Solar energy is radiant energy from the sun. More solar energy falls on the earth from the sun in one hour than the world uses in one year!
Turning that energy into useful energy is the challenge. Several technologies have been researched, tested and are in use today with more coming in the future.
Passive Solar – Depending on the location, a home or building can be positioned to best utilize the direct sunlight as heat in winter and to keep heat out in summer. Green building designs make the most of this low-tech solution.
Photo courtesy of South Sound Solar
Solar Photovoltaic (PV) - When the sun shines onto a solar panel, photons from the sunlight are absorbed by the cells in the panel, which creates an electric field across the layers and causes electricity to flow. Solar PV was first used in outer space where burning fuel is prohibited because of the lack of oxygen. NASA’s research into PV led the way to today’s rooftop solar revolution. Solar PV creates direct current (DC) electricity that is converted to AC, by a power inverter, before it is connected to the grid. Solar panels are composed of cells made usually of silicon. Solar panels are wired together into a solar array of varying sizes. When added to existing rooftops, solar arrays have minimal impact on the natural environment.
Photo courtesy of Fire Mountain Solar
Solar Thermal - As you know from feeling the sun’s rays on your skin, solar energy also generates heat. The sun’s rays can be used to heat water either directly or to heat a liquid that then transfers the heat to water to deliver hot water to a home or other use. This technology is often used to heat swimming pools.
Either solar PV or solar thermal technologies can be used on a small scale to power a residence or small business, or on a massive scale as a solar power plant.
Solar Thermal & Concentrating Solar Photos: U.S. Department of Energy
Concentrating Solar Power (CSP) - This technology uses mirrors to reflect and concentrate sunlight onto receivers that collect solar energy as heat which is used to heat a fluid to high temperatures. The fluid transfers heat to produce steam that powers turbines transferring heat energy into mechanical energy. Turning of the turbines generates electricity. The fluid used in CSP can be an oil, molten salt, molten sand or other material that stays in a closed loop. These power plants continue to produce electricity at night because they have so much stored concentrated heat energy. Each mirror has a motor controlled by a computer to angle the reflective surface toward the sun tracking it across the sky. The computer software and/or the motors operating in the desert can have operational difficulties. There are several CSP power plants in California and Nevada deserts. They take up an enormous amount of land space and, like any power plant, generate a lot of electricity. Several different designs exist including dishes, troughs and towers.
Large Scale Solar PV – Power plants made up of very large solar arrays generate electricity to power individual buildings, communities or micro-grids. When paired with a storage mechanism, then the power can be used day or night. Storage of electricity made by Solar PV is a field where significant research is being conducted today.
Emerging Solar Technologies
Research is rapidly advancing to find new ways to utilize the sun’s energy to make electricity, including:
- Thin Film / Flexible Solar Cells
- Solar Roadways