More and more owners of remote homes are realising the benefits of clean, quiet and efficient battery charging using photovoltaics. Chandlerys, caravan shops and car accessory shops all sell a range of 12Vdc equipment suitable for use in remote homes. Beco also stock a range of inexpensive inverters which provide AC power. The modules are BP380 laminates, linked to a Studer Inverter, a Morningstar 'Sunsaver' regulator and a bank of Exide 12-500X batteries.

Solar systems for remote homes may be divided into two types -

Low Voltage DC
The simplest system to install, comprising a solar module, 12v battery and a charge regulator. The battery stores the energy from the solar array during the day. The stored energy is then used to power low voltage lights, radios, CD players, etc at any time, day or night.This type of system is ideal for use in garden sheds, garden lighting, greenhouses, holiday chalets, caravans and boats.

Low Voltage DC with AC
The same equipment is used in a DC/AC system as in a DC only solar system but with the addition of an inverter. The inverter draws the stored energy from the battery converting it to 240V AC to run televisions, microwave ovens, low energy light bulbs, etc up to the maximum power of the inverter. Inverters are readily available with continuous power outputs from 200 to 3500 watts. This type of system would normally be used in remote homes where mains power is not available from the national grid but can be installed anywhere that AC power is needed.

Note: With both these systems it is essential that the solar array output is matched to the expected total daily load. When sizing a system the three L’s (Load, Location, Losses) must be taken into consideration so that a reliable system will be installed.

The following notes are designed to assist potential domestic users and should be read in conjunction with the product information sheets on charge controllers & inverters as well as the solar electric design guide.

Solar modules are relatively expensive to purchase and install, however, major advantages are -

• The energy they produce is free
• Maintenance is almost zero
• No pollution
• No noise
• Warranties of ten to thirty years
• Simple to expand the system

Many luxury items that have become almost essential to some people are very power hungry and require large solar systems. Always buy low energy equipment as these often use 50% less power (e.g. light bulbs) and purchase energy efficient appliances that you require to run continuously – eg your refrigerator. The initial higher cost will be more than offset by the savings made on the solar system. Cookers and heaters use very large amounts of electric power and alternative fuel versions would be more economic. The attached diagram shows the componant parts of a typical domestic solar power system.

Array: A number of solar modules connected together and mounted on frames.

Controller: In its simplest form the controller prevents the batteries from being overcharged. More sophisticated controllers also prevent damage to the battery by disconnecting the load when the battery voltage drops to a preset level.

Battery: Stores energy from the array during the day so that electric power is available day and night.

Inverter: Converts the 24volt DC from the battery to 230volt AC.

Each module in the system will be sized to support your total power requirement.The first stage in designing a solar power system is evaluating what your minimum power requirements are. Start by listing all the mains powered electrical equipment that you have or anticipate having. Against each item note the wattage or current consumption and the average daily or weekly use, in hours and minutes, of each appliance.

For example:

Located in Spain this load would require a 1700watt solar array. This assumes that the house will be occupied for 12 months of the year. Summer only use would reduce the array size by about half.