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okh
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Re: Off grid solutions

Thanks for this. Interesting.
For heating using a fireplace, are you considering pipes in your fireplace?
Did not know they existed as standalone units. But I have seen the principle used in some older fireplaces with copper pipes embedded in the fireplace walls. However, I am looking at some new clean-burning, closed fireplace inserts. Had one fitted at home last year, and the increase in efficiency was remarkable. We went from maybe 10-15% to some 85%. That means from some 1/2 kWh/kg of firewood, to almost 4 kWh/kg. (Completely dry wood = 5,3 kWh/kg, with actual normal moisture <20% somewhere around 4,5 kWh/kg). Biggest problem with the open fireplace though, was that the flue/damper had to be left open when we went to bed to get rid of CO. Meaning that the net effect was probably negative on a cold night.
One thing I have not seen, maybe I skipped it, is have you figured out how much power you are going to need? Because no matter how much power you need, you need to generate twice as much.
True. And at 60°N solar is rather limited in the winter. But for LED lights, phone-charging and radio, requirements will be minimal. For fridge (45W) or other appliances it would be a totally different story. Still, I suspect I shall have to rely on a portable power generator for power tools and topping the batteries. All heating/hot water will come from firewood.
And don't forget the batteries.
This is a bit of a headache at the moment. Currently almost all off-grid solutions come with lead-acid (agm), thick plated batteries. But here I suspect things will change over the next couple of years. New types of batteries with clever controllers should dramatically improve lifespan and weight/efficiency ratio.
With Wind and Water, they are basically maintenance free and last a life time if taken care of right.
I suppose you are right in theory, but in harsh climates moving parts are difficult. I have more faith in a solar system for now (but also because of distance to creek and strong turbulence around the building). I have used wind-turbines on sailing boats, and I was not impressed with output. To generate 50W, a pretty strong wind was needed.
1400W sounds like a lot, but I know hair dryers that use that much power! LOL!
Yes, well, hairdryers are out of the question. Not a great concern smile ok
[Sep 16, 2015 9:05:04 AM] Show Printable Version of Post    View Member Profile    Send Private Message    Hidden to Guest [Link] Report threatening or abusive post: please login first  Go to top 
ickle_bea
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Re: Off grid solutions

Hi guys, I am following this thread from the original thread 5778.

I am looking to purchase a property in Spain which will be my home but also a yoga/dance and eco-arts centre with accommodation for up to 15 workshop attendees.

I am looking at renovating a very old building but the outhouses and barns are also in need of complete renovation or possibly just full rebuild in which case I would aim for a sustainable build using elements of permaculture design.

This is not going to be a small property though so I need to look at what type of energy sources will work best for a bigger property as well as what the best building materials to use in a Mediterranean climate.

I am completely new to this and would appreciate any advice. It seems there are so many options for off the grid design and I just don't know where to begin.
[Jan 2, 2016 1:50:50 PM] Show Printable Version of Post    View Member Profile    Send Private Message [Link] Report threatening or abusive post: please login first  Go to top 
okh
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Re: Off grid solutions

How wonderful. Spain offers a lot of possibilities in terms of renewable energies, in addition to being a lovely country.

First question is, approximately where in Spain? There are differences in average sun-hours and not least average/winter temperatures. Then the property / house(s). Does the property have a lot of sun in general? South facing façade / roof with no shade from trees? What are the current building materials (degree of insulation)?

It will also depend on whether you want to be completely off-grid or just use renewables as supplement.

All that said, there are some pretty interesting developments in sustainable energy supply. And installation prices are coming down. My current favourite would be a combination of solar thermal collector, wood burning stove (or pellets). Even if you want to go very low cost, a solar thermal collector (air) should give considerable effect.

Also, Spain was quite early in using heat-pumps for water heating (came across it for the first time in Malaga early nineties - and that was an old installation).

Please keep posting what you find out. Sounds like an exciting project.

ok
[Jan 2, 2016 4:34:48 PM] Show Printable Version of Post    View Member Profile    Send Private Message    Hidden to Guest [Link] Report threatening or abusive post: please login first  Go to top 
okh
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Re: Off grid solutions

Just to elaborate, in addition to the above. Just read an article today (in Danish, I am afraid and promoting one brand, so I will not link), but it explained modern mass heaters, like the Finnish variety. The one I read about came with water heating for floor and hot water, and it could be combined with a solar thermal collector. A really interesting solution provided you have reasonable access to firewood. The beauty of this system is the heat retention so you will not get all the heat at once like with most firewood stoves (in other words, it should be good for winter in Costa del Sol).

