Guten tag
first I would like to apologize for posting here in english. As most of you may already know solar energy is now very quickly developing in Spain; I have been in the bussiness for two years and I am know thinking about using heat pipe collectors for some applications, but they are  not comonly used in Spain and I have a lack of information (suppliers of coure only tell what thay think they should tell). My problem is that I have been told (by only one person) that heat pipes lose efficiency over time because the fluid they have inside may degrade. I haven't read about this phenomena in solar energy bibliography. I know in Germany you have been using these collector for years, so you may have a good retounr of experiencie.
I would be very thankfull if some of you cold help me. Maybe this subject has already been treated in this forum but I don't speak german... if so, please tell me and I will find someone to translate.