Heating a Farmhouse with a Wood Chip Boiler Biomass Heater - Taking you through from hedge to hearth.

This is a very interesting alternative energy project in that although it is used to heat an individual dwelling, in this case a farmhouse, it actually lies at the heart of what future energy conversion may be all about. There is a growing sense that energy and food production needs to be based around small communities.

Turning back the Clock

A few kilometres away from us is an organic dairy farm with a fine head of rare breed Normandy cows and from where we get our raw milk, cream, cider, honey, chicken grain and straw. The layout of the farm is the same as one sees in most parts of France, the buildings constructed mainly from locally sourced stone and clay, the extraction of the stone at the time of construction resulting in the formation of a large duck pond. On one side of the pool is the bread oven, still used to this day.The farm, as with our own house, has due to its its construction, a high thermal mass which makes the building warm in Winter and cool in Summer. Traditionally these farms had large open fireplaces upon which huge logs would be placed both for cooking and heating. These fires were fed from timber grown on the farm, and were highly inefficient at around 15%. 

Going backwards to go forwards

The fields surrounding the farm are divided with hedges of deciduous wood. The hedges are trimmed every 15 years and the wood is used for fuel. This cycle has been going on for centuries, maintaining the hedgerows being an essential part of the farm calendar. Traditionally, the bigger branches were cut or split into logs for the fire and the thinner twigs would be collected, tied into bundles (faggots) which could be used in the bread oven. Over the last 80 years or so this latter use has become almost obsolete resulting in most farmers/landowners burning these smaller twigs in the fields where they were cut. This amounts to about one third of the total amount of combustible material being wasted.

The solution Michael and Lydie have adopted is to heat their large farm house using a wood chip boiler, the chips are produced from ALL of the hedge trimmings.

In this part of Normandie, there are hedges of a specific type known as bocages. This is an ancient hedging system, whereby the trees were planted on the top of lines of mounded up earth, lined with local stone. Thus, creating raised hedges and obviating the need for livestock fencing. Many of these, sadly have been grubbed out and flattened over the years but others have been preserved. Not only that but some farmers and homesteaders/smallholders are either replanting them or even reinstating the ones that have been destroyed. They are a haven for wild flowers and wildlife and I'm proud to say that we have one which runs along the whole side of our garden.  If you have ever visited Cornwall or Devon, you will have seen similar beautiful hedge types.

Starting at source

On an appointed day a tractor and chipping unit arrive at the land where the wood to be shredded lies beside the trimmed hedge. On the day when we were there, the cut branches from 200m of hedge were converted into chips in one hour and 5 minutes, producing three large trailers full of fuel, sufficient for 18 months of heating of the farmhouse.

Here is a short clip of the chipper in action from our own files. The complete video of the whole system from hedge to hearth, embedded from our Youtube site will be shown at the end of this article.

The chipping machine, and grab are powered via a power take off (pto) from the transporting tractor. The tractor has to be at least 250 HP to supply sufficient power to chip the larger diameter branches. The machine is owned by farmers in the county who contributed to its purchase. Each farmer pays for the running costs incurred to process his wood. Many farmers are also now collectively producing their own biofuel and the tractor can be run on this.

The three fully laden trailers are taken back to the farm and the contents are piled in a hanger to dry. Michael told us it is possible to let the branches dry in the field prior to chipping, producing fuel that may be used immediately. The big disadvantage to this is that the cutters in the machine wear much more rapidly than when chipping 'greener' wood. So, if you have the space, let the easier-to-process chips dry in an open-sided shelter.

After a few days in the shelter, the chip mound starts to naturally heat up, this heat drives the moisture out of the chips such that after 6 months they may be transported up to the rear of the farmhouse where there is a sheltered area next to the 'boiler room'. This means that the recently vacated shelter can then be used to store straw from the summer grain harvest.

The mound can attain temperatures as high as 80º C and theoretically one could extract this heat via a heat exchanger network to supplement the energy needs. The downside to this is that the drying mound would need to be near to the point where the heat is required, the size of the mound would mean another shelter near to the house. Plus any heat exchanger would be susceptible to damage from the machines needed to transfer the dried chips to their final destination. Additionally, there would be a problem of odour. The vapour that is emitted from the pile has a strong fragrance of alcohol.

Goodbye Mr. Chips

Now we come to the final destination of the wood chips, the boiler. 

The dried chips are transferred to a loading bay in this case it is a corrugated iron sheeting silo of 4m³ capacity. Sited in the base of this is a trough in which a screw or auger operates to feed the chips into the boiler. Two spring arms rotate at intervals to sweep chips into the trough. the arms ensure that no voids can form above the trough. The screw feed and the sweeping arms' operation are controlled by the boiler. 

