Irene Kightley

I did this just under thirty years ago and since then it's been great fun. I still "work" but it doesn't feel like it.

I do what I want almost every day. (Do you like dusting?) If I have to do something I really should do that I find boring/what's the point, I'll only have to do it again in six months etc. then I just put very loud techno music on, dance around and pretend that I have to work for a living. "I am just a jobbing gardener, I am just a jobbing gardener". That can be my mantra some days.

This technique usually does the trick and if I don't finish the job then I think, "What the hell" and laugh at people who think that a clean house/garden/pair of jeans is important.

This sounds really corny but it was Permaculture that helped lead me to my mission to be free and I am so grateful.

Cristo, almost all LEDs are driven by a DC power supply and all MIFIs are too.

Small appliances like fridges, and so on are often DC because they're used by caravaners, motorists and truck drivers in their 12v or 24v vehicles.

I totally agree that two 50 watt panels are too small for this application but if Tim can get them cheaply from a friend, then he can put an even number together in a series/parallel configuration to produce 24v.

The battery needs to be charged as quickly as possible, within the 4 hours of 10:00 AM to 3:00 PM (assuming the sun is on your panels during that whole time)  because there are 3 stages to charging, and the controller will hold back on a complete charge until those 3 stages are completed.

Tim already has a 12v AGM battery and AGMs batteries like to be charged slowly and with a low voltage charge rate of just over 14v. Unlike open acid batteries, they do not need a regular, final, high voltage equalisation charge. They can be equalised but only if they are showing signs of wear and I'd suggest only a couple of times a year and by somebody who knows what they are doing.

That's one of the reasons I suggested that he use a 24v array to connect to his MPPT controller, because there will be a high enough voltage at the beginning and end of daylight to charge a 12v battery. Even with very little light hitting the panels, the chances of having a good voltage to complete the absorption phase are high - even in Scandinavia in winter. (60° - 70° N)

A good solar controller will have the option to select the battery type automatically and will deliver the appropriate charge to AGM batteries with no intervention from the owner - apart from the initial selection when you install the battery.

Panels these days are up in the 250-350+ watt zone, and are a reasonable size.

When talking about big solar panels and a very small ah battery, be very careful about using too many amps to charge a battery. It's tempting to buy bigger and relatively cheaper panels but the charge rate for most AGM batteries is lower than 12% of the C20 amp hour rating. Check your battery specifications for the recommended charging amperage and don't go above that.

Inverters have alarms on them that will warn you when the batteries get too low, so it's important to stay in touch with what's going on.

Tim will probably never need an inverter, they use current to operate and with only a small ah battery, the energy stored in the battery won't last long. An inverter alarm is useless if you don't hear it and I know many people who have ruined their battery bank by relying on an inverter to protect it. If it's really necessary, a tiny inverter could be used (We used a little 300w MSW inverter with a 300 watt system which we had) but used it only for a very short time each time and only on a sunny day.

The more expensive inverters cut off to protect the battery but all solar controllers with output cables to a load will cut off at a high enough voltage to protect your AGM battery. Use the controller to monitor what's happening, you'll get much more data than you'll get from an inverter - which either turns on or it doesn't !

You're going to need upwards of 700-1000 watts worth of panels to keep a 24 volt system charged up

Tim's system (Unless he decides otherwise of course.) will be a tiny 12v system.

Tim, I think using solar is a bit like buying a car, it's up to you to learn how to drive and maintain the car. Anybody can drive (ahem) but if you don't know how to maintain and install a solar system, then you learn until you know exactly what you're doing and why, or you get somebody you trust to design it for you and you learn as you go along - but always with safety in mind.

Hello Maddy, it's great to see you in here - a really comprehensive forum full of great people.

Congratulations on the new book. I loved your last book, Fertile Edges and it's still lying on my bedside table to be dipped into when I feel like a bit of inspiration!

I've recently added some work that I did for my Permaculture diploma to our new (So far unfinished) website and one of the design PDFs is called :

The first phase of the house at Sourrou : Applying the ethics of permaculture to building a comfortable home.

I've put the link here because I thought it might be an interesting addition to this thread and it should answer a lot of the questions people have been asking me about the build and the features we included in the house to make it more sustainable.

A lot of people were interested in how much it cost. We built the house for under 15,000 euros - that's 17000 American dollars. There's a breakdown of the budget in the PDF.

https://lafermedesourrou.com/wp-content/uploads/2018/01/First-Phase-of-The-House-at-Sourrou-SMALL.pdf

The wood consumption mentioned in the text has has dropped dramatically since we've put in windows and finished insulating the extension we built on to the house.

