How do you design a solar thermal system for water purification in remote areas?

1 The basic principle

A solar thermal system for water purification works by using the sun's heat to evaporate water from a contaminated source and condense it as clean water in a separate container. The process removes bacteria, viruses, parasites, salts, metals, and other impurities from the water, making it suitable for drinking, cooking, or irrigation. The system can be set up in any location that receives enough sunlight and has a water source, such as a well, a river, or a pond.

2 The main components

A solar thermal system for water purification consists of four main components: a solar collector, a basin, a condenser, and a storage tank. The solar collector is a device that absorbs and transfers solar heat to the water. It can be made of metal, glass, plastic, or other materials that have high thermal conductivity and low emissivity. The basin is a container that holds the contaminated water and exposes it to the solar heat. It can be made of any material that can withstand high temperatures and corrosion. The condenser is a device that cools and collects the water vapor that rises from the basin. It can be made of metal, glass, or plastic tubing that is coiled or shaped to increase the surface area for condensation. The storage tank is a container that stores the purified water and prevents it from being recontaminated. It can be made of any material that is durable, leak-proof, and easy to clean.

3 The design process

Designing a solar thermal system for water purification requires you to consider several factors, such as the water demand, quality, and solar radiation. To begin, estimate the daily water demand for your intended use and population to determine the size and capacity of your system. Test the water quality of your source to identify contaminants and concentrations. Measure the solar radiation and ambient temperature in your location to optimize the orientation and insulation of your system. Choose materials and components based on availability, cost, performance, and durability. Consider using locally sourced or recycled materials to reduce environmental impact and maintenance cost. Assemble and install your system according to instructions and safety precautions of your chosen design. Monitor and evaluate regularly to ensure efficiency and reliability by assessing indicators such as temperature, flow, quality, and system performance.

4 The benefits and challenges

A solar thermal system for water purification has many benefits, such as using renewable and free energy from the sun to reduce dependence on fossil fuels and electricity, providing clean and safe water for various purposes, and being simple and low-cost to build and operate. It is also adaptable and scalable to different needs and conditions. However, it depends on the availability and intensity of sunlight, requires regular cleaning and maintenance, has limited storage capacity and distribution options, and may face social or cultural barriers to acceptance or adoption.

5 The examples and resources

If you are interested in designing a solar thermal system for water purification, you can find many examples and resources online that can inspire and guide you. For instance, the SODIS method uses transparent plastic bottles to disinfect water with solar heat and ultraviolet radiation. The WADI device measures the solar radiation and indicates when the water in a transparent container is safe to drink. The Solvatten unit is durable and reusable, treating up to 11 liters of water in two to six hours of exposure to sunlight. The Solar Water Pasteurizer uses a solar collector and heat exchanger to pasteurize water, killing up to 99.999% of harmful microorganisms. And the Solar Still uses a solar collector and condenser to distill water, removing up to 99.9% of dissolved solids and contaminants. Additionally, you can find more information on how to design a solar thermal system for water purification from resources such as the Solar Cooking Wiki, the Solar Water Disinfection Handbook, and the Solar Water Purification Project.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?