Low flow-rate pump

A centrifugal pump comprising:

• a electromagnetic stator including two half-stator assemblies, each said half-stator assembly comprising a plurality of coils arranged about a central aperture, each half stator assembly having a like number of magnetic poles and spacers of magnetic permeable material being mounted between said coils in said half stator;
• a rotor-impeller assembly comprising a longitudinal hollow member rotatable about its longitudinal axis, each end of said member forming one of a pair of inlets with a rotor-impeller fixed to said hollow member and presenting a substantially circular aspect to said stator, said rotor-impeller disc being magnetized to present a number of alternating magnet poles to said stator, said number being equal to the number of poles in said half stator, and said rotor-impeller including at least two fluid passages communicating between the interior of said hollow member and the periphery of said rotor-impeller;
• a housing including two opposed inlet ports, an outlet port and a pump volute in communication therewith and a cavity to receive said half-stator assemblies such that said central aperture in each coil is aligned with a respective one of said opposed inlet ports;
• a pair of bearing means, each bearing means located within a respective one of said central apertures and operable to receive said rotor-impeller to allow said rotor-impeller to rotate in said bearings in said pump volute between said half-stator assemblies wherein, when operating, fluid is drawn into said inlet ports and forced out of said outlet port by rotation of said rotor-impeller.

A solar domestic hot water system comprising:

• a solar energy collection panel for heating fluids, including a fluid inlet and outlet,
• a primary fluid reservoir,
• a fluid to fluid heat exchanger having a primary loop and a secondary loop, said primary loop connected between said solar energy collection panel outlet and said primary fluid reservoir,
• a domestic water reservoir connected across said secondary loop of said fluid to fluid heat exchanger to form a thermo-syphon,
• a pump connected between said primary fluid reservoir and said solar energy collection panel inlet, comprising:
• a stator including two half-stator assemblies, each said half-stator assembly comprising a plurality of electromagnetic coils arranged about a central aperture to form at least two magnetic poles, each coil having a like number of poles, bars of magnetic permeable material being mounted in said coils;
• a rotor-impeller assembly comprising a longitudinal hollow member forming two inlets and a rotational axis and a rotor-impeller disc fixed to said hollow member and presenting a substantially circular aspect to said stator, said rotor-impeller disc being magnetized to present a number of alternating magnet poles to said stator, said number being equal to the number of poles in said coils, and said rotor-impeller disc including at least two fluid passages communicating between the interior of said hollow member and the periphery of said rotor-impeller;
• a housing including two opposed inlet ports, an outlet port, a pump volute and a cavity to receive said half-stator assemblies such that said central aperture in each coil is aligned with a respective one of said opposed inlet ports;
• and
• a pair of bearing means, each bearing means located within a respective one of said central apertures and operable to receive said rotor-impeller to allow said rotor-impeller to rotate in said bearings in said pump volute between said half-stator assemblies wherein when operating, fluid is drawn from said primary fluid reservoir into said two opposed inlet ports and forced out of said outlet port of said pump by rotation of said rotor-impeller and delivered to said solar energy collection panel inlet;
• and
• a control system and power supply for said pump, said control system responsive to the temperature of said primary fluid at said solar energy collection panel outlet and the temperature of said domestic water entering said secondary loop to energize and de-energize said pump.