20kw system Some help for the uninformed

[bjhmilla]

Hi folks, appreciate any help you can gove. Moving to a new property with a large field attached so wanted to get a project together for a ground mounted system. Aiming for as close to self sufficiency as possible albeit there will be a grid connection as uk winter not especially conducive to off grid. not worried about feeding back to grid.  (Does thst mean you dont need dno permission or do you need thst regardless)

Before going to anyone. I wanted to get an idea of what im asking for.

Its a large v old house with some electric heating. So not efficient, more places to put power than i could ever generate (move central heating off biofuel/swimming pool etc). But settling around 40kwh per day as a sensible figure to start with.

What would a good ground based system look like.
I had 20kw in mind,

Any advice on the rest ie. Panel brands, Charge controllers, Invertors, 3ph/1ph single or multiple. Suggested battery type and size and number, Mount systems ie. The ones that are static or tilt to increase efficiency.

Ill likely end up doing the grunt work. setting the mounts and panels maybe even running some wires in ducting etc as im from a civ eng background but would be getting an installer to do everything electrical but i just want to be armed to get some quotes in so i know what im looking at

Thanks in advance

[Alan Ambrose]

Suggest start with the overall sizing and economics calcs. It could be a quick comparison with extra insulation / airtightness would put it into context. Easy to get an idea of monthly generation per panel from pvgis:

 

 https://pvgis.com

 

You’ll almost certainly need dno permission.

[Jinglish]

What is your primary motive?

Is it..

>ROI (Return of investment)

>Go "green" no matter what it costs

>Live off grid

 

Depending on what you prioritise would help factor the choice of renewables.

[Dillsue]

You probably  want to speak to your planning department to see if there's any restrictions on building your own small solar farm. After that speak to your DNO to see how much export they'll allow. Once you know if either or both of those are going to restrict you, you can start designing a system

[SteamyTea]

All the above, but before you start invest in energy reduction. The kWh you don't need is worth a lot more than the kWh you generate costs.

As winter is the problem, you need modules to face the lower sun angles (more vertical).

This compromises land usage as you cannot have module rows too close together because shading becomes an issue.

In the past this was dealt with by modules tracking the sun, but as module prices plumetted, tracking systems fell out of favour because of the high costs.

 

The secondary part is storage.

Storing energy in water, especially if efficiency is boosted with a heat pump is the cheapest and easiest, but does require lots of space, mainly for the insulation.

Chemical battery storage gets a lot of people very excited, but financially is a disaster and relies on some very dodgy accountancy to make it price parity with grid supplied power.

 

Cut your usage first, it is so much easier and cheaper.

[Russell griffiths]

My neighbours have a system that moves around to track the sun, far more efficient I believe. 

[JohnMo]

1 hour ago, Russell griffiths said:

My neighbours have a system that moves around to track the sun, far more efficient I believe. 

Should be as it always pointing at the correct angle and direction. A fixed panel is in the correct (best) orientation for an hour or so - maybe per year. But the DNO treats your fixed system, as always producing full inverter name plate values for export purposes. Which is a little disconnected from reality.

[bjhmilla]

Thanks for the comments

The motivation is kind of a mix of wanting to be as "off grid" as poss but also a bit of protection as this is a v 1850 victorian standalone farmhouse with single glazing and single skin brick walls (no cavity) so you can imagine the heat loss is a nightmare  but also things like retrofitting ext or int insulation are a no go because of the listed exterior and the interior features. 

 

Heating is currently a mad mix of a few electric rads, oil aga, some rooms oil central heating, some rooms a very old log furnace feeding rads (not auto). Hot water is electric immersion. So the whole heating system needs renewal. 

 

With the view that the heat loss is huge, air source HP seems non starter, plenty of land so GS hp is poss but again would this overcome heat loss without mad amounts of new rads and even then no insulation 

 

So my view is that we need to aim for as much electric gen in the winter as possible to help offset what will probably end up being a new oil or biomass heating system. 

 

Even in the summer when not needing elec heating, pool has an ashp

 

Plenty of space and outbuildings just trying to mitigate the sky high heating bills

 

In terms of feeding back. I know dno likely wont give permission for a system this size to feed in so thought that bit might be a non starter but obvs that would be great if they did allow

 

[SteamyTea]

5 minutes ago, bjhmilla said:

 

With the view that the heat loss is huge, air source HP seems non starter, plenty of land so GS hp is poss but again would this overcome heat loss without mad amounts of new rads and even then no insulation

Heat loss is what ever it is and is totally independent of the heating source.

That is why you have a power rating on heating systems, and not a radiator surface area rating.

 

You may be better off getting a diesel CHP unit to help cover the winter.

 

Just for a laugh, measure how much energy, and the time it takes to raise your pool up by 3°C and how long it takes to drop back down again.

[Jinglish]

With the age of your property IMO you are limited with what you can do given your goal is to reduce your overall heating bill with the potential of being off grid. You could spend a fortune retro fitting insulation, windows etc. with almost no return in your lifetime. I'm all up for saving energy but some properties are just not fit for this purpose. As attractive as a GSHP or ASHP sounds your property don't have the fundamentals in place to support it. I think you will need to look at each measure independently and chart up a cost vs saving vs timeline in a table. 280mm loft insulation if you don't have is probably the lowest hanging fruit. Your biggest heat loss will be from your walls and I don't think there is any sense here in trying to mitigate your single skin without major cost and compromises.

 

If you do overhaul your heating system then I suppose the main choice would be radiator feed by OIL/LPG/Bio Mass OR go for electric all round traditional or even infrared based. If going with electric then you can work out if Solar can offset your usage. Either way your choices are expensive and as said earlier doubt you will ever see a return.

 

Have you tried what grants maybe available? https://ukem.co.uk/ (You be surprised what you can get if you call, ignore the benefits your house should be very low EPC so would likely qualify)

Edited July 8 by Jinglish

[SteamyTea]

9 hours ago, Jinglish said:

Your biggest heat loss will be from your wall

Probably from the slab/foundation in reality and that can probably be insulated, or replaced.

Uncontrolled air leakage is probably high up the list.

Just getting the walls back to brick and replastering could make a huge difference.

North and east facing walls, are the ones to insulate if you can as the have the least incidental light on them, so are generally always colder.