Course: 22.527 – Solar Systems
Semerter: Spring 2007
Instructor: John Duffy
Partner: Village Empowerment Project
Project Description: Yearly Power Output of Peruvian PV Systems for Carbon Offset Credits. The University of Massachusetts Lowell has started a project that has included the installation of solar power stations in several mountain communities in Peru which lacked electric power. The success of this project prompted the Vice President of Environmental Affairs of Staples to inquire about purchasing carbon offset credits created by these photovoltaic (PV) systems. The purpose of student reports was to estimate the electricity produced by the systems installed in Peru and then calculate the resulting carbon offset that could be purchased by Staples.
The first objective for students was to estimate the incident irradiation by month for each of the installations, based on recorded weather data. They looked at the sites of Raypa and Cochapeti, for which there was solar data. Average daily solar irradiation was obtained by summing 24 hours worth of hourly solar irradiation, for each year. Students found that in Raypa it varied from a low of 5 kWh/day in May, to a high of 6 kWh/day for October. Cochapeti exhibited less variation, ranging from 5.3 in January to 5.9 in September.
A secondary objective was for the students to measure the Isc and Voc of at least two of the Evergreen 50W modules in the UML solar lab. To estimate electricity produced in kWh by month, students calculated the loads used by the lights, radios, and refrigerator at the Raypa clinic, which was divided by the efficiency of the solar systems that supplied them. Students carried out the same calculations for the Cochapeti clinic. Then students determined the carbon offset, to find out if it is economically feasible for Stables to purchase them. Students determined that the system that powers the Raypa clinic saves .28 tonnes of carbon dioxide over a traditional coal fired power plant per year, or a full carbon credit over the measured lifetime of the system so far. Cochapeti contributed an additional .32 credits per year, or .64 over its two year measured lifetime. They also found that the two systems give .6 carbon credits per year, and therefore surmised that there has been an accumulated 6 carbon credits since the project began 10 years ago in 1997. Since these are only two of among 20 clinics, they estimates that 60 carbon credits have been generated by all the PV systems installed thus far in Peru. The students concluded that since these solar systems generate an appreciable amount of electricity and thus carbon offset, it is definitely worth investigating the sale of the resulting carbon credits to Staples.
Learning objectives met by the S-L project:
- Explain principles of operation of a silicon photovoltaic (PV) cell, PV balance of system components, passive solar systems, and PEM fuel cells and electrolyzers
- Form a mathematical model of the I-V characteristics of a PV cell
- Connect PV modules in such a way as to match a required load or battery voltage
- Formulate mathematical models of thermal performance
- Match systems to building and location requirements
- Calculate and explain key economic figures of merit of solar systems
Community needs met by the projects:
- UTEC used the analysis to help prepare an application for a grant from the Massachusetts Technology Collaborative for photovoltaic modules for the new building.
- The carbon offset credit analysis was delivered to Staples.