- Solar, an astronomical potential
- Wood, an energy at your fingertips and cheap
- Geothermal power, underground power
- Wind power, a big potential
- Heating and domestic hot water: costs and solutions
Heating, producing electricity or hot water... are all needs that renewable energy can cover. The equipment evolves to make the houses more and more autonomous.
France is well endowed with renewable energies: large forest area, geothermal rich basement, sun, powerful wind regimes and a lot of water (rivers, seas and oceans). However, renewables account for less than 16% of final energy consumption and we need to work hard if we want to achievetarget of 23% by 2020.
Solar, an astronomical potential
The energy of the sun can be captured in different ways.
The photovoltaic technology converts solar radiation into electricity using panels installed on roofs or on the ground. The energy produced can be consumed directly, stored in batteries or injected into the distribution network and generate profit. The installation project must take into account various parameters: sunshine rate, orientation of the house, characteristics of the neighborhood and surrounding buildings (possible shading...). In addition to the fluctuations of the sunshine, its output is conditioned by the surface and the maximum power, in watts- or kilowatt-peak (Wc or kWp), installed panels. In France, 1 kWp produces an average of 900 kWh / year of electricity in the north and 1,400 kWh / year in the south.
The Solar Thermal uses specific sensors that transmit the heat of the sun to the water of a storage tank, via a heat transfer fluid running in a closed circuit. For a family of four, there are 2.5 to 5 m2 catchment area in the south and 5 to 7 m2 in the north. The individual solar water heater (Cesi) only provides domestic hot water. The combined solar system (SSC) feeds the central heating and domestic hot water circuits together. It can also heat the water of a swimming pool.
More recently, manufacturers have developed the solar photovoltaic (or aerothermal) that exploits heated air in photovoltaic panels and redistributes heat in the home through a ventilation system. In summer, the device allows you to cool rooms during hot nights.
French innovation, the hybrid solar implements photovoltaic panels which integrate in their box a dispositif of heat recovery. The sensors are connected by two pipes (to and from) to a buffer tank that can serve one central heating circuit and another DHW circuit. The key is a simplified installation and improved efficiency in power generation (up to + 15%).
Wood, an energy at your fingertips and cheap
Of forest and / or agricultural origin, energy wood (or solid biomass) includes the by-products of the wood industry and the recycling of untreated packaging: crates, pallets... forest biomass supplies the logs and remnants of cuts (slash) used to manufacture shredded wood (chips), pellets, compressed logs... Easy to store, these different fuels are nowadays associated with heaters, whose yields from 70 to over 90% minimize pollutant releases into the atmosphere.
The individual wood heating (stove, closed hearth...) has the ability to heat a whole house, if it is designed for permanent use and with adequate power. With a canalizable device, it is possible to heat several rooms, by distribution of hot air. The stoves and the boiling pans can heat the water of a central heating circuit and ensure the production of DHW (domestic hot water). The wood boilers (logs, pellets or chips) see their technical performance evolve. Autonomy progresses on all fronts, automatic versions even rivaling their gas or oil cousins.
Wood is a renewable and economical fuel. Insert, stove and boiler, the range of appliances covers all needs: auxiliary heating, central, supply of domestic hot water... Opposite the Pellematic boilerfed with pellets by suction from a silo (94% yield).
The opinion of the expert *
"Biomass (1) will play a major role in the energy transition... It represents half of the efforts needed to reach the 2020 targets of the authorities in the field of renewable energies... It is an energy that relies on abundant heterogeneous resources and which favors the development of local jobs that can not be relocated... "
* Philippe Gattet, director of studies at Xerfi-Precepta
(1) All organic matter of plant or animal origin (wood, plants, agricultural waste...)
Geothermal power, underground power
In a detached house, we prefer the geothermal energy "very low energy" associated with a heat pump. The calories captured in the soil, with a maximum temperature of 30° C, come from areas of the earth's crust or groundwater located less than 100 m deep.
The most common technique in metropolitan France is the horizontal capture, consisting of a network of tubes in tight loops, buried at a depth of 60 to 120 cm. This principle requires a substantial laying surface: 1.5 to 2 times that of the house to be heated.
Where the terrain is a problem, use is made of vertical capture by probes, with a depth of 80 m max. Two wells of about ten meters deep and 50 meters deep enough to heat 120 m2 livable. But drilling, technically challenging, involves a higher installation cost.
