Intro to Renewable Energy

Here at Sunelco we understand that not everyone who wants to live with a solar or renewable energy system is going to be already trained in the fundamentals of electricity. We also know that there are students who are researching the topic for classroom projects and that other folks want to learn for the simple intrinsic value of having more knowledge on the subject. For this reason we created the Renewable Energy Classroom in hopes that it will get extensive use and help this generation of enthusiasts become more familiar with today's renewable technology.

How do solar cells generate electricity?

Simply put, photovoltaics or PV for short can be thought of as a direct current (DC) generator powered by the sun. When light photons of sufficient energy strike a solar cell, they knock electrons free in the silicon crystal structure forcing them through an external circuit (battery or direct DC load), and then returning them to the other side of the solar cell to start the process all over again. The voltage output from a single crystalline solar cell is about 0.5V with an amperage output that is directly proportional to cell’s surface area (approximately 7A for a 6 inch square multicrystalline solar cell). This is not enough to do any appreciable work so typically 30-36 cells are wired in series (+ to -) in each solar module. This produces a solar module with a 12V nominal output (~17V at peak power) that can then be wired in series and/or parallel with other solar modules to form a complete solar array to charge a 12, 24 or 48 volt battery bank.

Will Solar work in my area?

Solar is universal and will work virtually anywhere, however some locations are better than others. Irradiance is a measure of the sun’s power available at the surface of the earth and it averages about 1000 watts per square meter. With typical crystalline solar cell efficiencies around 14-16%, that means we can only expect to generate about 140-160W per square meter of solar cells placed in full sun. Insolation is a measure of the available energy from the sun and is expressed in terms of “full sun hours” (i.e. 4 full sun hours = 4 hours of sunlight at an irradiance level of 1000 watts per square meter). Obviously different parts of the world receive more sunlight than others, so they will have more “full sun hours” per day. We have a “Solar Radiation Data Manual” that lists the average number of full sun hours per day throughout the year for 239 cities across the United States for both stationary and tracking mount structures. We use this data along with your electrical load information to accurately size a photovoltaic system to meet your needs.

Since the study of Renewable Energy (RE) requires knowledge of both Alternating Current (AC) and Direct Current (DC) electricity, we have created a section entitled Basics of Electricity which will give you some entry-level information on the fundamentals of electricity. This information is applicable to both DC (battery type) electricity and AC (wall outlet) electricity.


Sloop Story

Mr. Paul Riggs of Stockton, California saw solar power as a natural fit for his sloop - why not take advantage of all that sun while out on the water?

Paul mounted four Kyocera 120 watt solar modules above the wheelhouse of his boat. The 480 watt solar array charges a bank of five 213 amp hr. batteries, which in turn, provide him with enough power to run a refrigerator, freezer, all the lights and the autopilot. Now Paul can spend his days on the water without the need to plug into shore power or starting an engine.