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Dan's 57Kw Build
#1
Like many I have been absorbing all the knowledge you guys have been kindly passing on and have began my own 57Kw build.

So the idea behind my build is I want to build a home next year that is off grid (electrically). I plan to have mains water as I cant guarantee the rain water harvesting can sustain us if we continue to have summers like we just had in the UK, plus connecting to mains water is relatively cheap as opposed to connecting to the grid. It will be super insulated with ground source heat pump for heating and hot water.

Initially I planned to have 120 size packs for a 14s system and then add further 14s packs in parallel as I get enough cells. And was going to weld up a nice housing and have it powder coated to put them all in. However I found this box lying around in work which had battery storage written all over it so it changed the plan a little, hence the 57Kw build.










Ive done a basic drawing on CAD to help get an idea of spacing the packs evenly and they should fit like a glove leaving around 25mm gap per pack and plenty of room front and back for air flow. I can't decide weather to cut a large section out of the door or not and put a pice of perspex or similar with lots of holes in for venting and also to see the longmons or just leave it and put some vents along the sides.



As you guys know better than me gathering and processing cells is time consuming work. I've been collecting for around a month or so now and have around 1500 tested cells and just the other day I picked up over 300 packs for £150 which should give me a further 1800 give or take. 
With me using 240 packs its going to take 3,360 cells for each parallel totalling 6,720 cells needed. My cell cut off is 2,000mah so I'm guessing I'm going to have to test around 9,000 - 10,000 cells to get what I need.  

As far as bus bars go I thought I could pick a few brains for suggestions. My plan is to have 3 pieces of U shape 10mm2 copper wire to connect all the 0.15mm tinned copper wire fuses to each cell and then have 16mm x 4.5mm copper flat bar to connect each pack together at each end as follows.



Ideally I would connect one to the back and one to the front but it would be a pain in arse to get to the back bolt to pull individual packs out. Do you think it would still draw current from the cells at the back of the pack if i was drawing say 120 to 150 amps from the battery bank? It would only be 5.4 amps per 240 cell pack.
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#2
That setup looks great and yes the back cells will give power. If you start pulling 100A per pack then you might have some of the front cells giving more than the back but Down at your level it will not be a problem
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#3
What are you planning for energy generation? Solar? Hydro? Wind? Give details. Site size, orientation, latitude, etc...

What is your projected energy usage? What is your regular electricity draw excluding heating? What size is the property? What are your projected heating requirements?
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#4
That box/housing/fridge sized battery container looks perfect for the project! Would love to know the plans for recharging also
If you'd like to support the forum please feel free to use my affiliate links to purchase all kinds of stuff for your projects 
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#5
Sorry fellas, forgot to mention that bit. The house will be located in North Wales, UK and will be around 180m2 - 200m2. 
Generation will be from Solar with around a 12 - 15kw array. The side of the property will be directly South facing with a large triple garage along that face to with both the garage and the house having as many panels along those sides along with plenty of glazing to harness as much heat as possible also. Off the side of the garage will be a plant room lets call it, which will house all the ground source heat pump kit and the battery bank Inverter etc.

As I want to have slate for the roof tile I did think about using these PV slate tiles but I think the price of them and the power they produce wont cut the mustard. So I'm going to go with in built panels that sit flush with the slate and will be similar colour so will blend in nicely plus I wont need to buy as much slate.


http://www.gb-sol.co.uk/products/pvslate...gJeqPD_BwE

I know that from November to February I might struggle to get enough generation to top up the battery, I mean I should be able to go for 4/5 days with zero sun with the battery I'm building but I'm going to get a small wind turbine around 1.5 - 2kw and I'll put it on the gable end of the garage which should help trickle charge the battery bank. I'll install it so its detachable and I'll take it down between March and October. But I'll trial it first as I may not even need the wind generation. Hence the 12 - 15kw array to get me through the winter months.

Looking at my electricity bills I use on average around 13Kw a day, I've been renovating the place I'm currently in so a lot of use of tools etc plus theres some other things I could change that use a lot of electricity so I reckon on a normal day it would be around 9-10kw a day.
For heating and hot water I currently have a gas combi boiler which in the winter can use around 6kw a day.
The house I'm in is a 3 bed detached house which is probably half the size of the one I plan to build, that said it is solid brick construction with no insulation so basically leaks heat. The new place will be above building reg standards of insulation with triple glazing and as air tight as possible.
The element I have no idea on power usage which hopefully some one has some experience with is the ground source heat pump for heating and hot water?.

