Solar technology explained

Standard-System-SchematicFor those who do not fully understand the concept and operation of a solar thermal (hot water) system, Comfort Solutions Ireland have prepared an explanation in simple language, of a standard solar system, from the sun hitting the solar panels or tubes on the roof to the hot water in your taps. We hope this gives you a good understanding of the basics of our solar thermal systems. If at any point, you have any questions or would like a site survey or quotation for your home or business, please contact us.

 

Please note: It is extremely important that your solar hot water system is installed by competent and experienced installers. Solar hot water systems handle exceptionally high temperatures which can be highly dangerous if not correctly managed. Ensure your installer is fully qualifed in solar thermal systems and can prove accreditation.

 

Collector

DSC00135From the diagram we can see that a solar water heating system is really very simple. On the roof of the house there is a solar collector often called "solar panels". These are usually a dark blue colour (best at absorbing heat), with a network of pipes within containing water, and a glass cover on top. The panel absorbs the sun's heat, which is then absorbed by the water. The glass cover allows the sun's rays through, but traps a layer of air to insulate the panel from the atmosphere outside. This means that the panel can produce hot water even in cold air temperatures, so long as the sun is shining. More elaborate panels take the form of glass evacuated tubes with metal pipes inside, and these tend to be more efficient than flat panels especially in low-light or cloudy conditions ie. they do not require direct sunlight to work effectively. Good quality solar panels and tubes will last at least 25 years with minimal maintenance.


Pump

The water in the panel is moved through a closed loop of pipework by a water pump. The pump uses very little power, generally around 25 to 50 Watts of electricity. Although these systems do use electrical energy, the energy harnessed from the sun far exceeds consumption. More expensive systems might use a photovoltaic panel (Solar PV) to generate electricity from the sun, which is then used to run the pump.


Expansion Vessel

As the water in the system heats up and cools down, it expands and contracts. In order to keep the pressure in the system fairly constant, an expansion vessel is fitted which compensates for changes in water volume due to temperature. The pressure used is only around 2 BAR, which is not high enough to worry about.


Cylinder

DSC00068

The hot water generated by the solar system is generally transferred to a storage place in the form of a hot water cylinder. This is done using a heat transfer coil, which usually takes the form of a flat coil in the bottom of the cylinder. This is the coldest part of the tank, so the system can transfer heat into the tank even when sunshine is limited. In summer, this allows the solar system to heat the full cylinder of water, meaning that you shouldn’t need any oil, gas or electricity for water heating. In winter, your solar system will still work, although to a lesser degree. You will need your oil, gas or electricity to bring your cylinder up to full temperature, but they will have less work to do as the water will have been pre-heated somewhat by the solar heating system. Modern hot water tanks with these special solar heating coils are very efficient at transferring heat into the water, and only a little more expensive than a standard tank. They are also highly insulated, meaning that any energy gained is not easily lost but effectively stored until needed. Comfort Solutions Ireland use high quality stainless steel cylinders which carry a 25 year warranty.


Controller

The whole system is run by an electronic controller. This uses temperature sensors to work out when the panel is hotter than the water in the tank, so it knows when to switch the pump on and off. The controller is a very intelligent piece of technology and can also protect your system against frost, stagnation and other potential problems.


Hot water

Solar_hot_water_tap

It is important to realise that the water that comes out of your hot water tap has not been through the solar panel, it remains completely separate. This is partly because a pressurized, closed system is more efficient at transferring heat, and partly because the closed system must contain antifreeze to protect the panel from damage in cold temperatures. Using the same water through the system also protects system components against lime-scale due to minerals in water. You might be worried about the coil becoming damaged and leaking antifreeze into the hot water tank. Fortunately, this is not as big a concern as you might think. Solar water heating systems use a special kind of antifreeze called Propylene Glycol, which is a common non-toxic food additive. (Older systems used Ethylene Glycol, which is toxic when consumed, though minimally toxic through skin contact. The antidote is alcohol!) It also contains a lurid dye, usually luminous pink, green or yellow, which will alert you in the unlikely event of a leak. It may contain a special bitter chemical to stop you drinking it, although you shouldn't really be drinking from the hot tap anyway!


Conclusions

Solar-thermal water heating systems are becoming more and more cost effective due to recent rises in energy prices. Depending on the levels of sunshine where you live, and how much hot water you use, the system will generally pay for itself within 10 years, and sometimes less than 5. In addition, houses with eco-friendly features tend to stand out in the housing market and sell more quickly. You should notice an immediate fall in your fuel bills, particularly in summer. Costs may be offset even further if you are eligible for a government grant (See Grants section), which are still available to houses built before 2006. If you are looking for a way to reduce your carbon footprint and save money in the long term, solar thermal water heating could be perfect for your needs! 

Download our Solar Thermal leaflet below

pdfComfort_Solutions_Solar_Hot_Water_Brochure_JULY_2012.pdf

For more information, updates on our latest technologies, or to have a solar system tailored for your home or business, contact us today.

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