THE TRACKER

pvpumps.com – Nearly all solar collectors need some stand either fixed or tracking.

Price (as low as 85 U$/m2) and reliability (ab to 5 years warranty) of the new simple tracking stand is close to that of fixed stand.

Solar tracker can boost capacity of the PV pumping system by 70-80%. The new tracker, therefore, reduces price of the water delivered by the PV pumping system by about 50%.
The low cost solar tracker is based on a new arrangement of solar cells connected directly to reversible D.C. motor. Solar cells both sense and provide energy for tracking.

At least one solar cell (or panel) is fixed to a rotary axle of the tracker and its plane is declined, from the plane parallel to the axle and perpendicular to the collectors of solar energy, approximately by 20 o eastwards (see Fig. 3.). The solar cell (panel) is connected directly to a D.C. electromotor (see Fig. 4). Both the motor and the self-locking transmission are integrated in the tracker axle (TRAXLETM).

Figs. 1-3 show principle of the tracker. Solar collectors are oriented eastwards. As the sun moves from the east to the west, angle of incidence bof solar radiation on sensing/driving cells increases untill power of the driving D.C.motor, connected to these cells, is high enough to move solar collectors. Then the angle of incidence b starts to decrease untill the power of the D.C. motor is lower than that necessary to move solar collectors. Additional antiparallel solar cells, placed in the same panel, enables backtracking of the tracker from any position.

track

Integration of antiparallel solar cells in one “bifacial” panel makes the tracker more compact, more reliable and less expensive. Antiparallel solar cells can be even manufactured monolitically on single substrate.

Backtracking time of the new tracker is a few minutes only even in cold climate (-40oC) while by passive trackers (either freone or shape memory) the backtracking time is more than one hour [1] at the same temperature.

Area of the auxiliary solar panel of the tracker is about 1% of the area of moved solar collectors while collectible energy surplus is up to 40% [2-5] and pumping capacity surplus is up to 80% [6]. Area related torque [9] is 2 N.m/m2 (AM1.5).

The efficiency of the tracker increases with efficiency of solar panels. Force necessary to overcome friction and aerodynamic drag remains constant while the area related output power (W/m2) of driving/sensing solar panel increases. In 70s when efficiency of solar panels was approximately ~10%, auxiliary solar panels (tracking &backtracking) as large as 2% of the solar collectors were needed while in the near future ~20% efficient auxiliary solar panel will represent less than 1% of the area of solar collectors.

solar

Spesification

solar-2

solar-3

The rotary axle of the new tracker should be oriented in north/south direction with accuracy of about +10%. It makes adjustment of the new tracker very easy. Additionally the new trackers are less heavy (approx. 7kg/m2) than preceding ones. It also contributes to easy instalation (and to low transport expenses). The only parameter which have to be well adjusted is a balance of solar collectors (the tracker is designed to rotate not to lift the collectors). Centre of gravity of the rack have to be on the axis of the TRAXLETM or slightly below the axis.

Main advantages of the new tracker over other systems (either active or passive)

  • Works also at low temperature down to -30oC
  • Price of the tracker 85-195 US$/m2
  • Collectible energy surplus up to 40% over fixed arrays
  • Pumping capacity surplus up to 80%
  • No maintenance
  • Easy installation (no complex adjustment)
  • Lightweight (low transport cost, easy installation)
  • Proven silicon PV technology & D.C. motor
  • Self-locking transmission (protects tracker against wind).
  • Extremely simple (i.e. reliable) solid state system
  • Automatic morning orientation within 5 minutes
  • Aluminium structure & stainless steel fasteners.
  • Horizontal, vertical or polar axis tracking possible
  • Scalable system (any size is possible)
  • Portable system

CONCLUSION

The new tracker is less expensive (antiparallel driving/sensing solar cells integrated in one case enables prices down to 85 USD/m2), works well at low temperatures (down to -30oC) and unlike perpendicular (or shadowed) sensing cell it enables backtracking from any position.

Both the new tracker and the driving unit are worldwide patent pending (PCT).

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References:

[1]  H.U. Rauth, A. Dress, R. Pruschek, T. Weidele, Annualy generated electricity of one and two axes solar tracking systems, Proc.13th European PV Solar Energy Conference, Nice 23-27 October 1995, pp.1015-1018.
[2]  M.S. Imamura, Grid connected PV plants: field experiences in Germany a pursuit of higher solar energy collection efficiency, Solar Energy Materials and Solar Cells 35, (1994) 359-374.
[3]  S. Nann, Potentials for tracking photovoltaic systems and V-troughs in moderate climates, Solar Energy 45, (1991) 385-393.
[4]  J.M. Gordon, J.F.Kreider and P. Reeves, Tracking and stationary flat plate solar collectors: Yearly collectible energy correlations for photovoltaic applications, Solar Energy 47(1991) 245-252.
[5]  D. F. Menicucci, The determination of optimum mounting configurations of flat plate photovoltaic modules based on a structured field experiment and simulated results from PVFORM, a Photovoltaic System Performance Model, Sandia Report SAND 85-1251.
[6]  F.H.Klotz, PV systems with V-trough concentration and passive tracking concept and economic potential in Europe, Proc.13th European PV Solar Energy Conference, Nice 23-27 October 1995, pp.1060-1063.
[7]  P. Baltas, M. Tortoreli and P.E. Russell, Evaluation of power output for fixed and step tracking photovoltaic arrays, Solar Energy 37, (1986), pp. 147-165.
[8]  J. M. Gordon and H.J. Wenger, Central-station solar photovoltaic systems: Field layout, tracker and array geometry sensitivity studies, Solar Energy 46,(1991), pp. 211-217.
[9]  V. Poulek, M. Libra, New Solar Tracker, Solar Energy Materials and Solar Cells, 51, 2 (1998) 113-120.