PV system TRAXLE

PV systems TRAXLE

Solar PV systems TRAXLE combine very effectively solar trackers TRAXLE and mono c-Si PV modules TRAXLE bifacial.

It can increase annual PV energy gain by up to 55% compared to fixed standard PV systems. Seasonal (summer) energy gain can be up to 75%. TRAXLE bifacial can DOUBLE pumping capacitu of solar water pumping/irrigation systems.

Price of the bifacial PV systems TRAXLE is EQUAL to fixed standard (monofacial) ones.

Price of the simple tracking support structures TRAXLE is EQUAL to fixed ones (based on equal energy gain).

Bifacial PV modules are manufactured on the same production line as standard (monofacial) ones. There is NO difference of the price.

There are only two negligible differences in the design of the TRAXLE bifacial PV modules compared to standard (monofacial) ones.

a) Transparent Tedlar film is used in the back-side laminate insted of white opaque one.
b) Metalic grid is used on the back-side on solar cells instead of full metal electrode.

Because there is either no or low price difference in the price of bifacial and monofacial modules it is reasonable to use bifacial modules which could produce 5-20% more energy (in comparison with monofacial PV module with the same nominal output power).
Polar axis solar tracker and/or tracking concentrator is always mounted on high support structures (to avoid contact of the rotating PV array with the ground). It improves back side energy collection in comparison with fixed PV arrays or even roof integrated PV modules. The energy gain can be in the range 10-15% (for typical albedo 0.3). Air-flow around the modules and corresponding cooling is improved as well (especially in comparison with roof integrated modules).
Additionally solar trackers/concentrators are usually oriented to the west, before backtracking, in the morning. The bifacial modules enable to collect direct back side solar radiation before backtracking. According to local climate the resulting energy gain could be 2-5%.
It is very advantageous that bifacial PV modules (fixed), transparent for infrared radiation, has lower operating temperature against monofacial ones (about 5-9oC). It is especially advantageous by solar trackers and tracking soft (C = 1.6) concentrators where PV modules are exposed to higher solar radiation than on fixed racks. Measured temperature of bifacial c-Si PV modules on the tracker was usually lower (by 5-8oC) than that of roof integrated monofacial c-Si modules. The reduced temperature of bifacial modules can also increase the energy gain by 2-5%.
The reduced temperature is also very important for lifetime of PV modules in soft (C = 1.6) concentrators. It should help to avoid degradation of polymer encapsulants of modules cased by higher temperatures (of monofacial modules).
A synergic combination of all above effects can boost energy gain by 15-25% in comparison with the same tracker/concentrator with monofacial modules.

surplu-a

Fig.1 Idealised power/time dependence

The polar axis solar tracker with c-Si bifacial PV modules will therefore deliver by about 50% more energy than fixed c-Si monofacial PV array with the same rated output power. The tracking bifacial soft concentrator will even double the energy gain against fixed monofacial PV array (Fig.1). Concerning the PV pumping systems there can be up to 100% and 150% pumping capacity surplus for tracks and tracking concentrators respectively.

References:
[1] V. Poulek, M. Libra, New solar tracker, Solar Energy Materials and Solar Cells, 51, 2, (1998), 113-120
[2] R.W. Stacey, P.G. McCormick, Effect of Concentration on the Performance of Flat Plate Photovoltaic Modules, Solar Energy, 33, 6, (1984), 565-569
[3 ]M. Libra, V. Poulek, Bifacial PV Modules in Solar Trackers and Concentrators, a New Approach to Supplying Power in Agriculture, in Proc. of the conference “Physical Methods in Agriculture, Approach to Precision and Quality”, Prague, August 2001, Kluwer Academic/Plenum Publishers, Hardbound, (2002), ISBN 0-306-47430-1