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Solar PV Hints, Tips & Troubleshooting

DrPhilG

Well I've reached the point of driving everyone nuts on the PV quotes thread, and since I now have my system installed and running my endless questions no longer belong there.

So I figured I'd ask here, and also provide a home for others in the same boat, with general questions and advice on managing post-install.

My first question (of many) is how do people best manage their production in order to reduce grid export? Despite being overcast and miserable a fair bit of the day, I've produced 24kWh so far today, but ended up exporting 11.

Not too bad when we're home, as the wife did a few loads of washing and drying, put on the dishwasher etc.

But we're both at work tomorrow so other than a timed or remotely activated washer/dryer run we would end up exporting a lot more.

Extra battery capacity or a water diverter would help, but they don't tend to justify their costs in the long term.

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BryanF

MAULBROOK wrote: »

I have been thinking about charging the battery at night on the cheep rate to have it full for use during the day.
Was only planning to do this during the bad winter months.
I have a Solis 5kw wit a 7 kw BYD battery.
My thinking is have it full for the morning and if its a good day the the water will heat via the Iboost.

Any thoughts would be welcome, good or bad.

Cheers

hi one post is enough thanks https://www.boards.ie/vbulletin/showthread.php?p=114966790

unkel

Sir Liamalot wrote: »

Tesla poowerwalls have 300W internal heaters that maintain a 20°C operating temperature and they'll only mount them outside.

Well, not in living areas. So yeah, if you don't have a garage or any other non-living area or outbuilding, then that means outside.

I reckon the reason for this is that Tesla doesn't use the much safer LiFePo4 chemistry in their power wall cells. Most other home attached storage manufacturers do and they have no problems installing indoors

garo

MAULBROOK wrote: »

I have been thinking about charging the battery at night on the cheep rate to have it full for use during the day.
Was only planning to do this during the bad winter months.
I have a Solis 5kw wit a 7 kw BYD battery.
My thinking is have it full for the morning and if its a good day the the water will heat via the Iboost.

Any thoughts would be welcome, good or bad.

Cheers

I would do the maths first. How do you heat your water normally? If it's using an oil or gas boiler you are paying 5c max per kWh after accounting for losses assuming you are on a decent plan. So using the iBoost saves you 5c per unit.

Putting energy into a battery using night rate and drawing it back out has a number of costs. It is reasonable to assume you will have ~80% round trip efficiency. Recall your inverter is converting AC to DC which is going into the battery and being stored via a chemical reaction. Then the reverse reaction takes place and your iverter converts DC back to AC. Sir Liam's experiments showed a near 80% efficiency rate so we will go with that. So your 8c night rate leccy is already 10c.
Then by charging and discharging you are using up finite battery life. I did some calculations on the Pylontech last year that found a range of 5-10c per kWh put into the battery and taken out of it depending on how much you paid for it and how many cycles you actually get out of it.

If you store night rate electricity in the battery only to have your solar heat the water you may find it ends up costing more in the long run. A compromise might be to charge to 50-60% so you are sure you don't have any excess to heat the water. But even then do your maths.

[Deleted User]

unkel wrote: »

I reckon the reason for this is that Tesla doesn't use the much safer LiFePo4

They adopted 18650 for pricepoint, energy density, ubiquity and subtle safe isolation.
Easier cool 10 000 teeny cells than big chunkers (surface area) and when they start failing nobody notices.
The new "6 times more energy" cells they're using are coincidentally 6 times larger.

They put them in houses because that's what they had and people were willing to pay for them.

Impossible to recycle. (not viable)

worlds goodest teecher

graememk wrote: »

Usually
Higher standing charge & slightly higher day rate.

Do you know your annual usage currently?

I think the tipping point for a day night meter is 30% of your units to be night.

So putting some loads to run overnight can tip the balance in your favour, ie Dishwasher.

No, no idea of our consumption. Different property, different circumstances from twelve months ago. Myself and my wife both working from home now. PV will hopefully cover most of our daytime consumption on a good day. Stagger washes, etc.

Evening consumption consists of dinner, one evening shower, maybe dishwasher, TV, lighting and pellet stove.

graememk

worlds goodest teecher wrote: »

No, no idea of our consumption. Different property, different circumstances from twelve months ago. Myself and my wife both working from home now. PV will hopefully cover most of our daytime consumption on a good day. Stagger washes, etc.

Evening consumption consists of dinner, one evening shower, maybe dishwasher, TV, lighting and pellet stove.

Ive starting doing quite heavy monitoring of my power use, But something that surpised me, is that our washing machine doesnt use a lot of power,

and the dishwasher with its 3 spikes. its on its Auto setting of about 2.45 hrs.

