Energy exchange traded funds continue to strengthen as a global energy crunch supports strong demand heading into the winter months. On Friday, the ALPS Alerian MLP ETF (NYSEArca: AMLP) increased 0.3%, and the JPMorgan Alerian MLP Index ETN (NYSEArca: AMJ) advanced 0.3%.The more widely observed Energy Select Sector SPDR Fund (NYSEArca: XLE) was 0.6% higher.