Patent Description:
Nearly all large developed cities in the world have at least two types of energy distribution grids incorporated in their infrastructures: one grid for providing heating and one grid for providing cooling. The grid for providing heating may e.g. be used for providing comfort and/or process heating, and/or hot tap water preparation. The grid for providing cooling may e.g. be used for providing comfort cooling and/or process cooling.

A common grid for providing heating is a gas grid or an electrical grid providing comfort and/or process heating, and/or hot tap water preparation. An alternative grid for providing heating is a district heating grid. The district heating grid is used for providing heated heat transfer fluid, typically in the form of water, to buildings of the city. A centrally placed heating and pumping plant is used for heating and distributing the heated heat transfer fluid. The heated heat transfer fluid is delivered to the buildings via one or more feed conduits and is returned to the heating and pumping plant via one or more return conduits. Locally at a building, heat from the heated heat transfer fluid is extracted via a district heating substation comprising a heat exchanger.

A common grid for providing cooling is the electrical grid. The electricity may e.g. be used for running refrigerators or freezers or for running air conditioners for providing comfort cooling. An alternative grid for providing cooling is a district cooling grid. The district cooling grid is used for providing cooled heat transfer fluid, typically in the form of water, to buildings of the city. A centrally placed cooling and pumping plant is used for cooling and distributing the thus cooled heat transfer fluid. The cooled heat transfer fluid is delivered to the buildings via one or more feed conduits and is returned to the cooling and pumping plant via one or more return conduits. Locally at a building, cold from the cooled heat transfer fluid is extracted via a heat pump.

The use of energy for heating and/or cooling is steadily increasing, influencing the environment negatively. By improving utilization of the energy distributed in the energy distribution grids, negative influences on the environment may be reduced. Hence, there is a need for improving utilization of the energy distributed in energy distribution grids, including existing grids. Provision of heating/cooling also requires huge investments when it comes to engineering projects and there is a constant strive to cut the costs. Hence, there is a need for improvements in how to provide sustainable solutions to heating and cooling of a city.

In <CIT> a closed loop heating system is disclosed. The closed loop heating system comprises at least one closed fluid circuit, at least one thermal energy receiving unit and at least one thermal energy releasing unit. The closed loop heating system also comprises a heat pump, transferring thermal energy from at least one first part of said fluid circuit to at least one second part of said fluid circuit.

In <CIT> a district thermal energy network is disclosed. The district thermal energy network interconnects a plurality of thermal loads such as buildings having heating and cooling systems. The network has an energy unit, which may be a geothermal, solar, nuclear, hydro-electric or heat pump unit or a boiler, hot water tank or CHP system. The energy unit is capable of operating as a heat source or a heat sink. The network also has a primary circuit having an upstream flow line and a downstream return line that includes a primary pump to deliver working fluid from the energy unit along the circuit. Each of the thermal loads has a respective user circuit connected to the primary circuit by a respective connection. A switchable valve system for each thermal load selectively connects the user circuit to the primary circuit in a selected working fluid direction along the connection so that the primary circuit can selectively function as a heat source or a heat sink for the user circuit.

It is an object of the present invention to solve at least some of the problems mentioned above.

A method for distributing energy to a plurality of buildings is provided. The method comprises: exchanging, at a central heat exchanger, heat from an incoming flow of district heat transfer fluid of a district feed conduit in a district heating grid, the incoming flow of district heat transfer fluid having a first temperature in the range of <NUM>-<NUM>, to an outgoing flow of local heat transfer fluid in a local feed conduit of a local energy distributing system, the outgoing flow of local heat transfer fluid having a temperature of <NUM>-<NUM>; and extracting, at a local heating system in each of the plurality of buildings, each local heating system having an inlet connected to the local feed conduit, heat from the local heat transfer fluid flowing in the local feed conduit for providing hot tap water and comfort heating to the respective building.

The method may further comprise circulating a flow of local heat transfer fluid in the local energy distributing system, the local energy distributing system comprising the local feed conduit configured to distribute local heat transfer fluid from the central heat exchanger and a local return conduit configured to distribute local heat transfer fluid to the central heat exchanger.

The method may further comprise: extracting, at a cooling system, heat from a building of the plurality of buildings, the local cooling system having an inlet connected to the outlet of one of the plurality of local heating systems; and distributing the from the building extracted heat to the local heat transfer fluid.

