Solar Thermal Drain Back Systems
Overheating and air pockets can lead to costly and potentially damaging malfunctions in solar thermal systems. Overheated glycol fluid in the collector and pipework can quickly render systems completely inoperable and, in worst case scenarios, can require a complete system replacement.
Adveco Drain Back counters these problems, as well as issues relating to high system pressure, dirty pumps and non-return valves, plus corrosion from acidic heat transfer medium all resulting from very high temperatures seen in modern solar thermal systems.
A simple gravity-driven process within the compact module Drain Back module ensures trouble free operation and system longevity for improved returns on investment in renewables for water heating in commercial buildings.
- Gravity driven drainback, no large storage tank needed
- Automatically drains fluid if power is cut
- Fluid replacement needed every eight years at most
- Compatible with Adveco flat plate solar collectors
Drain Back Module Design: Features & Key Technologies
- Intrinsically safe, issue-free system operation
- Proven overheat protection concept
- Extendable and appropriate for solar thermal refurbishment
- Automatically drains fluid if power is cut without the need for working component
- Extends low-maintenance operational lifespan with fluid refresh required every eight years at most
- Reduces required pump capacity and energy use of pump station to a minimum
- Designed for single-row roof-mounted and console systems. Fully compatible with Adveco Flat Plate Solar Thermal Collectors
- Suitable for retrofit projects without further hydraulic adjustments
- High-quality stainless steel/aluminium compact modular design
- Supports high pressure (6 Bar)
Adveco Drainback Systems – For Long-lasting, Low-Maintenance Renewables
As with any technology, issues can arise if a commercial system is poorly designed or maintained. In terms of solar thermal systems, the results can vary from frustrating to catastrophic and can prove to be extremely costly.
By far the greater concern is the stagnation of the solar fluid as a result of high-temperature build-up within the collectors when a system is not operating. solar thermal collectors or panels utilise the sun’s energy to heat a water & glycol mix in the panel. This solar fluid is then pumped to a heat exchanger inside a water cylinder.
If a solar thermal system has no overheat protection the fluid can change to the consistency of tar. The ‘tar’ can rapidly develop as a film, and within a multiple collector system, it is likely that some of these will become blocked and will not be able to be cleared out causing permanent damage and resulting in very high repair costs. We have seen this issue develop in systems a matter of weeks after initial installation!
Overheat protection is therefore vitally important and will typically require the addition of a large solar storage or buffer vessel to dump unwanted heat to stop the system from stagnating. Together with the heat dump system starting in the middle of the day due to a short period of low demand, the Solar Thermal application could be extremely inefficient.
At Adveco, we are proponents of systems that deploy drain back, which as the name implies drains the solar fluid from the collector to a reservoir when not in use, allowing for a system to be safely off.
A drain back vessel located in the plant room is one option, that will also allow for pipework fluid, but will require greater head pumps.
With Adveco’s drain back module, installed on the flat plate collector commercial buildings with high demands can deploy a large number of collectors with a small tank and still provide high-temperature water with the knowledge that in times of low use high-temperature build-up in collectors is impossible. This ensures the system remains protected.
As there is no requirement for the installation of large solar storage, this approach is far more cost-effective and more efficient as there is no call to dump unused heat.
Example Adveco Drain Back & Flat Plate Collector Installation
Specifications
Drain Back 1190 – 1.190m module, sized for a collector field up to 5m², 7 litre volume, 6kg empty weight.
Drain Back 2090 – 2.090m module, sized for a collector field up to 10m², 13 litre volume, 10kg empty weight.
- Drain Back 1190
- Length 1.190 m
- Collector field size 5m²
- Volume 7 litres
- Empty weight 6 kg
- Drain Back 2090
- Length 2.090 m
- Collector field size 10m²
- Volume 13 litres
- Empty Weight 10 kg
Is a drainback system a tank, a reservoir, or something else?
Drainback, or drain back, solar systems always need somewhere for the solar fluid to go when the panels aren’t being used, whether that’s called a reservoir, a storage tank, or a module. The traditional approach is a drain back vessel sited in the plant room, essentially a storage tank that holds the fluid and the system’s pipework volume, but this needs a bigger pump to lift the fluid back up to the collectors each time the system starts.
Adveco’s drainback module takes a different approach, sitting close to the collector itself rather than as a separate plant room tank. That keeps the reservoir small, a 7 or 13 litre module rather than a full storage vessel, while still giving high demand commercial buildings the ability to run a large number of collectors off a compact drainback unit instead of a large solar storage tank.
Why solar thermal systems need overheat protection
Solar collectors heat a water and glycol mix that’s pumped through to a heat exchanger inside a cylinder. Without overheat protection, a period of low demand lets that fluid sit in the collector and heat up unchecked, and severely overheated glycol can degrade to a tar like consistency within weeks of installation. Once that happens in a multi collector array, some panels typically block permanently, and repair usually means a costly system replacement rather than a simple fix.
The conventional fix is a large solar storage or buffer tank to dump the excess heat, but that adds cost and still risks kicking in during a short demand dip in the middle of the day, wasting the heat the system just generated. Drainback avoids that dump entirely, since there’s no built up heat to get rid of if the fluid isn’t sitting in the collector in the first place.
Which drainback module do I need?
Sizing runs off your collector field area. Drain Back 1190 covers collector fields up to 5m², matching two or three Adveco flat plate collectors on a typical installation. Drain Back 2090 covers fields up to 10m², suited to larger arrays. For non-standard or larger collector fields beyond these two sizes, Adveco can advise on a suitable configuration rather than working strictly off the two standard modules.
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