Solar Powered Commercial DC Pool Pump

The pool pump system being evaluated is a hybrid AC and solar powered DC system. A DC pool pump is directly fed by PV panels installed on the roof of a building. An automatic digital motor controller changes the torque and speed of the DC motor based on the input power coming from the PV panels. The system also has automatic controls which engage a secondary AC pool pump with a Variable-Frequency Drive (VFD) to supplement any flow loss due to decreased power from the PV panels. This ensures the minimum commercial pool water turnover requirements are met. This project is a field evaluation. The energy savings potential will be determined and the system’s ability to meet minimum commercial pool water turnover requirements will be verified.

This field assessment evaluates the effectiveness of an emerging energy efficient technology that uses solar energy. It directly supports the penetration of similar technologies in the residential and small commercial marketplace. The assessment demonstrates how a multifamily pool pump system was retrofitted with a variable speed drive (VSD) pump and two solar-powered pumps to reduce grid energy consumption, especially during peak hours. The project seeks to verify that this proposed emerging technology system is able to maintain the minimum health code required filtration flow rate and to quantify the total energy savings. The energy savings result from the installation of an efficient VSD pump and two solar photovoltaic powered pumps. The evaluation measures all parameters involved in the community pool’s pump system. Two weeks of baseline data were compared to three months of emerging technology system data. The baseline system consisted of two constant speed pumps with 1.5 HP motors operating in parallel and running 24/7. The new installation required the removal of the two existing pumps and the installation of two 2.3 HP direct current (DC) solar-powered pumps and one 3.0 HP alternate current (AC) grid powered pump with VSD. The solar pumps operate whenever sufficient sunlight is available. The grid powered pump speed is modulated by a controller that is connected to a flow meter installed in the pool return line. This maintains the health code required flow rate of 139 gallons per minute (gpm) for this size pool at all times. In other words, the grid pump provides whatever is needed in addition to the solar pumps. The evaluation found that the system is able to meet the minimum health code required flow rate; the solar pumps produces energy savings; and the VSD pump contributes to further savings. Some savings can be attributed to a change in system piping, but it is difficult to determine to what extent. In order to extrapolate the monitoring data to annual savings, regression analysis with solar insolation was used to accurately predict solar production and how it affects the speed of the grid powered pump throughout the year. The total system cost was $35,298.56. By factoring in an annual 2% utility rate increase, a 30% investment tax credit, and a blended utility rate of 0.15 dollars per kilowatt hour ($/kWh), the estimated payback period is 8.0 years.