Solar Car Race

Currently, solar energy makes up only a tiny fraction of our energy used in the U.S.

From 2010 Colorado Utilities Report In Colorado, solar and other forms of renewable energy are being used more and more for electricity generation. Colorado has the second most aggressive renewable portfolio standard in the U.S. which says that by 2020, our investor-owned utilities (Xcel and Black Hills) must generate 30% of their electricity from renewable sources. Other utilities such as rural electric associations and municipal utilities must generate 10% of their electricity from renewables by 2020. Xcel Energy plans to achieve this goal as early as 2013, although in-state and customer-owned renewables are weighted more heavily in the 30% calculation.

How Solar Works A photovoltaic cell works by having 1 positively charged chemical layer and 1 negatively charged chemical layer. When photons from sunlight hits the cell, electrons flow from the semiconductor into the load (i.e. an appliance). Multiple cells strung together from a module (panel) and modules strung together form a solar array.

Energy is a function of power times time and is measured in watt-hours, kilowatt-hours, or even mega- and giga-watt hours. Power is a function of volts times amps and is measured in watts. Volts measure the pressure of electrons moving through a wire. The higher the pressure, the greater the voltage, similar to water falling a short distance (low voltage) versus water falling a long distance (high voltage). Amps measure the volume of electrons moving through a wire. The higher the volume, the greater the amperage, similar to water flowing through a full small diameter pipe (low voltage) versus a full large diameter pipe (high voltage). For solar, greater voltage results from more sunlight and cooler temperatures. Current is a function of sunlight (insolation). Voltage Amperage

Sunny Days Colorado has an excellent solar resource, averaging about 5.5 “sun hours” per day (where 1000 watts of solar energy are available per square foot).

Location, Location Mount type 10 watts per square foot Usable roof space Tilt, azimuth It’s important to have a properly installed array to take advantage of the solar resource. Panels can be mounted on roofs, on the ground, or on poles, and thin-film solar panels can be integrated into roof shingles (bottom)! In general, rooftops in Colorado can generate 10 watts of solar energy per square foot, depending on tilt and azimuth. For fixed systems that don’t track the sun, a tilt equal to one’s latitude will generate the most electricity over a given year. An azimuth of true south (about 180 degrees) will also generate the most solar electricity over a given year. Solar panels can typically convert about 20% of the sun’s energy into useable electricity.