The very low energy geothermal capture horizontal or vertical (1), here by probes, takes advantage of the solar heating of the earth's soil and the waters it traps in its clay or rock layers. A heat pump (2) and one dual energy water heater (3) then feed central heating (4) and sanitary (5).
The thermal sensors (1) Solar System Combined Solar System (SCC) transfer heat from the sun to heat transfer fluid (2) which leads to a buffer tank (3). Coupled with a boiler installed in relief (4), the balloon serves the networks ofhot water (5) and central heating (6).
The Canadian well recovers the calories present in the soil thanks to a thick headed and an air intake (1 and 2) to warm the indoor air. A buried collector pipe (3) feeds a thermodynamic power plant (7) which distributes heated air in winter or cooled in summer in the house (8). The stale air (9) returns to the central unit before being discharged to the outside (10). The system includes a probe (4) and one temperature controller (5).
Wind power, a big potential
France is swept by powerful wind regimes. Thanks to their distribution, the wind turbine fields rotate 80% of the time and provide 4.5% of national electricity consumption, for an installed capacity of 12,500 megawatts in 2017.
The domestic wind turbines, or small wind, represent only a confidential part of the national park. Their generator delivers a very low voltage current (12 or 24 V) which can be stored in batteries to power TBT equipment: alarm, lighting... It is completed by an inverter allowing to obtain 230 V AC. From a power of 90 W to 36 kW, the small wind is conceived mainly in rural area and in isolated sites. The most efficient models can provide punctually the energy needed for the electrical needs of a home. The average investment range varies from € 8,500 to € 15,000 (accessories and installation included). The amortization period is estimated at around fifteen years. If you plan to resell your production to the grid, the 15-year guaranteed redemption prices are capped at 8.2 eurocents per kWh. It is much lower than those of photovoltaic electricity and too low for the operation to be profitable.
Heating and domestic hot water: costs and solutions
A substantial budgetHeating and domestic hot water (DHW) 70% of energy consumption of a house (source: Ministry of Sustainable Development). Prioritizing renewable energies makes it possible to overcome rising prices for fossil fuels, which are becoming increasingly scarce, or electricity from nuclear power, which is not really environmentally friendly, or even makes a profit. For comparison, for the 2016 heating season, French households spent on average 1927 € of fuel oil, 1726 € of electricity, 1415 € of gas (study quelenergie.fr).
To find out more: ademe.fr (practical guide "Choosing your wood heating system").
Wood: logs and pelletsThe wood provides heating best cost (between 4 and 7 € / kWh, source Ademe): boiler, preferably automatic, individual device ducted or with boiler function. If the housing configuration lends itself to it (open loft type), the central layout of a non-ductable stove is an interesting option. Log, pellets or mixed, it is possible to limit storage constraints by adding a decorative pyre or a large pellet tank.
ThermodynamicsThe thermodynamic water heater is a kind of big balloon surmounted by a heat pump. It takes the calories from the air and transfers them, amplified, into the water of its tank. The device can operate at a temperature of 10 to 35° C.
The thermodynamic heating takes up the principle by adapting it to a reversible heat pump. The system can function as a VMC (Air / air heat pump) or by harnessing the energy of the earth (Air / water PAC...) to supply central heating by radiators and / or underfloor heating. Small flat, the power of the installation must correspond to 120\% heating needs of the house. The necessary adaptation of the electric subscription can then result in an additional cost of several hundred euros per year, according to David Bonnet, sales director of the company Technibel.
The solar panelsWell sized and oriented, photovoltaic panels can cover the needs of a household.
The feed-in tariffs per kWh of electricity by EDF, set by the French Energy Regulatory Commission (CRE), are based on the installation of the panels: building integration (IAB), simplified integration (ISB), non-integration into the building (NIB). They remain fixed for 20 years (with an indexation formula based on criteria such as the INSEE index or changes in the cost of living) at the date of the connection request and are decreasing from the lowest to the highest. high installed power. According to the decree of May 9, 2017:
- total resale of electricity produced: 11.36 cts / kWh for an installation with a power of about 100 kWp at 18.48 cts / kWh for a power of less than or equal to 3 kWp.
- consumption: surplus electricity is sold to EDF up to 10 cts / kWh for installations up to 9 kWc and 6 cts / kWh for those up to 100 kWp. The self-consumer receives an investment premium paid over 5 years, decreasing every quarter (edfenr.com/news/profit-incorating-consumption).
Learn more about the price of energies: