Thermal energy network

Abstract

A district energy network interconnecting a plurality of thermal loads and for redistributing thermal energy therebetween, the network comprising: a primary circuit loop for working fluid, at least two thermal loads thermally connected to the primary circuit loop, at least one of the thermal loads being capable of taking heat from the primary circuit loop and at least one of the thermal loads being capable of rejecting heat into the primary circuit loop, an energy centre connected to the loop and capable of acting as a heat source or a heat sink, and a control system adapted to provide to the primary circuit loop a positive or negative thermal input from the energy centre as a balancing thermal input to compensate for net thermal energy lost to or gained from the at least two thermal loads by the primary circuit loop.

1 . A thermal energy network interconnecting a plurality of thermal loads, the network comprising:
 at least one energy unit capable of functioning as a heat source or a heat sink, a primary circuit loop for working fluid connected to the energy unit, the primary circuit loop comprising an upstream outflow line and a downstream return line,   a primary pump for pumping the working fluid around the primary circuit loop successively from an outlet of the energy unit along the upstream outflow line, along the downstream return line and back to an inlet of the energy unit,   
       at least two thermal loads, each thermal load respectively comprising a user circuit loop for working fluid,
 each user circuit loop being connected to the primary circuit loop by a respective working fluid connection at a respective location along the primary circuit loop, and 
 a switchable valve system coupled to each user circuit loop for selectively connecting the user circuit loop to the primary circuit loop in a selected working fluid flow direction within the respective connection so that the primary circuit loop can selectively function as a heat source or a heat sink for the user circuit loop. 
 
     
     
         2 . A thermal energy network according to  claim 1  wherein the primary circuit loop consists of the upstream outflow line and the downstream return line. 
     
     
         3 . A thermal energy network according to  claim 1  wherein the connection comprises:
 a first working fluid line having an inlet connected to the upstream outflow line and an outlet connected to the user circuit loop, 
 a second working fluid line having an inlet connected to the downstream return line and an outlet connected to the user circuit loop, and 
 a third working fluid line having an outlet connected to the upstream outflow line and an inlet connected to the user circuit loop. 
 
     
     
         4 . A thermal energy network according to  claim 3  wherein the switchable valve system is arranged to connect the user circuit loop to either (i) the upstream outflow line by the first working fluid line and the upstream outflow line by the third working fluid line or (ii) the downstream return line by the second working fluid line and the upstream outflow line by the third working fluid line. 
     
     
         5 . A thermal energy network according to  claim 3  further comprising a fourth working fluid line having an outlet connected to the downstream return line and an inlet connected to the user circuit loop. 
     
     
         6 . A thermal energy network according to  claim 5  wherein the switchable valve system is arranged to connect the user circuit loop to both the upstream outflow line and the downstream return line by a respective pair of the first and fourth, or second and third, working fluid lines. 
     
     
         7 . A thermal energy network according to  claim 5  wherein the switchable valve system comprises a first control valve on the first working fluid line, a second control valve on the second working fluid line and a third three-way valve selectively and alternatively connecting the third working fluid line and the fourth working fluid line to a spur working fluid line connected to the user circuit loop. 
     
     
         8 . A thermal energy network according to  claim 1  further comprising, in each thermal load, a first heat exchanger coupled to the respective user circuit loop and connected to a heating system and a second heat exchanger coupled to the respective user circuit loop and connected to a cooling system. 
     
     
         9 . A thermal energy network according to  claim 1  further comprising a control system in the geothermal energy unit, the control system being adapted to control the temperature of the working fluid within the primary circuit loop within a preselected target range. 
     
     
         10 . A thermal energy network according to  claim 9  wherein the preselected target range is from 3 to 30° C. 
     
     
         11 . A thermal energy network according to  claim 10  wherein the preselected target range is from 5 to 21° C., optionally from 9 to 15° C. 
     
     
         12 . A thermal energy network according to  claim 9  wherein the control system is adapted to control the temperature of the working fluid at least partly by controlling the direction and rate of thermal energy exchange between the energy unit and a thermal energy source or store. 
     
     
         13 . A thermal energy network according to  claim 9  wherein the control system is adapted to control the temperature of the working fluid by providing to the primary circuit loop a positive or negative thermal input from the at least one energy unit capable of functioning as a heat source or a heat sink, the input being a balancing thermal input to compensate for thermal energy lost to or gained from the at least two thermal loads by the primary circuit loop. 
     