The square wave in the graph has to be the fridge clicking on and off.

Graphs just to give an indication of the profiles of dishwasher and washing machine, Should be able to grab a wash/dry cycle tonight. ( we have a combined washer dryer)

worlds goodest teecher

We bought the house early this year, gutted it. All min A rated appliance, installed cavity and attic insulation, replaced inefficient oil boiler with new one, triple glazed front and back door, just approved for solar PV grant. Flexible with when we do washes. The payback on 14 panels with battery was long and out of our budget. Going with 8 panels 2.5kW system, no battery. If night saver would complement this system and help reduce cost I would be interested in exploring it further.

daughy

graememk wrote: »

Ive starting doing quite heavy monitoring of my power use, But something that surpised me, is that our washing machine doesnt use a lot of power,

and the dishwasher with its 3 spikes. its on its Auto setting of about 2.45 hrs.

The square wave in the graph has to be the fridge clicking on and off.

Graphs just to give an indication of the profiles of dishwasher and washing machine, Should be able to grab a wash/dry cycle tonight. ( we have a combined washer dryer)

Your right about the washing machine, it'll use a lot when spinning, I can't really remember exactly but I used a kw meter on a washing machine about 4 years ago and if I can remember it was 100 Watts continously for the cycle, and approx 1kw for the spin, your fridge is the bad boy consumer, approx 1kw for 24 hours, 365 days a year, the dryer eats electricity, mine uses 2.5kw an hour, I'm not sure about a dishwasher. Would be interesting to see your results.

graememk

daughy wrote: »

Your right about the washing machine, it'll use a lot when spinning, I can't really remember exactly but I used a kw meter on a washing machine about 4 years ago and if I can remember it was 100 Watts continously for the cycle, and approx 1kw for the spin, your fridge is the bad boy consumer, approx 1kw for 24 hours, 365 days a year, the dryer eats electricity, mine uses 2.5kw an hour, I'm not sure about a dishwasher. Would be interesting to see your results.

Fridge/freezer is fine 1kwh a day? and 9hrs of it is on night rate, If i want to save power id turn some of my pcs/servers off!

[Deleted User]

Yurp the washing machine surprised me too. We always blame the noisey ones...like the fruit dehydrator.

Fridges usually have stifled cooling. The ones in live-aboards are top loading, active condenser cooling, externally insulated and often atmospherically vented.

[Deleted User]

worlds goodest teecher wrote: »

We bought the house early this year, gutted it. All min A rated appliance, installed cavity and attic insulation, replaced inefficient oil boiler with new one, triple glazed front and back door, just approved for solar PV grant. Flexible with when we do washes. The payback on 14 panels with battery was long and out of our budget. Going with 8 panels 2.5kW system, no battery. If night saver would complement this system and help reduce cost I would be interested in exploring it further.

Interesting you have night saver. I'm going with it (requested install on Thursday) and plan on using it for washing machine, drier, dishwasher and a food dehydrator.
I'm starting to figure that and the solar as a service might work with 6 panels. A 2 2kw system no battery

Prowetod

graememk wrote: »

Ive starting doing quite heavy monitoring of my power use, But something that surpised me, is that our washing machine doesnt use a lot of power,

and the dishwasher with its 3 spikes. its on its Auto setting of about 2.45 hrs.

The square wave in the graph has to be the fridge clicking on and off.

Graphs just to give an indication of the profiles of dishwasher and washing machine, Should be able to grab a wash/dry cycle tonight. ( we have a combined washer dryer)

What system are you using to monitor your usage?

graememk

Prowetod wrote: »

What system are you using to monitor your usage?

emonpi/emoncms from openenergymonitor

actually using an emontx for the energy monitoring hardware as i was already running the emoncms for other projects on a pi

Monitoring my house, and my parents house with them, (all connected to the same network)

Its got an AC/AC adapter so it can measure the voltage to give a more accurate reading from the CT's

championc

My washing machine consumes nothing even remotely near 1kw while spinning. I have watched the figures from my MyEnergi app.

However, there is no getting away from the power which is needed to heat the large quantity of water used by every wash. That too is why dishwashers are such large consumers.

Water heating will always be the guzzler of power

DrPhilG

Our tumble dryer packed it's bags just before our solar install (it's been in the brink for a while).

We replaced it with a heat pump model. The old one used to run on average at about 2kWh during the cycle and because it was knackered it would take a good 90-120 minutes at least to dry a load.

The new one seems to peak at about 600w and dries a load in under an hour.

garo

I really doubt the fridge consumes 1kW. More likley its 1kWh per day or an average of about 40W.

