Analisis pengaruh perbedaan intensitas pencahayaan dan konsentrasi Fluida kerja AL2O3-Air terhadap performa Evacuated Tube Heat Pipe Solar Collector pada sudut kemiringan 45 derajat = Analysis on effect of difference lighting intensities and AL2O3-Water working Fluid concentrations on the performance of Evacuated Tube Heat Pipe Solar Collector at inclination angle of 45 degrees