A SPIS is a clean and sustainable irrigation technology that utilizes solar energy to pump and distribute water for agricultural use. As water scarcity and unreliable energy access continue to challenge agricultural productivity, SPIS offers a sustainable alternative to the most common irrigation systems by reducing dependence on fossil fuel sources, preventing from the consequences of their volatile prices. By replacing diesel- or gasoline-powered pumps, it lowers greenhouse gas emissions, reduces air pollution, and generates significant cost savings for farmers.

Beyond lowering operating expenses, SPIS also supports more consistent and productive farming: it is one of the best-studied solutions for improving smallholder farmers’ livelihoods, as access to modern irrigation can substantially increase yields, with case studies showing improvements of up to two- to three-fold (Efficiency for Access, 2019). This reliability enables year-round cultivation, leading to higher crop output, greater diversification, and improved farmer incomes (Schneider S., Raabe M. et al., n.d.).

SPIS is suitable for a wide range of irrigation scales, from small household gardens to large agricultural fields. It is particularly suitable for adoption in rural areas with limited access to electricity and abundant solar radiation, offering an affordable solution to increase agricultural productivity.

Solar cooling systems are generally divided into two types: passive and active.

Passive solar cooling does not use any mechanical devices or electricity. Instead, it relies on smart building design and natural processes to keep spaces cool. For example, buildings can be designed to have proper shading, reflective roofing materials, and good air flow through windows or vents. These methods help to reduce indoor heat without using any machines. They are simple, cost-effective, and very useful, especially in areas where access to electricity is limited.

Active solar cooling, on the other hand, uses technology and equipment to convert solar energy into usable power that runs cooling systems as described below. The three main types of active solar cooling include:

1. Solar absorption cooling, which uses solar-heated fluids to run absorption chillers; the chiller cools air by using a mix of fluids that work together – often lithium bromide and water. It’s good for places with strong sunlight and large cooling needs.
2. Solar ejector cooling, which relies on solar thermal energy to power ejectors that produce cooling through pressure differences.  This system uses solar heat to drive a jet ejector – a simple device that compresses and expands a gas (called a refrigerant) to make it cold. Because of its simplicity, solar ejector cooling is best for small-scale uses like rural homes or remote clinics.
3. Solar desiccant cooling, which removes humidity from the air using solar-regenerated drying materials (desiccants, like silica gel). This method is ideal for hot and humid climates.

Note: The three techniques outlined above represent the different systems of active solar cooling. However, for those systems to work, they must be powered by solar energy. Section 1.1 explains the fundamental ways these systems are powered using two main approaches: solar electric and solar thermal to supply the required energy to run these cooling systems.