Briefly describe how a photovoltaic solar array is made up. Differentiate between monocrystalline panels and polycrystalline panels in terms of efficiency and cost of production.

Here are the solutions to the questions:

1. Briefly describe how a photovoltaic solar array is made up. A photovoltaic (PV) solar array is made up of multiple solar panels (also called modules) connected together. Each panel consists of many individual solar cells (typically silicon-based) that convert sunlight directly into electricity. These panels are mounted on a support structure and wired together, often in series and parallel, to achieve the desired voltage and current output.

2. Differentiate between monocrystalline panels and polycrystalline panels in terms of efficiency and cost of production.

   • Monocrystalline Panels:
     • Efficiency: Generally higher efficiency (17-22%) due to the use of single, pure silicon crystals, allowing electrons to flow more freely.
     • Cost of Production: Typically more expensive to produce because the manufacturing process for growing single-crystal ingots is more complex and energy-intensive.
   • Polycrystalline Panels:
     • Efficiency: Generally lower efficiency (15-17%) compared to monocrystalline panels because they are made from multiple silicon crystal fragments, which creates grain boundaries that impede electron flow.
     • Cost of Production: Typically less expensive to produce as the manufacturing process is simpler, involving melting and cooling silicon fragments.

3. What are the four main components of a stand-alone PV system? The four main components of a stand-alone (off-grid) PV system are:

   • Solar panels (PV array): To convert sunlight into DC electricity.
   • Charge controller: To regulate the voltage and current from the solar panels to the battery, preventing overcharging or deep discharging.
   • Battery bank: To store excess electricity generated by the panels for use when the sun is not shining.
   • Inverter: To convert the DC electricity from the battery bank into AC electricity for household appliances.

4. What is the optimal angle for annual energy production for a solar array in Durban in winter? For optimal annual energy production, the tilt angle of a solar array is typically set equal to the latitude of the location. Durban's latitude is approximately $29.86^\circ$ South. For optimal winter production, the tilt angle is usually increased by about $15^\circ$ from the latitude. Optimal winter angle $\approx \text{Latitude} + 15^\circ = 29.86^\circ + 15^\circ = 44.86^\circ$. The optimal angle for a solar array in Durban in winter is approximately $\boxed{45^\circ}$ (tilted towards the north).

5. Briefly describe how a grid-connected PV system works. In a grid-connected PV system, solar panels convert sunlight into DC electricity, which is then fed into an inverter. The inverter converts the DC electricity into AC electricity, which is synchronized with the utility grid. This AC power is then used to power the home's electrical loads. Any excess electricity generated is fed back into the utility grid, often earning the homeowner credits (net metering), while insufficient power is drawn from the grid.

6. What are three key considerations with regard to the environmental impact of a PV system? Three key considerations regarding the environmental impact of a PV system are:

   • Resource extraction and manufacturing: The production of solar panels requires mining of raw materials (e.g., silicon, rare earth metals) and involves energy-intensive manufacturing processes, which can lead to habitat disruption and greenhouse gas emissions.
   • Land use: Large-scale solar farms require significant land area, which can impact ecosystems, agricultural land, and local biodiversity.
   • End-of-life waste and recycling: Solar panels have a lifespan of 25-30 years, and their disposal at the end of life can create electronic waste. Proper recycling infrastructure is crucial to manage these materials and prevent hazardous substances from entering landfills.

7. List two advantages and two disadvantages of solar energy.

   • Advantages:
     • Renewable and sustainable: Solar energy is an inexhaustible resource, reducing reliance on fossil fuels.
     • Low operating costs: Once installed, solar panels have minimal maintenance and no fuel costs.
   • Disadvantages:
     • Intermittency: Solar power generation is dependent on sunlight, meaning it doesn't produce electricity at night or during cloudy weather.
     • High initial cost: The upfront cost of purchasing and installing solar panels and associated equipment can be substantial.

8. What is the main function of a heliostat? The main function of a heliostat is to track the sun's movement and reflect sunlight onto a central receiver or collector. Heliostats are typically large, flat mirrors used in Concentrated Solar Power (CSP) systems to focus solar energy, generating high temperatures.

9. Describe how a CSP system is used to generate electricity. A Concentrated Solar Power (CSP) system generates electricity by using mirrors (like heliostats or parabolic troughs) to concentrate sunlight onto a receiver. This concentrated sunlight heats a heat transfer fluid (e.g., molten salt or synthetic oil) to very high temperatures. The hot fluid then transfers its heat to water, producing high-pressure steam. This steam drives a turbine, which in turn spins an electrical generator to produce electricity. The steam is then condensed and recycled.