The below mentioned features of the local energy distribution system and/or the energy distribution system, when applicable, apply to this third aspect as well. In order to avoid undue repetition, reference is made to the below.

Further, a local energy distributing system is provided. The local energy distributing system comprises: a local feed conduit; a local return conduit; a central heat exchanger connected to a district heating grid having a district feed conduit for an incoming flow of district heat transfer fluid having a first temperature in the range of <NUM>-<NUM>, and a district return conduit for a return flow of district heat transfer fluid, wherein the central heat exchanger is configured to exchange heat from the incoming flow of district heat transfer fluid to an outgoing flow of local heat transfer fluid in the local feed conduit, the outgoing flow of local heat transfer fluid having a temperature of <NUM>-<NUM>; and a plurality of local heating systems, each having an inlet connected to the local feed conduit and an outlet connected to the local return conduit, wherein each local heating system is configured to provide hot water and/or comfort heating to a building.

By exchanging heat from the incoming flow of district heat transfer fluid to the outgoing flow of local heat transfer fluid in accordance with the above, a cheaper, less advanced and more energy efficient energy distributing system as compared with a traditional district heating system utilizing a district heating grid is achieved. For example, heat transfer losses will be reduced making the local energy distributing system more economical and energy efficient. Moreover, since heat transfer losses will be reduced, due to the relatively low temperature of the local heat transfer fluid distributing the energy in the local energy distribution system, constraints on the use of piping's for the conduits transporting the heat transfer fluid is reduced as compared with a traditional district heating system utilizing a district heating grid. Moreover, by setting the from the central heat exchanger outgoing flow of local heat transfer fluid at the temperature of <NUM>-<NUM> the cooling rate in the local energy distribution system will be reduced as compared with a traditional district heating system utilizing a district heating grid. The local energy distributing system also makes it possible to implement efficient energy distribution solutions in expansion areas where existing district heating grids are weak or difficult to expand. Strengthen or expanding existing district heating grids is both expensive and complicated. Moreover, by reducing the cooling rate of the energy distribution system the flow rate of the heat transfer fluid is reduced. Hence, the overall demand on the pumping in the energy distribution system is reduced. This will further reduce the complexity of the energy distribution system as compared with a traditional district heating system utilizing a district heating grid.

According to theoretical simulations, the a local energy distributing system will over a calendar year absorb approximately <NUM>-<NUM>%, of the total energy being put in to the local energy distributing system, from solar energy, in the form of thermal energy absorbed from the ground surrounding the local feed and return conduits. Further, <NUM>-<NUM>% of the total energy being put in to the local energy distributing system will originate from energy provided by the district heating grid and approximately <NUM>% of the total energy being put in to the local energy distributing system will be electricity power used for driving the local heating systems.

Each of the plurality of local heating systems may be configured to extract heat from local heat transfer fluid entering the local heating system via the inlet and return local heat transfer fluid to the local return conduit via the outlet.

Each of the plurality of local heating systems may be configured to return local heat transfer fluid having a temperature being in the range of -<NUM>-<NUM>. By conducting local heat transfer fluid having a temperature in this temperature range, heat loss to the surroundings may be reduced. Moreover, thermal energy of the surroundings may even be absorbed by the local heat transfer fluid flowing in the local return conduit. The surroundings of the return conduit is typically ground since the return and feed conduits typically is arranged in the ground along the majority of their paths.

The local feed conduit together with the local return conduit may have a heat transfer coefficient greater than <NUM> Watt per meter&Kelvin, W/(mK), when parallel arranged in ground. This value of the heat transfer coefficient is estimated when the local feed and return conduits are parallel arranged within a distance of one meter from each other in ground having an average annual temperature of <NUM> and the arithmetic average temperature of the local feed and return conduits are <NUM>-<NUM>. By this, thermal heat from the surroundings may be picked up by the local feed conduit and/or the local return conduit. Moreover, cheap un-insulated plastic pipes may be used for the local feed conduit and/or the local return conduit. Moreover, thermal energy of the surroundings may easily be absorbed by the local heat transfer fluid flowing in the local return conduit.

At least some of the plurality of local heating systems may comprises a local circulation pump connected between the inlet and the outlet of the respective local heating system for circulating local heat transfer fluid in the local feed and return conduits. A system with distribute pumping of the local heat transfer fluid are thus provided. Such a system is less vulnerable. This since upon failure in one or more of the local circulation pumps the rest of the system will still be operational. Moreover, by distributing the pumping over the plurality of local circulation pumps smaller and cheaper circulation pumps may be utilized.

