. If you can do the whole thing perfectly, let's say, your bill is zero or maybe ever so slightly negative. If you're using 8kwhr for an oven and giant air conditioner, but it averages out to 2kwhr during the day and your panels generate the same amount, the meter just reports the net. So you're freeriding generated power off of the grid (the same as you would draw from a battery) when you need to and pushing power onto the grid when you don't need it.

You more or less get to use power like you have a battery but without the battery. The fractional generation reimbursement is, I suppose, to prevent someone from drastically changing consumption and getting paid the same as a preferable generator. As in, a gas generation station is someone you'd rather pay 7 cents an hour to vs. someone's rooftop, but the net metering rules cause the utility to pay the same for power from both, and even further than that, require the grid that has supplied some power and taken some from the panels to suddenly remove the grid charge, too.

That part doesn't make as much sense and it's changing (and should).

Before batteries, I remember standalone systems having coil shunts and such things. It'd be dandy if those shunts heated water and then heated a fluid mass somewhere for fall and winter heat, but I'm sure that's not a feasible thing.

 

[Sideways]

The sand battery that has gone live in Finland recently stores renewable energy as heat ( 600C) for months, to feed back into an underground district heating system in the winter. Simple and inspiring.
It would be awesome to see a rural domestic version of that. A 10x10x10 foot cube of sand would take all my excess summer energy to give back as heat in winter. Intense sources energy are more useful than dilute ones. That's why solar PV is more versatile than solar thermal, and the sand battery has advantages over hot water buffer tanks provided it's own challenges can be solved.

 

[Sideways]

@Sideways , you say "First is to use an AC coupled battery which simply wires in to any new or existing system using 240V AC."
I don't understand that idea, explain please?

Excellent and thorough view, much appreciated.

Dave, I'll come back to this when I figure out a better way to explain it clearly. I won't forget but bear with me a day or three.
I'll try and complete my "place holder" posts as quickly as possible because I have learnt that once a post is made, you only have 24hrs to go back and edit it.
After that, Mike K will be helping me to bully this into a useful and hopefully readable thread
Cheers Mike !

 

[Lorenzl]

I suppose the other thing is the grid doesn't not need your surplus during the day. They would prefer it at night hence the buy in tariff is low?

 

[Inspector]

Mike perhaps one of the Phase Change Materials could be used to store heat for later use.

https://www.ctc-n.org/technologies/phase-change-materials-thermal-energy-storage
https://www.1-act.com/products/pcm-heat-sinks/pcmselection/
Pete

 

[Lorenzl]

@Sideways there is one on the way Caldera but only for re heating water.

I am thinking about installing a Sunamp phase change battery.

 

[Sideways]

I like the Sunamp phase change concept. Especially their research into why these materials typically fail after a small number of cycles and their proprietary modifications to a well established material that is claimed to extend its life to over 30 years.
Right now though, they are using this to solve the wrong problem. The largest domestic battery is equivalent to a 300 litre water tank, at greater cost, but in less space. It is about freeing space in small homes.

If they made a unit as big as a 300L water tank that held equivalent of 600 L of energy, I'd be interested.
Also, the Sunamp gives it's energy back at 55C. A hot water tank can store it's whole contents at 70 odd and be diluted when used. That increases the effective volume of hot water that you can store in a simple tank.

Sadly, none of these devices are able to store enough water, hot enough, to maintain central heating overnight.

 

[Robbo3]

Very good write up.

 

[Denty]

MyEnergi smart controls

There is little argument that the way to get maximum value from solar PV is to maximise self consumption.
Key to this are
1. A solar diverter that measures surplus energy that you are trying to send back to the grid and instead sends exactly the surplus amount of power into an immersion heater or some other electric heater like electric radiators.
2. A smart electric vehicle charger that does the same for charging an electric car. It has the option to send only the surplus generation to charge the car battery.

There are plenty of EV chargers but few that are smart enough to only use surplus energy whenthat is what you want to do.
There are a few options for solar diverters.

The best system on the market at present is offered by a UK company called myenergi.
They have a long technical history in the game and offer both of the above, plus an app to visualise and control both.

