Holwell Farm within the Dartmoor National Park, in Devon, UK, is using a 20-kW Remote Area Power Supply (RAPS) system incorporating a wind turbine system, 20-kWh battery storage and a backup 25-kW diesel generator (UNEP, 2003). The system provides electricity for agricultural activities, bed and breakfast tourist accommodation and other domestic uses. The farm is located 2.5 km from the nearest electricity grid. The three-blade wind turbine has a rotor diameter of 8.8 m, a hub height of 24.4 m and is mounted on a lattice tower. An automated control system ensures that AC power is always available and switches to the diesel generator when batteries are 80% discharged or when electrical demands are high.