Yes Tim, I’m going to repeat myself a little here, so forgive me but I’d like to answer your message with a few comments on some of your points.

- battery goes with the panels (both DC)

I don’t understand what you mean by this to be honest as you won’t be using alternative current anyway.

In my last message, I suggested that you bring the cable from the solar panels (connected in series to make 24v) to the controller inside the cabin. An MPPT controller will then adapt to your battery voltage of 12v and your load output on the controller will be 12v too. (I suggest that you buy a controller with a load output which cuts off the load when the battery is low, most small MPPT controllers have them and that will extend the life of your battery.)

You’ll want to check the controller regularly to see if you have enough energy to run certain things and it’s handy not to have to go outside. If you keep everything outside and in 12v, you need to run a 35mm² cable which costs about 12€ a metre. That calculation is with a 3% loss in the cable. With a 2% loss, the cable will cost about 20€ a metre!

For 24v coming from the panels, 25mm² cable will do the job for up to 10 amps and is about 5€ a metre. It’s easy to find in the small ads - people often sell end of rolls cheap at the end of a big electrical job.

- separate the battery from the charge controller

Yes, but just make sure that the controller is no more than 50cms away and certainly not on top of the battery. AGM batteries gas less than an open batteries and they are fine used inside homes and in enclosed spaces such as camping cars.

- battery does not like cold so I need to insulate

An AGM battery is the best type for cold situations (Check the specifications for your battery for max and min temperatures) but, as I’ve suggested, put the battery inside or somewhere protected near your cabin but with decent air circulation and you won’t need to worry.

- A MPPT controller probably works best looking at my cabin site (I currently have PWM..)

In my humble opinion, there’s no point in buying an MPPT controller for such a small system unless you are going to use it for doing the job of reducing your voltage to keep the cost of cables to a minimum (Unless your site has some special thing that I don't know about).

Personally, I’d prefer to buy another panel with the same specs joined with original panel in series to make 24v and an MPPT controller which will cost in total around 300 euros, rather than buying 35mm² cable which will cost more than 600€. (12€ x 60 metres) This method will also give you a much better chance of charging your battery when the weather is against you.

A 20amp MPPT controller will cost from 120 to 350 euros. I’ve bought two cheap Epever controllers after reading several reviews and so far I’m pleased very with them. You can also find a lot of small second hand controllers as people sell them when they upgrade their system. I have a 20amp Morningstar which cost less that 50€ and it does the job perfectly after several years.

After reading you last paragraph, I realise that maybe I didn’t express myself very well in my last message. I’ll add comments to some of your ideas :

-While the panel obviously should be where the sun is and the battery where the panel is,

The battery does not need to be near the panel but needs to be near the controller in or near the cabin 30 metres away from the panels. The point of using an MPPT controller is that you can use smaller wires from the solar panels because you can run 24v to your controller which will then detect a 12v battery.

-From there run a wire (12 AGW or less?) to the cabin into a distribution box near the cabin from where the lights and some DC outlets are supplied.

12 AGW ? If you mean 12 AWG, a tiny cable this size will only carry 00.8 amps over 30 metres and will burn out very quickly and is extremely dangerous if you use anything over 10 watts! You need 2 AWG or 35mm² if you stay with 12v. Please look at the link for cable sizing that I put into my last message to see what I mean.

Sorry if it sounds like I’m being a PITA but I don’t like seeing people doing dangerous things or wasting their money. I’m not an electrician and I wouldn’t call myself an expert but I’ve more than 27 experience of installing and using photovoltaic solar panels.

This is posted with love and I'm only thinking about what's best for you.

Hello Tim,

With a 100watt 12v panel and your environment (Solar panels like the cold, batteries like the same temperatures as we do), you're forced to bring your solar energy to the batteries into the warm. That means you need to use a very thick cable (probably the same cost as your panel) because the lower the voltage in DC (Direct Current), the thicker the wires you need to move it.

Have a look at this cable sizing calculator.

http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

You didn't say what kind of battery you have - an "open" (meaning you have to add water from time to time) or a vented or gel battery but as long as you're (and your friends) are careful not to be silly around batteries (naked flames, smoking etc), they can live in a protected area in your cabin. Just don't put your controller too near your battery. (Learn more about this stuff.)

If I were you, I'd buy another panel with the same specifications as the one you've bought. Join the panels in series, making 24v and take that to an MPPT controller which will reduce the voltage to the same as your battery automatically.

Your cable will be less expensive (Use the link above and you'll see what I mean) and you'll have a much "longer day" to charge your batteries because the MPPT controller will keep on charging your 12v battery with as much sunshine as it can because it's using the beginning and the end of the day to keep it topped up with more volts than a PWM controller can. (If you don't know what I'm talking about, do your research on the difference between these solar controllers).

