Solar Power Data-Logger

The Renewable Energy for Development group, part of The Centre for Renewable Energy Technology within Loughborough University, work on access to energy services for the 1.3 billion people without access to reliable energy supplies.

They were working on mini-grid projects based in Kenya and in Bangladesh.

These solar PV systems provided renewable energy for communities of up to 500 people. These systems provide lighting, phone recharging, food processing and egg incubation.

The operation of these mini-grids needed to be remotely monitored for maintenance issues and to provide data for research into the use of the systems.

Solution

RE-Innovation designed and produced a bespoke data-logging unit which recorded the main system parameters, stored the data to a local SD card and uploaded the data for online monitoring.

We provided four data-loggings systems which are fully self-contained with solar charging facility, GPS for location sensing and with a GPRS connection (with a valid SIM card) for uploading data to an online database and also for sending operation and maintenance texts.

The units needed to measure the DC output from two 1.5kW solar PV arrays. This provided energy which is stored within a central battery bank. We also measure the DC current to the various loads on the system (up to 6 loads circuits in total)

A total of 8 DC currents are recorded using hall-effect current transducers. 2 isolated DC voltages are also measured, along with 3 temperatures, using thermistors.

The loggers needed to be easy to install within the system (as the main power system was installed by a local solar PV company), so we used DIN rail mounted connection blocks within a IP65 rated wall-mounted cabinet, along with a comprehensive installation manual.

A 2Wp solar PV module recharges a small LiPo battery bank within the loggers for local power supply. The power can also be fed directly from the battery banks within the system.

The loggers are based upon the LinkIt One from Seeed Studio. This unit is based upon the MediaTek Aster (MT2502) system-on-chip processor and has GPS, WiFi and GPRS capability. It also includes an SD card slot for data-logging. It is very low cost for these features and also has an open-source library for using most of the functions on the board.

We designed a break-out PCB for mounting, power management and for the various measurement sensors, including hall-effect sensors, isolated voltage sensors and temperature sensors.

The circuit board is available for download here.

The data-logger code is available here.

Two of these units have now been installed at sites in Kenya and are uploading information for detailed analysis and research use.