We CARE Solar, a nonprofit organization in Berkeley, California, offers what's known as a solar suitcase, a small, off-grid photovoltaic (photovoltaic) power system and lighting solution, in a rugged case. Since 2009, these systems have provided light and power to telemedicine clinics throughout the developing world. The solar-powered luggage can currently be found in nearly 300 clinics in 18 countries. Many of these clinics have no other source of electricity or light because of their remote location and great distance from the grid. Others receive only sporadic power, due to frequent grid failures. Most rely on kerosene lamps or candlelight to perform common medical procedures and even complete surgery. Such conditions make the Sun Travel Box a very popular addition to a clinic's U12-006 (UX120-006M) four-channel data logger.
challenge
Regional variations in climate and existing sunlight from site to site make it difficult to determine proper system sizing (PV module size, battery size, and user load matching). PV module systems with light user loads may suffer from chronic battery charging, causing the battery to fail. Systems equipped with a battery that is too small for the user's energy demands can experience battery deep cycling and also result in short battery life. Understanding a site's energy needs and available solar energy is key to designing a properly balanced system that will continue to function for many years to come. While the team made every effort to secure each system's geographic location, monitoring system performance allowed it to spot installation flaws, quantify usage patterns, and identify areas for future design improvement. Since systems are often located in remote, rugged environments, it is difficult for us to take care of solar crews to visit them on a regular basis once they are installed. When the Sun Suitcase program began, the system's performance monitoring system logged through human data entry; however, the data was often incomplete, inconsistent, and subjective. We were concerned that the Sun team needed a better way to record system performance data with the U12-006 (UX120-006M) four-channel data logger and monitor usage patterns to ensure correctly sized photovoltaic systems are being implemented in medical clinics.
solution
Knowing the performance of the installed solar box system, we cared about the research of the sun and finally decided to start the HOBO® U12-006 (UX120-006M) four-channel data logger as an effective and cost-effective solution.
Since energy is precious in the clinic, these self-powered data loggers U12-006 (UX120-006M) are four-channel data loggers that immediately appeal. The compact HOBO U12-006 (UX120-006M) four-channel data logger has no need for human interaction for months and can therefore be incorporated into solar box installations without further user training. Accompanying hoboware® software is used to download collected data and graphical analysis. The technicians in our country, who regularly travel to remote clinics for other jobs, can quickly learn to unload and restore the collected data files to team members in the United States. By monitoring PV voltage, battery voltage, and load usage, the team can quickly get a snapshot of system performance and usage patterns.
result
In November 2011, the Solar We Care group worked with medical technicians in northern Nigeria to install solar trunk systems in some regional clinics. Six representative site systems were equipped with a HOBO U12-006 (UX120-006M) four-channel data logger, directly connected to the channel with voltage readings at critical points within the PV system. A small voltage divider circuit is used to step down the HOBO U12-006 (UX120-006M) four-channel data logger input to the massive nominal 12V voltage down to the appropriate level.
These connections allow the logger to track photovoltaic voltage, battery voltage, and user load voltage. Loggers will record and collect data at 15-minute intervals for a period of approximately six months. Once collected, the recorded data is processed and integrated to determine energy production, battery cycle depth, and daily power usage, all of which are self-evident in determining system health and usage profiles.
When the U12-006 (UX120-006M) four-channel data logger data was analyzed, our concerned solar engineers were pleased to see that the power systems were continuing to function as designed. The data clearly shows when and when the system's lights are being used each night. This also confirms that all batteries are being charged on a daily basis, which is key to ensuring long battery life. In some cases, the data collected even showed that smaller PV modules could be used. This knowledge will allow our solar care team to utilize smaller, cheaper PV modules for future installations, and ultimately save money that will allow the group to power more clinics.
Information obtained from the Nigerian project was directly applied to the system design for an installation in southwestern Uganda. The "Gorillas in the Mist" movie setting, this part of Uganda is known as a difficult climate because of frequent fog, dense foliage, and hilly terrain for solar power. Using the data collected from the Nigerian system to properly design new solar suitcases for the Ugandan climate, the research team traveled in February 2013 to install the units in nine telemedicine clinics. For more information, please call Beijing Sike Keyi Instrument Co., Ltd. These systems will generate electricity and lighting for the clinic, while the data collected by the four-channel data logger of the HOBO U12 series data logger U12-006 (UX120-006M) will be collected and analyzed this summer, after the rainy season. It is expected that these data will provide valuable input into the design and installation of the two solar box systems to be implemented beyond 2013.
