Flate Plate vs Evacuated Tube Solar Hot Water Collectors
The solar heating collector's job is simple – it is in the sun, absorbs the heat, and transfers it to where you need it.
To do this efficiently, solar heating collectors need to absorb – and retain – a large volume of sunlight every day.
Cost is typically the primary consideration. Collector for collector, evacuated is a lot cheaper than flat panel collectors. However when comparing price one should consider cost per BTU capacity is also less which make the year round performance is more effective and cheaper.
In cool climates, evacuated tube collectors will have a lower cost per BTU.
Shipping costs can be more with flat panels than with evacuated tubes as well, especially when ordering a package system.
Evacuated tubes are modular, and can be shipped vertically, maximizing the usable space on a pallet. It always takes 2-3 people
to install a flat panel collector where as a evacuated tube collector can be installed by one person.
Location is also an important consideration to cost. In some regions, it make take more or less of one type of collector vs the other
to heat the same amount of water. For example in a cool climate, you could need 2 or 3 flat panel collectors to produce the same heat
as 1 evacuated tube collector. In really cold (under 50F) weather, flat panel collectors collect little or no heat.
Generally, evacuated tubes perform better in colder and/or cloudier conditions than their flat panel counterparts. This is because of
the vacuum in the glass tube, which allows tube collectors to retain a high percentage of collected heat. They work well in freezing
conditions where flat panels will not work.
However, in areas where heavy snowfall can be an issue, evacuated tube collectors will not leak much heat from the collector, and
therefore will not melt snow and heavy frost as quickly as a flat panel collectors. Evacuated tube collectors in cold climates can be
installed at a higher angle to better face the sun, and this, along with a separation between the tubes, allows snow to slide off more easily.
A flat panel collector, on the other hand, will collect some heat through the reflected sunlight off snow & ice, rising above freezing and
therefore melt the snow or heavy frost much quicker, even though it may not be able to produce any hot water in cold conditions.
For customers needing really hot water, for example, laundromats, car wash, manufacturing process etc. note that flat panel collectors
will not reliably perform above 130-140F. Evacuated tube collectors can produce hot water up to 200F.
Due to the self-tracking design of evacuated tube collectors, they collect heat fairly evenly throughout the day starting within minutes
of sunrise. Flat panel collectors must collect nearly all of their heat in the middle part of the day.
Flat panels are typically designed with an unsealed enclosure. This can make them prone to condensation over time, which can result in corrosion.
However, this largely does not impact the actual performance of a flat panel unless corrosion results, and is mainly a cosmetic downfall.
Flat panel collectors – if damaged, will continue to function, and can at times be repaired. Other times, the entire flat panel must be replaced.
Evacuated tubes, on the other hand, are sealed with a vacuum. This gives them their high heat retention properties, however, without this vacuum
an evacuated tube collector performs very poorly. If a tube were to lose it's vacuum, it is generally very easy to correct, and can be
done easily by simply replacing the tube.
Evacuated tubes are typically less sensitive to sun angle and orientation than their flat panel counterparts. Their circular design allows sunlight
to pass at an optimal angle throughout the day – from morning to night.
Flat panel collectors are more sensitive to sun angle, and may require the use of racking systems, or other elevations to maximize their production.
When considering which technology to use, consult your local dealer, or contact us directly. We will be glad to look at both technologies and
see which is the best fit for your specific application.
Flat panel collectors are best for users in southern climates or for northern seasonal homes only used during the summer. Evacuated tube collectors
are best for areas where winter temperatures frequently drop in the 40F range or below. Customers needing hot water at higher temperatures
in all climates should consider evacuated tube collectors.