Projet de réseau de chaleur : la checklist britannique

https://i0.wp.com/www.idea.gov.uk/idk/site-idk2/images/f/logo.gifLe centre de ressources mis en place par le gouvernement britannique à destination des collectivités locales propose une checklist indiquant en une vingtaine de points synthétiques les principales questions et points de vigilance liés à la mise en place d’un projet de réseau de chaleur. Si on fait abstraction de la 1ère partie relative aux autorisations administratives, qui sont propres à chaque pays, le reste du document est tout à fait applicable aux projets français.

On retrouve ainsi dans ces recommandations de nombreux points régulièrement mis en avant par les acteurs de la filière en France : étude des coûts à long terme ; recherche de combustibles locaux ; recherche d’une demande de chaleur aussi stable que possible sur la journée et sur l’année ; recherche de bâtiments garantissant une demande importante et constante (« anchor loads ») ; sur les quartiers neufs, recherche de bâtiments anciens voisins pouvant être raccordés…

3 études de cas sont également proposées :

General

Scale District heating can work at a range of scales from a singe building up to a city. It is most appropriate at the scale of a large neighbourhood or city. Smaller areas of 200-250 homes can also be viable.At least 55 new dwellings per hectare are necessary for financial viability of a residential only scheme or a heat density of at least 3,000kW per square kilometreYou may need to start with a smaller scheme and allow it to grow over time.
Impact on phasing A large development that is phased over a number of years may need to comply with several versions of Part L of the Building Regulations (see glossary). If district heating is needed for compliance in later phases then economies of scale might mean it is preferable to install a network to serve all phases.
Wayleaves or land purchase Land purchase or wayleaves (see Glossary) may be required if pipes cross land owned by others. Two separate payments may be needed for wayleaves:

  • the owners’ payment: which represents a ‘rent’ for the land used
  • the compensation payable to the occupier for interference with other activities.

These payments are both negotiated.

Energy generation

Space requirements This will depend on the type of generating plant, location and fuel supply.The size needed for a biomass plant room will be larger than for the size needed for gas. This is because space for fuel is needed. This might be equal to the space needed for the generating unit.
Location The energy centre should be located as close to customers as possible to minimise the length of expensive pipe work.
Fuel supply Consideration should be given to fuel supplies, long-term costs, efficiencies and the ability to source the fuel close to customers.
Demand for heat This should be as consistent as possible across a 24-hour period and between seasons. This will allow the plant to run as efficiently as possible.
Sizing the energy centre The boilers or CHP engine should be sized to serve the summer base load so that waste heat is minimised. Additional demand can be met by back-up boilers that are only switched on as necessary.If a thermal store is built into the network then the boiler or generating engine can be sized to meet a greater proportion of demand.

Consideration should be given to whether additional capacity will be needed in future.

Thermal store This works in the same way as a domestic hot water tank and stores excess heat over a 24-hour period or even between seasons.
Efficiency Boilers and generating engines operate most efficiently when there’s a smooth, steady load.

(See also: biomass, energy from waste and CHP)

Distribution

Space requirements Trenches will be needed to accommodate flow and return insulated pipes. Pipes vary in size depending on capacity.In sizing pipes, consideration should be give to whether additional connections will be needed in future.
Development density At least 55 new dwellings per hectare are necessary for financial viability.A recent study from DECC suggests a minimum heat density of 3,000 kW per square kilometre per annum.
Load profiiles Heat demand for buildings of different uses is not evenly distributed across the day or year. Homes generally have a morning and evening peak, while commercial users peak during the day. Winter heat demand is likely to be higher than summer. You should look for a good mix of demand loads.
Mix of uses Heat and CHP engines operate most efficiently when they are run for long periods of time. Consequently, connecting a mix of uses to a district heating network will stabilise the demand profile allowing the system to operate more effectively. With a stable demand profile the boiler or generating engine can be effectively sized and allowed to operate at full efficiency for more of its operational time.
Age of buildings Generally older buildings are less efficient and therefore have a higher heat demand than new buildings. Since a brand-new development may not have sufficient heat demand to justify the expense of a district heating network it may be better to connect new and existing buildings.
Anchor loads Certain buildings, such as hospitals, hotels, swimming pools and civic buildings, have a large demand for heat, which tends to be steadier over 24 hours. These are called anchor loads and connecting these up can provide the starting point for district heating network.
Physical barriers Having to cross physical barriers, such as railways, major highways and waterways, can make district heating pipe work much more expensive and introduce delays in construction.

Energy use

Space requirements Pipe work will be needed to connect each property with the heat main.
Properties will need a heat exchanger (also called a hydraulic interface unit), which can save some space compared to an equivalent boiler unit.
Location The energy centre should be located as close to customers as possible to minimise the length of expensive pipe work.
Fuel supply Consideration should be given to fuel supplies, long-term costs, efficiencies and the ability to source the fuel close to customers.
Demand for heat This should be as consistent as possible across a 24-hour period and between seasons. This will allow the plant to run as efficiently as possible.
Sizing the energy centre The boilers or CHP engine should be sized to serve the summer base load so that waste heat is minimised. Additional demand can be met by back-up boilers that are only switched on as necessary.
If a thermal store is built into the network then the boiler or generating engine can be sized to meet a greater proportion of demand.Consideration should be given to whether additional capacity will be needed in future.
Thermal store Heat use can be measured in a similar way to electricity or gas using a meter or, more cheaply, by simply metering the flow of hot water used. Many old district heating systems were not metered like this, which led to very inefficient use.

Publier un commentaire

Entrez vos coordonnées ci-dessous ou cliquez sur une icône pour vous connecter:

Logo WordPress.com

Vous commentez à l'aide de votre compte WordPress.com. Déconnexion / Changer )

Image Twitter

Vous commentez à l'aide de votre compte Twitter. Déconnexion / Changer )

Photo Facebook

Vous commentez à l'aide de votre compte Facebook. Déconnexion / Changer )

Photo Google+

Vous commentez à l'aide de votre compte Google+. Déconnexion / Changer )

Connexion à %s