As for the inverter I was going to go for 2 or 3 MPP Solar PIP-5058MS and get the parallel wiring kits as they are relatively cheap to get a 10 - 15kw inverter. But I think it would be way too inefficient, I know that Daromer has the 10kw green beast but having heard him mention how inefficient that is and how much power it uses just sitting there puts me off that one to. 
What do you guys suggest as an efficient 10kw or 15kw inverter, The Victron ones look a good shout but man they are not cheap!
hbpowerwall likes this post
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#6
Oh wow! Man after my own heart! Building your own low energy home is a dream i'm yet to make reality. good for you!
I'll PM you if you fancy hearing about my not quite so grand attempt. I'm trying to improve the energy efficiency of a 1980's build timber frame detached house over in Essex. Only have 2kw of panels and 7.5kw of diy powerwall so far, but its growing.
With solar insolation about the same (maybe a tiny bit more?) as what you'll get in Wales, you may want to hear how 2kw have been performing recently in this weather (Spoiler: its not great, but you already know that!)
Also - 300 packs for £150? Well played!
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#7
Hi Wardy,

Sorry for the late reply.

You mention that you are building an off grid (electrically) property of up to 200m² and heated with a ground source heat pump, and you may have up to 15kWp of solar panels. 

Unfortunately you shall find achieving the above close to impossible. The heating season coincides with the solar isolation is at its lowest, so your energy demand is highest when you are least able to generate it. This pretty much rules out solar powered heating. Many people don't realise just how much energy it takes to heat a house for a day in mid winter!

You also mention a wind turbine. I'm pleased that you are looking at diverse energy sources as you will certainly benefit from having complimentary generation. However, building integrated wind turbines are nothing short of a con. Wind turbines need a clear and uninterrupted fetch so they are working in clean laminar air flow. Buildings, trees and hedges all create turbulence and takes the energy out of the wind. This is the reason all wind turbines are mounted on tall poles. A building mounted wind turbine will merrily spin and give the impression that it is working, but the actual energy production shall be a fraction of what it could be if the turbine was mounted in the middle of an open field. It is unlikely to every recover the cost of installation. Take a trip over the to the  Navitron Forum and see what they have to say about building mounted turbines. There are quite a few people on there that make and fly turbines. You may also want to take a trip to the Centre for Alternative Technology given you are in Wales.

Your reason for going off grid electrically appears to be driven by the cost of connection. If this is the case, then you should find out what proportion of the works is contestable. You can undertake the contestable works yourself at a vastly reduced cost compared to what the distribution network operator (DNO) will charge you. You should also haggle over the non-contestable works costs as they often try it on. If you do go off-grid, you shall find that it is not a cheap endeavor. You must size your equipment to cover your peak usage, not your average. That means that you are paying for equipment size to cover needs that you only use a few percent of the time. You may also wish to have some redundancy in your system too so that if an inverter fails you are not stuck without electricity for a week while you source and install a new one. Ie two parallel 5kW inverters may be preferable to one 10kW inverter.

It is good that you mention a ground sourced heat pump and not air sourced. Air sourced heat pumps suffer greatly with the lower ambient temperatures of winter when compared to the shoulder months & summer months. Air sourced heat pumps are further frustrated by the damp oceanic climate in Britain when winter temperatures often hover just above freezing, both with high humidity. This means that the evaporator coils often ice up and need defrosting with an electrical resistance heater. Air source heat pumps are often over sold in UK. They can and do work well in Europe where the climate is drier. I've spoken to people who had them installed and then quickly found out it was costing them far more than expected, and subsequently ripped them out. Here is a good article on the effect of cold humid climate on heat pump performance.

The advantage of a heat pump depends on the availability and price of the fuel. If you only have electricity, then a heat pump will help you as the coefficient of performance (COP) - the amount of useful energy moved divided by the amount of energy consumed - is greater than 1.0. COPs of up to about 6 are touted, but this may not be achieved and you must do your homework. In UK winter the COP can degrade to 2.0 or below. Therefore you must look at the relative cost per kWh of each fuel type. Mains gas for example is about 3.5p/kWh, compared to electricity which is about 16p/kWh. So in order to be financially worth installing a heat pump it must achieve a COP of 16.5 / 3.5 = 4.7 just to break even, before installation costs which are typically higher than gas boiler. Bear in mind that most of you heating demand is in the 3 coldest and dampest months so you really need to look at the heat pump's COP for those conditions and not just the headline figure given by the manufacturer. They almost never provide humidity related data.

Now let's get to your solar ideas. The good news is that you 15kWp planned installation could potentially meet your electricity needs, providing it is south facing and completely unshaded. Here is the expected production for a 15kWp south facing system in North Wales. Values expressed in kWh per day average.

Code:
        35°       75°
Jan    15.40     18.30
Feb    24.60     26.70
Mar    42.00     41.40
Apr    51.20     44.70
May    58.10     45.40
Jun    56.30     41.70
Jul    53.90     40.90
Aug    46.80     38.70
Sep    41.60     39.10
Oct    28.20     29.50
Nov    18.60     21.70
Dec    13.60     16.80

The 75° panels are ground mounted and angled optimised for the winter sun at 75° to the horizontal. The 35° panels are building integrated roof mounted. You can see the difference the seasonal optimisation has. So a 15kWp system that is optimised should cover your daily usage when accounting for inverter & charging losses.

 
Click to embiggen.

Attached is an Excel screen grab that shows solar production for both 35° & 75° systems against the heating demand for a small house of approx 85m² in the year 2007 - 2008. As you can see clearly in the graph the demand and production are 180 degrees out of phase. Also note just how much energy is used for heating. 70% of the annual demand is consumed in the 3 - 4 coldest months. As you can see these from the numbers that house is using around 60kWh per day in December and January. Your demand will scale with size.

My house is typical of UK houses, being double glazed throughout in 2016, cavity wall insulation, 300mm loft insulation and combi boiler. I used 104kWh/m² per annum. If you build to Code for Sustainable Home Level 6 you shall achieve 46kWh/m² per annum. That is hard to achieve without attention to detail in the design and up-front costs. But you could therefore project your heating demand as 200m² * 46kwH/m² = 9,200kWh. You shall need hot water which shall account for another 2,000 to 3,000 kWh per annum. Multiply the annual heating demand by the monthly percentages in my picture to obtain your monthly usage... Divide by 30 for daily demand.

Now, apply the COP of your heat pump, which should be fairly easy to find for a GSHP to work out your electricity demand. Ie if you have a heating demand of 40kWh per day with a COP of 4, then you need 10kWh of electricity for heating per day. 

So now you will see that a 15kWp solar array cannot supply the heating demand even with a heat pump. Realistically you shall need 35kWp or more. Sorry.

So you need to ask yourself some questions:
Can you really go off-grid for electricity? I think yes, providing you heat your house with Gas, Oil or Wood for the coldest winter months.
Is it cost effective to go off grid? Probably not, unless you are a long way from mains electricity.

If you can connect to gas I certainly would. It's the cheapest fuel you can buy, and opens up the possibility of combined heat and and power in the winter. A CHP generator will produce approx 25% electricity, 60% heat & 15% waste from each kWh of fuel. So a CHP plant making your electricity demand of 13kWh per day would produce approx ((13kWh / 25%) * 60%) 31.2kWh of heat for free. The cost of electricity would then be 3.5p/kWh / 25% = 14p/kWh. You will generated 2.1p/kWh of heat per unit of electricity, giving an effective cost of 11.9p/kWh electricity.

Hope you're still with me...
I'll let you digest and comment.
-Tim
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#8
Hey Tim, I was hanging on towards the end there but I’m still with you. Ha

Thank you for taking the time to write such a detailed reply. 
Even if I do feel Deflated by the data you provided..

Mains gas is off the cards, unless I got a tank installed and if I was going to go down that route then oil would be a better option.
But I really don’t want to, I want to be self sustainable from renewable energy!. 
I know the numbers don’t lie but it’s hard to know for sure what my energy consumption will be until I’ve built it and trialed it.
I failed to mention that there will be a log burner installed and I believe if you use the heating wisely for example it will have underfloor heating and if that comes on earlier in the day when the sun is out and the screed slab will act as a radiator storing the heat. Obviously it will need to be on later in the evenings on colder days but you get what I’m saying. That coupled with a build as close to passive house standards as possible and large glazing along the south face.
As for the 12 - 15kw array, I assumed that this was way more than my needs required. I plan to max out both south facing roofs with as many panels as they can hold so it could likely be 20kw + as the price Of a pannel And the price of the slate needed I doubt there’s much in it.