When we were observing it they were actuated for 5 seconds every 30 seconds. The silo holds enough chips for about 3 weeks in the winter months.

The boiler functions automatically, feeding fuel and adjusting the amount of  air needed for optimum combustion. The grate is emptied of ash which is then transferred to the ash box at regular intervals. There is a heat exchanger sited after the combustion chamber the exterior surfaces of which are also automatically cleaned to ensure optimum heat transfer.

The water heated in the exchanger passes into the coils of a 800l hot water tank. This tank provides the domestic hot water and the supply of heating water to the 15 radiators in the house. Thus the boiler is not running all the time and is re-ignited when the hot water tank temperature drops to a pre-determined point. An electrical resistance in the combustion area is used to ignite the wood.

Depending on the quality and type of wood chip being burned the ash box needs to be emptied at best every 3 weeks i.e. every 4m³ of wood chips, inferior wood such as willow will produce more ash that will require the emptying of the box every 10 days.

Pros and Cons

Pros

Using all of the trimmings from the hedges means that there is nearly 50% more fuel for heating and less pollution arising from burning the residue in the fields.

Locally sourced wood means very low fuel miles contributing to environmental impact of system.

Claimed efficiency of over 90% and low emissions means the boiler compares well with gas boilers.

Smokeless.

Ideal for small communities or a group of homesteads seeking a renewable source of heating.

Machines could be powered by Biodiesel to lessen environmental impact further.

Excellent for co-operatives (shared use of chipping equipment).

Cons

Expensive for small independent user if own production of chips desired.

Outbuilding required for bulk storage of chips.  

Cannot function without electricity.

Initial cost of the system - 25,000 Euros, in some countries there is a subsidy for renewable energy start-up but the cost is still steep, in particular if you are also needing to hire the shredder and/or buy in wood for chipping or the chips themselves.

With the ever increasing price and rapid diminishing of resources, any form of heating which can process a renewable, sustainable fuel is worth serious consideration, especially in rural areas.

Our thanks go to Michael and Lydie for the time taken in showing their system to us and to Mother Nature for providing the wood.

Now, if you'd like to, sit back and watch the film:

Thanks for dropping by and please feel free to share this article, comment and/or ask questions and if you'd like to be assured of getting the next post, then sign up to follow this blog.

All the best, Andy

© Andy Colley 2014

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Moving off the Grid - Part Two - Heat Pumps

This will be part of an on-going series  on how and why people choose their source of energy.

Heat Pumps

Heat pumps move ‘heat’ from one point to another. Refrigerators are the most common example of a heat pump system. In our context we are looking at a system that takes heat  energy from a lower temperature body and by mechanical means extracts the heat energy which is then released at a higher temperature. The power  necessary to  enable this is usually electrical and one would normally expect to use 1kW of electrical power to produce 3kW of heat energy. Mostly the source for the heat pump is either the ground or the air but if available in sufficient quantity, water.

  

Practical and beautiful - one of the two lakes on the property.

 The Lady of the Lake – 35 years of heat pumps

Some necessary maintenance - cleaning the exchanger.

Anne-Marie and Jean-Louis have always used heat pumps as their principal source of energy. Their first system was installed when they lived in a riverside property, where they had the right of use not only of the section of river which fronted their property but also an ancient lavoir (communal laundry). This latter gave them ample place in which to accommodate the exchanger. Thirty-five years ago this type of system was so new here in France that the technician who installed the pump didn’t actually have either the belief in, nor knowledge of, the system, just the technical competence to do the work. Anne-Marie and Jean-Louis were so pleased with the system that when they moved, some twenty years ago, to their present home they decided to go with the system again, this time with Jean-Louis building the exchanger himself. Their present system was built from scratch, as they had managed to find a beautiful piece of land with two lakes and a small dwelling, thus giving them scope to build their new home around its heating system. This is perhaps one of the drawbacks with this form of heating in that it is best installed in a newbuild as it requires pipes to be laid within the flooring. However, it is possible to retrofit the system, if one can break through the flooring or use a system of wall-mounted radiators. For Anne-Marie and Jean-Louis, who mostly worked from or at home it has been the perfect solution. The house is kept at a constant  ambient 19°C, except in the bathrooms where additional piping adds to the heating capacity and give a temperature of 23°C.

The constant temperature allows Anne-Marie to grow a whole range of orchids and succulents. A great and avid gardener she uses the heating system to its full advantage when growing some of the many difficult members of these plant families.

This brings us to another consideration with heat pumps, in that they require volumetric calculations for the designs and costings of the whole installation. This could add to the costs of start up, in that you may need to engage a professional to undertake such a study. However, some of the companies selling and installing heat pumps also include a feasibility study within the package – it pays to shop around. All in all this sort of system requires a physical mass, whether a body of water or area of land in which to install the exchanger and a significant initial outlay in time, money and possibly inconvenience for start-up. Anne-Marie and Jean-Louis found and then preserved a beautiful natural environment, which is home to a wide variety of rare and beautiful wildlife. The little grebe, frogs and moorhen paddle about the water lily pads oblivious to the system beneath.