We aspire to an EV so the solar was designed with a car in mind. Within days of installing the panels, we realised how much surplus we had and I went online and bought a Myenergi Eddi solar diverter immediately.

Eddi works great. It cost £300+ but it is well built and pumps several kWh a day into our immersion heater. Once the tank is hot and the immersion thermostat opens the circuit, Eddi realises this and sends any more surplus to a second circuit, which could be an electric rad or a second immersion heater.
This is actually smart. A big tank with immersions top and bottom can be set to heat water at the top of the tank first for a shower then preheat the bulk of the tank through the day.
While heating the second load, Eddi switches back to the primary load every 15 minutes in case it will take more.

Here is Eddi heating our immersion on priority 1. Note the periodic spikes happen when it checks back and manages to push a little more heat into the tank.
View attachment 142515
Also notice the dotted temperature line.
Eddi has an optional sensor circuit board. An end user installable thing. This allows you to control some extra circuits and to connect one or two standard temperature sensors. The dotted line shows the actual temp of our water measured by the sensor. You can allow that to control the heating.

Below is happens when we use hot water in the morning and and Eddi has time and surplus available to reheat the tank. On occasions we have heated and used three tank fulls of water in a day. It takes about 12kWh. In our old hot tank we are limited because the immersion only reaches halfway down into the tank, but at 70C this is enough for a good tub.

View attachment 142518
The system has upto three current sensors that can be hooked up to the meter tails to see what is coming in and out of the grid, and in my case to measure the generation from each of two inverters. The myenergi app shows all the energy flows in one place and is our goto in deciding whether we canrun our kettle, oven, microwave, tumbler, etc for "free"

Here's the app showing the multiple devices. When we add a Zappi 2 car charger, there will be one more petal.
View attachment 142520

And some screens showing history and consumption in different ways
First shows 15kWh of generation. We used only 1.2kW of that and exported the rest.
We had to buy 5kWh from the grid because we don't have our batteries yet.
But the app doesn't count the energy diverted to hot water so we need to add about 8kWh to the 15 in the first screen, we actually generated about 24kWh and used nearly 10kWh of it.

View attachment 142519

View attachment 142517

This screen shows generation by the smaller our two inverters.
Notice how it starts at 7am. The small inverter is fed from the lowest our panels, the bottom our roof gets sun about 30 minutes after the top first gets it. So Eddi starts heating the water at 6.30 thanks to the larger inverter and the little un kicks in a bit later.

For both inverters the best power is made in the morning and early afternoon thanks to the SE facing direction of the roof. Whenbthe time comes, we'll be able to charge the carbin the morning and go out in the afternoon

View attachment 142522View attachment 142521

Very informative and might I say timEly, thank you

 

[MikeJhn]

A123 in the USA where the originators of the LiFe (lithium nano phosphate) battery about thirty-five years ago, then shortly afterwards came the Chinese copy PO4 and as far as I now they are both Lithium Iron batteries, is it me or others that are confused, if someone could explain the chemical difference that would help my old brain get less cloudy.

 

[Jacob]

Phew a lot of information above!
Battery seems to be the weakest link in so many of the alternative energy schemes, except as back up, which is how they've always been e.g. to start an ICE and keep it going but not to run one (very far).
Maybe low tech energy storage is the way? Hot water tanks? Pumped water for hydroelectric generation?
Or to to link all solar panel installations to a bigger grid (national?) and completely separate generation from distribution?
Ditto EVs - having lower tech replaceable batteries available at charging stations rather than aiming for long journey self sufficiency - or simpler still, have direct electric pick-up as per rail, tram etc?

 

[Jacob]

.....

Sadly, none of these devices are able to store enough water, hot enough, to maintain central heating overnight.

But luckily hardly anyone needs central heating overnight. Those that really do need it become another design problem, possibly involving underwear (remember the dressing gown?), or small and well insulated rooms?

Thinking out of the box required - two particular boxes may need a lot of rethinking; personal habitation and personal transport.

