Heating with wood pellets: the question to ask before choosing this method of heating?
Problem of hot water with the pellet boiler or wood
The preparation of domestic hot water (simply called ECS thereafter) is a problem completely (or almost) independent of the problem of sizing the heating.
Indeed: a boiler must run for the heating 4 to 8 months (depending on the region and the behavior of the inhabitants) in the year when it must provide constantly DHW. Therefore, the boiler can not be "theoretically" cut off during the summer months (just as with fuel oil), it will simply operate at reduced load. As we have seen, this may regulatory issues on a wood boiler (Acceptable on a pellet boiler but quasiement incompatible with a wood boiler).
Over the year, the ECS energy needs are usually for families and average house about 20% heating needs.
Also, generally, the pellet boilers have no integrated water heater. We must therefore prepare the ECS apart.
Some boilers have a "summer" function. The boiler only switches on the DHW circulator and regulates the power on the minium. If this makes it possible not to consume at all another source of energy for DHW, the efficiency of the boiler is greatly degraded, which does not seem very wise.
So what are the possible solutions for DHW all year so with a pellet boiler without overeating and clog its boiler summer? Here are 3 possible solutions: electric, wood and electric, the best solar-wood-electric.
A completely independent electric DHW
Using electricity to heat (even ECS) is not very economical overall (it is economical and "ecological" in France because of the cheap nuclear kWh and which rejects little CO2 but it is everything) but if the rest of your house is heated green, it can be an interesting economic compromise.
The solution is to make a completely independent DHW circuit of the heating circuit.
Power consumption due to the ECS average household is between 2000 and 4000 kWh / year, which corresponds with an electric kWh 0.1 euros (including subscription) to an invoice between 200 and 400 € per year if you have bihoraire is even better.
For information, a shower uses about 2 kWh.
Practical example: if you consume 4000 kWh per year for ECS, financially (bill of about € 400) is granulated 2T energetically but this only represents approximately 0.8 T (4000 / 5 800 = kg). Electric heat is 2.5 (2 / 0.8) times more expensive than heating pellets.
This electricity bill is therefore important for an average home that would consume 4 tons of pellets approximately. Economically without electric heating ECS, this would allow to have 1,2 Tons (2-0.8 = 1,2) of Pellets "free" per year. In other words: to heat one year free on 5 approximately.
But the electrical ECS is the solution that costs the least to investment: an electric ball to 100 300 costs € while a dual-energy ball costs about 5 times.
A dual-energy water heater
This is a compromise solution permettrant not use electricity when the boiler is running.
A coil pass inside the flask with water from the boiler. The ball is a radiator again, but with a separate circuit other radiators and a specific management (already provided in most boiler control). The ball also has an electric heater for summer periods or it is not advisable to operate the boiler because of the low power required for the preparation of the ECS (see sizing problem).
This solution is very criticized by professionals say it is better to burn the granulated as electricity, given the low yield in summer, this is not necessarily true.
practical example: if your boiler is cut 6 monthly (compromised) this saves about 50% on your ECS electricity bill. If we take up the reasoning and figures above, do not use any electrical supplement, would allow "just" to gain 1 year of heating every 10 years.
This solution therefore seems the best compromise price investment but environmentally, the best solution is to use either pellets or electricity in summer when the sun shines! We think obviously with the use of solar energy!
The Best of a storage tank tri-energy: wood-solar-electricity
The wood-solar compromise is, for us, the best solution both in terms of raw energy and in terms of annual heating budget but it is one that costs, of course, also the most expensive investment.
(Personnelement it is this solution we have, as you can see on this page: Solar wood pattern for floor heating and DHW.)
The tri-energy term is a bit unfair because if your plant is sized electricity should not be used for anything. Indeed, the solar courverture up 80% of your ECS needs. The 20% being provided by the timber in winter. Electricity should be used for less than 10% of requirements.
For example on our installation (see Solar wood pattern for floor heating and DHW) we have an electrical resistance but it is not wired and we obviously never count the cabler (it serves as a "plug" see photos).
Technologically it is like a normal boiler ball to the difference that an additional coil was added solar.
In winter: most of the ECS produced by the boiler.
In summer most of the ECS produced by the sun and the complement (low) by electric.
This solution is the best compromise in terms of pollutant discharge and heating budget but investment is heavy (expect to 30 35 000 to € 8m² panels and wood boiler or excluding bonuses tax credit) But ultimately this is a much better compromise econological a heat pump where prices can be much higher and that the maintenance costs for the use and life are worst!
Yet it is the heat pump has the wind in its sails because such advertising campaigns carried out by EDF. We believe that the disappointments related to this energy (falsely called renewable geothermal) Will soon be very large among users (maintenance costs, electricity consumption and life) ... Also use a heat pump is to develop and renew the nuclear: it is therefore environmentally friendly than paper trading.
General conclusion of the case: wood pellets, compromise econological fossil fuels!.
Wood pellets is a compromise between the econological heating wood logs and heating fossil fuels: granules provide ease of use that the logs will not probably ever make.
Obviously this at a cost: the investment but also to use.
Indeed, a granulated kWh delivered in bulk costs about € 200 / 5000 0.04kWh = € kWh while a wooden logs about costs (€ 60 in the dry beech cubic meter): € 60 / 2000 0.03kWh = €. The bulk Pellet is 33% more expensive than the buche (€ 60 and the cubic meter is already a high price), however this difference was offset by a unit of yield pellets generally higher than logs appliances.
Wood pellets is an economical and environmentally friendly way of heating (no binder is used, the granules take by fritage ie by internal pressure).
This heating method is a promising future conditions as the pellet is reliable sourcing (limited resource nonetheless) and does not line (too) the prices on oil. See : What future for the price of wood pellets?
The pellets are not a panacea but a very good compromise for those who dare to invest for the future.
Indeed, the field of wood waste would not, far from it, to heat all the French with granulated.
The energy future is made of diversified solutions and especially energy savings!
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