Keltic Renewables use Daikin drainback solar thermal panels. These flat panels are generally mounted on a south facing roof.  (or nearest to south as possible)

How do  Daikin drainback solar panels work?

Primarily the fluid only flows through the panels when energy can be stored.

The thermal store is an unpressurised tank containing water. The solar controller is constantly monitoring the temperature in the tank and the solar panels. When the panels can provide a higher temperature than what is in the tank the pumping station will engage and push a quantity of water from the tank up to the solar panels and back down, thus creating a thermal circuit. The pumps will continue to circulate until the solar energy gain has decreased and/or the tank is up to its maximum temperature. When this happens the pumping station stops and the water will flow back from the panels into the tank.

This method has a number of impressive advantage over other flat plate systems:

• There is no issues with extreme high temperatures on hot summer days. Conventional systems should be fitted with a “heat dump” to try and get rid of excess energy so the system does not super heat. This is generally done with a radiator installed in the attic or externally that will radiate the excess heat from the system. If this is not done the antifeeze will boil which can cause it to breakdown and reduce its life expectancy at best. As the Daikin drain back system does not have any water in the panels when there is no gain to the tank the above is never a problem.
• There is no issues with extreme cold temperatures. Conventional systems must contain an antifreeze mixture to prevent freezing in cold temperatures. Obviously when it is freezing outside there is generally no solar gain. Again as the Daikin drain back system does not have any water in the panels when there is no gain to the tank the above is never a problem.
• There is no need for antifreeze in the system.  This means that as we are using just water the heat gain is quicker versus an antifreeze based system. This also means that the cost for maintenance is reduced significantly as there is no need to change the fluid.

The tank will have an input from another energy source. Daikin has provided ready made options for these varying sources:

HPSU: Heat Pump Solar Unit. This comprises of the high efficiency thermal store which has the Daikin altherma internal components housed above it.  This has the advantage that from one system location the heating, hot wtare and solar systems can be controlled. The integration of the heat pump and solar storage together has a huge added benefit in that the energy stored can be used for hot water and heating. In other words if there is a bright day and cool evening the system will use some of the stored energy for heating which keeps the heat pump off for longer.

There is also added option of integrating another heat source into the thermal store e.g. wood burning stove with back boiler to give the ultimate in renewable systems integration.

GCU: Gas combination unit. Daikin have produced a combined gas and solar system that integrates a high efficiency condensing gas boiler, solar drain back panels in a highly efficient thermal store. This store can decide to use excess energy stored for the solar system to heat part of the poperty.

The gas boiler provides:

• up to 28kW of heating output
• gas adapting Lambda-Gx combustion system for optimum fuel usage even for inconsistent gas quality
• Intelligent Storage Management (ISM) means powwr output from 500W.
• Intuitive enrgy regulation

Keltic renewables use Kingspan HP400 for our solar tube installations.  These tubes are at the forefront of solar engineering design and efficiency. The vacuum tubes design means that thermal losses thrrough conduction and convection are removed. This allows the collector to absorb solar energy even when the solar radiation is quiet low (diffuse radiation).

The absorber within the tube contains an absorber plate which is coated with a high efficiency coating that maximises solar radiation absorption while minimises thermal losses.

This absorber plate conducts the heat into the heat pipe which transfers the energy into the fluid circulating through the top of the manifold. The fluid will only circulate when the hot water cylinder will receive a gain from the solar tube collector and the tank is below its maximum temperature setting.

One of the  biggest advantages of the Kingspan HP solar tube systems versus their competitors is the built in over heat protection.

This is an integrated temperature limiter that stops the energy from flowing to the manifold if the temperature exceeds 95 degrees C. This safety device alone results in a much more robust and long lasting system.