New ground mount PV array

[Dillsue]

If your going for a moveable array make sure you consider wind load when it's gusty. Maybe accept that you'll never protect from the odd tornado but consider stormy weather that may be getting worse through the life of the array

[JohnMo]

The vertical panels are proving themselves very productive, just had a quick look and was producing around 5.6kW from the vertical and 45 deg arrays. 2/3 was from the vertical panels.

 

Yesterday was the least import we have done over the winter months. We imported 16kWh, for all heating, DHW and normal household electricity. We had -1 overnight and a high of about 6 during the day, so heating was on.

 

2kWh topped the battery up to 60%, as it was still quite full from the previous day. The rest went into running things on cheap rate period (12kWh).  The remainder of the day came from battery, PV (15.5kWh) and a final 2kWh at full price. Total price of electricity yesterday was £3.24.

 

Last year even with the 45 deg panels we still imported 17kWh each day on average, with heating and hot water coming from gas.

 

PV, battery, E7 and heat pump is proving to be quite a bit cheaper, than PV and gas boiler. Averaging around £80 saving per month over the winter so far (pricing corrected to current rates, so comparing like for like).

 

 

[Roger440]

7 hours ago, JohnMo said:

The vertical panels are proving themselves very productive, just had a quick look and was producing around 5.6kW from the vertical and 45 deg arrays. 2/3 was from the vertical panels.

 

Yesterday was the least import we have done over the winter months. We imported 16kWh, for all heating, DHW and normal household electricity. We had -1 overnight and a high of about 6 during the day, so heating was on.

 

2kWh topped the battery up to 60%, as it was still quite full from the previous day. The rest went into running things on cheap rate period (12kWh).  The remainder of the day came from battery, PV (15.5kWh) and a final 2kWh at full price. Total price of electricity yesterday was £3.24.

 

Last year even with the 45 deg panels we still imported 17kWh each day on average, with heating and hot water coming from gas.

 

PV, battery, E7 and heat pump is proving to be quite a bit cheaper, than PV and gas boiler. Averaging around £80 saving per month over the winter so far (pricing corrected to current rates, so comparing like for like).

 

 

 

So how big is the total array?

 

Certainly some whorthwhile power given where you are.

[JohnMo]

3.1kW at 45 deg, and 4.5kW vertical. Not bad for NE Scotland, have generated 200kWh so far this month.

[Russdl]

Bifacial panels mounted vertically facing east/west seems to be the new big thing if you have the space for them.  More expensive than standard PV panels though. 

[Roger440]

12 hours ago, JohnMo said:

3.1kW at 45 deg, and 4.5kW vertical. Not bad for NE Scotland, have generated 200kWh so far this month.

 

Thats pretty good. Higher tham most stuff ive seen quoted. I guess being vertical is the thing that makes the difference this time of year.

[JohnMo]

2 minutes ago, Roger440 said:

 

Thats pretty good. Higher tham most stuff ive seen quoted. I guess being vertical is the thing that makes the difference this time of year.

My output at this time last year with just 45 deg panels, wasn't worth talking about.

[Jenki]

Just had a quick look at mine, south facing , 4 kW North Scotland.

Today I've generated 5.2kWh already before 11 am.

Since November I've generated 720kWh.

Looking at a barn later this year and like the idea of adding a few vertical panels to it but would want to make that off grid with a small turbine and battery, with a view to take the ASHP & treatment plant off grid.

[JohnMo]

35 minutes ago, Jenki said:

Just had a quick look at mine, south facing , 4 kW North Scotland.

Today I've generated 5.2kWh already before 11 am.

Since November I've generated 720kWh.

That's really impressive.

 

My roof panels get lots of shade in the morning so very short productive day.

[Jenki]

23 minutes ago, JohnMo said:

That's really impressive.

 

My roof panels get lots of shade in the morning so very short productive day.

Unfortunately giving a lot if it away at the moment, as I've not got a solar divertor in place yet. (its on the long snagging / TODO list...)

[Roger440]

8 hours ago, Jenki said:

Just had a quick look at mine, south facing , 4 kW North Scotland.

Today I've generated 5.2kWh already before 11 am.

Since November I've generated 720kWh.

Looking at a barn later this year and like the idea of adding a few vertical panels to it but would want to make that off grid with a small turbine and battery, with a view to take the ASHP & treatment plant off grid.

 

Thats interesting. Im not keen on batteries, but want to use the power for heating. I wonder just how small a battery i can get to cover the start up demand of an ASHP.

[JohnMo]

6 minutes ago, Roger440 said:

 

Thats interesting. Im not keen on batteries, but want to use the power for heating. I wonder just how small a battery i can get to cover the start up demand of an ASHP.

