Located in Yarmouth, Nova Scotia, the YMCA Yarmouth operates year round offering recreational activities such as gym, aerobics, personal training, children activities, and swimming. The swimming pool is operated year round for family swims, as well as 3000 swimming sessions per year. The swimming pool is 30 ft x 50 ft with a shallow and deep end.

The current method of heating the pool is by oil fired boilers transferring heat through a heat exchanger to the pool. A pneumatic control system regulates the amount of heat be transferred to the pool. The desired maintained pool temperature is 84 °F

System Description

In November 2003, Thermo Dynamics Ltd. was approached by the YMCA to design a solar thermal pool heating system to offset the cost of fuel oil. In July of 2004, TDL began to install, supplied and installed a solar pool heating system.

Solar Collectors

The solar collectors are mounted on a flat roof located directly above the swimming pool. The collector mounting structure is constructed of galvanized steel channel. The structure is fastened to pressure treated lumber which has been incorporated into the roof and weather proofed. The orientation of the solar collectors is due south with an angle of 45° to the horizontal. There are a total of 40 Thermo Dynamics G32 solar collectors (119 m2 gross collector area; 127 m2 aperture area). The solar collectors are the liquid-flat-plate type, with low-iron tempered glass glazing and Sunstrip absorber plate. The solar collectors are arranged in two arrays of 20 solar collectors. There is a front array of 20 solar collectors and a rear array of 20 collectors. Within each array, there are two sub-arrays of 10 solar collectors in parallel with each other. Each sub-array of 10 solar collectors has 5 solar collectors plumbed in series with another 5. The arrays are plumbed independently, and valved, to allow servicing of one array without shutting down the entire system.

Each array is supplied with glycol via 1” nominal copper tubing. The hot solar return from each array is also 1”. All piping is covered with 1/2” thick Armaflex pipe insulation. Expansion joint have been installed in both the supply and return lines. All supply and return piping is run down through the pool room to the mechanical room.

Heat Exchangers

Each solar collector array has its own heat exchanger bank. The 2 banks are plumbed in parallel on the pool side of the heat exchangers. Therefore if one solar collector array is shut down, the other array can continue to supply heat to the swimming pool.

Each heat exchanger bank consists of 2 Thermo Dynamics Ltd DTL Series tube and shell model# D3T14 L12. (Each D3T14L12 is rated for 24 kW) The heat exchangers are arranged so that counter flow operation is achieved.
Isolation, drain valves, and air vents have been installed to allow for easy maintenance on the heat exchangers.

Solar Pumps™ and Photovoltaic Modules

A propylene glycol solution (40:60, glycol:water) is circulated through the solar collectors by four TDL P50140M Solar Pumps™. Both the front and rear solar collector arrays were charged with glycol and pressurized to 40 psi. Two Solar Pumps™ circulate the glycol in a each array of twenty solar collectors. Each pump is powered by two BP Solar 20-Wpeak photovoltaic modules wired in series to give a nominal 30 VDC system. The photovoltaic modules are rated at 1.2 amperes at 15 VDC operation. The PV modules are mounted above the rear array of solar collectors and in the same plane as the solar collectors. The Thermo Dynamics Booster™, a linear current booster, is wired between each pair of PV modules and the permanent magnet DC motor that drives the pump. The TDL Booster™ provide for pump start-up and continuous running at very low levels of solar radiation (approximately 100 W/m2). At full sun the PV modules produce a flow rate of over one liter per minute per solar collector.

A single differential controller complete with a 4 pole single throw relay, ensures that the collectors do not cool the pool water. As well, several thermostats have been installed to prevent pool water overheating.


View photographs of the installation


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