The local energy distributing system may further comprise a central circulation pump configured to circulate the fluid in the local feed and return conduits. The central circulation pump may be used to provide a base pressure in the local energy distribution system; this will reduce the pumping work of the local circulation pumps. Alternatively, or in combination, by using the central circulation pump the installation in some or all of the buildings may be simplified since the central circulation pump may be used instead of local circulation pumps. Instead of local circulation pumps in the buildings check valves may be used for regulating the flow within the local heating system(s).

Each local heating system may comprise a heat emitter and a local heat pump.

The central heat exchanger may be configured to exchange heat such that the district heat transfer fluid returned to the district return conduit is having a temperature of <NUM>-<NUM>, preferably <NUM>-<NUM>. By returning district heat transfer fluid of this low temperature the cooling performed in the central heat exchanger <NUM> can be as great as approx <NUM> (depending of the temperature of the incoming district heat transfer fluid feed through the district feed conduit). This high degree of cooling performed in the central heat exchanger will reduce the heat losses in the district heating grid. Moreover, it will reduce the degree of pumping needed in the district heating grid.

The local energy distributing system may further comprise one or more local cooling systems having an inlet connected to the outlet of one of the plurality of local heating systems, wherein the one or more local cooling systems are configured to extract heat from a building. By this a combined heating and cooling system is provided. Moreover, comfort heating and comfort cooling is provided at the same time in a simple and cost-effective manner using only one of energy distribution grid.

The one or more local cooling systems may comprise a cooler and a cooling heat exchanger.

An energy distributing system is provided. The energy distributing system comprises: a district heating grid having a district feed conduit for an incoming flow of district heat transfer fluid having a first temperature in the range of <NUM>-<NUM>, and a district return conduit for a return flow of district heat transfer fluid; and a local energy distributing system according to the above.

The energy distributing system may further comprise a central heat production plant connected to the district heating grid for providing heat to the district heating grid.

The energy distributing system may further comprise a plurality of district heating substations, wherein each district heating substation is configured to provide hot tap water and/or comfort heating to a building.

The above mentioned features of the local energy distribution system, when applicable, apply to this second aspect as well. In order to avoid undue repetition, reference is made to the above.

Hence, it is to be understood that this invention is not limited to the particular component parts of the device described or steps of the methods described as such device and method may vary.

These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiments of the invention. The figures are provided to illustrate the general structures of embodiments of the present invention.

In connection with <FIG> an energy distribution system <NUM> will be discussed. The energy distribution system <NUM> comprises a district heating grid <NUM> and a local energy distributing system <NUM>. The local energy distributing system <NUM> is connected to the district heating grid <NUM> via a central heat exchanger <NUM>.

The district heating grid <NUM> is formed by one or several hydraulic networks configured to deliver district heat transfer fluid to district heating substations <NUM> which are arranged in buildings <NUM> such as office buildings, business premises, residential homes and factories in need for heating. A typically district heating substation <NUM> comprises a heat exchanger. A typical district heating grid <NUM> comprises a central heat production plant <NUM> which heats the district heat transfer fluid. The central heat production plant <NUM> may by way of example be a district heating plant. The heated district heat transfer fluid is transported via one or more district feed conduits <NUM> forming part of a conduit net work to distributed district heating substations <NUM> which are arranged in the buildings <NUM>. It goes without saying that one and the same building <NUM> may comprise several district heating substations <NUM>. The district heating substations <NUM> are configured to provide comfort heating and/or hot tap water to the respective building <NUM>.

When the heat of the district heat transfer fluid is consumed in the district heating substations <NUM> the temperature of the district heat transfer fluid is lowered and the thus cooled district heat transfer fluid is returned to the central heat production plant <NUM> via one or more district return conduits12 forming part of the conduit net work.

District heating grids <NUM> are used to satisfy comfort heating demands and/or hot tap water demands. The district heat transfer fluid is typically water. The temperature of the district heat transfer fluid in the one or more district feed conduits <NUM> is typically between <NUM>-<NUM>. The return temperature in the one or more district return conduits12 is typically between <NUM>-<NUM>.

