Solar Systems


The solar thermal systems is a green alternative way of heating and hot water and they can also save you huge amounts of expenses for your home. 

In recent years with the large increase of fuel prices and the establishment of the Regulation of Energy Efficiency in Buildings, the need for energy saving and reduction of primary energy consumption is becoming large. The solar thermal system is a method in which solar energy can be used, for producing hot water and covering part of the heating requirements of buildings. The method is applied for many years in countries of the European Union, but in our country is not widely spread. The majority of solar systems are installed in Germany and Austria, countries with little sunshine and large heating needs. These systems are combined for space heating and water heating. Across the Mediterranean, the numbers of solar radiation favor the use of solar systems throughout the year. Especially in Greece, the climate is ideal for such installations.


How it works

The solar system combined space heating (THCH) and hot water (DHW) is a system that exploits the thermal energy produced by the solar panels. That way the water is heated for use and for the heating system. It consists of

three basic parts: 

the solar collectors and the two hot water storage tanks, one for hot water usage and one for the space heating (Figure 1). These two tanks can be placed one in another (tank into tank), thereby saving space, piping and automation (Figure 2). As the tanks can be placed in every available space of the building, the solar collectors are integrated better for asthetic reasons on the building. Moreover, they can be placed in rooms which are heated, thus reducing heat losses of water. The flat solar panels absorb the difusses sunlight, collecting solar energy even on cloudy days and converting 2/3 of solar radiation into usable energy. Most market brands have glass panels which has high absorbency and does not reflect (antireflex) to ensure maximum heat transfer. The specificity of solar thermal is that they work


 to the heating produced by other fuels rather then 

eliminating it.

 They can be combined with any conventional source of energy (oil burners or gas) or renewable energy sources ( biomass burners) and can be integrated into an existing system, as long as there is space available for the installation of collectors and hot water storage tanks. Also, they can be combined with any heating mean, but it is preferable to use heating means with low temperatures, such as fancoils or underfloor heating. This happens, because the water as heating mean circulates at low temperatures, such that even with little sunshine are easy to be achieved. 

The system ensures to fully meet the demand for domestic hot water and then, if there is excess energy warms the water for space heating. If excess energy is not sufficient, the solar system is bypassed and the space heating is being caried out by the burner, as in conventional heating systems.


How much do the solar thermal systems contribute to the existing heating?

The extend of contribution of the solar thermal system and thus the reducting of fuel needs depends on 

the climatic conditions, altitude, geographic location, the size of installation 

and other factors. Depending on the local climate and the location of the building, the solar panel can capture more or less energy. Depending on the size of the installation, the solar thermal systems cover from very small, up to more than 80% of annual heating needs. Of course, very high coverages are not economically viable solutions. 

The ideal cost - efficiency ratio is to achieve a coverage of about 40-60% of the total heat load 

(DHW and THCH). 


For example the degree of the contribution rate of solar thermal systems: 

A solar heating system is applies and combined with floor heating in Creet, it can almost entirely undertake the thermal loads 

resetting oil use. 

The contribution rate will be significantly lower in the corresponding region of Macedonia, where solar radiation is reduced, but certainly 

will exceed 50%, 

a reduction which is very important for fuel consumption and every day savings. 

Volue and surface installation

To achieve coverage of 40-60% of the thermal load, based on the average sunshine in Greece and the average energy required for heating buildings, the surface of solar collectors should correspond to 

20% of the surface of the heated area, 

while the required 

storage volume is approximately tenfold, 

calculated in liters. For a house that is 


there are required 


flat plate collectors and 1000l. hot water storage tanks( about 200l. for domestic hot water and 800l. for space heating). In the case of roof, the the required surface shoud be 1 1/2 times the surface of the collectors, that is approximately 30sqm., whereas for the installation of storage tanks the required space would be about 3-4sqm.


Advantages of the Solar Thermal Systems

1. Fuel Savings
2. Quick payback
3. Reduced maintenance
4. Reducing pollutants
5. Aesthetic result
6. Does not remove the existing heating system
7. Very small interventions in exiting homes

Another advantage of such a system is that the size (and therefore cost) may be


 to the requirements of the user and can be easily varied. For example, it can be initially placed a system that takes 30% of the load of heating and after some time it can be extended by placing additional solar panels, to cover 60% of the heating. Especially in the case

of installing solar thermal systems on a new building, 

the savings are greater: Because a percentage of the thermal power which is needed is undertaken by the solar heating system, the size of the conventional equipment (boiler and burner) required to be installed is


A part of the money that is invested in the solar systems, is saved from the first day, when the basic equipment is being purchased. For example, it may be preferable to buy a 20KW boiler instead of a 50KW one, if during the initial installation (new bulding) a solar heating system is depoyed with a 60% participation.

Cost  The cost of a system of 20sq.m. as in the above example, is about 10,000 to 12,000 euros. The savings generated can result in about 1.3 tons of oil annually. 10% of the installation cost is deducted from income tax. This means the system based on the current oil price can be amortized in 5 years. The equalization of heating oil and diesel is already applied, so the heating of buildings via solar thermal becomes economically attractive.