It is also to be considered that the system they have heats a very large volume of living space. Anne-Marie’s original intent was to run a Bed and Breakfast, so their heat pump actually provides a constant 19°C and 23°C in six bedrooms and bathrooms respectively, as the system was also installed in the floorspaces on the upper floors. According to Jean-Louis many people opt for a system which heats just the lower floor and uses radiators above.

The Layout

The lake is some 50m from the house, the feed and return pipes to the exchanger were buried in a trench. Jean-Louis made the 3m x 1m exchanger himself, the tubes arranged in two layers to give a total exchanger area of 6m².



From left to right;-  150l hot water tank, heat pump for heating and hot water and heat pump for heating only.

 





There are two heat pumps in their system the first solely for heating the second for heating and hot water. Recirculating pumps deliver the anti-freeze laden water from the heat exchanger in the lake to the heat pump where some of its heat energy is absorbed prior to returning to the exchanger. The heat from the heat pump is then used to warm the water in the hot water tank, the system from then on being similar to any conventional wet  central heating system. Central heating pumps move the heated water around the matrix of underfloor pipes throughout the house. In the bathrooms the pipes are laid closer together to provide the elevated temperatures required (9cm apart as opposed to 14cm for the rest of the house). The floors act as massive heat sinks, if there is no heating supplied to the system for a 24 hr period, the temperature of the floor drops by only 1°C. The heat pump system is programmed to only run from midnight to 7a.m. thus taking advantage of the lower rate tariff. The financial implication of this is that their total energy bill for this whole house (floor area of 200m²) amounts to 1 350 Euros per annum.

The circulation pumps supplying the water from the exchanger in the lake. A well spaced out system like this is essential for ease of access in case of maintenance.

 
Upstairs feed manifold supplies heating water to the bedrooms and bathrooms. A similar arrangement exists for the ground floor.

Advantages

Reliable heating system furnishing comfortable temperatures throughout a large house.

Low maintenance costs.

No fuel storage necessary.

High level of reliability – few moving parts, no exposure to weather.

Long life expectancy

No pollution provided the integrity of the source loop (heat exchanger in lake) is not compromised.

Disadvantages

Initial capital costs high.

Underfloor installation work is messy in a retro-fit operation.

Electricity supply needed to make system work. Hence you have to have a backup source if there is a possibility of outages and you are still on the grid.
For example, in 1999 the hurricane we had here took down pylons with a resulting 7 day power outage.

Any leak in the heat exchanger will lead to system failure but also to contamination of the water source or land, although use of ecological anti-freeze reduces risk.

Repairs to heat pump requires specialist know-how.

Care has to be taken to ensure no corrosion to pipes and fittings arises from the water in the heating side of  the system.  Jean-Louis has had to change the fittings in the hot water feed manifold to stainless steel due to the acidity of the potable water. He also cites chemical attack from the concrete has caused further deterioration in some fittings.

Jean-Louis and Anne-Marie are so sure that this system is the right one for them that having put their house on the market they have already chosen their new house with a heat pump system as the prime consideration.



 
A heating system which takes full advantage of the landscape  but which has no visible presence within it.    

All the best and thanks for dropping by. Please feel free to share this article, comment and/or ask questions.

Cheers, Andy

© Andy Colley 2014

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Moving off the Grid Part One - Choosing and Using Woodburning Cookers

This will be an on-going series to explore how and why people choose their source of energy.

Why we chose wood

Simple primitive living, when we started our new life in France
Christmas 1999 with our plum pudding cooking on the Godin.

Winter is rapidly approaching and inevitably folks are thinking about heating their homes. When we first arrived here the Spartan heating was a massive granite fireplace, the chimney of which, 1.70m by 0.70m, was blanked off  and a crudely made open-fronted firebox. This had a swan's nest grate sitting in the centre of the hearth, with its flue passing through a hole in the blanking-off plate. There was plenty of wood-fuel left by the previous owner in the outbuildings, so for the first few visits here, this crude open fire became our sole  source of heating and cooking. After all, you can’t carry kitchen appliances on a motorbike. 