The driving pressure difference between district feed conduits <NUM> and district return conduits <NUM> of the hydraulic network always creates a so called "pressure cone" whereby the pressure in the district feed conduits <NUM> is higher than the pressure in the return conduits <NUM>. This pressure difference circulates the district heat transfer fluid in the hydraulic network between the central heat production plant <NUM> and the district heating substations <NUM>. One or more district grid circulation pumps <NUM> are arranged in the district heating grid <NUM> in order to provide the driving pressure difference.

The district feed conduits <NUM> and the return conduits <NUM> used in the district cooling grid <NUM> are typically made of insulated steel pipes designed for a maximum pressure of <NUM>,<NUM> MPa and maximum temperature of about <NUM>-<NUM>. In this context insulated shall be constued such that the pipes have an extra layer of heat insulating material wrapped around the same. As a non-limiting example, the steel pipes of the district feed conduits <NUM> and the return conduits <NUM> are insulated such that the conduits arranged in parallel in ground have a heat transfer coefficient lower than <NUM> Watt per meter&Kelvin, W/(mK), preferably lower than <NUM> W/(mK). These value of the heat transfer coefficient is estimated when the district feed and return conduits are parallel arranged within a distance of one meter from each other in ground having an average annual temperature of <NUM> and the arithmetic average temperature of the district feed and return conduits of <NUM>-<NUM>.

As indicated above, the local energy distributing system <NUM> is connected to the district heating grid <NUM> via the central heat exchanger <NUM>. Heat exchangers as such are well known in the art and can basically be described as comprising an arrangement of a first circuit circulating a first fluid having a first temperature, and a second circuit circulating a second fluid having a second temperature. The first and second circuits closely abut each other along a respective extension thereof. By the two circuits along an extension closely abutting each other a heat transfer takes place between the first and second fluids. For the central heat exchanger <NUM> the first circuit forms part of the district heating grid <NUM> and the second circuit forms part of a local energy distributing grid 20a. The local energy distributing grid 20a being part of the local energy distributing system <NUM>. The local energy distributing grid 20a comprising a local feed conduit <NUM> and a local return conduit <NUM>. The local energy distributing grid 20a is configured to deliver local heat transfer fluid to local heating systems <NUM> which are arranged in buildings <NUM>, preferably residential homes but also other types of buildings <NUM> such as office buildings, business premises and factories in need for heating.

The central heat exchanger <NUM> is configured to exchange heat from an, via the district feed circuit <NUM>, incoming flow of district heat transfer fluid to an outgoing flow of local heat transfer fluid in the local feed conduit <NUM>. The central heat exchanger <NUM> is configured to exchange heat such that the outgoing flow of local heat transfer fluid has a temperature of <NUM>-<NUM>. Further, the central heat exchanger <NUM> may be configured to exchange heat such that the district heat transfer fluid returned to the return conduit is having a temperature of <NUM>-<NUM>. By returning district heat transfer fluid of this low temperature the cooling performed in the central heat exchanger <NUM> can be as great as approx <NUM> (depending of the temperature of the incoming district heat transfer fluid feed through the district feed conduit). This high degree of cooling performed in the central heat exchanger will reduce the heat losses in the district heating grid. Moreover, it will reduce the degree of pumping needed in the district heating grid.

Hence, the local energy distributing system <NUM> comprises a plurality of local heating systems <NUM>. With reference to <FIG> a local heating system <NUM> will be discussed in more detail.

The local heating system <NUM> comprises a heat pump <NUM> and a heat emitter <NUM>. The heat emitter <NUM> is connected to the local energy distributing grid 20a via the heat pump <NUM>. The local heating system <NUM> is configured to, via the heat emitter <NUM> and the local heat pump <NUM>, provide hot tap water and/or comfort heating to a respective building <NUM>. The local heat pump <NUM> has an inlet <NUM> connected to the local feed conduit <NUM> and an outlet <NUM> connected to the local return conduit <NUM>. In this context the term "inlet of the heat pump" is to be interpreted as the inlet via which the heat pump is fed with local heat transfer fluid from the local energy distributing grid 20a. Likewise, the term "outlet of the heat pump" is to be interpreted as the outlet via which the heat pump returns local heat transfer fluid to the local energy distributing grid 20a.