I would look from a slight different direction. PV will get utilised before your demand takes from the grid. Any short falls are then taken from the grid.

 

So if your generating 2kW and your heat pump is the only thing online and is drawing 2kW, all good, no import. If it does a stop-start cycle and the inrush current is higher than you are generating, the shortfall will be grabbed from the grid.

[Roger440]

1 minute ago, JohnMo said:

I would look from a slight different direction. PV will get utilised before your demand takes from the grid. Any short falls are then taken from the grid.

 

So if your generating 2kW and your heat pump is the only thing online and is drawing 2kW, all good, no import. If it does a stop-start cycle and the inrush current is higher than you are generating, the shortfall will be grabbed from the grid.

 

Im rather keen not to get tangled up in the complexities of connecting to the grid. All seems rather hard. Ive read up on it multiple times. Still dont understand it. Happy to be corrected, but its a bunch more elecronics too. It also means paying other people large sums of money to do not a great deal. Probably badly.

 

My logic was to heat a big water tank. Any shortfall would be covered by the exsisting oil boiler. That being somewhat cheaper than buying power from the grid.

 

If i keep that entirely seperate from the rest of the system i dont need to involve anyone else. I can DIY the whole thing.

 

Well, thats my current thinking.

[JohnMo]

22 minutes ago, Roger440 said:

logic was to heat a big water tank

 

May be good way around things.

 

For a simple heat pump I quite like these (on paper at least).

https://eco-outlet.co.uk/products/activair-3kw-indoor-air-source-heat-pump

 

They don't modulate, but you don't need that.

 

They only pull 0.75kW and 5.2 Amps you could configure the ducts to do cooling in the summer also.

 

Small off grid inverter and almost a caravan battery to act as a buffer.

 

 

[Roger440]

10 minutes ago, JohnMo said:

 

May be good way around things.

 

For a simple heat pump I quite like these (on paper at least).

https://eco-outlet.co.uk/products/activair-3kw-indoor-air-source-heat-pump

 

They don't modulate, but you don't need that.

 

They only pull 0.75kW and 5.2 Amps you could configure the ducts to do cooling in the summer also.

 

Small off grid inverter and almost a caravan battery to act as a buffer.

 

 

 

Thanks

 

I think i need something a bit bigger as ill only have power to run it during daylight hours. If we take your example of 16 kWh during the day (and i can have a fair bit larger if i wanted too) , clearly i would want to use all that to heat water. 

 

Are you suggesting a battery before the invertor? What stops the invertor draining that?

 

Can you tell i dont really grasp a fair bit of this?

[JohnMo]

22 minutes ago, Roger440 said:

Are you suggesting a battery before the invertor

Something like this, would assume setting in the solar controller or inverter would stop drain down.

 

[Roger440]

18 minutes ago, JohnMo said:

Something like this, would assume setting in the solar controller or inverter would stop drain down.

 

 

Hmmm, interesting.

 

Whats the "thing" to the left of the solar controller?

 

What even is a solar controller? How does one identify a correct one?

 

Whilst i have indeed learnt something, for which im grateful, theres now more questions than i had before!

 

I do like the 12v batteries. Thats a tech i can understand, install and look after. Which is really one of my key objectives. I really dont want to be reliant on other people every time something goes wrong. With the exception of the alarm on my barn, there not a single thing i cant look after, maintain or repair myself. A failed alarm is not remotely a problem to life. Broken heating is.

[JohnMo]

Have a look at bumblesolar, they do packaged with decent descriptions.

 

https://www.bimblesolar.com/offgrid/complete-packages?utm_source=Google&gad_source=1&gclid=Cj0KCQiA5-uuBhDzARIsAAa21T_pBfVYnZg6RQ-C1fytSoJzP7IIHhN1WXUWTLpcdoWkxqSsrT8pzWQaAqdBEALw_wcB

[Roger440]

That got expensive real quick!

 

Though i see no descriptions. Just bundles.  But with stonking big batteries. Surely i only need a tiddler to take out any surge?

 

Obviously with a bunde, you know everything will work together, but at a significant cost. And i suspect, overkill in some respects for my application.

 

Im sadly, not much wiser, probably more confused after reading up on solar convertors. 

 

Maybe im dumb, but i cant find simple explanations/diagrams of what i actually need to do. But im probably searching for the wrong thing? 

 

I know what i want to do, which, granted is a bit unconventional, but doesnt seem radical in any way. Collect electricity, run ASHP to warm water up in big tank (thus avoiding a large expensive battery) . Does it really need to be this complicated? The 10kw bundles have no less than 7 devices stuffed full of electronics!!! Hardly likely to be reliable

 

If these are the sort of prices im in for, ill abandon it before i ever start. 

