What is Solar Energy?

Solar power

Solar energy is energy derived from the Sun's radiation. The Sun is an powerful source of energy and provides the Earth with as much energy every hour as we collectively use in a year worldwide. It is important that we continue to harness and increase our use of solar energy (and other clean, renewable energies) as fossil fuels become depleted, expensive, and fall out of favor with their consumers.

As the global demand for energy grows and conventional energy resources become increasingly costly to extract, people are looking to the power of the Sun. Solar has been growing exponentially for the last 20 years, while the price of photovoltaic (PV) cells has dropped 20% whenever manufacturing capacity doubles; PV cell prices are 99% lower now than they were in 1976. It is no longer the cost-prohibitive energy source it once was.

Solar power is important because every beam of light that we can convert into electricity is another step in reducing our dependence on polluting fossil fuels. Also by investing in the clean energy economy, we can help ensure energy security right here in America and create millions of jobs without the need to outsource. Each year more and more people are investing in their own energy portfolios by installing solar panels on their homes, but not everyone has that option (e.g. due to home ownership, geographic location, home orientation, etc.). For the latter, Mosaic allows people to become investors in solar projects to earn competitive returns while also helping out the environment.


When one thinks of solar power, PV or solar panels come to mind. Even within the category of PV there are many applications and variants of the technology, but fundamentally, PV enables us to directly convert sunlight into electricity. Semiconductor materials (like those used in computers) make up solar cells and are used to convert photons (e.g. light) to electricity. PV arrays consist of solar cells which can come in a variety of shapes and sizes. The PV array on a house generating electricity is likely made of traditional crystalline silicon. Alternatively, thin film solar utilizes stacked semiconductors only a few micrometers thick that can be applied as roof shingles or solar window tinting to generate electricity. What thin film gains in versatility and price reductions, it loses in terms of conversion efficiency. Typical solar cells have an efficiency of around 15%, although there are models that are up to 21% efficient.

Concentrated Solar Power

Concentrated solar power is not a type of energy that can be installed on top of one's home or building. It requires the use of many mirrors across a broad expanse of land that focuses the power of the Sun on a fixed tower. The tower contains salt that is heated by the concentrated sunlight where it functions similar to a battery to store heat and generate steam after the Sun sets. The design can also be altered so that parabolic trough-shaped mirrors can concentrate sunlight onto a tube containing fluid, generating steam and then electricity.

Active & passive solar heating

Passive solar can be used to heat a building. By constructing a building with large south-facing windows, the Sun's energy can be captured during the day. Certain thermal storage materials can absorb the heat and slowly dissipate it throughout the night keeping the building warm. Thermal storage materials like adobe have been used to construct buildings for thousands of years.

Active solar heating is another way to make use of the Sun's radiant energy. An example of active solar is solar water heaters. These systems can be found on top of many buildings throughout the world. Water slowly passes through a flat plate collector facing the Sun and as the water is heated, it flows into a storage container to be used later. In some Mediterranean countries, 30-40% of all homes have solar water heaters, highlighting the effectiveness of such a system to meet basic household hot water needs.