Heat pumps as such, are well known in the art and basically comprise a closed circuit in which brine is circulated between a first heat exchanger and a second heat exchanger. The first heat exchanger has an inlet and an outlet, in this case the inlet <NUM> and the outlet <NUM> of the local heat pump <NUM>, via which the local heat pump <NUM> is connected to a first circuit circulating a flow of a first fluid, in this case the local heat transfer fluid of the local energy distributing grid 20a. Likewise, the second heat exchanger has an inlet and an outlet via which the local heat pump <NUM> is connected to a second circuit circulating a flow of a second fluid, in this case a heating fluid of the heat emitter <NUM>. The heating fluid of the heat emitter <NUM> is typically water, although it is to be understood that other fluids or mixture of fluids may be used. Some non-limiting examples are ammonia, anti-freezing liquids (such as glycol), oils and alcohols. A non-limiting example of a mixture is water with an anti-freezing agent, such as glycol, added thereto.

Since the flow of local heat transfer fluid in the local feed conduit is having a temperature of <NUM>-<NUM> the input temperature to the local heat pump <NUM> is in the same temperature range. The local heating system <NUM> is configured to extract heat from local heat transfer fluid entering the local heat pump <NUM> via the inlet <NUM> and return local heat transfer fluid to the local return conduit <NUM> via the outlet <NUM>. The local heating system <NUM> is configured to return local heat transfer fluid having a temperature being in the range of -<NUM>-<NUM>.

The local heating system <NUM> may further comprises a local circulation pump <NUM>. In the in <FIG> shown embodiment the local circulation pump <NUM> is arranged in the outlet <NUM> of the local heat pump <NUM>. However, the local circulation pump <NUM> may alternatively be arranged in the inlet <NUM> of the local heat pump <NUM>. Hence, the local circulation pump <NUM> is connected between the inlet <NUM> and the outlet <NUM> of the local heating system <NUM>. The local circulation pump <NUM> is configured to circulate local heat transfer fluid in the local feed and return conduits <NUM>, <NUM>. The local circulation pump <NUM> is configured to overcome the pressure difference between the local return conduit <NUM> and the local feed conduit <NUM>. The local circulation pump <NUM> is further configured to regulate the flow of local heat transfer fluid flowing through the local heat pump <NUM>. By regulating the flow of cooling fluid trough the local heat pump <NUM>, and at the same time optionally control the operation of the local heat pump <NUM>, the temperature of the local heat transfer fluid outputted from the local heat pump <NUM> may be controlled.

Hence, some or all of the plurality of local heating systems <NUM> of the local energy distributing system <NUM> may comprise a local circulation pump <NUM> for circulating local heat transfer fluid in the local feed and return conduits <NUM>, <NUM>. Additionally or in combination with the plurality of local circulation pumps <NUM>, the local energy distributing system <NUM> may comprise a central circulation pump <NUM> configured to circulate the fluid in the local feed and return conduits <NUM>, <NUM>.

The local heat pump <NUM> may be controlled by a controller <NUM>. The controller <NUM> may control the local heat pump <NUM> based on data pertaining to heating demands of the heat emitter <NUM> and/or data pertaining to the temperature of the local heat transfer fluid in the outlet <NUM> of the local heat pump <NUM>. Data pertaining to heating demands of the heat emitter <NUM> may be determined by means of a heat demand sensor <NUM> connected to the heat emitter <NUM>. Data pertaining to the temperature of the local heat transfer fluid in the outlet <NUM> of the heat pump <NUM> may be determined by means of a temperature sensor T1 connected to the outlet <NUM>.

The piping used for the local feed and return conduits <NUM>, <NUM> in the local energy distributing system <NUM> is normally plastic un-insulated piping. In this context un-insulated shall be constued such that the piping does not have an extra layer of heat insulating material wrapped around the same. The piping is typically designed for a maximum pressure of <NUM>-1MPa. The piping is further typically designed for maximum temperature of about <NUM>. Further, the local feed and return conduits <NUM>, <NUM> in the local energy distributing system <NUM> may together have a heat transfer coefficient greater than <NUM> W/(mK) when parallel arranged in ground. As mentioned above, this value of the heat transfer coefficient is estimated when the local feed and return conduits are parallel arranged within a distance of one meter from each other in ground having an average annual temperature of <NUM> and the arithmetic average temperature of the local feed and return conduits are <NUM>-<NUM>.