I guess I’m just being optimistic and a little stubborn as I do not want to be grid connected.

What do you think to solar hot water to couple with the GSHP? 
I’m thinking it’s a waste of money given when generation is low in winter it will be useless.

I think the beauty of the wind turbine, all be it not as efficient bolted above a gable end it will be producing 24/7.
And if I’m still struggling in winter I could hook a generator to the inverter for emergencies

Thanks again for your reply!.

(11-16-2018, 07:11 PM)Daveyboy Wrote: Oh wow! Man after my own heart! Building your own low energy home is a dream i'm yet to make reality. good for you!
I'll PM you if you fancy hearing about my not quite so grand attempt. I'm trying to improve the energy efficiency of a 1980's build timber frame detached house over in Essex. Only have 2kw of panels and 7.5kw of diy powerwall so far, but its growing.
With solar insolation about the same (maybe a tiny bit more?) as what you'll get in Wales, you may want to hear how 2kw have been performing recently in this weather (Spoiler: its not great, but you already know that!)
Also - 300 packs for £150? Well played!

Hey Daveyboy

PM away mate, Any info on other people’s attempts on what we are trying to achieve I’m all ears. 
Along with any data that you have for the winter months. I’m sure It will be an eye opener for me. 
I could of got them cheaper if I had tried haggling but when he said £150 I couldn’t snatch his hand quick enough.. ha

Nice build you’ve got yourself to mate!. Have you hade a start on the pergola yet to house more panels?.
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#9
Totally agree that wind turbines mounted on buildings are a waste of time/money/resources, unless it's mounted on a 60+ft pole in a flat and _extremely_ windy area. Almost always, you'll be better off mounting more solar panels, perhaps at super steep angles on walls to maximize power output during winter.

A log burner will complement solar nicely during cold and dark winter months. Have you looked into wood pellets? The burner can usually start the fire on its own, and even add more pellets to the fire as needed (thermostatically controlled).
Typical units have an internal pellet tank that you need to fill every (few) day(s). For some units, you can have a pellet storage room (auto feed with a long auger), which you only need to have filled once a season.
While not as "clean" as wind power, the pellets are made from wood chips / sawdust, and are perfect examples of renewable biofuels.
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#10
(11-17-2018, 05:31 AM)ajw22 Wrote: Totally agree that wind turbines mounted on buildings are a waste of time/money/resources, unless it's mounted on a 60+ft pole in a flat and _extremely_ windy area.  Almost always, you'll be better off mounting more solar panels, perhaps at super steep angles on walls to maximize power output during winter.

A log burner will complement solar nicely during cold and dark winter months.  Have you looked into wood pellets?  The burner can usually start the fire on its own, and even add more pellets to the fire as needed (thermostatically controlled).
Typical units have an internal pellet tank that you need to fill every (few) day(s).  For some units, you can have a pellet storage room (auto feed with a long auger), which you only need to have filled once a season.
While not as "clean" as wind power, the pellets are made from wood chips / sawdust, and are perfect examples of renewable biofuels.

A mate of mine has a Biomass boiler, he had it put in about 3 years ago with a government scheme. The pellets you burn are relitivly cheap but the install is far from. He paid something in the region of 80k for the install and gets kick backs from the government of around 3.5k every quarter. He does have a massive house, over 500m2 and just as well as you need some space for all the boiler, hopper etc. you need a spare garage just to put it all in. 

My build budget is around 220k and that’s with me doing everything bar the brickwork and the plastering. So biomass is out of my price range unfortunately.

I liked what Tim mentioned about the size of the solar generation I would need to keep me a float over winter and what you mentioned about wind power not worth it. 
If I was to install a 30kw array, how much energy would that produce in the summer, like 70kw plus?. What would I do with all that juice, it would just go to waste. So I’m thinking as the plot has plenty of space, I could have an extra ground mounted array set at 75 degrees as Tim mentioned which I could just connect during the winter months or is this a bad idea you think?. It would be a lot of panels to store somewhere during summer.
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