     
         14 . A thermal energy network according to  claim 9  wherein the connection comprises:
 a first working fluid line having an inlet connected to the upstream outflow line and an outlet connected to the user circuit loop, 
 a second working fluid line having an inlet connected to the downstream return line and an outlet connected to the user circuit loop, and 
 a third working fluid line having an outlet connected to the upstream outflow line and an inlet connected to the user circuit loop, and the network further comprising a first temperature sensor on the first working fluid line and a second temperature sensor on the second working fluid line, each first and second temperature sensor being configured to provide a temperature input to the control system. 
 
     
     
         15 . A thermal energy network according to  claim 9  further comprising an outlet temperature sensor on the outlet of the energy unit and an inlet temperature sensor on the inlet of the energy unit, each outlet and inlet temperature sensor being configured to provide a temperature input to the control system. 
     
     
         16 . A thermal energy network according to  claim 1  wherein the energy unit comprises any at least one of a geothermal energy unit, a solar energy unit, a boiler unit capable of combusting any carbon-containing fuel, including biomass or recycled material, a combined heat and power (CHP) unit, a liquid reservoir, a source of flowing liquid, a wind or water turbine, a hydroelectric power generator, a nuclear power generator, a ground source or air source heat pump, or any other energy unit capable of functioning as a heat source or a heat sink. 
     
     
         17 . A thermal energy network according to  claim 16  wherein the energy unit comprises at least one geothermal system installed in the ground, the geothermal system comprising at least one borehole heat exchanger having a working fluid therein for thermal energy exchange between the ground and the at least one borehole heat exchanger. 
     
     
         18 . A thermal energy network according to  claim 1  wherein each thermal load is located in a building. 
     
     
         19 . A thermal energy network according to  claim 18  wherein each thermal load is located in a respective building. 
     
     
         20 . A thermal energy network according to  claim 18  wherein each thermal load comprises at least one device, located in a building, which is capable of requiring a positive or negative heat demand. 
     
     
         21 . A method of providing thermal energy to a plurality of thermal loads, the method comprising the steps of:
 (a) providing an energy unit capable of functioning as a heat source or a heat sink, a primary circuit loop for working fluid being connected to the energy unit, the primary circuit loop comprising an upstream outflow line and a downstream return line,   (b) pumping the working fluid around the primary circuit loop successively from an outlet of the energy unit along the upstream outflow line, along the downstream return line and back to an inlet of the energy unit,   (c) providing in each of at least two thermal loads a respective a user circuit loop for working fluid, each user circuit loop being connected to the primary circuit loop by a respective connection at a respective location along the primary circuit loop, and   (d) selectively connecting the user circuit loop to the primary circuit loop in a selected working fluid flow direction within the connection so that the primary circuit loop selectively functions as a heat source or a heat sink for the user circuit loop.   
     
     
         22 . A method according to  claim 21  wherein the primary circuit loop consists of the upstream outflow line and the downstream return line. 
     
     
         23 . A method according to  claim 21  further comprising the step (e) of providing in each thermal load a first heat exchanger coupled to the respective user circuit loop and connected to a heating system and a second heat exchanger coupled to the respective user circuit loop and connected to a cooling system. 
     
     
         24 . A method according to  claim 23  further comprising the step (f) wherein the primary circuit loop selectively functions as a heat source for the user circuit loop and thermal energy is supplied to the heating system from the primary circuit loop via the user circuit loop. 
     
     
         25 . A method according to  claim 23  further comprising the step (g) wherein the primary circuit loop selectively functions as a heat sink for the user circuit loop and thermal energy is taken from the cooling system to the primary circuit loop via the user circuit loop. 
     
     
         26 . A method according to  claim 23  wherein in a heating mode working fluid flows along one working fluid line from the upstream outflow line and returns to the upstream outflow line along another working fluid line to provide heat to the heating system via the first heat exchanger. 
     
     
         27 . A method according to  claim 23  wherein in a cooling mode working fluid flows along one working fluid line from the downstream return line and returns to the upstream outflow line along another working fluid line to remove heat from the cooling system via the second heat exchanger. 
     
     
         28 . A method according to  claim 21  further comprising the step (h) of controlling the temperature of the working fluid within the primary circuit loop within a preselected target range. 
     
