Can we get a solar system that doesn't feed back to the grid + sizing advice needed

[Goboatingnow]

However, price is not the only consideration: during 'grid-down' you can't buy any grid power at any price, until it comes back online. If a storm takes the grid out for three days, and normally a storm also means no/poor solar production too, then batteries and a stand-by generator are the solution for most of us.
For my family we use the solar as our go-to input, and the grid as our back up during low-solar days (Nov-Jan especially). The base cost for the grid tie is $30/month or about a dollar per day.
We wired in a generator plug outside our workshop (where the solar equipment lives) and in the case of a prolonged winter outage, where solar is also not sufficient, we plug in the generator to the wall and charge up the battery pack for a couple hours, then shut down the generator again. Many of the house loads (fridge, well pump, freezers) run in cycles that are best supplied by the batteries rather than having the generator running non-stop waiting for those loads to need a cycle.

Grid failed in a storm twice on 10 years. Once for 5 hours once for 3 hours.

Grid reliability has been excellent

 

[OffGridForGood]

Grid failed in a storm twice on 10 years. Once for 5 hours once for 3 hours.

Grid reliability has been excellent

NICE !- I can say I will have power outages three to ten times each winter, and the outages can be a few minutes or three days depending upon the cause. Last April we had a late winter storm24inches of heavy wet snow that blocked all the roads and knocked down hundreds of trees. The plows and the hydro crews had to work together, since neither could do their job without the other, lines down on the roads, trees in the way of the plows, yeah it was quite a mess. We pulled power off our batteries for two days, then a neighbour helped me get to my honda generator and we charged up the battery bank in a few hours, shut down the genset to conserve the gas we had on hand (not knowing at that point how many more days we might need to wait) and the next day grid power was back online. My wife was so impressed with the shop solar back up, I got the green light to expand it and run a Critical Loads Panel (CLP) in the house from the shop solar. It all depends on your situation and environment, where we live in heavily treed rural area, we know the power outages will happen, just wonder when and for how long. Long sunny days this time of year, and we flip the house loads onto the CLP and save on grid hydro use too. Kinda win win to us in our situation.

 

[OffGridForGood]

Hi Everyone,

we moved into a new house and we’re planning our first solar system and we would be very grateful if you could help us out with any advice.

We have an East - West facing roof with some shade on one side. (The building next to us casts a triangular shaped shade on the center of our East side roof, that’s disappearing by 11:30-is.)

We would like to have a system that supports a 15kW/day usage in case of an outage on the grid on a winter day. (Our summer, normal usage is around 8-9kW currently, but we just moved in, we don’t have enough data points yet, we’ve been living on ready meals for the last 2 weeks, didn’t get new electrics etc.)

We’re in the UK (Northamptonshire), where we get 8-9hrs of daylight during winter.
Peak insolation hours are: January: 0.6 / February: 1.17 / March: 2.07 / April: 3.15 / May: 3.83 / June: 4.31 / July: 4.28 / August: 3.62 / September: 2.53 / October: 1.51 / November: 0.83 /December: 0.49

We had 3 surveys so far and talked to several companies, but we’re getting conflicting information. We would like to have an oversized system and can easily accommodate 20 panels (8kW system) on our roof (16 on the West side, no shade, and 8 on the East side, probably also safe from shade, but there might be some shady corners - we have no way to know yet; we just moved in and have trouble seeing the roof and calculating the shade-free area.) Therefore, the 8 panels on the shady side will have either optimisers or microinverters.


So far we got 3 suitable offers:

Option 1: this is the most expensive. We understand this would allow us to use “island mode”, which for us, ignorant people means pretty much being independent from the grid and provide enough electricity for our needs, winter/summer and turn the incoming grid power off, if we llike.

We were told we cannot NOT feed electricity back to the grid, because once we’re not using more, and our batteries are topped up, the produced energy NEEDS to go to somewhere, and that’s the grid (we can either sell it or give it away for free, but it needs to go there.) Is this correct?

This system would have:

• 20 Longi Hi-MO 5m monocrystalline panels
• 8 optimisers
• 2x3.6kW GivEnergy hybrid inverter
• 2x9.5Wh GivEnergy batteries. (If we want to reduce costs, we can have 2x5.2kWh batteries instead.)

We’ll need power diverter and PV protect but no voltage optimiser. We were told this is a big work, the electrician would change our system so much they will issue a new NICEIC certificate. (Bear in mind it’s a new build.) We understand they will rewire all the electrics with a secondary feed to the solar system.