The local heat transfer fluid, and hence energy carrier, is typically water, although it is to be understood that other fluids or mixture of fluids may be used. Some non-limiting examples are ammonia, anti-freezing liquids (such as glycol), oils and alcohols. A non-limiting example of a mixture is water with an anti-freezing agent, such as glycol, added thereto. According to a preferred embodiment the local heat transfer fluid is a mixture of water and an anti-freezing agent, such as glycol. This will allow for the local heat transfer fluid to have temperatures below <NUM>. Providing a local heat transfer fluid having freezing point below <NUM>, preferably below -<NUM>, makes it possible to conduct local heat transfer fluid in the return conduit that may absorb heat from the surroundings, e.g. the ground surrounding the return conduit, even if the surroundings have a temperature close to <NUM>.

The local energy distributing system may further comprise one or more local cooling systems <NUM>. With reference to <FIG> a local cooling system <NUM> will be discussed in more detail. It shall be noted that the local cooling system <NUM> is arranged in connection with a local heating system <NUM>. The local heating system <NUM> is a local heating system <NUM> as has been discussed above. In order to avoid undue repetition with regard to the local heating system <NUM> reference is made to the above.

Each cooling system <NUM> comprises a cooler <NUM> and a cooling heat exchanger <NUM>. Coolers <NUM> are as such well known in the art and may be used e.g. for comfort cooling in buildings such as office buildings, business premises, residential homes and factories in need for cooling. The cooler <NUM> is connected to the local energy distributing grid 20a via the cooling heat exchanger <NUM>. The local cooling system <NUM> is configured to, via the cooler <NUM> and the cooling heat exchanger <NUM>, provide comfort cooling to a respective building <NUM>. Hence, the local cooling system <NUM> is configured to extract heat from a building <NUM>.

The cooling heat exchanger <NUM> has an inlet <NUM> connected to the outlet <NUM> of one of the plurality of local heating systems <NUM>. The cooling heat exchanger <NUM> further has an outlet <NUM> connected to the local return conduit <NUM> of the local energy distributing grid 20a. In this context the term "inlet of the heat exchanger" is to be interpreted as the inlet via which the heat exchanger is fed with local heat transfer fluid from the local energy distributing grid 20a. Likewise, the term "outlet of the heat exchanger" is to be interpreted as the outlet via which the heat exchanger returns local heat transfer fluid to the local energy distributing grid 20a.

As mentioned above, the cooler <NUM> is connected to the local energy distributing grid 20a via the cooling heat exchanger <NUM>. With reference to the above, heat exchangers as such are well known in the art and can basically be described as comprising an arrangement of a first closed circuit circulating a first fluid having a first temperature, and a second closed circuit circulating a second fluid having a second temperature. By the two circuits along an extension closely abutting each other a heat transfer takes place between the two fluids. In the local cooling system <NUM>, the first circuit is locally arranged in the building <NUM> and the second circuit forms part of the local energy distributing grid 20a. Coolers to be used for local cooling systems of buildings are typically situated in air ducts of ventilation or distributed through fan-driven air-coil collectors or ceiling mounted cooling batteries in individual spaces of a building.

The local cooling system <NUM> may further comprises a flow valve <NUM>. The flow valve <NUM> is configured to regulate the flow of local heat transfer fluid flowing through the cooling heat exchanger <NUM>. By regulating the flow of local heat transfer fluid trough the cooling heat exchanger <NUM>, and at the same time optionally control the operation of the cooling heat exchanger <NUM>, the temperature of the local heat transfer fluid outputted from the cooling heat exchanger <NUM> may be controlled. The flow valve <NUM> may be controlled by a second controller <NUM>. The second controller <NUM> may control the flow valve <NUM> based on data pertaining to cooling demands of the cooler <NUM> and/or data pertaining to the temperature of the local heat transfer fluid in the outlet <NUM> of the local heating system <NUM> and/or data pertaining to the temperature of the local heat transfer fluid in the outlet <NUM> of the local cooling system <NUM>. Data pertaining to cooling demands of the cooler <NUM> may be determined by means of a cooling demand sensor <NUM> connected to the cooler <NUM>. Data pertaining to the temperature of the heat transfer fluid in the outlet <NUM> of the local heating system <NUM> may be determined by means of the temperature sensor T1 discussed above. Data pertaining to the temperature of the local heat transfer fluid in the outlet <NUM> of the local cooling system <NUM> may be determined by means of a temperature sensor T2 connected to the outlet <NUM>.

