Lamps and Electric Appliances
Lamps
Bulbs have an efficiency of only 5%. Halogen lamps are only slightly more efficient. They are, therefore, not suitable for solar systems.
Fluorescent lamps of the tube or compact type are 5 times more efficient and can last 5,000 hours and more. They need a good and efficient electronic ballast for operation. Fluorescent lamps with electronic ballasts cost about 10 € for AC and 20 € for DC (prices as of 2002).
Audio and video devices
Most appliances such as TVs, receivers or video recorders operate on AC. There are a few exceptions including some DC TVs. Color TVs consume more than black & white ones. There are considerable differences between individual brands. TVs should not be operated in stand-by. Controllers and inverters may disturb operation of TVs and radios.
| Power demand of color TVs | |
| Size | Power |
| 17 cm | 20 W |
| 25 cm | 40 W |
| 37 cm | 60 W |
Transistor radios and cassette players are operated by batteries at a voltage below 12 V. Since batteries are expensive, such appliances should also be connected to the solar system through a voltage converter.
For mobile operation, rechargeable NiCad batteries can be applied that are charged with a 12 V NiCad charger.
Water pumps
Some tens of thousands of pumps powered by solar generators are currently in use worldwide. A variety of pumps for low water demand are available on the market. These include single-stage centrifugal pumps for lifting heads < 10m and diaphragm pumps for larger heads, both DC- and AC-operated. They are surfacemounted, floating or submerged pumps. DC pumps with brushes need regular replacements.
The energy requirement (E) for a daily water demand (Q), a pumping head (h, water level to tank inlet or pipe outlet) and a pump efficiency (η = 0.2-0.4, depending on type and pumping head) is
E [kWh] = h [m] x Q [m³/d] / 367 / η
The reliability varies widely. Some pumps only work for a few hundred hours of operation. Poor water quality will cause problems. Simple pumps for typical demands such as 1 m³/h over small heads will cost about 100 - 200 € (prices as of 2002).
Refrigerators
Refrigerators are available for AC and DC. DC refrigerators are more expensive. They cost more than 600 €. The size has only a small effect on the price. Only low-consumption refrigerators of the compressor type are suitable for solar systems. A 100 l high-quality refrigerator without an icebox may consume approximately 300 Wh at 24°C and 450 Wh at 32°C. Ice production, a high demand for cold drinks and a low-efficiency type can easily double or triple this figure. Box types are more efficient. Special types are available for vaccine storage. Starting at low voltage levels (<11.5 V) is a problem for many refrigerators.
