Sunlight reaches the Earth via photons, particles that are created at the sun’s core through atomic fusion. It takes them a million years to migrate from the center of the sun to its surface, and just 8 minutes to reach the planet from more than 93 million miles away. According to NASA, the sun produces an amount of energy equal to 5 x 1023 horsepower and the amount captured by Earth has been calculated to about 1.8 x 1017 Joules per second. These numbers are staggering, however, sunlight can be safely converted to energy through solar power.
The first step of the process occurs every second of every day. The next part requires solar cells. Solar panels are required to convert sunlight into energy; if placed on a roof, they should be ideally placed where there’s no shade and face a direction that allows for the most exposure. With a 36-cell panel, the entire surface area must receive sunlight. It will only produce half as much power even if just one of its cells is shaded. Advanced photovoltaic systems will track the sun as it moves across the sky (as the Earth rotates), so the orientation of the panels will shift according to where the light is coming from.
Process of Solar Power Energy Production
Sunlight strikes the silicon surface on a photovoltaic cell, which has a positive and negative film. Photons pass through an outer layer of glass and hit the silicon cells. When they do, negatively charged electrons naturally shift to one side, generating an electric voltage. But pure silicon doesn’t work well as a conductor due to its atomic structure. It is crystalline and has three layers of electrons – the total number of electrons is 14.
There is always an even number of electrons in each layer, except when energy is introduced. Some electrons then break free and migrate to places in the atom where others have moved from. The motion of electrons generates electricity. Solar cell manufacturers introduce impurities (atoms such as boron or phosphorous) to maximize the number of electrons that can be freed, which increases energy conduction.
The voltage generated is a usable current. Each solar panel in an array is connected by wiring, which enables the current to be gathered and channeled to a terminating point. Multiple cables end at a fused array combiner, a type of electrical box that contains fuses to protect parts of the array. The electricity produced up until this point is direct current (DC).
Where Solar is Most Commonly Used
Devices and appliances used by homes and businesses, however, require alternating current (AC). The electricity is converted using a device called an inverter. Solar power inverters make the energy produced usable so it can be consumed, supplied to the power grid, or used to power up a battery. Usually mounted outside a house near the main electrical panel, an inverter converts electricity into 120-volt AC power. This is energy that can be immediately used.
Other components are connected to the inverter. These include an electricity production meter and a net meter, which work together to enable power to be first consumed by electrical loads in the building. This configuration also has benefits when more electricity is produced than used. Net-metered power means power from the utility is reduced, lowering utility bills but during an outage, the system will turn off automatically so workers are protected.
Grid tie solar systems deliver energy to appliances and other systems that consume it. Excess electricity is fed back to the power grid. On the other hand, the system will draw energy from the grid if electricity isn’t being produced by the solar system. Most photovoltaic systems are tied to the grid, while off-grid ones direct the energy to a rechargeable battery. This storage system is located past the inverter. The solar cells provide a direct charge, so excess energy can be drawn from the battery as long as it is available.
Climate and Energy Production
The power produced by a solar photovoltaic system is affected less by climate than by shading. There primarily needs to be direct access to sunlight. Air temperature has less of an effect on efficiency. Even if there is snow, the exposure to sunlight is able to melt it quickly.
However, as temperatures rise, efficiency is reduced. Output efficiency can be cut 10 to 25 percent at temperatures above 77°F, depending on where the panels are installed. Given the exponential increase in output current and linear reduction in voltage produced, the outside temperature can be gauged. Nonetheless, each type of solar panel has a unique tolerance to heat. Panels are assessed to determine their Standard Test Condition temperature, which is a benchmark to see how much power one loses when the temperature is raised by 1°C above 25°C. Manufacturers include this data with each panel they sell.
To Maximize the Energy Produced by Rooftop Solar Power Systems:
Raise the rooftop panels by a few inches to allow air to flow around them and cool things down.
Choose arrays with lighter colored materials, which absorb less heat so the panels stay cooler.
Move inverters and combiners that generate heat away from the array, so it doesn’t transfer to the panel materials.
Technologies that Enhance Solar Energy Production
Today’s solar technologies go beyond silicon cells and net metering. Concentrating solar power systems add mirror panels and other types of reflective components. These produce heat that contributes additional electricity to the system. Solar water heating systems are also popular. Facing the sun, the solar collector can heat water directly, or add heat to another fluid that transfers it to water in the system. Solar energy can also be used to preheat air ventilated into a building using transpired solar collectors. Various applications for solar power exist, from an inexhaustible energy stream that comes from tens of millions of miles away.
Sources: Solar-energy-for-homes.com, NASA, NW Wind and Solar, Gosolarcalifornia.ca.gov, Civicsolar.com