 

Sorry if i sound like im moaning. I get enthused with the ideas, but then realise im niether smart enough or rich enough to do them

 

[SteamyTea]

8 hours ago, Roger440 said:

Maybe im dumb, but i cant find simple explanations/diagrams of what i actually need to do

Your not likely to find a simple diagram with the correctly sized components for your installation.

 

But let us start at the beginning.

 

You have a Sun, the output, once rays hit the ground, at your location, will vary during the day, week, month and years.

This variation, usually measured in kW/m², but often shown as kWh/m² over a set time period i.e. a month.  The difference is the mean instantaneous power delivered, or the total energy delivered over a period.

Now as instantaneous power is very variable, the electricity that the modules (PV panels) is also variable.

Modules are generally fixed voltage devices i.e. produce no voltage when it is dark, once a threshold light level is reached they 'jump' up to a fixed voltage (usually around 0.5V per individual cell).  This voltage stays the same until there is extreme light when the voltage may either increase slightly, or decrease slightly (not worth worrying about those extremes).

The individual cell voltage is irrespective of the physical size of the cell, a 1 mm² cell will be at the same voltage as a 1 m² cell.

But we don't make a few large cells for reliability reasons, we make several relatively small cells and join them together in series.

You may have noticed that manufactures often specify the number of cells in a module i.e. 60, 72, 96.  This translates to a modules output voltage i.e. 30V, 36V, 48V, 12V modules will have 24 cells.

So when photons of light hit a cell, a voltage is produced (0.5V), if more photons of light hit a cell, more current is produced.  Current is measured in amps (A).  Current can be thought of as the thing that does the work.  Say you are chapping down a tree, one swing at it every 5 seconds.  To cut it down faster you can chop every 2.5 seconds, or get a heavier axe.  As the speed (the voltage) is fixed, the only option is a heavier axed.  To make a module 'heavier' it is just a matter of increasing the surface area so that it catches more photons.  It really is that simple.  Larger area, more amps.

 

Now getting back to a real system and why a 'charge controller' is used.

A basic charge controller does two things, controls the voltage and limits the maximum power.

This has to be done in all PV systems because of the varying sunlight levels which react a 'wild' DC current i.e. unregulated.

Now you are worried that the electronics is all a bit voodoo and therefore unreliable.  Like a car, they can be unreliable if the wrong one is used for the job.  Get a small car, fill it will people, stick it in second gear and redline it, it will not last long, get a large car, fill it with people use the gears appropriately, and it will last a very long time.

So think of a charge controller as a gearbox, it varies the fixed voltage (the RPM) that is delivered by changing 'gear' with varies the amps (the torque).  As voltage multiplied by amperage is power, V x A = W (watt).

But what comes out is a fixed voltage supply i.e. 12V, 48V, 230V, 600V, but with a varying power that is correlated to the amount of sunlight hitting the modules.

This output power is direct current (DC).

Posh charge controllers have got sophisticated and can be set up to limit the amount of power they deliver, this is important when charging batteries, very good charge controllers can also sense the type of batteries and the state of charge those batteries are in, and vary the power delivered accordingly i.e. more power when battery is flat, less power when it is reaching full charge.  They can also 'search' for the point, at any time, that will deliver the most power, this is called maximum power point tracking (MPPT).

A charge controller is not the same as an inverter.  An inverter, in its most basic form, just converts direct current (DC) to alternating current (AC).  Most PV inverters have a charge controller built in, which is why you can wire PV modules into them directly, they also have sensors and circuits in them that can detect the the grid voltage, the grid resistance and the load resistance.  This is done for safety and reliability.  Unlike a teenager in a car, they are designed to work nowhere near the ultimate limit of the components (actually most teenagers only think they are at the limit, they would shit themselves at the real limits of their cars, then hit something).

 

So basically, a charge controller takes varying power from the modules, changes it to generally a higher, more useful voltage, and lets the current vary.  That power is then fed into an inverter which makes it AC, at 230V (or whatever is appropriate), which then drives the load.  If the load is too high, it tries, via the MPPT to deliver, but if that fails it disconnects for safety and reliability.

 

Getting back to your question a while back, 'how big a battery is needed to start a heat pump'.  Not very big at all as it only needs to deliver a high current for a few seconds.  The right sort of battery is needed though.  A lead acid battery basically comes in two sorts, a cranking battery or a leisure battery.  A cranking battery can deliver a very high current for a few seconds, that is how it can turn over a large diesel engine, but a leisure battery is designed to deliver much lower current, but at a more steady voltage, over a much longer period.  Lithium batteries generally can deliver a high current and at a steady voltage.  This is because the chemistry is different (the number of free electrons and how far they are from the protons).