We would have a changeover switch - in case of blackout, we would be able to manually switch to full solar mode/separate ourselves from the incoming grid electricity. Our electrics will still shut own, but we can just switch to use our batteries instead of the grid.


Option 2: this would need us to choose a couple of slots from the fusebox to be connected to our solar system. We won’t be able to operate all our equipment from solar in case of a blackout, just the ones that are wired to our solar system (e.g. boiler, fridge, micro, wifi, computers or whatever we pick).

This would have:

• 16 Longi Hi-MO 5m monocrystalline panels
• 8 optimisers
• one 5KW GivEnergy hybrid inverter
• one GivEnergy 9.5kWh battery

Option 3:

this company said they don’t even deal with connecting us to the grid - what we want is easy and possible without feeding electricity back to the grid and it’s possible. (Is this true?) No visit from the grid people is needed, no permission, no power diverter, no PV protect is needed.


They gave us a quote for:

• 20 Longi Hi-MO 5m monocrystalline panels
• 8 optimisers
• 3 GroWatt 6.5kWh batteries

Which option do you think is best from the above? Option 1 is almost double the price of option 3.

Meanwhile, another company keeps telling us, we’re really oversizing our system, it doesn’t make any sense; we should get 10-12 panels max.

What do you guys think of the above options?

Since we’re in the UK, one of our worries are that during winter we won’t produce enough V to startup the inverter in the morning, unless it’s very sunny, so we might be spending a lot of money on something that might not work. (Stupid side question: isn’t it possible to start up the inverter from batteries?)

Our main objective is not to save money, but to be able to use our essential equipment if there’s an outage, especially during the winter (last year there were outages that lasted for 2-3 weeks in some areas). (Combi boiler with a 40W pump, 900W micro, 3 computers, maybe a little electric heater etc.)

If we could avoid feeding electricity back to the grid, we would like that - it would indeed save us some money on equipment and hassle, getting permissions, visit from the grid people etc. We got conflicting info about it, so we don’t even know if this is possible or not.

We would be very grateful for any advice and confirmation about our inverters (needing 120 V or 150V startup voltage) to start working early on a winter day… I couldn’t calculate for how long it would take for them to start up in a cloudy, winter day.

Again, we don’t care too much about the return of our investment - we want backup power supply in case there are weeks of outage or issues with electricity (and potentially gas) supply.


Thank you!


PS: You guys rock - we read through so much of your advice on this forum and learnt so much from you already.

I have seen some good Youtube vids from UK -

These folks have been working with thier Solar in the UK for a few years now, and post some good information on their experiences. Maybe a good resource to start with, given they share your local weather and supply chains.

 

[Goboatingnow]

NICE !- I can say I will have power outages three to ten times each winter, and the outages can be a few minutes or three days depending upon the cause. Last April we had a late winter storm24inches of heavy wet snow that blocked all the roads and knocked down hundreds of trees. The plows and the hydro crews had to work together, since neither could do their job without the other, lines down on the roads, trees in the way of the plows, yeah it was quite a mess. We pulled power off our batteries for two days, then a neighbour helped me get to my honda generator and we charged up the battery bank in a few hours, shut down the genset to conserve the gas we had on hand (not knowing at that point how many more days we might need to wait) and the next day grid power was back online. My wife was so impressed with the shop solar back up, I got the green light to expand it and run a Critical Loads Panel (CLP) in the house from the shop solar. It all depends on your situation and environment, where we live in heavily treed rural area, we know the power outages will happen, just wonder when and for how long. Long sunny days this time of year, and we flip the house loads onto the CLP and save on grid hydro use too. Kinda win win to us in our situation.

We had some snow in 2012 my pickup managed just fine. Grid never faltered, couple of guys in a backhoe cleared the lane ,

Mind you first reports this year warn of potential blackouts as backup generators operators bid for licences and have decided not to build leaving too much reliance on renewables. Seemingly the 70 data centres here are gobbling up all thd grid power

So who knows. Any back to my boat , houses are very overrated, no zombie appocalyse at sea.

 

[OffGridForGood]

No Zombies at Sea...are we sure of that?!
I have to ask, how does a boat use solar PV - or can you use floating flexible and just roll them out on the surface of the water!

 

[Influencer]

I would start with the opposite, as much battery as you want to afford and add panels when you want.
The AIO will charge your batteries from the mains and act as a super UPS to whatever you want to connect to it, as this seems to be your main concern.
Then later you can add the panels to try and remove your mains charging requirements. The AIO can blend both charge sources.

