INTRODUCTION

This is a brief overview of solar electric for people who are new to it. It will answer the most often asked questions.

Let's begin with how solar cells work. The technology was developed in the 1950's and has been consistently improved. Cells are made of silicon wafers with embedded wires. When the sun hits these cells, the atoms are bombarded with photons and give up electrons, producing electricity.

The quality and reliability of today's solar panels is evidenced by manufacturers' warranties that extend to 20 years for 90 % of their rated output. Solar panels produce direct current (DC), the only type of electricity that can be stored for later use.

Panel location is important. A site with unrestricted sun from 9am to 3pm is required.

SYSTEMS TYPES

The most basic system is commonly used in cabins without the usual home appliances. It consists of solar panels, charge controller, storage batteries, and a DC Load center. All lighting is DC. Water pumping and pressurization can also be accomplished using DC pumps. Appliances are limited to what is available through the recreational vehicle industry. DC equipment is more expensive and does have some limitations.

More typical systems for remote homes use an inverter in addition to the basic DC system described above. Inverters take battery-stored DC power and convert it to AC power. Modern inverters produce very clean efficient power, making it possible to use conventional appliances and lighting.

SYSTEM SIZING

Before sizing a system, every effort should be made to utilize efficient appliances and lighting to keep the system cost affordable. Propane can be used for refrigeration, cooking, clothes drying, and water heating. Electric refrigerators can be used but need to be the superefficient Sunfrosts or high efficient conventional. Lighting should utilize fluorescent, compact fluorescent, or halogen bulbs.

To size a system, do a comprehensive list of the loads that will be used and length of use each day. Use the Energy Use Reference to do this.

There are many variables in deciding how to pump water. DC pumps will pump and pressurize. They are higher cost and not as reliable as AC pumps. However, AC pumps have a high current draw when pumping from a deep well, which requires a larger inverter. The best type system is determined by evaluating depth of well, depth to water level, and gallons per minute (gpm) production.

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