Data acquisition aids construction of mobile health clinics

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Monitoring the construction methods of solar and wind-powered mobile health clinics in Malawi, Africa, to optimise manufacturing of mobile facilities in the region, is being carried out using data acquisition equipment from National Instruments. David Kennedy and Kenny Cameron of the University of West of Scotland explain

Data acquisition aids construction of mobile health clinicsLack of developed health care facilities and a poorly developed electrical distribution network to rural areas present challenges in the Republic of Malawi in South East Africa. At the remote health clinic manufacturing facility, mobile clinics or other mobile organisations can be manufactured, outfitted with appropriate interior equipment, and equipped with solar, wind, or microhydroelectric generating equipment. Currently, one remote health clinic facility prototype is located in Makata, a small village in Malawi.

Makata's clinic is designed as a basic workspace with counter surfaces, an examination/treatment bed, a sink, cupboards, and a refrigerator/freezer. The key elements that power this facility include a 2 kW array of solar photovoltaic panels, a charge controller which is required for every solar installation, an inverter which is also required for every installation where the output is required to be 240V AC, and a small-scale Renewable Devices Swift Wind Turbine.

We worked with a group of Malawian engineers to build a second clinic using tools, materials, and equipment that were available locally in Malawi. With this partnership, we had a reliable supply chain established for items that could not be locally sourced.

To provide key specifications for a new system, we needed to understand the efficiency of the remote health clinic manufacturing facility in Makata. We acquired detailed knowledge of the amount of electricity the mobile unit consumed and the amount that the facility could generate. To acquire this data, we used the NI cDAQ 9172 8-slot chassis with the NI 9205 32-channel analog module and the NI 9211 4-channel thermocouple module. We set up the system with a dedicated laptop to monitor voltages and currents produced by two solar arrays and a wind turbine.

This system also monitored the current drawn by the 2kW inverter and the amount of current wasted as heat. In addition, we monitored wind speed and ambient and battery temperature to understand fully the working environment and better plan the construction of mobile remote health clinic facilities in the future.

Data displayed a significant amount of generated current wasted as heat during the hottest part of the day. With this information, we reduced the size of the solar array from 2 to 1.5kW for the second clinic to reduce the amount of excess energy. We are also investigating the possibility of using the wasted energy for other tasks such as pumping and heating water.

Matching energy supply to critical loads

After observing that the battery charge diminishes over several days, we used a range of preferential electrical trips to limit the energy supply to critical loads when the battery voltage starts to fall. At the same time, we increased the battery storage by 25 per cent to ensure that the clinic has power during all types of weather conditions. Using the reliable data from the DAQ system over a long monitoring period, we made these decisions and introduced more ideas for future development. Furthermore, we have plans to scale the DAQ system, modify it to fit future systems, and use it as a diagnostic tool to identify faults and problems with existing or new solar or hydro installations.

We continued to work with Malawian engineers and recently completed construction of the second clinic in Scotland. We built the new facility under Malawi manufacturing specifications and we will then ship the system to Malawi. Also, funding is in place for the engineers from the Malawi Polytechnic of the University of Malawi to construct a third clinic using the maximum amount of locally sourced materials and equipment. We plan to redeploy the DAQ system to the third clinic to monitor the performance of locally sourced equipment such as the lead acid batteries, which will significantly reduce the cost of the clinic.

Now, the next steps in optimising the remote health clinics are to build on the support infrastructure, which is the subject of a new funding bid that we have submitted to the Scottish Government in partnership with the Malawi Polytechnic, as well as a mobile-phone-based monitoring system for off-grid electrical generation systems.

The DAQ system was easy to use and gave us confidence in finalising the specifications for the new remote health clinic. The new facility has been in operation for more than one year, and we have a very clear concept of how the remote health clinic facility functions and uses energy under all types of weather conditions.

21 December 2009

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