back due to undulating terrain. At these locations, low power transmitters (LPT) are installed to receive and retransmit the signal for local population. Pico PV systems The smallest, often portable photovoltaic systems are called pico solar PV systems, or pico solar. They mostly combine a rechargeable battery and charge controller, with a very small PV panel. The panel's nominal capacity is just a few watt-peak (1–10 Wp) and its area less than in size. A large range of different applications can be solar powered such as music players, fans, portable lamps, security lights, solar lighting kits, solar lanterns and street light (see below), phone chargers, radios, or even small, seven-inch LCD televisions, that run on less than ten watts. As it is the case for power generation from pico hydro, pico PV systems are useful in small, rural communities that require only a small amount of electricity. Since the efficiency of many appliances have improved considerably, in particular due to the usage of LED lights and efficient rechargeable batteries, pico solar has become an affordable alternative, especially in the developing world. The metric prefix pico- stands for a trillionth to indicate the smallness of the system's electric power. Do it yourself community With a growing interest in environmentally friendly green energy, hobbyists in the DIY-community have endeavored to build their own solar PV systems from kits or partly DIY. Usually, the DIY-community uses inexpensive or high efficiency systems (such as those with solar tracking) to generate their own power. As a result, the DIY-systems often end up cheaper than their commercial counterparts. Often the system is also connected to the regular power grid, using net metering instead of a battery for backup. These systems usually generate power amount of ≈2 kW or less. Through the internet, the community is now able to obtain plans to (partly) construct the system and there is a growing trend toward building them for domestic requirements. Gallery of standalone systems References Applications of photovoltaics