A solar tracker is a PV rack that rotates on an axis to face the sun as it crosses the sky. It is well known that solar tracking will increase energy yield by 25-50%. For solar pumping, tracking offers even greater gains and benefits that can greatly reduce system cost. Optimum yield during the peak watering season Tracking offers more water out of smaller, less expensive system by increasing performance when the most water is needed - during long sunny days of the growing season. This is most appropriate for agricultural and seasonal summer uses.
Prevention of pump stalling
Many solar pumps experience a disproportionate drop in performance when the sun is at a low angle (early morning and late afternoon). When the PV array output is less than 50%, a centrifugal pump may produce insufficient centrifugal force to achieve the required lift. By causing the pump to run at full speed through a whole sunny day, tracking can often DOUBLE the daily water yield.
Water distribution for PV-direct irrigation
Solar irrigation can be practical with NO storage device, in some situations - The soil itself stores water during cloudy days! However, sun-tracking may be necessary to achieve uniform water distribution. When water flow is reduced, a sprinkler just makes a puddle. A trench or drip line feeds only the first few plants, or the lowest ones. A tracking array minimizes the periods of reduced flow. It makes solar-direct water distribution an option for dry sunny regions. There will still be short periods when distribution is not even, but our customers have proven that it can work.
Expediting the design process
The tracking decision as a handy variable in the design process. Often you find a system that produces a little bit less than is needed, but the next larger system costs much more. A tracker is a low-cost means to increase the yield of the smaller system.
When NOT to use a tracker
Tracking is least effective during shorter winter days, and during cloudy weather. If the need for water is constant during the year or greatest in the winter, or if the climate is very cloudy, then it may be more economical to design the system with more solar watts and no tracker.
Dankoff Solar has sold passive Track Rackstm by Zomeworks, since 1983. The tracking process uses no moving parts and no electrical parts, only a fluid/vapor flow that tips a balance. An automotive type shock absorber may need replacement about every 5 years.
Isn't there more to go wrong?
Zomeworks Track Racks rarely fail, even long after the 10-year warranty. In a rare case of failure, it will hold at mid-day position and the pump will still function, or it can be tracked by hand. Field repair is accomplished easily by attaching outboard canisters.