Before prudent investors will commit, they want to know what energy production results can be expected from a given PV array or plant. Understanding PV module and array performance is fundamental to predicting and maximizing actual electrical production and for scheduling ongoing maintenance.
The standard method for testing module and array performance in the past has been to utilise a single reporting condition set at an artificial uniform ambient temperature of 25°C. This standard reporting condition does not reflect actual on-site operating conditions where 50°C (or -10°C) can be more common. More importantly, an artificial environment does not accurately address variable weather factors involved in actual outdoor performance.
Being able to provide quality ‘bankable’ statistics from a given site is fast becoming a primary concern. The bankable data that investors seek is based on the ratio between the output power of the equipment and the available sun at the specific location. To determine this ratio (and ultimately the efficiency of a site) performance data must be initially gathered on-site to create a base of output expectation, and then continually assessed to track whether the plant is meeting the anticipated production goals.
Simply monitoring the level of energy production of PV modules or arrays only provides information about the problem, not the solution. Using continuously active on-site meteorological data gathering equipment, monitoring can expose certain problematic conditions that reduce optimum solar gain, including shadowing from structures around plant, misaligned or moved panels, and dirt on the panels. Gauging the surface temperature of a given panel is also helpful to monitor because if the actual panel gets too hot the efficiency will go down.
In response to the need for a compact easy to install weather station specifically designed for solar plants that require the highest standard in dependable data, RainWise Inc. based in Maine, USA, developed the PVmet weather station series.
Consolidating all the necessary sensors into a convenient package, the weather stations in the PVmet series offer sensors aimed at dirt, misalignment and shadowing concerns, global and/or plane-of-array sensors for irradiance solar monitoring, back-of-module sensors to track the panel temperature, and wind speed/direction sensors to track cooling effects. Wind speed can also give indications of incoming storms, information that helps tracking panels to go into ‘stow’ formation for protection - an important safety measure in hurricane and tornado prone areas.
Sites being funded by investors require a high level of accuracy and accountability in the data acquired by the sensors, the solar sensors in particular. In response to this concern, RainWise upgraded the irradiance sensor to the highly accurate Kipp & Zonen thermopile CMP pyranometer line and is now able to offer a spectrum of these higher accuracy sensors depending on the needs of the industry. The wind sensor has also been upgraded to an ultrasonic sensor with no moving parts, thus reducing maintenance and repair and increasing longevity.
PVmet efficiency monitoring weather stations are successful in providing the optimal environmental data necessary for maximizing actual on-site performance modeling. Providers and investors now have the necessary instruments for acquiring bankable information with which to move forward in the development of dependable mid and large-scale solar power plants.
Find out more about RainWise Inc. and the PVmet Solar Panel Monitors at: www.rainwise.com
By Sonia Turanski, RainWise Inc.