Solar collector with expandable fluid mass management system

Abstract

Solar energy conversion systems and methods use solar collectors and working fluid management systems to provide both efficient and safe operation under a wide range of operating conditions. In one embodiment, a solar collector and at least one fluid accumulator preferably with an integral heat exchanger, and at least two mass flow regulator valves enable working fluid flow into and out of the fluid accumulator.

1 . A solar energy conversion system comprising:
 a working fluid circuit for receiving and directing flow a working fluid within the working fluid circuit;   at least one solar collector in the working fluid circuit;   at least one fluid accumulator in the working fluid circuit;   a pump for moving working fluid in the working fluid circuit to the solar collector and to the fluid accumulator;   the working fluid circuit also extending between the solar collector and the fluid accumulator, and from the fluid accumulator to the pump.   
     
     
         2 . The solar energy conversion system of  claim 1  further comprising a cold inlet valve in the working fluid circuit between an output of the pump and the fluid accumulator. 
     
     
         3 . The solar energy conversion system of  claim 1  further comprising a discharge valve in the working fluid circuit between the fluid accumulator and an intake of the pump. 
     
     
         4 . The solar energy conversion system of  claim 1  further comprising an inlet valve to the fluid accumulator in the working fluid circuit located between the solar collector and the fluid accumulator. 
     
     
         5 . The solar energy conversion system of  claim 1  further comprising a heat source in thermal communication with the fluid accumulator. 
     
     
         6 . The solar energy conversion system of  claim 5  wherein the heat source is a heat exchanger located at least partially within the fluid accumulator. 
     
     
         7 . The solar energy conversion system of  claim 5  further comprising a condenser in thermal communication with the heat source. 
     
     
         8 . The solar energy conversion system of  claim 1  further comprising a heat exchanger within the solar collector. 
     
     
         9 . The solar energy conversion system of  claim 1  further comprising at least one expansion device in the working fluid circuit. 
     
     
         10 . The solar energy conversion system of  claim 1  further comprising a control system operative to control operation of the pump, and to control: the flow of working fluid from the solar collector to the fluid accumulator, the flow of working fluid from the pump to the fluid accumulator, and the flow or working fluid from the fluid accumulator to the pump by reference to operating pressures and working fluid temperatures. 
     
     
         11 . A method of converting solar energy acquired from a solar collector and transferred to a working fluid in a working fluid circuit of a solar energy conversion system having at least one solar collector in the working fluid circuit, at least one fluid accumulator in the working fluid circuit, a pump for moving working fluid in the working fluid circuit to the solar collector and to the fluid accumulator, the working fluid circuit also extending between the solar collector and the fluid accumulator, and from the fluid accumulator to the pump, the method comprising the steps of:
 controlling the pump to move working fluid through the working fluid circuit to the solar collector and to the fluid accumulator;   thermally controlling the fluid accumulator to cool the working fluid in the fluid accumulator;   removing working fluid from the fluid accumulator by controlling a valve between the solar collector and the fluid accumulator to an open position when the working fluid has reached a target set point temperature, and controlling a discharge valve between the fluid accumulator and the pump to an open position.   
     
     
         12 . The method of  claim 11  further comprising the step of removing working fluid from the fluid accumulator by reference to operating pressure and temperature of the working fluid in the fluid accumulator. 
     
     
         13 . The method of  claim 11  further comprising the step of monitoring the energy consumption by the pump by use of a mass flow meter, kilowatt-hour meter, or pump performance map. 
     
     
         14 . The method of  claim 11  further comprising the step of calculating an amount of working fluid in the fluid accumulator by reference to a database of NIST thermophysical properties. 
     
     
         15 . A solar energy conversion system comprising:
 a working fluid circuit for receiving and directing flow of a working fluid within the working fluid circuit;   at least one working fluid solar collector in the working fluid circuit;   at least one fluid accumulator in the working fluid circuit and located above the solar collector, an inlet an inlet valve in the working fluid circuit connected to an intake of the fluid accumulator, and a discharge valve in the working fluid circuit between the fluid accumulator and the solar collector, and   a heat source for controlling a temperature of the fluid accumulator.   
     
     
         16 . The solar energy conversion system of  claim 15  wherein the heat source for controlling a temperature of the fluid accumulator is a heat exchanger in thermal communication with the fluid accumulator and with a fluid accumulator condenser. 
     
     
         17 . The solar energy conversion system of  claim 15  further comprising a heat transfer fluid circuit connected to the condenser, the heat transfer fluid circuit comprising a heat transfer fluid condenser and a heat transfer fluid solar collector, the heat transfer fluid condenser located below the fluid accumulator condenser and above the heat transfer fluid solar collector. 
     
     
         18 . The solar energy conversion system of  claim 15  further comprising an intake valve in the heat transfer fluid circuit proximate to an intake to the fluid accumulator condenser. 
     
     
         19 . A method of converting solar energy acquired from a solar collector and transferred to a working fluid in a working fluid circuit of a solar energy conversion system having at least one working fluid solar collector in the working fluid circuit, at least one working fluid accumulator in the working fluid circuit and means for controlling a temperature of the fluid accumulator, and wherein the solar collector is located below the fluid accumulator whereby the working fluid solar collector operates as a thermosiphon, the method comprising the steps of:
 controlling introduction of the working fluid into the fluid accumulator by operation of an inlet valve in an inlet in the working fluid circuit to the fluid accumulator;   cooling the working fluid in the fluid accumulator;   discharging working fluid from the fluid accumulator to the working fluid solar collector according to a desired mass flow rate of the working fluid in the working fluid circuit.   
     
     
         20 . The method of  claim 19  wherein the working fluid in the fluid accumulator is cooled by a heat exchanger in thermal communication with a fluid accumulator condenser, by controlling flow of a heat transfer fluid through the fluid accumulator condenser. 
     
     
         21 . The method of  claim 20  further comprising the step of heating the heat transfer fluid by a heat transfer fluid solar collector in a heat transfer fluid circuit connected to the fluid accumulator condenser. 
     
     
         22 . The method of  claim 21  further comprising the step of passing the heat transfer fluid through a condenser in the heat transfer fluid circuit prior to the heat transfer fluid solar collector. 
     
     
         23 . The method of  claim 22  further comprising the step of operating the heat transfer fluid solar collector as a thermosiphon. 
     
     
         24 . The method of  claim 19  further comprising the step operating the working fluid solar collector in a substantially stagnant mode. 
     
     
         25 . The method of  claim 19  further comprising the step of isolating a flow of a portion of the working fluid through the fluid accumulator and the working fluid solar collector from a remainder of the working fluid circuit. 
     
     
         26 . The method of  claim 19  further comprising the step of operating the working fluid solar collector at a temperature relatively higher than an ambient temperature. 
     
     
         27 . The method of  claim 19  further comprising the step of operating the working fluid solar collector at a pressure which is relatively lower than a pressure in the working fluid circuit.