Resilient minigrids using PV and biofuels

We are developing software tools to help design minigrids optimised for developing countries. In particular, the minigrids must be resilient to weather and climate, provide predicable generation, with a long maintenance-free lifetime. Solar PV and biofuels are the primary energy sources, although this will depend on the local resource. Batteries will not have a major role because of their limited lifetime, expense, and susceptibility to theft. Instead, biofuels are used to store energy chemically and provide dispatchable generation.

We will present an overview of the project, details of existing and planned solar irradiance monitoring at partner universities in Africa (Uganda, Congo-Brazzaville, and Tanzania), and initial irradiance datasets. Low-frequency high-accuracy data will be recorded and used to quantify errors in wide-area indirect datasets, such as data available through PV-GIS. There are very limited ground-based pyranometer measurements in East Africa, with no operational BSRN stations. High-frequency low-accuracy data will be recorded and later used as an input dataset for simulations and lab-based operational minigrids. The logging frequency is sufficiently high to capture cloud-edge events occurring on sub-second timescales. Spikes in irradiance and high ramp rates can cause grid instability and potentially damage inverters and other power components.

An existing monitoring station at CREEC, Kampala, Uganda, has been recording irradiance for 6 months. The station includes an LP02 Pyranometer (ISO-second-class) and a triplet of silicon sensors spaced at 5 m. Data is recorded at 10 Hz, allowing irradiance ramp rates and cloud-edge reflections to be captured by the silicon sensors. Using cross-correlation, cloud speed and direction are calculated from the time shifts of cloud edges detected from sensor pairs. Cloud speed and direction govern the dynamic nature of irradiance, and hence the electrical output of PV modules and arrays.