Solar/Battery Powered Clinic for Australia's Remote Areas

by A Zahedi, Monash University, Australia

Click here to see a diagram

Introduction

When it comes to remote areas, Australia has some of the most inaccessible in the world. This article investigates the possibility of building a photovoltaic/battery system to power nursing clinics in remote areas where reliable electricity supply is not available through the grid. The system has been designed and will be built and evaluated at Monash University.

Background

A remote nursing clinic's main electrical load is a vaccine refrigerator, which requires the highest priority. Other loads, such as lights and fans, are considered to have lower priority. A vaccine refrigerator requires an extremely reliable power supply and the entire system needs an accurate charge and discharge controller. Because of the remote location, quick replacement of the electrical components is difficult, therefore any failure can put the refrigerator system out of operation. The result is spoilage of the vaccines and, consequently, unnecessary illness of patients.
 To increase the reliability of supply, the photovoltaic/battery system uses two separate battery strings. One battery string supports the vaccine refrigerator and the other supports the other loads. The refrigerator battery always has priority and is charged during the day by a photovoltaic panel. Surplus power generated by the photovoltaic panel then charges the auxiliary-load battery. The main refrigerator battery and the photovoltaic panel are sized for the refrigerator load.

Solar Array Selection

In designing photovoltaic-powered health clinics; the technical factors include:

  • load characteristics;
  • photovoltaic radiation availability;
  • location;
  • array configuration.

Two technologies are available: flat-plate cell technology and concentrator module technology. Both are mature technologies which convert solar radiation to electricity in somewhat different ways. Flat-plate cells use both the direct and diffuse components of insolation; the concentrator module technology uses only the direct component.
 A particular location normally lends itself more to one technology than the other, so the selection is a matter of economics. Locations at high elevations receive radiation with less atmospheric scattering. In these areas direct beam radiation can reach the surface. Low-elevation locations receive both direct beam radiation and atmospheric scattering.
 It is also important to select an appropriate tracking system. Active tracking allows the array to track the sun continuously thus it can collect 20-30% more daily solar energy than passive tracking. However, it may be more prone to maintenance problems.

 The System

A diagram of a photovoltaic/battery system is shown above. The solar panel is the main power generating unit. In normal conditions, the solar panel powers the vaccine refrigerator. When more power is generated by the solar panel than is required by the vaccine refrigerator, the excess power is stored in the batteries. In all cases the highest priority is given to the vaccine refrigerator and its battery. The
 12 V dc, 73 litre capacity vaccine refrigerator consumes 20 Ah over each 24-hour period. A simple, programmable logic control device is used as the charge and discharge controller. The solar panel used is rated at 83 W.

Economic Analysis

At present, photovoltaic systems for large-scale power generation have a high initial cost. However, for remote applications, the initial cost of conventional energy sources include many associated capital items such as excavation, wiring, transformers and other associated line-extension costs. Life-cycle cost analysis gives a true measure of cost-effectiveness and should be used as the basis for selecting a specific power system for remote health clinics.
 This whole system costs about $4,000 (where $ is the Australian dollar). Mass production of this system offers an even lower price.

Conclusion

The photovoltaic/battery powered nursing clinic offers a permanent nursing clinic which provides service at low cost in remote areas. But clinics are not the only application for the photovoltaic/battery system. Isolated farms and cattle stations could also benefit, and the technology has potential for export abroad.
 For more information contact the CADDET Australian National Team in Canberra.

The CADDET Renewable Energy Newsletter is a quarterly magazine published by the CADDET Centre for Renewable Energy at ETSU, UK.

The articles published in the Newsletter reflect the opinions of the authors. They do not necessarily reflect the official view of CADDET.

Enquiries concerning the Newsletter should be addressed to
Pauline Toole, Editor, CADDET Centre for Renewable Energy, ETSU, Harwell, Oxfordshire OX11 0RA, United Kingdom. Tel: +44 1235 432968, Fax: +44 1235 433595.