Charge everything during the day when your battery is full. A laptop is DC (It uses a battery) but don't use an inverter to charge it, use a car charger which costs about 29€ (this one is 18 years old)



You can also charge almost any small appliances such as torches, portable lights, telephones, tablets etc. with a 12v USB charger.

Keep your battery full for the evening/night and use LEDs or compact fluo lights - you'll be fine.

I've installed solar systems for friends with vans and yurts who only had a few hundred watts of panels and all of them are delighted with their lighting and their ability to charge stuff when the sun shines. Around the winter solstice it can become more difficult but you just have to get the candles out and enjoy the magic.

Thanks for all your lovely comments.

Sorry to take so long to come back to this subject but I attended the annual Permaculture encounter in France and the preparation for conferences and visits here afterwards take a whole month or so out of my diary.

Sebastian, I think I've labelled them OK - the text is at the top of each photo. Oh, and we started building the house before Brad Lancaster's book was published - I've never heard of the book and now I want a copy !

Alicia, here are some links to posts in the forum.

Off grid solar and wind

https://permies.com/t/85303/DC-grid-solar-system

https://permies.com/t/43331/Mixing-PV-wind

Rainwater harvesting

https://permies.com/t/20835/harvest-rainwater

https://permies.com/t/20847/Whats-join-rain-barrels-water

https://permies.com/t/15826/slope

Permaculture design in the home

https://permies.com/t/23053/permaculture-projects/Permaculture-Design-home

I've kept a record of the design considerations and the complete build from the start. In my website (Signature at the bottom of the page), click on "albums" then scroll down to "shelter" and there's a selection of photo albums with comments on our building activities.

Denise, we have a lot of great, free insulation material such as sheep and goat wool, straw and left-over rolls of insulation given to us by friends and neighbours, so we used a lot wherever we could.

In the (As yet unfinished) extension to the house, we used 37cms of straw, 20cms of hollow core brick, then about 25cms of either stone or light clay-straw insulation.

Denise, we're in South West France and several times a year, we're bombasted by extremely large hailstones during storms.



They have smashed the vacuum tubes on our solar water heaters, split polycarbonate sheets, dented our van and ruined tarpaulins covering our hay - but after almost twenty years, our photovoltaic solar panels are still intact.

Hi Nuno,

I've already posted a lot in the forum about the house but for those who don't know me or our place at Sourrou I'll just explain that for the first part of the build, I tried to follow all the classic guidelines for building an effective passive solar house. With a few small changes, it's working really well both summer and winter.

Here are some of the main elements :

The east/west axis of the house means that the sun orientation is used to the fullest for positioning solar water heating panels, photovoltaic panels and for benefiting from winter light and heat in the house.

Stones on some of the interior walls add thermal mass to be sun-warmed or heated by the wood stove. When we were building, it was interesting to see the light effect of the orientation of the house. We marked the walls with a trace at both solstices and the autumn and spring to determine the size of the overhang on the terrace roof which we built later.



Straw bales under the slab with "tiles" made by hand from clay from the pond in front of the house, cement and sand make a good thick heatsink for winter and stay cool in summer.



Spring equinox



Calculating the size of the overhang to maximise solar effectiveness



Big French windows on the south and sw side of the house to allow light to enter and small windows in the north to conserve heat.



Trees and climbing plants on the south facing terrace lose their leaves in winter and let the sun shine all the way into the house.





The small lean-to greenhouse acts as a cushion to the outside and helps heat the house in winter. In summer it's cooled by shady climbing plants and evaporating water.



The walls, floor and roof are super insulated and the outside on the south and west sides are surrounded by terraces and protected from the prevailing winds by several layers of hedges and trees.



The front door on the north wall is surrounded by plants and we leave the door open in the evenings when it's hot to get a nice cool breeze through the house.



When it is blazing hot outside, it's cool inside the house



The sun comes all the way in in the winter, warms the walls, the floor and the wooden furniture and the light is lovely. These photos were taken around the winter solstice.





I've probably missed out a lot of details but if you want to know more, just ask.

So I took a few photos inside and outside of our house to record the changing temperatures, then made the shots into a short video to illustrate one of the cool advantages of having a bioclimatic house which I though might be interesting to share.

No fans, no air conditioning, no energy use - just common sense.

It's 14h and I'm outside, then under a lean-to, I enter the workshop, walk past the cellar (with the door open) then go into the main kitchen then out of the west door to a covered south-facing terrace, then outside under the shade of some trees then point the thermo on the ground in full sun.