 

Now I know the above does not 'specify' which components need to be bought, and which order they need to be put in, but I am just trying to explain what each major component does and how they work.

To help specify, you need to know the maximum power that will be drawn i.e. heat pump starting current, and the length of time it needs to run off a battery.

[Roger440]

Thanks for taking the time.

 

I understood most of that before, but its something of a leap from there to actually doing it.

 

The bimble solar stuff had 7 boxes of wizardry. Which i simply couldnt understand what it was all for. Which you have confirmed with your explanation, which ties up with JohnMo's original diagram.

 

Sadly, car electronics have gone the same way as everyone else. They used to be exceptionally reliable up until a decade or so ago. Been going downhill ever since. Seem to have fell into the same process as everone else, cobble something together, dont complete it, dont test it, then release it anyway.

 

I cant think of a single electronic device that ive owned (cars aside) hasnt failed/gone wrong. And then, very relevant to this little project, no sooner have you bought it, it gets dropped like a hot potato and is no longer supported. Given the long paybacks on much of this stuff, you will likely be replacing it before you even get to payback.

 

Simple is better, but sadly, doesnt make as much money. If i could do it with relays, i would. 

 

Back to the task in hand, even with a free PV array and invertor, its questionable if this makes any economic sense by the time ive bought all the other clutter i need. It definitely wont if i have to pay others to do it.

 

I did consider ditiching the ASHP and using the solar to heat the water directly with an immersion heater. But thats hopeless in terms of its contribution to the heating costs. Id need an array 3-4 times as big to achieve the same aim, which would cost much more than the ASHP and associated changes. Would be simpler though.

 

My original plan of sticking 100% to oil certainly has simplicity and reliability on its side.

[SteamyTea]

19 minutes ago, Roger440 said:

If i could do it with relays, i would. 

You can. It is how regulators, and indicators, worked in Morris Minors.

They were fantastically reliable, lasted 15,000 miles, sometimes.

 

If you want to heat water directly, you could fit Solar Thermal. The m² efficiency is better than PV. Crap in lower light levels though.

 

As for the reliability of electronics, that is usually down to capacity mismatch. Why they usually have a continuous power rating and a peak power rating.

 

25 minutes ago, Roger440 said:

bimble solar stuff had 7 boxes of wizardry

Show us all what they are and I am sure someone can do a sketch, or RTFM.

[Roger440]

7 minutes ago, SteamyTea said:

You can. It is how regulators, and indicators, worked in Morris Minors.

They were fantastically reliable, lasted 15,000 miles, sometimes.

 

If you want to heat water directly, you could fit Solar Thermal. The m² efficiency is better than PV. Crap in lower light levels though.

 

As for the reliability of electronics, that is usually down to capacity mismatch. Why they usually have a continuous power rating and a peak power rating.

 

Show us all what they are and I am sure someone can do a sketch, or RTFM.

 

In my previous life i spent a lot of time doing reliability reports (on trains) . Despite what manufacturers would have you believe most of it simply isnt reliable. There were exceptions though, ill give you that. Worse, is that invariably, there is no fix. Just off an on again and no one is any the wiser. Until the next day, repeat, repeat, repeat. Fit new one. Shortly after, failed. My phone, repeated failures, all my computers, failures. Even the electronic timeswitch thing on my central heating fails, randomly, to turn on the heating. Ive wired round it to force on 24/7 and use the programmable thermostat to control instead. All just utter garbage. None of its reliable. I dont need to insert this crap into my heating system. 

 

Meanwhile on the trains, under the floor, the 2 stage voith transmission just got on with the job for 600k miles. Still working when you take them off.

 

Anyway, we digress.

 

Ive been round the solar thermal. Not much cop in winter, plus the solar array will be 200 feet or more from house, so eliminates that as a solution.

 

This was the bundle. Just what is it all for???? Is this really necessary to transfer energy from my solar panels to my heating water.?? https://www.bimblesolar.com/offgrid/complete-packages/over-10kw-off-grid-solar-power-kits/10kwcomplete-victron-600

 

 

[SteamyTea]

44 minutes ago, Roger440 said:

This was the bundle.

Had a quick look, most of it is generic stuff like cables, switches and connectors.

 

There are the modules and batteries, then the charge controller/inverter, the MPPT and the communication device (which is probably not needed, but is used to set up the system, so will be needed, think of it as a specialised spanner).

 

As it is all Victron kits, I suspect it is well sized for the system and won't be unreliable, why you pay a lot extra for it, they have done the leg work.

 

I am sure of you ask Bimble, they will have an installation guide.

 

[Dillsue]

Why off grid? Is this for powering some parts of a grid connected house?