With reference to <FIG> a method for distributing energy to a plurality of buildings <NUM> will be discussed. The method comprises one or more of the following acts. The acts may be performed in any order suitable.

Exchanging S400, at the central heat exchanger <NUM>, heat from the incoming flow of district heat transfer fluid of the district feed conduit <NUM> in the district heating grid <NUM> to an outgoing flow of local heat transfer fluid in the local feed conduit <NUM> of the local energy distributing system <NUM>.

Circulating S402 a flow of local heat transfer fluid in the local energy distributing system <NUM>, the local energy distributing system <NUM> comprising the local feed conduit <NUM> configured to distribute local heat transfer fluid from the central heat exchanger <NUM> and the local return conduit <NUM> configured to distribute local heat transfer fluid to the central heat exchanger <NUM>. The act of circulating S402 is preferably performed using a plurality the local circulation pumps <NUM>. Alternatively, or in combination, the act of circulating S404 may be performed using the central circulation pump <NUM>.

Extracting S404, at the local heating system <NUM> in each of the plurality of buildings <NUM> heat from the local heat transfer fluid flowing in the local feed conduit <NUM> for providing hot tap water and/or comfort heating to the respective building <NUM>.

Extracting S406, at a cooling system <NUM>, heat from one of the plurality of buildings <NUM>.

Distributing S408 the from the building <NUM> extracted heat to the local heat transfer fluid. The heat may be distributed to the local heat transfer fluid of the local return conduit <NUM>. Alternatively, or in combination, the heat may be distributed to the local heat transfer fluid of the local feed conduit <NUM>.

For example, in the in <FIG> shown embodiment the flow valve <NUM> is arranged in the outlet <NUM> of the cooling heat exchanger <NUM>. However, the flow valve <NUM> may alternatively be arranged in the inlet <NUM> of the cooling heat exchanger <NUM>.

In the in <FIG> shown embodiment the first and second controllers <NUM>, <NUM> are illustrated as separate controllers. However, alternatively the first and second controllers <NUM>, <NUM> may be combined into a single controller.

In the in <FIG> shown embodiment the central circulation pump <NUM> is illustrated to be located at the inlet to the central heat exchanger. However, it is realized that the central circulation pump <NUM> may be arranged at any position within the local energy distributing grid 20a.

In the in <FIG> shown embodiment the local heat transfer fluid exiting the local cooling system <NUM> via the outlet <NUM> of the cooling heat exchanger <NUM> is feed to the local return conduit <NUM>. However, alternatively or in combination, the local heat transfer fluid exiting the local cooling system <NUM> via the outlet <NUM> may be feed to the local feed conduit <NUM>. Feeding of the local heat transfer fluid exiting the local cooling system <NUM> via the outlet <NUM> may be controlled by the second controller <NUM>. The control of the feeding of the local heat transfer fluid exiting the local cooling system <NUM> via the outlet <NUM> to the local feed and/or return conduits <NUM>, <NUM> may be based on the temperature monitored by the second sensor T2.

Further, the heating and cooling systems have been exemplified with one, respectively two temperature sensors T1 and T1-T2, respectively. It is to be understood that the number of temperature sensors and their positions may change. It is also to be understood that additional sensors may be introduced to the system depending on desired input to the first and second controllers <NUM>, <NUM> and desired complexity. Especially, the first and second controllers <NUM>, <NUM> may be arranged to communicate with the heat emitters <NUM> and/or coolers <NUM> locally arranged in the buildings <NUM> to take local settings into account.

Claim 1:
A method for distributing energy to a plurality of buildings (<NUM>), the method comprising:
exchanging, at a central heat exchanger (<NUM>), heat from an incoming flow of district heat transfer fluid of a district feed conduit (<NUM>) in a district heating grid (<NUM>), the incoming flow of district heat transfer fluid having a first temperature in the range of <NUM>-<NUM>, to an outgoing flow of local heat transfer fluid in a local feed conduit (<NUM>) of a local energy distributing system (<NUM>), the outgoing flow of local heat transfer fluid having a temperature of <NUM>-<NUM>; and
extracting, at a local heating system (<NUM>) in each of the plurality of buildings (<NUM>), each local heating system (<NUM>) having an inlet (<NUM>) connected to the local feed conduit (<NUM>), heat from the local heat transfer fluid flowing in the local feed conduit (<NUM>) for providing hot tap water and comfort heating to the respective building (<NUM>).