The Self-Sufficiency Handbook. Alan Bridgewater
Currently, there are many questions about PV systems. Are they reliable? How long will they last? Will they do the business in a cool climate? Their use in domestic settings alongside the more trusted solar collectors is growing. All that happens, in effect, is that small PV panels are being used to provide the electricity that sets the various pumps and controls in motion.
An evacuated tube (vacuum) solar water-heating system.
Photovoltaic panels convert sunlight into energy.
An individual photovoltaic cell.
These basic systems are not very sophisticated (in all fairness, PV systems are capable of much more), but they are very neat. As production costs come down, more PV products are coming onto the market.
Passive Indirect Solar Gain and Greenhouse Rock Storage
If you have a conservatory, you will know how quickly it heats up. Conservatories are wonderful places to be in late autumn and early spring. Even on a relatively cold autumn or spring day, they feel comfortable. Yet, in late spring through summer and early autumn, when the sun is beating down, they are usually far too hot. For the most part, when the conservatory is too hot, say in early autumn and late spring, the house can be a bit chilly.
At this point, what most of us do without really giving it much thought is open the doors that link the house to the conservatory so that the heat flows into the house. You could take this basic approach one step further and build vents in the linking wall at floor and ceiling levels—much like the Trombe wall—to create a chimney effect that draws hot air into the house. Alternatively, you could fit an extractor fan in the top vent and send hot air via ductwork to a colder part of the house. All you are doing, in essence, is taking the unwanted hot air and putting it someplace where it is wanted.
The “greenhouse rock storage” option takes this way of thinking one step further and tackles the house-too-cold/conservatory-too-hot scenario. The sun heats up the structure of the conservatory—the walls and floors—so that the air becomes hot and starts to rise. At this point, an extractor fan switches on and draws the hot air out of the conservatory and sends it, via ducts, into an insulated space full of rocks, ideally an underground storage bin. Rock is usually the first choice, simply because it is low in cost and easily obtainable, but you could use any safe, inert material that is slow to heat and equally slow to cool, such as crushed concrete, crushed glass, or granulated metal. Once the heat from the air has been absorbed by the material in the storage bin, the air is circulated back to the conservatory as cool air. During the night, the hot air from the storage bin is sent by natural convection or by fan back to the house.
The rock storage approach is certainly more mechanical than the Trombe wall system, but it is a good option if you have problems with existing structures—meaning that you already have a conservatory that is too hot and a house that is too cold. It cleverly tackles both problems.
Wind Power
It seemed obvious to us. There we were, living in a place where the wind blew so fiercely that every tree and building seemed to be braced against it, so what would be more natural than to build a wind generator? I wrote to a hippie commune in the United States, and they sent me a batch of designs for DIY generators made out of bits and pieces salvaged from old cars.
When the big day came, we mounted the generator in place and connected the wires, and the propeller began to spin. It looked so beautiful. To make a long story short, we had power for a few glorious minutes, and then the lights blew, the cables melted, and the propeller cartwheeled across the field. From then on, we settled for gas lamps and candles.
Now, of course, wind turbines are de rigueur. They are everywhere: rows of giant wind generators on hillsides and mountaintops, medium-sized machines outside gas stations, mini wind turbines alongside highways. The question now is not how to build one, or even where to get one, but what type of wind generator to install. In fact, there are so many options and so much jargon (e.g., utility tie-in, off-grid with battery bank, traditional two-blade) that it can be a bit confusing.
How Does It Work?
We all know about traditional wind turbines. The wind blows, the sails go around, and the turning horizontal pivotal action is converted by means of gears, wheels, and rods to vertical action to turn huge flat stones to grind corn or to turn a pivot that turns a crankshaft that sets a water pump in motion. There are all sorts of complicated head-and-axis design options: canvas sails on a horizontal axis, cylindrical rotors on a vertical axis, vertical rotor blades on a vertical axis, blades like a child’s wind turbine toy on a horizontal axis, and so on.
Most modern, high-tech wind generators have two, three, or five blades or propellers of an airfoil section on a horizontal axis—a bit like an old airplane. Most machines are mounted on a pole or tower and designed in such a way that a mechanical or electronic governor comes into action and applies a brake when the machine reaches a designated top wind speed. The wind blows over the blades, causing them to rotate; the prop spins on a horizontal axis and turns a shaft; the shaft turns inside the generator; the generator converts the turning motion into electricity; and, finally, the resultant electricity is either stored in batteries and converted by means of an inverter to standard AC supply or fed into the public power grid.
Technical Questions and Answers
• How many blades does a wind turbine have? Machines typically have two, three, or five blades, but you can’t choose based on the number of blades. There are so many designs that it’s best for you to do your research and choose what you consider to be a proven machine.
• How much power can a wind turbine produce? Here, too, there are many options. For example, a 600W machine will provide enough electricity to power lighting circuits in a three-bedroom house, while a 2,500W machine will provide enough electricity to power lighting circuits and most appliances in a three-bedroom house.
• How long does a wind turbine last? Much depends upon the machine. One manufacturer claims that its machines have a product life of twenty years.
• How high does the mast have to be? Heights range from 18 feet (5.5 m) for small machines, up to 50 feet (15 m) for large ones.
• Can I mount a wind turbine on my roof? Although the industry pushed for years for bigger hub diameters and increasingly taller masts (based on the research that equates these figures with more power output), there is now a push toward having a lot of small machines rather than one big one. The idea is that every house could have one or more small rooftop machines. That said, there is an anti-rooftop lobby that claims that vibration is always going to be an issue with rooftop designs.
• Can I build my own wind turbine? DIY is a good option if you are an all-around skilled mechanic with a working knowledge of electricity.
• Which is best—a stand-alone or a grid-tie-in machine? It depends on your location. A small machine with batteries might be the only answer for an isolated rural location.
• Are there any grants available? This depends on the country in which you live. There are some grants available in the United States and Australia as well as in Scotland but not too many grants in England and Wales. However, the overall availability of grants is increasing, so research your specific state/province/region.
• What planning issues