But for full autonomy you need to consider using alternative sources as well. Photovoltaic for light etc. But also possibly gas for cooking and supplement (you will not use much, so it is justifiable even in an eco environment). And then there is a fuel cell, like this one in one of the most beautiful spots on earth, Savoie ...

Still, I would have gas / generator back-up. Unless, of course, you are a total purist...

ok
[Jan 14, 2016 6:22:58 PM] Show Printable Version of Post    View Member Profile    Send Private Message    Hidden to Guest [Link] Report threatening or abusive post: please login first  Go to top 
okh
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Re: Off grid solutions

A crisp -18°C outside and time to reassess some energy investements.

Extra house insulation a while back, brought heating costs down by some 20%.
New electric floor heating in basement (up to 120W/m³) keeps house relatively temperature stable. (An old house in a cold climate could require as much as 200W/m³, modern houses should be able to manage with 1/4th or less).

Firewood is blazing of in a relatively new stove (installation cost around €4000) delivering 2500-11000 W. No reliance on the grid, except for frost protection. Cost is interesting, and it is well worth comparing firewood quality and prices. Dry firewood will deliver approximately the same kWh pr kg regardless of whether it is heavy or light wood. The variables are the cost, moisture content and not least, stove efficiency.

The long and short of it is that a good stove with good firewood will deliver up to 4 kWh pr kg of firewood. But a quick test revealed that the actual cost pr kWh here ranged from €0,1 to €0,2 depending on the firewood quality and price. Seemingly similar sacks of firewood vary greatly in sack weight, dampness and price. So much so that the price/kWh more than doubles from one retailer to another. That was surprising.

ok

Stove efficiency
Open fireplace Modern stove

Wood moisture kWh/kg 15% 50% 80% 85% 90%
0% (does not exist) 5,3 (0,8) (2,7) (4,3) (4,5) (4,8)
Very dry wood 10% 4,7 0,7 2,4 3,8 4,0 4,2
Dry wood 15% 4,4 0,7 2,2 3,5 3,8 4,0
Relatively dry 20% 4,1 0,6 2,1 3,3 3,5 3,7
Damp firewood 25% 3,8 0,6 1,9 3,1 3,2 3,4

Normal firewood will have a moisture content between 10% and 20%. Moisture over 20% is not acceptable. Getting good efficiency from a stove (85%), requires a modern construction and knowing how to use it.
[Jan 15, 2016 10:21:20 AM] Show Printable Version of Post    View Member Profile    Send Private Message    Hidden to Guest [Link] Report threatening or abusive post: please login first  Go to top 
okh
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Re: Off grid solutions

Some reflections on sun energy. The sun provides roughly a kW pr m³ at earth surface. Manufacturers of thermal sun collectors claim to be able to exploit up to 70% of that - which can either provide some hot air ventilation (air collectors) or quite a lot of hot water.

For electricity (photovoltaic), solar has a lower output - in the range of 15% although newer systems may yield more. In practice, however, a lot of variables come into play. So looking at empirical data, it seems that manufacturers of photovoltaic panels estimate between 100 and 200 kWh/m³/year in Europe.

Problem is that output is lower in the winter (when days are shorter and weather less forthcoming), which means that the installation needs to be dimensioned based on winter electricity needs. Still, thanks to low-energy lamps, you will get quite a lot of light from a relatively small, correctly angled installation.

Realistically, it seems many rely on a fossil supplement to charge (top-up) batteries in the winter. Downside is that although it may only be needed in short periods, the cost per kWh is high. The small generators supplied locally give from 1,5 to 2,5 kWh per litre of petrol. Which means they exploit only a fraction of the energy contained in the fuel.

The good news is that modern installations, good insulation and some clever solutions, makes self-sufficiency possible. But more important, it certainly opens up for reducing both carbon footprint and grid reliance considerably even in traditional on-grid houses.

ok
[Jan 24, 2016 11:59:26 AM] Show Printable Version of Post    View Member Profile    Send Private Message    Hidden to Guest [Link] Report threatening or abusive post: please login first  Go to top 
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