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Photovoltaic (PV) Systems

Photovoltaic panels in Rwanda. (Photo: Jeff Haeni)

Photovoltaic (PV) Systems generate electricity from sunlight collected by solar panels. Energy collected in this manner can be used to supply direct power to electrical equipment, or it can be stored in batteries to provide indirect power.

In combination with a battery, PV systems are excellent for handling small-to-moderately sized loads in locations where grid electricity is not available. Solar/diesel hybrid systems offer many advantages to solar-only systems for many off-grid small and medium sized health facilities. They are highly modular, so it is easy to customize the system to your needs and add units if your power demand increases. Photovoltaic systems provide DC (direct current) power. Inverters, which convert this DC power to AC power, must be added to most systems powering medical equipment used in health clinics.

PV systems are rated in terms of the peak power (in watts or kilowatts) they can produce. This is multiplied by the peak sun hours (PSH) factor to determine the energy (in kilowatt-hours) produced each day. An optimal setting in Africa might receive the equivalent of five or more hours of peak sunlight per day. In this case, a 1-kW system would produce 5 kWh per day. There is always some loss of power from rated output, so it is common to increase system sizes by 20 percent over the rated load to ensure power supplies are sufficient to meet the identified needs.

Cost Considerations

Depending on the size of the system, installed PV systems can cost $8.00-12.00/watt. However, unusual expenses such as transportation of modules, customs fees, or permitting expenses can increase this cost. If the system has no other backup, the battery must be sized appropriately to provide power after several days of overcast weather; therefore, local weather patterns can influence overall system cost. In a hybrid configuration, the batteries can be much smaller since the generator can take over if there are prolonged cloudy periods.

Maintenance Considerations

The panels themselves typically have a very long lifetime (20-30 years). Unfortunately, installation programs do not always include a sufficient service component. Health Facilities with solar panels must have a vigorous training program for local users and maintenance protocol. Regular maintenance on batteries is essential; they should be checked every week, with the electrolyte level replenished as needed, and if properly maintained, should last several years before needing replacement. While training local hospital staff in system maintenance is essential for routine maintenance, a professional technician should also perform a semi-annual maintenance check, examining wiring connections, mounting bolts, and inverter operation and be on call to fix the system if it does not work. Maintenance funds should be established upfront and be dedicated only to solar system repair. Mixing maintenance funds with general operating budgets has proven to be an ineffective model.

Additional Resources

These are links to external publications and Web sites that have information on issues related to providing reliable electricity and energy services at health facilities. USAID and Powering Health make no warrantee or guarantee regarding these external resources, and the organizations hosting these resources are solely responsible for their content.