The PV systems we design sell themselves. The present owners are happily committed to their alternative sources of energy. This web site proposes several system designs. The logic is that you will not make the same expensive mistakes others have. A wrong guess or a little misinformation can result in a wrong choice or poor design. If you purchase the wrong piece of equipment you forever live with poor performance, or suffer the economic loss incurred in a trade-in. The solution is to profit from the previous mistakes of others.

· Why Photovoltaics?

There are many reasons why a remote site home or camp should be powered by photovoltaic electricity. A PV system is superior to a wind system in home applications. There is less maintenance, and what there is does not require an owner to choose between climbing a tower in an ice storm or watching his or her investment go down the drain. The sun shines more frequently than the wind blows. Long periods of no power in a wind system require a large and expensive battery bank. A PV system is modular. It can be purchased first as a beginning system and then expanded to a medium or large system. If you cannot afford a large PV system immediately, buy a small system and add to it as your cash flow permits.

· How a PV system Works.

The simple PV system contains a PV module, a battery, and a load. The module transforms light energy into low voltage DC electricity that is stored in the battery until needed. The load uses the energy stored in the battery and the PV module then recharges the battery. The PV module could directly power the load. A 50 watt PV panel could power a 50 watt bulb, but only in the daytime, and only on a sunny day. The battery can power the load at a time when the PV module is not producing electricity. The inverter is between the battery bank and the load, this inverter converts DC to AC.

·Array Mounting

Modules may be mounted on a pole, a ground support, a side support, a side wall of a building, or on a roof. The first consideration obviously is day long access to unobstructed sunlight; but also, it is important to consider wire length to batteries and just plain where they look good. Anytime a modules orientation is exactly perpendicular to the sunlight it receives the greatest possible insolation and puts out its highest wattage. Ideally, a mount that can change directions so that it will always be perpendicular to the sun will have the greatest output. In theory, this would mean the array would follow the sun from east to west and also tilt upward at the same time as the sun rises higher in the sky at noon.

·Charge Controllers

The charge controller in a PV system is a voltage regulation device which matches and protects both the PV array and the battery bank. If the modules were allowed to constantly charge a battery bank, then in times of low load, they would be capable of supplying more wattage to the batteries than the batteries could hold. Simply, more electrical energy would be going into the battery bank than would be drawn out. A deep cycling lead acid battery, which is normally used, would reach a state of overcharge. In a lesser case, the batteries would boil off too much water and require extra maintenance. In a service case, the batteries would be damaged. A controllers job is to sense the level of charge of the battery bank by measuring its voltage. When the battery reaches a desired high voltage, all or part of the PV current must then be channeled away from the battery. When only part of the current is shunted, the remainder functions as a maintenance trickle charging current to keep the batteries at 100% charge.

·Batteries

For simplification we will concentrate on lead anatomy, lead acid, deep cycling batteries. At the current level of battery production and technology, this is the one good choice for remote site home installation. These batteries are, of course, not ideal for PV use, but the economy of scale dictates a price that compensates for their less than perfect design. There are superior designs of batteries such as the “Absolyte” suspended electrolyte batteries. The life is longer, the temperature range of operation is better, and the maintenance is negligible. However, the price is prohibitive even after factoring in the increase life span. The battery industry should develop a battery specifically for home PV systems. Until your first battery bank replacement, use the deep cycle battery.

·Inverters

The inverter is potentially the weakest link in the remote site home PV system. It is a complicated. Expensive piece of electronic technology, which to most owners comes in the shape of a mysterious large black box. Inverters for a PV homes have come a long way in the last seven years. The best inverters are very reliable. They will require less warranty service than a generator. The majority of them will never do anything but run. Most PV homes will either immediately or in a short while need an inverter.