What are these cylinders on top of solar cells? (Portugal)

D107

Whenever I travel I always try to learn about how different countries approach heating, AC, recycling, etc. I can't figure out what the cylinders are on the solar cells--too big to be AC-DC converters I'd guess.

kcopp

Those are "batch Feed" solar panel set ups.
They are for solar Thermal (hot water) panels.
That is the tank vs. having it below.
Pretty popular in temperate climates vs. northern north America.

hot_rod

Sometimes called integrated collectors. You see them with evac tube style collectors also.

Very portable, and folks often take they along when they move from flat to flat. See them for sale at hardware stores a DIYer kits.

A warm climate system as there is no freeze protection, cold water up, hot water down, thermosiphon principle.

D107

Thanks. So this is for DHW, water is in those tanks; that town's avg air temp in the coldest month of the year (Jan) is 49ºF, lowest temp 40º. I guess that's about the same or higher than the average incoming water temp in the Northeast here. And in summer, even better.

So in NE, no tanks on roof, just a water pipe running down I assume. If I could be assured that the panel installation wouldn't eventually cause leaks in my roof, this might be a good alternative to the photovoltaic panels for electric. Good to integrate with to a reverse indirect for DHW/buffer. And no need to worry about future utility policy for net metering; the hot water savings will be as real as electric as long as I'm not generating more hot water than I can use.

I notice the panels are angled differently than the roof contour.

hot_rod

Solarhart out of Australia made a push in the US market with a batch type system. They had glycol antifreeze in the collector and a HX in the tank. But you still had a tank of hot water outside The look of a tank on the roof wasn't all that desirable either. They never got much traction in the NA market.

Most every city in the US you can get a 50% SF, solar fraction. meaning 50% of your DHW from the sun with 2 or 3 collectors.

Not really a good match for heating as the winter sky doesn't have a lot to offer for energy, and the ambient temperature outside steals away to much energy from the collector in the winter months. In the sunny SW installers look for a 30% solar fraction for heating loads. It ends up being a lot of collectors. Energy in the US is very inexpensive compared to the rest of the world.

Germany and other European countries embrace thermal solar to lessen their dependance on Russian oil supply. Russia has been know to shut off the pipe lines in the winter, playing politics.

Collector typically mount at the same slope as the latitude where they are installed for best year around performance.

D107

Well here in the north, with only two seniors averaging $13/mo gas hot water costs ($156/yr) saving half of that for the 50% SF, the ROI would seem to be several lifetimes. (HW therm usage with direct hwh about 103 Therms a year.)

hot_rod

David107 said:

Well here in the north, with only two seniors averaging $13/mo gas hot water costs ($156/yr) saving half of that for the 50% SF, the ROI would seem to be several lifetimes. (HW therm usage with direct hwh about 103 Therms a year.)

Yep