Solar collectors are fuelled by solar radiation. Therefore they allow us to use cheap and renewable solar energy. But how does solar collector work? Radiation reaches the absorber covered with a special absorbing layer. Absorber transforms the energy into heat and transmits it to heating agent by copper pipes. Then the heat is transported further, used for heating of water, air conditioning or the building’s heating systems.
In terms of heating, office locations are different from buildings used for housing or industrial purposes. In this specific case, the energy is used primarily for general heating and, to the lesser extent, for heating of water – unless there’s a restaurant in the building and it requires huge supply for this commodity. The main factors taken into account when considering the solutions for heating of water are: average daily use of water per employee (in an office building it’s usually 10 l per person), the number of users (which is of highest importance for the investment’s profitability), the number of working days in year (usually it’s 295 days) and maintenance costs (in case of solar collectors one has to take into account the change of glycol every 5 or 6 years and possible change of magnesium anode in the buffer) – explains Karol Michałowski, the owner of EcoDay. What is also important is having the durability of the solar collectors written down on paper. In the case of high quality, polish solar collectors it’s 25 years. The power of the collectors has to be adjusted properly. However, more important than the power of the device is its efficiency, i.e. how much energy it can generate. Other elements of the system and their proper functioning also influence the general efficiency of the device. The higher the efficiency, the more energy is transmitted into the system.
Heat and energy without the sun
There are two types of solar collectors that can be used in office buildings: photovoltaic link collectors, which can be used for production of electricity and liquid collectors, which by transforming the solar energy into heat, can be used for heating of water, general heating and air conditioning.
In the western countries, over a half of solar installations is used both for heating of water and interior. Bigger solar installations are much more efficient than the ones used on family houses (the difference may reach up to 30%). It influences the profitability of the investment and reduces the time for it to pay off. One will immediately feel the difference as the expenditures connected with primary source of heating will decrease.
Usually the additional energy from the solar installation covers part of the buildings heat supply. Because of the fact that the amount of heat gathered by the collectors varies in relation to the season, the solar collectors can only be the additional source of heating – explains Krzysztof Gnyra, consultant in Viessmann. In office buildings, liquid collectors can gather energy to support the water heating systems, for building’s general heating or to support the air conditioning. The investment will be more profitable when the costs of the primary heating systems are high. Taking into account our geographical position this investment should be an efficient supporting installation. The solar collectors are integrated with the primary heating systems so that as much energy as possible can come from the sun and the boiler could use less fuel. They will never replace the primary heating, but they have to be taken into account as a part of the general system, upgrading its efficiency.
In the case of office locations air conditioning of the interior is very important. It’s connected with accumulation of people and utilities generating heat inside the structure. The heat grows also as a result of many glassed surfaces. Solar collectors can also take care of this problem as the cooling devices can work on solar energy. Only void solars can be used for air conditioning, due to high temperatures created by absorption cooling devices. First thing to do is to make sure how much cool needs to be provided inside the building and, basing on that value, power and type of cooling device has to be chosen. The most common type of air conditioning is the absorption cooling system.