     
         29 . A method according to  claim 28  wherein the preselected target range is from 7 to 17° C. 
     
     
         30 . A method according to  claim 29  wherein the preselected target range is from 9 to 15° C. 
     
     
         31 . A method according to  claim 21  wherein in step (h) controlling the temperature of the working fluid is at least partly achieved by controlling the direction and rate of thermal energy exchange between the energy unit and a thermal energy source or store. 
     
     
         32 . A method according to  claim 21  wherein the connection comprises:
 a first working fluid line having an inlet connected to the upstream outflow line and an outlet connected to the user circuit loop, 
 a second working fluid line having an inlet connected to the downstream return line and an outlet connected to the user circuit loop, and 
 a third working fluid line having an outlet connected to the upstream outflow line and an inlet connected to the user circuit loop. 
 
     
     
         33 . A method according to  claim 32  wherein step (d) is implemented by a switchable valve system which is arranged to connect the user circuit loop to the upstream outflow line by either the first or second working fluid lines and to the downstream return line by the third working fluid line. 
     
     
         34 . A method according to  claim 33  wherein in a heating mode a first control valve of the switchable valve system the first working fluid line is open, a second control valve of the switchable valve system on the second working fluid line is closed and the third working fluid line is open. 
     
     
         35 . A method according to  claim 33  wherein in a cooling mode a first control valve of the switchable valve system on the first working fluid line is closed, a second control valve of the switchable valve system on the second working fluid line is open and the third working fluid line is open. 
     
     
         36 . A method according to  claim 32  further comprising a fourth working fluid line having an outlet connected to the downstream return line and an inlet connected to the user circuit loop. 
     
     
         37 . A method according to  claim 36  wherein step (d) is implemented by a switchable valve system which is arranged to connect the user circuit loop to both the upstream outflow line and the downstream return line by a respective pair of the first and fourth, or second and third, working fluid lines. 
     
     
         38 . A method according to  claim 37  wherein the switchable valve system comprises a first control valve on the first working fluid line, a second control valve on the second working fluid line and a third three-way valve selectively and alternatively connecting the third working fluid line and the fourth working fluid line to a spur working fluid line connected to the user circuit loop. 
     
     
         39 . A method according to  claim 32  wherein in step (h) controlling the temperature of the working fluid is at least partly achieved by controlling the direction and rate of thermal enemy exchange between the energy unit and a thermal energy source or store and the method further comprises sensing a first temperature on the first working fluid line and a second temperature on the second working fluid line, and providing the first and second temperatures as a temperature input to a control system implementing step (h). 
     
     
         40 . A method according to  claim 31  further comprising sensing an outlet temperature on the outlet of the energy unit and an inlet temperature on the inlet of the energy unit and providing the outlet and inlet temperatures as a temperature input to a control system implementing step (h). 
     
     
         41 . A method according to  claim 21  wherein the temperature of the working fluid is controlled by providing to the primary circuit loop a positive or negative thermal input from the at least one energy unit capable of functioning as a heat source or a heat sink, the input being a balancing thermal input to compensate for thermal energy lost to or gained from the at least two thermal loads by the primary circuit loop. 
     
     
         42 . A method according to  claim 21  wherein the energy unit comprises any at least one of a geothermal energy unit, a solar energy unit, a boiler unit capable of combusting any carbon-containing fuel, including biomass or recycled material, a combined heat and power (CHP) unit, a liquid reservoir, a source of flowing liquid, a wind or water turbine, a hydroelectric power generator, a nuclear power generator, a ground source or air source heat pump, or any other energy unit capable of functioning as a heat source or a heat sink. 
     
     
         43 . A method according to  claim 42  wherein the energy unit comprises at least one geothermal system installed in the ground, the geothermal system comprising at least one borehole heat exchanger having a working fluid therein for thermal energy exchange between the ground and the at least one borehole heat exchanger. 
     
     
         44 . A method according to  claim 21  wherein each thermal load is located in a building. 
     
     
         45 . A method according to  claim 44  wherein each thermal load is located in a respective building. 
     
     
         46 . A method according to  claim 44  wherein each thermal load comprises at least one device, located in a building, which is requires a positive or negative heat demand. 
     
     
         47 .- 96 . (canceled)