CASE STUDY SYSTEM 3

Small Solar Home System or Caravan System

System Design Brief

This is a typical solar home or caravan system that will provide a few 12 V DC loads.  The appliances typically used in these systems include a radio, a fan and lights.  The average daily energy use was calculated to be 130 Wh/day using the information supplied by the client.  No significant seasonal load was identified in the load assessment. (see Energy Calculation Worksheet).  These solar home systems also represent one category of systems typically used for Rural Electrification (see Rural Electrification).

System Sizing

In preparing the system design in 2000 the method used was as outlined within the then Draft standard AS4509.2.  In 2002 the AS4509.2 standard was published.  The installation of the system complied with part 3. (See System Sizing Worksheet)

System Installation and Specifications

The installation of this modified system was completed in late 2006 and is comprised of the following major components:

Battery Charge Controller The battery charge controller or regulator ensures the electricity from the photovoltaic array going into the battery bank has the correct voltage or current to charge the batteries.  It detects the state of charge of the batteries and decides the appropriate charging current. The regulator is a Morningstar model “SunLight-10”.  It is rated PV current & Load current of 10 Amp at 12 V DC.

Battery Bank The battery bank enables the system to provide electricity anytime during the day. It is used to store excess energy generated by the PV array during the day, which can then be used to supply energy during the night. The battery used is a 12 V stationary lead acid battery type “OGi 50 LA”. It has a total rated capacity of 50 Ah at the C10 rate. These batteries were chosen to provide 360 Wh of usable storage at a maximum depth of discharge of 60%. This is equivalent to three days of average energy use for this system. These batteries require their electrolyte to be regularly checked and topped up with distilled water.

DC Switchboard This box houses the DC circuit breakers. It allows each DC component to be isolated. For the purposes of the display this box also houses meters that allow you to see where energy is being supplied from and where it is going. You can see the battery voltage and current, as well as the PV array current.

System costs

The following table contains the costs of the various system components as at January 2002. These costs are based on the recommended retail prices of the equipment (or similar) from the Western Australian suppliers. All prices include GST.

Rural Electrification

Over the last decade grid-connected photovoltaic (PV) systems have become more popular in the developed countries whilst small to medium scale stand-alone PV systems are more prevalent in developing countries..  Around one percent of every new household accessing electricity in developing countries incorporates some PV technology into their electrical system (Nieuwenhout et. al., 2001).

The major components of a household rural PV electrification system include the PV array, a lead-acid battery bank, a battery charge controller, an inverter and a backup diesel generator. These small systems are used to power domestic appliances such as lights, TVs, radios, mobile phones and computers (Wimmer, 2007). 

Larger community scale systems are used to power the equipment used in schools, community centres, health facilities, religious/worship centres and shopping markets.  Electrification gives people access to a range of energy services that were previously not accessible to them. These energy services often include pumping for access to clean water, machinery to reduce the physical labour in rural commercial production and clean cooking and lighting services for use at home. Electrification increases the capacity of regional essential health and education services, increases efficiency in commercial production and allows the rural community to enjoy cultural activities through increased opportunities for leisure.

Van der Vleuten (2003) has proposed three different types of energy technologies to better suit the diverse needs of the rural electrification markets in different countries:

• Large scale centralised energy systems,
• Decentralised independent energy systems, and
• Network of energy systems based on multiple energy technologies 

These three systems are envisaged to greatly assist in the electrification process of rural and remote regions in developing countries, with large populations representing a substantial market for PV technologies (Hankins, 2001; Lorenzo, 2000).

To create a sustainable market in rural regions of developing countries "infrastructure is needed to provide the end-user with hardware, information and services. This requires a dense network of local entrepreneurs, including importers, distributors, technicians and shopkeepers” (Van der Vleuten, 2003).  A basic education of users about the system ability and limitations together with the general maintenance of the system components is of the utmost importance to the successful long-term operation of sustainable rural electrification programmes in developing countries.

References

Hankins, M (2001), Commercial Breaks - Building the Market for PV in Africa. Renewable Energy World, Issue  Jul-Aug 2001, pp. 164-175.

Lorenzo E (2000), In the Field – Realities of Some PV Rural Electrification Projects, Renewable Energy World, Issue Oct. 2000, pp. 38-51.

Nieuwenhout F et. al. (2001), Experience with Solar Home Systems in Developing Countries: A Review. Prog. Photovolt. Res. Appli., 9, pp. 454-474.

Van der Vleuten F (2003) Selling Rural Electrification – Developing Solar Market Infrastructure in Africa and Asia.  Renewable Energy World, Issue  Nov-Dec 2003, pp. 90-101.

Wimmer N (2007) Digital Development – Innovations Push Rural Electrification. Renewable Energy World, Issue  Jan-Feb 2007, pp. 94-101.

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