wind energy green renewable sweden sverige stockholm göteborg gothenburg malmö linköping norrköping norrland gotland öland förnybar vindenegi vindturbin wind turbine small scale liten cylindrical propeller cylindrisk low cost lågkostnad naturvänlig environmental friendly no-noise no-harm to birds animals children surrounding facilities no-risk ingen risk på fåglar miljövänlig durable sustainable generate electricity power everywhere always anytime low wind speed high wind speed storm weather condition continuous high kwh per square meter