The Solar Boiler™ module is a Shell-and-Coil all copper heat exchanger and glycol reservoir with eMag Solar Pump™. The heat transfer fluid in the solar loop circulates from the reservoir to the solar collectors and back through the coils of the heat exchanger using the Solar Pump's positive displacement pump. The solar loop is closed from the atmosphere and regulated by the Solar Pump's built-in differential temperature controller. Circulation on the shell or water side of the heat exchanger is generated by natural circulation.
Shell & Coil Heat Exchanger: The Solar Boiler™ uses Thermo Dynamics high performance Shell-and-Coil™ heat exchanger mounted in the Side-Arm™ configuration. This system provides a highly stratified storage tank. The storage tank can be any commercially available tank with the correct connections.
Controls: The Solar Boiler™ uses a proportional control strategy, achieved by the variable output of a 20W photovoltaic module. The variable collector flowrate and thermosyphonic flow between the Solar Boiler™ and the storage tank ensure that high quality water is supplied to the auxiliary heater throughout the year. The PV module drives the brushless DC motor through a linear current booster to ensure good performance at low light levels.
The e-Mag Solar Pump™ with Differential Temperature Control & Linear Current Booster (LCB) is a brass body, vane-type, positive displacement pump. The pump has special clearances and ethelyene-propylene seals for high temperature protection. It has a maximum output pressure of 500 kPa (73 psi). The nominal flow rate is 1.2 L/min. (0.32 USGPM). The pump is driven by an efficient brushless DC motor and includes a differential temperature controller. Nominal power consumption is 18 watts (1/40hp) at nominal 12 VDC.
The e-Mag Solar Pump™ motor driver includes TDL's most recent Linear Current Booster (LCB) technology to match the power delivery of the PV module to the DC motor under varying light conditions. The unit also features differential temperature control, fail-safe protection, high-temperature limits, and an electronic jolting function to overcome static friction and/or minor pump blockages.
At peak irradiance the PV module runs the motor at rated speed, at lower light levels the LCB transforms the voltage into current to allow the motor to start. The motor runs at reduced speed at lower light levels providing a proportional control for the Solar Boiler™. The controller also measures the collector temperature and the storage temperature to provide differential temperature control.
Freeze protection is provided by a solution of 40% Propylene Glycol USP and 60% distilled water in the solar loop. Propylene glycols freezing point is -19°C (-2.4°F). The water in the system starts to form ice crystals and pumping becomes difficult. The 40/60 aqueous solution of Propylene Glycol provides burst protection to -51°C (-60°F).
Contamination Protection: The Solar Boiler™ module operates at atmospheric pressure. The storage tank is at city water pressure and the water will flow into the Solar Boiler™ module if there is a leak in the heat exchanger, diluting and dispelling the small volume of heat transfer fluid from the system. Propylene glycol is nontoxic food grade approved heat transfer fluid and is compatible with a single wall heat exchanger.
Leak Detection: The glycol reservoir in the Solar Boiler™ module will overflow onto the floor. Propylene glycol is clear (older propylene glycol may be slightly green and/or brown). The fluid has an oily, slippery feeling when rubbed between your fingers.
High Temperature Limit: A high temperature limit sensor installed on the Solar Boiler™ module prevents the storage tank from exceeding 82°C (180°F). An adjustable tempering valve can be installed on the hot water outlet if required by the local plumbing code.
Over Temperature Protection: The boiling point of 40/60% aqueous solution of Propylene glycol/distilled water is 105°C (221°F). The maximum recommended bulk temperature is 163°C (325°F) and the maximum recommended film temperature is 191°C (375°F). The Solar BoilerTM is equiped with a 414 kPa, (60 psi) pressure relief valve (PRV) on the solar loop. In the event of a pump failing to circulate the glycol on a hot sunny day, the glycol expands in the solar collector, increasing the pressure in the solar loop, and thereby increasing the boiling point of the glycol to prevent boiling.
Over Pressure Protection: A 414 kPa (60 psi) pressure relief valve is installed on the Solar Boiler™ Module for safety.
Corrosion Protection: In the collector loop, the propylene glycol, when the pH is approximately 5-7, is non aggressive. All wetted parts are copper, stainless steel, carbon and brass.
Plumbing Connectors: Copper tubing with 3/8" compression fittings.