Growing clean energy demand not only increases the number of available technologies for producing electricity from solar power, but also raises the complexity of solar power plants. As a result, performance monitoring has become a critical factor. The solar monitoring station providing data about the available solar energy is a key part for a solar energy plant - either CSP or PV. Knowing the availability of energy level is critical for running a solar plant.
Kipp & Zonen’s Solar Instruments
Kipp & Zonen offers the following instruments for performance monitoring of a solar power station:
Pyranometers - Radiometers designed for irradiance measurement on a plane surface, typically from solar radiation and lamps.
Pyrgeometers - Designed to measure IR radiation, for both atmospheric and material testing research applications.
Pyrheliometers – Indented for unattended normal incidence direct solar radiation measurement research.
Sun Trackers – These are all-weather, consistent, and economical tracking and positioning devices available either as a computer-based Positioner or a dedicated Sun tracker.
UV Radiometers – They are broadband scientific UV radiometers to measure ‘Total UV’ and with a spectral response that is adapted to UVA, UVB and the UVE Erythemal (sunburn) action spectrum of the human skin.
Net Radiometers – They are used to measure incoming and out-going short-wave (0.3 to 3µm) and long-wave (4.5 to >40µm) radiation.
Horticultural Sensors - Radiometers specially engineered for horticultural and agricultural applications to measure photo-synthetically active radiation.
Sunshine Duration Sensors - Radiometers designed to measure sunshine duration.
Laboratory Thermopile – This equipment measures radiant fluxes and is sensitive to radiation from 0.2 to 50µm, and has a field of view of 10°.
Data Loggers – Different models of data loggers are available to read out and store data from Kipp & Zonen’s various sensors.
Mobitoring of Solar Radiation at Solar Power Plant
Figure 1. Solar Monitoring Station.
A complete solar monitoring station (Figure 1) comprises a pyranometer for global horizontal irradiance (GHI) measurement, a shaded pyranometer for diffuse horizontal irradiance (DHI) measurement, and a pyrheliometer for direct normal irradiance (DNI) measurement. These solar instruments are installed on a sun tracker (Figure 2), which follows the sun all through the day to provide data on solar radiation available at the site.
Figure 2. SOLYS 2 Sun Tracker from Kipp & Zonen.
For PV plants, a tilted pyranometer installed at the same angle as the PV panels is critical for their performance and is a key component of the solar monitoring station. For CSP plants, the monitoring station often consists of a pyrgeometer for infrared radiation measurement from the atmosphere. An additional weather station consisting of sensors for precipitation, wind and temperature also provides data for analysis of the plant performance. Two measurement sites are typically needed for larger plants to provide consistent data throughout the site and redundancy of the measurements.
Issues to be Considered in Solar Monitoring Station Installation
An unobstructed field of view is essential for the solar monitoring station, meaning that there must be no shadows all through the day and no objects, buildings, or trees obstructing the light from the solar equipment. In certain cases, the monitoring station needs to be installed at some height above the ground.
The monitoring station’s base needs to be stable and the best option is a concrete or sturdy steel platform. Protecting the monitoring station from damage is essential and can be achieved with a secure fence.
Maintenance for Reliable Operation of a Solar Monitoring Station
The glass domes and windows of the instruments need to be cleaned periodically as the presence of dirt will considerably reduce data consistency. Water or alcohol must be used for cleaning, but not with industrial cleaning liquids and soaps as they leave residual films on the dome surface, thereby affecting optical properties of the dome.
It is recommended to use a special microfiber cloth, provided along with Kipp & Zonen instruments, to perform gentle cleaning of the surface without leaving scratches or particles on the dome. Contamination of the instruments can be reduced by using ventilation units. It is necessary to replace the desiccant periodically to maintain the instruments dry inside. The thread of the drying cartridge and the sealing ring must be devoid of sand or dirt while replacing it in order to ensure that the equipment is airtight.
It is necessary to check the correct levelling of the equipment and alignment of the pyrheliometer periodically. Regular maintenance is not required for modern sun trackers, but older models might require annual oiling of gears or correction of the internal clock if they do not have automatic correction through GPS data.
The aforementioned maintenance steps will keep the solar monitoring station to perform at a high level, thereby ensuring the solar energy plant to operate well.
This information has been sourced, reviewed and adapted from materials provided by Kipp & Zonen.
For more information on this source, please visit Kipp & Zonen.