Electrical
Fundamentals of Photovoltaic Systems
This article provides an overview of photovoltaic power supplies, using batteries as energy storage devices. Topics covered include typical photovoltaic applications, basic components, system configurations, definitions of common solar electric terms and a list of useful websites.
Solar Electrical System Basics
The most common method of producing electricity using solar energy is to use photovoltaic cells, often called solar cells. Solar cells produce an electrical current when exposed to sunlight. A typical solar cell is composed of a thin wafer consisting of an ultra-thin layer of phosphorus-doped silicon on top of a thicker layer of boron-doped silicon. An electrical field is created near the top surface of the cell where these two materials are in contact, called the P-N junction. When sunlight strikes the surface of a solar cell, this electrical field provides momentum and direction to light-stimulated electrons, resulting in a flow of current when the solar cell is connected to an electrical load.
Home Built Solar System
Written by an author who, in an effort to save costs, decided to make his own photovoltaic panels.
Wiring Solar Panels and Batteries
Only a single-page pamphlet, but it does clearly illustrate the difference between wiring solar panels and batteries in series vs. parallel.
Bicycle Wheel: a Surprising Wind Turbine
Author's description: "Herein we present a discussion and some conclusions about the design of the bicycle wheel converted into an easy-to-assemble convergent wind turbine. The results observed in practice have been so promising that we suggest that this could be an excellent design for a wind turbine."
Build a Savonius Wind Turbine
The Savonius rotor concept did not become popular until recently, probably because of its low efficiency. However, it has the following advantages over other conventional wind turbines:
- Simple and cheap construction,
- Acceptance of wind from any direction, thus eliminating the need for reorientation,
- High starting torque and
- Relatively low operating speed (rpm).
Stirling Engines - a Beginner's Guide
A Stirling engine is a heat engine that is operated by the cyclic compression and expansion of air or other gas between different temperatures, resulting in a net conversion of heat energy to mechanical work. Advantages of a Stirling engine include:
- They can run on virtually any available heat source.
- Emissions can be reduced.
- No valves are needed, and the burner system can be relatively simple.
- They can be built to run quietly and without an air supply.
- They start easily and run more efficiently in cold weather.
How to Maintain NiMH Batteries
NiMH batteries outperform other rechargeable batteries and have higher capacities and less voltage depression. These properties make them ideal for use in high drain devices. Toxic Cadmium is absent in NiMH batteries so they are also more eco-friendly. A fairly technical paper, but with some potentially useful information on what MiMH batteries are (and aren't) suited for, the memory effect, charging and care & maintenance.
1.2 Volt vs. 1.5 Volt Batteries
Author's description: "Very often I’ve read statements like '1.2 volt NiMH cells can’t be used in some equipment designed for 1.5 volt alkaline cells because the voltage is too low.' This is a myth resulting from a number of misconceptions. I’ll explain why it isn’t true."
Vehicle Battery Servicing
Routine vehicle battery servicing covered here includes testing, charging, cleaning, jump starting and adding water.
Water Heating
Solar Hot Water Simplified
Even in the cloudiest climates, the sun can provide 50 to 60 percent of a household’s annual water heating, and in sunnier places, 80 percent or more. This 10-page, well-illustrated, extract from Home Power magazine describes the 5 main types of solar hot water systems: batch, thermosyphon, open-loop direct, pressurized glycol and closed-loop drain back.
The Integral Passive Solar Water Heater Book
Solar systems for heating water can be divided into two classes: passive and active. The essential difference is that passive systems need no auxiliary power to operate while active systems are dependent on externally driven fans or pumps. This 104-page book deals primarily with passive systems which combine the collection and storage into one unit. Is there nothing new 'under the sun'? The first illustration in this book, showing several houses with solar water heaters on their roofs, was taken in Los Angeles in 1900!
A Simple Solar Hot Water Heater for the Tropics
This 8-page booklet shows, with numerous colour photographs, a thermosyphon solar hot water system designed originally for a fairly remote area of Costa Rica. As a result, the unit had to be simple and to rely on rugged and readily available materials, few tools and limited plumbing skills.
A Thermosyphon Hot Water System in the Fiji Islands
This 6-page booklet includes a detailed list of materials used and several colour photographs. Total cost (the year is not specified) was US$250.
Design & Installation of Solar Water Heater Applications in Pakistan
This book is actually a training manual produced by the Renewable & Alternative Energies Association of Pakistan. Very comprehensive.