I agree with championc - the spin cycle only takes about 200W. It's the water heating that is the killer.

garo

DrPhilG wrote: »

The new one seems to peak at about 600w and dries a load in under an hour.

Nice. Which one did you get?

garo

worlds goodest teecher wrote: »

We bought the house early this year, gutted it. All min A rated appliance, installed cavity and attic insulation, replaced inefficient oil boiler with new one, triple glazed front and back door, just approved for solar PV grant. Flexible with when we do washes. The payback on 14 panels with battery was long and out of our budget. Going with 8 panels 2.5kW system, no battery. If night saver would complement this system and help reduce cost I would be interested in exploring it further.

I would say so. But you would have to shift enough consumption to night-time to make the extra standing charge worth it. As someone said before 30% nighttime consumption is about where it becomes worth it for an average energy user. With solar, you will be reducing your daytime consumption so you would hit the breakeven faster. So I would say it will save you money.

If you have an EV, night rate is a no-brainer.

[Deleted User]

Garo are you related to circuit breakers?

I keep thinking it when I see your posts.

[Deleted User]

Sir Liamalot wrote: »

PWM is getting it's bottom handed to it as we speak.

MPPT won. 44% better. PWM kept dropping out in low light.
Same make, same class, same panels, same batteries, same discharge level.
Swapped the panels and cables over midway because I couldn't believe it.

Anyone looking for some programmable 30A 12V/24V PWM controllers PM me.

garo

Sir Liamalot wrote: »

Garo are you related to circuit breakers?

I keep thinking it when I see your posts.

Nope. First I head of them was about 20 years ago when I went to buy garo.com and it was taken :mad:

DrPhilG

garo wrote: »

Nice. Which one did you get?

Can't remember the model but it's a Samsung. The down side is that it introduced me to the Smartthings app which I've now got a bit obsessed with. Oil heating and all lamps running on smart plugs. Wife is itching to get a washing machine to match, lol.

Wiring up the bedside led mirrors in the bedroom to smart switches too.

garo

https://powercity.ie/product/133XEU

These look class. But way too pricy for me :pac:

daughy

garo wrote: »

I really doubt the fridge consumes 1kW. More likley its 1kWh per day or an average of about 40W.

I agree with championc - the spin cycle only takes about 200W. It's the water heating that is the killer.

Apologies, approx 1kwh per day for a fridge, that's correct also, it's the water heating that is the guzzler for the washing machine, was 4 years ago when I tested it. Poor mind is going.

graememk

Wash and tumble dry cycle

championc

Oh the power of data - undisputable

[Deleted User]

championc wrote: »

Oh the power of data - undisputable

I'm waiting on a day/night meter to be installed for those very reasons. Dishwasher, washing machine, drier, food dehydrator, 3 chest freezers, 2 fridges.

cubatahavana

Buying a new build with solar panels (5) without battery. Do they usually come with a way to know how much energy you harvest or would this be a non included add on?
Would a battery be worth it? Wife mainly working from home but not me.

[Deleted User]

I'd put the panels facing the sun at your highest demand hours before a battery.
After that I'd go hot water diversion.
After that unless the excess is inordinate I'd happily give it to the network.

If you can use the power during the day you'll keep the cost down and the efficiency up.

Some inverters have monitoring and/or daily readouts. Can't speak for them all.

Batteries only make sense if you're getting them free/cheap/haven't utility power.
It's extremely hard to justify extra thousands on hardware and the ~>20% efficiency hit to save a few cent every day.

I've been giving my excess away to the network (not much, I've only 2.5kWp) and the bills are down €25 a month.

[Deleted User]

Sir Liamalot wrote: »

I'd put the panels facing the sun at your highest demand hours before a battery.
After that I'd go hot water diversion.
After that unless the excess is inordinate I'd happily give it to the network.

If you can use the power during the day you'll keep the cost down and the efficiency up.

Some inverters have monitoring and/or daily readouts. Can't speak for them all.

Batteries only make sense if you're getting them free/cheap/haven't utility power.
It's extremely hard to justify extra thousands on hardware and the ~>20% efficiency hit to save a few cent every day.

I've been giving my excess away to the network (not much, I've only 2.5kWp) and the bills are down €25 a month.

That savings not to be sneezed at
I'm seriously giving the solar as a service provider some thought. I just need to get some bumf from him regarding specs and the inverter.
At 20 a month it's very doable. If I got 25 a month saving, it pays for the solar and I've a fiver in my pocket.

Can anyone remember who put up the OP for the saas provider?