When we began to live here permanently and renovate our house, we bought  an insert, a made-for-store Godin from a DIY Superstore and fitted it into the fireplace using blocks, which we then covered with decorative tiling. This looked like a Swedish ceramic stove but the output fuel-to-heat was poor and we were still reluctantly using an electric hot plate and mini cooker. After having returned the malfunctioning hotplate to the store for the 9th time, we decided enough was enough. We therefore, began to research woodburning cookers as a possible heat and cooking source. By now we had fully insulated the bare stone of our kitchen with hemp and lime and were not really wanting to break through this to install water pipes, so we went for a cooker without the advantage of a wraparound boiler. We also wanted something with glass windows so we could check on the cooking and ;have the cheering effect of the flames. Firewood is plentiful here, although year by year the price rises significantly. However, we are neither of us happy with burning magnificent oaks and beeches and we realised we could easily collect a supply of pallet wood to keep us going throughout the year. To this end our heating bill for the past three years has been zero.

Using the top of the cooker to heat water, combining this with a solar shower bag in summer and the creation of our own bicycle-powered washing machine, means we are now consuming 85 kWh of electricity every month at a cost of around 7 Euros. We have therefore, reached the point where we should quit the Grid but our house is on the market and unfortunately this has to be a consideration.

So what does our wood burning cooker do for us?

Heats all our hot water,
Cooks all our food
Dries fruit, flowers, vegetables and herbs
Dries clothes

Heats an iron

What electrical appliances did we get rid of?

Hot plate
Mini oven
Toaster
Kettle
Bathroom heater
200 litre immersion heater
hair dryer
iron

Our woodburner is not recommended by the manufacturer as a pallet-burner but some makers do promote this viz., Esse. The only problem we have found is that the flueways within the cooker need clearing of soot twice a year instead of annually when the chimney liner is swept. We also now have the little Godin stove (seen in the above photo) in our sitting room and this also heats the bedroom above it.

How to chose a Wood-burner

Our woodburning cooker with the now rarely-used insert.

We chose a Lincar, which was made by a company which had started up in business as a manufacturer of wood-burning cookers and then gone into the manufacture of wood-stoves. Most firms we looked at had started with stoves and then gone into wood-cookers, we also found that often they did not manufacture the cookers they sold. It is very important to check the labels on the back of wood-cookers so as to ascertain who makes them and where. This way you can check the full specs, designs and prices at source. The firm, we chose had an extra commendation for us, in that it also made cookers for the Catering Industry. We bought it over the internet, which was worrying, as we had no prior experience in this. It was also impossible to find a showroom nearer than the Italian border where we could actually see the cooker. Another problem was, that in 2008, when we bought the cooker there were very limited reviews of wood-cookers on the internet. However, the company we bought ours through was a small family concern and the person we dealt with had excellent technical knowledge and we had managed to build up quite a rapport with her before we finally bought it. She was also able to provide good quality stove piping direct from the factory and free delivery of the cooker from Italy to France. Hey, we even got a free oven mitt!

Combined with buying our wood-stove the most important thing we did was to fully insulate the house. How we did this with ecological materials is the next chapter of this blog. I will also be writing a piece on how we sourced and made our bicycle washing machine.

What happens in Summer?

 In the hotter months we still use the wood-cooker but only at meal times. Having espoused a French way of life we have a main cooked meal at lunch-time and a cooked meal in the evening, we also have a cooked breakfast. To provide hot water throughout the day I constructed a pallet wood hay box which keeps the water hot for the hours between lighting the cooker. To heat up a kettle we also use a home-made rocket stove. I found the information how to make one of these on Youtube but I have since found that the wood-gas burner, which you can make from similar recycled materials is more efficient but I have yet to make one and verify this.



This image shows our hay box in construction, I completed it with a pallet wood finish to hold in the hay and an insulated lid. Within the box water will keep hot for 4 hours and stay warm for up to 8 hours. This box can also be found as a Victorian cooking technique in Mrs Beeton's Book of Household Management published in 1875. 

Below are two of our more recent designs for a hay box. The first, a simple cheap and cheerful cardboard one (pictured below) and the second a more sophisticated pallet wood one. There is also a film of our trip to the beach in Winter, where we test both designs!

Factors to consider before you decide what energy requirements you need;

1. Be brutal. Start by cutting consumption, this is easier than creating energy.

2. What are your strengths. i.e., what energy sources are plentiful?

3. What are your needs – heating, cooking, hot water, drying, lighting ……

4. Budget and capital expenditure, including maintenance costs.

5. Personal strengths/skills

Wood is cheaper in large volumes but these will need sawing, carrying and storing. Solar, wind, geothermal and wood are cheaper if you can install your own systems.

6. Continuing education

Ask around, look what other people are installing, also visit Fairs and Salons/Exhibitions on Organic and Alternative Living. There are now more opportunities than ever for residential and day courses on alternative energy

A taste of something better - Guichen (Brittany) Salon Bio 2011 - Organic and Green Living Fair. These types of fairs are held yearly all over Europe.

All the best and thanks for dropping by. If you enjoyed this article feel free to share it, comment and/or ask questions.

Cheers, Andy

© Andy Colley 2014

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