Thermal energy network and methods of providing thermal energy

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 consisting of 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,
• 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 at a location downstream of the first working fluid line, and an inlet connected to the user circuit loop, wherein the third working fluid line comprises a return pump configured to return the working fluid to the upstream outflow line through the third working fluid line, 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,
• 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,
• wherein the first working fluid line of the second thermal load is connected to the primary circuit loop at a location downstream of the third working fluid line of the first thermal load, and
• wherein the second working fluid line of the second thermal load is connected to the primary circuit loop at a location upstream of the second working fluid line of the first thermal load.