Just reading Adventures in the Anthropocene by Gaia Vince – review
Essential reading, with lots of accounts from around the globe of people who are already dealing with the effects of climate change, but largely in temperate/hot (too hot) regions. EVs don't get a mention!

 

[NormanB]

We live in Cheshire, UK
I have been very happy with my installer. For now let's protect their reputation in public from any of my misdeeds PM me if you are in this part of the world and still want to know.
I think "in roof" is great. It looks smart and would be the way to go with a new build or a reroof. Two caveats though. First is that mounting solar panels flush with the roof means little or no ventilation behind them. Solar panels get hot and generation is reduced when they are hot. So in roof is electrically less efficient because the panels run hotter. I haven't quantified this. Second is that some in roof systems use or require specific panels. The in roof systems on show at the trade show I mentioned all used panels that were just a mid range PERC technology. My preference for the high spec N type panels wasn't negotiable.
Victron equipment looks excellent to me. They have a very good reputation for off grid solutions and the equipment appears well made. I'd recommend anyone interested to consider them.

Thank you. Sadly am not in your area.
Yes I was aware of the performance hit with in roof, just for me - aesthetics outweigh that.
My research continues (but I am favouring Victron as they seem to have the system integration sewn up).

 

[Sideways]

A couple of new housing estates that I have seen develop over the last 5 years both include a dozen or more houses built with in-roof panels. They look very tidy.

Our home is 40 years old and roofed with Marley cement tiles. I queried Marley about the expected life of their tiles and heard that 60 years even 70 year life is not uncommon. It felt just a step too far to add in a roof replacement to our project.

If I had the ££, I would have been tempted.

 

[Dabop]

The BYD BBox is quite popular here in Australia, a modular storage system that can be easily expanded later if you find you need more storage, and considerably cheaper than the Powerwall from Tesla (plus as the BBox uses LiFePO4 cells, it basically lasts about twice as long as the Powerwall with its lithium-ion cells

BYD is a HUGE player in China, their production levels are equal to Teslas 'gigafactories', and they have been available for about the same time (but only recently have they started looking at external markets- all their production was sold inside China- mostly to their automotive arm...)

BYD made the 'ElectricBlu' city buses, first trial in Australia was in 2016 for a 400km electric bus with first large order in 2017, now they are looking at replacing almost all the diesel buses with them in Sydney

They have been selling a fully electric BEV, the E6, since 2009, widely used in China as taxis (I got a ride in one here in Sydney, and they are a very zippy little beast)

They are well in advance of Tesla in one aspect, you can't buy a Tesla truck or semi trailer- walk in, plonk down the cash and drive out in a BYD electric truck....

They don't make 'supercars' like the Teslas- they are more the 'Toyota Corolla' of the BEV market- but they do have a long history in it- as long as Tesla has been doing it...

 

[sumo2001]

Very interesting read

 

[Jaydee]

Yes a very interesting read. Thank you for spending the time writing it up.

 

[NormanB]

A couple of new housing estates that I have seen develop over the last 5 years both include a dozen or more houses built with in-roof panels. They look very tidy.

Our home is 40 years old and roofed with Marley cement tiles. I queried Marley about the expected life of their tiles and heard that 60 years even 70 year life is not uncommon. It felt just a step too far to add in a roof replacement to our project.

If I had the ££, I would have been tempted.

As I understand it the in roof is fitted in/on a plastic tray which has suitable profiles to accommodate the profile of common roofing tiles. So no need to replace the roof, just the requisite number of tiles - rather like fitting a Velux window.

 

[NormanB]

MyEnergi smart controls

There is little argument that the way to get maximum value from solar PV is to maximise self consumption.
Key to this are
1. A solar diverter that measures surplus energy that you are trying to send back to the grid and instead sends exactly the surplus amount of power into an immersion heater or some other electric heater like electric radiators.
2. A smart electric vehicle charger that does the same for charging an electric car. It has the option to send only the surplus generation to charge the car battery.

There are plenty of EV chargers but few that are smart enough to only use surplus energy whenthat is what you want to do.
There are a few options for solar diverters.

The best system on the market at present is offered by a UK company called myenergi.
They have a long technical history in the game and offer both of the above, plus an app to visualise and control both.