Say you had the AIO but no batteries or solar - so you were just running the grid power through it. What's the efficiency of that? is there any energy lost when the AIO is supplying grid power directly to your home? I assume if it's not converting to DC it would be minimal, but just checking.

 

[BillSF]

Unfortunately I don't think you actually can use an AIO unless you find something with very low standby power (Victron?). The 6548's run around 70W standby not sure about GroWatt... That's 1.68 kWh per day per unit whether you're using power or not.

You don't have any solar energy to waste on high standby power.

You might want to aim for a DIY with low standby components (I know Will always mentions Victron, maybe there are others?).

Get an automatic transfer switch (I think Will mentioned this is one video) that can charge your batteries from the grid.

Heat is often more necessary to survive than cooling (a spray bottle or a water bath can do in a pinch, or an evaporative vest like the road construction crews wear).

Electric heat requires a lot of power. You probably need a heat pump (MrCoolDIY?) to have electric heat be at all possible.


It gets to 25⁰ F fairly regularly during the winter where I'm at.... I have central electric heat (10 kW) that came with the house...super expensive, I try not to use it. I have a Monitor heater and a 150 gallon tank of kerosene....I believe I can burn biodiesel with this as well if I ever get around to experiment with making that. I'll probably get a MrCoolDIY for heating and cooling and I'll still probably also get a wood-burning stove. Having 4 sources of heat seems like overkill until 3 of them are down on a freezing night....A wood stove is straightforward, no finicky parts that might wear out on a cold, stormy night.

I'd suggest you get the heat pump and maybe a small wood burning stove and keep at least some wood around for emergencies (ask the people that froze to death in Texas last year of you're not sure about backup heat).

You probably want to get at least 10 kWh of batteries that you can charge up when electricity is cheapest....10 kWh of batteries with grid rate arbitrage plus 8 kW x 0.5 hours of insolation 14 kWh per day.... I'd probably up the battery to 15 kWh so you have more buffer.

Get a generator that can run on propane and have two 25 lb cannisters around. If you only have it for emergencies, don't ever run gasoline through it even if it is flex fuel (or keep extra replacement seals on hand).

If you can get more than 8 kW of panels by going off grid you'll need it.... However maybe as a cheaper solution you can setup mirrors / foil near the panels to focus more light on them.....not a good idea in warm climates since the heat will wear them out faster and lower their efficiency.... but with 0.5 hours of insolation, you're probably safe to try to get 2x to 3x that by focusing extra light on them (at least during the winter). Get bifacial panels and paint the ground (or roof?) white or put something reflective underneath them.

Other that, you need to focus on being super efficient with your energy usage to get your usage down.

 

[32 volt boater]

Wind turbines generate thousands of megawatt-hours of electricity every year in Northamptonshire.

Anyway it looks like the energy companies in your area like wind energy.

Do both maybe?

UK solar tracker company claims 30-60% more energy per year than conventional roof mounted solar panels https://heliomotion.com/

 

[32 volt boater]

Still got the link to the search www.google.com/search?q=Northamptonshire+UK+solar+tracker&tbm=isch

My first search click is always Images

 

[xcentric]

Initially, as another UK person) I was looking to backup the house for grid outages, which we do have - but realised the expense wasn't worth the hassle to do the whole house. I have separate UPS for router and internet, and a log burner.

It's worth thinking seriously about how often the grid goes down and whether you want to be independent of it. It's much more cost effective to have it as part of a multi-level approach to living - wood, solar, grid, batteries, generator if you like - which will then give you flexible heating and lighting approaches. Also I don't understand why you don't want to feed back into the grid - in the UK the Octopus tariff allows you to charge batteries overnight on cheap rates and use them during the day, cutting your bills by a half - and if you have enough power you can feed back into the grid at peak times for about twice what you paid to get it - all of which is socially responsible, environmentally helpful, and helps the financial payback. We did battery only for a bit, now adding panels.

As to your options, I'd consider what people have said on here to see if you want other quotes for other systems, but my experiences are that many solar installers are very expensive for not enough knowledge - you might consider finding a knowledgeable electrician. Certainly increasing your knowledge by asking questions on here is sensible.

Finally - we reckon it'll be about 2.5 years to pay back our system - DIY design, DIY equipment choice (all guided by here), self + electrician install - and that once done any new panels we add will pay back their cost in less than a year because of the load shaping we can then do. Without grid export and import, the sizing of the unit esp batteries would have to be massively different, the costs about 4-5 times higher, and the payback probably never.....