Renewable Power
for a
Wireless Network
at Tech 2 – Grizedale

Following on from the 3-day workshop on renewable energy, after relocating to Grizedale attempts were made to develop a low-power renewable energy system. The objective was to provide electricity to support a small computer to maintain the service of a wireless network.

The power source chosen was a wind turbine (small photovoltaic - PV - modules were also used as part of the demonstration). The turbine provides power to charge a large 12 volt battery. The wind turbine was erected on the green at Grizedale Centre (not an ideal location, but good for the ourposes of demonstration). Various locations were then tried for locating the main antenna for the wireless network.

The tower and wind turbine are assembled on the ground. The base of the tower is hinged to a plate that is fixed to the ground. The whole tower and turbine can then be winched to a vertical position using a gin pole to support the weight of the tower as it rises up.

Erecting the wind generator

A schematic of the power system

The power system stores energy is a large battery. The system works at 12 volts - although higher voltages are commonly used with small wind turbines. The battery is charged via a charge controller (left, top). This ensures that the battery is efficiently managed. If the battery could be overcharged it diverts the power to protect the battery - turning it to heat in a 'dump load'. The charge controller also manages the power from any photovoltaic modules running in tandem with the generator.

The charge controller and battery were housed in a small wooden box at the foot of the wind turbine tower (left, second/third).

The battery discharges to an inverter (left, bottom). This is a device that takes the 12 volt direct current (DC) and turns it into the 230 volts alternating current (AC) used in the mains supply. The inverter is wired to a plug strip to allow equipment to be plugged into the system and powered. The inverter can supply up to 400 watts of power - around 1.7 amps at mains voltage.

For safety, the connections to the battery, and to the inverter, are fused with small sections of lighter gauge wire. At full power, the inverter will draw around 40 amps from the battery. The cables connecting the battery and inverter can carry a far higher current. The short sections of wire should fuse at around 50 amps - far safer than discharging more than 100 amps from the battery should a short circuit or other fault occur.

It turns!