There is no single answer. It depends on the requirements (daily hot water needs), the technology to
be used (more sophisticated and efficient technology, like forced circulation systems with evacuated
tube collectors cost more than more simple types), and whether the system is being installed in a
new home or in a pre-existing building.
But the most important thing is that a properly sized solar system will, over time, save much more than it costs. Also, a significant part of the initial cost could be covered by incentives.
The cost of the panels alone depends on the type and size. While significant, the cost of the panels is, nevertheless, only part of the cost of a solar thermal system. Therefore, normally it is best to evaluate the cost of the entire system, including installation (see FAQ #1)
Cost-effectiveness depends on many factors: place of installation, use, exposure, alternative heat source, etc. A solar thermal panel is always cost-effective provided that it is used consistently. Long periods of disuse, usually during the spring and summer, limit its cost-effectiveness. For ever specific case, Pleion can create simulations to assess which system is best for a specific context.
There are various types of solar thermal panels that vary by their mode of operation (direct flow,
tankless, forced circulation) and type of construction (glass surfaces, evacuated tubes, etc.).
Each type serves a purpose and meets different needs and different situations.
However, we can say that the highest performance is generally obtained with evacuated tube collectors, which can maintain high performance even in the coldest season.
During the winter, there are less hours of sunlight, consequently reducing the amount of energy the
sun radiates daily onto the surface of our solar panels. In addition, the operating conditions of the
solar system are made more difficult in the winter due to the low temperatures.
However, there are evacuated tube panels for forced circulation systems that can operate efficiently even in very cold climates, making maximum use of solar radiation, even when it is reduced.
The amount of water provided daily varies and depends on the season and weather conditions. In fact, a solar system is usually not the only source of hot water but is accompanied by a conventional system such as a water heater or heat pump to guarantee the availability of hot water when there is not sufficient sunlight. In generally, a correctly proportioned system provides 50% to 75% of the yearly hot water needs of a house and guarantees almost complete independence during the summer.
Depending on the conditions, where it is installed, the exposure of the panels, and other factors, a good system can provide from 450 to 800 kW/year for every m2 of collection surface, which corresponds to equal savings of useful energy. To translate energy savings into cost savings, we would need to know the associated energy carrier, as well as the efficiency of the conventional heat generator present.
If the system is sized well and correctly installed, you will save far more over time than you spent.
Savings increase significantly in situations in which the associated conventional source is oil or LPG.
It depends on the characteristics and dimensions of the system, which must be sized and chosen based on the user’s needs and requirements. For this reason, PLEION has a wide range of solar kits in its catalogue for various needs and at different prices.
Once again, there are many solutions that vary by dimensions, features, and price.
A solar tankless water heater is simpler and more economical than a forced circulation system.
It is a solution that is especially suitable for mild climates.
Stagnation is the condition in which the solar system stops and starts to boil because it is getting
more energy than it can give to the user or accumulator system.
If stagnation occurs sporadically, it is not a problem. However, if it occurs frequently during the summer, the consequence may be the need for frequent maintenance operations to replace the antifreeze fluids circulating in the panels. For example, this is the case of a system sized to contribute to heating in the winter and that is, consequently, oversized in the summer.
An effective solution is possible when there is an outdoor pool where the excess heat can be discharged while also heating it to a pleasant temperature.
If there is no pool, Pleion has its patented ECLIPSE system which can be applied to all of its evacuated panels. It automatically shades the solar panels when the accumulation tank can no longer receive energy or when the panels exceed a set temperature threshold.
Direct flow panels, such as EGO and EGO PRIME, directly heat the domestic water.
In FREE type tankless panels, the fluid circulating in the solar panels is a mixture of water and glycol which then heats the domestic water.
Forced circulation panels also use a mixture of glycol and water, which transports the solar heat from the panels to a tank, which can contain domestic water or “technical” water (i.e., heating circuit water). In this last case, the heat accumulated can be used for heating rooms (especially when combined with a low temperature radiant panel system) and for producing domestic hot water using another heat exchanger.
Important! Water heated by the panels can reach very high temperatures, especially in the summer. A thermostatic mixing valve is always recommended to protect against scalding.
Solar thermal panels have a collecting surface, called the absorber with selective characteristics (it
is particularly effective in “capturing” and holding solar radiation) under the sun’s rays and
transmits the heat by conduction to a fluid circulating in special circuits that then transfer it to
domestic water or in certain cases to water in the heating circuit.
Direct flow panels such as EGO and EGO PRIME, on the other hand, accumulate domestic water, which is then heated by the sun. When a tap is opened, the hot water contained in the panel runs through the pipes towards the use and is replaced in the panel by cold domestic water, which is then heated.
In all cases, there is a transparent cover and insulating material that reduce the loss of heat from the solar panels, so the maximum energy is transmitted to the fluid with as little as possible dispersed outward.
This depends on the requirement to be served as well as the location. Nevertheless, we can say that the most typical system for hot water for a family of 3-4 people is a 300 litre boiler and 2 panels for a total of 4-5 m2.
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