We aspire to an EV so the solar was designed with a car in mind. Within days of installing the panels, we realised how much surplus we had and I went online and bought a Myenergi Eddi solar diverter immediately.

Eddi works great. It cost £300+ but it is well built and pumps several kWh a day into our immersion heater. Once the tank is hot and the immersion thermostat opens the circuit, Eddi realises this and sends any more surplus to a second circuit, which could be an electric rad or a second immersion heater.
This is actually smart. A big tank with immersions top and bottom can be set to heat water at the top of the tank first for a shower then preheat the bulk of the tank through the day.
While heating the second load, Eddi switches back to the primary load every 15 minutes in case it will take more.

Here is Eddi heating our immersion on priority 1. Note the periodic spikes happen when it checks back and manages to push a little more heat into the tank.
View attachment 142515
Also notice the dotted temperature line.
Eddi has an optional sensor circuit board. An end user installable thing. This allows you to control some extra circuits and to connect one or two standard temperature sensors. The dotted line shows the actual temp of our water measured by the sensor. You can allow that to control the heating.

Below is happens when we use hot water in the morning and and Eddi has time and surplus available to reheat the tank. On occasions we have heated and used three tank fulls of water in a day. It takes about 12kWh. In our old hot tank we are limited because the immersion only reaches halfway down into the tank, but at 70C this is enough for a good tub.

View attachment 142518
The system has upto three current sensors that can be hooked up to the meter tails to see what is coming in and out of the grid, and in my case to measure the generation from each of two inverters. The myenergi app shows all the energy flows in one place and is our goto in deciding whether we canrun our kettle, oven, microwave, tumbler, etc for "free"

Here's the app showing the multiple devices. When we add a Zappi 2 car charger, there will be one more petal.
View attachment 142520

And some screens showing history and consumption in different ways
First shows 15kWh of generation. We used only 1.2kW of that and exported the rest.
We had to buy 5kWh from the grid because we don't have our batteries yet.
But the app doesn't count the energy diverted to hot water so we need to add about 8kWh to the 15 in the first screen, we actually generated about 24kWh and used nearly 10kWh of it.

View attachment 142519

View attachment 142517

This screen shows generation by the smaller our two inverters.
Notice how it starts at 7am. The small inverter is fed from the lowest our panels, the bottom our roof gets sun about 30 minutes after the top first gets it. So Eddi starts heating the water at 6.30 thanks to the larger inverter and the little un kicks in a bit later.

For both inverters the best power is made in the morning and early afternoon thanks to the SE facing direction of the roof. Whenbthe time comes, we'll be able to charge the carbin the morning and go out in the afternoon

View attachment 142522View attachment 142521

Thank you for this and it is always interesting to see detail.

Just one think have you considered the arbitrage potential using a battery and the Octopus Agile tariff?

Here is a screenshot of my sons installation:

Note the price difference between export and import. The arbitrage can be between 20p per KWH and 45p per KWH

Clearly he is charging his battery from solar or by importing it and exporting to maximise arbitrage. He is still refining his controls and timing for best effect but is already yielding impressive results.

Not sure how long this ‘situation’ will continue.

 

[Dibs-h]

Thank you for this and it is always interesting to see detail.

Just one think have you considered the arbitrage potential using a battery and the Octopus Agile tariff?

Here is a screenshot of my sons installation:
View attachment 142640
Note the price difference between export and import. The arbitrage can be between 20p per KWH and 45p per KWH

Clearly he is charging his battery from solar or by importing it and exporting to maximise arbitrage. He is still refining his controls and timing for best effect but is already yielding impressive results.

Not sure how long this ‘situation’ will continue.

I know of a chap that fitted a 100kWh battery, charges it between 00:00 & 05:00 on Octopus's economy 7 tariff, at 5am the house disconnects from the mains and powers his house till 00:00. Then rinse and repeat. His usage is around 11kWh\day but from what I've read, by not deep discharging the battery much, the lifespan is longer.

Found it very interesting especially as phase 2 for him is the addition of PV panels.